Is there really a particular reason that everybody uses the Radio Shack SPL meter or can I use another SPL meter? I just ask because there are several i've looked at on ebay at good prices, but they weren't Radio Shack. Just didn't know if there was something special about it in particular. Thanks.

Nothing special about the meter, it's just easy to find and priced nicely. BTW, get an analog model if you can, it makes calibration much easier.

Nothing special about the meter, it's just easy to find and priced nicely. BTW, get an analog model if you can, it makes calibration much easier.

Disagree. The analog models are notoriously inaccurate at lower and upper frequencies, as much as 20dB in the very low end. The digital model is accurate within 1dB across the spectrum. You can use the analog models, but you should also get one of the adjustment charts out there for which ever model you get.

Disagree. The analog models are notoriously inaccurate at lower and upper frequencies, as much as 20dB in the very low end. The digital model is accurate within 1dB across the spectrum. You can use the analog models, but you should also get one of the adjustment charts out there for which ever model you get.
I don't know where you heard that, but it's not true. They are both equally accurate (or inaccurate; however you want to look at it). Most people prefer to use the analog model.

I was also going to ask...i'm not a hardcore audiophile...so this surround system I just installed will be up for a long time. Is there any reason to actually BUY an SPL meter if I'm just going to use it once? Or is this something you need to use more than once?

I ask because I have a friend that said he'll let me borrow his...but theres a used on on ebay for $30.00. Just trying to keep the expenses down!

I was also going to ask...i'm not a hardcore audiophile...so this surround system I just installed will be up for a long time. Is there any reason to actually BUY an SPL meter if I'm just going to use it once? Or is this something you need to use more than once?

I ask because I have a friend that said he'll let me borrow his...but theres a used on on ebay for $30.00. Just trying to keep the expenses down!

Yes, I use mine frequently just to double check, and as hardware in the system changes. Plus, I think you can get a new one from RS for about the same price as what you saw on ebay.

I don't know where you heard that, but it's not true. They are both equally accurate (or inaccurate; however you want to look at it). Most people prefer to use the analog model.

Not only heard it, but measured it myself since I have both. The digital model is within 1dB from 20Hz - 20KHz. The analog falls off considerably below 50Hz and above 10KHz. These measurements were confirmed using a calibrated EMC8000 and frequency response software.

Perhaps there's a newer analog model that fixes the older inaccuracies, but I've not seen one.

Not only heard it, but measured it myself since I have both. The digital model is within 1dB from 20Hz - 20KHz. The analog falls off considerably below 50Hz and above 10KHz. These measurements were confirmed using a calibrated EMC8000 and frequency response software.

Perhaps there's a newer analog model that fixes the older inaccuracies, but I've not seen one.
That's what the correction tables are for. And if you do a search you'll find quite bit of disagreement about what correction values should actually be used for BOTH meters. The analog RS meter is MUCH preferred by most everyone over the digital RS meter. Professionals use analog meters, as well.

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf

That's what the correction tables are for. And if you do a search you'll find quite bit of disagreement about what correction values should actually be used for BOTH meters. The analog RS meter is MUCH preferred by most everyone over the digital RS meter. Professionals use analog meters, as well.

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf

Well I use neither since I have the Behringer, but based on my measurements, if I had to use one and didn't want to bother with correction tables, the digital model works just fine on its own for most HT calibration purposes.

They are both equally accurate (or inaccurate; however you want to look at it). Most people prefer to use the analog model.

Agreed on inaccurate. :D

But I disagree on analog. I prefer the digital because it's easier to read when measuring pink noise. The amplitude of noise varies a lot over time, especially at low frequencies. But in the grand scheme of things both models work fine for their intended purpose.

--Ethan

Not only heard it, but measured it myself since I have both. The digital model is within 1dB from 20Hz - 20KHz. The analog falls off considerably below 50Hz and above 10KHz. These measurements were confirmed using a calibrated EMC8000 and frequency response software.



The specifications indicate otherwise.... the meter does not have a flat response from 20hZ-20khZ (500-10khZ +-3db, A weighting,) .

Typical response from the digital and analog meter below

I know that others here were interested in the specs to correct the non-linearities of the factory stock RS SPL meter. The figures below are to be either added to (+) or subtracted from (-) the readings that you obtain from your factory stock meter. In other words, the meter in stock form is EXTREMELY deficient when it comes to taking low frequency measurements. Keep in mind that these corrections are only valid under the following conditions. The meter must be set to C weighting, using 1/3 octave pink noise (easily available from various CDs), with the mic pointed at the speaker. These measurements were verified on both the RS analogue and digital meters using laboratory grade test equipment. Baseline testing was done using the 80 dB scale for reference purposes. While on the low side, this should give you a good baseline as to what your actually getting out of your system. Needless to say, if you had BIG peaks in the bass region with the stock meter and you weren't calculating in these correction figures, you're in even worse shape than you thought.

10Hz +20.5
12.5Hz +16.5
16Hz +11.5
20Hz +7.5
25Hz +5
31.5Hz +3
40Hz +2.5
50Hz +1.5
63Hz +1.5
80Hz +1.5
100Hz +2
125Hz +0.5
160Hz -0.5
200Hz -0.5
250Hz +0.5
315Hz -0.5
400Hz 0
500Hz -0.5
630Hz 0
800Hz 0
1KHz 0
1.25Khz 0
1.6KHz -0.5
2Khz -1.5
2.5Khz -1.5
3.15Khz -1.5
4KHz -2
5KHz -2
6.3KHz -2
8KHz -2
10Khz -1
12.5KHz +0.5
16KHz 0
20KHz +1

Is there really a particular reason that everybody uses the Radio Shack SPL meter or can I use another SPL meter? I just ask because there are several i've looked at on ebay at good prices, but they weren't Radio Shack. Just didn't know if there was something special about it in particular. Thanks.

The reason it's frequently used is because it's commonly available, inexpensive, and correction factors have been developed to make it usefully accurate for doing frequency response mapping.

For the general purpose of calibrating the speakers to equal volume, any one is better that nothing. That's because it's mostly a relative measurement vs an absolute measurement in that regard.

Sure, there is the part about calibrating to reference level, but really, that's not such a big deal IMO. I assume most of us play the system at a pleasing (or in some cases tolerated) level regardless of what the absolute decibel level is.

I have to ask this-I am sure there are a few others who might be in my boat.
A. 50Hz +1.5
63Hz +1.5
80Hz +1.5
What does the 50Hz mean (I know what it means- but not how to use it to help me calibrate the sound) also +1.5?

B. To calibrate, I attach my RS SPL to a tri-pod at PLP {70dB>Slow>C weight). > aimed at the ceiling use AVIA test tones. Master vol. control at -0-. Then change the individual speakers dB to +_- . To make the SPL to dial register right at _0_. However, I do not understand how to use the table above.

You don't really need to fully understand the frequency response characteristics above to calibrate your AV system. What the information above indicates... is the relative magnitude of the SPL meter reading above or below a calibrated level at various frequencies. Since the meter is used for all channels in your AV setup, and you are using the pink noise from the AVIA disk, you will not need to make any adjustments to the speaker output levels above the actual SPL meter readings. Pink noise contains a large frequency swath used for calibration of your AV equipment.

With the SPL meter set as you indicated ( I would use a level around 80-85db), you would allow your AV processor or reciever to send out the pink noise through each speaker successively. While measuring each speaker level with the meter, you want to adjust the speaker level to maintain the same level coming from all speakers (somewhere between 80-85db, your choice).

Does this help?

Ok, got a really noob question here........
I see people setting levels of 75-85db to do a level calibration. On my Yamaha RX-V3800, the default max volume setting from the factory is +16, and can be adjusted.
If I were to set the volume at said +16, and do a level check, I'd probably shatter the windows, blow the speakers and my eardrums. :D
How are you folks setting at 75-85 and then using the meter to calibrate levels?

Turn on the test tone sequence, adjust the volume level to read 75dB on the meter... I can just about guarantee the volume control ain't gonna be +16 to get to 75dB with the test tones. On some (many?) receivers/processors the volume control is disabled during calibration and automatically referenced to the 0dB position.

I'd suggest you RTFM for the 3800 to see how the calibration sequence works for that model. ;) If it has the auto calibration routine, which I assume it does, that should get you fairly close. Some like to double check with the SPL meter.

Ok, got a really noob question here........
I see people setting levels of 75-85db to do a level calibration. On my Yamaha RX-V3800, the default max volume setting from the factory is +16, and can be adjusted.
If I were to set the volume at said +16, and do a level check, I'd probably shatter the windows, blow the speakers and my eardrums. :D
How are you folks setting at 75-85 and then using the meter to calibrate levels?

Remember....75db is 75dB. If you have your receiver on +16 and are ABLE to obtain a 75dB rating on the SPL meter for each speaker, then when you watch movies and turn your master volume to +16, it will be at 75dB. Now, if you crank your master volume down to +5 and calibrate it to 75dB, guess what....when you watch a movie at +5, it will be at 75dB....same EXACT volume level it was at +16 on the Master volume. It doesn't matter where your Master Volume Level is set, given you can actually dial in 75dB (85 or whatever you choose).

The specifications indicate otherwise.... the meter does not have a flat response from 20hZ-20khZ (500-10khZ +-3db, A weighting,) .

Typical response from the digital and analog meter below

I know that others here were interested in the specs to correct the non-linearities of the factory stock RS SPL meter. The figures below are to be either added to (+) or subtracted from (-) the readings that you obtain from your factory stock meter. In other words, the meter in stock form is EXTREMELY deficient when it comes to taking low frequency measurements. Keep in mind that these corrections are only valid under the following conditions. The meter must be set to C weighting, using 1/3 octave pink noise (easily available from various CDs), with the mic pointed at the speaker. These measurements were verified on both the RS analogue and digital meters using laboratory grade test equipment. Baseline testing was done using the 80 dB scale for reference purposes. While on the low side, this should give you a good baseline as to what your actually getting out of your system. Needless to say, if you had BIG peaks in the bass region with the stock meter and you weren't calculating in these correction figures, you're in even worse shape than you thought.

10Hz +20.5
12.5Hz +16.5
16Hz +11.5
20Hz +7.5
25Hz +5
31.5Hz +3
40Hz +2.5
50Hz +1.5
63Hz +1.5
80Hz +1.5
100Hz +2
125Hz +0.5
160Hz -0.5
200Hz -0.5
250Hz +0.5
315Hz -0.5
400Hz 0
500Hz -0.5
630Hz 0
800Hz 0
1KHz 0
1.25Khz 0
1.6KHz -0.5
2Khz -1.5
2.5Khz -1.5
3.15Khz -1.5
4KHz -2
5KHz -2
6.3KHz -2
8KHz -2
10Khz -1
12.5KHz +0.5
16KHz 0
20KHz +1




Those numbers are suspect to me. If you use a RS SPL as an SPL meter, those numbers are useless. The SPL A scale is a specific weighted SPL scale. The SPL C scale is a specific weighted SPL scale.

For some reason, people are trying to claim that an RS SPL meter is "inaccurate" at low or high frequencies. Inaccurate as compared to what? The defined SPL A scale? The defined SPL C scale?


http://hyperphysics.phy-astr.gsu.edu/hbase/sound/acont.html#c1


For some reason people think that a RS SPL meter should read the same way as a flat measurement microphone (AKA flat). It was not designed to do that . For that matter, no other SPL meter is designed to do that either unless it has an absolute scale.

Professionals use analog meters, as well.




Professionals calibrate with an RTA. They are supposed do daily level checks with an SPL meter, but those "normal" readings are supposed to be measured at the same time as the RTA readings.

There are two uses for calibration.

One is to make all channels equal in volume level. You can use any SPL number to do that.

The second use is to determine what the volume setting is used to give you Dolby "Reference Playback Level".

A lot of THX units do not use the Dolby "Reference Level" as the calibration standard. They use the THX "Reference Level" as the calibration standard.

The frequency response of the meter is relevant only if you're using it as a spectrum analyzer in order to EQ a room. For setting up the channel levels in your receiver or processor using a pink noise generator, they are irrelevant.

Those numbers are suspect to me. If you use a RS SPL as an SPL meter, those numbers are useless. The SPL A scale is a specific weighted SPL scale. The SPL C scale is a specific weighted SPL scale.

For some reason, people are trying to claim that an RS SPL meter is "inaccurate" at low or high frequencies. Inaccurate as compared to what? The defined SPL A scale? The defined SPL C scale?


http://hyperphysics.phy-astr.gsu.edu/hbase/sound/acont.html#c1


For some reason people think that a RS SPL meter should read the same way as a flat measurement microphone (AKA flat). It was not designed to do that . For that matter, no other SPL meter is designed to do that either unless it has an absolute scale.

Perhaps "inaccurate" was the wrong word to use. The RS SPL does not have a flat response which, for the purposes of calibrating speaker levels, may result in inaccurate calibration.

For some reason people think that a RS SPL meter should read the same way as a flat measurement microphone (AKA flat). It was not designed to do that .

Afaik, that's what the correction factors are supposed to do - make up for the non-flat response characteristics when the RS meter is used as the mic with something like REQW.

Also, afaik, the correction factors have been developed by taking an average of the RS meter compared to calibrated flat measurement mics.

The frequency response of the meter is relevant only if you're using it as a spectrum analyzer in order to EQ a room. For setting up the channel levels in your receiver or processor using a pink noise generator, they are irrelevant.
Well, not entirely irrelevant.

From my response in THIS (http://www.avsforum.com/avs-vb/showthread.php?t=952429) thread:

"But because of the inaccuracy of the meter at lower frequencies, if you calibrate the sub using AVIA to the exact same level as your speakers, the sub will be a few dBs too hot. Many people prefer this, so they leave it be. If you want to calibrate the sub more accurately, then it should be calibrated ~82dB (72dB) relative to the 85dB (75dB) used for the speakers. The level to calibrate the sub is approximate because everyone's sub sounds a little bit different with the tones (which are NOT LFE) depending upon the crossover used, the speakers' capabilities, the sub's capabilities, as well as room effects. In the end, the best way is to adjust the sub is to adjust it a few dB either way to taste, by ear."

Folks,

I question the validity of all correction curves for the RS meter for many reasons. First, measuring the response of an SPL meter is not at all trivial, and to do it properly requires $1,000 worth of time in an anechoic chamber plus a known-accurate loudspeaker. Further, who's to say that all RS meters are the same? I imagine RS buys whatever microphone capsules are cheapest on the Chinese market at any given time. More to the point, I've compared my own RS meter with an expensive calibrated AKG microphone, and they tracked within 1 dB from 20 Hz to 800 Hz. Above 800 Hz even with correction the RS meter was way off. Graphs below.

--Ethan

http://www.ethanwiner.com/misc-content/etf_calib_lf.gif

http://www.ethanwiner.com/misc-content/etf_calib.gif

I question the validity of all correction curves for the RS meter for many reasons. First, measuring the response of an SPL meter is not at all trivial, and to do it properly requires $1,000 worth of time in an anechoic chamber plus a known-accurate loudspeaker. Further, who's to say that all RS meters are the same? I imagine RS buys whatever microphone capsules are cheapest on the Chinese market at any given time. More to the point, I've compared my own RS meter with an expensive calibrated AKG microphone, and they tracked within 1 dB from 20 Hz to 800 Hz. Above 800 Hz even with correction the RS meter was way off. Graphs below.
As filmnut pointed out, it's essentially irrelevant for system calibration.

But my understanding is that, regardless of whether the correction values are correct, valid, useful, or not, there is actually little variation (imprecision) from one identical RS meter to the next.

HERE (http://www.avsforum.com/avs-vb/showthread.php?t=505236) is a relevant thread regarding the correction values.

Ethan I have some time at the office this week. I am going to use the Mic compare of SMAART and do a few responses of the Rat shack and maybe a couple of others. It would be interesting to see if 2 rat shacks measure the same mine against yours. I suspect you are right about different parts at different times.

Well, not entirely irrelevant.

From my response in THIS (http://www.avsforum.com/avs-vb/showthread.php?t=952429) thread:

"But because of the inaccuracy of the meter at lower frequencies, if you calibrate the sub using AVIA to the exact same level as your speakers, the sub will be a few dBs too hot. Many people prefer this, so they leave it be. If you want to calibrate the sub more accurately, then it should be calibrated ~82dB (72dB) relative to the 85dB (75dB) used for the speakers. The level to calibrate the sub is approximate because everyone's sub sounds a little bit different with the tones (which are NOT LFE) depending upon the crossover used, the speakers' capabilities, the sub's capabilities, as well as room effects. In the end, the best way is to adjust the sub is to adjust it a few dB either way to taste, by ear."

Yes, you're quite right. I forgot about the sub channel.

Yes, you're quite right. I forgot about the sub channel.


Don't be so sure about what is right and wrong.


Read part 8 from the SVsound SPL meter section.

http://www.svsound.com/questions-faqs.cfm


"What to set the sub to? You might find that a higher level, relative to your main speakers is preferable. In other words, set to a bit higher than 75dB, or 85dB, depending on your calibration tone source. Tastes vary and so do movie soundtracks, but your SV Subwoofer is capable of tremendous levels of low distortion, low frequency bass. Take advantage of this, especially if you like action movies with lots of ".1" channel low frequency effects (LFE). Keep in mind too that the human ear is relatively insensitive to low frequencies. This, coupled with the fact most folks don’t watch movies at Dolby Digital reference level (loud!), means tweaking the bass up a few dBs usually yields a better movie sound experience."

"Many of us with SV Subwoofers run a +2 to +6dB setting on the LFE or ".1" channel, but much depends on your room's acoustics whether you have one or more subs, and your typical listening level. With a setting like this, the VE test tone will peak about 81-83dB for the subwoofer portion of the calibration run. Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."

Don't be so sure about what is right and wrong.


Read part 8 from the SVsound SPL meter section.

http://www.svsound.com/questions-faqs.cfm


"What to set the sub to? You might find that a higher level, relative to your main speakers is preferable. In other words, set to a bit higher than 75dB, or 85dB, depending on your calibration tone source. Tastes vary and so do movie soundtracks, but your SV Subwoofer is capable of tremendous levels of low distortion, low frequency bass. Take advantage of this, especially if you like action movies with lots of ".1" channel low frequency effects (LFE). Keep in mind too that the human ear is relatively insensitive to low frequencies. This, coupled with the fact most folks don’t watch movies at Dolby Digital reference level (loud!), means tweaking the bass up a few dBs usually yields a better movie sound experience."

"Many of us with SV Subwoofers run a +2 to +6dB setting on the LFE or ".1" channel, but much depends on your room's acoustics whether you have one or more subs, and your typical listening level. With a setting like this, the VE test tone will peak about 81-83dB for the subwoofer portion of the calibration run. Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."

Hmmm? Your quote supports exactly what sivadselim posted, and I agreed with him, so I'm not sure what you mean by "don't be so sure about what is right and wrong". No one would deny (I hope) that your ear should be the final arbiter of what level is "right".

Hmmm? Your quote supports exactly what sivadselim posted, and I agreed with him, so I'm not sure what you mean by "don't be so sure about what is right and wrong". No one would deny (I hope) that your ear should be the final arbiter of what level is "right".


81 to 83 on the subwoofer portion of the test is based on the 75 dB calibration level for VE. Silvy says to use 73 dB. That is an 8 to 10 dB difference in level!!!

What is it you do or don't take exception to, Cass?

What I quoted myself as saying in Post#24 is generally considered to be the correct way to look at things.

From the SVS link you directed us to there is a "compensation chart (http://www.svsound.com/questions-faqs-rscomp.cfm)". These are the correction values there:

12Hz add 16.5dB
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB

If you notice, from 25Hz to 80Hz, the correction values range from 5dB to 1.5dB. Everyone's subwoofer will "sound" different when calibrating, but the range of frequencies covered by the calibration "tone" will cover and fall somewhere within this range of frequencies. This is why 3dB (an approximate average) is often used as the value that you should consider the meter to incorrect by when calibrating the subwoofer.

If you are going to buy just one piece of audio test gear in your life, I recommend the Radio Shack meter - either digital or analog. Great value for the money. I tend to use a computer + calibrated microphone more often than a pro calibrated sound meter, but that's just me. This lets me use a "flat" calibrated microphone with any software weighting curve I want. Plus I am generally interested as much in frequency content as in a single SPL number, so I use various other analysis software.

The mic is calibrated in two dimensions:

1. For relative flatness, I send it off yearly to a lab which gives me a machine-readable calibration curve, with fractional dB deviation from flatness over the entire frequency range.

2. For absolute level, I use an Acoustic Calibrator specifically designed for the microphone's capsule. This calibrator puts out a 1 kHz reference tone at a fixed and accurate dB level (switchable between 94 dB and 104 dB). The software absolute dB level gets set accordingly.

Regards,
Terry

What is it you do or don't take exception to, Cass?

What I quoted myself as saying in Post#24 is generally considered to be the correct way to look at things.

From the SVS link you directed us to there is a "compensation chart (http://www.svsound.com/questions-faqs-rscomp.cfm)". These are the correction values there:

12Hz add 16.5dB
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB

If you notice, from 25Hz to 80Hz, the correction values range from 5dB to 1.5dB. Everyone's subwoofer will "sound" different when calibrating, but the range of frequencies covered by the calibration "tone" will cover and fall somewhere within this range of frequencies. This is why 3dB (an approximate average) is often used as the value that you should consider the meter to incorrect by when calibrating the subwoofer.



Those correction values are intended to be used with single tones, not for calibration of speakers with pink noise. What, is it too hard to read all the words? SVS tells you how to calibrate speaker levels, and then they tell you how to use the meter for other uses.


"Now if you got this far, and consider yourself an advanced user, you might want to delve a little deeper into the use of the SPL meter to flatten out response peaks in your room (using an external equalizer like we offer) or maybe just using one of the popular test disks out there to check and see just how well your subwoofer is performing. If so, you'll want to use a handy "compensation chart" to adjust the readings of your SPL meter. Its sensitivity down low is NOT uniform, but it's easy to make up for this slight flaw in this great too. This chart is ONLY good for the Radio Shack SPL meter pictured above. If your subwoofer seems to be measuring poorly with low frequencies, this chart is CRITICAL to making sure you know what's what."


Furthermore, those correction numbers track the C scale filter numbers. I don't see any inaccuracy at all. After all it is the SPL C scale, not the absolute scale. Compare the correction numbers to the C scale chart. Is there any difference?

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/acont.html#c5

Those correction values are intended to be used with single tones, not for calibration of speakers with pink noise.
And the pink noise that comes form the subwoofer will falll withing the range of frequencies from (very approximately) 25Hz to 80Hz, and over this range the meter is inaccurate.

BTW, SVS, basically, tells you how to calibrate the subwoofer "hot".


"Now if you got this far, and consider yourself an advanced user, you might want to delve a little deeper into the use of the SPL meter to flatten out response peaks in your room (using an external equalizer like we offer) or maybe just using one of the popular test disks out there to check and see just how well your subwoofer is performing. If so, you'll want to use a handy "compensation chart" to adjust the readings of your SPL meter. Its sensitivity down low is NOT uniform, but it's easy to make up for this slight flaw in this great too. This chart is ONLY good for the Radio Shack SPL meter pictured above. If your subwoofer seems to be measuring poorly with low frequencies, this chart is CRITICAL to making sure you know what's what."
As you point out, this is completely irrelevant when calibrating using pink noise.



HERE (http://www.keohi.com/keohihdtv/experttips/guykuo/avia/avia_a2z.html) you go, Cass. Straight from Gary Kuo. Read the section entitled "Setting Speaker Levels With AVIA". Particularly:

"On occasion, you may be told that your subwoofer should be calibrated to produce an SPL which is 10 dB higher than the other channels. There is no need to do this with AVIA's subwoofer test tones because they are recorded 10 dB softer to automatically produce a 10 dB higher subwoofer setting when you target the same 85 dB SPL. If one wishes to be technically more correct, the 10 dB offset actually is only true if one is using an RTA to measure sound levels. We're using an SPL which would read about 3 dB lower for the same subwoofer setting. If you want to be completely correct, place sub level 3 dB lower at 82 dB instead of 85 dB SPL."


I don't make this sh!t up. We've been over and over this. There is really nothing that is that hard to understand, here.

END OF DISCUSSION :D

Right back at you. The SVS instructions for use with DVE!


Read part 8 from the SVsound SPL meter section.

http://www.svsound.com/questions-faqs.cfm


"What to set the sub to? You might find that a higher level, relative to your main speakers is preferable. In other words, set to a bit higher than 75dB, or 85dB, depending on your calibration tone source. Tastes vary and so do movie soundtracks, but your SV Subwoofer is capable of tremendous levels of low distortion, low frequency bass. Take advantage of this, especially if you like action movies with lots of ".1" channel low frequency effects (LFE). Keep in mind too that the human ear is relatively insensitive to low frequencies. This, coupled with the fact most folks don’t watch movies at Dolby Digital reference level (loud!), means tweaking the bass up a few dBs usually yields a better movie sound experience."

"Many of us with SV Subwoofers run a +2 to +6dB setting on the LFE or ".1" channel, but much depends on your room's acoustics whether you have one or more subs, and your typical listening level. With a setting like this, the VE test tone will peak about 81-83dB for the subwoofer portion of the calibration run. Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."



Then again, you already know that!

http://www.avsforum.com/avs-vb/showthread.php?t=952429


"I am currently using:
Lexicon MC12 – analog from XA2
Toshiba XA2 – speaker settings to large and distances to 0 as Lex does all BM etc.

When running a level test in each of the following I obtained funny results from the HD DVE (both from its HD and SD sides) for my sub.

FL FC FR SR RR RL SL Sub
72 72 72 71 71 71 71 76 - HD DVE HD side using Dolby True HD

72 73 73 71 71 71 71 81 - HD DVE SD side 6.1 test tones using Dolby Digital

75 75 75 75 75 75 75 75 - Internal Lex. Used this to set actual levels

73 73 73 71 --- --- 71 73 - AVIA SD 5.1 DD -is 85 db so I removed 10 db from # for more proper comparison

74 74 74 72 --- --- 72 74 - DVE SD disk – Dolby Digital

76 76 76 78 75 75 77 78 - THX Optimizer on Star Wars A New Hope DVD – Dolby Digital

Which is right? Is the HD DVE (HD and SD sides) wrong for SUB calibration? This may be causing people to set their sub levels too low.

Funny thing is that the DVE SD and the HD DVE disks come from the same manufacture yet DVE SD disk shows a correct sub level vs the HD DVE (SD side) that shows the sub level 10 db too high."


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The Lexicon MC-12 calibrates to THX reference level, so those calibration numbers are 4 dB higher than the others. I would use the Lexicon internal tone generator numbers myself. That's what I use with my receiver (as recommended by Dolby).

The other numbers are all different. Which set of numbers are correct on an absolute basis?

Right back at you. The SVS instructions for use with DVE!


Read part 8 from the SVsound SPL meter section.

http://www.svsound.com/questions-faqs.cfm


"What to set the sub to? You might find that a higher level, relative to your main speakers is preferable. In other words, set to a bit higher than 75dB, or 85dB, depending on your calibration tone source. Tastes vary and so do movie soundtracks, but your SV Subwoofer is capable of tremendous levels of low distortion, low frequency bass. Take advantage of this, especially if you like action movies with lots of ".1" channel low frequency effects (LFE). Keep in mind too that the human ear is relatively insensitive to low frequencies. This, coupled with the fact most folks don’t watch movies at Dolby Digital reference level (loud!), means tweaking the bass up a few dBs usually yields a better movie sound experience."

"Many of us with SV Subwoofers run a +2 to +6dB setting on the LFE or ".1" channel, but much depends on your room's acoustics whether you have one or more subs, and your typical listening level. With a setting like this, the VE test tone will peak about 81-83dB for the subwoofer portion of the calibration run. Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."

And what are you pointing out, exactly? Are you now a proponent of running the subwoofer that "hot"? Are the SVS instructions what YOU follow to calibrate YOUR setup? There is nothing any more relevant (or different) to this thread in what you keep quoting from the SVS site. What are you arguing exactly, anyway, and what part of that argument is the info from the SVS site supposed to support? Why don't you email them for some clarification?

No matter what you use to calibrate with, including a receiver's built-in tones, as long as you know whether the subwoofer calibration tone is "correct" or "incorrect", and how incorrect it is, the "fudge factor" that you use to compensate for the meter's inaccuracy at lower frequencies is, essentially, the same.

No matter how you want to slice it, the meter is less accurate at lower frequencies.

From what you are quoting:

"Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."

It would be interesting to see if 2 rat shacks measure the same mine against yours.

There's no reasonable way to compare yours against mine because mine includes the substantial deviation of the room I measured in. I could have measured a few feet away from one of my (huge) JBL speakers, but the graphs above were measured near the listening position.

--Ethan

It would be interesting to see if 2 rat shacks measure the same mine against yours. I suspect you are right about different parts at different times.
There's no reasonable way to compare yours against mine because mine includes the substantial deviation of the room I measured in. I could have measured a few feet away from one of my (huge) JBL speakers, but the graphs above were measured near the listening position.I guarantee you, though, that if you take 20 completely different independent measurements using the SAME meter in the same room at the same location, then take 20 different independent measurements using 20 different (but identical) meters in that same room at that same location, that the intra-meter and inter-meter deviation is going to be VERY similar.

No matter how you want to slice it, the meter is less accurate at lower frequencies.

From what you are quoting:

"Because the Radio Shack sound meter is relatively insensitive at very low frequencies you'll actually be set several dBs higher than what's read."



Less accurate than what? Not true if your intent is to read SPLs using the SPL C scale as a C scale reading. If you want to convert C scale to something else, then be my guest.

All you need is one peak from your room in the frequency range in question, then your SPL numbers are simply misleading you.

I guarantee you, though, that if you take 20 completely different independent measurements using the SAME meter in the same room at the same location, then take 20 different independent measurements using 20 different (but identical) meters in that same room at that same location, that the intra-meter and inter-meter deviation is going to be VERY similar.



You should use something likeTrue RTA sometime. It will open your eyes a bit!

There's no reasonable way to compare yours against mine because mine includes the substantial deviation of the room I measured in. I could have measured a few feet away from one of my (huge) JBL speakers, but the graphs above were measured near the listening position.

--Ethan


I can get those same differences using the same mike just by moving the mike a small amount. How did you handle locating the two mikes? One after the other? Tape them together? In a fixed mike stand?

Less accurate than what? Not true if your intent is to read SPLs using the SPL C scale as a C scale reading. If you want to convert C scale to something else, then be my guest.

All you need is one peak from your room in the frequency range in question, then your SPL numbers are simply misleading you.Cass, what Gary Kuo says is absolutely correct. If you want to calibrate your sub "absolutely" to 75dB, then you should calibrate with a meter reading of ~72dB. 85dB? Calibrate with the meter reading ~82dB. 79dB? Calibrate with a meter reading ~76dB. It's pretty simple. If the calibration tone is known to be "off" by a certain number of dBs (as it once supposedly was with DVE) then all you do is simply mathematically compensate by that EXACT number of dBs. But the correction "fudge factor" should still be applied to the meter's reading.

That the correction value is approximately 3dB is due to the fact that everyone's subwoofer will reproduce the pink noise a little differently depending upon several different factors. C-weighting does NOT compensate for the meter's inaccuracy at lower frequencies.

You should use something likeTrue RTA sometime. It will open your eyes a bit!
I'm not sure what that has to do with the inherent variability of the RS meter used by a human being.

... C-weighting does NOT compensate for the meter's inaccuracy at lower frequencies.

The RS meter is technically not inaccurate at low frequencies. It correctly applies the dB(C) filter which results in lower readings at lower frequencies. This is how it is designed to work, and as a result makes the RS meter an inaccurate tool for measuring subwoofer output if you do not compensate for the dB(C) filter.

Cass, what Gary Kuo says is absolutely correct. If you want to calibrate your sub "absolutely" to 75dB, then you should calibrate with a meter reading of ~72dB. 85dB? Calibrate with the meter reading ~82dB. 79dB? Calibrate with a meter reading ~76dB. It's pretty simple. If the calibration tone is known to be "off" by a certain number of dBs (as it once supposedly was with DVE) then all you do is simply mathematically compensate by that EXACT number of dBs. But the correction "fudge factor" should still be applied to the meter's reading.

That the correction value is approximately 3dB is due to the fact that everyone's subwoofer will reproduce the pink noise a little differently depending upon several different factors. C-weighting does NOT compensate for the meter's inaccuracy at lower frequencies.



Your comment "C-weighting does NOT compensate for the meter's inaccuracy at lower frequencies" is meaningless. The C scale filter is the reason for the so called inaccuracy at lower frequencies. Also unless your subwoofers FR is perfectly flat at the listening position, the SPL reading will be misleading.

Do you set your RS SPL meter to read AVE, or MAX? You get two different SPL numbers just by doing that (primarily from the subwoofer test).

I use the receiver test tones so I don't have to guess on what test disk is correct or what source is correct. After all, I use my receiver for other things besides Dolby Digital being played from a DVD player.

The RS meter is technically not inaccurate at low frequencies. It correctly applies the dB(C) filter which results in lower readings at lower frequencies. This is how it is designed to work, and as a result makes the RS meter an inaccurate tool for measuring subwoofer output if you do not compensate for the dB(C) filter.


I would use the phrase ... and as a result makes the RS meter an inaccurate tool for measuring the subwoofers Frequency Response if you do not compensate for the dB(C) filter.

Pretty much any SPL meter has the same problem unless they have an absolute SPL scale.

Calibrating microphones is much more difficult than most people imagine! Earthworks Precision Audio has a paper on how they test their cal microphones.
"How Earthworks Measures Microphones"
http://www.earthworksaudio.com/tech/ew_measures_mics.pdf

I would think that almost all the DIY calibration curves are wrong.

So, again, Cass, I ask what it is you do or don't take exception to. Even if you use the receiver's test tones to calibrate, the meter is STILL inaccurate at lower frequencies and this should be taken into account when using it to calibrate your subwoofer(s).

So, again, Cass, I ask what it is you do or don't take exception to. Even if you use the receiver's test tones to calibrate, the meter is STILL inaccurate at lower frequencies and this should be taken into account when using it to calibrate your subwoofer(s).


I don't use compensation for the SPL meter C scale to calibrate speaker levels. My subwoofers bandwidth is lower than what most people use, so my numbers do not translate to other setups. As a matter of fact, I do not measure the subwoofer with an SPL meter anymore. I use my ears, then check with an SPL meter to make sure that the number is reasonable.

For that matter, my receiver has an option to send audio to any two adjacent channels instead of test tones. I use that to set my main speaker phantom images to sound right by doing a 360 degree test, one pair after the other. The surrounds sound too loud if the main speaker levels are all set to measure be equal in SPL level.


Read the calibration procedures here:

http://www.grammy.com/PDFs/Recording_Academy/Producers_And_Engineers/5_1_Rec.pdf

With the use of an SPL meter, they say to use C scale slow. They do not say to use any compensation at all. Just to use the plain old SPL C scale.

They also say:

"RTA metering is the preferred method for calibrating a surround sound speaker system because an
SPL meter will yield a less accurate result since only the peak of one band is
measured. If an SPL meter is used, set it to C-weighting on the slow scale.
It is also helpful to have a number of well-recorded commercial surround sound
releases on hand to play back in order to do final “tweaking” by ear."

In other words, a bad room (like most rooms) will give you a deceptive number for the subwoofer measurement.


As far as levels are concerned:

"The final step is to set the level of each subwoofer relative to that of the main
speakers. Common practice is to calibrate the subwoofer approximately 4dB
above the reference level of the main speakers. This procedure differs
somewhat depending upon whether the subwoofer is receiving the LFE channel
only or whether bass management is being utilized to route signal to it from some
or all of the main channels."

I don't use compensation for the SPL meter C scale to calibrate speaker levels.
No need to; you calibrate the speakers to the same exact relative level. It doesn't matter at all what the meter "reads"; only that it is consistent.

As a matter of fact, I do not measure the subwoofer with an SPL meter anymore. I use my ears, then check with an SPL meter to make sure that the number is reasonable.
That's great. I sort of do this, too.

But the meter still becomes increasingly inaccurate at lower frequencies. How we prefer to calibrate is irrelevant.


For that matter, my receiver has an option to send audio to any two adjacent channels instead of test tones. I use that to set my main speaker phantom images to sound right by doing a 360 degree test, one pair after the other. The surrounds sound too loud if the main speaker levels are all set to measure be equal in SPL level.So what you are saying is that you calibrate how you damn well please. Which is perfectly fine.

But I still don't see what in the world 'how you prefer to calibrate' has anything at all to do with the fact that a RS SPL meter becomes increasingly inaccurate at lower frequencies.


Read the calibration procedures here:
Why????? :confused:

At issue (although, honestly, what's at issue is not really clear to me), I think, is whether the RS SPL meter becomes increasingly inaccurate at lower frequencies. If you can refute that, please do. If not, what are we discussing? We're not discussing calibration proceedures. At least I'm not. Not yours, SVS's, the Recording Academy's, mine, or ANYONE else's. That's irrelevant.



THE RS SPL METER BECOMES INCREASINGLY INACCURATE AT LOWER FREQUENCIES. :D

No need to; you calibrate the speakers to the same exact relative level. It doesn't matter at all what the meter "reads"; only that it is consistent.





Last that I heard the subwoofer is a speaker. You say to calibrate it at a lower relative level. Even assuming that is an accurate way to calibrate, that would only apply to people who playback at full reference level.







So what you are saying is that you calibrate how you damn well please. Which is perfectly fine.




No, I am saying that SPL meters in general do not measure the way that you think that they do. Take two identical speakers, locate them in two different parts of the room, and the in room flatness of the FR will vary. If you set the speakers to measure the same with an SPL meter, that does not mean that they will be playing back at the same level due to those FR variations. The SPL meter is stupid - it measures different than the way that your ear hears.

If you have a digital version of the RS SPL meter, you can measure AVE or MAX. MAX takes peaks into account, and AVE does not do so to the same extent. Which setting do you use? They are both used with the C scale filters and slow response setting.






At issue (although, honestly, what's at issue is not really clear to me), I think, is whether the RS SPL meter becomes increasingly inaccurate at lower frequencies. If you can refute that, please do. If not, what are we discussing? We're not discussing calibration proceedures. At least I'm not. Not yours, SVS's, the Recording Academy's, mine, or ANYONE else's. That's irrelevant.



THE RS SPL METER BECOMES INCREASINGLY INACCURATE AT LOWER FREQUENCIES. :D



Most (it not all) professional sources for methods of measuring with an SPL meter do not say to set the SPL meter to C scale slow, then use compensation tables to correct your SPL readings. Like I said before, the RS SPL meter is inaccurate as compared to what?

The RS SPL meter has an accurate A and C scale readout as compared to the A and C scale standards. If you intent is to use the RS SPL meter as a flat measurement mike for FR measurements, then you can try C scale compensation factors.

By the way, look at those compensation factors posted earlier in the thread. Look at the high end compensation factors and compare them to the C scale standard. They do not match.

Nothing special about the meter, it's just easy to find and priced nicely. BTW, get an analog model if you can, it makes calibration much easier.

Agreed the needle is easy on the eye. I’ve used the analogue RS SPL meter for 18 years.

At issue (although, honestly, what's at issue is not really clear to me), I think, is whether the RS SPL meter becomes increasingly inaccurate at lower frequencies. If you can refute that, please do. If not, what are we discussing? We're not discussing calibration proceedures. At least I'm not. Not yours, SVS's, the Recording Academy's, mine, or ANYONE else's. That's irrelevant.



THE RS SPL METER BECOMES INCREASINGLY INACCURATE AT LOWER FREQUENCIES. :D

This has already been refuted. It is not inaccurate, it gives you that results you ask for, an accurate measurement filtered with a C-weighted, logarithmic scale. Your measurements are inaccurate because you're using the wrong tool for the job. It is not designed to give a flat measurement at low frequencies, so why would you expect it to?

Lots of confusion in this thread probably because RS has sold lots of different meters over the years under the same name. They all work about the same when reading the meter, the LF is rolled off with either A or C weighting. What varies is the RCA output. Some models apply the A or C weighting to the RCA out and some output a (relatively) flat signal. It's a matter of where they tapped off the output in the circuit, before or after the A/C filter.

The only way to know for sure is to test it. Use the meter as a mic for software like REW and make sure no mic cal file or C weighting is applied by REW. Play some tones and see if the reading in REW matches the meter's reading or at least has a consistent difference. If it does, the meter is applying weighting to the RCA. If REW starts reading much higher than the meter as you go lower, the meter isn't applying weighting to the RCA.

I can get those same differences using the same mike just by moving the mike a small amount. How did you handle locating the two mikes? One after the other? Tape them together? In a fixed mike stand?

I did not put them adjacent because I wanted to avoid interaction. So I carefully placed the front of each capsule by eye. They were within at least one inch of each other if not half that. But I also had two other advantages.

First, my home studio has a fair amount of bass tapping, so at low frequencies the response varies much less than in an untreated room. And for the high frequency graph I used 1/3 octave averaging to reduce the changes over distance. I don't pretend this is as accurate as a "real" test in an acoustics lab. But it's at least in the ball park, and proves to my satisfaction that most of the "correction charts you see are incorrect if well-intentioned.

--Ethan

Just thought I'd add an observation I made concerning the low end response of the digital RS meter. When I first got my HSU VTF2 sub, I used the meter to measure the output, and then compared it to published measurements taken by Tom Nousaine. Using the published Rives Audio adjustments,

20 +7.5
25 +5
31.5 +3
40 +2.5
50 +1.5
63 +1.5
80 +1.5

which were based on the analog RS model, my measurements almost perfectly matched Mr. Nousaine's. Just an FYI.

Rob

Here is an SPL A scale and C scale calculator. This can be used to convert any SPL meter to an absolute scale subject to meter tolerance and measurement with fresh batteries.


http://www.sengpielaudio.com/calculator-dba-spl.htm


There is also a note: "There is no formula for conversion from dBA to dBSPL and vice versa."


Note that when any battery operated equipment is calibrated, brand new fresh batteries are installed prior to calibration.

Just thought I'd add an observation I made concerning the low end response of the digital RS meter. When I first got my HSU VTF2 sub, I used the meter to measure the output, and then compared it to published measurements taken by Tom Nousaine. Using the published Rives Audio adjustments,

20 +7.5
25 +5
31.5 +3
40 +2.5
50 +1.5
63 +1.5
80 +1.5

which were based on the analog RS model, my measurements almost perfectly matched Mr. Nousaine's. Just an FYI.

Rob



Those are all single tones.

So, what's the consensus on Analog vs Digital?
I am able to get a Analog Radio Shack SPL meter for 50€ which is a good price. Unfortunately they don't ship the Digital version. Am I missing on something if I just stick with the analog?

Can I connect either model to my line-in in order to produce FR graphs, or is this feature reserved for the digital model?