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RS SPL meter useless for In-room subwoofer response? - Page 2

post #31 of 154
7/8/09 at 8:20am
Look at the JBL in room target FR response. The posters who like to EQ flat must hate JBL!









Link to JBL Synthesis technology


.
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post #32 of 154
7/8/09 at 8:27am
...and considering the amount of r&d that harman puts into correlating sound characteristics with subjective impressions, you can bet that target frequency response wasn't randomly selected.

(however, that frequency response is meant for movies, if i recall correctly)
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post #33 of 154
7/8/09 at 8:34am
That's room response which would be more akin to a sound power measurement, which would not be flat even for a perfectly flat anechoic derived response. Knowing the measurement conditions are everything in understanding the data.
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post #34 of 154
7/8/09 at 8:40am
Quote:
Originally Posted by LTD02 View Post

...and considering the amount of r&d that harman puts into correlating sound characteristics with subjective impressions, you can bet that target frequency response wasn't randomly selected.

(however, that frequency response is meant for movies, if i recall correctly)



Rolling off at 30 Hz for movies?

Anyhow, that FR target is in the ballpark to the way that my system measures after I fine tune levels by ear.
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post #35 of 154
7/8/09 at 8:47am
Quote:
Originally Posted by augerpro View Post

That's room response which would be more akin to a sound power measurement, which would not be flat even for a perfectly flat anechoic derived response. Knowing the measurement conditions are everything in understanding the data.



Anechoic measurements are not made by anyone on this forum. Most people here tend to post measurements of the in room FR on a very limited frequency basis (AKA subwoofer area).

This is not rocket science!
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post #36 of 154
7/8/09 at 9:06am
http://JBL HOM Owner's Manual



• Target Curves:

Intuitive logic would tend to indicate that the best sound would be achieved when the system delivers flat frequency response. While this is true for all other components in the audio chain, this is definitely not true in the case of loudspeakers installed in listening rooms. There are several reasons for this, and it has taken many years of research to establish just what the most desirable performance characteristics are.

• Ideal Low-Frequency Response

Room boundaries (walls, ceiling and floor) tend to contain low-frequency energy within the room. Simply stated, this results in a boost in low-frequency energy. This is true whether it is a speaker or a piano producing the sound. The exact frequency at which this effect begins and the amount of boost realized are a function of the room size, shape and wall construction. No two spaces are ever exactly alike. This same low-frequency enhancement also occurs in recording studios, and the recording engineers know this will occur during playback. They balance their recordings in anticipation of this. Therefore, it would be wrong to “flatten” the speaker system response in the playback environment. To do so only results in a thin bass sound.

By surveying many listening rooms over the years, JBL engineers have established a low-frequency response characteristic that delivers the most consistently satisfactory results. This has been confirmed through extensive subjective evaluation tests.
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post #37 of 154
7/8/09 at 9:26am
Quote:
Originally Posted by J_Palmer_Cass View Post

Rolling off at 30 Hz for movies?

while most folks around here would disagree, the idea of rolling off at 30hz has its advantages.

systems designed in that way tend to maximize spl in the 30-40hz range.

big spl in that region is probably subjectively more impactful in blind listening tests than extension down to 5hz or whatever.

the lower your tuning frequency, the lower your efficiency and maximum spl in the 30-40hz region.

it's all tradeoffs.

i hate to beat a dead horse, but the frequency response of the mastering studio must be considered. those guys are not running systems that are flat to 5hz. they rolloff; most of them as the jbl frequency response target. as a result, if you have a system that is flat to 5hz, you are just way overblowing the subharmonics. and while this may be fun, it is a distortion. a closing car door should not sound like a dinosaur stomping the ground.

ok, flame suit on.
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post #38 of 154
7/8/09 at 9:28am
Quote:
Originally Posted by J_Palmer_Cass View Post

http://JBL HOM Owner's Manual



Target Curves:

Intuitive logic would tend to indicate that the best sound would be achieved when the system delivers flat frequency response. While this is true for all other components in the audio chain, this is definitely not true in the case of loudspeakers installed in listening rooms. There are several reasons for this, and it has taken many years of research to establish just what the most desirable performance characteristics are.

Ideal Low-Frequency Response

Room boundaries (walls, ceiling and floor) tend to contain low-frequency energy within the room. Simply stated, this results in a boost in low-frequency energy. This is true whether it is a speaker or a piano producing the sound. The exact frequency at which this effect begins and the amount of boost realized are a function of the room size, shape and wall construction. No two spaces are ever exactly alike. This same low-frequency enhancement also occurs in recording studios, and the recording engineers know this will occur during playback. They balance their recordings in anticipation of this. Therefore, it would be wrong to flatten the speaker system response in the playback environment. To do so only results in a thin bass sound.

By surveying many listening rooms over the years, JBL engineers have established a low-frequency response characteristic that delivers the most consistently satisfactory results. This has been confirmed through extensive subjective evaluation tests.

lol. i almost cut that exact same section out of the pdf to post. very nice!
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post #39 of 154
7/8/09 at 9:42am
From the same manual: "The Synthesis target curves are derived from data in many typical installations. They represent a trend of what should be expected, not a specific shape that must be achieved for good sound. They help in the setting of overall levels, and are useful for diagnostics and troubleshooting."
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post #40 of 154
7/8/09 at 9:45am
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

while most folks around here would disagree, the idea of rolling off at 30hz has its advantages.

systems designed in that way tend to maximize spl in the 30-40hz range.

big spl in that region is probably subjectively more impactful in blind listening tests than extension down to 5hz or whatever.

the lower your tuning frequency, the lower your efficiency and maximum spl in the 30-40hz region.

it's all tradeoffs.

i hate to beat a dead horse, but the frequency response of the mastering studio must be considered. those guys are not running systems that are flat to 5hz. they rolloff; most of them as the jbl frequency response target. as a result, if you have a system that is flat to 5hz, you are just way overblowing the subharmonics. and while this may be fun, it is a distortion. a closing car door should not sound like a dinosaur stomping the ground.

ok, flame suit on.

lmao, I like car door shaking my room

I do remember testing a bunch of curves and the best one was when I bump 25Hz to 35Hz in my system, Maybe that is why people love the JLs so much, they are maximized for that frequency range.

The "bent knee curve" discussion is a great one. Im going to apply it to my setup and experience what it sounds like.

Sorry to the OP for the OT Thats me but its secondary to the problem in the thread.
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post #41 of 154
7/8/09 at 9:47am
Thread Starter 
Quote:


The posters who like to EQ flat must hate JBL!

I hate flat that is why I have a hard time with Audyssey and why Im buy the Audyssey pro software (Im also curious if the pro stuff will do my SSF for me).
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post #42 of 154
7/8/09 at 9:49am
Quote:
Originally Posted by LTD02 View Post

while most folks around here would disagree, the idea of rolling off at 30hz has its advantages.

systems designed in that way tend to maximize spl in the 30-40hz range.

big spl in that region is probably subjectively more impactful in blind listening tests than extension down to 5hz or whatever.

the lower your tuning frequency, the lower your efficiency and maximum spl in the 30-40hz region.

it's all tradeoffs.

i hate to beat a dead horse, but the frequency response of the mastering studio must be considered. those guys are not running systems that are flat to 5hz. they rolloff; most of them as the jbl frequency response target. as a result, if you have a system that is flat to 5hz, you are just way overblowing the subharmonics. and while this may be fun, it is a distortion. a closing car door should not sound like a dinosaur stomping the ground.

ok, flame suit on.



I don't disagree.

The following is the electronic EQ that is applied to my passive subwoofer(s). 23 Hz is the "rolloff" frequency that I use for the reasons that you mentioned above. With a HP much lower than that, then I need more drivers and amplifiers to get the same SPL output.


.
LL
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post #43 of 154
7/8/09 at 9:57am
Thread Starter 
Nice curve, looks like an exaggerated "Bent Knee" curve and I like the potential (make sense in my head but I do not know why). Time to experiment and I have a nature peak in the 25 Hz range !!

NXT, JBL, etc have been doing this stuff correctly for awhile, we just don't learn about it in threads like the Audyssey thread.
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post #44 of 154
7/8/09 at 10:03am
Quote:
Originally Posted by augerpro View Post

From the same manual: "The Synthesis target curves are derived from data in many typical installations. They represent a trend of what should be expected, not a specific shape that must be achieved for good sound. They help in the setting of overall levels, and are useful for diagnostics and troubleshooting."



Sounds logical to me. Typical trend of what should be expected when speakers are measured in room. The trend is not "flat"!

The in room FR of my system as adjusted must be typical to many installations. The low end is boosted by about 8 dB in that typical curve, low end rolloff around 25 Hz, and high end roll off around 12 kHz. My speakers are spec'd flat to 26 kHz, so I tend to ignore in room meaurements of anything above 8 kHz myself.
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post #45 of 154
7/8/09 at 10:05am
I think the "Hard Knee" is just an acknowledgment that the room gain does not come on gradually (as in a curve) but somewhat abruptly at a given frequency. For example when doing the driver measurements in garage you can quite clearly see the room take over at 30hz, and it's not real gradual.
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post #46 of 154
7/8/09 at 10:13am
Quote:
Originally Posted by J_Palmer_Cass View Post

I don't disagree.

The following is the electronic EQ that is applied to my passive subwoofer(s). 23 Hz is the "rolloff" frequency that I use for the reasons that you mentioned above. With a HP much lower than that, then I need more drivers and amplifiers to get the same SPL output.


.

that is interesting. what are you running for mains?
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post #47 of 154
7/8/09 at 10:19am
Quote:
Originally Posted by penngray View Post


Nice curve, looks like an exaggerated "Bent Knee" curve and I like the potential (make sense in my head but I do not know why). Time to experiment and I have a nature peak in the 25 Hz range !!




Most of that EQ is applied to compensate for the natural rolloff of my passive subwoofers. Commercial subwoofers apply EQ in their amplifers to flatten out the FR of the subwoofer/amplifier package. They just don't tell you that they do it.




Quote:
Originally Posted by penngray View Post


NXT, JBL, etc have been doing this stuff correctly for awhile, we just don't learn about it in threads like the Audyssey thread.


This thread brings up things that I like to evaluate. This thread starts out as a RS SPL meter or mike thread, Audyssey works its way in quickly, the HT Shack "Bent Knee" EQ is mentioned, and we end up looking at JBL target curves.

I have to update my in multi seat room curves now that my JPC MBM has not been adjusted for a long time. Off hand, I am sure that I am close to the typical JBL FR curve. I know that I am not flat, but I am not sure if I have that 8 dB boost in room for the bass.
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post #48 of 154
7/8/09 at 10:21am
Thread Starter 
Well this thread will probably get back on topic with toddRiffic posts again. Its really about his problem and I still want to understand what Audyssey is doing and Im sure he wants to fix his problem, which is the fact that Audyssey creates a null when calibrating his new sub.


I did like the NXT info, I always wondered why the did their EQing that way.
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post #49 of 154
7/8/09 at 10:24am
Quote:
Originally Posted by LTD02 View Post

that is interesting. what are you running for mains?



Sealed NHT 2.1 for R & L mains. Kind of an older speaker. Good to about 45 Hz. I run the mains as large and fill in the low end with the subwoofer(s).
LL
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post #50 of 154
7/8/09 at 10:27am
the problem with threads is they assume humans are linear thinkers. we are not. conversations go all over the place. mr. cass' comments here inspired questions i have posted elsewhere. it's all good. though i concede trying to stay "on topic" in threads is a good thing.
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post #51 of 154
7/8/09 at 10:29am
Quote:
Originally Posted by penngray View Post

Well this thread will probably get back on topic with toddRiffic posts again. Its really about his problem and I still want to understand what Audyssey is doing and Im sure he wants to fix his problem, which is the fact that Audyssey creates a null when calibrating his new sub.


I did like the NXT info, I always wondered why the did their EQing that way.



toddRiffic should use REW or similar along with his SPL meter. SPL meters and warble tones are kind of useless and perhaps misleading.

As far as target curves are concerned, they can't all sound good. A "flat" traget sounds weak in the bass to my ears!
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post #52 of 154
7/8/09 at 10:32am
Quote:
Originally Posted by J_Palmer_Cass View Post

Sealed NHT 2.1 for R & L mains. Kind of an older speaker. Good to about 45 Hz. I run the mains as large and fill in the low end with the subwoofer(s).

roger. i had some superone's, so i know the sound.
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post #53 of 154
7/8/09 at 10:32am
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

the problem with threads is they assume humans are linear thinkers. we are not. conversations go all over the place. mr. cass' comments here inspired questions i have posted elsewhere. it's all good. though i concede trying to stay "on topic" in threads is a good thing.

I think its a great side topic, have we ever had a single topic thread....yeah the ones that no one responses too
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post #54 of 154
7/8/09 at 10:34am
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

toddRiffic should use REW or similar along with his SPL meter. SPL meters and warble tones are kind of useless and perhaps misleading.

As far as target curves are concerned, they can't all sound good. A "flat" traget sounds weak in the bass to my ears!

Agreed and I suggested that in my first post regarding his problem.
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post #55 of 154
7/8/09 at 10:35am
In response to this question in the Audyssey thread...

http://www.avsforum.com/avs-vb/showt...6#post16787886

... The other day I went to Radio Shack and asked if I could purchase several RS SPL meters (both analog and digital) so I could compare them for consistency. They were just fine with that since they have a 30-day return policy.

This is what I found. The analog meters were perfectly consistent amongst themselves, and so were the digital ones. However, there were drastic differences between the analog and digital meters. The digital meters were around 5dB higher in their SPL readings when measuring pink noise for the sub. They also sometimes did this when measuring peak SPL during playback.

Just FYI...
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post #56 of 154
7/8/09 at 10:38am
Clarification...

I used C and slow for both meters. I did not use any of the advanced features of the digital meters (ie MAX, DH, etc.).
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post #57 of 154
7/8/09 at 10:41am
Quote:
Originally Posted by counsil View Post

In response to this question in the Audyssey thread...

http://www.avsforum.com/avs-vb/showt...6#post16787886

... The other day I went to Radio Shack and asked if I could purchase several RS SPL meters (both analog and digital) so I could compare them for consistency. They were just fine with that since they have a 30-day return policy.

This is what I found. The analog meters were perfectly consistent amongst themselves, and so were the digital ones. However, there were drastic differences between the analog and digital meters. The digital meters were around 5dB higher in their SPL readings when measuring pink noise for the sub. They also sometimes did this when measuring peak SPL during playback.

Just FYI...



Did you have the RS Digital SPL meter set to MAX or to AVE for this test?
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post #58 of 154
7/8/09 at 10:44am
william cowan agrees.





"The slight rise in the low end is intentional. The system sounded better that way. When it was truly flat the bass sounded lacking except at very high levels. At normal listening levels of around 90dB the system sounds great when it's balanced like this."
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post #59 of 154
7/8/09 at 10:55am
Quote:
Originally Posted by J_Palmer_Cass View Post

Did you have the RS Digital SPL meter set to MAX or to AVE for this test?

I did not use MAX. If MAX is not used then it averages the readings and refreshes every second (if I remember correctly). The bar below it refreshes 5 times a second (again, if I remember correctly) so it shows lower/higher readings during that 1 second refresh interval, but I didn't look at the bar during my tests.
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post #60 of 154
7/8/09 at 11:05am
Here is a little bit more information for you guys...

I calibrate my Denon 3808 with Audyssey Pro. After calibration my digital RS meter reads 74/75 for the sub. My analog meter reads 69/70.

Since the pro mic is calibrated to be +/- .5dB, I tend to think that a 70dB reading on an analog RS meter is more like 75 instead of the popular 72/73dB reading (in my room anyway). What do you guys think?
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