How To Determine your Receiver's Maximum LFE Output for Gain Structuring - AVS Forum
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post #1 of 27 Old 02-22-2013, 03:53 PM - Thread Starter
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In preparation for my upcoming DIY project, I figured out my receiver's maximum LFE output level the other night. I did it in a way which I haven't seen described on the forums before, so I figured I'd share my process.

The reason for wanting to determine one's maximum LFE output level from their receiver is so that they can set their LFE trim such that the signal can be fed into a pro audio amplifier at the highest level possible, without clipping. Basically, this is a good first step in setting up your "gain structore". However, I also discovered that this can be handy even if you are simply connecting to a commercial subwoofer.

The short version is that I discovered that when fed a -.5dbFS signal, my Onkyo TX-NR809 AV receiver can output a maximum of 4.5V RMS at a LFE trim level of -2db. And as an aside, the -3db point is 3Hz.

Required parts:

AV Receiver
Computer with a "Line In" input (not "Microphone In")
RCA Cable
3 4.7KΩ resistors
Alligator Clips (at least four)
RCA to 3.5mm cable
Digital Multimeter (optional)

Required Software:

Room EQ Wizard
Zelscope (Optional, but highly recommended)
DIY Audio Test DVD

Procedure.

WARNING: YOU WILL BE USING REFERENCE LEVEL TEST TONES AS PART OF THIS PROCEDURE. TURN OFF YOUR AVR AND DISCONNECT ALL SPEAKERS BEFORE PROCEEDING!
Ok, you don't have to disconnect all your speakers. I disconnected mine because 1) the test tone DVD doesn't stop after each tone, and 2) just in case I clicked on a mains test tone rather than an lfe test tone.

Note: This procedure can be performed without Zelscope. But I like to be able to see a waveform, and not just an SPL spike on an RTA.

Connections Setup:

After disconnecting all your speakers, connect an RCA cable to the LFE Output (may be labeled as "Sub Out") on your receiver.

Connect an RCA to 3.5mm cable to the "Line Input" of your computer. Adjust the volume of the line input level to a low level. One click above 0 will work. If the level is too high, the waveform will clip within the sound card, and this could be misinterpreted as the receiver clipping. (Windows 7: Start-->Control Panel-->Sound-->Recording tab-->Select "Line In"-->Click Properties-->Levels tab-->Adjust slider all the way left, and then go one notch right. Other Operating Systems: Good Luck)

Set your Line Input as your default recording device. (Windows 7: Start-->Control Panel-->Sound-->Recording tab-->Select "Line In"-->Set Default)

Connect three 4.7KΩ resistors in series.

Connect an alligator clip from the center conductor of the RCA cable going to the receiver to one end of your resistors.

Connect another alligator clip from the shield side of the RCA cable going to the receiver to the other end of your resistors.

Connect an alligator clip from the shield side of the RCA cable going to your computer to the end of the resistors connected to the shield side of the cable going to your receiver.

Connect an alligator clip from the center conductor of the RCA cable going to your computer to the other side of the resister connected to the shield wires.

What you end up with should look like this:



Note: The reason we are doing this with resistors is because if you connect your AVR straight into your line input on your sound card, you may clip the input of your sound card. This could be falsely interpreted as your receiver clipping. What we are doing here is setting up a simple voltage divider so that we don't clip the signal coming into our sound card.

Software Setup:

Room EQ Wizard:

Once Room EQ Wizard has started, go to Preferences-->Preferences.

In the drop down menu under "Input Device and Input" select "Line In"

In the drop down menu under "Input Channel", select right or left, depending on which RCA plug you have connected to the resistor network. (Red = Right, White = Left)

Close the preferences window.

Click the "RTA" button.

Click the red circle near the top right corner of the window that pops up.

Now you should see a real-time spectrum from your Line In.

Zelscope:

Click the Play button located just underneath "File" in the top left corner of the window.

Click the Ch1 and Ch2 buttons to turn on both channels. You can turn off the unused channel once you determine which channel corresponds to the input you are using.

V/Div you can adjust later. However, note that any voltage reading you get from the scope is NOT VALID unless you first calibrate the software with a sine wave of a known voltage level. For our purposes here, we don't need to know what the voltage level is.

Under the "Horizontal" section, set "MS/DIV" to 2.

After having disconnected your speakers, turn your AV Receiver on.

Now, start the Audio test DVD, navigate to "Extras", and select one of the sweeps in the LFE section. If everything is set up properly, you should see a sine wave appear in Zelscope. Adjust V/Div to a comfortable viewing level, and turn off the un-used channel.



The Actual Test:

Now, turn your receiver up to 0. (assuming your volume display is set to db. If it is, as you turn up the volume, the numbers should go down) As you do this, the waveform in Zelscope should get bigger.

If the waveform you are getting at this point is not clipped, go into your AV Receiver's setup, and turn the LFE trim setting up and re-check until you see clipping at the output.

If the waveform you are getting at this point is clipped, adjust the "Line In" volume setting in your computer. If the clipped waveform displayed on the scope gets bigger, it is your receiver clipping. If the clipped waveform gets even more clipped, your sound card is clipping. Turn down the level of your "Line In".



Now, using the -.5db sweeps in the Audio Test DVD, you can continue adjusting your receiver's LFE output trim until it is just below clipping. On my receiver, that level is -2db.

Optionally, at this point you can hook a DMM across all three resistors. This will give you your receiver's maximum output level before clipping in volts RMS. This reading will help you determine whether or not your receiver can drive a pro audio amp. My amp outputs a clean 0db signal at 4.5V RMS. It clips at 4.8V RMS.

At this point, you can turn to the Room EQ Wizard RTA window. To verify you are not clipping, click the "THD" button. Your THD should be under 1% with no clipping. With clipping, it will be more than 1%.

If you know your way around REW, you can calibrate it's SPL meter to the 95db pink noise on the audio test DVD. Once you do this, the RTA should read just under 115db (ideally 114.5db) when you run the -.5db test tones.

Having accomplished this, you can now play the individual 1Hz to 20Hz tones and plot out your receiver's low frequency response.

NOTE: Ideally, this would give you an accurate reading. However, your sound card will also have a low frequency rolloff. In reality, your receiver's actual low frequency rolloff will likely be a little less steep than what you measure using this method. In order to get an accurate reading of your receiver's low frequency rolloff, you would need to measure using an actual oscilloscope.

Here is the plot I got for my receiver:



Now that you have this information, what do you do with it? For one, decide how much headroom you want. Ideally, your LFE output will never output anything greater than a 0dbFS signal. However, it is possible to see a greater than 0dbFS signal if a similar signal appears on the other channels and gets re-routed to the LFE channel by way of the receiver's bass management. And so if you want an extra margin for safety, you could set your receiver's LFE trim to 3db below the level at which you get clipping with a 0dbFS signal. However, I have heard numbers as high as +9db FS (124db SPL) thrown around as theoretically possible. (0dbFS signal at the same frequency, in phase, to all 7 channels at the same time in a 7.1 soundtrack). And so how much headroom you want to leave is up to you.

Now you have determined what level to set your AVR to when setting up your gain structure.

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post #2 of 27 Old 02-22-2013, 04:11 PM
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That's basically what I described a week ago, except with a stepped attenuator instead of the 3 series resistors.
Yours has pics which will make it easier for many others to follow.
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post #3 of 27 Old 02-22-2013, 07:54 PM
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Ok I'll say it then......Badass Sir biggrin.gif

Voltage divider and all, with PICS. Sweet.
Sure the DD-1 detector we use is "easier" but I wouldn't mind seeing with the software. Never heard of Zelscope, but already like it for this application.

Thanks!

"I should really see what dB levels I'm pushing. Long as it can't foam my beer during a movie we are ok "
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post #4 of 27 Old 02-23-2013, 03:53 AM
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Dan,

Great write up with pictures and screen shots to follow. I know A9X has described this before for folks also who do not use oscopes (but I do like seeing pictures:))

My only question is why you did not start out with the sub trim at its maximum and then increase the master volume until the onset of clipping (as is done in pretty much every article on setting up the gain structure I could find)? Thanks.

James
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post #5 of 27 Old 02-23-2013, 04:03 AM
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What is a Zelscope?

How are the resisters connected in series?

Is just one RCA to 3.5mm cable needed? Also, do you butcher this cable in order to hook the resisters to it?

Thanks for the very informative post, Dan LW.
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post #6 of 27 Old 02-23-2013, 09:14 AM
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Excellent writeup! Thanks!

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post #7 of 27 Old 02-23-2013, 10:48 AM
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nice writeup.

i like how everything is very carefully monitored and precise to the 0.5db until the last step where "add 3-9db depending headroom" is suggested. it is right. it is just kind of funny. however, that does present another challenge. 9db is eight times the signal level. that takes a 4.8 volt output signal down to 0.6 volts, which isn't enough to hit full power on many pro amps. yes or no?

edit: 7 channels of 105db redirected coherent bass = 105db + 20*log(7)db = 105db + 16.9db = 121.9db of redirected bass. 121.9db + 115db = 20*log(10^(115db/20)+10^(121.9db/20)) = 125.14db. so if you want to be absolutely sure never to clip allow for 10.14db headroom. :-)~

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post #8 of 27 Old 02-23-2013, 05:22 PM
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Nice tutorial!

I just made 4 files that play 10, 20, 40, and 60 Hz sine waves for 30 seconds each to all 5.1 speakers. They are played at full volume and encoded into ac3/ dolby digital format. I believe that these files should produce the loudest possible signal that any source can play with respect to redirected bass. LTD did the problem math to figure out how much to adjust for redirected bass. I like using heuristics and just trying it out. I'm going to try to attach one or more to this post.

Nathan 6ch_20.zip 2123k .zip file 6ch_40.zip 2074k .zip file
Attached Files
File Type: zip 6ch_20.zip (2.07 MB, 5 views)
File Type: zip 6ch_40.zip (2.03 MB, 4 views)
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post #9 of 27 Old 02-23-2013, 05:29 PM
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Here are the 10hz and 60hz test tracks.

I forgot to say that I think you can use these test tracks to check the increase in redirected bass. Measure the LFE level with redirect bass on and off and that should give you the increase.
6ch_10.zip 2118k .zip file 6ch_60.zip 2030k .zip file
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File Type: zip 6ch_10.zip (2.07 MB, 3 views)
File Type: zip 6ch_60.zip (1.98 MB, 5 views)
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post #10 of 27 Old 02-23-2013, 08:37 PM
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Hmmm. Still like the SMD DD-1, and yes it works very easy for home audio as well as car audio. It's quicker and just as accurate. Simple enough as using a muti-meter.

example
40Hz at -0dB track
Yammy V867 sub out set at +3 (where it's usually kept) which is set for max volume determined for before clipping the BFD in our chain
measured where max volume set to just under distortion detected by DD-1
verified; measured with fluke77 and it's 7.31Vac RMS

Checked the main channels (1kHz at -0dB) and depending on where your individual channels are set (+/- /ch) you'll be limited to whats set hottest. If all the chain is the same ie same amps same speakers everything can be extrapolated. The yammy V867 channels measured at 4.5Vac RMS before distortion.

==================
Can then use the DD-1 to set your amp gains, and or also use your multi-meter to balance outputs desired Vac. And just in case your running a lab clone note the DD-1(125V) or HV(200V) models are limited in voltage for large amp measuring depending on load.

voltage = sq rt ( P x R)
lab clone
14000w x 4ohms
236v....hmm nope

Supposedly Meade can mod the HV model for higher voltages.

"I should really see what dB levels I'm pushing. Long as it can't foam my beer during a movie we are ok "
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post #11 of 27 Old 02-24-2013, 07:30 AM - Thread Starter
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Quote:
Originally Posted by exojam View Post

My only question is why you did not start out with the sub trim at its maximum and then increase the master volume until the onset of clipping (as is done in pretty much every article on setting up the gain structure I could find)? Thanks.

I suppose that would have been quicker, in that I would simply subtract the master volume value at the onset of clipping, and trim the channel down that much. Whereas I did the reverse and found the trim level by trial and error. So that method would be quicker, but both get you to the same destination.
Quote:
Originally Posted by Martycool007 View Post

What is a Zelscope?

How are the resisters connected in series?

Is just one RCA to 3.5mm cable needed? Also, do you butcher this cable in order to hook the resisters to it?

Zelscope is a free (for a 14-day trial, $10 to buy) program which uses the inputs of your sound card as the inputs to a software oscilloscope. Basically, it's a software oscilloscope.

I had raw resistors in my electronics toolbox, so I simply twisted the leads together. It wasn't until after I did this that I found my breadboard.

Just one RCA to 3.5mm is required. I didn't butcher the ends of any cables. I just used some alligator clip leads to connect the plugs to the resistor network.
Quote:
Originally Posted by LTD02 View Post

nice writeup.

i like how everything is very carefully monitored and precise to the 0.5db until the last step where "add 3-9db depending headroom" is suggested. it is right. it is just kind of funny. however, that does present another challenge. 9db is eight times the signal level. that takes a 4.8 volt output signal down to 0.6 volts, which isn't enough to hit full power on many pro amps. yes or no?

edit: 7 channels of 105db redirected coherent bass = 105db + 20*log(7)db = 105db + 16.9db = 121.9db of redirected bass. 121.9db + 115db = 20*log(10^(115db/20)+10^(121.9db/20)) = 125.14db. so if you want to be absolutely sure never to clip allow for 10.14db headroom. :-)~

Yes, in an ideal world we would just set the trim to just below clipping. That brings up an interesting question. How hard can a sub be clipped without damaging the woofer? Of course, the answer is it depends... on how much power the amp has, on whether or not the amp has protection against a clipped input, on how much power the speaker can handle. I'll have to research these when I determine how to set up my gain structure. If my amp will protect against clipped inputs, then I'd just prefer to set my receiver trim to just below clipping a 0db FS signal, and if a poorly mixed movie comes through my system, I'll just accept that I won't hear >115db of bass.

Anybody have an answer to this? I know clipping can kill tweeters, but how about woofers?

Thanks for spelling out the theoretical maximum! I didn't know the exact formula. I just added up the channels. +3db for the first channel, +3db for the next two, and +3db for the last four. Either way you slice it, 10db of headroom is a lot of headroom. Building a subwoofer system capable of 125db would be really expensive. My two LLTs I plan to build with SI HT18 drivers should easily achieve 115db. But I'd have to build four or more to achieve 125db!
Quote:
Originally Posted by NathanJ View Post

Nice tutorial!

I just made 4 files that play 10, 20, 40, and 60 Hz sine waves for 30 seconds each to all 5.1 speakers.

Wow, that's scary! The worst case scenario (shy of 7.1) available for download. I may have to try that out. Looks like I get to tweak around some more.

Still confused? Read "
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post #12 of 27 Old 02-24-2013, 10:46 AM
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I have been using the behringer 31 band eq's for my subs. It has a led meter that you can see the signal level , I set my lfe's so that at reference they just touch the orange lights. With the denon 4311, I have to back the gain on the eq down 3 clicks, then set sub level +10 . The 4311 puts out a lot of signal .


http://www.behringer.com/EN/Products/FBQ3102.aspx
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post #13 of 27 Old 02-24-2013, 08:38 PM
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Dan,

I've been trying to understand how audyssey plays into the whole gain structure setup thing. I cannot say I made much progress. Perhaps you can help.

When you recommend to set trims on LFE just below the clipping level, what exactly do you mean? Do you forego Adyssey level calibration? If so, do you only adjust subwoofer channel or trims for oher channles are also changed to maintain the balance? and , somewhat related, why do you find it important to set the trim level close to clipping to begin with?

The reason I am asking is that, AFAIK , there is a good chance AVRs do not have to produce LFE signal close to max clean output for ref level playback. How strong the signal is would depend on SPL reading during the calibration which would be a function of drivers sesnsitivity, power and distance to the LP. All those multi driver high gain setups in small rooms would not need much input voltage, especially if there is little LF boost by Audyssey. Am I making any sense?
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post #14 of 27 Old 02-24-2013, 08:51 PM
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Quote:
Originally Posted by Dezmond View Post

I have been using the behringer 31 band eq's for my subs. It has a led meter that you can see the signal level , I set my lfe's so that at reference they just touch the orange lights. With the denon 4311, I have to back the gain on the eq down 3 clicks, then set sub level +10 . The 4311 puts out a lot of signal .


http://www.behringer.com/EN/Products/FBQ3102.aspx
how precise the HPF controls are on these? Is it possible to reliably set the filter to 13Hz for example?
Thank you
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post #15 of 27 Old 02-24-2013, 08:53 PM
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Quote:
Originally Posted by zheka View Post

Dan,

I've been trying to understand how audyssey plays into the whole gain structure setup thing. I cannot say I made much progress. Perhaps you can help.

When you recommend to set trims on LFE just below the clipping level, what exactly do you mean? Do you forego Adyssey level calibration? If so, do you only adjust subwoofer channel or trims for oher channles are also changed to maintain the balance? and , somewhat related, why do you find it important to set the trim level close to clipping to begin with?

The reason I am asking is that, AFAIK , there is a good chance AVRs do not have to produce LFE signal close to max clean output for ref level playback. How strong the signal is would depend on SPL reading during the calibration which would be a function of drivers sesnsitivity, power and distance to the LP. All those multi driver high gain setups in small rooms would not need much input voltage, especially if there is little LF boost by Audyssey. Am I making any sense?

I still stand by my opinion that most modern day receivers are capable of enough output voltage that this is becoming irrelevant. In days past when a receiver was capable of outputting a mere 1 or 2 volts at best, setting LFE at maximum clip level helped to maximize the signal input to the pro amps. When todays receivers are putting out 5+ volts, there is really no reason to be cranking sub outs to pre clip levels.

The old wives tail of maxing out output signals is a thing of the past. Initially, when the BFD was really popular, it was advised to send the hottest signal into the BFD (just before clipping), to maximize the signal. We were taught that the hotter the signal, the cleaner it was. This has since been proven as inaccurate. Now there are certain instances where SN ratios will play a factor, but these are rare.

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post #16 of 27 Old 02-24-2013, 09:04 PM
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Quote:
Originally Posted by bass addict View Post

I still stand by my opinion that most modern day receivers are capable of enough output voltage that this is becoming irrelevant. In days past when a receiver was capable of outputting a mere 1 or 2 volts at best, setting LFE at maximum clip level helped to maximize the signal input to the pro amps. When todays receivers are putting out 5+ volts, there is really no reason to be cranking sub outs to pre clip levels.

The old wives tail of maxing out output signals is a thing of the past. Initially, when the BFD was really popular, it was advised to send the hottest signal into the BFD (just before clipping), to maximize the signal. We were taught that the hotter the signal, the cleaner it was. This has since been proven as inaccurate. Now there are certain instances where SN ratios will play a factor, but these are rare.

I find your reasoning very convincing.
I think it is good to know what the max clean voltage is so that it can be compared with voltage measured at the actual highest Audyssey calibrated output level ( thank you for the test tones, NathanJ).
But it is not clear to me why and how the max clean output level should be used for setting the gain structure around, given that it may be well in excess of what's needed for ref. level playback.
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post #17 of 27 Old 02-25-2013, 05:33 AM
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Quote:
Originally Posted by zheka View Post

how precise the HPF controls are on these? Is it possible to reliably set the filter to 13Hz for example?
Thank you

Its adjustable in 5hz incriments from 10hz up. So you would have to use 15hz, they call it a low cut filter .
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post #18 of 27 Old 02-25-2013, 06:50 AM
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Quote:
Originally Posted by Dezmond View Post

Its adjustable in 5hz incriments from 10hz up. So you would have to use 15hz, they call it a low cut filter .
'

OIC. The Low Cut control is stepped, not continues. The manual states that the filter is bypassed when control is in the 10Hz position. Would this mean that the lowest usable setting is 15Hz?
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post #19 of 27 Old 02-25-2013, 10:20 AM - Thread Starter
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Quote:
Originally Posted by zheka View Post

Dan,

I've been trying to understand how audyssey plays into the whole gain structure setup thing. I cannot say I made much progress. Perhaps you can help.

When you recommend to set trims on LFE just below the clipping level, what exactly do you mean? Do you forego Adyssey level calibration? If so, do you only adjust subwoofer channel or trims for oher channles are also changed to maintain the balance? and , somewhat related, why do you find it important to set the trim level close to clipping to begin with?

The reason I am asking is that, AFAIK , there is a good chance AVRs do not have to produce LFE signal close to max clean output for ref level playback. How strong the signal is would depend on SPL reading during the calibration which would be a function of drivers sesnsitivity, power and distance to the LP. All those multi driver high gain setups in small rooms would not need much input voltage, especially if there is little LF boost by Audyssey. Am I making any sense?

Most of what I learned about gain structuring is from this article:

Gain Structure for Home Theater

I used Audyssey to set the distances and levels of the individual speakers. If you want to use the level Audyssey sets up for you, that can easily be achieved by running Audyssey, and then using a test tone to determine the level it set your subwoofer at. Next, see where Audyssey set your trim at. If it set it at a level below your maximum clip level, you are probably good and can leave it as is. If it set it at a level above your maximum clip level, adjust the trim down to the level you determined, run the test tone again, and turn up your sub amplifier to achieve the same level which Audyssey determined. (In this case, you're using the subwoofer amp instead of the receiver LFE trim to achieve the desired level).

Also, it is important to know the clip level in case you are in a situation like mine. As it turns out, Audyssey set my trim to +2.5db. But my clip level (using a -.5db FS signal) is -2db! So if I left my receiver at the level Audyssey determined, I would actually never achieve 115db peaks, but would rather achieve 110.5db peaks, at which point I would be sending a clipped signal to my subwoofer! This makes me want to believe there was something wrong with my methodology, and I may indeed try this again to see if I get the same results.

On a sidenote, I set my receiver to "pure audio" mode in order to get a flat non-EQed response. I'll have to try this again with DEQ enabled to see if there are points where my signal is being driven to clipping by the DEQ.

As far as gain structuring, as I understand it, the theory is that by sending a signal just below clipping (at 0db FS), you are maximizing the dynamic range available to you. The article linked above explains this with pictures. Basically, if you send a signal to a pro audio amp which is lower than what your receiver can put out, you then have to turn the amp up more in order to achieve the desired SPL. This raises the noise floor of the amp, which in turn decreases dynamic range. However, as I understand, noise is generally above subwoofer frequencies, so noise floor is not a huge issue when gain structuring for a subwoofer.

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post #20 of 27 Old 02-25-2013, 11:56 AM
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As far as gain structuring, as I understand it, the theory is that by sending a signal just below clipping (at 0db FS), you are maximizing the dynamic range available to you. The article linked above explains this with pictures. Basically, if you send a signal to a pro audio amp which is lower than what your receiver can put out, you then have to turn the amp up more in order to achieve the desired SPL. This raises the noise floor of the amp, which in turn decreases dynamic range. However, as I understand, noise is generally above subwoofer frequencies, so noise floor is not a huge issue when gain structuring for a subwoofer.

I'd agree with this, but the same has also been said about the sub out gains.

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post #21 of 27 Old 02-25-2013, 12:21 PM
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Originally Posted by DanLW View Post


I used Audyssey to set the distances and levels of the individual speakers. If you want to use the level Audyssey sets up for you, that can easily be achieved by running Audyssey, and then using a test tone to determine the level it set your subwoofer at. Next, see where Audyssey set your trim at. If it set it at a level below your maximum clip level, you are probably good and can leave it as is. If it set it at a level above your maximum clip level, adjust the trim down to the level you determined, run the test tone again, and turn up your sub amplifier to achieve the same level which Audyssey determined. (In this case, you're using the subwoofer amp instead of the receiver LFE trim to achieve the desired level).

Got it!

You only recommend to adjust the trim down and only if it is over the clipping level. If it has to be adjusted, you suggest to increase the gain on the amp to compensate for the difference. This makes sense now smile.gif Thank you.

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On a sidenote, I set my receiver to "pure audio" mode in order to get a flat non-EQed response. I'll have to try this again with DEQ enabled to see if there are points where my signal is being driven to clipping by the DEQ.

It would be interesting to see what you find out. AFAIK, the closer AVR to ref. level the smaller the DEQ boost, with DEQ fully disabled at ref level. So in theory you won't see the effect of DEQ if you measure at 0db setting on the MVC.
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With the structuring, are we only worried if the signal is clipped going into the amp? There is other methods to determine max wattage going to each speaker/sub. Having access to a Input Isolated O-Scope and hook directly to the LFE output I found the Sony STR-DG810 did not clip whatsoever at max volume or max SW setting. My main concern was the unbalanced output being able to drive the pro amp.
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post #23 of 27 Old 02-25-2013, 05:10 PM
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Terrific write-up, great diagrams, esp. the sesame-street step by step that I can follow very well! Had no Idea Zelscope existed, will likely be getting a copy myself.

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post #24 of 27 Old 02-25-2013, 05:13 PM
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Quote:
Originally Posted by Kiel'thalin View Post

Having access to a Input Isolated O-Scope and hook directly to the LFE output I found the Sony STR-DG810 did not clip whatsoever at max volume or max SW setting. My main concern was the unbalanced output being able to drive the pro amp.
I'm not getting what your concern is then; your AVR pre outs can drive to max settings with no significant distortion. Is that enough level to drive your pro amp or not? That info will be in the amp specs. You'll need twice the level into the amp to get full output if driving it unbalanced.
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post #25 of 27 Old 02-25-2013, 05:52 PM
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Originally Posted by A9X-308 View Post

I'm not getting what your concern is then; your AVR pre outs can drive to max settings with no significant distortion. Is that enough level to drive your pro amp or not? That info will be in the amp specs. You'll need twice the level into the amp to get full output if driving it unbalanced.

Right now it is enough to drive my current sub to max. I am afraid it won't be enough to drive the additional subs I am putting together now. The concern for me is spending the money on a ART cleanbox or not. Trying to sack any extra money away for a nice processor for the amp I am building for the mains.
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post #26 of 27 Old 02-25-2013, 06:05 PM
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Quote:
Originally Posted by Kiel'thalin View Post

Right now it is enough to drive my current sub to max. I am afraid it won't be enough to drive the additional subs I am putting together now. The concern for me is spending the money on a ART cleanbox or not. Trying to sack any extra money away for a nice processor for the amp I am building for the mains.
Are you planning on adding additional power amps (driving more subs) or adding additional subs on to the existing amp(s)?
Paralleling additional amps will give you the same voltage level at the amp inputs as they are generally 10kohm or higher. Adding extra subs to the existing amps will depend upon what and how you're implementing them, but if the same as what you already have, you'll need no more gain.
Certainly don't spend any money on a cleanbox or similar until it has been definitely determined you need it.
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post #27 of 27 Old 02-25-2013, 09:46 PM - Thread Starter
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Quote:
Originally Posted by A9X-308 View Post

Are you planning on adding additional power amps (driving more subs) or adding additional subs on to the existing amp(s)?
Paralleling additional amps will give you the same voltage level at the amp inputs as they are generally 10kohm or higher. Adding extra subs to the existing amps will depend upon what and how you're implementing them, but if the same as what you already have, you'll need no more gain.
Certainly don't spend any money on a cleanbox or similar until it has been definitely determined you need it.

Agreed, it normally isn't a problem to drive multiple amps off one output since the input impedance is nominally 10Kohms. Even if you were to drive 10 amps off one output, the impedance seen is still 1K, which shouldn't load down the circuit that much.

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