Gain Structure for Home Theater Discussion Thread

Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Thanks for the reply.

When I measure my AVP subwoofer channel maximum output voltage:

set Left and Right channel to small, set crossover at the highest possible frequency
set the AVP to Stereo mode
adjust the master level of AVP and the level for sub channel to max setting
Play 60 Hz Sine Wave 0 dBFS by Blu-Ray player(oppo 103d)->
send PCM to AVP(EMOTIVA UMC-200)->
measure the sub output voltage

But when I play a blu-ray movie with DTS-HD/Dolby TrueHD, the LFE channel is pre-set to play LFE data 10 dB higher than a main channel (or 10dB higher than the bass from a main channel). I believe this is the reason that channel 4 output of REW is 10dB higher than other channels.

So my question is that, for the maximum subwoofer output voltage when watching movie with DTS-HD/Dolby TrueHD encoded, do we need to add 10db with the subwoofer output measurement?If we need to do this, how to do it? The file is already 0 dBFS.

Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Many thanks for the reply. This totally makes sense to me.

One more question regrading to the center output measurement:

https://drive.google.com/file/d/0B7-tKLkKnSm0VmpXdEEycDVtTnc/view
FL 3.45v
C/Pro Logic II music 3.3v
C/Pro Logic II cinema 5V
C/DTS Neo music 4v
C/DTS Neo cinema 5V

As my test results above, the max center output voltage is different when setting different playback mode. Using Pro Logic II music(3.3v) appears to be closed to FL channel output, but which test results is correct?

Re: Gain Structure for Home Theater: Getting the Most from Pro Audio Equipment in Your System

Hi Wayne,

Great guide!!

If one has an AVR with its built in amp(s) driving their speakers and uses a pro-amp to drive their subs. Would this be the right procedure?

Assumptions:
1. Clean output to reference.
2. You have previously eq'ed your sub to where you like it .ie flat or with house curve etc.


1. Disconnect all speakers
2. Turn avr trim up on all speakers in avr
3. Play 0dbfs tone through all speakers, use "All Channel mode"
4. Crank avr to 0db (or cleanest level before distortion)
..now you have max voltage coming out of the avr's sub pre-out....
5. Turn your subs pro-amp input gain up until the indicator flickers red then goes solid red. (Note this setting, don't ever change it)
6. Rerun your room correction in the avr to set your speaker/sub trims in the avr OR use a spl meter to set your speakers and sub trims in your AVR, using your avr's built in tones so that each speaker and your sub are playing 75db at your listening position.
7.Enjoy

I read your thread on gain structure. Thank you for the information. I have two questions. In both finding out your avr's clean output and setting your amps gains you say to turn your subwoofers trim up all the way. However, you say "Adjust the AVR’s subwoofer trim level to the maximum setting" in one paragraph and "There’s no need to adjust the AVR’s subwoofer trim, as it will be automatically reduced to “clean voltage” when the AVR’s master volume is turned down to the “clean voltage” setting" in the next. This confuses me. Also, after your done setting your gain you say "All that’s left to do at this point is adjust all the AVR's speaker and subwoofer levels using your usual method". I dont have a usual method. I dont have audicy or any room correcting software nor do i want it. I want to set my sub trim to 0. That brings me to my first question. Can i do everything you said exept keep my subwoofer trim at zero? Im not opposed to turning it up to +15 i just have to know what to set it on after i set my gains. 0? Leave it at +15? My second question is similar to my first. When determining your clean ouput voltage you say to turn your xover to its highest setting. Can i do it with it on 80? Again, im not opposed to setting it to its highest setting, however, i would like to at least put that back to 80 when the test is done to protect my speakers. Thanks wayne!!!

Wayne A. Pflughaupt said:

Sure you do. You do use some kind of method to adjust and match the levels of the main speakers, and then adjust the subwoofer to blend, don’t you?

Click to expand...

No i dont. Thats what i thought setting your subwoofer gain was for. You set your amp to match the level of reciever aka other speakers so in a movie somone closing a car door doesnt sound like an explosion. I like leaving everything at 0 and using my volume. Cant hear dialog? Turn it up...explosions too loud? Turn it down. Untill i upgrade my receiver and get some software or understand it better im gonna keep doing it like this.

I would like to go through my gain setting process with you just to make sure i have it right. I get the idea, you want your reciver and amp to clip at the same time.

I will be using a oscope or dd1 to determine my clean output volume(not a speaker like you did). So (acording to you) i turn my sub trim all the way up(+15), turn my xover all the way up, play a test tone and turn up the volume untill it clips, back off untill it doesnt and thats my safe volume?

Then with my sub trim all the way up (still) and oxer all the way up (still), amp gain at 0 i play pink noise at the safe volume and increase gain until light is steady solid. Thats my gain.

Then since i like everything at 0 i would turn my trim back down to 0 and change my xover back to 80 and im done?

The reason why im asking is because when searching how to set your gains most information is about car audio. Its pretty much the same thing exept they recomend leaving everything flat instead of turning trim all the way up and xover.


Since you know i will most likly put the subwoofer trim back to zero should i just set the gains with them set at zero? I want to get this right so i can set it and forget it! Thanks wayne!!!

djcreative1 said:

I would like to go through my gain setting process with you just to make sure i have it right. I get the idea, you want your reciver and amp to clip at the same time.

Click to expand...

Actually, your situation is outside the scope of the article. The article is based on the premise of using outboard pro-audio amplifiers for all channels.

What you’re basically doing is setting your subwoofer level. The common procedure for that, which you’ll find recommended at any home theater forum, is to adjust the subwoofer gain to get an in-room SPL measurement about 10 dB hotter than the main speakers, as a starting point. True, typically the sub in question is active, but it doesn’t change if your sub happens to have an outboard amplifier. An amp is an amp - makes no difference if it’s in or out of the sub box. And a gain control is a gain control.

At the end of the day, all that matters is: are you able to get all the volume you need out of the sub? If the answer is “no,” even with the receiver’s sub output maxed out, and the sub’s gain all the way up, then a new sub system in order. If the answer is “yes,” you’re good to go.

I’m sure you won’t be satisfied with that, so consider this. In your situation, a pro-audio-styled gain structure exercise is irrelevant because your receiver, despite Pioneer’s specs, probably puts out less than an honest 100 watts per channel, while your Crown amp puts out 1200 watts per channel with your 2-ohm load. IOW, by the time the Crown reaches clipping, the Pioneer will be having a melt-down because it can’t keep up.

So, you can do the max-level procedure you mentioned, at +15 or 0 (your choice), but what you’re probably going to find is that the sub ends up exceeding loud compared to the main speakers. Which means you’ll have to back down on the amplifier gain. Which means all you’ve ultimately done is blend the sub with the main speakers, just as I described in the second paragraph above.

Regards,
Wayne