Gain control affecting dynamics

V

Vaughan Odendaa

Senior Audioholic
Hi there,

For a long time now my system has been crippled because of poor low frequency dynamics. This shouldn't be the case, after all, I own dual MFW-15 subwoofers.

I have always calibrated my system flat with my main speakers, 73-74 dB's for the subwoofers (70 dB's per subwoofer) and yet tactile sensations were almost nonexistent even as I raised the MV. Problem was, the more I raised the MV, the more compression set in, so not only could I not sense pressure sensations but there was a major stumbling block; compression and lots of it.

I never understood how this could be. I mean I have EQ'ed my system flat, I've cut several peaks which should mean that I have more available headroom to deal with dynamic loads. So if I increase my master volume the bass levels should raise accordingly. Not so.

If I increased my subwoofer level (it was -7 to 0) the bass levels got louder but the peaks got crippled again. The 15" cones were hardly moving at all. Increasing my MV and increasing the subwoofer level could not get the cones to move much.

This worried me. Until now. My gain levels on both subwoofers were extremely low but this was required to get the 70 dB reading out of both subwoofers. So I increased my gain control to 40% and dialed back my subwoofer level to read the same SPL output and the differences were amazing. Now the cones are moving !

There is now a tactile feeling that I have that is beyond words; I never felt this before. I disconnected the one subwoofer and I simply increased the gain control. Now we're talking.

And it's not as if my total SPL level was any higher during calibration; it was exactly the same level ! The only change was that I increased my gain control and reduced my subwoofer level. I can now perceive the pressure changing in my room on several bassy sequences and the compression has all but gone. As my MV is increased so does the bass levels. This did not happen before.

I tried Transformers where ironhide does the famous flip scene and I couldn't get over how deep and visceral the bass was. It swept over me, through me and pummeled me. I can't believe that it's taken me so long to figure out that my gain control settings were set too low and thus severely crippling my dynamics.

But how ? And why would it make any difference at all ? I mean, the gain control and subwoofer level effectively form the volume control of the subwoofer so why would it matter in which order I control the gain or sub level ? As long as it reaches the goal SPL output at the seats that is all that matters, right ?

Well, I have no idea what just happened and I invite anyone to please explain what happened. All I know is that I am going to be watching my entire collection again because as far as I am concerned, this is the first time I'm exploiting my subwoofers capabilities.

I'm very happy at the moment. If anyone can shed light on what happened in my system I would very much appreciate it.

Regards,
 
J

jamie2112

Banned
This sounds like an out of phase sub to me.... can you reverse the polarity of one of your subs? Just a thought....
 
AcuDefTechGuy

AcuDefTechGuy

Audioholic Jedi
I told you already a long time ago.:D

Turn off all the EQs and just set every level to Zero.:D

Sometimes More is actually Less.:D

I know some people love EQs and Tones, but the fact remains that when we use EQs and Tones, measureable distortion, noise, crosstalk, and frequency response linearity are all adversely affected. Some say that these effects are inaudible. But I have never liked the sound of any EQs and Tones.

Like they say, how the specs look on "paper" is one thing. But how it actually sounds to our ears is a lot more important. Trust your ears.
 
V

Vaughan Odendaa

Senior Audioholic
jamie2112 said:
This sounds like an out of phase sub to me.... can you reverse the polarity of one of your subs? Just a thought....
No, nothing was out of phase. Believe me, I would have tested for this in the beginning stages.

Regards,
 
V

Vaughan Odendaa

Senior Audioholic
AcuDefTechGuy's said:
Turn off all the EQs and just set every level to Zero.
But I haven't done this. The issue wasn't the EQ. At all.

I know some people love EQs and Tones, but the fact remains that when we use EQs and Tones, measureable distortion, noise, crosstalk, and frequency response linearity are all adversely affected.
I don't think you understand. Increasing the gain levels on the subwoofer itself all of sudden gave me my dynamics back. That has nothing to do with any EQ device. This is what I don't understand.

Regards,
 
V

Vaughan Odendaa

Senior Audioholic
I argued a while back the merits of calibrating flat with the main speakers and I expressed my views on that issue and how I hated the fact that infrasonics were limited, blah, blah.

But this entire time there was another issue that creeped in that gave me this impression, not just that the levels were set accurately. No, I watched Cloverfield and I thought my house was going to cave in because the pressure sensations were huge.

After watching several bassy films, my impressions have altogether changed. Calibrating flat is not bad at all. It's great, in fact. However, if I calibrate flat with the main speakers and EQ flat then it stands to reason that I should be able to increase my MV and gain much needed headroom in the process.

With subwoofers as powerful as mine and still EQ'ing and calibrating flat, I should have enormous headroom capabilities and yet I had reached a compression state early on and I couldn't understand why. No one could, not Mark Seaton, not anyone.

And yet today is the day that all those issues have been solved. But I still don't understand the how and why. I fail to see how me changing the order (upping gain levels and reducing subwoofer levels in AVR) could have affected things this much.

Because the differences are astounding, so much so that I want to watch all my films again.

Regards,
 
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V

Vaughan Odendaa

Senior Audioholic
AcuDefTechGuy's said:
So is your subwoofer level on your EQ/Tone set to Zero and you are now just using the gain control on the subwoofer itself?
No, my subwoofer level is basically set to -9 now. My SMS-1 is set to 7 and my subwoofer gain control has been set to 40%. Before it was set to slightly below 20% because at the time that was all that was needed for me to reach a 73-74 dB reading. My subwoofer levels, of course, were higher than -9.

--Regards,
 
V

Vaughan Odendaa

Senior Audioholic
Thinking back on this issue it actually makes sense (I think).

If you have low voltage from the reciever and the gain on the MFW is set low this could produce the low volumes that I experienced. But the overall SPL level was exactly the same. And increasing the subwoofer level to compensate for the low gain structure doesn't actually help in this regard.

So this would only affect peak output loads ? I mean I never dabbled to determine at which point the gain control had this compression effect but I did note that turning the gain up from less than 20% to 40% made a massive jump on peak output levels.

Regards,
 
Adam

Adam

Audioholic Jedi
You have posed a very interesting question, Vaughan. I'm hoping that some of the people here can give some good answers on this.
 
Hi Ho

Hi Ho

Audioholic Samurai
The problem you describe is all about gain staging. On a sound board there is a gain control before the master fader. If the gain is set too low then you're not going to get much volume out of the master fader into the main mix. Also, if the amplifier is set too low then, no matter how much gain you apply, you won't get the volume you're looking for and compression sets in.

The same goes for the subs. When I setup a receiver I usually set the subwoofer level in the receiver at zero and the gain on the sub about half way up and go from there adjusting the level at the sub. The auto setup function in most receivers does a great job of setting the speaker levels but they aren't great at setting subs and usually turn the level in the receiver all the way down.
 
V

Vaughan Odendaa

Senior Audioholic
In some cases it seems like the only way to get a flat calibration (not that it's a prerequisite or anything) is to reduce the sub level and gain level to very low levels.

Some receivers send out a high voltage on their pre-out stage. This problem is compounded when you have more than two subwoofers. The SMS-1 gives me additional control to further decrease the level if need be but I'm thinking of selling it and buying the anti-mode.

Regards,
 
V

Vaughan Odendaa

Senior Audioholic
Hi Ho said:
The problem you describe is all about gain staging. On a sound board there is a gain control before the master fader. If the gain is set too low then you're not going to get much volume out of the master fader into the main mix. Also, if the amplifier is set too low then, no matter how much gain you apply, you won't get the volume you're looking for and compression sets in.
Which explains it perfectly. Would I expect to see any additional gains increasing my gain control past 40% and recalibrating flat ? I don't see that I will though. Thanks for your explanation !

Regards,
 
Adam

Adam

Audioholic Jedi
The main reason that this topic interests me so much is that it seems to lead towards a recommended way of setting up systems that is opposite of what I've read here and done myself. Namely, the approach of fixing issues with some auto-on sensors in subs by turning the receiver sub output up (in order to stay above the threshold of the auto-on sensor) and turning the gain down on the subwoofer amp (to keep the sub level the same as before).
 
V

Vaughan Odendaa

Senior Audioholic
I'm hoping we can talk more about this topic as I'm sure others would benefit.

Regards,
 
MidnightSensi

MidnightSensi

Audioholic Samurai
Gain doesn't add, it multiplies.

You can still reach full power of the amplifier with a low gain setting, but the source input needs to be a lot hotter.

You want to find a balance between clipping your source, and setting your gain to a level that keeps the noise floor low.
 
V

Vaughan Odendaa

Senior Audioholic
MidnightSensi said:
You can still reach full power of the amplifier with a low gain setting, but the source input needs to be a lot hotter.
When you say "source input" do you mean the subwoofer level control in the AVR ? Because I tried increasing the subwoofer level and it made no difference; dynamic peaks were still crushed at high levels.
 
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