SVS SB-3000 can‘t handle low input signal?

[stesto]

Hi guys,

I would like to know if anyone experienced something similar or has some ideas on the following.

I already talked to the SVS customer support, they had an explanation but I‘m surprised that I seem to be the only one on the planet with that problem, so:
I recently bought an SB-3000 to add some low end to my Klipsch RP-600M, which works fine.
I have the following setup:
Input:

- TV via Toslink​

- Raspberry Pi (for streaming and controlling the minidsp)​

—> miniDSP 2x4HD —>
Output:

- 2 Channels left / right —> Behringer A800 —> RP-600M​

- remaining 2 Channels combined —> SB-3000​

​

So I would say it is rather simple.
To make it short the problem I‘m facing is that I can‘t feed the subwoofer with signals where I have the Master Volume of the minidsp set to less than -50 db to -60 db. Below that „threshold“ is sounds as if the sub is muted.

I mailed that (including some measurements - I had to prove to myself that I wasn't making this up) to the support and after some texting the guy narrowed it down to the „noise gate“ svs includes in their subwoofer dsp.
He said that noise gate shuts the output of the sub off (to prevent the noise floor I assume) at around 3 - 5 mV of signal voltage. I measured that output of the minidsp and it‘s correct. At around -50 to -60 db MV the signal voltage(?) is at said value.

To compensate that I increased the output gain of the sub channel on the minidsp to +6 db, used a Y-splitter cable into the sub (which internally adds 6 db) and lowered the gain on the behringer amp to reduce the speaker volume - as the support suggested.
Because of the lowered speaker volume I had to adjust the in-app subwoofer gain to -38 db. That‘s insane, how could I ever need to increase that gain if I have to limit the volume of the speaker.

And as you can imagine, that of course lowers the potential output SPL of the whole system.
With that compensation I can use the MV down to around -65db before the noise gate kicks in.

The thing that bothers my is that this sub limits my „volume range“ to 50 db.
I can‘t believe that no one else needs to occasionally lower the volume below -50 or -60 db for some listening in the evening or night for example.
Some people now gonna say that I will never listen to music at ±0 db MV, that‘s probably true in everyday life but I hope you get what I mean.

On top I checked this website where you can calculate the resulting voltage of a specified gain - because I thought maybe my minidsp‘s output voltage is too low in general - but the values are almost the same. At 0 db it should be at 1V, but the minidsp is at 2.22V which is even more. And when calculating the voltage of -50 db it yields around 3mV.

I know that I can‘t do anything about It because I can’t disable that noise gate but I just wanted to know if anyone besides me encountered that problem.

Best wishes,
Steve

 

[MrPeabody]

I'm not the right person to be trying to answer this but I've read it several times and I'm not following. You seem to be saying that you had to increase the signal level into the subwoofer so that the subwoofer wouldn't interpret the signal as noise and mute, and that this meant that you need to lower the gain for the A800 (in the MiniDSP I assume). Why? Why would increasing the signal level at the input to the subwoofer, which would obviously make it louder, require you to lower the gain for the A800?

 

[stesto]

Sorry my english is not the best so maybe I couldn't describe it properly.
My problem is the "range" of only -50 db to 0 db MV I can use because of that noise gate. But -50 db is sometimes still too loud when listening in the evening/night. So when I adjust the behringer (it has gain knobs) that it has the "right" volume at -50 db (so that the sub doesn't mute itself) I can't crank it up if I want to. That means when I push the MV to 0 db I know that the speaker and sub could put out more SPL because I "only" increased the volume by 50 db.
I can't achieve whisper quiet volumes while maintaining the ability to push it to disco-like volumes. It's either one or the other.
Before I bought this sub I had another one without noise gate, there I used the System down to -70 to -75db. That meant I was able to increase the volume by +70db instead of my current +50db because it's relative to the whisper qiuet volume I want as a "minimum volume".
I hope that makes any sense...
Btw I know that the Behringer is a powerful amp. Behringer says it puts out 220 Watts per channel (at 8 ohms) and each knob has 21 little dots and I have these currently at the 6th dot if that makes sense. I guess thee 11th dot is where it doesn't add or remove any gain from the signal, but I'm not sure. So I limit amps output for the speakers there.

 

[raindance]

Where a volume control is pointing doesn't necessarily have any bearing on output power, it's all about gain structure.

Why can't you set the sub to "on" instead of "auto"? Or doesn't it have this feature?

 

[stesto]

I have to limit the gain on my speaker, that means I remove some headroom, right?

This "on" or "auto" feature has nothing todo with the noise gate afak. The on/auto setting changes the start behaviour of the sub and its amp. But the noise gate actually disables the output - while playing - when the incoming signal is too low, it doesn't turn the sub off, it kind of mutes it instead

 

[raindance]

Depending on the gain structure of the whole chain, yes you probably remove headroom. The typical rule of thumb, at least in pro audio, is if the power amp volume is less than half for "full volume" in room then chances are the previous stage is running too hot.

Those mini DSP units are a challenge also as they have limited headroom and its hard to keep it in the A/D sweet spot without either clipping or wallowing in the noise.

That noise gate "feature" - is it pre-volume pot at the sub?

 

[MrPeabody]

Sorry my english is not the best so maybe I couldn't describe it properly.
My problem is the "range" of only -50 db to 0 db MV I can use because of that noise gate. But -50 db is sometimes still too loud when listening in the evening/night. So when I adjust the behringer (it has gain knobs) that it has the "right" volume at -50 db (so that the sub doesn't mute itself) I can't crank it up if I want to. That means when I push the MV to 0 db I know that the speaker and sub could put out more SPL because I "only" increased the volume by 50 db.
I can't achieve whisper quiet volumes while maintaining the ability to push it to disco-like volumes. It's either one or the other.
Before I bought this sub I had another one without noise gate, there I used the System down to -70 to -75db. That meant I was able to increase the volume by +70db instead of my current +50db because it's relative to the whisper qiuet volume I want as a "minimum volume".
I hope that makes any sense...
Btw I know that the Behringer is a powerful amp. Behringer says it puts out 220 Watts per channel (at 8 ohms) and each knob has 21 little dots and I have these currently at the 6th dot if that makes sense. I guess thee 11th dot is where it doesn't add or remove any gain from the signal, but I'm not sure. So I limit amps output for the speakers there.

I understand that you ended up with too little dynamic range due to the gain setting for the Behringer. I follow most of what you've said in this post. What I still don't understand is why you had to set the gain for the Behringer so low. This is what I'm confused about. If you had to increase the gain for the sub output from the MiniDSP, this would have made the sub louder, which would seem to mean that you needed to increase the gain for the Behringer to keep the speakers at volume matched to the sub. But this is apparently not what happened, and this is what I don't understand. I realize that it's probably a stupid question because there has to be a reason for it, but nevertheless I don't understand why you had to lower the gain for the Behringer. This seems to be a crucial element to the explanation of why things ended up as they did, and as such it seems that maybe you could provide a more complete explanation of why you lowered the gain for the Behringer.

 

[stesto]

Depending on the gain structure of the whole chain, yes you probably remove headroom. The typical rule of thumb, at least in pro audio, is if the power amp volume is less than half for "full volume" in room then chances are the previous stage is running too hot.

Those mini DSP units are a challenge also as they have limited headroom and its hard to keep it in the A/D sweet spot without either clipping or wallowing in the noise.

That noise gate "feature" - is it pre-volume pot at the sub?

I don't get this rule of thumb, can you explain it in other words? When I have the amp at a volume of 50% or less what does your "full volume" here refer to?

I don't know what a minidsp would do differently compared to a typical av-receiver for example when it comes to the output of a channel (sub in this case). When its master volume is at 0 db it gets me around 2.22V and when I lower the volume the voltage decreases accordingly.

I understand that you ended up with too little dynamic range due to the gain setting for the Behringer. I follow most of what you've said in this post. What I still don't understand is why you had to set the gain for the Behringer so low. This is what I'm confused about. If you had to increase the gain for the sub output from the MiniDSP, this would have made the sub louder, which would seem to mean that you needed to increase the gain for the Behringer to keep the speakers at volume matched to the sub. But this is apparently not what happened, and this is what I don't understand. I realize that it's probably a stupid question because there has to be a reason for it, but nevertheless I don't understand why you had to lower the gain for the Behringer. This seems to be a crucial element to the explanation of why things ended up as they did, and as such it seems that maybe you could provide a more complete explanation of why you lowered the gain for the Behringer.

I actually didn't end up with too little dynamic range because of the behringer, but rather because the subwoofer won't play anything below -50 db. So when I play a sine wave - for testing purposes - with the master volume on the minidsp set between -50 and -60 db (it varies a bit), the sub won't play anything because the signal is too low and it "thinks" it's noise. Like the SVS support said they have their noise gate set to around 3 to 5 milliVolts.
According to this website when you calculate the voltage of a gain loss of -50db it should result in a voltage of round 3mV so that is technically fine I guess.

And the reason is why I had to lower the behringer gain is that this range I have (50db) is not enough to lower the master volume to a level that is quiet enough at -50db. So I lowered the behringer so that -50db is quiet enough but now I obviously lost headroom.
As I said in my initial post I was able to compensate that a bit by increasing the minidsp gain for sub channel by +6db - so that I can lower the MV by another -6 db before it mutes itself. But that on the other hand would obviously lead to clipping when I set the minidsps MV to 0db.
Does that make sense? I probably can't explain it properly.
It's like the sub is meant for people who don't want to listen to very low volumes... or only for listening to low volumes, I don't know.

 

[MrPeabody]

...
And the reason is why I had to lower the behringer gain is that this range I have (50db) is not enough to lower the master volume to a level that is quiet enough at -50db. So I lowered the behringer so that -50db is quiet enough but now I obviously lost headroom.
As I said in my initial post I was able to compensate that a bit by increasing the minidsp gain for sub channel by +6db - so that I can lower the MV by another -6 db before it mutes itself. But that on the other hand would obviously lead to clipping when I set the minidsps MV to 0db.
Does that make sense? I probably can't explain it properly.
It's like the sub is meant for people who don't want to listen to very low volumes... or only for listening to low volumes, I don't know.

I suppose that I would need to play with the MiniDSP to understand what's going on here. I still do not follow the reason for lowering the Behringer gain as much as you did. Oh well.

 

[stesto]

I suppose that I would need to play with the MiniDSP to understand what's going on here. I still do not follow the reason for lowering the Behringer gain as much as you did. Oh well.

Okay... let's talk about SPL (with my little to no knowledge about that)
I imagine that situation like that:

(All the numbers are made up - I can't mesaure the real SPL currently)
I have my Klipsch speaker. The Behringers gain is set to 0 db (I don't know, there are no numbers on that thing)
Let's say at 0 db MV on the minidsp they put out 110 db SPL (maximum) at my listening position. So really loud.
Now if want to decrease the volume and set it to -50 db. In theory that should get me 60 db SPL at my listening position.
For me that's still too loud as a minimum volume. I like it when it's at -70 db MV or something which gets me 40 db SPL. So that should be my minimum volume: 40 db SPL.
But with that sub I can't get below -50 db because of it's noise gate.
So I have to lower the behringer that a MV of -50 db results in a SPL of 40db (my desired minimum volume). That leads to the problem that when I want the full volume (MV set to 0 db) I only get 90 db SPL maximum.

As I said all numbers are made up, but that's going on in my head.

Edit: changed numbers, they were confusing

 

[raindance]

Exactly what I'm wondering!

I understand that you ended up with too little dynamic range due to the gain setting for the Behringer. I follow most of what you've said in this post. What I still don't understand is why you had to set the gain for the Behringer so low. This is what I'm confused about. If you had to increase the gain for the sub output from the MiniDSP, this would have made the sub louder, which would seem to mean that you needed to increase the gain for the Behringer to keep the speakers at volume matched to the sub. But this is apparently not what happened, and this is what I don't understand. I realize that it's probably a stupid question because there has to be a reason for it, but nevertheless I don't understand why you had to lower the gain for the Behringer. This seems to be a crucial element to the explanation of why things ended up as they did, and as such it seems that maybe you could provide a more complete explanation of why you lowered the gain for the Behringer.

 

[raindance]

I don't get this rule of thumb, can you explain it in other words? When I have the amp at a volume of 50% or less what does your "full volume" here refer to?

"full volume" is one of two things (a) as loud as you want it to get in your room OR (b) full amplifier power (normally I wouldn't aim for this).

 

[stesto]

"full volume" is one of two things (a) as loud as you want it to get in your room OR (b) full amplifier power (normally I wouldn't aim for this).

Well at least I want to use the power the speaker can handle. I'm sure I'm nowhere near that power...

 

[Honken]

Not sure how I stumbled upon this old thread, but I am experiencing similiar issues with my PC-2000 subwoofers - but fortunately the fix is simple with them. Essentially, if I put my subs on "automatic on" the signal level needs to be very high for the subs to actually turn on. If I lower the main speakers signal this solves it, but just like you I do not wish to lower my headroom that much.

But, there is something happening to the sound when I'm using the auto on feature - even with the gain lowered on my mains. With music playing, bass simply sounds... off. It is highly noticable with music playing, bass sounds honky and it misses the lower end - bass guitars don't sound like bass guitars at all. I don't think this is the typical audiophile nervosa phenomena. The effect might be exaggerated since I've got a high XO at 160hz (digital, using LFE in on the subs).

I don't see any difference post EQ (which I created with the auto on feature disabled to prevent the subs from going to idle between sweeps) when running sweeps in REW, so I assume it has something to do with the level of the signal. But since disabling the auto on feature works for me (and the subs sound great), I haven't tried to explore this problem further. I have my subs and amps hooked to a "smart" powerstrip , so I've got automatic power control anyway.

I wonder if these subs simply have the same sort of "feature" built in (I don't see it mentioned in them manual), but an earlier version of it. I've been toying with the idea of getting additional, and smaller, subs to fill out some nulls but this thread makes me weary of going with a newer SVS. I've been eyeing the 10D from sigbergaudio anyways.