# Sub Volume Control and Fletcher-Munson



## Guest (Dec 28, 2006)

Firstly, let me say that the Home Theater Shack rocks - this forum is excellent, very educational and helpful. A big THANK YOU to the administrators, moderators and Shacksters.

I am in the process of configuring my system and wonder what people have done in the way of volume control for their sub levels. For ref. I am using a BFD1124 / EP2500 amp with the sub output coming from a Yamaha RX-V2600 receiver.

All of us listen to music at different levels and at low levels, a base boost is required. For example, in the “Bass level effect on crossover choice" thread, Brucek shows that he is using a 30 dB elevation for low levels. Basically, if you look at the Fletcher-Munson (FM) (or Robinson-Dadson) curves you can see the base boost that results in a perceived flat response. 

The problem is that as the volume goes up and the base offset is maintained, most of us will hit the wall for our base system way before the higher frequencies (e.g., > 100 Hz). In addition, this may not sound good – too much base.

So it appears that what is needed is separate volume control curves for the subwoofer and mains. At present, I change the gain on my sub amp when I change the main volume. However, this is non-optimal for a number of factors including system damage and WAF. 

My hope is that there is a preamp signal conditioner that can go between the subwoofer output on the receiver and the input on the sub amp (or BFD) that would boost the signal at lower levels and attenuate the signal at higher levels to result in appropriate sub levels across the board. Maybe there are other approaches?

So my question for all the enthusiasts on the forum, what have you done (if anything) to address the sub levels at different system volume levels?

Paul


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hi Paul, 

It sounds like a remote controlled pre-amp is probably what you want. Check my remote control options for your subwoofer thread.


> So my question for all the enthusiasts on the forum, what have you done (if anything) to address the sub levels at different system volume levels?


 This may surprise you, but judging from the deafening silence that thread generated, I get the impression that very few HT enthusiasts use any kind of separate controller for their subs.

Regards,
Wayne


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## Sonnie (Apr 11, 2006)

Hi Paul and thanks for the comp on the Shack... much appreciated.

I'm not sure a variable volume control into the BFD is desirable really. The BFD ideally needs to see more of a constant signal which is why we go through setting the input signal process. Wayne and brucek can explain this better than I can... or you may actually know already and I could be missing your point.

How many volume levels would you generally listen to? A couple, maybe three? If you use the 1124P then you could setup several presets with different bass boost depending on the level you plan on listening to. However, I've measured my response with as much as 20db difference (70db and 90db) in volume and the response was pretty much identical... maybe a db variance here and there, nothing noticeable though.


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## Guest (Dec 29, 2006)

Thanks Wayne, the remote might be a good option – I’ll keep my eye out for one on e-bay.

Sonnie, your suggestion is essentially where I am at now and this is fine if it were just me running the system. My room is fairly large (www.members.cox.net/paulnclark) and open to the rest of the house so I am running the sub system pretty hard already. My concern however is that if I have it set for low level background music using a substantial base boost (e.g., 30 dB) and someone else ends up cranking up the volume, this may do some damage.

From the BFD guide: “Remember not to adjust the volume of your sub via your pre/pro or receiver after you have set the input level... use you sub volume or the volume on the amp connected to your sub, which should be inline after the BFD.” 

I am guessing that most all of us use a receiver and change its volume which in turn affects the level on the pre out to the BFD. Am I missing something?

Paul


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## brucek (Apr 11, 2006)

> I am guessing that most all of us use a receiver and change its volume which in turn affects the level on the pre out to the BFD. Am I missing something?


The point of the Guide where it says, "Remember not to adjust the volume of your sub via your pre/pro or receiver after you have set the input level... ", is in reference to the variable speaker trim level for the subwoofer, and not the master volume. The setting of the trim level is to ensure that when the master volume is at the position which you consider to be the loudest ever likely used, the level to the BFD at that point is trimmed to a digital FS position. We should really change the name of the section on "setting the input level" to "preventing clipping in the BFD". 

I don't know of anyone that goes to the trouble of introducing a loudness control to result in a frequency response that varies with respect to the position of the control. I do know that many of us have a music and HT set of filters in our BFD. I guess that I like the bass a bit louder when I'm listening to movies than when listening to music, so I have two settings. 

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

> My concern however is that if I have it set for low level background music using a substantial base boost (e.g., 30 dB) and someone else ends up cranking up the volume, this may do some damage.


 The Chase RLC-1 connected the way I described in the link, plugged into a switched outlet, would prevent this problem, so long as the system was powered down between the quiet listening session and the loud one.



> From the BFD guide: “Remember not to adjust the volume of your sub via your pre/pro or receiver after you have set the input level... use you sub volume or the volume on the amp connected to your sub, which should be inline after the BFD.”
> 
> I am guessing that most all of us use a receiver and change its volume which in turn affects the level on the pre out to the BFD. Am I missing something?


What brucek said. The BFD is possibly the only pro equalizer on the market that doesn’t have an input level adjustment, so the only way we can adjust the level it gets is from our receivers. Once you get that all set to where the meter is getting an optimal reading, if your sub level is too loud or too soft, you’ll want to adjust at the sub.

As such, any external pre-amp you might use to adjust your sub level, like the Chase, is a gain reduction device. In other words, any setting other than “all the way up” is going to attenuate the incoming signal. So, you’ll want to put the pre-amp between the BFD and the sub, not in front of the BFD. Make sense?

Regards,
Wayne


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