Amplifier Question

[Kele]

I have an amp running two subwoofers from two of its five channels. The amps channels are 100 watts each (damping factor 1000 per channel). Both formally self-powered subs' panel amps are shot so I am running them as dumb sealed enclosure speakers. My preamp is acting as the low-pass filter to the subs. I have no idea what the sensitivity rating is of each sub speaker, but they are both 8ohm. It sounds great... maybe as good as their original amps.

I have two ways of adjusting the volume for the subs: 1) Via the Pre-amp's calibration level for the Sub+L/R channel, and 2) via potentiometer pots on each channel at the (separates) amplifier. The amp's instruction manual states the "0" position (no attenuation) is normal but provides level reduction pots just incase.

My question has do with wanting to make life as easy as possible for the amplifier driving two subs (+ a center and two rears). Currently I have reduced the preamp's output for the subs by minus 8db, and have the amp volume pots at max (one pot about 20% less to balance that sub's sound in the room). Would it be more beneficial for the amp to work less hard by boosting the sub signal out of the preamp and use the amp's pots to lower the sub levels to mate with mains and the room?

Hope this makes sense...

Kele

[Bob Lombard]

Ah, an interesting arrangement. Because the energy output to the subs
is the same either way, I think it makes no difference. On the other
hand, if I was ever a hi-fi expert it was in another life.

bob

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[ScottW]

"Bob Lombard" <thor...@vermontel.net> wrote in message
news:ldqvh...@news1.newsguy.com...

I think you are right. Most often the volume pots are only attenuators on the
amp input.
The amp itself is a fixed gain device. Raising the level out on the preamp
while
increasing the attenuation on the amp input makes no theoretical difference to
the signal the amp sees.
On the other hand, if you're a believer that less in the path is better, many
attenuators are
effectively in bypass when in the zero position. Certainly the case if you feel
a click
as it sets to zero. Having the amp attenuator at zero and using the preamp
alone for levels
probably is a cleaner path.
Another consideration is the length of the cable between amp and preamp.
A long cable might pick up more noise so a higher signal plus noise attenuated
at amp
might be beneficial.
More often than not, these differences are miniscule at best.

ScottW

[Kele]

I understand that keeping the input signal low (especially bass), there's less chance of bleed to other channels. But it is also logical that a higher signal need not be boosted by the amp as much for the same end sound level. Just trying to give the amp a fighting chance. The amp runs a little warmer with the two subs now tethered to it, but not hot when cranked for half a day. I find it hard to believe that a 100 watt AB-amp channel can drive a sub that had a 1000 watt, 2000 watt peek, class-D plate amp (8" driver). I'm still fiddling with getting the bass balance right: two non-similar subs + system + room. Awolnation-Sail is one I've been playing for its low freqs.

[Barkingspyder]

On Sunday, February 16, 2014 6:48:06 AM UTC-8, Kele wrote:
> I have an amp running two subwoofers from two of its five channels. The amps channels are 100 watts each (damping factor 1000 per channel). Both formally self-powered subs' panel amps are shot so I am running them as dumb sealed enclosure speakers. My preamp is acting as the low-pass filter to the subs. I have no idea what the sensitivity rating is of each sub speaker, but they are both 8ohm. It sounds great... maybe as good as their original amps.
>

How is that dumb? Sealed enclosures have been some of the better speakers and make for good subs, with the right drivers. Damping factor is meaningless in modern audio equipment, I can't remember if it ever was relevant.

> I have two ways of adjusting the volume for the subs: 1) Via the Pre-amp's calibration level for the Sub+L/R channel, and 2) via potentiometer pots on each channel at the (separates) amplifier. The amp's instruction manual states the "0" position (no attenuation) is normal but provides level reduction pots just incase.
>

Having a way to adjust volume levels is crucial for good listening in any environment, especially in a home theater set up.

> My question has do with wanting to make life as easy as possible for the amplifier driving two subs (+ a center and two rears). Currently I have reduced the preamp's output for the subs by minus 8db, and have the amp volume pots at max (one pot about 20% less to balance that sub's sound in the room). Would it be more beneficial for the amp to work less hard by boosting the sub signal out of the preamp and use the amp's pots to lower the sub levels to mate with mains and the room?
>

It does, and I hope my reply does as well.
The most important thing you need to do is get yourself to Radio Shack and buy one of their analog SPL (sound pressure level) meters, so you can match the levels of all those speakers at your listening position. Subs are kinda tricky because so many of them have a bump round 50 Hz, which is why plate amps are no including an EQ for that. Once you match the spl of all your speakers accurately, which can not be done without some kind of measuring device, you will enjoy the sound of your system much more.

[John Pluta]

Actually here is the best way to do it. I was in the same boat. I have a 5 channel surround amp (a Carver AV-705x). It ran 2 surround speakers and 1 subwoofer. I have a pair of Quicksilver V4's running the front channels. My Carver had rear pots for each channel. I had someone remove them with the idea that less is more as well as a shorter path. It was correct and the sound improved immediately.

If your preamp has 2 outputs, run your fronts from 1st output and the other speakers from the 2nd. BTW, running 2 or 3 channels of a 100 watt surround amp should not place much strain on it.

Another choice is to get a X-over for the sub amp and run it into a 2nd preamp output as well. Still another way is to get a used/inexpensive surround preamp like a Sherbourn or Emotiva. That way you can use the multi-channel outputs and run them into your input on your preamp (say video).

John