Hi-Fi speaker volume control question

[quantumtangles]

I would like independently to control the volume output of two pairs of speakers connected to the same stereo power amplifier.

Can I interpose potentiometers between the +ve and -ve speaker cable outputs, which is to say, can I plant four pots in between the amp and the speakers whose output I want to control?

The plan is to balance volume from speakers at the far end of the room with speakers to my right and left that are closer to me. I want more volume from the speakers that are further away.

So can I use pots? If so what pots would appear suitable? Is there a circuit I can build that would make for a nice project?

The system is as follows:

Technics Stereo Power Amplifier SE-A1010
Technics Stereo Control Amplifier SU-C1010
Yamaha Model NS-500 speakers x 2
Yamaha Model NS-200 speakers x 2


Stereo power amplifier specifications:
Output power 100W+100W (4 ohms, 1kHz, 0.05%)
80W+80W (6 ohms, 20Hz - 20kHz, 0.02%)
70W+70W (8 ohms, 20Hz - 20kHz, 0.015%)
THD 0.015% (-3 dB (20Hz - 20kHz), 8ohms)
Frequency characteristic 5Hz-100kHz+0 -3 dB
Dumping factor 70 (8ohms)
SN ratio 98dB(EIAJ)
115dB(IHF'66)
Input sensitivity/impedance 1V/20kohm
Meter indicating range 0.001W-200W (8ohms)
Power source AC100V, 50Hz/60Hz
Power consumption 210W

Stereo Control Amplifier Specs
http://www.usersmanualguide.com/panasonic/stereo_control_amplifier/suc1010

NS-500 Specs:
40Hz～20kHz
1.8kHz
91dB/W/m
8Ω
60W

NS-200 Specs:
35Hz～35kHz
3kHz
90dB/2.83V/m
6Ω
100W
300W


Should I bite the bullet and get an appropriate graphic equaliser/surround sound unit?

 

[davenn]

you are going to struggle trying to find pots that can handle 100W
when I was in the PA game I used to use switched attenuators that handle to ~ 40W
havent seen anything rated for more than that


Dave

 

[shrtrnd]

I would worry about differences in power outputs.
Are you planning to independently control each PAIR of speakers, or each of the
four speakers INDEPENDENTLY?
It sounds simple to think in terms of the different speaker volume levels, but altering
the load (which is what a speaker is), has an effect on the amplifier output circuitry
itself. If you're not careful in balancing the amplifier output loads, you can damage the amplifier
output circuits inside of the amplifier chassis.
Something to consider.

 

[KrisBlueNZ]

As Dave said, the problem is power dissipation. Any power that is not sent to the speakers must be dissipated somewhere, and that place is the series resistors.

If you're not changing the settings often or quickly, you could do something with an array of relays, like a discrete DAC built with high-power resistors, but you'd probably need a microcontroller to control it all.

Also anything you connect between the amplifier and the speakers will affect the damping factor and the frequency response.

A variac would also work... for frequencies below a few hundred hertz!

I would buy a small power amplifier module and slave it from the line outputs of your main amp. These are available as kitsets and pre-assembled for reasonable prices. Google is your friend.

 

[quantumtangles]

Many thanks you guys. As always, you are really helpful and it is much appreciated