Solutions please - for reducing volume on one pair of hifi speakers to match other pair on amplifier driving two pairs simultaneously

Thread Starter

spj747

Joined Jun 23, 2020
1
Dear Sir/Madam,

I am a new member and my electronics know-how is somewhat limited. I have a Creek Evolution 100A integrated amplifier with A+B speaker output capability. I have two pairs of floorstander speakers connected and tend to use them simultaneously, as they sound very good together. My problem is that one pair plays a tad louder than the other - having a higher sensitivity rating (90dB as opposed to 89dB) (2.83V/1m). The amp is rated at 110W into 8 ohms / 170W into 4 ohms. The speakers - (front) Dali Opticon 6s [sens. 89dB - nominal impedence 4 ohms] & (side/rear) Dali Zensor 7s [sens. 90dB - nominal impedence 6 ohms. Max SPL on both is 110dB .. (should that be relevant!).

Does anyone have any ideas re. (preferably straightforward) solutions for this problem ? I would very much appreciate any input offered.

Many thanks.
All the very best.
Regards,

Simon Paul James.
 

KeithWalker

Joined Jul 10, 2017
1,043
Does anyone have any ideas re. (preferably straightforward) solutions for this problem ? I would very much appreciate any input offered.

Many thanks.
All the very best.
Regards,

Simon Paul James.
To make the power received bye the different speakers the same, Connect a 2 ohm resistor in series with each 4 ohm speaker. It sounds too ridiculously simple to work, but it will do the job. Make sure you use resistors with high enough power dissipation for the level of sound you will be using. Ten watt resistors should handle it for normal very loud listening.
Regards,
Keith
 

Audioguru again

Joined Oct 21, 2019
1,588
1dB of different loudness is so small that all you need to do is move the louder speakers 1 foot (30cm) farther away from you.
Adding a series resistance affects the frequency response because the impedance of a speaker changes with frequency changes.
 

Ylli

Joined Nov 13, 2015
965
1dB of different loudness is so small that all you need to do is move the louder speakers 1 foot (30cm) farther away from you.
Adding a series resistance affects the frequency response because the impedance of a speaker changes with frequency changes.
Since the speakers are already different, their impedance curves are likely different to begin with. Adding a passive 2 ohm resistor is not going to change that relationship significantly.

I agree that 1 dB of difference is totally inaudible, the difference heard by the OP must be more than just the relative speaker sensitivities. Ideally, you would want to use a Pi or T attenuator (3 resistors), but the simple series resistor should be good enough (and inaudible as to the change in frequency response).

Assuming the 4 ohm speaker is louder, then adding a 2 ohm resistor in series will drop that level by about 3.5 dB. A 1 ohm resistor will drop the level by just less than 2 dB. A 0.5 ohm resistor will drop the level by 1 dB. If you need more atten, a 4 ohm resistor will drop the level by 6 dB.
 

KeithWalker

Joined Jul 10, 2017
1,043
Since the speakers are already different, their impedance curves are likely different to begin with. Adding a passive 2 ohm resistor is not going to change that relationship significantly.

I agree that 1 dB of difference is totally inaudible, the difference heard by the OP must be more than just the relative speaker sensitivities. Ideally, you would want to use a Pi or T attenuator (3 resistors), but the simple series resistor should be good enough (and inaudible as to the change in frequency response).

Assuming the 4 ohm speaker is louder, then adding a 2 ohm resistor in series will drop that level by about 3.5 dB. A 1 ohm resistor will drop the level by just less than 2 dB. A 0.5 ohm resistor will drop the level by 1 dB. If you need more atten, a 4 ohm resistor will drop the level by 6 dB.
As you stated, adding a passive low value resistor in series with the 4 ohm speaker will not change its frequency response enough to make a difference.
I calculated the value of the series resistor you need. This time I did not make any dumb assumptions. The value you need is 0.9 ohms. This, in series with the 4 ohm speaker will cause the same power to be dissipated by 4 ohm speaker as the 6 ohm speaker when the same voltage is applied to both loads.
Keith.
 
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joeyd999

Joined Jun 6, 2011
4,410
Put a blindfold on. Have someone randomly move the speakers around. See if you can really tell -- reliably -- which pair is which.
 

crutschow

Joined Mar 14, 2008
25,119
Since the speakers are already different, their impedance curves are likely different to begin with. Adding a passive 2 ohm resistor is not going to change that relationship significantly.
You missed AG's point.
The speaker response is predicated on the source impedance being very low.
Since the speak impedance changes with frequency, an added series resistor will cause the response to vary with frequency, as the impedance changes.
That doesn't happen with a low source impedance.

Better to use an auto-transformer type speaker volume control.
They don't add significantly to the source impedance.
 
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Audioguru again

Joined Oct 21, 2019
1,588
I did not mention the change in damping because many people like to hear the boomy sounds of a poor damping ratio but I like the sound to be "tight" and controlled. But the 2 ohm resistor in series with an 8 ohm speaker will probably not be noticeable to the frequency response and the damping (mid-lows will be reduced 1dB and the low frequency resonance and highs will be at full level).
 
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