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oldmako

Uneven volume at low levels - Forte 2

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I use these Forte 2's in my bedroom and frequently at very low volumes.  With more than one amp/receiver I have an annoying difference in speaker output.  I have to modulate the balance to get the sound right, but with each change of volume comes another change in balance.    Speaks equal length from amp.   Wires equal length and gauge.  I have tried reversing the R/L RCA's, etc.

 

 

Is this a crossover issue?

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I would try swapping components between speakers so you can narrow it down to a specific piece....crossover or driver is likely if changing the amp, wires, etc didn't improve it

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This is a scenario that has always been to me like so many fingernails on chalkboards.

 

My guess is it's not any equipment subsequent to the preamp(s).  Channel tracking imbalance in volume (and bass/treble) controls is a very common problem.  Play something exactly the same through both channels (mono, two lefts, or two rights), lift the speaker "-" leads from the amplifier and clamp them together unattached to anything else (see footnote).  If/when the two channel outputs match, there should be no sound through the speakers regardless the volume level.  You can adjust the balance control to get them quiet, but I'd bet the balance knob will have to be shifted to a different spot at the lower volumes mentioned above.

 

The only cure is replacement of the volume control with a better-matched unit, or newer equipment which doesn't actually use a ganged pot anymore for that function.  If neither are practical at this time, then rig a system to switch to mono and readily lift/combine the speaker common leads to reset the balance control at each "critical" volume setting.

 

In this case if the problem lies with a speaker, all else being equal (which it likely isn't) the same speaker will always be the quiet one no matter the hookup scheme in use.  It's not always the one speaker itself, is it?

 

Footnote:  some equipment inverts one amp channel signal and has the speaker outputs "wired backwards" internally to re-invert the signal.  They do this so large signals common to both channels don't have both channels "running off of" the same power supply rail together.  It actually does better-balance the load on a common power supply.  In this case you'll have to lift one channel "-" speaker wire and the other channel "+" wire and tie them together "in the air."

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Pot tolerance.  No, not that pot.  Not that tolerance.

 

Old fashioned main volume controls can be a big problem this way.  My old (c. 1974) McIntosh c28 drove me crazy.

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3 hours ago, oldmako said:

I use these Forte 2's in my bedroom and frequently at very low volumes.  With more than one amp/receiver I have an annoying difference in speaker output.  I have to modulate the balance to get the sound right, but with each change of volume comes another change in balance.    Speaks equal length from amp.   Wires equal length and gauge.  I have tried reversing the R/L RCA's, etc.

 

 

Is this a crossover issue?

Have you tried a different pair of speakers in there to see if there is a similar result?  

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The problem is likely the volume control on the amp, not the speakers.  Though it may be true that their high efficiency makes such channel imbalances more apparent. 

 

I sent back a Peachtree Nova, and a Bryson BP-25 (A preamp) for adjustment/ repair and neither came back totally balanced.  Hence, I sold them.  Sadly, i think it’s inherent in some volume control designs.  This is one reason I suggest people NEVER get an integrated or pre-amplifier that lacks a balance control.  

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I say get one with a rotary encoder or any other method that doesn't require precise synchronization between two pots' wipers / variably-resistive elements.  Even if they're well-synched they get noisy over time, requiring periodic maintenance.

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15 hours ago, glens said:

This is a scenario that has always been to me like so many fingernails on chalkboards.

 

My guess is it's not any equipment subsequent to the preamp(s).  Channel tracking imbalance in volume (and bass/treble) controls is a very common problem.  Play something exactly the same through both channels (mono, two lefts, or two rights), lift the speaker "-" leads from the amplifier and clamp them together unattached to anything else (see footnote).  If/when the two channel outputs match, there should be no sound through the speakers regardless the volume level.  You can adjust the balance control to get them quiet, but I'd bet the balance knob will have to be shifted to a different spot at the lower volumes mentioned above.

 

The only cure is replacement of the volume control with a better-matched unit, or newer equipment which doesn't actually use a ganged pot anymore for that function.  If neither are practical at this time, then rig a system to switch to mono and readily lift/combine the speaker common leads to reset the balance control at each "critical" volume setting.

 

In this case if the problem lies with a speaker, all else being equal (which it likely isn't) the same speaker will always be the quiet one no matter the hookup scheme in use.  It's not always the one speaker itself, is it?

 

Footnote:  some equipment inverts one amp channel signal and has the speaker outputs "wired backwards" internally to re-invert the signal.  They do this so large signals common to both channels don't have both channels "running off of" the same power supply rail together.  It actually does better-balance the load on a common power supply.  In this case you'll have to lift one channel "-" speaker wire and the other channel "+" wire and tie them together "in the air."

WAY TOO COMMON, even in high end equipment.   You will see many measurements show volume control tracking.

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21 hours ago, oldmako said:

I use these Forte 2's in my bedroom and frequently at very low volumes.  With more than one amp/receiver I have an annoying difference in speaker output.  I have to modulate the balance to get the sound right, but with each change of volume comes another change in balance.    Speaks equal length from amp.   Wires equal length and gauge.  I have tried reversing the R/L RCA's, etc.

 

 

Is this a crossover issue?

If you have tried  totally different electronics and the result is the same, you likely have a network issue. And unless its always been this way, which might point to a voice coil problem or someone swapped a voice coil or completely different driver,  given you're not the original owner of the speakers. Could be a bad cap, transformer or even a loose connection or cold solder joint, somewhere.  The signal travels at almost the speed of light, so you can rule out a cable length.

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40 minutes ago, Max2 said:

Could be a bad cap, transformer or even a loose connection or cold solder joint, somewhere.

 

I've seen bad solder joins cause this. At a very low signal level, the can drop out and now even work, but higher voltage and al of a sudden your signal is there. If you can pull the crossovers out and reflow the solder on all the connections, I would have a go and see what you get.

 

Bruce

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I have two Crown xli800's. Great amps but the output between the two is clearly different and after I set these up with a way to control gain from each to balance output all was well. Lots of those caps in even the better amps have 5 or 10% tolerance so if you go to the extremes at each end it still passes manufacturer tolerance but can be up to 20% different worst case scenario.

1 hour ago, Max2 said:

If you have tried  totally different electronics and the result is the same, you likely have a network issue. And unless its always been this way, which might point to a voice coil problem or someone swapped a voice coil or completely different driver,  given you're not the original owner of the speakers. Could be a bad cap, transformer or even a loose connection or cold solder joint, somewhere.  The signal travels at almost the speed of light, so you can rule out a cable length.

Good comments as all these things can come into play but I figure the most likely culprit is two different amps.

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1 minute ago, Dave A said:

I have two Crown xli800's. Great amps but the output between the two is clearly different and after I set these up with a way to control gain from each to balance output all was well. Lots of those caps in even the better amps have 5 or 10% tolerance so if you go to the extremes at each end it still passes manufacturer tolerance but can be up to 20% different worst case scenario.

Good comments as all these things can come into play but I figure the most likely culprit is two different amps.

That would be the easy diagnosis.  He really needs to just bring in an AVR or something to actually see if its a speaker problem.

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2 hours ago, Max2 said:

That would be the easy diagnosis.  He really needs to just bring in an AVR or something to actually see if its a speaker problem.

 

On 8/18/2019 at 11:37 AM, oldmako said:

With more than one amp/receiver I have an annoying difference in speaker output

I assume from what the OP said that this happens with two different amps hooked up at the same time.

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18 minutes ago, Dave A said:

 

I assume from what the OP said that this happens with two different amps hooked up at the same time.

Well it could be the receiver if he is using it as a Pre, but has tried two different amps.  He needs a fully different source to take the first step to determine speaker problem or electronics problem.   We need more clarity

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4 hours ago, Max2 said:

He needs a fully different source to take the first step to determine speaker problem or electronics problem.   We need more clarity

 

If it's a speaker problem (difference in output between them) then all needs doing is swapping speaker leads between channels for confirmation.  Is it always the same one that's quieter?

 

While lifting and tying together their commons playing a mono signal will immediately indicate whether there's a proper null difference between what's getting sent to the two speakers.

 

Yes, verification of what's happening is needed to stop all this speculation.

 

A "fully different source" is not required to gather all the info necessary.

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2 hours ago, glens said:

 

If it's a speaker problem (difference in output between them) then all needs doing is swapping speaker leads between channels for confirmation.  Is it always the same one that's quieter?

 

While lifting and tying together their commons playing a mono signal will immediately indicate whether there's a proper null difference between what's getting sent to the two speakers.

 

Yes, verification of what's happening is needed to stop all this speculation.

 

A "fully different source" is not required to gather all the info necessary.

You could be right, but If he could identify the single bad channel after a couple of power source swaps, he wouldn't have to post this problem.

 

I have to modulate the balance to get the sound right, but with each change of volume comes another change in balance.

 

You can swap speakers and mess around with that for a while, possibly still scratching your head with random outputs continuing....or hookup another powered source and put an end to it right then. 

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That's a much "more involved" process.  By floating the tied-together common leads it doesn't matter if one speaker is louder than the other.  When both channels are amplifying the same signal the same amount, there will be (virtually) no difference in potential between the "+" outputs, thus no sound through the speakers.  If then the commons are re-attached and there's a volume difference between the speakers, the  offender has been found..

 

If the balance control had to be moved to obtain the null, variously at different volume settings (almost guaranteed), then likely (est) the problem was found before re-connecting the commons.  Which should be done at a reasonable volume setting with null-adjusted balance to confirm the speakers in fact play the same volume.  Or not.

 

Everything can be determined with the equipment already in place.

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You guys are astonishing.   Many thanks for your input.

 

To clarify I have used a Marantz 2240, a Fisher 500C and an old Pioneer SA9100 to power the speakers.  None at the same time.  The problem persists.  

 

I bought the speakers used from a guy who seemed to know and care little about hifi.   Pretty funny that he owned a 1600 dollar pair of speaks!  I should mention (and I just now recalled) that one woofer was bad and replaced with the proper speaker purchased from Klipsch.   I suppose it's possible that could have something to do with it, but being a bottom feeder, there's a lot that I don't know.   I am out of the country right now.  When I return I will attempt to do some more sleuthing.  

 

Thanks.

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