Woofers sound and respond different - what to do?

Dave Bullet · 12th October 2004, 04:26 AM

I've bought 2 Peerless 850122 drivers from Madisound. Both drivers exhibit different:
- cone displacement with a 25Hz tone
- sound different to my ears

I've tried a mono signal and swapped amp channels. It follows the drivers.

What can I do? I've already soldered cables to the terminals so I suppose return is not an option? I don't have an SPL meter / microphone. Would that be the best way to deal with it? Take measurements then attenuate one or the other if it is an efficiency thing?

I don't want to return and probably can't now I've soldered.

Please help!

Cheers,
Dave.

joe carrow · 12th October 2004, 04:33 AM

buy one more, and use whichever 2 of the 3 sound best together?

Nasse · 12th October 2004, 04:40 AM

Don´t have any experience on this but I remeber some speakers need few hours "playing in" before parameters settle to specs

But if they are both new and same batch...

Bill Fitzpatrick · 12th October 2004, 04:50 AM

Send them an email and ask them about it.

phase_accurate · 12th October 2004, 05:01 AM

One thing that just crossed my mind: Apart form the possibility that one of them may be faultiy or that they need more "burn in" -is it possible that one is a 4 Ohm and the other one an 8 Ohm version ? This could easily be checked using an Ohmmeter.

Regards

Charles

Dave Bullet · 12th October 2004, 10:09 AM

joe_carrow:
Thanks - thought of that but there aren't any local retailers / distributors in NZ for this driver. Closest is Aus for AUS$89 + shipping and that would be hit and miss?

others re burn-in period
the first driver was only played by itself fro maybe 15 minutes. After leaving both with a Rammstein house mix

overnight - no obvious difference. The excursion of one is about 1.25 times that of the other at any given volume / frequency (eg. a proportional and linear difference)

phase_accurate:
good idea - I hadn't thought of that. I'll need to borrow an ohmmeter / multimeter (yes - I'm the only human left without one

) and test. Both woofers do have model 850122 on the magnet (and I'm pretty sure the 850122 only comes in an 8 Ohm version).

I should get a mic and let the computer be the judge - to see if they are significantly different when measured.

I certainly trust my ears though... ah well - will have to wait and see. I'll try measuring the resistance, running in longer and we'll see what happens.

Thanks for your replies.
David.

kelticwizard · 12th October 2004, 01:17 PM

As long as you have the multimeter, you might as well measure the free air resonance.

An online tone generator is available here:
http://www.david-taylor.pwp.blueyond....html#SweepGen

And all you would then need is a resistor from 4-10 ohms.

BassAwdyO · 13th October 2004, 01:22 AM

It sounds to me like you have a definite factory defect. If you tested the subs on the same amp and got different results it could only be due to one thing. That would be voice coil malfunction. Sometimes speakers dont fry voicecoils completey the voice coil laminate melts and the copper gets fused or shorted. In that case an entire section of coil gets "skipped" and the current passes through only a portion of the coil. I've seen this happen before. I wouldnt imagine the problem with your woofers is due to the voice coil of one speaker being fried, but a factory defect causing a similar situation. In the weak speaker probably only part of the coil is working due to a short somewhere in the coil. You should definately send it back. Even if it has been soldered, I've never heard of a warranty being void due to wires being soldered on. Check the impedence. I'm sure you'll find a difference

Dave Bullet · 13th October 2004, 01:27 AM

Update:

I emailed Madisound and they promptly replied, saying they would happily allow me to return the 850122s and they would send back a matched pair (good service).

I presume here I will be paying for shipping (both ways) and considering it cost me (via Fedex) USD$50 (yes that's right) to get them here - it will be USD$100 to get USD$80 of matched drivers. Since I've also soldered the drivers, don't know if they will take them back anyway.

I think I'll just try them out and see how they sound.... I've got to get myself setup for measuring.

The other option is if I go the HT route - I could get another 2 as rears then choose the best 2 out of the 4 for the fronts.

Cheers,
Dave.

Bill Fitzpatrick · 13th October 2004, 02:00 AM

If Madisound sent you defective merchandise they should pay shipping both ways for replacement.

12th October 2004, 04:26 AM	#1
Dave Bullet diyAudio Member Join Date: Jan 2002 Location: Wellington, New Zealand	Woofers sound and respond different - what to do? I've bought 2 Peerless 850122 drivers from Madisound. Both drivers exhibit different: - cone displacement with a 25Hz tone - sound different to my ears I've tried a mono signal and swapped amp channels. It follows the drivers. What can I do? I've already soldered cables to the terminals so I suppose return is not an option? I don't have an SPL meter / microphone. Would that be the best way to deal with it? Take measurements then attenuate one or the other if it is an efficiency thing? I don't want to return and probably can't now I've soldered. Please help! Cheers, Dave.

12th October 2004, 01:17 PM	#7
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	As long as you have the multimeter, you might as well measure the free air resonance. An online tone generator is available here: http://www.david-taylor.pwp.blueyond....html#SweepGen And all you would then need is a resistor from 4-10 ohms. __________________ "A friend will help you move. A really good friend will help you move a body." -Anonymous

13th October 2004, 01:22 AM	#8
BassAwdyO diyAudio Member Join Date: Jun 2004 Location: Illinois	Factory defect It sounds to me like you have a definite factory defect. If you tested the subs on the same amp and got different results it could only be due to one thing. That would be voice coil malfunction. Sometimes speakers dont fry voicecoils completey the voice coil laminate melts and the copper gets fused or shorted. In that case an entire section of coil gets "skipped" and the current passes through only a portion of the coil. I've seen this happen before. I wouldnt imagine the problem with your woofers is due to the voice coil of one speaker being fried, but a factory defect causing a similar situation. In the weak speaker probably only part of the coil is working due to a short somewhere in the coil. You should definately send it back. Even if it has been soldered, I've never heard of a warranty being void due to wires being soldered on. Check the impedence. I'm sure you'll find a difference __________________ The golden rule of DIY: Build nice, or build twice!

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12th October 2004, 04:33 AM	#2
joe carrow diyAudio Member Join Date: May 2004 Location: San Francisco	buy one more, and use whichever 2 of the 3 sound best together?

12th October 2004, 04:40 AM	#3
Nasse diyAudio Member Join Date: May 2004 Location: Scandinavia	Don´t have any experience on this but I remeber some speakers need few hours "playing in" before parameters settle to specs But if they are both new and same batch...

12th October 2004, 04:50 AM	#4
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Send them an email and ask them about it.

12th October 2004, 05:01 AM	#5
phase_accurate diyAudio Member Join Date: May 2002 Location: Switzerland	One thing that just crossed my mind: Apart form the possibility that one of them may be faultiy or that they need more "burn in" -is it possible that one is a 4 Ohm and the other one an 8 Ohm version ? This could easily be checked using an Ohmmeter. Regards Charles

12th October 2004, 10:09 AM	#6
Dave Bullet diyAudio Member Join Date: Jan 2002 Location: Wellington, New Zealand	joe_carrow: Thanks - thought of that but there aren't any local retailers / distributors in NZ for this driver. Closest is Aus for AUS$89 + shipping and that would be hit and miss? others re burn-in period the first driver was only played by itself fro maybe 15 minutes. After leaving both with a Rammstein house mix overnight - no obvious difference. The excursion of one is about 1.25 times that of the other at any given volume / frequency (eg. a proportional and linear difference) phase_accurate: good idea - I hadn't thought of that. I'll need to borrow an ohmmeter / multimeter (yes - I'm the only human left without one ) and test. Both woofers do have model 850122 on the magnet (and I'm pretty sure the 850122 only comes in an 8 Ohm version). I should get a mic and let the computer be the judge - to see if they are significantly different when measured. I certainly trust my ears though... ah well - will have to wait and see. I'll try measuring the resistance, running in longer and we'll see what happens. Thanks for your replies. David.

13th October 2004, 01:27 AM	#9
Dave Bullet diyAudio Member Join Date: Jan 2002 Location: Wellington, New Zealand	Update: I emailed Madisound and they promptly replied, saying they would happily allow me to return the 850122s and they would send back a matched pair (good service). I presume here I will be paying for shipping (both ways) and considering it cost me (via Fedex) USD$50 (yes that's right) to get them here - it will be USD$100 to get USD$80 of matched drivers. Since I've also soldered the drivers, don't know if they will take them back anyway. I think I'll just try them out and see how they sound.... I've got to get myself setup for measuring. The other option is if I go the HT route - I could get another 2 as rears then choose the best 2 out of the 4 for the fronts. Cheers, Dave.

13th October 2004, 02:00 AM	#10
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	If Madisound sent you defective merchandise they should pay shipping both ways for replacement.

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