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daws0n
21-02-2014, 06:33
I own the pair of large profile model 10 monitor speakers and have had them advertised for sale here. I've had them out of storage again and playing in my system for a short while - finally got a keen buyer and the buggers have failed on me!!

Back last year I was informed that they incorporate an early pair of volt b250 (before they changed the basket to the cast aluminium ones - the speakers were produced in 1980). Sadly, one of them has stopped working during playback - there is still movement/sound from the driver but it now produces a distorted/warbled fluttery sound with very little bass output.

Since they are early drivers would a new generation b250.x drop in replacement work? If not, is it possible to repair what ever has gone wrong with it?

Cheers

Dawson

daws0n
21-02-2014, 06:44
P.S The driver produces a load scratching noise when gently pushed - a lot of resistance in movement. Appearance wise, it looks fine (no damage/perforation to paper cone)

YNWaN
21-02-2014, 07:56
Unfortunately your description (a very good description) describes the symptoms of the voice coil wire delaminating from the voice coil former. On the plus side, Volt are still very much in business and when I dealt with them, a year or so ago, were very helpful. I suggest you give them a call (or email) and they will tell you your options.

daws0n
21-02-2014, 08:20
Aye I thought so. How does that happen?? The b250s are known for high wattage handling (PAs etc... the back states 200w) and my Exposure amp only outputs 80 max! Specs wise they go well beyond what I would drive them at.

I did get a bit excited after a few hours and probably hit 95dB average SPL for a few tracks when the farting started (not very loud, but loud enough). Me thinks the old girls just couldn't handle the techno vibes :( It went something like:

Oni Ayhun - 02. OAR003-B (Original Mix)
DJ Mujava , Township Funk
Squarepusher - 03. Stadium Ice

*fart fart fart*

337alant
21-02-2014, 09:18
http://www.voltloudspeakers.co.uk/About_Us/about_us.html
Just contact Volt directly and send the driver back for repair, good friendly service they did BM 220.8 for me a few years ago

Also check you amplifier output for DC offset

Audio components sell the drivers as well
http://www.audio-components.co.uk/store/SubCategory.asp?SubCategoryID=101


Alan

daws0n
21-02-2014, 10:10
Thanks for that Alan, I have sent an email. Was the repair job expensive? Could you please explain how to check for DC offset? Can I do that at home?

Others have suggested that perhaps it is due to my power amp being underpowered.. Ive had them playing louder for longer in the past, would have though 80wpc is plenty of juice. They were playing at about 10-10:30 on the dial so not hard IMO.

My dynaudios are a far tougher 6ohm 84dB load so Id say those are far more demanding power wise.

What do you think?

YNWaN
21-02-2014, 11:07
Where did you have them in storage - could they have got slightly damp?

hifi_dave
21-02-2014, 11:12
I've suggested, on your PFM post, that it might be corrosion or suspension sag by being in storage. Try rotating the driver 180 degrees to centre the voice coil.

daws0n
21-02-2014, 12:06
They were stored the right way up under the stairs. Thanks Dave I will give that a try.

337alant
21-02-2014, 12:16
Thanks for that Alan, I have sent an email. Was the repair job expensive? Could you please explain how to check for DC offset? Can I do that at home?

Others have suggested that perhaps it is due to my power amp being underpowered.. Ive had them playing louder for longer in the past, would have though 80wpc is plenty of juice. They were playing at about 10-10:30 on the dial so not hard IMO.

My dynaudios are a far tougher 6ohm 84dB load so Id say those are far more demanding power wise.

What do you think?

They charged me £75 +PP, but what I got back was just like a new driver, they even changed the cast alloy chassis for a black anodised one. My other driver wasent damaged but was 20 years old so I sent that one off as well.

To check for DC offset just set a volt meter to DC milli volts and check across your red & black speaker terminals on each channel at the back of the amp with no speakers attached and the amp switched on
A normal reading would be less than 40mv but up to 100mv still ok but is a warning that you have a leaky cap somewhere, feedback cap usual culprit.

Alan

YNWaN
21-02-2014, 13:36
I doubt it is the driver sagging, from the severity of the description - easy enough to try though. DC offset may be the problem though - in which case any speaker will be in danger. Get a voltmeter (any cheap one will do) and measure the DC present between the + and - terminals of the speakers when the amp is turned on.

daws0n
21-02-2014, 18:26
Checked DC offset and thankfully the amp is fine - 6mv / 1mv.

To be on the safe side I unplugged all cables from it and measured directly on the speaker outputs. Since exposure don't have binding posts this was a bit of a pain though as it required digging the needles into the recessed holes (they take 4mm plugs only), I presume in future it is safe to measure with the speakers plugged in at their inputs instead?

Thanks for the advice everyone, I've yet to hear from volt so will await correspondence before making the next move.

istari_knight
21-02-2014, 23:35
Preferably DC offset is measured with input shorted & no load connected.

From the test you've done it's safe to say the amp is fine :thumbsup:

nat8808
22-02-2014, 00:09
I did get a bit excited after a few hours and probably hit 95dB average SPL for a few tracks when the farting started (not very loud, but loud enough).

Really too much information mate. Tried charcoal tablets?