I have a sub woofer with some old caps, I am unable to find in the UK an equivalent:
Make: Alcap
45 MFD
90VNP
+-10%
Any advice please
Make: Alcap
45 MFD
90VNP
+-10%
Any advice please
How old are those Alcaps, Keith?
They are very reliable and the ones I've measured have remained in spec over tens of years.
They are very reliable and the ones I've measured have remained in spec over tens of years.
Those are axial bipolar types used in a crossover network, two capacitors each 45uF at 90V in parallel.
You may be able to find just one 100V bipolar capacitor at 100uF, which should be ok for replacement of both.
But they may not need replacement at all.
You may be able to find just one 100V bipolar capacitor at 100uF, which should be ok for replacement of both.
But they may not need replacement at all.
Falcon Acoustics stocks 100 V Alcaps, but not 45 uF ones.
https://www.falconacoustics.co.uk/l...tycap-solen-audio-capacitors.html?cat=231&p=2
If the two 45 uF capacitors are in parallel then you could replace them with an 80 uF in parallel with a 10 uF.
However, I doubt if this is necessary.
https://www.falconacoustics.co.uk/l...tycap-solen-audio-capacitors.html?cat=231&p=2
If the two 45 uF capacitors are in parallel then you could replace them with an 80 uF in parallel with a 10 uF.
However, I doubt if this is necessary.
They have to be over 20 years old, The cabs are old Peavey woofers. The one I am trying to fix the sound is as though you have things bouncing on the cone.
The transformer is screwed on the side in the cab.
The transformer is screwed on the side in the cab.
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But if the sub has more than 20 yo, l wouldn't swap it.
Be aware than LL at Alcaps means low loss. It is for caps that has low "resistivity" , and being in parrallel increase twice this performance.
A cheap MKT or MKP of 45 uF /100V or more will do also.
Edit : maybe the voice coil is veilled ? Is it moving freely when pushing the cone with hands?
Be aware than LL at Alcaps means low loss. It is for caps that has low "resistivity" , and being in parrallel increase twice this performance.
A cheap MKT or MKP of 45 uF /100V or more will do also.
Edit : maybe the voice coil is veilled ? Is it moving freely when pushing the cone with hands?
Hi and thanks, yes the cone moves freely. that's what made me think it was caps.
Have changed leads, amp etc, just the same.
Next is to try the crossover from the other cab and if its that or the transformer or the speaker.
At present at a loss..
Thanks again to all for the input
Have changed leads, amp etc, just the same.
Next is to try the crossover from the other cab and if its that or the transformer or the speaker.
At present at a loss..
Thanks again to all for the input
That "transformer' is an 'inductor', part of the low pass filter in conjunction with the capacitors.
Alcaps will last well in excess of 20 years.
The fault seems more likely to lie with the woofer driver itself. Try rotating it 180 degrees in its mountings.
Alcaps will last well in excess of 20 years.
The fault seems more likely to lie with the woofer driver itself. Try rotating it 180 degrees in its mountings.
You should inspect the rear suspension of the subwoofer cone. This is a corrugated disc called the 'spider'. With age, the glue can become brittle and the spider becomes detached from the speaker's basket or from its cone.
Presumably you would have noticed if there was any detachment of the front cone suspension.
Presumably you would have noticed if there was any detachment of the front cone suspension.
Ok, I can conclusively say its the speaker that U/S, turning it round no impact. The spider is all intact.
Now the speaker has very little in the way of markings, so have no idea of ohms, watts as no plate on either driver.
The pictures don't give much away. the only # I can find is UK M23 or UK N23
Now the speaker has very little in the way of markings, so have no idea of ohms, watts as no plate on either driver.
The pictures don't give much away. the only # I can find is UK M23 or UK N23
As I'm seeing it, from the back, the left is the input speakon. The right speakon is the output for the tops. If this is the case, the caps are not even in the woofer circuit, and the transformer style coil is the only thing in series with the woofer and not shunt components. Being this...
I would try the driver in operation outside of the box at low levels and see if it makes the noises you are hearing by itself. If it does not make those noises, you have isolated the problem to the cabinet. Make sure there are no air leaks, that all structures are affixed solidly.
If all this is good, and low levels in the box yield no noise, then it is possible you are bottoming the driver and the voice coil is smacking the backplate of the magnet inside. How far is is moving when the noise occurs? If a half inch or more, then you could be bottoming the driver. This means it is being used too loudly and will lead to premature failure.
I would try the driver in operation outside of the box at low levels and see if it makes the noises you are hearing by itself. If it does not make those noises, you have isolated the problem to the cabinet. Make sure there are no air leaks, that all structures are affixed solidly.
If all this is good, and low levels in the box yield no noise, then it is possible you are bottoming the driver and the voice coil is smacking the backplate of the magnet inside. How far is is moving when the noise occurs? If a half inch or more, then you could be bottoming the driver. This means it is being used too loudly and will lead to premature failure.
I agree with your well worded analyses regarding the disposition of the filter components and the likely bottoming of the driver.
If necessary, Keith could try asking a Peavey spare parts specialist regarding a relacement woofer. For example:
https://www.protechsoundandlight.co.uk/pages/peavey-spares
May not be fruitful given the 1998 date on the unit.
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Wolf, the noise is the same low, high volume, I have changed it over to the other cab and its the same. Good to no that the crossover is nothing to do with the driver circuit.
Galu: will try Peavey spare parts specialist on Monday, also I have found a driver that looks the part
https://www.prebeat.co.uk/speakers-...udio-12-speaker-woofer-driver-500w-4ohm-p4137
Thanks again you all for the help.
Keith
Galu: will try Peavey spare parts specialist on Monday, also I have found a driver that looks the part
https://www.prebeat.co.uk/speakers-...udio-12-speaker-woofer-driver-500w-4ohm-p4137
Thanks again you all for the help.
Keith
I would hold off on purchasing a woofer that simply "looks the part".
The enclosure has been tuned by those twin reflex ports to match the exact characteristics of the original driver.
Not knowing these characteristics means that any substitution would be a hit or a miss affair with regards to the bass performance.
To be clear, the crossover has a lot to do with the driver circuit.
The inductor in series with the woofer passes the bass frequencies while blocking the higher frequencies.
The capacitor in series with with the satellite speaker passes the higher frequencies while blocking the bass frequencies.
P.S. Do you have a model number for these Peavey subs, Keith?
EDIT: You said there was no label on either of the subs. That's problematical!
EDIT: You said there was no label on either of the subs. That's problematical!
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Yes that's the problem, no markings on the cab inside or out, so at a complete loss.
Looking at vintage peavey cabs they made 18" not able to find 12 ".
plenty OF new CABS FOR SALE LOOKING THE SAME WITH OUT ANY drivers, so could have been a home made, that said it does not help with "what was in the cab"?
Looking at vintage peavey cabs they made 18" not able to find 12 ".
plenty OF new CABS FOR SALE LOOKING THE SAME WITH OUT ANY drivers, so could have been a home made, that said it does not help with "what was in the cab"?
Perhaps the enclosure is not so finely tuned to the woofer after all!
However, it would be best to be sure of the woofer's nominal impedance so that you can at least match that when buying a replacement. I'd guess 8 ohms for a pro cabinet.
If you have access to a multimeter, measure the resistance in ohms across the terminals of the good woofer - after disconnecting one of its connecting wires.
That would allow us to deduce its nominal impedance.
However, it would be best to be sure of the woofer's nominal impedance so that you can at least match that when buying a replacement. I'd guess 8 ohms for a pro cabinet.
If you have access to a multimeter, measure the resistance in ohms across the terminals of the good woofer - after disconnecting one of its connecting wires.
That would allow us to deduce its nominal impedance.