Help! Vintage Peavey/Trace Elliot gear

[Andy Jones]

Hi all, long time lurker first time poster.

Yesterday I picked up a 1979 Peavy Century Amp and a vintage (late 70's) Peavey 115 Bass Enclosure Cab rated at 4ohms (unsure of the wattage).

The Century and Cab played absolutely fine, no issues at all even at high volume.

BUT THEN I plugged in my Trace Elliot AH250 and the speaker blew straight away even at 1-2 volume. The speaker driver kicked out an electrical burning smell and just a slight crackle came out.

SO my amp guy said to bring him everything and he'll figure out what's happened. He says the Century is most likely fine but the Trace Elliot may have blown it's output transistor, but it may not have (no smell or anything came from the amp, just the speaker)

Peavey amp: 2 Speaker Outputs - 100w 4ohms 20V rms - Minimum amp load 4ohms - Speaker jacks paralleled. (Only plugged speaker cable into one output straight into cab.

Trace Elliot amp: 1 speaker output - 4ohms - Only info I can find on the amp is for 240volts AC underneath the kettle lead input.

What I want to know is about a replacement speaker in the cab. I've been looking at an 8ohm 15" Peavey Black Widow I can get for a good price, though the connectors are different, they look more like hifi connectors rather than soldered. Would I be able to fit a Black Widow as a direct replacement into the cab and hook the connectors up to the jack input?

Any help is real appreciated and I've attached some pics too.

Thanks

 

[agedhorse]

Did you have both amps plugged into the speaker at the same time?

 

[Andy Jones]

Did you have both amps plugged into the speaker at the same time?

No no, just one at a time. Century first and it worked fine, then when I plugged Trace Elliot in after was when I ran into the problem.

 

[Wasnex]

I believe the AH250 is rated for 250W at 4 ohms, and probably 50-60% of that at 8 ohms (125-150W)

If the speaker is rated at 100W at 4 ohms, it's no wonder you blew it.

The position on knobs do not tell you have much power the amp is making. In fact most amps make their full rated power long before the knobs are maxed out. Some make there full rated power before the Gain and Volume knobs are even turned up to 12:00 (straight up).

As far as replacing the speaker. In order to maintain original performance, you need a new OEM driver or to recone the damaged driver to OEM spec, which may or may not be an option.

Don't assume you can simply buy and expensive driver with a high power rating and get good results. The driver and cab function as a system, so good results requires the drive and cap to work well together.

Drivers are described by a range of electro-mechanical characteristics called Thiele Small (T/S) parameters. The internal volume of the cab and tuning of any ports must be compatible with the T/S parameters of the driver. One driver may work better with a large cab, and another driver may work better with a small cab.

If a cab has ports, they need to be tuned to start becoming active when the driver begins to cut off. With proper tuning, the port smoothly extends the frequency response down to a lower range. Also, as the port becomes active, it suppresses driver excursion, which increases mechanical power handling within the cab intended pass band. However, below port resonance(Fb), response drops off quickly and cone excursions increases. So it's' a good idea to limit how much energy you feed the cab below Fb.

In order to choose a good driver, it needs to be modeled in the cab. This involves using a computer program/app. The volume of the cab and port dimension are entered into the program, along with the driver's T/S characteristics. If you just throw a random driver in the cab, it may not perform very well and it may be possible to blow it with a lot less power than the driver is rated for.

A driver's RMS rating is more a measure of how much energy the voice coil can dissipate without burning. With bass cabs you also need to be concerned with driver excursion (mechanical power handling). If the excursion is allowed to exceed Xmax, the driver is likely to be damaged.

It's not unusual for a driver's mechanical power handling to be significantly less than the RMS power rating, even in well designed cabs. Also if you put the same driver in different cab designs, the mechanical power handling and low frequency response will vary by design.

 

[InkCow]

Peavey could probably tell you if a BW would work in that cab.

This is kind of a surprising outcome, though. I would have to assume something was really wrong with your Trace Elliot. Was it especially loud despite being turned down so low?

 

[Andy Jones]

Thanks for all the info Wasnex, a lot of it went over my head but I get the jist, I've definitely overloaded the speaker with the Trace Elliot, should have stuck with the Century as that seemed totally fine and sounded great!

There is a version of this cab, again late 70's with the same design that does have an 8ohm Black Widow speaker. I definitely can't afford/won't have access to the computer modelling thing, but can I assume that because there is a version of the cab with the speaker (full unit, cone, driver and everything) I hope to replace it with, that it'll work okay?

These are the details of the speaker I hope to replace it with, put straight into the cab:

Peavey Peavey 15" Black Widow 1508-KADT
Impedance: 8 Ohms Power capacity: 1400 W Peak 700 W Program 350 W Continuous Sensitivity: 99.0 dB / 1 W 1 m Usable freq. range: 40 Hz ~ 2 kHz

 

[Andy Jones]

Peavey could probably tell you if a BW would work in that cab.

This is kind of a surprising outcome, though. I would have to assume something was really wrong with your Trace Elliot. Was it especially loud despite being turned down so low?

I've emailed Peavey too but yet to get a response, but to be fair it was only this afternoon (and it's a Sunday).

I hope there's nothing wrong with my Trace Elliot! My amp guy is 50/50 on it which is a little worrying, but no it wasn't especially loud before the frying.

 

[InkCow]

It wouldn’t surprise me, given the vintage, if they aren’t the same cabinet.

I’ll defer to the smarter people who have already replied here, but it sure seems odd that you overloaded it given your account.

 

[Wasnex]

Thanks for all the info Wasnex, a lot of it went over my head but I get the jist, I've definitely overloaded the speaker with the Trace Elliot, should have stuck with the Century as that seemed totally fine and sounded great!

There is a version of this cab, again late 70's with the same design that does have an 8ohm Black Widow speaker. I definitely can't afford/won't have access to the computer modelling thing, but can I assume that because there is a version of the cab with the speaker (full unit, cone, driver and everything) I hope to replace it with, that it'll work okay?

These are the details of the speaker I hope to replace it with, put straight into the cab:

Peavey Peavey 15" Black Widow 1508-KADT
Impedance: 8 Ohms Power capacity: 1400 W Peak 700 W Program 350 W Continuous Sensitivity: 99.0 dB / 1 W 1 m Usable freq. range: 40 Hz ~ 2 kHz

It's possible the AH250 has a problem as well.

There are quite a few different models of BW 15" drivers. Some may work well in the cab and some may be absolutely awful. So, if Peavey sold the cab with a BW driver, you need the specific BW driver they used as OEM. Another possible concern is whether Peavey made any adjustments to the port tuning for various drivers. It may be as simple as dropping the OEM BW in, or you may need to make some changes to the cab for best results.

Hopefully the tech you are working with is taking a scientific approach, rather than dropping in a random driver.

If not, someone here on TB may be willing to model a few drivers if you take internal measurements of the cab and ports.

 

[Andy Jones]

It wouldn’t surprise me, given the vintage, if they aren’t the same cabinet.

I’ll defer to the smarter people who have already replied here, but it sure seems odd that you overloaded it given your account.

This is what I'm hoping that it's a minor costly fix rather than a REALLY expensive fix/not even worth doing and I just have to cry a little and chalk up my loss to a silly mistake!

 

[Andy Jones]

It's possible the AH250 has a problem as well.

There are quite a few different models of BW 15" drivers. Some may work well in the cab and some may be absolutely awful. So, if Peavey sold the cab with a BW driver, you need the specific BW driver they used as OEM. Another possible concern is whether Peavey made any adjustments to the port tuning for various drivers. It may be as simple as dropping the OEM BW in, or you may need to make some changes to the cab for best results.

Hopefully the tech you are working with is taking a scientific approach, rather than dropping in a random driver.

If not, someone here on TB may be willing to model a few drivers if you take internal measurements of the cab and ports.

Thanks, I'm hoping that's the info that'll get back from Peavey themselves about whether the cab shell was the same or tuned differently. The driver I'm looking at buying (if I have to) is also a late 70's one so I'd assume that's what they sold with the cabs at the time. It's cheap enough but not worth taking an uneducated risk over.

My tech guy is incredible with amps, however admittedly himself isn't a 'speaker guy' which is why I've turned to help from here. But yes, thank you for the detailed info it's much appreciated.

 

[J Wilson]

While we're talking UK Trace, can someone explain to me how they used XLR connectors on speaker cables, and moreover, WHY?

 

[Wasnex]

While we're talking UK Trace, can someone explain to me how they used XLR connectors on speaker cables, and moreover, WHY?

XLR speaker cables were actually a thing for a while back in the day. Even early Ampeg SVTs used similar 4-pin speaker connectors. The extra two pins were used as a safety interlock with the SVT. This was to prevent the amp from being set to operate without a speaker connected.

I believe the XLR plugs are a bit better than 1/4", but using the same connectors as mic cables probably led to a few unfortunate accidents.

I could not find a schematic for the AH250 with an XLR.

The V-Types use this configuration:
Pins 3 and 2 are tied together and carry the signal. Pin 1 is ground.

V8 on left. V4 and V6 on right.

 

[agedhorse]

It's very likely that the Trace amp has problems causing the speaker to fail, this was not terribly uncommon.

 

[InkCow]

Ask any gearhead about British electrics of that era…

 

[Zooberwerx]

Hi all, long time lurker first time poster.

Yesterday I picked up a 1979 Peavy Century Amp and a vintage (late 70's) Peavey 115 Bass Enclosure Cab rated at 4ohms (unsure of the wattage).

The Century and Cab played absolutely fine, no issues at all even at high volume.

BUT THEN I plugged in my Trace Elliot AH250 and the speaker blew straight away even at 1-2 volume. The speaker driver kicked out an electrical burning smell and just a slight crackle came out.

SO my amp guy said to bring him everything and he'll figure out what's happened. He says the Century is most likely fine but the Trace Elliot may have blown it's output transistor, but it may not have (no smell or anything came from the amp, just the speaker)

Peavey amp: 2 Speaker Outputs - 100w 4ohms 20V rms - Minimum amp load 4ohms - Speaker jacks paralleled. (Only plugged speaker cable into one output straight into cab.

Trace Elliot amp: 1 speaker output - 4ohms - Only info I can find on the amp is for 240volts AC underneath the kettle lead input.

What I want to know is about a replacement speaker in the cab. I've been looking at an 8ohm 15" Peavey Black Widow I can get for a good price, though the connectors are different, they look more like hifi connectors rather than soldered. Would I be able to fit a Black Widow as a direct replacement into the cab and hook the connectors up to the jack input?

Any help is real appreciated and I've attached some pics too.

Thanks

I assume you're in the UK?

Riis

 

[J Wilson]

XLR speaker cables were actually a thing for a while back in the day. Even early Ampeg SVTs used similar 4-pin speaker connectors. The extra two pins were used as a safety interlock with the SVT. This was to prevent the amp from being set to operate without a speaker connected.

View attachment 4929440

I believe the XLR plugs are a bit better than 1/4", but using the same connectors as mic cables probably led to a few unfortunate accidents.

I could not find a schematic for the AH250 with an XLR.

The V-Types use this configuration:
Pins 3 and 2 are tied together and carry the signal. Pin 1 is ground.

V8 on left. V4 and V6 on right.
View attachment 4929457

Thanks, Was. I can just imagine someone in a hurry plugging a mic cable into the back of one.

 

[eddybuzzard]

No no, just one at a time. Century first and it worked fine, then when I plugged Trace Elliot in after was when I ran into the problem.

Were either of these amps ON when this speaker plugging, and unplugging occurred?

 

[definenredefine]

I'll throw in an additional wrinkle (sorry) - I also have an older (late 70s/early 80s) Peavey 1x15" cab rated at 4 ohms. I believe it has a Scorpion driver in it. Yours may have one as well. Scorpions look like this -

Also the Century is a pretty sweet head. I bet yours sounds awesome.

 

[devnulljp]

Thanks, Was. I can just imagine someone in a hurry plugging a mic cable into the back of one.

Same problem with 1/4" -- lots of people using guitar leads to connect amps to speakers.

I vaguely remember some high end companies using XLRs in their basses too in the 80s -- I think maybe Wal or Alembic ?