BSD-Bad Speaker Day

[Saxonbowman]

A little while back I bought an Epiphone EA-50T Pacemaker amp, made in the mid 60's.

image removed

As purchased it sounded a little thin without much volume. I did some research on this amp and found that indeed this is typical for Gibson products from this time period. Further research led me to some information that there were some filter circuits they put in there to minimize distortion, which also lowered the gain and bass response. I identified these circuits and made an easy to reverse modification which bypassed the offending filters. This resulted in a whole lot more gain and better tone. It sounded great in the mid range, but bass response was not ideal. I see this as an ongoing project and hope to document the mods in a future thread.

I thought by putting a better speaker in I could improve the bass response. So I got a Warehouse Guitar Speakers WGS-10C because it had a big magnet and seemed like it would be the most efficient speaker I could get in that size. Weeel, it didn't work out so well. With the new speaker I got bad distortion and clipping. To make sure I didn't mess something up on the amp I put the old speaker back. It sounded fine. So, the question I have is did I buy a speaker that just won't work with that amp, or is there a problem with the speaker? Both are eight ohms. Could the output transformer just not be able to handle a speaker of that type? Doesn't seem likely to me but just maybe.

I made a short video with the new speaker, then the original. Please excuse the playing.



Any ideas will be appreciated. Thanks!

 

[Dismalhead]

From your video I'd keep the old speaker and send the new one back to WGS. It has decent tone IMO.

 

[Saxonbowman]

From your video I'd keep the old speaker and send the new one back to WGS. It has decent tone IMO.

I'm leaning this way. Very disappointed!

 

[Wobbles]

The new speaker is more efficient, which causes more output power. Something in the circuit can't handle the extra power. OT, output tube, or maybe cathode resistor, would be a good place to look. Good luck.

 

[strat a various]

The new speaker is more efficient, which causes more output power. Something in the circuit can't handle the extra power. OT, output tube, or maybe cathode resistor, would be a good place to look. Good luck.

Speakers don't "...causes more output power." Power is measured in Watts, and the output transformer is outputting whatever wattage that circuit develops. The speaker doesn't influence how much power is generated. An efficient speaker can sound louder ... doesn't change the wattage. OP needs to consult a tech, the story sounds wrong. Speaker could be defective or damaged.

 

[Dacious]

Ok. I'm presuming you have guitar and amp turned right up?

What you are hearing is cranked tone. The WGS (which is total overkill in that amp) is not only more efficient but also more fidelitrous (if that's a word). It's accurately reproducing what the amp is amplifying.

Have you replaced the filter and bypass electrolytic caps on this amp? If not, that's issue no 1. It sounds to me to be distorting due to possibly poor earth's or caps.

You say you've bypassed some of the preamp?. If so, you've got a lot more gain - which is potentially overdriving the power section.

If you put too much gain through the front end, it will make it all the way through the power section. Poor filtering=poor ability to produce bass tones. Ergo, distortion.

The amp should be louder than it is. A tech could go through that for amazingly little money, replace caps, clean contacts and pots, roll a couple of tubes through it and probably make it much louder and cleaner. All you need is one dud resistor that's drifted in value, it can be like having the volume on '1'.

Here's a good example. It sounds like yours, just louder so it isn't necessary to dime it..These
will never have tons of bass. They don't have the power or transformers for that. They do breakup fairly early. It may be the speaker is gunked up from sitting around. But your mods have not fixed the main issue

 

[BobbyZ]

Can you play a different amp through the WGS speaker?
I'm thinking there's something wrong with that speaker. Or and maybe this is wrong! I'm wondering if the magnetic field from that WGS is having an affect on the amp somehow. Not sure if that's even possible!
Playing the WGS with a different amp would give a pretty good idea though.

As mentioned old electrolytics need to go.

 

[Obelisk]

I own a couple of Kalamazoo combos that were made during the same period. In each I put an older blue frame Eminence 10 which improved the overall sound and performance of each amp. They originally came with the same speaker that came with your amp. I would suggest finding a similar speaker for your amp as the Emi has a similar tone to the original speaker, but is more efficient. I generally like ceramic speakers better, but the EL84 seems to couple better with alnico speakers. I believe this Pacemaker came with a 6AQ5 which is a bit more akin to a 6V6 in mini noval socket, but I believe they also came with 6BQ5/EL84.

That WGS speaker sounds broken. I bet if you pushed it hard, the amp would sound like a fuzz pedal. If you haven't fully serviced the amp, then do that first before changing a speaker. A less than 100% functioning amp is never going to give you an idea of what a speaker can do in that amp.

Can you play a different amp through the WGS speaker?
I'm thinking there's something wrong with that speaker. Or and maybe this is wrong! I'm wondering if the magnetic field from that WGS is having an affect on the amp somehow. Not sure if that's even possible!
Playing the WGS with a different amp would give a pretty good idea though.

As mentioned old electrolytics need to go.

Hooking up the WGS speaker to another amp is a good idea to verify if the speaker is broken. It certainly sounds broken in the clip.

Beyond being coupled to the amp, I would think the size of a speaker magnet could have little impact on the performance of the tubes or circuitry by its proximity to the tubes. I have been using an EV SRO with coffee can sized alnico magnet in my Deluxe Reverb. That amp sounds great with a speaker that has a magnet that is easily 3 times the size on the WGS. It's also closer to the tubes and transformers than on the Pacemaker. I suppose magnetic field could have an influence, but my intuition tells me the speaker would need to be making physical contact to induce any major alteration of an amp's performance(like when a string sticks to a pickup).

 

[BobbyZ]

Yeah I'm thinking it's not a magnetic field thing going on, just a bad speaker out of the box. Another amp would tell really quick. I've also put some pretty large magnet speakers in amps and never noticed any interaction. Just a thought really.
If anything I'd expect the WGS to be cleaner sounding than the original and unlikely to break up before an amp of this power level.

 

[BobbyZ]

Another thought. . . . . A bad connection somewhere that's getting rattled by the new speaker. Could be in the speaker wires or inside the amp.
Once I pulled an old C12N out if a BFDR because it made noises. Amp plugged into another cab sounded fine so it had to be the speaker. Right?
Wrong! Cold solder joint on a tube socket. Speaker in the amp just vibrated it enough.
Had I ran the C12N with another amp (real easy to do) I would've saved myself the time to swap speakers and found the real problem sooner.

 

[Saxonbowman]

At work now so this will be brief. The power transformer and filter caps were replaced before I bought the amp. Everything else looks pretty stock. @Dacious thanks for the video clip. Neither the amp nor the guitar were turned up very far in my sample. There is plenty of headroom, at least after the modification. The amp in the clip is an earlier version but the tone and volume are very similar to mine, again after the mod. I'll try to upload the schematic and document the mod when I get home. Output tubes on this one are 6BQ5.

Unfortunately I don't have another amp where the speaker is easily accessible. I'll see what I can rig up. I can at least hook up the WGS out of the cabinet. Won't sound great but would eliminate the magnetic interference question.

 

[telemnemonics]

Assuming you left the amp and guitar volume settings the same it sounds like a bad speaker new from the factory.

Could still be the original speaker sounds good but lacks bass like some vintage speakers, compared to more bass heavy speakers that are best suited to amps with less bass output.
I find vintage 10" speakers often have less bass than modern tens.
But you gotta run another amp through the WGS before returning it.
Sitting on the floor is fine to confirm that the speaker is the source of the raspy sound.
Could be voice coil rub, easy enough to assemble misaligned, especially with a foreign factory subcontracting the build.

 

[strat a various]

Assuming you left the amp and guitar volume settings the same it sounds like a bad speaker new from the factory.

Could still be the original speaker sounds good but lacks bass like some vintage speakers, compared to more bass heavy speakers that are best suited to amps with less bass output.
I find vintage 10" speakers often have less bass than modern tens.
But you gotta run another amp through the WGS before returning it.
Sitting on the floor is fine to confirm that the speaker is the source of the raspy sound.
Could be voice coil rub, easy enough to assemble misaligned, especially with a foreign factory subcontracting the build.

Dropping a speaker can mess up the voice coil alignment.

 

[telemnemonics]

Dropping a speaker can mess up the voice coil alignment.

That's true so it could be bad without WGS being at fault.
I've had speakers with bent frames from being dropped that worked fine too though, and no business is faultless...

At the same time some of the vintage high power handling speakers like Altec and JBL have been known to have the whole cone assembly sag into a buzz, which in come cases improves if you just turn the speaker 180 in the cab so gravity opposes the sag.

 

[Saxonbowman]

Turns out that the back of my Mustang I was easier to get off than I thought so I hooked the WGS up to it. As soon as I turned it up past half way the speaker broke up in the same way as with the other amp. I just laid the speaker in its shipping box for the test so orientation doesn't seem to matter. Looks like it will be going back.

Sometimes the simplest diagnostic methods are the best. Thanks for pointing me in the right direction!

 

[dan40]

Happy to hear that you got it figured out. That should be a great sounding little amp when you get the speaker issue resolved. I have been itching to build one of those older Gibson circuits for quite awhile but just never seem to find the time.

 

[Saxonbowman]

Happy to hear that you got it figured out. That should be a great sounding little amp when you get the speaker issue resolved. I have been itching to build one of those older Gibson circuits for quite awhile but just never seem to find the time.

I was thinking about building something too but figured it would be easier to fix up or mod something. That's how I ended up with this amp. That's why I'd rather tinker with it rather than take it to a tech. That's how I approach most things for better or worse.

Sent from my SM-G950U using Tapatalk

 

[schmee]

Turns out that the back of my Mustang I was easier to get off than I thought so I hooked the WGS up to it. As soon as I turned it up past half way the speaker broke up in the same way as with the other amp. I just laid the speaker in its shipping box for the test so orientation doesn't seem to matter. Looks like it will be going back.

Sometimes the simplest diagnostic methods are the best. Thanks for pointing me in the right direction!

Any speaker will garble laying in a box or on the floor. Just a heads up on that. I dont know that speaker specifically, but those horseshoe magnet alnicos are not real robust speakers in general, the actual magnet inside the horseshoe frame is small.
Most every horseshoe magnet, and especially 10's, are lacking bass and breakup early.... at least in a single speaker application.

 

[Saxonbowman]

I own a couple of Kalamazoo combos that were made during the same period. In each I put an older blue frame Eminence 10 which improved the overall sound and performance of each amp. They originally came with the same speaker that came with your amp. I would suggest finding a similar speaker for your amp as the Emi has a similar tone to the original speaker, but is more efficient. I generally like ceramic speakers better, but the EL84 seems to couple better with alnico speakers. I believe this Pacemaker came with a 6AQ5 which is a bit more akin to a 6V6 in mini noval socket, but I believe they also came with 6BQ5/EL84.
...

I have a Kalamazoo 4 which I actually bought new. It has the same speaker. Its all I have left of an early attempt to play guitar. That amp is no longer working but I hope to bring it back. Is there a modern equivalent to the blue Eminence?

Any speaker will garble laying in a box or on the floor. Just a heads up on that. I dont know that speaker specifically, but those horseshoe magnet alnicos are not real robust speakers in general, the actual magnet inside the horseshoe frame is small.
Most every horseshoe magnet, and especially 10's, are lacking bass and breakup early.... at least in a single speaker application.

I just put it in the box to verify that it broke up in the same way as with the other amp. I think those weak speakers are why they had the tone and volume limiting circuits in those old amps. There are a bunch of filters that you don't find in the circuits of others from the same period.

 

[strat a various]

That's true so it could be bad without WGS being at fault.
I've had speakers with bent frames from being dropped that worked fine too though, and no business is faultless...

At the same time some of the vintage high power handling speakers like Altec and JBL have been known to have the whole cone assembly sag into a buzz, which in come cases improves if you just turn the speaker 180 in the cab so gravity opposes the sag.

Right, first thing to try.