Advice on Music Man 115B 120 speaker

[sharkbarf]

Hey Talkbass - I need some advice and sanity checking on a Music Man 115B 120 combo amp that I just bought. Long story short, I think it has a bad speaker coil.

I got it used from Guitar Center online, shipped across the country to me. It was a gamble - the picture made it look like it had some wear and tear, but the GC condition said everything worked. I'd been looking for one of these for a long time, so I bit the bullet, knowing I could always return it to GC.

It came, it powered on fine, no knob noise. Sounded a little thin as I turned the volume up to low levels, then I noticed it sounded distorted. At any volume, any EQ settings, playing anywhere on the neck, there is distortion. I plugged the output from the amp into a separate cab (8 ohm 10") instead of the built-in speaker, and it sounded excellent. Played for 5 or 10 minutes. That seems to rule out issues with the amplifier portion, right?

Digging around in the amp, there were some old post-it notes that say "bad voice coil." A little research makes me feel like that's the issue.

I took the speaker out, and there are some water marks on the cone. I pushed the cone and it didn't budge at all - I read that was a way to test the coil.

I'm not ready to give up on it. My local GC offered to refund a portion of the cost, so I'm looking at options. Here's what I'm thinking:
Option 1: Return the speaker for full refund, search and gamble on another one someday.
Option 2: Find a local speaker repair shop and have them repair the speaker. Anyone have a rough estimate of that cost? Less/more than $100?
Option 3: Try to either put a new coil in or re-cone the speaker myself. I've never done either, but I'm reasonably handy. Not sure if parts exist for the speaker.
Option 4: Put a new speaker in.

Questions for you that know more than I:
Question 1: What speaker did Music Man use? Based on this price list, there were Electro Voice and not EV versions. I think mine is not EV because there's no branding on the speaker, and it doesn't look like EV speakers I saw pics of online.
Question 2: Would a Celestion Pulse15 be appropriate for this amp/cab? It looked like it had good mentions on TB and seems like it would work based on my basic knowledge. I think the amp wants an 8 ohm speaker? Any other speakers you'd suggest?

Thanks for any input you might have!

 

[agedhorse]

If the cone didn't move at all, it's possible that the pole piece broke off from the back plate and this is not repairable. The speaker must be replaced.

If you don't know exactly what the existing speaker is, reconing will become very difficult because you won't know what parts are needed, no matter how handy you are. It's tough even for an experienced recone tech, and even then, the parts might fit mechanically but you still don't know the electromechanical parameters required.

The closest speaker I am aware of to the original is the Eminence Delta 15A, but it's a little more like the EVM-15L than the original (a good thing imo).

Factor this cost into your decision.

[edit for correct size]

 

[kesslari]

Whatever @agedhorse says is probably the best bet, which in this case sounds like "replace the speaker with an Eminence Delta 12A and you'll be good".

 

[nixdad]

Hey Talkbass - I need some advice and sanity checking on a Music Man 115B 120 combo amp that I just bought. Long story short, I think it has a bad speaker coil.

I got it used from Guitar Center online, shipped across the country to me. It was a gamble - the picture made it look like it had some wear and tear, but the GC condition said everything worked. I'd been looking for one of these for a long time, so I bit the bullet, knowing I could always return it to GC.

It came, it powered on fine, no knob noise. Sounded a little thin as I turned the volume up to low levels, then I noticed it sounded distorted. At any volume, any EQ settings, playing anywhere on the neck, there is distortion. I plugged the output from the amp into a separate cab (8 ohm 10") instead of the built-in speaker, and it sounded excellent. Played for 5 or 10 minutes. That seems to rule out issues with the amplifier portion, right?

Digging around in the amp, there were some old post-it notes that say "bad voice coil." A little research makes me feel like that's the issue.

I took the speaker out, and there are some water marks on the cone. I pushed the cone and it didn't budge at all - I read that was a way to test the coil.

I'm not ready to give up on it. My local GC offered to refund a portion of the cost, so I'm looking at options. Here's what I'm thinking:
Option 1: Return the speaker for full refund, search and gamble on another one someday.
Option 2: Find a local speaker repair shop and have them repair the speaker. Anyone have a rough estimate of that cost? Less/more than $100?
Option 3: Try to either put a new coil in or re-cone the speaker myself. I've never done either, but I'm reasonably handy. Not sure if parts exist for the speaker.
Option 4: Put a new speaker in.

Questions for you that know more than I:
Question 1: What speaker did Music Man use? Based on this price list, there were Electro Voice and not EV versions. I think mine is not EV because there's no branding on the speaker, and it doesn't look like EV speakers I saw pics of online.
Question 2: Would a Celestion Pulse15 be appropriate for this amp/cab? It looked like it had good mentions on TB and seems like it would work based on my basic knowledge. I think the amp wants an 8 ohm speaker? Any other speakers you'd suggest?

Thanks for any input you might have!

I'm interested to see how this plays out, and what you decide.
I've had mine since ordering it new in '82.

 

[sharkbarf]

The closest speaker I am aware of to the original is the Eminence Delta 12A

Thanks @agedhorse for the info and suggestion. You mean the Delta 15A, right? Since this is a 15" speaker. Or is there a reason you suggested 12?

And good point about finding the corrects parts for the mystery speaker. I haven't been able to find any info on what the original was.

 

[agedhorse]

Thanks @agedhorse for the info and suggestion. You mean the Delta 15A, right? Since this is a 15" speaker. Or is there a reason you suggested 12?

And good point about finding the corrects parts for the mystery speaker. I haven't been able to find any info on what the original was.

Sorry, I misread that it was the 112. The Delta 15A is the correct.

 

[bottomzone]

If you want to keep the amp, take GC up on their offer and have them refund a portion of the cost. Otherwise, get a full refund.

 

[Johnny Alien]

Weird. I was just looking at a 115B 120 on the GC used site. So bizarre that they had two around the same time.

I had one but don't remember what the stock speaker was. I can say that I tried a few replacements out of curiosity and nothing sounded good in that cabinet except the stock speaker. Not sure why that was.

 

[agedhorse]

Weird. I was just looking at a 115B 120 on the GC used site. So bizarre that they had two around the same time.

I had one but don't remember what the stock speaker was. I can say that I tried a few replacements out of curiosity and nothing sounded good in that cabinet except the stock speaker. Not sure why that was.

It depends on which drivers you tried, I can think of quite a few drivers that would under-perform the stock speaker.

 

[Omega Monkey]

Can you try the amp with another cab you like, and see if you like the amp in general?

If you do, then you should be looking at ideally $150-200 partial refund from GC (before tax). Otherwise just let it go, Elsa.

If they go for that kind of refund amount (unlikely), I think an EVM 15B would likely be a great replacement. Most of that era MM amps were using various OEM Eminence I think. A JBL D, E, K, or M would probably also be great. Don't be too beholden to the naysayers of doom saying you need to carefully select the precise chosen one driver. People simply did NOT do that in the 70s, but if you replaced a stock driver with EV or JBL, 9 times out of 10 you were going to get a noticeable improvement in sound quality, because the aftermarket drivers were just that much better. The one caveat is the cab tuning and volume can affect the power handling, BUT, any of those pants creaming dream drivers of the time were more or less designed for those applications and basically vice versa with the cabs, many of which were LITERALLY just EV TL-606s (ie the ancestral homeland of the EVMs).

But yeah, $150-200 is what it will likely cost to get a driver like that, maybe more. A more basic replacement that would "do the job" but might not be amazing, maybe more in the $100-150 range (like the Eminence Delta mentioned above).

You can always walk away and let GC eat their own hat when they have to sell the cab for way less. Don't let them push their loss on you. Just return it and walk away if they don't give you a reasonable refund.

 

[GreaserMatt]

I'd find a cool old 15" speaker for it...

 

[agedhorse]

I'd find a cool old 15" speaker for it...

No matter how it sounds?

 

[Bill Whitehurst]

I'm not sure, but I think the Altec - Lansing 421 was an option in those.
If that is the case, then that would likely work in that just fine.

 

[sharkbarf]

I ended up deciding to keep the amp and replace the speaker. Guitar Center was kind enough to give me a partial refund on the purchase, plus a refund of the original shipping, so I feel like I still got a decent deal even with the new speaker. I decided to replace the speaker with the Celestion Pulse15, partly because it seemed like the Eminence Delta was backordered and I was impatient.

And now it sounds great! I'm not sure how the new speaker compares to the original sound-wise, but after playing it at home a few times and with the guitarist in my band, I really like it. It definitely is powerful and girthy sounding, and has plenty of articulation and warmth. The EQ options on the amp seem endless. I'm really glad I got a 15" combo amp (instead of my dinky Fender Rumble 25 with an 8"). Even at low volumes the extra warmth and push from the 15 is noticeable. It can do aggressive/punk and calm/smooth styles equally well.

I've used several dirt pedals on it, too, and they sound great. It still seems like magic to me that a single speaker can vibrate precisely enough to put out really low notes and the high-pitch grit from a distortion pedal, all at (seemingly) the same exact time.

Anyways, thanks to all of you for chiming in with your advice and support! I appreciate the sanity checking, information, and thoughts you all had. Keep on rockin.