Peavey Bass speaker buzz/distorted- possible to fix?

[Bluemeanie72]

Hi - wonder if anyone can help. I have an old Peavey TNT 115 BW combo that’s been sitting in my garage for about 16 years and I’ve recently joined a new band and wanted to get it going again. It all seems to be working ok except there’s a buzz/distortion on the speaker, overpowering at low volume to the point it sounds like playing through a really bad distortion pedal. If you gently place your finger on the cone at certain positions the noise seems to disappear but really makes the bass tone sound awful.  I have found a spot where you can touch it and crank the volume up and it plays pretty much ok as long as you keep your finger there, I spose I could get a mate to stand at the back of the stage and press it there for an hour but it’s not the best solution  

 

everything looks fine on surface, no tears in cone, I’ve taken off the magnet and all looks fine there as well, I can’t see anything obviously wrong but really I don’t know what I’m looking at anyway 
 

been looking Into a replacement speaker off eBay but wondering if there is a simple fix to it that I’m unaware of.

 

(I should add that I have the technical knowledge and ability of Father Dougal McGuire from Father Ted) 

 

Any pointers would be greatly appreciated - the speaker is a MOD 1502-DT 4 ohm Black Widow 15”

 

thanks 

Edited September 23, 2021 by Bluemeanie72
Title incorrect

[Phil Starr]

You might want to change the title. If there are people out there with expetise in speaker repairs they won't necessarily see this.

 

The glue in old BW speakers doesn't age gracefully, it hardens and goes brittle eventually breaking down. This is used in two places, to stick the central dome to the cone and to stick the cone to the frame. The repair is simple, glue it back down again. To do this without affecting the speaker means using a compatible glue and I use Copydex which is latex based. it sets to form a rubber bond which is flexible and it is compatible with the materials used.

 

you can spot fix the offending bits but usually the glue will go elsewhere. I remove the dome completely and clean off al the old glue by gently scratching away at it then just copydex it back on following the insructions on the pack. the surround is trickier but it is possible to ease the surround away and re-glue that in the same way. Be careful here as it has to go back in the same place, any sideways movement might make the coil rub against the magnet which will kill the speaker. You could try freeing a bit at a time cleaning that and glueing then move on to the next bit. One thing that makes it easier is that you can remove the magnet from the BW's to service them, again with care.

 

Alternatively I have a spare BW I'd be happy to sell, but this is an 8ohm unit. PM me if interested, I'm going to advertise a few bits on BC sometime soon but if you want it you can jump in now.

[Phil Starr]

Oh welcome to BassChat

[Bluemeanie72]

57 minutes ago, Phil Starr said:

You might want to change the title. If there are people out there with expetise in speaker repairs they won't necessarily see this.

 

The glue in old BW speakers doesn't age gracefully, it hardens and goes brittle eventually breaking down. This is used in two places, to stick the central dome to the cone and to stick the cone to the frame. The repair is simple, glue it back down again. To do this without affecting the speaker means using a compatible glue and I use Copydex which is latex based. it sets to form a rubber bond which is flexible and it is compatible with the materials used.

 

you can spot fix the offending bits but usually the glue will go elsewhere. I remove the dome completely and clean off al the old glue by gently scratching away at it then just copydex it back on following the insructions on the pack. the surround is trickier but it is possible to ease the surround away and re-glue that in the same way. Be careful here as it has to go back in the same place, any sideways movement might make the coil rub against the magnet which will kill the speaker. You could try freeing a bit at a time cleaning that and glueing then move on to the next bit. One thing that makes it easier is that you can remove the magnet from the BW's to service them, again with care.

 

Alternatively I have a spare BW I'd be happy to sell, but this is an 8ohm unit. PM me if interested, I'm going to advertise a few bits on BC sometime soon but if you want it you can jump in now.

Hey thanks for that , really useful info, sounds complex if you don’t know what you are doing tho ! (And thanks for correction on title, I hadn’t noticed that!)

 

I took the speaker out again earlier and dismantled it and put back together again and now the buzz seems to have gone, but it went and came back again the other day so I’m not too hopeful it’s fixed itself, your explanation would explain it as if it’s glue it’s possible it could be intermittent depending on how it’s sitting in the cab and vibrations could loosen it again.

 

as for your speaker, I know the 8 ohm version would lose volume , any idea how much volume we are talking about? (I’d plan to gig the amp in pubs/small venues without main PA system) I had been considering that option as I’d seen a few of those kicking about 

 

thanks for your time 

[Phil Starr]

You'd probably lose about 2db in volume, that's noticeable but not huge. 1db is about the smallest change you'd notice, so just a little more than that. I gigged this speaker in a home built cab for years with a Hartke HA3500 (250W @8ohms) and it was plenty loud enough for any pub gig. I bought it as a replacement for a Peavey 2x15 which had developed a buzz like the one you described but then fixed that which is how I know the stuff above. The 2x15 was borrowed so I returned it and used the 1x15 as my gigging speaker.

 

I should have said the buzzing could be other thinks loose in the cab or worst case the coil is damaged which makes the speaker you have unusable as it would then fail fairly quickly. You can test for this by using a pint glass to gently push the cone in, a scratching noise would not be good as that says the coil is rubbing. Peavey BW's are pretty reliable though apart from the glue issue on old ones so my suspicion is that is your problem.

 

£30-40 is the going rate for a replacement BW so that's the worst damage you could do. It's not a difficult job to do if you are careful so despite talking myself out of a sale I'd say give it a go. You've probably located the problem with your finger pressing. 

[Bluemeanie72]

28 minutes ago, Phil Starr said:

You'd probably lose about 2db in volume, that's noticeable but not huge. 1db is about the smallest change you'd notice, so just a little more than that. I gigged this speaker in a home built cab for years with a Hartke HA3500 (250W @8ohms) and it was plenty loud enough for any pub gig. I bought it as a replacement for a Peavey 2x15 which had developed a buzz like the one you described but then fixed that which is how I know the stuff above. The 2x15 was borrowed so I returned it and used the 1x15 as my gigging speaker.

 

I should have said the buzzing could be other thinks loose in the cab or worst case the coil is damaged which makes the speaker you have unusable as it would then fail fairly quickly. You can test for this by using a pint glass to gently push the cone in, a scratching noise would not be good as that says the coil is rubbing. Peavey BW's are pretty reliable though apart from the glue issue on old ones so my suspicion is that is your problem.

 

£30-40 is the going rate for a replacement BW so that's the worst damage you could do. It's not a difficult job to do if you are careful so despite talking myself out of a sale I'd say give it a go. You've probably located the problem with your finger pressing. 

Haha yes I think you may have talked yourself out of a sale ! Thing is I’m in no rush at the minute, we are a way off gigs yet and the rehearsal studio has amps I can use in the meantime.
 

I just dragged the amp out into my garage and cranked it right up , it’s still playing fine and the buzz has gone. The only thing different I did when I took it out this morning was to remove the magnet and generally have a look around before putting it all back together again, no idea why that would have done anything?!  I also rotated its position in the cab by about 90 degrees as well

 

I think I’ll lug it down my next practise session next week and see how it holds out, if it goes again I’ll have a go at your glue idea and if that doesn’t work I’ll go for new speaker at that stage - thanks for all your advice, very much appreciated. 

[agedhorse]

It's possible that there's a bit of magnetic debris stuck in the gap, or just as common would be bits of deteriorating foam from the magnet structure vent. To remedy this, two different methods are used depending on what the problem is.

 

1. Magnetic debris requires the use of folded over masking tape (sticky side out), and patiently running around the gap. It may take 5 or 6 iterations of doing this before it's clean.

 

2. Foam residue requires the use of a business card type paper stock, wet it with mineral spirits, and run that around the gap again and again, changing cards as needed. It may take a dozen iterations of this before it['s clean. Also, very gently clean the inside and outside of the voice coil to remove any foam debris that may have melted to the surfaces.

 

I have never heard of the defective glue issue, nor have I seen it, and I serviced a lot of BW drivers (both in and out of warranty). The assembly is generally very well done.

 

IF you need to buy a replacement basket, be sure to use the same part number that was originally used with the motor, there are some newer baskets that are not fully compatible with the old motors. They may physically fit (sort-of), but the power handling is no greater and the sensitivity ends up being significantly lower. You can always email Peavey support to verify that your basket and motor are compatible. IIRC, there were 3 different motor series.

[3below]

8 hours ago, Phil Starr said:

..... The glue in old BW speakers doesn't age gracefully, it hardens and goes brittle eventually breaking down. This is used in two places, to stick the central dome to the cone and to stick the cone to the frame. The repair is simple, glue it back down again. To do this without affecting the speaker means using a compatible glue and I use Copydex which is latex based. it sets to form a rubber bond which is flexible and it is compatible with the materials used........

 

49 minutes ago, agedhorse said:

....I have never heard of the defective glue issue, nor have I seen it, and I serviced a lot of BW drivers (both in and out of warranty). The assembly is generally very well done............

 

The glue on the BW speaker in the 115BW combo that I owned from 1980 failed in about 2010.  The cone parted company with the frame  during a gig, I tried the copydex approach however was unsuccessful.  I had not caught the damage soon enough.   When I took the speaker apart I also encountered the deteriorated foam reside that @agedhorse mentions. You have nothing to lose by attempting a 'copydex' repair. 

[Phil Starr]

16 minutes ago, 3below said:

 

 

The glue on the BW speaker in the 115BW combo that I owned from 1980 failed in about 2010.  The cone parted company with the frame  during a gig, I tried the copydex approach however was unsuccessful.  I had not caught the damage soon enough.   When I took the speaker apart I also encountered the deteriorated foam reside that @agedhorse mentions. You have nothing to lose by attempting a 'copydex' repair. 

I had three of these that needed repair to the dust cap of which two had the same issue with the surround. That was out of five I had over a couple of years but those speakers may well have been from the 80's too. I have no problem with a speaker that fails after 30 years especially when you can still get replacement parts. I hadn't come across the foam issue but it's useful to know about. I don't know if Peavey are still supplying the replacement baskets but over here the repair was uneconomic you could buy a speaker of similar quality for less than the cost of the basket.

[3below]

9 minutes ago, Phil Starr said:

I had three of these that needed repair to the dust cap of which two had the same issue with the surround. That was out of five I had over a couple of years but those speakers may well have been from the 80's too. I have no problem with a speaker that fails after 30 years especially when you can still get replacement parts. I hadn't come across the foam issue but it's useful to know about. I don't know if Peavey are still supplying the replacement baskets but over here the repair was uneconomic you could buy a speaker of similar quality for less than the cost of the basket.

Likewise I was not unhappy with the value I had from that combo, it did many gigs over the years, faultlessly. I also found repair uneconomic and picked up a used Fender (Eminence) 15" on this very forum.  The next bit will (probably) make @Phil Starrwince (and likewise me, since I was / am a Physicist). I just fitted it and did not worry about Thiele/Small parameters and correct porting. Fortunately it sounded OK (we are only talking 100W here).  TNT combo with a modern speaker and correctly ported will be a pretty reasonable thing apart from the weight :).

[agedhorse]

Where the joint at the cone neck fails, if you do an analysis of the failure you will find that the glue itself was fine but the paper of the cone neck itself fails. This was before the industry recognized the need for reinforcing the cone necks in higher powered speakers, especially those with shallow cone profiles. Other manufacturers encountered the same thing, and one of my projects was the development of revised cones with reinforced necks for drivers that we had originally used throughout the company I worked for at the time.

 

The surround separating from the basket is more likely a production problem rather than a glue problem, this is also something that every manufacturer has to deal with. The dust cap separating from the cone is also likely a production problem since the glue used for that bond was completely different from the other glues. Back then, there were 3 different adhesives used. There were also issues with the aluminum dust cap fatiguing and actually fracturing around the glue line because the MEK glue was so hard and there was too aggressive heat treatment of the aluminum. This too was an industry wide issue, and one reason why manufacturers moved away from aluminum dust caps. They must be very thin (IIRC it's about 0.003"  (0.07mm) aluminum and it must be very stiff, therefore it must be heat treated to a high degree which makes it vulnerable to stress cracking. Even JBL had some issues over the years, and they were the first to successfully perfect the process. 

[DGBass]

As Phil says, Peavey BW drivers of certain vintage suffered certain issues with glue drying out. One thing I have found consistently with these drivers is over time( 20 or 30 years), the foam dust filter in the magnet assembly dries out and parts of it crumble and fall into the air gap of the magnet assembly. Sometimes they fall into the area behind the dome and rattle about behind it. This usually causes buzzing and distortion. 1504DT and 1508 DT models were prone to this. It's an easy fix, take the driver out of the cab and unbolt the magnet assembly from the basket.  Then vacuum any gunk out of the magnet assembly air gap and from the basket assembly. I've found on occasion bits of coil formers broken off in the gap. If it's really bad this can score the voice coil and render the basket unusable. In most cases, cleaning the air gap in the magnet will get your BW working again and be distortion free. Another thing to check when you have the basket detached is that there is no melted foam on the copper voice coil winding. You can usually see this as black gunk on the coil former. This can also be fixed by very careful scraping of any lumps or parts on the coil former. But its delicate work and I'd only recommend this if you have some experience with Peavey BW drivers. 

[Phil Starr]

4 hours ago, agedhorse said:

Where the joint at the cone neck fails, if you do an analysis of the failure you will find that the glue itself was fine but the paper of the cone neck itself fails. This was before the industry recognized the need for reinforcing the cone necks in higher powered speakers, especially those with shallow cone profiles. Other manufacturers encountered the same thing, and one of my projects was the development of revised cones with reinforced necks for drivers that we had originally used throughout the company I worked for at the time.

 

The surround separating from the basket is more likely a production problem rather than a glue problem, this is also something that every manufacturer has to deal with. The dust cap separating from the cone is also likely a production problem since the glue used for that bond was completely different from the other glues. Back then, there were 3 different adhesives used. There were also issues with the aluminum dust cap fatiguing and actually fracturing around the glue line because the MEK glue was so hard and there was too aggressive heat treatment of the aluminum. This too was an industry wide issue, and one reason why manufacturers moved away from aluminum dust caps. They must be very thin (IIRC it's about 0.003"  (0.07mm) aluminum and it must be very stiff, therefore it must be heat treated to a high degree which makes it vulnerable to stress cracking. Even JBL had some issues over the years, and they were the first to successfully perfect the process. 

I hope we aren't putting Bluemeanie off, he just wants a working speaker.

 

This is really helpful to me however, thanks. My experience is of just a few failed units that I successfully repaired. In all three cases the dust cap had come away partially from the cone. The neck joint wasn't a problem in these limited cases. Just one of these drivers had the metal dome the others were fabric domed versions. In each case the adhesive appeared to have crystallised, forming hard granules which crumbled away easily from the cone/surround. I only discovered the partial separation of the surround from the basket when the speakers were removed from the cabs. they were both rear mounted. I each case the glue showed the same crystalline structure and was crumbling. All the speakers were of roughly the same era and were already 20 years old. 

 

I have to say I loved the sound of those old metal domed Peaveys. My first proper gigging speaker was a 2x15 Peavey and I loved the sound it made. 

[agedhorse]

No idea, I never saw that. Peavey used a black MEK glue that was really tough and hard. Usually the aluminum fractured at the edge of the dust cap where it became the lip that fit over the top edge of the bobbin. Once it stated cracking, the fracture would travel and the dust cap would kind of come apart. It's possible that Peavey used a different glue for the European market, the MEK glue was quite toxic and for the most part it's been phased out in the favor on more advanced adhesives.  

 

At one point, the industry tried CA adhesives, they didn't work all that well until new formulations came into being, and now some manufacturers use UV cure adhesives. 

 

Also, at one point, Peavey used a one piece dust cap/bobbin assembly, that was also problematic and expensive to form. These also fractured right at the edge:

 

 

Edited September 24, 2021 by agedhorse