Installing new speaker in Maverick bass amp. Help!

Dreamlander

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First off the weber alnico i am putting in is a bit larger than the junk i took out. I had to remove the pot cover just to get it to fit. As I remove the old speaker and all the gasket material, I realize that I am going to need something to replace the gasket i took out. So what does everyone use? I know they make speaker gaskets, but I have been waiting on this thing for a while and want to get it installed. Is there something I could use from the local hardware store?
 

capnjuan

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Hi DL; I don't use anything for gasket; the speaker has a fiber gasket on it that will compress. Are you talking about at the edge of the baffle where it meets the cabinet or are you talking about the leading edge of the speaker seating against the baffle? cj
 

Dreamlander

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Well I was talking about between the speaker and the cab because that is where I pulled cleaned off the old putty like substance, but i am not really sure what I am talking about. I don't see how there would be anything compressing on the speaker. The head of the screw sits directly on the metal part(baffle?) of speaker that sits directly on the cab. The only thing between the screws and the cab is the thin metal on the speaker.
 

capnjuan

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Hi DL; if you're looking at the cone side of the speaker, there should be a tan material going around the outside of the metal rim; although it might seem firm, it will compress; provided you're installing the speaker from the inside, that's the surface that fits flush up against the plywood baffleboard. You can putty it but it isn't really necessary. cj
 

Dreamlander

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Ok, I thought that might have been what you where talking about, but there is no way I can install this speaker like that. The back of the cab is completely stapled and glued on. So i have to install with the speaker sitting on the outside of the hole. Is that a bad thing?
 

Dreamlander

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Yeah, just looked at my 4x12 peavey cab. Speakers mounted the same way with nothing between the speaker and the cab. I can't take it anymore I am going to install this baby and start breaking it in. :mrgreen:
 

matsickma

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Hi Dreamlander,

Yes. As you noted the Maverick Bass amp has the speaker "dropped into" the baffel board. The back of the speaker mounting rim attaches to the front baffel board. Guild did use a puddy material similar to what you are using. I think it was the black puddy often used by Electricians or Plumbers to fill holes that route cables or pipes from outside to inside. Another approach is to get a tube of Silicone rubber RTV and apply a thin layer around the speaker hole. Take a stick or your finger and spread it evenly around the hole about a 1/2 inch wide. Let it dry before installing the speaker. You could probably even install the speaker onto wet RTV and let it cure for a good seal. Make sure you do a pre fit of the new speaker into the hole. Not all 15 inch speakers will fit into the hole under this mounting arrangement. JBL D, K or E 130's or 140's will not fit.

M
 

Dreamlander

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Well, it is a vast improvement over the stock speaker, but it still sounds muddy and flat at high volumes, is this a tendency with a new speaker? Will it sound better once broke in? I guess i will just keep playing and find out. Regardless I think I need to change out the volume pot, it is still scratchy and cuts out after several cleanings. So I am thinking this will probably make a world of difference. But the vol pot is some kind of double pot or something. How do I know what kind of pot I need?

volpot001.jpg


volpot002.jpg

The one on the left.
 

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If you get a digital multimeter, put the probes on the outermost lugs of the volume pot and see if it's in the 1-2 megs range. Are the knobs push on or are they setscrews?
 

matsickma

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I can tell you from my experiance that the Maverick Bass amp is not as bright as the Maverick guitar amp. The speakers are part of the issue with the less than bright tone, and to my suprise, running the Maverick Bass amp, when ran thru the same speakers as a Guitar amp did not result in the same tone. I think Guild intentionally cut the upper end sparkle out of the Maverick Bass amp. To know for sure we need the schematics for both amps. Maybe capn can help here. I assumed Guild tailored the tone of the Bass amp in a manner similar to what they did on the Bass verses Normal channel on the Thunderbass amp. It might be a simple fix by changing the RC network on the tone swich or Bass control LPF.

Also, Yes the POTs don't look to be in good condition.

M
 

capnjuan

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Hi Mike/default/DL; no have the Maverick/Bass schematic; I do have the Maverick/Lead but it only shows a single-function vol pot; yowee....those pots look like somebody sprayed salt water in there. DL; it would be reasonable to expect your new speaker to sound a little harsh or damped until the cone gets a little more flexible.

I was thinking it might be pull on / push off Bright but then there'd only be two connections on the 2nd pot body ??????/ cj
 

capnjuan

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We'ez on it DL; you have the team with you ... of course that would be the Twenty Mule Team ... [sorry; a Geezer joke]. I'll look today on MusicParts.com - they might have the schematic; of course, you could go there too. If they have it, they charge $15/ea and, after carding them, they send you an email with a link to their FTP site where you can download it. Caution; the link is timed to expire after a period of time so, if you buy it, go get it and save it off .... and send DKL, default and I copies.

Incidentally, what you are paying for is the right to download it; MusicParts puts a watermark on it but they don't 'own' the design; they own the exclusive right to sell it. Their webpage doesn't have any language prohibiting you from sharing the file with others provided you don't do it for profit. cj
 

capnjuan

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Bump-a-titty bump-a-titty: Here you go DL: that be your Bart Maverick amp in the pic below:

maverickbassvolume.jpg


Your amp has 'ganged' volume pots controlling volume. Interesting; in the 2-channel / 4-preamp tube bass heads, they added a master volume control allowing the preamp to be turned up to overload and then turned down allowing more variability in tone. In your amp, both gain stages are upped and downed at the same time.

The schematic above is a little confusing; at the far left, it says: Volume 1M (1 meg) 10% LOG but on the right it says: Volume LIN. (in both cases, the 004027 is Guild's part #) Pots are usually either 'audio taper' a/k/a logrithmic or 'linear'. The schematic suggests that the 1st stage is 'LOG' or logrithmic (audio taper) but the second stage is 'LIN' for linear.

Both dual 1 meg audio and linear taper pots are available but I can't say that I've ever seen one of each type ganged together - oh those pesky Guild audio engineers .... :evil: The only thing that makes any sense is that they were trying to keep the last gain stage/driver/output tubes from being overloaded; while the 'front' half of the pot was allowing more volume (dumping less signal to ground), the other or back half is trying to 'meter' or more carefully control the signal seen by the output section.

In any event, why don't we wait on default, Kap'n, Teleharmonium or one of the other solder-heads and see what they have to say before doing anything else. cj
 

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capnjuan

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You're not concerned with the 'LOG' v. 'LIN' question? So which would you use?
 

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I'd go with the audio, I think.

First thing I noticed was that 300k resistor, I would guess that would be there to knock down a basses input. I would think that you could lose that and notice some more gain.

Comparison of circuits, Bass on top, lead on bottom.

screenshot001mg7.gif
 
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