Corrected: Celestion Speaker Issue

[Detroit ABA]

I have an RM-100 that sounds good with clean tones but as soon as you add any gain or switch to higher gain module it sounds terrible. I took it in to get serviced at an authorized Randall Service Center and they biased the tubes, cleaned all connectins, etc, but the issue still exists. I have tried everything and I am at a loss. I tried different guitars, cables, speaker cables, and even installed new preamp tubes. Any ideas on what the problem maybe and how to fix it would be appreciated.

 

[eyeball987]

What speakers are you using? Sounds like you checked everything but the cab. Do you have access to another cab?

 

[Detroit ABA]

I forgot to mention I have checked the speakers. They are Celestion Vintage 30's and they are only few months old in a Marshall 1960 angled cab. The speakers sound great and get good frequency response while playing clean but the amp or something else goes bad as soon as I add any gain. I am going to check the amp with another cab in the next day or so and maybe borrow a different amp to check with my cab. I feel like it has to be the amp but I could be wrong.

 

[eyeball987]

I am going to check the amp with another cab in the next day or so and maybe borrow a different amp to check with my cab.

Good idea. Sometimes clean tones can hide cab/speaker issues. I would guess (hope at least) that the service center would try the amp out before they released it to you. If you were close to Cleveland, I would let you try one of my cabs to test it out.

 

[bruce egnater]

Can you describe "sounds terrible"? What higher gain modules do you have and what kind of tone are you expecting from them?

 

[JKD]

I am going to assume you ran with just the basics to rule out anything else in the chain? i.e.

Guitar->cable->amp->speaker cable->cab

I assume, along with the bias, that the center also changed the power amp tubes? These go out quicker the pre-amp tubes...

A recording might help, is it hum? is it too bassy? sound like a transistor radio? crackly?

 

[Detroit ABA]

I was able to test the head on another cabinet and the issue is NOT with the RM 100 Amp. Bruce, I do apologize for assuming that it was an issue with the amp and thank you for personally for replying to my post. I am really enjoying the MTS platform. I tested the cabinet with other amps and I am having issues with my Marshall 1960A 4X12 cabinet.

I purchased the cabinet as a NOS back in April and the RM 100 used in the beginning of June. All four celestion G12T75 speakers went bad in the cabinet in beginning of August. I purchased brand new celestion vintage 30s right away and here it is about 8 weeks later and now they are toast.

I am not sure what is killing the speakers? I don't run my speakers hard at all (master volume at noon & and modules at 9 o'clock.) I have checked everything inside & out and I am lost on what the issue is with the speakers dying. They sound great clean but once you add any gain they just fizzle out like they are blown. I followed the break in instructions, verified they are wired correct, had them ohm tested (along with the amp), impedence is matched, everything.

I apologize again for now highjacking my own post to vent about speakers. I just wanted to make clear that the issue is NOT with the RM 100.

 

[kc2eeb]

Be very sure they are all in phase correctly. Easy to check. You need to be able to see/touch the back of all the speakers.
Plug in the speaker cable to the cabinet. Take a 9 volt battery and hold the negative to the plug sleeve and tap the positive terminal to the tip
of the plug and watch the speaker cones. They should all move in the same direction when you tap the positve to the plug tip.
If they are out of phase with each other, it will sound thin and "fizzy."
Also a sealed back non-ported cabinet (like a Marshall) will not sound great right in front. They are made to project and you need to get at least 10 feet away from them.

 

[Detroit ABA]

I checked the phasing, and everything moves correctly. Thanks for the reply.

 

[eyeball987]

What speakers are you using? Sounds like you checked everything but the cab. Do you have access to another cab?

Wow. I actually gave useful advice! From your initial description I suspected a cab issue. Glad you figured it out and good luck with the new speaker problem.