Scumback M75 65w (AGI) tale...

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Scumback Speakers

Scumback Speakers

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So I got a call from a client (JL from So Cal) on Tuesday. JL was disappointed that he blew one of his M75 65w speakers in his 4x12 cab after three years.

I asked how he determined it was blown, and he told me how he tested to find out, and I agreed he was right.

Still, this was the first time in years I've heard of this, so I asked him a couple of questions.

Me: Ok, so what were you doing, what amp were you using?

JL: 100w NMV Marshall.

Me: Ok, so where did you have it set for volume?

JL: 8 or 9.

Me: Alright, but even if you've got one of the old 68 Plexi's with the high plate current I doubt you could blow 260w of speakers.
Those high plate current models typically are 125/130w clean (4 on the volume knob), so even at 8/9 you shouldn't be past 220/230w.

JL: Well Jim, it is one of the high plate voltage models (typical Plexi 470v to the plates, his Plexi clone 510v I found out from fusionbear later).

Me: Ok so you don't use a pedalboard, do you?

JL: Yes

Me: Alright but, you weren't doing some dumb ass thing like stepping on a clean boost, then an overdrive pedal plus a fuzz with the amp volume set at 9...were you?

JL: AS GOD INTENDED! It sounded f**king glorious right before it blew up!

Me: Ok...well, you know you kinda hit about 300w plus right, so this isn't exactly a warranty issue after three years.

JL: Right! I got it. I just wanted to call to order four more M75's for my 2nd 4x12 cab.

Me: Ok...now you're talking.

I'm going to have T-shirts made up...I'll let you all see the design when they're ready.
 
:)
 

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Does this happen at all with modern amps like 5150's? Cause I mean, they have four 20 watters in their cabs, and I don't hear too many stories of people blowing them out easily.

Or is this a ridiculously loud old Marshall type of thing?
 
Rex Rocker said:
Does this happen at all with modern amps like 5150's? Cause I mean, they have four 20 watters in their cabs, and I don't hear too many stories of people blowing them out easily.

Or is this a ridiculously loud old Marshall type of thing?
Click to expand...
It is a 1968 100w Plexi clone with the plate voltage set about 10% higher than stock. It can still happen with modern amps if you bias them too hot, and have pedals set to high to create a square wave.
 
Scumback Speakers said:
It is a 1968 100w Plexi clone with the plate voltage set about 10% higher than stock. It can still happen with modern amps if you bias them too hot, and have pedals set to high to create a square wave.
Click to expand...
I think it’s less about the the speakers wattage capability and more about how it was being used. Square wave = temporary DC. Speakers don’t like DC. Very common way to blow speakers in the audiophile world is by not having a enough power and being pushed too hard and the stereo starts to clip (DC) and frys the speakers.
 
300w????? Jesus I better re think my cabs when I run my 72 Trem boosted.
I’d been running my 79 cab with 65s; so far no worries. But it sounds like I better run an additional cab. I have 505v pt.
 
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