75W speaker in JCM900 100W combo?

[robaxeman]

Hi all - Happy New year!

I have a 1991 JCM900 4101 - 100W combo. It has a single speaker - a G12T-75. I believe that this is a 75W speaker. How can this be right when the the amp is 100W? I've never had the amp above 5 or 6 so I don't what would happen if I crank it all the way up.

Anyone have any thoughts as to how this is OK?

Many thanks....

 

[demonufo]

Uhhh, that's not good...
I'd be looking for a 150W speaker, and given Celestions current prices, I'd probably look to Eminence.

 

[maltone]

robaxeman... I'm in the same boat, with JCM 2000 DSL 100 head. A friend has given me his MESA 2X12 roadster cab - on indefinite loan. It has 2 Celestion V30's at 60 watts each.

— Mind you, I'm always on the GREEN/CRUNCH channel, volume at about 4.5, GAIN about the same, or even 3.5. I "should" be ok.

But I was told that if I got 2 100 watt speakers, I'd be ok. You might want to consider theScumback BlackBack BH75 series speakers — The 100 watt versions here:
Scumback BlackBack H Series Speakers

Here's an amazing demo of them by Peter Thorn. The settings are exactly the same for the guitar and amp, and ONLY the speaker was changed: [ame=http://www.youtube.com/watch?v=u6U30BV2kFM]Scumback Speakers demo, by Pete Thorn - YouTube[/ame]

 

[spacerocker]

Hi all - Happy New year!

I have a 1991 JCM900 4101 - 100W combo. It has a single speaker - a G12T-75. I believe that this is a 75W speaker. How can this be right when the the amp is 100W? I've never had the amp above 5 or 6 so I don't what would happen if I crank it all the way up.

Anyone have any thoughts as to how this is OK?

Many thanks....

I wouldn't worry...Unless you continually play flat-out all the time, there shouldn't be a problem. As you say you don't go above 5 or 6, so it should be fine!

Most people with 100W rigs probably don't put out more than about 30 or 40W most of the time.

Obviously, though, if you do put the full 100W through a 75W speaker for any length of time, you will burn it out!

 

[Marshall & Moonshine]

Just remember that most Marshalls are rated for their CLEAN HEADROOM for their wattage. Actual power output can be much higher. I've heard almost twice the stated wattage. Blow the speaker coil and more damage could possibly occur, I think. Ask one of the techs. I think you usually want twice as much rating on the speaker(s) as the rating on the amp to be safe. It will sound better and last longer.

 

[MartyStrat54]

Buy yourself a 16 ohm Eminence Swamp Thang and call it good.

 

[maltone]

Speaking of output...

Can you guys please explain the ACTUAL output of the JCM 2000 - DSL 100 on the:

1) clean channel, volume at half, gain at half = ? output wattage
2) crunch channel, same settings:
3) RED/ULTRA gain channel, LEAD 1, volume half, gain at half:

I would really appreciate the explanation for each setting. Like what does Marshall mean "100 watts" RMS? Is that the clean channel, both vol and gain at 10?

 

[demonufo]

No way to tell really, and it will vary from amp to amp, and be dependant on tubes fitted, and how the amp is biased.

Without putting your particular amp on the bench, there is no way in the world of calculating the very specific answers that you want. And when you move the amp about from place to place, the voltage will vary, and so will the results, subsequently.

100W RMS is its CLEAN output maximum rating (well, up to about 1% total harmonic distortion anyway). Or rather, what a correctly biased amp of that design is capable of producing clean, without clipping. Early Superleads that often had over 500V on the plates, were quite capable of kicking out over 190W fully cranked.

 

[maltone]

Ahhh, ok. I wasn't aware it was that involved. In my case, the plate voltage is 439 VDC, and it's biased at 74mv per side, or 37mv per tube - I think 65% plate dissipation - JCMJMP did it for me - he lives very close to me.

I was asking because I'm really interested in those Scumback BlackBack H75 speakers. I'm wondering if 2 in a 2X12, at 65 watts each would cut it, or would I be better off going with the 100 watt versions.

The loudest I ever play this thing is on the red channel, Volume at about half, gain at 1.5 (if that) because I don't find the red channel very useful as is. I know there are some Joey mods for both channels - especially to make the red channel less fizzy, less noisy. I find it fizzly, and scratchy sounding, and "CLOCKY". If you say that word out loud, "CLOCK", it's a kind of hollow sound, and lacks the definition and warmth I'm wanting to hear. — Certainly gainy, but not in a good way.

I like the available gain on tap, but it isn't warm and full - so I'd like a bit less gain on that channel, more fullness and clarity if it can be had.

 

[demonufo]

Given your plate voltage, and the settings you describe, I would expect the two 65W Scumbacks to be more than adequate.

 

[robaxeman]

Hey Everyone - thanks for the response and discussion.

Scumback speakers - could be a great idea, but not available in UK (that I could see), so shipping costs would be high, on top of already quite expensive gear.

So, back to Celestion (can't bring myself to use anything else really). DrTube reckons this combo had a G12H-100 orginally, but I can't find any of those anywhere, and certainly not on the Celestion site. Given the discussion about an amp's RMS rating being of a clean sound, and therefore putting out more than 100W as it get's cranked up, I thought maybe I should go for a 150W speaker - like the G12B-150 in the 1912 cabinet - but I can't find one of those either! (again, not even on the Celestion site). So for now, I will use my 1922 cab (2 xG12T-75s). (Just put some new EL34s in the amp - sounds brilliant!).

 

[maltone]

robaxman, what EL-34's did you end up using?

 

[dodgethis]

Or you could use Eminence Delta 12s. Rated at 400W. But that's a full range speaker.

 

[MartyStrat54]

I have two of those new in the box.

 

[dodgethis]

Dammit, Marty. Stop tempting me.

 

[JohnH]

Marshall put a Heritage and a Vintage speaker in 100W JVM combos. So far as I can work out, the Heritage is only 30W, so total speaker rating is 60W - so even more of a question!

 

[demonufo]

Marshall put a Heritage and a Vintage speaker in 100W JVM combos. So far as I can work out, the Heritage is only 30W, so total speaker rating is 60W - so even more of a question!

Are you sure they're not using versions of the G12H Anniversary which doesn't seem to be a 30W speaker, like the same speaker mix (one of those and a V30) in some of the 1922 cabs? The G12H30-Heritages are a very expensive speaker in comparison, and I can't see it myself.

 

[robaxeman]

robaxman, what EL-34's did you end up using?

Hi Maltone - I got them off a friend - 1 pair of 'Marshall' and another pair 'Made in Russia' The Marshall one's are shown as 'Grade A' so i assume they're not new. The Russian on'e are brand new.

Sounds great though!

 

[demonufo]

Hi Maltone - I got them off a friend - 1 pair of 'Marshall' and another pair 'Made in Russia' The Marshall one's are shown as 'Grade A' so i assume they're not new. The Russian on'e are brand new.

Sounds great though!

Two different pairs????

Mmkaaaaaay. How closely do they match?

 

[MartyStrat54]

Two different pairs????

Mmkaaaaaay. How closely do they match?

What do you mean by "match?"