50w / PPIMV / Quad o' ScumPVCs = safe?

[somethin'else]

Alright fellas, I have to say Jim's PVC speakers are giving me the massive wood! Just outstanding tone from those, and I love the Ms and Hs both, so I'm stuck there for now.

SO: I have a '68-ish 50 watter with LarMar in a 2x12 combo cab with a matching 2x12 extension cab... kind of a nice portable 4x12.
Usually at gigs, I run it with the LarMar around 3-6, depending on the house, and only the combo loaded with 6402/H75.
I don't know how many watts output that might be, since the PPIMV is variable.
I've been told that with an attenuator, say for a 50 watter: -3db would halve it to 25w, -6db would halve the 25w to around 12-15w, -9db would halve the 12-15w to around 8w, and variable on down from there.

A healthy 50w clean is 80-90w full tilt? Is that a good assumption?

I'm wondering if I got a quad of PVCs, would I be safe running the single 2x12 (40w) with the LarMar no higher than 5, for smaller houses, and adding the 2nd 2x12 and running the amp wide open for better sized rooms.

Can anyone guesstimate what the wattage output may be for a 50w plexi through the range of the LarMar?

I dream of a quad of the PVCs, but would hate to melt them and end up with really expensive wheel chocks!

Thanks in advance fellas, and a Big Ass Kudos to Jim for raising his own bar with the new offerings!!!

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[rgorke]

Jim would probably be the best to answer this but with those the safe bet is to run a 50 watter with four of the PVCs.

And yes, they sound even better in person.

[irwin4star]

I have an analog ac volt meter hooked up to my other speaker out, I'll check the voltage readings. All my amps have standard larmars, el34's and is set on 16 ohms. What ohms you running, what volume? Jumpered? Tone control settings? Circuit?

[Scumback Speakers]

You will not be safe running two PVC's with your amp at that volume. You'll need four, sorry.

[irwin4star]

At the speakers, you'll have to stay under 25v peak at 16 ohms and about 18v peak at 8 ohms.

[somethin'else]

I have an analog ac volt meter hooked up to my other speaker out, I'll check the voltage readings. All my amps have standard larmars, el34's and is set on 16 ohms. What ohms you running, what volume? Jumpered? Tone control settings? Circuit?

Thanks Irwin, I have 6CA7s, not jumpered, 8 ohms out to 8 ohm 2x12.

At the speakers, you'll have to stay under 25v peak at 16 ohms and about 18v peak at 8 ohms.

Man, I wish I understood that! Or how to check.

You will not be safe running two PVC's with your amp at that volume. You'll need four, sorry.

And there it is. Thanks Jim, I was afraid of that. So, a 50w PPIMV'd to 3-4 would still be putting out more than 40w?
I would need to run 4, regardless, eh?



Oh, rgorke, or anyone running a quad of these with a 100w? How are you doing it? Attenuating to -6db & -9db? I assume that would be safe?

Thanks!

[irwin4star]

All you have to do is measure ac volts across the speaker tabs while playing or looping something that has the same volume as playing. If I run my larmar at 3 it knocks alot of power down.

[somethin'else]

All you have to do is measure ac volts across the speaker tabs while playing or looping something that has the same volume as playing. If I run my larmar at 3 it knocks alot of power down.

Thanks! I think I can do that.
So, 18v peak at 8 ohms is what I'm looking for? What does that equate to? IE, is this relative to wattage output?
(foolhardy) 18v @ 8 ohms peak = 40w? Hey I gotta ask!

Cool, a project! Thanks for the tip Irwin.

[irwin4star]

Yep, 18v would be 40.5w @8 ohms and loud as hell.

[Scumback Speakers]

You will not be safe running two PVC's with your amp at that volume. You'll need four, sorry.

And there it is. Thanks Jim, I was afraid of that. So, a 50w PPIMV'd to 3-4 would still be putting out more than 40w?
I would need to run 4, regardless, eh?

I'm sure I've blathered this before but I'll say it again one more time (sure not to be the last time!).

50w dual EL34 JCM/JMP/1987x type amps put out 50-55w clean (no distortion, before edge of breakup). That can happen anywhere from 2-4 on your volume knob. In excess of that you get more volume/gain/overdrive, all the way up to 90-99w at 7-9 on the volume knob.

100w quadl EL34 JCM/JMP/1959 type amps put out 110-130w clean (no distortion, before edge of breakup). That can happen anywhere from 2-4 on your volume knob. In excess of that you get more volume/gain/overdrive, all the way up to 170-235w at 7-9 on the volume knob.

Those levels are minimum/maximums in my experience based on real Plexis, Metro kits I've built, other clones. When rgorke was here a few days ago he played my 50w clone. He said it was plenty loud. That amp has a Mercury BluesBreaker PT and a special 50w MM OT that according to Paul @ Mercury puts out 5w less than their standard OT but had more even harmonics in it due to the winding method.

Roger's ears were ringing after playing for just a few minutes and he stood 15 feet back, but we also had the amp on 8-9. Still, if the OT specs are correct it puts out around 45-50w clean and 85-90 dimed (cranked to 10).

In answer to the voltage question, when I measured my 50w (the one described above) with the volume set at 8 it put out 36.4 volts to the 4x12 cab.

So here's the bottom line...The PVC models are sold with no warranty due to this particular voice coil used. If you want to risk two with your amp, and they burn up, you'll be pissed. Then you''ll wish you'd gotten four for sure. That's why I put the recommendation I did up on the site, and here as well. It's the price of admission to get that tone, guys, sorry!

I don't know how much clearer and plainer to say it. Now excuse me for being so short and curt on the subject but it's time to run to the bathroom again!

[somethin'else]

There, all culled into (another) one place. Thanks again for clarifying and reiterating every bit of this, Jim. I know it's a pisser to have to keep reminding folks, so I will copy/paste this and get a tattoo of it on my forearm, right next to my secret game plays!

Worth the price of admission, Indeed! This post should be your authorized Disclaimer on the PVCs.

(Hope you feel better soon!)

[rgorke]

Dave,

I don't have the PVCs. I just demoed them at Jim's place a couple days ago. I have my amp (100 w) variac'd down to 90 ish volts and running through a Weber attenuator on about 2 or 3 tops. My cabinet only has 4 25 w speakers, so I don't risk frying the speakers. I now know I am not close o their ratings after being at Jim's. Yeah, my ears were ringing at the volume of a 50 watter. The tone was killer.

All three cabinets sounded fantastic albeit with their own nuances.

[somethin'else]

Dave,

I don't have the PVCs. I just demoed them at Jim's place a couple days ago. I have my amp (100 w) variac'd down to 90 ish volts and running through a Weber attenuator on about 2 or 3 tops. My cabinet only has 4 25 w speakers, so I don't risk frying the speakers. I now know I am not close o their ratings after being at Jim's. Yeah, my ears were ringing at the volume of a 50 watter. The tone was killer.

All three cabinets sounded fantastic albeit with their own nuances.

Right on. I'm just using a 2x12 with a 6402 and an H75. I know I'm not anywhere near the danger zone though as the PPIMV rarely gets around 4-5 tops.

I still want to see what the amp's doing at different outputs. Does anyone have a chart on how the v=w ?

[irwin4star]

You can just use an ohms law calculator. They're everywhere online.

[somethin'else]

Got it Irwin, Thanks again for all your help! God, am I a newbie!