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Old 03-21-2014, 04:47 AM   #1
bluestratplayer
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Running multiple cabs with my Mesa

Ok I have a Roadster combo. The speakers are plugged into the 16 ohm jack so Im assuming its 2 eight ohm speakers wired to 16 ohms. I want to run a 4x12 cab under it but the amp only has dual 4 ohm outputs for running 2 eight ohm cabs. If I get a 16 ohm cab, can I run the eight ohm speaker out to a THD hotplate 8 ohm model, then connect the speakers to the outputs on the hotplate?

The hotplate outputs are wired in parallel so that's 16 ohms to each jack when both are connected correct?

Is there a better way to accomplish this goal outside of replacing the combo's speakers?

Thanks for helping.

Oh, this might help http://www.mesaboogie.com/Product_I...earPanel-LG.htm
rear panel view of the roadster
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Old 03-21-2014, 05:10 AM   #2
Offworld92
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Your cab has two 4 ohm speaker outs for using 2 cabs, right?

You could easily wire the internal speakers in parallel for 4 ohms.

If the cab has four 16 ohm speakers in it, you can rewire each pair in parallel for 8 ohms, then wire the two pairs together in parallel for 4 ohms total.

Done and done.
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Old 03-21-2014, 05:17 AM   #3
bluestratplayer
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those four ohm speaker outs are wired in parallel for two 8 ohm cabs. That's my problem.

Could I make a splitter to do what I want. Eight ohm from amp to input, input wired to two outputs so that each see 16 ohms?
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Mesa Boogie Roadster 2x12 combo
Peavey Impact 1
LTD MH350=FR
Cmatmods analog chorus, phaser, tremoglo, and deeelay
Vox Time Machine
Crybaby 535Q

Cmatmods.com
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Old 03-21-2014, 05:25 AM   #4
Offworld92
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Oh oh oh I see. Yeah that's frustrating.

Why did they do that? Who the hell uses, or who even makes 8 ohm cabs?

16 ohm cabs should just be the universal standard to avoid this. 112, 212 and 412 can all easily be wired to be 16 ohms. Smaller numbers, not so much.

Sorry, free bump and hope someone else has another solution.
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Old 03-21-2014, 05:31 AM   #5
bluestratplayer
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I really believe that hot plate will work. It pretty much says insert 8 ohms, 1 output use 8 ohms cab, 2 outputs use 2 16 ohm cabs. Just really want to make sure I'm understanding that correctly from the hot plate manual I found. And I want to see if there are better ways of doing it. Curse the 2x12 being the same amount as the head and it was closed back so I figured hey getting a 2x12 mesa cab pretty much for free going combo. Now this. Still worth it even if I cant hook two cabs up though.
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Mesa Boogie Roadster 2x12 combo
Peavey Impact 1
LTD MH350=FR
Cmatmods analog chorus, phaser, tremoglo, and deeelay
Vox Time Machine
Crybaby 535Q

Cmatmods.com
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Old 03-21-2014, 05:32 AM   #6
bluestratplayer
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II. AS A POWER ATTENUATOR TO TWO SPEAKER CABINETS:
Same as above, except connect cables from both speaker outputs on the Hot Plate to your
two speaker cabinets. These output jacks are wired in parallel, so if both speaker outputs
are being used, the 2Ω Hot Plate would be needed for two 4Ω speaker cabinets, the 4Ω
Hot plate for two 8Ω cabinets and the 8Ω Hot Plate for two 16Ω cabinets.
IMPORTANT: WHEN USING BOTH SPEAKER OUTPUTS FROM
THE HOT PLATE, THE TWO SPEAKER CABINETS SHOULD HAVE THE SAME
IMPEDANCE AS EACH OTHER, AND THAT IM PED ANCE SHOULD BE DOUBLE THE
IMPEDANCE OF THE HOT PLATE.

from the thd manual if it helps you guys help me.
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Mesa Boogie Roadster 2x12 combo
Peavey Impact 1
LTD MH350=FR
Cmatmods analog chorus, phaser, tremoglo, and deeelay
Vox Time Machine
Crybaby 535Q

Cmatmods.com
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Old 03-21-2014, 07:09 AM   #7
Cathbard
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You need two 16 ohm loads with the 8 ohm hotplate. So rewire the 4 ohm 4x12 to be 16 ohm. It will be four 16 ohms in parallel atm so rewire them to series/parallel and there's your second 16 ohm load.
Plug both into the hotplate and use 8 ohm on the amp.
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Old 03-21-2014, 02:12 PM   #8
bluestratplayer
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Awesome thanks cath. I don't have the cab yet just the combo but now I know how to hook it up.
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Mesa Boogie Roadster 2x12 combo
Peavey Impact 1
LTD MH350=FR
Cmatmods analog chorus, phaser, tremoglo, and deeelay
Vox Time Machine
Crybaby 535Q

Cmatmods.com
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Old 03-21-2014, 02:45 PM   #9
dspellman
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If you have four 16-ohm speakers in a 4x12, wire each side in series and then wire the two sides together in parallel (or vice-versa) to get a 16-ohm cabinet. If you have four 8-ohm speakers in your 4x12, you'll do the same to get an 8-ohm cabinet. You can wire four 16-ohm speakers in parallel to produce a 4-ohm cabinet.

Generally, a tube head will expect to see UP TO a pair of 8 ohm cabinets (full stack), which will result in an 4 ohm impedance presenting itself to the output transformer. Generally, you don't want a lower total impedance with a tube amp (very few are stable at 2 ohms).

Last edited by dspellman : 03-21-2014 at 02:46 PM.
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