Two thieles and an open back all at the same time w/ a MKIV?

[MusicManJP6]

I am unsure of how the amp perceives loads at the moment, so I have a question. How can I (if at all) use both my thiele cabs AND an open back cab? They are all 3 8 ohm 1x12 cabs. It would seem that I should only use 2 at a time using the 4 ohm outs on my Mark IV. BUT, would it be safe to use the 8 ohm out for the open back as well? I have not tried it and would rather not until I know if it is OK/safe to do so.

Thanks for the help guys!

-Adam

 

[Schmoog]

you would need to use a series box on two of the cabs so you would present the amp with an 8 ohm load and a 16 ohm load into the two 4 ohm outputs. the 4 ohm outputs will parallel the 16 ohm and 8 ohm loads, and present the amp with somewhere in the vicinity of a 12 ohm load. you shouldn't use all three outputs at once.

 

[MusicManJP6]

I didn't think it would be wise to use all three outputs. Is there a particular brand of series box I need to look for? Thanks.

 

[Schmoog]

I make mine. I made 3 in 30 minutes for about 20 bucks. I can send you a wiring diagram for them if you'd like....

 

[Schmoog]

I make mine. I made 3 in 30 minutes for about 20 bucks. I can send you a wiring diagram for them if you'd like....

Or, I can build you one of course....

 

[Boogiebabies]

I run the 8 Ohm Thiele EV in the 4 ohm tap, an 8 ohm G-Flex 2X12 in the 4 ohm and an 8 ohm Mesa Recto 4X12 in the 8 Ohm tap. The 8 ohm load is a direct match for the 8 Ohm load. The two 8 ohm speakers cabs make a 4 ohm load using both 4 ohm taps. It only gets dicey if you try to use two 4 ohm speakes in the 4 ohm jacks. Since it halves the impedence running 2 ohms is not good. Running two 8 ohm loads through the 4 ohm taps yields a 4 ohm load, so it's actually a perfect match. Even if I run the Recto cab and 2X12, they are also at a 4 ohm load in the two 4 ohm taps.

 

[phyrexia]

I run the 8 Ohm Thiele EV in the 4 ohm tap, an 8 ohm G-Flex 2X12 in the 4 ohm and an 8 ohm Mesa Recto 4X12 in the 8 Ohm tap.

All at once, you say?

 

[MusicManJP6]

I run the 8 Ohm Thiele EV in the 4 ohm tap, an 8 ohm G-Flex 2X12 in the 4 ohm and an 8 ohm Mesa Recto 4X12 in the 8 Ohm tap.

All at once, you say?

I am curious as well! That contradicts Schmoog's original post of not using all three outputs at the same time...

Schmoog: I might take you up on building me a series box. How much would you charge for shipping and all?

 

[Schmoog]

probably like 25 shipped or so. I have two that I made for someone who changed his mind so you can have one of those, I just gotta paint them.

 

[MusicManJP6]

What are the dimensions of the boxes you made?

 

[Schmoog]

my most current batch were just build in small project boxes from radio shack, there probably 2 inches long by 4 inches wide. But I'll put em into whatever enclosure you want. I built 2 isolated series boxes into one Hammond 1590DD enclosure for one gentleman. If you want them in a metal enclosure or, like the last gentleman want two in one box. Just let me know what you want. I have been building custom footswitches, Tip/Ring switches and other custom pedals for a couple years now. so chances are, whatever you need, I've either built for myself or someone else. I just finished a pedal for a gentleman yesterday that had a guitar with regular mag pups and a piezo. he wanted to split the outputs so he could send mags to an amp, and the piezo to the board, and also be able to footswitch the active output in one unit. I built him a footswitch with a TRS input, two mono outputs. The footswitch would crossfade very quickly (20 ms) between the outputs, then mute the intended inactive output to prevent channel bleed. Its pretty nifty.

 

[Schmoog]

Oh, taking the opportunity for the shameless plug, I also build custom head cabinets, and speaker enclosures.

 

[daveg62]

Maybe I'm wrong in thinking this but if you run the two 8 ohm thieles in series you get 16 ohms. And the combo speaker is 8 ohm. How does the difference affect the sound coming out of the combo speaker compared to the thiele cabs? Wouldn't the thieles be quieter because of the higher ohms. Like I said maybe I'm wrong in thinking like this, I'm not sure.

 

[Buddy]

I run the 8 Ohm Thiele EV in the 4 ohm tap, an 8 ohm G-Flex 2X12 in the 4 ohm and an 8 ohm Mesa Recto 4X12 in the 8 Ohm tap. The 8 ohm load is a direct match for the 8 Ohm load. The two 8 ohm speakers cabs make a 4 ohm load using both 4 ohm taps. It only gets dicey if you try to use two 4 ohm speakes in the 4 ohm jacks. Since it halves the impedence running 2 ohms is not good. Running two 8 ohm loads through the 4 ohm taps yields a 4 ohm load, so it's actually a perfect match. Even if I run the Recto cab and 2X12, they are also at a 4 ohm load in the two 4 ohm taps.

+1
And Daveg , with that amount of cone moving air , I would'nt worry about spl , Tinnitus , maybe :lol:

 

[Schmoog]

Maybe I'm wrong in thinking this but if you run the two 8 ohm thieles in series you get 16 ohms. And the combo speaker is 8 ohm. How does the difference affect the sound coming out of the combo speaker compared to the thiele cabs? Wouldn't the thieles be quieter because of the higher ohms. Like I said maybe I'm wrong in thinking like this, I'm not sure.

no. because the whole lot of speakers get paralleled inside the amp, so it balances out. I used to run my head, a thiele, and 2 1x15 cabs and they balanced out nicely.

 

[phyrexia]

I am officially calling BB out: Are you running two 8 ohm cabs in your 4 ohm outputs and one 8 ohm cab in your 8 ohm output, simultaneously?

 

[daveg62]

I am officially calling BB out: Are you running two 8 ohm cabs in your 4 ohm outputs and one 8 ohm cab in your 8 ohm output, simultaneously?

Yes I'm a bit confused about this. I'm thinking of adding another theile cabinet to my Mark III and now I don't know if I need to series the two theiles together or not.

 

[MusicManJP6]

I have heard from several reliable sources now that you should not run 3 cabs using all 3 outputs on the MKIV.

Schmoog: PM sent.

 

[ursinus]

I have heard from several reliable sources now that you should not run 3 cabs using all 3 outputs on the MKIV.

Schmoog: PM sent.

That is what I understand too. Maybe BB knows something about the primary winding of the transformer that we don't? I know that the secondaries (the 8ohm and 4ohm outs) can take it, but the current load doubles on the primary and the the tubes (2 ohms at the secondary).

I wouldn't try myself. I run 3 cabs with my combo, but I run 3-16 ohm cabs in parallel. The combo speaker plugged in to the 4 ohm out and the extension speaker plugged in to the other 4 ohm out and the Theile plugged into the parallel out of the extension speaker. Total load is about 5-6 ohms. Well whithin the acceptable.