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 Post subject: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 1:22 pm 
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I have a Twin Reverb '65 Reissue and am wanting to connect an external cab. My other cab is a Vox 212BN with these specs"

2 - 12" Vox GHS12-30 speakers @ 8 ohms
It says maximum input 60w RMS at 16 ohms

The Fender Twin manual says this about the Ext. Speaker hookup - EXTERNAL SPEAKER JACK - Plug-in connection for an external speaker. This jack is wired in parallel with the MAIN SPEAKER JACK {E}. A total speaker impedance load of 4-ohms should be used to avoid damage to the amplifier.

Am I ok to use this cab through the external speaker jack?

Thanks,
Derek


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 1:49 pm 
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I interpret the specs of your Vox cab to say that is contains two 8 ohm speakers rated at 30 watts each and that they are wired in series for a total resistance of 16 ohms and the combination can handle 60 watts.

The TRRI has two 8 ohm speakers wired in parallel for a total of 4 ohms load.

Connecting your Vox cab to the TRRI would present a total load of 3.2 ohms. I don't recommend it.

If you rewire the TRRI speakers to a series connection (16 ohms total) adding the Vox cabinet would result in a total impdeance of 8 ohms which may be workable. However, without the cabinet connected, the total load would be 16 ohms from the two TRRI speakers. Also not recommended.

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 1:54 pm 
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Rewire your Vox cab in parallel instead of series for a 4 ohms impedance.


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 2:03 pm 
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Thanks guys....

How do I rewire the Vox in Parallel? I suppose I can google this to get a better understanding.

Thanks,
Derek


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 2:57 pm 
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Diagrams are everywhere, here's one:

http://www.bustedgear.com/faq_Speaker_wiring.htm


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 3:33 pm 
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atolleter wrote:
Rewire your Vox cab in parallel instead of series for a 4 ohms impedance.


Really bad idea. Then the total load on the TRRI would be 2 ohms. A definite no-no.

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 3:34 pm 
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dschaaf wrote:
Thanks guys....

How do I rewire the Vox in Parallel? I suppose I can google this to get a better understanding.

Thanks,
Derek


Don't do it. See my second post.

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 3:49 pm 
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atolleter wrote:
Diagrams are everywhere, here's one:

http://www.bustedgear.com/faq_Speaker_wiring.htm


There is no way to wire four 8 ohm speakers and come up with 4 ohms total.

If my math is correct:

Four speakers in parallel = 2 ohms

Four speakers in series = 32 ohms

Two series speakers in parallel with two parallel speakers = 3.2 ohms

Two series speakers in parallel with two series speakers = 8 ohms

Three speakers in series in parallel with one speaker = 6 ohms

Three speakers in parallel and in series with one speaker = 11 ohms

Any other combinations?

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 4:04 pm 
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Thanks Bill!


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 4:22 pm 
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bluesky636 wrote:
Connecting your Vox cab to the TRRI would present a total load of 3.2 ohms. I don't recommend it.


This will work safely.

I regularly run my TRRI at 2.6 ohms (internal speakers paralleled with an 8-ohm external load) and have done so for years without problems. Less than 2.6 ohms though is whistling past the graveyard IMO.

Arjay

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 5:46 pm 
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Retroverbial wrote:
bluesky636 wrote:
Connecting your Vox cab to the TRRI would present a total load of 3.2 ohms. I don't recommend it.


This will work safely.

I regularly run my TRRI at 2.6 ohms (internal speakers paralleled with an 8-ohm external load) and have done so for years without problems. Less than 2.6 ohms though is whistling past the graveyard IMO.

Arjay


I was being a little over cautious. It's probably the best case scenario since nothing else is close.

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 8:12 pm 
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Thanks guys...much appreciated! :)


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Tue Jan 18, 2011 8:59 pm 
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You're very welcome. Good luck. :D

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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Thu Mar 17, 2011 10:33 am 
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Question...
I want to run my tiny terror head through my older Twin Reverb's speakers. I'm going to get an AB box to switch between the fender clean channel and then use the tiny terror for distortion.
Does anyone see any foreshadowed problems doing that? I'm new to the whole A/B situation.


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 Post subject: Re: external cab for Twin Reverb '65 RI
PostPosted: Thu Mar 17, 2011 3:54 pm 
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capeotter wrote:
Question...
I want to run my tiny terror head through my older Twin Reverb's speakers. I'm going to get an AB box to switch between the fender clean channel and then use the tiny terror for distortion.
Does anyone see any foreshadowed problems doing that? I'm new to the whole A/B situation.


Its not polite to hi-jack someone else's thread.

In any case, if you are planning on connecting both amp's speaker outputs to the TR's speakers at the same time, you will blow up both amps as soon as you power them up. Should be interesting.

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