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Post subject: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Wed Dec 20, 2017 10:53 am
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Hey everyone i was wondering if it would be possible to unplug the main speaker connection in my Blues Deluxe reissue (leaving the main speaker jack and external speaker jack open) and plugging in a 4x12 Cab which has two 8 ohm inputs. i would go from main speaker jack and external speaker jack in BDRi into the 4x12 Cab

From the BDRi specs its seems like two 8ohm load would work but im concerned that the internal speaker that comes with the BDR needs to be connected at all times.

Thanks, Cole


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Tue Dec 26, 2017 3:49 am
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You can connect the external cab on the main speaker output from the Blues Deluxe.
Forget ext output speaker jack

Tube amps must alway see a speaker


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Tue Dec 26, 2017 7:46 am
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What the manual means is that a speaker must always be connected to the jack labeled "internal speaker". It can be an extension speaker instead of the actual internal speaker.

The "internal speaker" jack is a shorting jack. If nothing is plugged in there, and you connect a cab to the "extension speaker" jack, there will be no sound and the tubes and transformer will be under extreme stress.


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Tue Dec 26, 2017 7:53 am
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The internal jack is connected to the transformer's 8 ohm tap.

The extension jack is a switching jack. When you use both jacks, the ext jack switches both jacks in parallel to the transformer's 4 ohm tap.

Two 8 ohm speaker loads in parallel are 4 ohms total. So yes, you can plug in two 8 ohm loads. The internal speaker plus an 8 ohm extension cab, or two 8 ohm extension cab, or a stereo extension cab (where both halves of the stereo cab are 8 ohms).


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Tue Dec 26, 2017 7:58 am
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Awesome! thanks for response


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Tue Dec 26, 2017 8:11 am
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So that brings us to the cab.

You're sure it's a stereo cab?

A lot of mono cabs have a pair of jacks with a single impedance listed. Those jacks are in parallel so that you can daisy-chain multiple cabs.

So if you have an amp with a single output jack (or one 4ohm jack, one 8 ohm jack, and one 16ohm jack) you can run one speaker cable from the amp to the first cab, and then another speaker cable from the first cab to the second cab.

If you have a mono cab like that, you need to disconnect the amp's internal speaker and run one speaker cable from the amp's internal speaker jack to either input on the cab.

(Or use both the internal speaker plus the cab.)

Stereo cabs are always clearly labeled "stereo". They almost always have switching options to allow you to run them either mono or stereo.

Either an actual switch, or switching jacks with labels that say something like "use this jack for 16ohms mono or these two jacks for 8ohm stereo".

Marshall stereo cabs use switches plus switching jacks to give you the options of 4ohms mono, 16ohms mono, or 8ohms stereo.

If you do indeed have a stereo cab with two 8ohm sides, then yes two cables from the amp to the cab.


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Thu Dec 28, 2017 8:54 am
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yeah it is a behringer bg412f it has a mono/stereo switch on the back


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Post subject: Re: 4x12 Cab replacing internal and external speaker in BDRi
Posted: Thu Dec 28, 2017 10:13 am
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jacks374 wrote:
yeah it is a behringer bg412f it has a mono/stereo switch on the back


That will work then. Two speaker cables from the amp to the cab's left&right 8 ohm inputs.

There's also a way to safely "trick" the BDRI into working with a single 4 ohm load. If your 412 lets you select 4 or 16 mono and you wanted to just use 1 speaker cable you could do that.

Do be sure to use speaker cables, not instrument cables.

I once disconnected the internal speaker on a Deluxe Reverb and accidentally plugged it back into the ext jack instead of the internal jack. Thanks to the shorting jack Fenders will usually survive that for a little while.

But it's not good to do. So always be sure that when you disconnect the 412 you hook the internal speaker back up to the internal jack.


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