S1-45 - adding an extension cab

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WildBillMojo
Posts: 36
Joined: Sun Jul 17, 2011 12:00 am
Location: Australia
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Mon May 28, 2012 4:39 am

Hi,
I'm really happy with my S1-45, which I have been gigging with for a year or so. I recently unplugged the internal speakers and wired it to an Orange (sorry for swearing on this site!) 212 Closed Back - what a difference. Amazing mid range punch and a tight low end.
So what I really want is to run both the internal speakers and an external.
The only problem is impedance matching. The internal ones are 8Ohms, the external cab only comes as a 16Ohm option. So can I run these together and if so what impedance setting should I set-up on the amp?
Thanks in advance.

IM4Tone
Posts: 505
Joined: Sun Aug 07, 2011 12:00 am
Location: Emporium, PA

Mon May 28, 2012 6:31 am

WildBillMojo wrote:Hi,
I'm really happy with my S1-45, which I have been gigging with for a year or so. I recently unplugged the internal speakers and wired it to an Orange (sorry for swearing on this site!) 212 Closed Back - what a difference. Amazing mid range punch and a tight low end.
So what I really want is to run both the internal speakers and an external.
The only problem is impedance matching. The internal ones are 8Ohms, the external cab only comes as a 16Ohm option. So can I run these together and if so what impedance setting should I set-up on the amp?
Thanks in advance.
No, there is no correct way to run them both together. An 8 ohm load paralleled w/ a 16 ohm load yields 5.3 ohms total impedance. Probably (I said probably, but not recommended) plugging in both the internal speakers plus the extension cab and setting the selector to 4 ohms would not damage the amp, but the distribution of the power (wattage) would be inverse to the two impedances, i.e. the internal speakers would get 2/3 of the amp's power, and the extension cab the other 1/3. I don't imagine that would distribute the sound to your liking, but if you are inclined to take risks (probably not a large one), you could try it out.

I'm going to assume that the internal speakers are each 16 ohms wired in parallel to yield your stated 8 ohms. If so, you could disconnect one internally yielding an impedance of 16 ohms, then add the external cab (also 16 ohms) and set the selector to 8 ohms.....But that would utilize only 3 of the four speakers. Alternately, if the two speakers in the ext. cab are 8 ohms each wired in series, you could use only one coupled with the two internal speakers and set the selector switch to 4 ohms (two 8 ohm loads in parallel).

Other than speaker replacement, those are the only options I can think of.

WildBillMojo
Posts: 36
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Location: Australia
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Mon May 28, 2012 6:39 am

Thanks man,
I suspected so. Looks like I may have to get me the S1 head instead :)
More gear (sigh.....)

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Bigsmudger
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Location: Bristol, England

Mon May 28, 2012 2:22 pm

My experience with an ext. cab and the S1-45.

I got a custom 2x12 Zilla cab with 8 ohm V30's in, wired in series to give a 16 ohm cab.

Asked Blackstar - they said the only way to use that cab with my S1 speakers was to wire the speakers in parallel
to give the cab 4 ohms, then select the 4 ohm option on the back of the amp.

I did that - meant resoldering 2 wires in the cab. Used it at a gig and nothing went bang :lol:
They said to turn off the amp before using the impedance selector.


IM4Tone
Posts: 505
Joined: Sun Aug 07, 2011 12:00 am
Location: Emporium, PA

Mon May 28, 2012 3:04 pm

Bigsmudger wrote:My experience with an ext. cab and the S1-45.

I got a custom 2x12 Zilla cab with 8 ohm V30's in, wired in series to give a 16 ohm cab.

Asked Blackstar - they said the only way to use that cab with my S1 speakers was to wire the speakers in parallel
to give the cab 4 ohms, then select the 4 ohm option on the back of the amp.

I did that - meant resoldering 2 wires in the cab. Used it at a gig and nothing went bang :lol:
They said to turn off the amp before using the impedance selector.
Interesting.....the internal speaker load of 8 ohms wired in parallel w/ the ext. cab load of 4 ohms yields an overall impedance of 2.7 ohms mismatched to the 4 ohm selector. That's a 1.3 ohm under mismatch versus the 1.3 ohm over mismatch for using the cab "as is" @ 16 ohms. So, I guess B* is saying that an under mismatch is preferred versus an over mismatch of the same magnitude.

I'm very curious as to your perception on how the sound volume was distributed between the combo and the extension cab since the cab had 1/2 the impedance of the combo. Did it seem as if the ext. cab was at a significantly higher volume?

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Bigsmudger
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Location: Bristol, England

Mon May 28, 2012 5:49 pm

To be honest I've only used it once and at a large venue with shocking acoustics and a very narrow stage.
It was like a sports hall type of thing, so everything just bounced off the walls.

The cab was bought for my Marshall head so it's not as wide as the S1 combo, so I had to stack the cab on top.
I had to stand so close that all I could hear was the cab so couldn't really tell if one was any louder than the other.
We've been miked up since so I've not needed it.

Got a few open air gigs coming up so I'll try it again and report back.

WildBillMojo
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Mon Aug 06, 2012 11:28 pm

Thanks guys.
In the end I've just bought the S1-212 extension cab - i'm picking it up later. Its an 8Ohm cab so what do I set the impedance selector to?
Thanks again.

IM4Tone
Posts: 505
Joined: Sun Aug 07, 2011 12:00 am
Location: Emporium, PA

Tue Aug 07, 2012 3:50 am

WildBillMojo wrote:Thanks guys.
In the end I've just bought the S1-212 extension cab - i'm picking it up later. Its an 8Ohm cab so what do I set the impedance selector to?
Thanks again.
Internal speaker load of 8 ohms paralleled with an external cabinet load of 8 ohms yields an overall load (as seen by the amp) of 4 ohms.

WildBillMojo
Posts: 36
Joined: Sun Jul 17, 2011 12:00 am
Location: Australia
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Tue Aug 07, 2012 3:54 am

Thanks man.

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