Max number of cabs connected to head

[james condino]

"Can you post the exact model of your AI for verification?"

Acoustic Image Focus, series III combined with a set of ACME B1s

 

[charlie monroe]

"Can you post the exact model of your AI for verification?"

Acoustic Image Focus, series III combined with a set of ACME B1s

James, the Focus 1 version of that amp is single channel, the R2 is dual.

It appears as though all output is through common speakon connectors. If you do have an R2 and either channel is used, the same speakers receive signal.

Your cabs should present a 4ohm load regardless of which of the 2 amps you own.

http://www.acousticimg.com/docs/Manual-amp heads sIII.pdf

The manual could be written better, but I guess they were saving trees

 

[agedhorse]

thats if you connect all the speaker together and run from a mono bridged output...many bass amps have a seperate left and right or A and B speaker output...for running stereo output......each speaker connects to its own channel and the ohm rating doesnt change...engage the bridge mono switch..the outputs of the two channels are summed together..you only have one speaker cable coming out of the amp that goes to one speaker...and you run a speaker cable from speaker cab 1 to speaker cab 2...now you have affected the impedance of the cabinets..essentially cutting it in half...wired like this..two 8 ohm cabs become 4 ohms..

The amp the OP is asking about is a single output channel, no bridging. No need to confuse things here.

So you're saying 3 four ohm cabs in parallel is also 2.67 ohms? I don't really see how you "skip straight to 8/3".

No, for identical 4 ohm cabinets it would be 4/3

whether you use seperate channels on an amp or bridge the channels together does matter...If I use channel A and B seperately on my ampeg SVT pro 4 and have a 4 ohm cabinet at each channel..its a 4 ohm system...if I bridge the two channels together..and jump the speakers together with a speaker cable..I am at a bridge mono load...it is now a 2 ohm system...the amp matters....all amps are different...you cant do this with all amps..but you can with amps that have stereo options...which essentially are two independent power sources in the amp for each channel...that can be used independently or together...running the channels independently...it is 4 ohms...bridging the channels is 2 ohms..

It doesn't matter at all if the amp does not have to output channels and does not bridge.

In the case of the SVT 4 pro, don't bridge it (and just about all other bridgeable amps) into 2 ohms. Not if you want the amp to survive.

 

[HolmeBass]

No, for identical 4 ohm cabinets it would be 4/3

I know that is the simplification, I think it's worth using the actual formula I originally posted - the real formula - just in case you have a 610 (usually 5.3 ohms nominally) or want to compute the value directly for one 8 and one 4.

I feel simplifications and shortcuts should only be used by those already well-versed in the formally correct way to compute it. Only they know the restrictions and special cases where the simplification actually works. The OP itself is a bit of a testament to that, isn't it?

 

[GreyBeard]

Hi everybody,
I have a mesa boogie subway d800, and several cabs, eden 115, eden ex112, a pair of ampeg svt 210 av, and i was wondering if i could connect the pair of ampeg AND the eden 115 (all 8 ohm each) with the d800.
I know it could be a stupid question, and i beg your pardon, but i found nothing about it on the web and i haven't the skills to resolve it by myself, so i ask if someone can help me.
Thank in advance

3x8 ohm cabs makes 2.6 ohms. I believe your d800 can be switched to work at 2 ohms so the answer is yes.

 

[agedhorse]

I know that is the simplification, I think it's worth using the actual formula I originally posted - the real formula - just in case you have a 610 (usually 5.3 ohms nominally) or want to compute the value directly for one 8 and one 4.

I feel simplifications and shortcuts should only be used by those already well-versed in the formally correct way to compute it. Only they know the restrictions and special cases where the simplification actually works. The OP itself is a bit of a testament to that, isn't it?

Actually, I agree with this.

 

[Ed Byrnes]

You can go here: Invalid Link Removed to check the total ohmage load the combination of speakers/cabs will present to your head. 3 x 8 ohm cabs in parallel will present a 2.7 ohm total. 4 x 8 ohm cabs gets you down to 2 ohms. If you head can't handle a 2 ohm load you can't do this

 

[okcrum]

AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

the last place you'd look

 

[Old Garage-Bander]

I know that is the simplification, I think it's worth using the actual formula I originally posted - the real formula - just in case you have a 610 (usually 5.3 ohms nominally) or want to compute the value directly for one 8 and one 4.

I feel simplifications and shortcuts should only be used by those already well-versed in the formally correct way to compute it. Only they know the restrictions and special cases where the simplification actually works. The OP itself is a bit of a testament to that, isn't it?

Actually there is a simple formula for two cabs of different impedance as well.
Product/Sum.
8x4 = 32, 8+4 = 12, 32/12 = 2.67 (rounded).

I agree that it is important to understand the math behind the process.
Ironically, those who do understand it don't need it.
Those who don't may end up getting it wrong when they try.
If getting it wrong means blowing out your amp, that can be an expensive error for the sake of showing your work.

How many -inverse of the sum of the inverses- folks also roll their own square roots?
To me it's like re-inventing the wheel all over again.
Nothing wrong with using the tools we've developed, especially for a results oriented outcome.

Should we have gone to the moon without ever using slide rules?

 

[Crimax]

Just for share the experience, i tried the combination of the couple of ampeg paired with the eden 115 xl on saturday in a gig. The place was a little square in a village near Milan, i was playing in a sort of tribute to blues brothers, 9 people total, with two sax and trumpet.
Actually i noticed just a little more bass, like there was more "air", so did the other members, but it didn't bring any significant advantage or upgrading.
I've got to say that the volume wasn't too loud, the cabs didn't suffer, and the eden cab is more middle scooped than for example an ampeg or ashdown, but as i said i notice just a little difference.
I was satisfied with the pair of ampeg, but wanted to do the experiment if someone is interested, and for the future i will stay with them, they are lighter, sound good , and the extra weight and space isn't worthwhile.