Speaker impedance question

[Mudpup]

Have a Peavey 2x10 combo running a 4ohm internal speaker at 350watts with the capability for an extension speaker at 4 ohms to take it down to 2 ohms and 500 watts.

Would i be able to add an 8 ohm cab without damaging the amp? Just want to biggen up the sound with a 12" cab and theyre not easy to find at 4 ohms. Dont need the full 500 watts really.

Any thoughts?

[xgsjx]

Yup.

Although it might be not as loud as the combo.

[icastle]

Sort of.

You'll achieve 2.67Ω if you add an 8Ω speaker, so electronically safe.
From a practical point of view though, I don't think you'll hear the difference.

[BILL POSTERS]

Like Icastle said, you could do it, but you'll probably hardly hear a difference.
No harm in trying it though eh ?

[aldude]

I think you might well be able to hear the difference, perhaps not in volume but certainly in tone.

I used to have a Trace Elliot 2x10 combo, it never really had a great bottom end. I suspect they reduced the size of the thing both to save weight and also ensure they had space to fit the amp section in. As a result the tuning was probably a bit off.

I got a 15" extension cabinet and the bottom end was back! So I say go for it.

[StraightSix]

If you have 350W as it stands, and 500W at 2ohms, you will probably only get ~400W @ 2.67ohms which isn't much of an increase.

The extra speaker will push some more air though and if you stack the combo and 1X12 cab, the speakers will be nearer ear level so you may like that improvement - I would try it out before parting with any cash.

If you can, look out for a 2X12 @ 4ohm - they are far more common and you will definitely get an improvement.

[StraightSix]

[quote name='aldude' timestamp='1330939084' post='1564871']
I used to have a Trace Elliot 2x10 combo...I got a 15" extension cabinet and the bottom end was back! So I say go for it.
[/quote]

Keep in mind that Trace Elliot amps generally provide maximum power with a 4ohm load so adding your 1X15 would have probably doubled your available power - that is very noticeable.

Another quick thought for the OP - try and find a 4ohm 2X10 cab as it will match up better with your existing 2X10 arrangement.

HTH

[Lozz196]

Volume-wise probably not too noticeable, but size of sound-wise, it should add more depth.

[Mudpup]

Cheers guys
It was more for adding some thump and headroom rather than outright volume

[melando]

In sound pressure level terms I think you should expect and increase of around 4.5dB. That should be easily noticable, and the effect will be enhanced because you'll have two cabinets working together giving a bigger source size. Definitely worth trying.


For those interested, my calculation runs as follows:

Internally, you probably have 2 x 8 ohm 10" units in parallel giving a 4 ohm load and an output of, let's say, 0dB.

Adding another identical 2 x 10" speaker system will give +6dB (2.0 in linear units) in sound presure level and will halve the impedance to 2 ohms.

A single 8 ohm 10" speaker will have a relative output of -6dB SPL (or 0.5 in linear units) compared to the 2 x 10 system. Adding this in parallel with the internal 2 x 10" should increase to output by 3.5dB SPL. (or 1 + 0.5 = 1.5 in linear units)

A equivalent 12" driver should have a dB or so of extra output than a 10" so I would expect that adding a 1 x 8ohm 12" system will increase the output by around 4.5dB.

[xgsjx]

I wouldn't have thought it would have made as much a difference as that. Part due to the fact that it's getting pushed by 1/2 the power that the 2x10 combo is & although it will make some sort of a difference, would it not depend on the sensitivity & so on of the ext cab?

Edited to tidy up grandma

Edited March 11, 2012 by xgsjx

[melando]

[quote name='xgsjx' timestamp='1331505161' post='1574002']
I wouldn't have thought it would have made as much a difference as that. Part due to the fact that it's getting pushed by 1/2 the power that the 2x10 combo is & although it will make some sort of a difference, would it not depend on the sensitivity & so on of the ext cab?

Edited to tidy up grandma
[/quote]

The extension cabinet will indeed see half the power that the internal 2 x 10" system does as, being 8 ohm instead of 4, it will only draw half the current. The acoustic output you get for that though, is significant, it's around half what you are getting from the 2 x 12", around -6dBspl. Adding them together, 0dB + -6dB = +3.5dBspl. Add a dB more because a 12" unit is generally a little more sensitive than a 10" (as I mentioned above) and you get around +4.5dBspl.

The 2 x 10" system will sound louder than the 1 x 12" extension cab so the the bulk of the sound will still appear to be coming from that, but the total will be 4.5 dB louder - which is the increased headroom desired. And the amplifier has the power output to deliver this.

[StraightSix]

[url="http://basschat.co.uk/topic/170609-selling-trace1215-combo-and-peavey-210tx/page__pid__1574355#entry1574355"]http://basschat.co.uk/topic/170609-selling-trace1215-combo-and-peavey-210tx/page__pid__1574355#entry1574355[/url]

Mudpup - this has just showed up in the For Sale section.