Advice needed re speaker for Acoustic 450

nrand · #1 08-21-2011, 07:55 AM

My daughter has an Acoustic 450 head I gave her some years ago and she needs a single speaker cabinet for it. Its not a great head, granted but money is tight so I advised her to hang on to it and get a cabinet in the short term.
As far as I am aware these heads push 170W into 4 ohms, yet the vast majority of the speaker cabs available are 8 ohms.
I am not strong on speaker theory, so can someone please tell me if such a mismatch is ok and/or what to expect?
Thanks

SurferJoe46 · #2 08-21-2011, 09:38 AM

In oversimplified logic here - the following is a rule-of-thumb.

Using an amp that is CAPABLE (the operative word here) of working at a load of 4 Ohms is OK if you run it into a higher Ohm cabinet.

4 Ohms is it's happy zone.
8 Ohms would be an easy job for the amp.
2 Ohms would make it unhappy.

Never have an amp drive something BELOW it's rated Ohm capacity.

Example----> run a head that's rated at 8 Ohms at 16 Ohms and really all that happens is you lose Wattage since the amp is coasting along at 1/2 it's normal work load.

But run an amp rated at 8 Ohms into a 2 or 4 Ohm cab and you might let the smoke out of the amplifier. Escaping smoke is never good.

She will experience a loss of perceived power (loudness) but the amp is fine at that.

We ARE talkin' solid-state here - right? If it's a tube amp or maybe even a hybrid (some tubes / some transistors) then all bets are off.

Cirk · #3 08-21-2011, 09:47 AM

There are some 4 ohm cabs out there. Just have to look around. What's the basic idea of what you would like, and how much would you like to pay for it? I'm sure the fine folks here would be glad to help. Also, check out the used gear for sale section here. If you don't find what you need, then post and ad in the wanted section.

Cheers!

RickenBoogie · #4 08-21-2011, 10:03 AM

An 8 ohm cab will do fine, and leave the door open to add another 8 ohm cab later, if needed. A 4 ohm cab will work, too, but if it's a single spkr cab, you will leave any future expansion right out. If you do get a 4 ohm cab, I'd be sure it was at least a 2x12.

nrand · #5 08-21-2011, 03:21 PM

Quote:

Originally Posted by Cirk

There are some 4 ohm cabs out there. Just have to look around. What's the basic idea of what you would like, and how much would you like to pay for it? I'm sure the fine folks here would be glad to help. Also, check out the used gear for sale section here. If you don't find what you need, then post and ad in the wanted section.

Cheers!

Thanks for this and other comments. Size and weight are currently an issue as she does not have a car. Daughter was using a large box with 2 speakers I had given her but it was too heavy for her - having just finished college and poor - I suggested a single speaker cab for the time being until she starts gigging. She is in Melbourne and does not have much to spend in the short term, so I have been looking for used gear.