Question Connecting Cab to Combo

Rykashu · #1 01-05-2011, 11:32 PM

I have an Acoustic B200 combo amp. The amp supports 200watts @ 4 Ohms. It has 1x15inch speaker that according to the electrical diagram in the manual on page 14 is a 4 Ohm speaker. I'm considering either connecting either a 2x10" or 4x10" cab to this combo so I can get the sound of both a 15" and some 10's. I'm trying to figure out what kind of impedance would be required on the external cab to not fry the combo as well as how would this affect the wattage to each the cab and combo's internal speaker. I'm not sure what the difference would even be between the speakers being wired series or parallel. The manual on page 14 also lists a note that the speaker output is in series with the internal speaker, and to the best of my knowledge the diagram seems to support that, though I could be wrong. However, on page 9 of the manual speaker out is listed as "Two-conductor, 1/4” Speaker Output Jacks, 4 Ohms minimum load, parallel". So I can't even figure out if the speaker output is series or parallel.

Here is a link to a pdf of the manual:
http://www.acousticamplification.com...115-Manual.pdf

billfitzmaurice · #2 01-06-2011, 06:53 AM

Plug a cord into the extension jack of the amp. If it's a series jack there will be no sound from the internal speaker. Since your amp is 4 ohm rated and has a 4 ohm internal speaker that's probably the case, as a parallel jack would give too low an impedance load. Adding a second speaker with a series connection is usually not worth it.

Rykashu · #3 01-06-2011, 02:03 PM

Why is it not worth it, will the volume be lower than it could for the internal? the cab? both? How is the wattage affected by connecting in series?

Bass_Pounder · #4 01-06-2011, 02:14 PM

Quote:

Originally Posted by Rykashu

Why is it not worth it, will the volume be lower than it could for the internal? the cab? both? How is the wattage affected by connecting in series?

If you add another 4 ohm speaker to the internal one, it increases your impedance to 8 ohms (in series), which cuts your wattage by about 50%.

So, you pick up speaker area but lose output - becomes a wash.

Rykashu · #5 01-06-2011, 02:30 PM

Fair enough, maybe once the warranty runs out I'll replace the internal with an 8ohm 15", and rewire the speaker out for parallel.

Bass_Pounder · #6 01-06-2011, 02:47 PM

Quote:

Originally Posted by Rykashu

Fair enough, maybe once the warranty runs out I'll replace the internal with an 8ohm 15", and rewire the speaker out for parallel.

If your looking for an amp that can "grow" for different uses, your best bet is to sell it and start over.

RickenBoogie · #7 01-06-2011, 05:12 PM

+1 enjoy the amp as it is for now, and step up to something better when you can. Those Acoustic combo's sound pretty good for the money, but the series spkr jack is a deal killer for me. Changing the speaker would also be a waste of money, just upgrade altogether, later on.

SurferJoe46 · #8 01-06-2011, 07:25 PM

Quote:

Originally Posted by RickenBoogie

+1 enjoy the amp as it is for now, and step up to something better when you can. Those Acoustic combo's sound pretty good for the money, but the series spkr jack is a deal killer for me. Changing the speaker would also be a waste of money, just upgrade altogether, later on.

If you replace the 4Ω with an 8Ω driver, then you'd have to change the output jack too to a parallel setup.

Just note that the next Acoustic combo up in size is the B-450 with a 600Watt amp and it can go to 2Ω, so you can actually add two more cabs to it if you want for a lot more power - and unfortunately a little more money.