Speakers' Role in Determining Amp Wattage

andrewalexander · #1 04-02-2011, 11:52 AM

So my friend just gave me a Sunn Beta 205 bass cab. It's a 2x15 enclosure. I plan on using it as an external speaker for my SWR Redhead. However, the amp states that its "continuous power" (a term with which I am unfamiliar) is 100W. My Redhead puts out 350W of power. I'm wondering if replacing the speakers in the Sunn could give it more wattage. But then, the problem is that I'm replacing vintage speakers from the 70's with modern speakers made with cheaper materials.

So I suppose I'm asking if changing the speakers in the cab would change its wattage. And if not, or if that is a bad idea, what the best way to use this cab with my Redhead would be.

Downunderwonder · #2 04-02-2011, 12:02 PM

Possibly the Sunn is rated more truthfully than modern gear. You want to see what its nominal impedance is before running the amp into it.

Absolutely you could change drivers for more power handling. Someone will probably have done it with your cab. Might help if you take a photo.

Depending on the impedances the amp will power up your Sunn cab with the same, twice or half the power that the combo's own speakers are dealing with.

Possibly you may benefit from rewiring the Sunn in series to protect the drivers from the Redhead. If it was me I'd get a vintage valve amp and play that thru it instead.

dmusic148 · #3 04-02-2011, 12:02 PM

Just use it as-is. The cab isn't really worth buying new speakers for. As far as wattage is concerned- it's really not worth getting into. Just listen for signs of stress and back off if needed. Chances are the cab will handle the output of the Redhead just fine.

Downunderwonder · #4 04-02-2011, 12:04 PM

btw, in the final analysis you will have to use your ears to judge if you are overpowering the Sunn.

Downunderwonder · #5 04-02-2011, 12:05 PM

I dunno what the Redhead is good for impedance wise. Putting a 4ohm extension cab on it could blow the amp and the speakers at the same time so go carefully.

dmusic148 · #6 04-02-2011, 12:08 PM

Quote:

Originally Posted by Downunderwonder

I dunno what the Redhead is good for impedance wise. Putting a 4ohm extension cab on it could blow the amp and the speakers at the same time so go carefully.

Yeah, there is that problem. Unless you know what impedance the cab is, and what the Redhead will handle, use the 2x15 alone, without the Redhead speakers.

andrewalexander · #7 04-02-2011, 01:24 PM

Well, the impedance isn't issue. Both the Redhead and the Sunn have an impedance of 4 ohms. Again, I'm just more worried about pushing too much wattage into the cab. However, I just tested it with 450 watt solid state head, and with the volume on the head at about 1 or 2, the cab was loud enough to shake the room. So I think, like you guys said, it's just a matter of feeling how much pressure I'm putting on the Sunn's speakers and adjusting the amp's output accordingly.

JimmyM · #8 04-02-2011, 01:28 PM

Quote:

Originally Posted by andrewalexander

Well, the impedance isn't issue. Both the Redhead and the Sunn have an impedance of 4 ohms.

no, you have an issue. if the cab in the redhead is 4 ohms and the sunn cab is 4 ohms, they will combine for 2 ohms, which is out of the safe operation realm of the redhead. the only way to use both together is to either disconnect the redhead's speakers and hook up the sunn instead, or use two amps, one for each cab.

Quote:

Again, I'm just more worried about pushing too much wattage into the cab. However, I just tested it with 450 watt solid state head, and with the volume on the head at about 1 or 2, the cab was loud enough to shake the room. So I think, like you guys said, it's just a matter of feeling how much pressure I'm putting on the Sunn's speakers and adjusting the amp's output accordingly.

exactly.

andrewalexander · #9 04-02-2011, 02:08 PM

Oh, sorry. The Redhead has a switch that turns the internal speakers off, and I was planning on using that. I won't need the 10's in addition to 15's. I should have specified as such.
Thanks for the advice, guys.

BassmanPaul · #10 04-02-2011, 02:51 PM

Quote:

Originally Posted by dmusic148

Just use it as-is. The cab isn't really worth buying new speakers for. As far as wattage is concerned- it's really not worth getting into. Just listen for signs of stress and back off if needed. Chances are the cab will handle the output of the Redhead just fine.

I, on the other hand, think that with more than triple the power that the old drivers are rated for that they will fail in short order.