My PA Future

Posted: Wed Nov 26, 2008 6:39 am

I would suggest going digital for the cross-over. This will also provide you with EQ, time-alignment delays, limiters and other useful stuff.

Shop around for a DBX Driverack PA, thats the cheapest I've seen: http://www.dbxpro.com/pa/pa.htm

Posted: Wed Nov 26, 2008 6:41 am

double post Rolling Eyes

Posted: Wed Nov 26, 2008 11:15 am

Ok, thanks, I think I will be going with the Ashly.

How do you guys feel about the DBX DriveRack PA Processor w/RTA-M Mic?

Posted: Wed Nov 26, 2008 2:24 pm

If you get a Driverack PA you won't need a separate cross-over.

I've used several of these units to drive small systems and bi-amped wedges. Never had any problems with them.

Posted: Wed Nov 26, 2008 5:10 pm

the driverack will come a little later in the process of buyng stuff, so i will need a separate cross-over for the time being

Posted: Tue Dec 02, 2008 6:42 pm

random question but is there any way to tie 2 power amps together.

for example, if you have 2 8ohm speakers and you cant get enough power out of one amp....can you link 2 amps together to power the 2 speakers?

Posted: Tue Dec 02, 2008 10:10 pm

stealthy wrote:

random question but is there any way to tie 2 power amps together.

for example, if you have 2 8ohm speakers and you cant get enough power out of one amp....can you link 2 amps together to power the 2 speakers?

Easy. Use one amp to drive one speaker and the other amp to drive the other speaker. Common the amplifier inputs. Don't even think about paralleling the amplifier outputs.

Posted: Tue Dec 02, 2008 10:11 pm

Boswell wrote:

stealthy wrote:

random question but is there any way to tie 2 power amps together.

for example, if you have 2 8ohm speakers and you cant get enough power out of one amp....can you link 2 amps together to power the 2 speakers?

Easy. Use one amp to drive one speaker and the other amp to drive the other speaker. Common the amplifier inputs. Don't even think about paralleling the amplifier outputs.

what if the amps are of different wattage?

Posted: Wed Dec 03, 2008 11:22 am

Then you get one speaker at X watts, and one at Y watts.

Posted: Fri Jan 02, 2009 2:01 pm

if an amp is rated at 800w/CH @ 4ohm, and you parrallel two 8ohm speaker cabs to it, then each cabinet is going to be getting 400w right?

Posted: Fri Jan 02, 2009 7:28 pm

A: The DriveRack PA is a very cool piece of gear. The RTA mic works well and gives you a good place to start every time.

B: NEVER hook two amps to the same speaker or you will have zero amps after they both go up in smoke.

As CodeMonkey suggests one amp bridged into each speaker, is the closest you will get, until you can find the money for another amp or (two).

Posted: Fri Jan 02, 2009 10:01 pm

It was Boswell, I believe...

And the suggestion in the post was to use two amp channels, but if more power is needed then bridge the speakers and get another amp.

Rather be 300W over budget than 300W under powered.

Posted: Sat Jan 03, 2009 2:19 pm

stealthy wrote:

if an amp is rated at 800w/CH @ 4ohm, and you parrallel two 8ohm speaker cabs to it, then each cabinet is going to be getting 400w right?

still not understanding if this is a true statement or not....

Posted: Sat Jan 03, 2009 3:55 pm

Sorry, it read to me like he (stealthy) wanted to tie the speaker outputs together, which would be disasterous.

And credit where credit is due to Boswell...

Posted: Mon Jan 05, 2009 7:22 am

stealthy wrote:

if an amp is rated at 800w/CH @ 4ohm, and you parrallel two 8ohm speaker cabs to it, then each cabinet is going to be getting 400w right?

still not understanding if this is a true statement or not....

Invoking Ohm's law, yes, that's correct. BUT.. the problem is that the impedance rating of a loudspeaker cabinet is only nominal. An 8-Ohm nominal cabinet may actually be something like 25 Ohm around its bass resonance frequency, only 3 Ohm at the crossover between LF and HF units, and somewhere in between those values at other frequencies. If you parallel up two dissimilar cabinets, the highs and lows of impedance are going to occur at different frequencies for the two cabinets, meaning that the amplifier power is not going to be shared equally between them, leading to over-driving one cabinet or the other. So, to be safe, always parallel up identical cabinets.

Looking at it from another point of view, though, an 800W amp is reasonable to use with a 400W cabinet, and preferable to driving a 400W amp into clipping.

When parallelling up cabinets, unless you have very substantial cable, try to run separate leads back to the power amp for the two cabinets in order to reduce the power losses in the cable.

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