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Effects of Biamping

S

scrotimusprime

Feb 15, 2008
120
1
San Francisco
www.level12band.com
#1
Ok, I understand the basics. You biamp and you can isolate certain frequencies to a certain cab. Ok sure, but what does that mean in terms of sound/power?

Say for example I've got an 18 I'm going to biamp. Ok, so if its not biamped it gets the full range signal but the speaker can only produce sound in a specific range.

Does this mean that the amplifier effectively "wastes" power - That is -> The head amplifies a signal that is otherwise thrown out?

OR do you lose sound quality as your 18" tries to make sounds it just can't do very well?

Or maybe something different -> Really I want to know what biamping buys me and when not biamping would hurt me. I read the faq, searched the forums, and googled around but I didn't find anything that specifically answers that question.

Thanks again,

Carl - Reconfiguring his rig, one day at a time
 
#3
scrotimusprime said:
Does this mean that the amplifier effectively "wastes" power - That is -> The head amplifies a signal that is otherwise thrown out?
Click to expand...
Yes.
if you biamp with a rig not made for biamping, you're going to create a hole in your mids.
Click to expand...
If all he has is an 18 he has no mids. :crying:
A ten would go well with it, but in a very small cabinet, a cubic foot or so, crossed over at 800 Hz. Any larger cabinet than that would be wasted cartage, since the ten would not be working down low where a larger cab is required.
 
#4
When you biamp, you usually use an active crossover before (or inside) the power amps, so each amp only amplifies the range it needs. If you were to use a passive crossover at the speakers, that would be burning off the power in the range you didn't want.

Your example of the 18: Most bass speakers are full-range, but of course they drop off at the upper end. That's why cabs use mid and tweeter drivers, to pick up things from there up.

If you crossed your 18 for use as a sub, it would be fed the low end. You'd need a different cab, say an 8+tweet, which would handle only the mids and top.

You can't effectively bi-amp if the speakers cover the same range. For example, an 18 and a 10 cover basically the same range. Bi-amping to them doesn't buy much at all. [Edit: As Bill said. His suggestion would limit the low end of the 10 so it acts as a mid driver.]

Bi-amping is generally expensive and bulky, and it doesn't really do much for an instrument. For a PA, multi-amping is the way to go.
 
#5
Well, I've got 3 cabs, an 18, a 15 and 4x10 already. On top of that I've got an svt4 pro so biamping at this point will literally cost me a patch cable.

What I was thinking of doing was putting the 18 in a biamp setup and letting the 4x10 and 15 cab handle the full range. The idea would mostly be to get the most out of the 18 since there's plenty its not going to do in terms of the higher frequencies.

Now I hadn't done that in the past because I didn't know what I was doing. Now here's the another question: what's multi-amping?
 
#6
It's worth experimenting since doing so costs you nothing.

Technically the 15 and 410 won't be full-range, they'll just handle the portion above the range of the 18. If you have them overlap, you can get some bad phase issues where they can actually cancel.

I suspect that the 15 and 410 will be a waste trying to handle only mids and highs. You could do that with a much smaller cabinet.

But experiment, and listen not only from a stage position but out in the house. What happens out there is often quite different, and that's what counts more.

Sorry about my use of the term "multi-amping." What I meant was separate amps for sub, mid/main, and top end. I believe the proper term is tri-amping.
 
#7
scrotimusprime said:
Well, I've got 3 cabs, an 18, a 15 and 4x10 already. On top of that I've got an svt4 pro so biamping at this point will literally cost me a patch cable.

What I was thinking of doing was putting the 18 in a biamp setup and letting the 4x10 and 15 cab handle the full range. The idea would mostly be to get the most out of the 18 since there's plenty its not going to do in terms of the higher frequencies.

Now I hadn't done that in the past because I didn't know what I was doing. Now here's the another question: what's multi-amping?
Click to expand...

I think your going to just have uneven response if you run the 15's and 10's full range.

You will have lots of polar problems (a 4x10 cab already has enough polar problems doing a 15 and a 4x10 only makes things worse)

Best is to try and get things to combine nicely at xover and have even amplitude response. Bewteen 10 and 18.
 
#9
first off - you guys know what you are talking about.

Last night I reconconfigured my amp setup and it made a world of difference. I pulled the 15 out of my configuration and wired a full biamp setup.

That is, hi's to the 4x10 cab and lows to the 18. World of difference. Now i'm just mucking with the cross over frequency trying to find the sweet spot.

Thanks guys,

Carl
 
#12
It's good that you have the basics to experiment with, because that's the way to get a practical understanding of the theory.

If you use the biamp setup in a large room, make sure you wander around the house during sound check to be sure your sound is good in the house. (Carry an extra long cord or wireless just to do that.) After you've checked a couple of typical venues, you won't have to bother.
 
#13
80-100 hz might be low for your garden variety 18" bass speaker. Subs in a PA are either horn loaded or used in large boxes, in clusters if they are reflex: a single 18" would need to be crossed at a higher point IMHO.

I think some softwares are available to analyze speaker freq response curve, wich might help you figure out the needed crossover freq.
 
#14
Isn't bi-amping using a two amplifiers for different frequency ranges? I think what you're doing is using a crossover (without separate amps). I'm working on a second cab to do the same thing. Hurray for technology and information flow that lets us musicians hot-rod our rigs for better sound. :hyper:
 
#16
I usually set the x-over freq around 200hz. my ampeg pr1832he has one downward angled 18 for the lows and 2x10 + 2x6.5 + horn on the top. Usually the low freq's are a little more power hungry than the highs. different power to the highs vs lows is another way to "balance" your tone for the room.
 
#17
not to confuse the issue here but I am considering running a external power amp, Yamaha P2500 or Carvin DCM1500 thru my GBE750 amp head into a 212 and 215 cab. I dont imagine I can control the lows and highs seperately right? So this would be more just running it all full range correct? Good thread.
 
#18
ErnieD said:
not to confuse the issue here but I am considering running a external power amp, Yamaha P2500 or Carvin DCM1500 thru my GBE750 amp head into a 212 and 215 cab. I dont imagine I can control the lows and highs seperately right? So this would be more just running it all full range correct? Good thread.
Click to expand...


There are a couple of choices but adding in a decent EQ or crossover would let you set the frequencies recieved by the Yammy. If it was a 3-way x-over, then you can set the low's for a hard stop at say 40 hz or 45, then the hi's for a stop at I dunno - I'd probably run the 15's full range and let them die off on their own...

I run dbx and Rane EQ's in my PA. They all have switchable hi-pass filtering built in. I use that to protect my top boxes (JBL EON's). I use the 30 hz filter on my power amp (it's a QSC) to protect the sub.
 
#19
ErnieD said:
not to confuse the issue here but I am considering running a external power amp, Yamaha P2500 or Carvin DCM1500 thru my GBE750 amp head into a 212 and 215 cab. I dont imagine I can control the lows and highs seperately right? So this would be more just running it all full range correct? Good thread.
Click to expand...

You can get an external xover, if your GBE750 has a pre amp out and an amp in.

Use the DCM for the 15's and the GBE for the 12's

Carvin makes an inexpensive xover. Lows to 15 highs to 12's
 
#20
scrotimusprime said:
That is, hi's to the 4x10 cab and lows to the 18. World of difference. Now i'm just mucking with the cross over frequency trying to find the sweet spot.

Thanks guys,

Carl
Click to expand...
With a standard 4x10 you'll probably find 150 to 200 Hz to be about right. Higher than that and there's no benefit in having such a large cab or so many drivers.
 

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