Bridging vs $2000 amps

Is this amp OK?
Post Reply
Message
Author
tuna
Posts: 55
Joined: Wed Aug 10, 2011 7:16 pm
Location: San Diego, CA

Bridging vs $2000 amps

#1 Post by tuna »

I went to an event recently and looked into the sound system. They had 3 dual 18" horn loaded subs on each side for 12 subwoofers total. These were powered by Crown amps that were bridged and provided bone shaking bass for a crowd of about 150 at any given time. Ive always read that bridging is bad. But, how do I get to the proper amount of power without spending a shitload of money? My BFM box has dual 15" drivers in it asking for 900w. I hooked up an amp that provided 950w @ 2 ohms and it was obvious that it was underpowered. It was suggested that I needed more overhead power for the drivers which puts me up to something like a Crown 6002 at $1600. But is that necessary? Why not bridge? What would I be risking with bridging? Bridging is made out to be bad but it seems like it is impossible to power some drivers without bridging... whats the deal?

User avatar
BrentEvans
Posts: 3044
Joined: Thu Oct 09, 2008 10:38 am
Location: Salisbury, NC

Re: Bridging vs $2000 amps

#2 Post by BrentEvans »

OK Class... everyone repeat it.... WATTS ARE MEANINGLESS.

I do believe you're comparing apples and oranges. Each driver has a thermal rating in watts at a given impedance in ohms. Amps are rated for watts at multtiple impedances. 950 watts at 2 ohms is 43 volts. You can't measure watts, but you can measure volts. If your drivers are "asking" for 450 watts at 8 ohms, and are wired in parallel, you need an amp capable of 60V of output to reach that amount of power.

There is nothing inherently wrong with bridging to get to the voltage you need, as long as you deploy a limiter to prevent over-voltage.

As to the gig with three double 18s and loads of power.... there's no replacement for displacement. 6 decent 18s will move more air than 2 remarkable 15s, regardless of the cabinet configurations. A BF cab will make the most out of those 15s, though.
99% of the time, things that aren't already being done aren't being done because they don't work. The other 1% is split evenly between fools and geniuses.

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: Bridging vs $2000 amps

#3 Post by Bill Fitzmaurice »

tuna wrote: My BFM box has dual 15" drivers in it asking for 900w
Speakers don't ask for watts. They do require a specific voltage to reach full output.
I hooked up an amp that provided 950w @ 2 ohms and it was obvious that it was underpowered.
What maximum voltage output did you measure?

tuna
Posts: 55
Joined: Wed Aug 10, 2011 7:16 pm
Location: San Diego, CA

Re: Bridging vs $2000 amps

#4 Post by tuna »

So I was wrong. I do believe I meant 900 @ 4ohms. The drivers are Eminence 3015LFs. I have not measured the output voltage but rather set my limiter settings based upon a calculator I found linked on this forum and which was discussed as a method of setting it all up to properly protect my speakers. With my own system I found that when I did this I the subs would quickly start clipping my amp resulting in me having to turn the limiter voltage down so that the subs hitting would hit the limiters but would not clip the amps. I figured the solution to this was a larger amp/more headroom and thus my original question.

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: Bridging vs $2000 amps

#5 Post by Bill Fitzmaurice »

tuna wrote: I have not measured the output voltage
:wall:

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Bridging vs $2000 amps

#6 Post by Bruce Weldy »

tuna wrote: rather set my limiter settings based upon a calculator I found linked on this forum
You cannot set voltage limits with a calculator. You must use a volt meter. They are cheap.....get one. Everything gets easier...and it actually works.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

tuna
Posts: 55
Joined: Wed Aug 10, 2011 7:16 pm
Location: San Diego, CA

Re: Bridging vs $2000 amps

#7 Post by tuna »

Ok. I have one. I will give that a shot.

Post Reply