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[DaveStep]

Hey everyone,

I am pretty new in the realm of ProSound and I don't profess to know all the answers. I figure something out that works and just never mess with it. I am a DJ and I do small-mid size events where I am expected to bring sound. For the last six years, I have run 3-XTI-2000's in bridged mono, with 100hz and -3gb clip to run 3-JBL-SRX-718. The tops I use are self powered. Normally I am always needing more bass than I can get so I usually run the amps all the way up to where I see the limit light illuminate and then bring them down a notch so that I don't see that light.

I know this isn't the way to do it, so after a bunch of research, I decided I would buy a PLD4.5 and use it to run the subs. I was super excited, but woefully let down after my first weekend. I used the JBL presets within the amplifier for the subs - 800w/30hz/80hz. They didn't get very loud before the limit light illuminated, and they didn't really sound very good. I know sound is subjective, but I will do my best: There was lots of deep bass mixed with some muddy bass, but not much else.  I suspect the crossover being set lower than what I am used to, but, if these specs are coming straight from JBL, I'd have to assume they are correct.

I called QSC and they told me to just take the limiters off and run it in two channel mode with only two subs, each to receive 2500 watts. This didn't set right with me, and I don't want to break my trend of never having blown a speaker. Again, I'd have to assume JBL would know what they were talking about in terms of setting the 800w. They also said to up the low pass crossover to around 100hz.

The other odd thing was that the amp displays the current usage on the front. It never exceeded 3amps all night, most of the time it was around 2-2.5 amp draw. That just doesn't seem right for three subs, or I have found a super efficient amplifier!

Any advice would be appreciated!

[Bob Faulkner]

For sure - raise the xover point to 100hz (LR/24); check the limiter to make sure it's not coming on too soon (sort of sounds like it is from your description).  Any compressors in use...?  disable them.  The limiter should only be used as a last resort "catch all" for signal spikes.  Maybe try setting your limiter to a few db more (within reason).

The SRX718  speakers can handle 800 watts continuously.  For DJ use, it may not be best to use much more power than this - because recorded music is already heavily compressed and you're not going to get too much headroom out of a recording.  Keeping amplifier wattage to around 800 watts will more than likely keep you from burning anything up.

[Kevin Bayersdorfer]

I just took a quick look at the manual, the limiter has all kinds of settings. In auto mode there is mild, medium, and aggressive. It is probably set to the latter, but possibly it is set in the advanced mode as you are using a preset. Find the limiter settings and try the mild option. Also keep in mind the amp has many places to adjust gain and sensitivity. Input gain, crossover gain. so look into those also.
Edit: just looked up specs for the subs. I would increase available power up to 1250 from 800, move the high pass up to 40, and keep the 80 low pass for now. Definitely not a plug and play amp, you are going to have to do some extensive testing /trial and error. 

[DaveStep]

Thanks guys. I was running an XTI-2000 bridged on each one, which was supposedly 1600W. I doubt that the little XTi did in fact put this much out, so, I will increase it a bit and see if it makes a difference. I will also give some different crossover frequencies a shot. Will have to wait till next weekend, as I doubt my neighbors will appreciate the bass.

[Tim Weaver]

I cut the available current to my subs in half and now they aren't as loud! What do I do!?!

[Scott Harris]

But with half the power they're still more than half as loud......    :-)

[Corey Scogin]

Thanks guys. I was running an XTI-2000 bridged on each one, which was supposedly 1600W. I doubt that the little XTi did in fact put this much out, so, I will increase it a bit and see if it makes a difference. I will also give some different crossover frequencies a shot. Will have to wait till next weekend, as I doubt my neighbors will appreciate the bass.

By the way...is DaveStep your real name or your DJ name?

[DaveStep]

I cut the available current to my subs in half and now they aren't as loud! What do I do!?!

I appreciate your kind words. I assumed that the amp, despite being limited at 800w RMS, was still peaking or bursting or whatnot at a higher wattage. I understand now that this was an incorrect assumption.

And yes, this is my real name.

[Tim Weaver]

PMPO is marketing bullshit.

If your amp is peak limiting at 800 watts, you are giving the driver 800 watts. It may go over that for a few milliseconds, but not enough to make any difference at all.

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