QSC old iron...

[David Raehn]

I usually run my four T48s (3015LF) with a QSC RMX1450. While I know that there isn't enough meat to take them to max, they don't do all that badly. I limit to 40v just to keep from pushing the amp too hard. I recently picked up an immaculate QSC MX1500 for cheap and got to thinking about how to implement it for the subs. The T48s are 8ohm and I run a pair from each side of the RMX1450, resulting in 4 ohm load on each channel. The specs suggest that this should net ~450 watts per channel or 225 per cabinet. If I wired only one cabinet to each channel the result would be ~280 per channel.

With the MX1500, I would be looking at ~570 per channel wired 4 ohms (285 per box) or 360 wired singly.

I realise the correct answer would be to have two of the same model amp, or one much bigger one, but what would you suggest I do to set up this correctly. I'm running a DCX2496 and I guess I could set separate limiters for separate outputs.

I cannot believe that I'm the only one that may have this issue......

[Grant Bunter]

Hi draehn.

You haven't added 2 ohms of acoustic impedance for cabs.
So, with the RMX1450 your load per channel with 2 cabs a channel is 5 ohms.

This is better, when redoing you calculations, you end up with slightly higher voltage output per channel and lower amperage output per channel.

You could use the RMX1450 for a pair of cabs and the MX1500 for a pair of cabs.
Yep, use the DCX with 2 different sub outs to send signal to each amp, as you can have a higher voltage output for the MX1500, leading to overall max output increase compared to your current setup, but still not up to max voltage limit for the 3015lf as per the plans...

[David Raehn]

Ahh... Forgot about the added acoustic impedance.

Well it's good to know that I can put it to use with the equipment I have on hand.

I'm starting to have a collection of these heavy old amps. (still haven't found a good home for my Crown K2 (might be good for my 4 OT12s)) I should sell them for install setups and use the money for some new class D stuff!

Thanks, Grant.

[sine143]

why not use the k2 on the t48s?!?!?!. can use your other "old iron" amps for the otops.

[David Raehn]

Good point....