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Amping for one SRX728


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#1 fsalo

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Posted 28 July 2012 - 10:45 AM

Hi,

I have the same problem as http://www.crownaudi...ic=3959&hl=clip (XTi4000's clip LED's turns on, without the -10 LED's ever turning on).

I have one SRX728 currently powered by one XTi4000 in bridged mono (CH1+CH2, 110Hz LP).

First thing: Frankly I don't understand what the issue is because according to the specs, the XTi4000 is supposed to have 3200W@4 Ohm and the SRX728 needs to have 1600W (and is 4 Ohm). Shouldn't that be enough headroom!?

Second thing: I'm sure this was asked before, but the forum doesn't let me search for "srx" or "728". The above linked thread mentions a MA9000i being ideal for a pair of 728's, but what would be a good choice for a single 728? Would the XTi6000 be okay?

#2 dakos

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Posted 02 August 2012 - 03:29 AM

Hello :)
There is a real big misunderstanding of how much power a speaker needs, the 728 is rated at 1600W continuous and 6400W peak, that's 6dB of headroom built into the speaker by design. Amplifiers don't have allot of headroom built in them (1-2dB for the higher end amps) so it's up to us to have enough peak amp power and at the same time, not too much continuous power. One more thing to take into consideration is that when you feed a speaker its rated continuous power for a long time you will encounter power compression, that means that the actual continuous speaker power is 3-6dB below the rated continuous speaker rating. So actually for the 728, 1600W of continuous power is too much continuous power.

There are a few reasons the XTI series are not that good for sub duty (They are great amps for other uses but not heavy sub duty), further then this operating this amp at a 4 ohm bridge configuration is extreamly demanding on the amp.

One thing you can do is also configure a HPF @ 35Hz at 18 dB/octave, this would help the amp cope with the task by filtering out the unreproducable sound.

About an amp suitable for the 728, since it's a 4 ohm cab, the itech/MAi would excell at 4 ohm per channel, so would the XTI, but the XTI doesn't have nearly enough peak power like the itech/MAi 6000/8000/9000/120000 have, you can get used gear with plenty of warranty left, the itech 6000/8000 are great at that kind of sub duty for about the same price as a new XTI6002.

#3 KevinNRP

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Posted 28 November 2012 - 01:36 AM

Looking to get a 5000i for my pair of SRX728 but I'm worried about tripping a breaker. Usually I'm only using normal 20amp circuits I only use 30amp when I'm running a distro. My questions are:
Would a 5000i be enough for the pair of SRX728 subs?
And will it require using a 30amp circuit or could I use a 20amp circuit?

On another note could I use the 5000i on a 20amp circuit if I'm only using 1 channel?

Also I'm new to understanding 1/3rd Power Pink Noise which reads on the specifications of an amp.

#4 dakos

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Posted 28 November 2012 - 06:19 AM

I didn't put the 4000/5000 amps there for a reason, they will "only" give a peak of 3000W per channel at 4 ohm, that is 3dB less of the peak power that each 728 can handle, not that big of a difference if you ask me.

Now about the 20 Vs 30 amp breakers, all the itech/mai series amps require a 30 amp breaker because at full demand they need all that power, if you plan to run two 728s on one amp, that's allot to ask from any amp. If you get an itech or mai you will get one of the most efficient amps you can get so even with all that load and only 20 amp breaker, you will still be able to get much higher SPL levels then most other amps out there.

If you oparate only one channel, usually the watts supplied by it go up, say an amp supplies 2x2000W at 4 ohm, if you connect only one channel it will supply 1x2500-3000W. Remember this is a rough wattage estimate to demonstrate the principle rather then varified measured exact numbers.
Avi