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Author Topic: What would you recommend?  (Read 6012 times)

Pete Sams

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Re: What would you recommend?
« Reply #10 on: March 22, 2011, 04:21:29 am »

Sorry, those specs seem way off all around. Those mackies I'd expect 750w RMS (sub) to be on the high side (1500w peak). The most I'd recommend with those speakers is 750w per channel @ 8, or even better would be around 550-600w for subs and 400-450 tops. Those drivers just can't take much more power and seeing as how they are discontinued, reconing will be much harder to do.

I've heard/mixed on these boxes. While not bad, I don't know why anyone would drop the $ to get 4 of them. But since you've got them.

QSC GX5 stereo for tops, 2 per channel
QSC GX7 stereo for subs, 2 per channel
than system will run for a long time and will be much less prone to driver failures. You could also use 2 GX7's and use 1 for left sub/top and 1 for right sub/top.
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luis Markson

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Re: What would you recommend?
« Reply #11 on: March 22, 2011, 04:45:13 am »

Sorry, those specs seem way off all around. Those mackies I'd expect 750w RMS (sub) to be on the high side (1500w peak). The most I'd recommend with those speakers is 750w per channel @ 8, or even better would be around 550-600w for subs and 400-450 tops. Those drivers just can't take much more power and seeing as how they are discontinued, reconing will be much harder to do.

I've heard/mixed on these boxes. While not bad, I don't know why anyone would drop the $ to get 4 of them. But since you've got them.

QSC GX5 stereo for tops, 2 per channel
QSC GX7 stereo for subs, 2 per channel
than system will run for a long time and will be much less prone to driver failures. You could also use 2 GX7's and use 1 for left sub/top and 1 for right sub/top.

By off, do you mean that 2 x continuous is not the way to match amp/speaker?
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Pete Sams

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Re: What would you recommend?
« Reply #12 on: March 22, 2011, 02:55:46 pm »

The only number you can halfway trust are RMS and peak. WTF is continous anyway, continous program according to EV 10 years ago was 50% of RMS, and they recommend powering at 1.5x cont. prog. or if you're an experinced user at RMS but no higher.

Any amp that clips will put out way beyond its rated power and that has to be taken into account when choosing an amp. Generally being at or below RMS will get the most out of your speakers. Beyond RMS power compression gets out of hand and any extra power is wasted as heat.
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Randall Hyde

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Re: What would you recommend?
« Reply #13 on: March 22, 2011, 03:00:40 pm »

I've been asked to recommend new amps for small system that I sometimes operate.
I have only had experience with QSC, so I can't say I have alot of experience to draw on.

The PA that it will run is 4 x Mackie S408 and 4x Mackie410s.

When you use the QSC Amp calculator it reccomends using 4 x bridged amps. Why would you do this rather than running 2 x high power amps at 2ohms?


When you drop below 4 Ohms, damping factor becomes an issue. You'll need either really short or really thick speaker cables. Even with 4 Ohms, 12 Ga cable drops you to a DF of 20 in 100' lengths (and keep in mind that the signal must traverse both sides of the cable between the amp and the speaker, so resistance is doubled).

I've been running bridged amps in the past (into 4 Ohms). Personally, I've gotten to the point where I'd prefer to have an amp that is twice the power running stereo. Half the rack space and considerably less weight than two bridged amps.  Probably slightly more than twice the cost, but worth it in the long run.
Cheers,
Randy Hyde
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Randall Hyde

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Re: What would you recommend?
« Reply #14 on: March 22, 2011, 03:06:34 pm »

The only number you can halfway trust are RMS and peak. WTF is continous anyway, continous program according to EV 10 years ago was 50% of RMS, and they recommend powering at 1.5x cont. prog. or if you're an experinced user at RMS but no higher.

Any amp that clips will put out way beyond its rated power and that has to be taken into account when choosing an amp. Generally being at or below RMS will get the most out of your speakers. Beyond RMS power compression gets out of hand and any extra power is wasted as heat.

Correct me if I'm wrong, but IIRC "continuous" is very well defined these days. I've seen two specifications that relate mainly to crest and time periods, but I've generally understood that continuous means a 6 dB crest factor pink noise signal applied to a speaker for a long period of time.

As for trusting peak, that's a no-go if you don't trust continuous. Peak = program + 3 dB and program = continuous + 3dB. Those values are calculated, not measured.  I can't speak for EV, but I do know that JBL's spec sheets explicitly state all this.

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Bob Leonard

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Re: What would you recommend?
« Reply #15 on: March 22, 2011, 09:37:39 pm »

The only number you can halfway trust are RMS and peak. WTF is continous anyway, continous program according to EV 10 years ago was 50% of RMS, and they recommend powering at 1.5x cont. prog. or if you're an experinced user at RMS but no higher.

Any amp that clips will put out way beyond its rated power and that has to be taken into account when choosing an amp. Generally being at or below RMS will get the most out of your speakers. Beyond RMS power compression gets out of hand and any extra power is wasted as heat.

You may want to read these articles.  ;)  Also note that JBL testing for continuos ratings is now 100 hours. So the answer to your "WTF" is simple. If JBL tells me I can put 1600 watts into a speaker for 100 hours non stop it becaomes a rating I can work with.
 
You also need to note that power compression occurs at any input level but to varying degrees depending on power applied and length of time applied. Better speakers suffer far less than lower cost or cheaper drivers simply because better drivers are designed to provide additional cooling to the motor assembly. This additional cooling, as in JBL's case, can be the equal to an additional 3-6db of output.
 
http://www.jblpro.com/pub/technote/spkpwfaq.pdf
 
http://www.crownaudio.com/amp_htm/amp_info/how_much_power.htm
 
http://www.jblpro.com/pages/general_faq.htm
 
 
 
 
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luis Markson

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Re: What would you recommend?
« Reply #16 on: March 23, 2011, 07:04:10 am »


Based on that assumption, one thing I would be cautious about is that although the S410s has a nominal 8 Ohm impedance rating, it also has a specified 3.8 Ohm minimum impedance rating (at 110Hz).  So while four of those in parallel might be a nominal 2 Ohm load, that would also represent a 0.95 Ohm minimum load. 

Why does Mackie supply the minimum input impedance for the S410s but not for the S408? Is there a greater variance of impedance across the frequency range of a sub than there is in a mid/high loudspeaker?

If so, why?
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Rob Spence

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Re: What would you recommend?
« Reply #17 on: March 23, 2011, 10:48:35 pm »

I suspect it is just sloppy marketting.
Why does Mackie supply the minimum input impedance for the S410s but not for the S408? Is there a greater variance of impedance across the frequency range of a sub than there is in a mid/high loudspeaker?

If so, why?
I suspect it is just sloppy marketing.
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