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Author Topic: Amplifier questions.....  (Read 10176 times)

Geert Friedhof

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Re: Amplifier questions.....
« Reply #40 on: May 11, 2017, 07:41:33 am »

I like the idea of passive monitors.

So what about this: Buy another XTI 4002. This will give you the option of running 2 monitors, 2 fronts, or 4 monitors and use the house PA. When one of the amps fails, or mains power is dodgy you can easily run from 1 amp. And when funds allow buy 2 SRX818P's which you use when needed.

Btw: you never mentioned which mixer you use.
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TJ (Tom) Cornish

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Re: Amplifier questions.....
« Reply #41 on: May 11, 2017, 08:42:19 am »

I agree, if you're constantly clipping ANY amp then you need to turn down.

But for arguments sake, if a larger amp makes virtually no impact as you say, should he just return the XTI 4002 and settle with a XTI 1002 and save some coin?

I guess what I'm saying is, being familiar with the equipment in question, I'm confident that by powering 2/ side STX 812m with a XTI 4002 he'd be leaving performance/headroom on the table. If he's doing small venue's and clubs (like I assume), then its a moot point. If he happens to be doing med-large outdoor shows with screamo bands or deaf rappers, he'd probably be clipping that XTI 4002 pretty often, and the XTI 6002 would probably be a better option. It's up to him to determine if the XTI 4002 is good enough.

This is all assuming that he follows the general ideology (as I do) that clip lights are bad, especially on full-range systems.

PS. +10000 to the self powered SRX 818SP recommendations. But he's made it clear that he prefers a passive setup and that's his prerogative, and his money. Hence, I didn't bother.

PPS. IMO the XTI feels closer to an iTech than its XTI brethren.
Michael, the difference between an XTI4002 and XTI6002 is 3dB.  The apparent volume difference between a clipped XTI4002 and an unclipped XTI6002 is probably nonexistent; in fact, the clipped amp may seem louder.

The problem with the thinking that a larger amp will help is the presumption that those last couple dB make the difference between an unhappy client and a happy client, and that clipping will no longer occur.  I have not found that to be the case.  Instead, the usual result - especially with mismatched amps/speakers - is fast destruction of the speakers.

This can be minimized with significant time spent on limiting such that the amp is programmed to not send more power than the speaker can handle.  This is not a trivial balance to strike - limit too early and performance is left on the table.  Limit to late and the smoke comes out.  Program material factors into this as well - EDM music with sustained sine waves requires different limiting than an R&R kick drum. 

This is the killer feature of the latest crop of self-powered speakers.  JBL (and others) have spent significant time testing this, and using the sophisticated processing originally from the ITechHD line (LevelMax) have worked out peak and RMS limiting such that the boxes are really hard to kill.

This can be reasonably well achieved with the STX series and ITech HD amps, especially if they are bi-amped.  This is a very high cost though - an ITechHD4x3500 into a pair of STX812m boxes is around an $8000 solution; a pair of the similar SRX812p boxes is less than $2500.  The XTI series amps, even with presets, do not have all of the special sauce in them.

I'm sure Jesse's system will be fine as most likely monitor wedge quality is lost in stage volume issues, not to mention too few mixes, and the box form factor is indeed nice.
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Tim McCulloch

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Re: Amplifier questions.....
« Reply #42 on: May 11, 2017, 10:51:46 am »

Michael, the difference between an XTI4002 and XTI6002 is 3dB.  The apparent volume difference between a clipped XTI4002 and an unclipped XTI6002 is probably nonexistent; in fact, the clipped amp may seem louder.

The problem with the thinking that a larger amp will help is the presumption that those last couple dB make the difference between an unhappy client and a happy client, and that clipping will no longer occur.  I have not found that to be the case.  Instead, the usual result - especially with mismatched amps/speakers - is fast destruction of the speakers.

This can be minimized with significant time spent on limiting such that the amp is programmed to not send more power than the speaker can handle.  This is not a trivial balance to strike - limit too early and performance is left on the table.  Limit to late and the smoke comes out.  Program material factors into this as well - EDM music with sustained sine waves requires different limiting than an R&R kick drum. 

This is the killer feature of the latest crop of self-powered speakers.  JBL (and others) have spent significant time testing this, and using the sophisticated processing originally from the ITechHD line (LevelMax) have worked out peak and RMS limiting such that the boxes are really hard to kill.

This can be reasonably well achieved with the STX series and ITech HD amps, especially if they are bi-amped.  This is a very high cost though - an ITechHD4x3500 into a pair of STX812m boxes is around an $8000 solution; a pair of the similar SRX812p boxes is less than $2500.  The XTI series amps, even with presets, do not have all of the special sauce in them.

I'm sure Jesse's system will be fine as most likely monitor wedge quality is lost in stage volume issues, not to mention too few mixes, and the box form factor is indeed nice.

^^^ THIS.  RIGHT.  HERE. ^^^
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Jesse Gregorio

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Re: Amplifier questions.....
« Reply #43 on: May 11, 2017, 12:50:06 pm »

I like the idea of passive monitors.

So what about this: Buy another XTI 4002. This will give you the option of running 2 monitors, 2 fronts, or 4 monitors and use the house PA. When one of the amps fails, or mains power is dodgy you can easily run from 1 amp. And when funds allow buy 2 SRX818P's which you use when needed.

Btw: you never mentioned which mixer you use.

I really like your idea. Thanks for the suggestion.

I primarily use a Allen and Heath Qu-16. My backup is an old Yamaha EMX-5016 (my original when I first started) which I hope to upgrade someday soon.
« Last Edit: May 11, 2017, 02:24:07 pm by Jesse Gregorio »
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Nathan Riddle

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Re: Amplifier questions.....
« Reply #44 on: May 11, 2017, 03:50:11 pm »

I really like your idea. Thanks for the suggestion.

I primarily use a Allen and Heath Qu-16. My backup is an old Yamaha EMX-5016 (my original when I first started) which I hope to upgrade someday soon.

OT:
Grab an xair 18 for your backup. Works great when you can't have a FOH and will get you through in a pinch for if the QU16 goes down (I use the QU24).
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Michael Storey

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Re: Amplifier questions.....
« Reply #45 on: May 11, 2017, 03:57:25 pm »

Michael, the difference between an XTI4002 and XTI6002 is 3dB.  The apparent volume difference between a clipped XTI4002 and an unclipped XTI6002 is probably nonexistent; in fact, the clipped amp may seem louder.

I agree that when looking at the numbers on paper there shouldn't be much of a difference between the two amps. But in practice, having personally tried a XTI4002 and XTI6002 on my old STX 828s subs, I found the apparent volume difference between a XTI4002 and XTI6002 just before clip was definitely noticeable, in favor of the 6002 of course.

The problem with the thinking that a larger amp will help is the presumption that those last couple dB make the difference between an unhappy client and a happy client, and that clipping will no longer occur.  I have not found that to be the case.  Instead, the usual result - especially with mismatched amps/speakers - is fast destruction of the speakers.

Would you agree the general consensus around here has been that (assuming the users program material has a typically high crest factor) it's best to use an amp that matches the program power rating of a loudspeaker? That's the way it's been on this forum for as long as I can remember, which dates back to a bit before Evan K. was blowing up Carvin speakers and whatnot (look at him now!). The XTI 6002 sits right in that sweet spot, but not over the top.

If you achieve the SPL levels needed with the underpowered 4002, but clip often, doesn't the last couple dB the 6002 affords you indeed become desirable? Again, this of course assumes one follows the ideology that you should keep your amps out of clipping.

This can be minimized with significant time spent on limiting such that the amp is programmed to not send more power than the speaker can handle.  This is not a trivial balance to strike - limit too early and performance is left on the table.  Limit to late and the smoke comes out.  Program material factors into this as well - EDM music with sustained sine waves requires different limiting than an R&R kick drum.

This is the killer feature of the latest crop of self-powered speakers.  JBL (and others) have spent significant time testing this, and using the sophisticated processing originally from the ITechHD line (LevelMax) have worked out peak and RMS limiting such that the boxes are really hard to kill.

This can be reasonably well achieved with the STX series and ITech HD amps, especially if they are bi-amped.  This is a very high cost though - an ITechHD4x3500 into a pair of STX812m boxes is around an $8000 solution; a pair of the similar SRX812p boxes is less than $2500.  The XTI series amps, even with presets, do not have all of the special sauce in them.

I'm sure Jesse's system will be fine as most likely monitor wedge quality is lost in stage volume issues, not to mention too few mixes, and the box form factor is indeed nice.

Great points.

I own a dozen SRX 800 series powered boxes, so it's safe to say I agree with you regarding their advantages. However, he made it pretty clear that he preferred passive subs. Yes, the powered SRX is the more logical choice IMHO, but he's free to do things the expensive way if he chooses to. Hence my suggestion of going with XTI6002 or even the IT5000hd to power a pair of SRX 818s. If he uses JBL presets for either amp, his limiting should be fairly dialed in, even on the XTI6002 (the XTI2 series limiters don't suck as much as the original XTI series).

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TJ (Tom) Cornish

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Re: Amplifier questions.....
« Reply #46 on: May 11, 2017, 04:23:33 pm »

Would you agree the general consensus around here has been that (assuming the users program material has a typically high crest factor) it's best to use an amp that matches the program power rating of a loudspeaker? That's the way it's been on this forum for as long as I can remember, which dates back to a bit before Evan K. was blowing up Carvin speakers and whatnot (look at him now!). The XTI 6002 sits right in that sweet spot, but not over the top.
Yes, the general rule is to have program-power-ish-sized amps, but there are a lot of assumptions to this - a couple being the need (and ability) to keep the amp from clipping, and R&R or gentler program material.
If you achieve the SPL levels needed with the underpowered 4002, but clip often, doesn't the last couple dB the 6002 affords you indeed become desirable?
Sure in theory, but it's a knife edge. 

Get a friend to do a blind test with you.  Play music (not a sinewave) at a fairly loud level.  Move the fader up 2dB and back.  See if you can actually hear the difference.  You can probably hear the difference at 90dBA in an otherwise quiet and dampened room, but now throw in a non-optimal small venue with 100dBA+ stage volume and I'll bet you money you won't be able to tell the difference.  For this marginal at best volume improvement, your speaker now has to dissipate almost twice the heat (3dB would be twice the heat), which significantly increases the risk of damage.  You're on the wrong end of a long lever - lots of input change for minimal output change.

If I was starting from scratch (and had a moral objection to self-powered speakers) I would probably get an XTI6002 over the 4002 just because, but I think upgrading an existing system from a 4002 to a 6002 is a pretty tough sell.  In the OP's situation, a second 4002 to add more monitor mixes will be a much better upgrade than a single larger amp.

By the way, it's unclear if the impedance issue was ever covered here.  Forgive me if I missed this, but was the OP trying to run all 4 STX812m off one side of the amp and his mains off the other side of the same amp?  If so, that's way too much on the same amp.  At a minimum, one XTI should run the 4 monitors and a different amp the mains, and yet a different amp the subs.  Or much better yet, self-powered versions of these things.
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Nathan Riddle

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Re: Amplifier questions.....
« Reply #47 on: May 11, 2017, 04:33:26 pm »

By the way, it's unclear if the impedance issue was ever covered here.  Forgive me if I missed this, but was the OP trying to run all 4 STX812m off one side of the amp and his mains off the other side of the same amp?  If so, that's way too much on the same amp.  At a minimum, one XTI should run the 4 monitors and a different amp the mains, and yet a different amp the subs.  Or much better yet, self-powered versions of these things.

2 STX boxes per channel on the amp.
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Jesse Gregorio

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Re: Amplifier questions.....
« Reply #48 on: May 11, 2017, 08:11:41 pm »

OT:
Grab an xair 18 for your backup. Works great when you can't have a FOH and will get you through in a pinch for if the QU16 goes down (I use the QU24).

I was looking at that or maybe an Xrack. Another alternative I was considering is the QU-Pac.
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Jesse Gregorio

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Re: Amplifier questions.....
« Reply #49 on: May 11, 2017, 08:21:37 pm »

At a minimum, one XTI should run the 4 monitors and a different amp the mains, and yet a different amp the subs.

Eventually, this would be the ideal setup that I would like to have, but my budget says otherwise at this time.
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Re: Amplifier questions.....
« Reply #49 on: May 11, 2017, 08:21:37 pm »


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