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Author Topic: Crest Pro 8200 amps  (Read 36861 times)

TJ (Tom) Cornish

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Re: Crest Pro 8200 amps
« Reply #90 on: August 16, 2010, 09:34:33 AM »

Alan Sledzieski wrote on Sun, 15 August 2010 07:28

What kind of power amp should I be looking at for the horns?
The 2 '' horns are 16 ohm, 150w.  I have no idea what kind of power a horn needs, I know not much.  But would a stereo 300w into 8 ohms be right? I'm guessing the amp would do 150 into 16 ohms?


At higher impedances, the amp's output voltage potential determines its capacity.  At lower impedances, the current producing supply is usually the limiting factor.

If a hypothetical amp can produce 300 watts into 8 ohms, this means the amp can supply 49 volts.  This same 49 volts into 16 ohms does indeed give your 150 watt number.  If however, the amp for some reason was current limiting at 8 ohms, the amp may be able to produce more than 49 volts into 16 ohms, which means you may get a little more than 150 watts out.

I will let those more versed in drivers give you general rules for horn power capacity, but here is a datapoint for you:

The JBL SRX722 box has a JBL2451H 4inch coil compression driver.  The spec sheet lists the power capacity as 75w / 150w / 300w continuous / program / peak.  I'm guessing that this is a pretty high power HF driver, but I don't have a lot of personal experience comparing them.

Headroom is a good thing, which is why you will see a lot of speakers having the same size amp driving the HF section as the lower sections.  This combined with good limiting is probably the best method.

I still think you should try to audition the newer light weight amps.  A 7lb Peavey IPR1600 would seem to fit well in this application, or a PLX 1604, 2402, etc. as well.  You need to do something to make your amp racks more managable because of all of the extra weight of voltage regulators you are carrying around.  Very Happy
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Phil Ouellette

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Re: Crest Pro 8200 amps
« Reply #91 on: August 16, 2010, 12:07:11 PM »

Alan Sledzieski wrote on Sat, 31 July 2010 03:56

Will someone please tell me what 1200 / 0 = ????????????


Finally something I can contribute.  Value/0 = infinity.

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That's "newbiesque" to my friends.

Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #92 on: August 16, 2010, 05:36:51 PM »

TJ (Tom) Cornish wrote on Mon, 16 August 2010 09:34

Alan Sledzieski wrote on Sun, 15 August 2010 07:28

What kind of power amp should I be looking at for the horns?
The 2 '' horns are 16 ohm, 150w.  I have no idea what kind of power a horn needs, I know not much.  But would a stereo 300w into 8 ohms be right? I'm guessing the amp would do 150 into 16 ohms?


At higher impedances, the amp's output voltage potential determines its capacity.  At lower impedances, the current producing supply is usually the limiting factor.

If a hypothetical amp can produce 300 watts into 8 ohms, this means the amp can supply 49 volts.  This same 49 volts into 16 ohms does indeed give your 150 watt number.  If however, the amp for some reason was current limiting at 8 ohms, the amp may be able to produce more than 49 volts into 16 ohms, which means you may get a little more than 150 watts out.

I will let those more versed in drivers give you general rules for horn power capacity, but here is a datapoint for you:

The JBL SRX722 box has a JBL2451H 4inch coil compression driver.  The spec sheet lists the power capacity as 75w / 150w / 300w continuous / program / peak.  I'm guessing that this is a pretty high power HF driver, but I don't have a lot of personal experience comparing them.

Headroom is a good thing, which is why you will see a lot of speakers having the same size amp driving the HF section as the lower sections.  This combined with good limiting is probably the best method.

I still think you should try to audition the newer light weight amps.  A 7lb Peavey IPR1600 would seem to fit well in this application, or a PLX 1604, 2402, etc. as well.  You need to do something to make your amp racks more managable because of all of the extra weight of voltage regulators you are carrying around.  Very Happy


All the wieght,  I'm happy I cut my amp wieght in half, I used to run the vs 1500's on the bottom end at 40 lbs each.  That was 2 amps 3kw total, 80 lbs  Now 2 8200's at 40 lbs per pair at 9kw.

I'd probably stick with a 200 series amp for the horns, 5200, 7200, 8200, what ever is needed.

leave my regs alone Laughing
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Greg Dreese

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Re: Crest Pro 8200 amps
« Reply #93 on: August 16, 2010, 05:53:38 PM »

Alan Sledzieski wrote on Sun, 15 August 2010 06:28



So here's 2 questions for you guys.

How much power is lost going through the internal crossover?




I don't believe I saw a response to this part of the question, and I would also be interested in the answer.  And if the answer is, "it depends," then is there some sort of average range?  And how different is it, depending on whether the crossover is two-way or three-way?

Greg
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Art Welter

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Passive crossovers, who cares about amps..
« Reply #94 on: August 18, 2010, 06:08:21 PM »

Alan Sledzieski wrote on Sun, 15 August 2010 06:28


So here's 2 questions for you guys.

How much power is lost going through the internal crossover?

What kind of power amp should I be looking at for the horns?
The 2 '' horns are 16 ohm, 150w.  I have no idea what kind of power a horn needs, I know not much.  But would a stereo 300w into 8 ohms be right? I'm guessing the amp would do 150 into 16 ohms?

Horns don't need any power, HF drivers do Cool .

The CA 9 is a good choice for HF power, you could use as  much as three dB more depending on the driver and crossover frequency.

Insertion loss in a passive crossover depends on the components used, but high quality capacitors and coils can yield an insertion loss of well under one dB.

Most good HF drivers on a horn are around six to 10 dB more more sensitive in the mid band than the woofer, so they are typically attenuated with resistors a similar amount.

That said, most good large diaphragm HF drivers on a CD horn roll off almost 10 dB at the top of their range, so bypass caps are put in the circuit to keep the frequency response flat up high. Without that compensation, the extra power needed in the UHF would be wasted in the resistors.

So the passive crossover insertion loss could vary from around 10 dB to one dB depending on frequency.

LF passive crossover components are larger and more expensive, using poor components for low crossover points can result in as much as 2 dB loss. With the price of big coils and capacitors, it generally is more cost effective to use active crossovers below around 300 Hz.

Art Welter
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Alan Sledzieski

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Re: Passive crossovers, who cares about amps..
« Reply #95 on: August 22, 2010, 11:54:16 PM »

12 or so years of running 6 crest vs 1500 and 2 ca 9 amps, never a problem, 3rd or 4th night out with the 8200's,, acl lit on one amp, it shut off.  I turned the switch off let it sit, turned it on, nothing.

Funny thing is I just glanced over at the amps, and saw it happen

Ran the rest of the night with 3 double 18's, 1 8200 short at this point.

Not very happy.

Thinking I should hold on to my old ca9's and the 3 vs 1500's I have left.

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Tim McCulloch

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Re: Passive crossovers, who cares about amps..
« Reply #96 on: August 23, 2010, 01:17:03 PM »

I haven't heard anyone complaining about frequency of failure with the Pro*200 series, but every manufacturer, every model... will have failures.

A friendly competitor has roughly 100 of the new units and has had only a couple go down from undetermined failures.  The few others that failed had documented abuse.

I'd chalk this up to randomness.  Send it back to Crest/Peavey and see what they say about it when it comes home.
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