Question: you need ONE single 2 channel amplifier for a pair of subs under $1000... - Page 2 - AVS Forum
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post #31 of 52 Old 04-05-2013, 09:56 AM
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The powersoft's and iTech's are pretty much dead flat to 10hz, give or take a few db's, and with a 12db/oct shelf boost applied you will have useable output to about ~7hz.
Not sure about XTI's and XLS's.
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post #32 of 52 Old 04-05-2013, 01:19 PM
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Guys this Crown hpf at 20hz talk is nonsense. I dont care what whoever at Harmon support said. The Itechs, MA series and CE series all have a 3rd order 8Hz hpf which is about 3 dB down at 8Hz. There are measurements of a plethora of other Crown amps floating around and I have yet to see a single one with a 20Hz 24dB hpf.

Can anyone produce one?
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post #33 of 52 Old 04-05-2013, 01:19 PM
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Double post...anyway I have measured three Crown models myself and seen measurements on a bunch of others.
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post #34 of 52 Old 04-05-2013, 01:52 PM
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Quote:
Originally Posted by Ricci View Post

Double post...anyway I have measured three Crown models myself and seen measurements on a bunch of others.

Honestly, I was incredulous when I called Crown. I said "I am a writer for AVS forum, I want you to dispel this rumor that's been circulating". I don't know why I believed that tech, after all when someone says "It doesn't matter, because most people's speakers won't play below 30Hz anyway.", it's like they just announced "I have no idea what I am talking about." I even mentioned that I have a Crown amp and subs, which is why I found the 20hz high-pass filter claim to be a bit unbelievable.

I just ran a 4hz test tone through my subs, via a Crown XTi-2002; it works, as I knew it does because I spent so many hours testing when I built them. With a 24Db high pass at 20Hz, 4Hz should barely register, but I can push X-max if I want to, which would be impossible if the XTi was down 48Db or more at that point. The proof is in the pudding, you can bet I'm going to give Crown a longer phone call and insist on doing a short interview with an actual engineer. I'm going to get to the bottom of this, I'd hate to think some poorly informed reps are causing Crown to shoot itself in the foot when it comes to selling amps for subwoofer duty.

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post #35 of 52 Old 04-05-2013, 02:19 PM
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Please do imagic. HPF of 24db at 20hz does seem aggressive. Even 18db at 8hz is a bummer. But not a deal breaker.
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post #36 of 52 Old 04-05-2013, 02:32 PM
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I can confirm what Josh is saying. I don't own Crown products but have been around long enough to know that they have consistently have had the 3rd order HPF ~8hz. It's always been like that.

My Dual 18" LLT subs 120dB down to 10hz

 

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post #37 of 52 Old 04-05-2013, 06:07 PM - Thread Starter
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Quote:
Originally Posted by Ricci View Post

Guys this Crown hpf at 20hz talk is nonsense. I dont care what whoever at Harmon support said. The Itechs, MA series and CE series all have a 3rd order 8Hz hpf which is about 3 dB down at 8Hz. There are measurements of a plethora of other Crown amps floating around and I have yet to see a single one with a 20Hz 24dB hpf.

Can anyone produce one?

It's important to understand of course what you've asserted as "nonsense" is not what's being contended.

You seem to have missed the crucial point of this being related to current/recent model amplifiers as you have listed amplifiers that were discontinued years ago. Both techs I spoke with said "older" Crown amplifiers did not employ such an hpf so it's not surprising of course that the models you listed are a-ok in this regard.

Crucially though, the ONLY recent example I can think of that was benched was the xti chuck tested and it was absolutely miserable at 20hz, fwiw.

If there would be one current exception though I'd expect it to be the astronomically priced I techs...matter of fact the tech I spoke with said he THINKS the itech may have a defeatable hpf.

I know this: when I run a 20hz sine on my 4002 the output is ridiculous, when I don't change a thing and run a 10, output is through the floor. Of course you'd have output even with a 24db slope, but it would be down, well, 24dbs as it seems with mine. I can measure tomorrow.

I simply do not see why multiple crown techs would actively and knowingly spread false information with so much confidence. The gentleman I spoke with, Kevin, seems to have a pretty strong engineering background and didn't sound like he was just pulling things out of the air.

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

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post #38 of 52 Old 04-05-2013, 06:21 PM - Thread Starter
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Quote:
Originally Posted by imagic View Post

Honestly, I was incredulous when I called Crown. I said "I am a writer for AVS forum, I want you to dispel this rumor that's been circulating". I don't know why I believed that tech, after all when someone says "It doesn't matter, because most people's speakers won't play below 30Hz anyway.", it's like they just announced "I have no idea what I am talking about." I even mentioned that I have a Crown amp and subs, which is why I found the 20hz high-pass filter claim to be a bit unbelievable.

I just ran a 4hz test tone through my subs, via a Crown XTi-2002; it works, as I knew it does because I spent so many hours testing when I built them. With a 24Db high pass at 20Hz, 4Hz should barely register, but I can push X-max if I want to, which would be impossible if the XTi was down 48Db or more at that point. The proof is in the pudding, you can bet I'm going to give Crown a longer phone call and insist on doing a short interview with an actual engineer. I'm going to get to the bottom of this, I'd hate to think some poorly informed reps are causing Crown to shoot itself in the foot when it comes to selling amps for subwoofer duty.

You probably lost him the second "I'm a writer at avs forum" dropped. Both techs at crown and qsc exhibited open disdain- and even contempt- for this site and the "patently inaccurate data and assumption thrown all over the place" as one mentioned to me.

They seem to be pretty steadfast in their contention that they're not producing amps for the .01% sub-freaks on avs and hts and have no designs on changing and I would bet they'd be rolling in the aisles if someone asserted that they're "shooting themselves in the foot" for not producing amps for the sub 20hz DIY subwoofer crowd on avs.

I for one hope this all to be a misunderstanding, googling leads to dozens of posts/sites citing a 12-24 cut at 20hz so who knows? it would be nice if we had chuck or someone else around to put this to rest once and for all.

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

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post #39 of 52 Old 04-06-2013, 03:27 AM
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Quote:
Originally Posted by Scott Simonian View Post

I can confirm what Josh is saying. I don't own Crown products but have been around long enough to know that they have consistently have had the 3rd order HPF ~8hz. It's always been like that.

My money is on eight hz. That's how my amp behaves, and that's where most amps put their HP filter—between five and eight Hz. The tech said Crown uses the same HP filter they have always used, and they definitely have used a 24Db Butterworth at 8Hz in the past.

All that's left is to talk to an actual engineer, instead of their tech support guys. The tech guy, who was so sure it was set at 20hz, could not tell me the slope. Ultimately the proof is in the fact the amp will perform, down to single-digits. If the claimed HP was in place, the XTi would only put out something like one watt when playing an 8Hz sine wave, instead of pushing my cones to maximum excursion. Despite my previous flippant comments, it's not like I'm actually going to go sell my amp or something. I still prefer the XTi to the iNuke 6000 that preceded it.

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post #40 of 52 Old 04-06-2013, 05:18 AM - Thread Starter
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I'll wait for confirmation or measurements. Of course the amp will "perform" so long as by "perform" you mean there's output below 20hz- that's not what's in question. Again, it is undisputed that you will have output at 10hz...just a single watt will push around 90dbs out of many cabs- so you, like me, should definitely be "seeing" something around 10hz...and we are. It's just markedly down from 20 without touching a thing on my rig. Both crown techs I emailed and spoke with said it's a 24db cut.

I'm going to measure 10 and 20hz output with my 4002 for a laugh this am.

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

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post #41 of 52 Old 04-06-2013, 07:24 AM
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Quote:
Originally Posted by mastermaybe View Post

It's important to understand of course what you've asserted as "nonsense" is not what's being contended.

You seem to have missed the crucial point of this being related to current/recent model amplifiers as you have listed amplifiers that were discontinued years ago. Both techs I spoke with said "older" Crown amplifiers did not employ such an hpf so it's not surprising of course that the models you listed are a-ok in this regard.

Crucially though, the ONLY recent example I can think of that was benched was the xti chuck tested and it was absolutely miserable at 20hz, fwiw.

If there would be one current exception though I'd expect it to be the astronomically priced I techs...matter of fact the tech I spoke with said he THINKS the itech may have a defeatable hpf.

I know this: when I run a 20hz sine on my 4002 the output is ridiculous, when I don't change a thing and run a 10, output is through the floor. Of course you'd have output even with a 24db slope, but it would be down, well, 24dbs as it seems with mine. I can measure tomorrow.

I simply do not see why multiple crown techs would actively and knowingly spread false information with so much confidence. The gentleman I spoke with, Kevin, seems to have a pretty strong engineering background and didn't sound like he was just pulling things out of the air.

James

Hey believe whatever Broseph...smile.gif

2 of the amplifier series I listed are current... I will take actual measurement data myself every time. It isn't to hard to dig up actual measurements via that crazy thing called Google. BTW long term sine wave power results are not going to tell you where the high pass filter is. Wrong metric wink.gif Some of the XLS or lower end XTI amps could have a 20Hz hpf but I have never seen any evidence of this with any Crown amp yet.
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post #42 of 52 Old 04-06-2013, 08:13 AM - Thread Starter
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Quote:
Originally Posted by Ricci View Post

Hey believe whatever Broseph...smile.gif

2 of the amplifier series I listed are current... I will take actual measurement data myself every time. It isn't to hard to dig up actual measurements via that crazy thing called Google. BTW long term sine wave power results are not going to tell you where the high pass filter is. Wrong metric wink.gif Some of the XLS or lower end XTI amps could have a 20Hz hpf but I have never seen any evidence of this with any Crown amp yet.

I don't disagree with you re the itech and macro i series, etc. That's precisely what I want to know about the the xti and xls.

The CE hasn't been made in years. The MA series either...but perhaps ur referring to the macro tech I series?

See Crowns website:
http://www.crownaudio.com/usa/macro-tech-series.html
http://www.crownaudio.com/usa/amplifiers.html

Neither apply here. And I won't believe "whatever" but rather, the facts.

I have already asserted that one xti amplifier has been measured to fall through the floor at sub 20hz. It's right here on this very site.

Re other I techs, xls', etc, you must be a much more proficient "googler" than I because I have yet to find any credible measurement (ha, or ANY measurements for that matter) on them.

This isn't a war, just an honest search for a definitive answer. I never said that sine waves offer that definitive answer, simply my experience that a 20 is robust, and a 10 is virtually non existent when I run everything, level matched.

I respect your expertise and knowledge and do not wish to argue about it. There's an obvious conflict between the manufacture techs and others (here). A resolution would be nice, that's it.

Have a good one.

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

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post #43 of 52 Old 04-06-2013, 08:22 AM
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The QSC RMX is still a current product "old school" amp, listed at -3dB @ 5Hz., and the PL, PLX series listed -3dB @ 8 Hz readily available used, the Crown CE4K a bit less so.

While not personally in the market for any of these amps as I already have some of each, I am disappointed by the apparent dumbing down of the techical information presented for some/many of the newer models.

Just because there is a knob doesn't mean you should turn it.
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post #44 of 52 Old 04-06-2013, 11:51 AM
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Instead of the histrionics, just measure the damn things.
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post #45 of 52 Old 04-06-2013, 03:28 PM
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Instead of being forced to buy one, why not the mfg. actually list some useful info such as -3dB points like they seemingly used to.

Just because there is a knob doesn't mean you should turn it.
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post #46 of 52 Old 04-06-2013, 03:40 PM
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^^ Because for the majority of their market, they're not relevant.
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post #47 of 52 Old 04-06-2013, 07:35 PM
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So what? It's a technical spec many or most used to provide as a matter of routine course, and I'd bet measurement thereof still on file for their newer offerings.

Those that don't care are free to disregard it, and it would be there for a tiny fraction of a penny in ink costs to sway the decision of those to which it does.

Just because there is a knob doesn't mean you should turn it.
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post #48 of 52 Old 04-06-2013, 08:41 PM
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Is it more expensive to add a HP in an amp than to leave it out? Why add it in the first place?
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post #49 of 52 Old 04-06-2013, 08:45 PM
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Is it more expensive to add a HP in an amp than to leave it out? Why add it in the first place?
For professional applications, subsonic frequencies do nothing but waste power and potentially damage speakers. Basically, it is a safety feature. You don't want a DC signal frying a P.A. system.

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post #50 of 52 Old 04-06-2013, 08:57 PM
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Quote:
Originally Posted by imagic View Post

For professional applications, subsonic frequencies do nothing but waste power and potentially damage speakers. Basically, it is a safety feature. You don't want a DC signal frying a P.A. system.
Agreed. I routinely EQ'd out anything below 30Hz when doing FOH to stop odd resonances and to keep radiated LF down to stop residents near venues complaining. It also allowed me to control excursion below tuning for the ported subs.

In most older amps, the LF filter is simply the DC blocking cap at the input of the power stage. It's generally only in some newer designs that additional op amps are included to roll it off more steeply.
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post #51 of 52 Old 04-07-2013, 04:50 AM
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Quote:
Originally Posted by imagic View Post

For professional applications, subsonic frequencies do nothing but waste power and potentially damage speakers. Basically, it is a safety feature. You don't want a DC signal frying a P.A. system.

I agree, to some degree, but certainly the speakers of today aren't any more succeptible than they were the other day, so to speak. And, I don't think most are asking for a DC amp, flat to DC.

Makes me question whether that's the real motive or if many amps today just don't cut the mustard down there so it's a convenient story line. With the prevalence of DSP you'd think you'd be able to adjust it down if you wanted, or at least defeat the filter with a switch or readily accessible board jumper.

Just because there is a knob doesn't mean you should turn it.
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post #52 of 52 Old 04-09-2013, 01:52 PM
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The word from Crown:

Yes, the HP filter on new Crown amps starts to have an effect at 20Hz, but the curve is not centered on 20Hz. Also, the slope is not 24Db/octave, it's around 12Db/octave, but since it's a curve, the full slope is not achieved until a lower frequency - around 8Hz. Officially, Crown does not test or rate their equipment below 20Hz, but this info comes from their head tech support guy for amplifiers, and he vetted it through a couple of engineers.

What he described is much more consistent with how my XTi-2002 behaves. On the flip side, a few particularly brutal Blu-rays used to clip my system when I used an iNuke 6000 to run the subs. Now, with four LLTs tuned to 16Hz, the HP filter is welcome and my system never stumbles. My adjacent neighbor is already beyond hating me (he ignores me on the street) and I normally use a small fraction of the system's capability. Crown amps are NOT for power-users who wish to plumb the depths of single-digit and low teen Hz with sealed subs, for everyone else, they should work just fine.

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