Measuring Amplifiers - Page 60

Well I'm already driving an 11 channel DSX array (7 channels off a Sherbourn 200/300 watt amplifier) to sometimes oppressive levels and everything seems ok.

I also have a Definitive Trinity subwoofer on the same circuit, all of my components, and my 60" Kuro and rarely do I see amperage draws over 12.0.

35-40 amps off a 15 amp household circuit have to be all but impossible even for more than a second or two I'd imagine.

James

Assuming I interpret the SQ D trip curves properly, somewhere between about 5 and 15 second @ 37.5A (2.5X the 15A breaker rating).

Well take heart, because I can tell you without hesistation that you will NOT find out a lot about the A7-450....NOT the sealed version, but the gigantic, 300lb, ported version.

I've read more about folks complaining about the lack of info on it rather than any solid info on it.

And granted mine will externally amplified, but I still plan on writing a thorough review on it when all is complete.

The Captivator has an entire thread dedicated to it if you're interested in it. Plenty of owner feedback there.

James

Whew.

While I of course appreciate such an informed response, the second "problem" with the amp series has me nearly gasping for air.

What is sounds like to me is: when this amp is used with an EQ (Audyssey or otherwise) it's possible that the lower octaves will be "boosted" (to be brought more near to linear response) to the point that the amp will run into trouble and cease operation.

Is this a problem in real world use would be my next question. Seems a couple are using this with a very comparable sub to my own (The Captivator) without issues, so I'm wondering if it is.

James

You have to take test bench performance in the right context, particularly if the results relate to duty cycle type stuff. Test bench is very severe duty cycle unlike just about anything you're likely to encounter in normal use.

Exactly, who sits around listening to sine waves or whatever.
In actually program material, they are coasting along 95% of the time. If not, you would not hear it anyway as your ears would be shot.

Parts Express is where I saw the XTi 2 series. Originally they had sometime in March, but looks like they got pushed back (or sold out).

I got to thinking about the original XTi 1000s performance, and was thinking about impedance curves. So I took a second look at the original measurement, and noticed two things. First, at 8 ohms, the power dropoff at 20Hz did not show up. Second, although he said he was going to do a mono test, I never saw a mono test done. So unless I missed something, this amplifier was never tested in bridged mono.

Finally, I looked at the impedance curve for a planned build utilizing a MaelX 18" driver:



So, in the real world (the one I happen to live in) the lowest resistance the amp will see in the subsonic range is about 5.23 ohms at 12.2Hz. We don't see impedance that low again until about 5Hz, at which point other factors will be attenuating the signal.

1) Will the low frequency deficiency of the 1000 series (assuming the 1002 has not been fixed) show up here? Maybe - in a band of frequencies from 11 to 15hz, and only if playing at or near reference.

2) Will it show up in bridged mono? That particular test was overlooked, so we don't know.

3) Will it show up -10db from reference? Given that I estimate 100W to get me there (200W if running 3db hot), probably not, although we don't know it's performance down to 10Hz.

4) In those tests, distortion was limited to .5% THD. No attempt was made to re-test while allowing for more THD. At those frequencies, the THD introduced by the driver is much higher, so allowing for 1-2% THD would be a negligible difference.

It will definitely be interesting to see the 1002 retested, especially if the bridged mono test isn't overlooked this time.

As can be seen by looking at spec sheets, bridged mono results will be the same power as the sum of both channels running stereo at twice the impedance.

i.e. 8 ohm bridged mono will be the same power as 2X the output per channel (both running simultaneously) at 4 ohms.

I agree re the THD of sub drivers especially at level, but if you look at the power vs distortion curves for typical high NFB SS amplifiers, the difference in power out between 1/2 and 2% will be a small fraction of a dB typically.

Chuck's tests involve AVS members personally owned amps and his testing process attempted to operate the amps within their own advertised stated parameters. When an amp showed distress the test was terminated to avoid permanently damaging someone's volunteered amp. In the instances where an amp over performed it's ad specs, Chuck took them to the limit of DIYers levels of inquiry.
The XTi-1000 underperformed significantly and the tests were terminated without forcing the amp past degrading distortion data points into possible destruction.

^ one of my favorite words, lol:

destruction.

James

Yeah, . . . . . we don't want those little heaters to become smoldering smudge pots.

One thing I'm taking away from my little adventure of finding an amp, seperate dsp, appropriate, converting (RCA to Phoenix, Phoenix to XLR), interconnects, etc:

An amp manufacturer could prolly make a decent penny producing an amplifier (1 and 2 channel for duals) "specifically" geared to drive passive subwoofers.

One with solid low-hz output and a built-in, variable, HLP. Heck, I'm sure many have a current model that could easily be modded for such a task.

just a thought.

James

We DIYers have been encouraging designers and engineers and manufacturers to do exactly that.
Closest we got so far was Peavey with the IPR 1600. The engineer was on here, this thread, trying to get him to understand our subsonic needs.
He tried to get us to understand the need for manufacturers to make money. His point was there aren't enough of us bass heads around to support a special project sub amp.

There are nowhere near enough AV enthusiasts doing this to warrant the hassle, plus dealing with non industry professionals (amateurs, let alone audiophiles) is considerably more work.

As a miniDSP balanced is $155 and will drive two amps where realistically is the hassle? If you're going to the effort of making an integrating your own subs, this is a trivial amount of extra effort.

It is a bummer.

We tried the same with Behringer. They were taking suggestions for a modified version of the DCX to allow for filters down to 5Hz and other jazz. But, that fell through too.
However, other niche products have come to the market since, ala miniDSP.

It's the oldage, if you build it they will come.

When it comes to amps...It's not like we need a whole other product designed and engineered, etc. I mean we are talking about a slight mod(s) to add extension or handle more current, etc. So, why not come up with something and create a niche product?
The DIY community is not living on an island, some are professionals, some have other contacts in the audio community or employed in the audio related jobs, etc. Word of mouth and reputation can go a long way in promoting a company.

Do you have a miniDSP?

People are buying Berhringer amplifier because they are cheaper vs Crown IT the new and old macro tech,QSC PL serie,Labgruppen, Powersoft just to name few that are equipped with all the bell and whisles you described, just a hand full of guy are buying those amplifiers like you described here.

Is the EP4000 still the best bang for buck?

I compared the EP4000 to my American DJ V3000 amp today at avsforum member carp's house and his EP4000 seemed to be generally about 4-6dB louder than my American DJ amp on his single JTR Captivator.

The difference was significant enough for me to be interested in purchasing an EP4000, but if there is something just a wee more powerful for the same basic dollar figure, then I'm interested in looking into that too.

I will soon take delivery on a pair of JTR Captivator PRO subwoofers and don't want to limit them too terribly by my amp.



The EP4000 uses Peak ratings for it's power listings, but from what I've read it's a rebadged EP2500 which used RMS ratings.
Thus the EP4000 RMS ratings are just the EP 2500 output power specs (1 kHz, 0.1% THD) per channel stereo:
500 watts RMS @ 8 ohms,
750 watts RMS @ 4 ohms,
1,200 watts @ 2 ohms.
Output power (1 kHz, 0.1% THD)
bridged mono:
1,500 watts RMS @ 8 ohms,
2,400 watts RMS @ 4 ohms.
*Weight: 36.6 lbs. *Dimensions: 3.5" H x 19" W x 15.8" D.

I currently own a old American DJ V3000 amp which isn't too far off these marks. I found an old review where the big brother of my amp the V4000 was compared to a popular Crown amp at double the price (CROWN MACRO-TECH 2400) and not found lacking -- so that likely means that the v3000 amp does what it says it does. (Which admittedly isn't much) http://start.mobilebeat.com/archive/...php/t-154.html

It shows 1% THD instead of .1%THD
*Specifications: American DJ V3000 (1 kHz, 1.0% THD) per channel stereo:
400 watts RMS @ 8 ohms,
630 watts RMS @ 4 ohms,
800 watts RMW @ 2 ohms.
Output power (1 kHz, 1.0 % THD)
bridged mono:
1,100 watts RMS @ 8 ohms,
1,500 watts RMS @ 4 ohms.
*Weight: 35 lbs. *Dimensions: 3.5" H x 19" W x 15.9" D.


I did notice besides the SPL difference that carp had his EP4000 bridged and gain knob for channel 1 completely maxed out. When I maxed out the gain knob on my V3000 amp the sound got distorted at the same AVR volume level. I had to knock the v3000 gain back to about 80% for it to clean up the sound. At that point my sub was measuring 4-6dB less at the listening position, but the audio was clean. Is that an artifact of the higher distortion level of 1% on my sub verses .1% on the EP4000?

For the price you are going to have a hard time beating the EP4000 unless you score a deal on a good used amp. I picked up a used Face Audio F1150TX for a little more than a new EP4000 and the F1150TX is one of the best sub amps I have ever owned. I drove a pair of sealed LMS Ultra's with the F1150TX in stereo and it never left me wanting more power. I tried the same thing with the single EP4000 I have but to the same levels the EP4000 would run out of gas, it had to be used in bridged pairs to equal the single F1150TX.

Here is an interesting little note about the new Behringer INuke 3000.
http://www.behringer.com/EN/Products/NU3000DSP.aspx

From a Danish review translated by google -
"...gives 4 ohms 5625 watts peak (yes - I have calculated and measured correctly) - which is 2809 watts RMS 4 ohms."
http://www.talkbass.com/forum/f15/be...ifiers-788601/


That's a lot of power for an amp that costs $300 shipped!
or $400 shipped with a dsp.

Anybody know of a single amp preferably or two amps that will run 4 10inch DVC subs...2+2 @ 500 watts each/2000 watts total?

depending on impedance, Peavey IPR3000

I measured mine at ~1500 W/ch at 2.8 ohms IIRC; check the ipr thread

Wouldn't that be too much if I only need 1000 per channel?

not necessarily, depends on program material, room size, and your preferred listening level

I guess I have a lot to learn. I have been only using amps that have been tested on this forum as to not break anything. Is there any plans to test the MA-5050?

Hey Noah, have you written the IPR3000 up yet on a thread somewhere? I mean everything but the bench testing? I'd like to hear your impressions about it if you haven't.

I'm lucky to get in a movie per week lately, so my initial impressions still stand - sounds the same as the big iron Peavey CS4080Hz it replaced, which is a good thing.

Any idea what the xti2002 or xls2500 do In terms of real output

Is there an easy way for me to test my EP2500?
I'm not convinced both channels are outputting the same amount of power.
Or that either is delivering all the power they should be.