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Old 4th April 2006, 18:47   #1
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Default Power Rating of Amp. (1141rms at 4ohms, 1022rms at 1ohms)

334 watts RMS x 2 channel at 4 ohms and ≤ 1% THD + N

1141 watts RMS x 1 channel at 4 ohms,14.4V supply and ≤ 1% THD + N

1022 watts RMS x 1 channel at 1 ohm, 14.4V supply and ≤ 1% THD + N


these are the specs of jbl BPX1100.1 1100 Watt Subwoofer Amplifier from the website can some one explain how come the amp is giving 1141 rms in to 4 ohms but 1022 watts in 1 ohm it should increase than 4 ohms. One more thing this is a current base amp ,and there are voltage base amp what diff does the have.
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Old 5th April 2006, 10:28   #2
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current dumping limitaiton - extremely poor power supply
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Old 5th April 2006, 13:04   #3
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Quote:
Originally Posted by navin
current dumping limitaiton - extremely poor power supply
It means the amp is not good at lower ohms rating and will not will be able drive multi sub systems. This are the spec of jbl-crown series amp, which where used in the great eyeballer palio. I have heard the palio myself the person giving the demo had no knowledge of the audio stuff installed in the car i myself adjusted the hu myself and listened to the sound. it was nice. but one thing i did not like was the external power supply. why man ? if make a car make it in itsself no extrenal power sources should be used.

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Old 5th April 2006, 13:14   #4
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When the word Crown comes up in any conversation I relook at my theory. Crown amps are behemoths. I have seen them being used to magnetize rare earth magnets (providing as much as 140A into DC). so I relooked at my earlier rushed statement...here is what i found...BTW Harmon Intl owns both JBL and Crown as well as Infinity and Revel and a few other brands.

1141W @ 4ohms = 17A
1022W @ 1 ohms = 32A

not exactly a slouch but yes if the power supply or output transistors permited it it could have dumped even more current. looks like the current is limited to 32A.

most amps are volt amps. they should double power as impedance is halved. 100W@8 ohms = 28V, 200W@ 4ohms = 28V, 400W@2ohms = 28V and so on. Now if you relate 400W@2ohms which is a lot of power you see that the current is only 14A! still a bit less than the above mentioned Crown amp.

current based amps are those where the current is controlled and hence you see that the current is limited to 32A. usually this is done using a tightly regualted power supply. the advatange is that such amps seem to manage reactive loads better than volt amps. reason being is that as the impedance of a reactive load rises or falls the watts are the same. As you can see in teh above example the Watts at 4ohms and 1 ohms are almost the same.

LBM, 32A is a lot of current. It would require 8 (4+4) Hitachi SJ50/SK135 Mosfets to dump that much current and only the metal body ones would disappate the heat properly over the long term.
see pic on post #1 here
http://www.diyaudio.com/forums/showt...294&highlight=

Last edited by navin : 5th April 2006 at 13:37.
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Old 5th April 2006, 13:22   #5
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Quote:
Originally Posted by low_bass_makker
It means the amp is not good at lower ohms rating and will not will be able drive multi sub systems. This are the spec of jbl-crown series amp, which where used in the great eyeballer palio. I have heard the palio myself the person giving the demo had no knowledge of the audio stuff installed in the car i myself adjusted the hu myself and listened to the sound. it was nice. but one thing i did not like was the external power supply. why man ? if make a car make it in itsself no extrenal power sources should be used.
Hi LBM,
The Eyeballer was not designed for normal usage. It was able to run in a car that was running (the alternator current would be added). Ideally it would have needed 2 or 3 batteries (for current) and a charging system that would complement the power supply.
However please consider that it was used at various shows, many indoors. With the exhaust and the heat of a running car, it was a nightmare. So the external power was used. (125Amps 12V)
And the current limitations are assuming you use it in your car.
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Old 5th April 2006, 13:47   #6
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BTW I must admit I am a biased person. I am fond of crown. I dont own one but have heard them and seem do some darn impossible things (for amplifiers).

The 2SJ50/2SK135 Mosfets mentioned above are not used by Crown but by me in my own home made car and home amps.
http://www.sjostromaudio.com/datashe..._datasheet.pdf
http://www.sjostromaudio.com/datashe..._datasheet.pdf

these are great devices but over long term I would not use expect more than 4A out of each of them (v/s 7A as speced) unless you got fan or oil coolling.
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Old 5th April 2006, 16:29   #7
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Quote:
Originally Posted by low_bass_makker
but one thing i did not like was the external power supply. why man ? if make a car make it in itsself no extrenal power sources should be used.
FYI the external power supplies are used during exhibitions and indoor demos. As it is important to keep the engine running for charging the car battery. So in indoor places to avoid the exhaust fumes the external power supplies are used. There is nothing like liking or disliking as it makes no difference in sound its just a convenience.

I have seen the Eyeballer setup and I don't think car electricals should have any problem handling that with engine on.

Last edited by Autophile : 5th April 2006 at 16:30.
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Old 5th April 2006, 18:44   #8
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One more thing did the eyeballer had sealed box for the sub and what volume they had ?
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