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  #1  
Old 12-04-2004, 12:04 PM
tom smith tom smith is offline
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bgw - jbl

does anyone have any experience with BGW 250 amplifiers specifically their use with JBL compression drivers.
i have a 250d bridged powering 2440 with 2445 diaphragm and it sounds pretty good but i'm a bit paranoid about damaging the diaphragm. don't really know how much they need with 800hz 18db crossover. i don't have any other suitable amps for comparison, not easy to find nice amps in england, should i seek out an alternative?
thanks
tom

BGW250.pdf

JBL 2440 driver info

JBL 2445 info

Last edited by tom smith : 12-04-2004 at 12:06 PM.
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  #2  
Old 12-04-2004, 05:46 PM
clubman5 clubman5 is offline
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BGW 250D

Its a good amp, its relaible, but how many 2440,s are you running? And why are you running the amp bridged?

I would think stereo operation would be more than enough power for your drivers!

800hz/18db is a proper crossover point!
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  #3  
Old 12-08-2004, 09:43 PM
tom smith tom smith is offline
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Re: BGW 250D

Quote:
Originally posted by clubman5
Its a good amp, its relaible, but how many 2440,s are you running? And why are you running the amp bridged?

I would think stereo operation would be more than enough power for your drivers!

800hz/18db is a proper crossover point!


I'm running a pair of mid horns each with one 2445 diaphragm in a 2440 driver.
the 2445 spec says 100W @ 500Hz and 150W @ 1KHz... my cuttoff is 800Hz - 130W? is it that simple?
BGW says 125W into 4 ohms and 100W into 8ohm in stereo operation... what will it provide a 16 ohm diaphragm?
I will stop bridging my amp... don't want to damage these. but do want to get best performance so thanks for your response scott.

tom

Last edited by tom smith : 12-08-2004 at 09:45 PM.
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  #4  
Old 12-09-2004, 03:25 PM
clubman5 clubman5 is offline
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Power specs!

Power specs on amplifiers are so misleading! The FTC rating 20hz-20khz is the true RMS, continuous power the amp can deliver at a rated impedance. 1Khz power is the amp being driven at that specific frequency, most amps deliver somewhat higher power at 1k THAN at 50HZ, so they use this rating to make things look good! The continuos pwer rating is the one to look at!

The impedance of your load ( drivers ) determines what the impedance the amp sees is, so if your using 8 ohm drivers, 1 per channel of the BGW, you have 100 watts per driver, and more on transients, and the amp will be able to produce slightly higher power in this frequency range, than if you were running a woofer from 80hz and down! At 16ohms the amp should produce about half or a little more than half the rated 8 ohm power, which should be more than enough for you!

To me, you have very adequate power for two compression drivers, 1 per channel, and should be able to get plenty of sound, without having to crank that amp much, in stereo operation!

If your using an 18db or steeper filter, 800Hz is a proper xover point, and you should have no problems!

Your drivers diaphragm can handle more power at higher frequencies, less at lower frequencies, this is due to the excursion limits of the diaphragm, but I dont think you need to have 150w per driver, you have plenty with the rated 100w per driver, as the efficiency of these drivers on proper horn is extremely high, Ill bet youll never crank that too hard at all!

All in all, running that amp in stereo, you are properly powered!
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Last edited by clubman5 : 12-09-2004 at 03:27 PM.
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  #5  
Old 12-10-2004, 12:10 PM
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daveg daveg is offline
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bgw etc

How is your high efficiency system sounding Tom?

I have nothing much to add to Scotts comments. The 2441 should be the most efficent components of your system (112db/1watt at least on that 36 inch plate horn) so adjust gain to match those components. They should sound smooth, detailed and clear. You won't damage these unless you are stupid run your amp flat out to create 130db plus of screaming and disorted mid. Don't feel you need to drive at 100 watts just because they are rated as such, the majority of alternative drivers from EV,B&C etc will be rated much lower but do the same job as the 2441.

Oh, you might want a high voltage 40 uf cap in series with the driver to protect from turn on pops or such in your system.

I suspose you might have read on another forum to use a MA 5000 or PLX 3402 but probably best to use good sounding amp rather than powerhouse amp.
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  #6  
Old 12-13-2004, 09:50 PM
tom smith tom smith is offline
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Re: bgw etc

Thanks Dave & Scott for your help, things are sounding pretty good, though i still have a long way to go... and progress is slow. experimenting with this gear is hard in the UK as you can't find much and there are no sounds around that are comparable in terms of their approach.
Quote:
Oh, you might want a high voltage 40 uf cap in series with the driver to protect from turn on pops or such in your system.


i have a 400V 22microfarrad capacitor in use on each 16ohm driver, will that do?
Thanks
tom

Last edited by tom smith : 12-13-2004 at 09:53 PM.
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  #7  
Old 12-14-2004, 06:01 PM
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cap

That cap will do the job. If you want to add a bypass cap as well then read up on that other JBL forum for ideas and see if its worth it. Bypass caps used on many production JBL.

I would expect your mids and high to be sounding very good unless something major is amiss. Not sure what happened on the bass dept?

I suspose you could pop in to a Hi Fi shop with a CD and see if your system is missing something soundwise. Scott is the Altec man here but your type of system was often used here albeit twenty years ago so there will be the older sound people around into these.
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  #8  
Old 12-14-2004, 06:37 PM
clubman5 clubman5 is offline
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Scotts system!

Scott uses altec 15,s but everything else is JBL!

For bypassing, talk to Earl K or Giskard on lansing heritage! There are others too! This site has some really fantastic minds, engineering skills, couple of guys that are masters at cabinet refinishing, in general a great place for JBL info!
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  #9  
Old 12-14-2004, 06:41 PM
Acidtension Acidtension is offline
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Scott

u've got mail
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  #10  
Old 12-14-2004, 06:49 PM
clubman5 clubman5 is offline
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Re: Scott

Quote:
Originally posted by Bozaureik
u've got mail
I picked up my mail!

Where are the pictures of the naked women spinning on urei,s I ordered?
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  #11  
Old 12-14-2004, 07:11 PM
Acidtension Acidtension is offline
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Re: Re: Scott

Quote:
Originally posted by clubman5
I picked up my mail!

Where are the pictures of the naked women spinning on urei,s I ordered?

I remember some years ago being sent some pics of two lesbo's wearing the sony phones and spinning on a pair of Technics (though the mixer was something like a Numark... so... we can conclude that they were poor quality Lesbos)
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  #12  
Old 12-15-2004, 03:39 PM
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daveg daveg is offline
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Altec 15

Well Scott might be able to confirm that A7 and 2 inch horn should sound more than pretty good? Perhaps something is amiss or they need careful EQ to sound good.
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  #13  
Old 12-15-2004, 03:46 PM
clubman5 clubman5 is offline
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Re: Altec 15

Quote:
Originally posted by daveg
Well Scott might be able to confirm that A7 and 2 inch horn should sound more than pretty good? Perhaps something is amiss or they need careful EQ to sound good.
Is an A7 what hes using? If so with what woofer is it loaded?

EQ is nice to have, tame a peak or two!

I love Altec cabinets with associated woofers, combined with JBL horns and tweeters!
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  #14  
Old 12-15-2004, 06:06 PM
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A7

I'm sure we will find out which woofers. Tom has posted specs here or on PM before.

Are Altec's polarity as JBL,positive on red goes makes cone foward?

Just a possible silly error if they are not.
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  #15  
Old 12-15-2004, 06:17 PM
clubman5 clubman5 is offline
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Re: A7

Quote:
Originally posted by daveg
I'm sure we will find out which woofers. Tom has posted specs here or on PM before.

Are Altec's polarity as JBL,positive on red goes makes cone foward?

Just a possible silly error if they are not.
Vintage JBL is black positive, for forawrd motion, Altec is Red positive!
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  #16  
Old 12-16-2004, 07:59 AM
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Polarity

I was got that wrong myself then! Scott is correct. Good job all my speakers are JBL of a older era with the same polarity convention.
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  #17  
Old 12-18-2004, 11:16 AM
tom smith tom smith is offline
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Re: Re: A7

Thanks for the information about bypassing the capacitors - another thing to bear in mind.
The altec A7 are loaded with 515 8ghp at the moment, driven by BGW GTA in stereo operation, one 515 woofer on each channel.
Quote:
Originally posted by clubman5
Vintage JBL is black positive, for forward motion, Altec is Red positive!

I will change with the polarity, but i don't live where the system is stored so thing are slo.
I intend to use some urei 27 band cut eq but haven't installed them yet, don't feel things are at that stage yet.
Does David Mancuso do any events in NY still?

thanks
tom

Last edited by tom smith : 12-18-2004 at 11:28 AM.
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