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Crown amp [message #82806]

Thu, 09 June 2016 15:13

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Hey Wayne!

How do you think this class d (I believe) Crown amp would work for a pair of 3 pi subs?

http://www.crownaudio.com/en/products/xls-1002

Instead of using an old Adcom power amp I own, and trying to integrate passive line crossovers and a gain control knob,
Im looking for something that has a low pass crossover capability and gain control built in.

Might this work, or is it better to use plate amps?

Am I correct in thinking that uber quality amplififcation is not necessary for distant subs and/or flanking subs, vs. the front mains?

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Re: Crown amp [message #82807 is a reply to message #82806]

Thu, 09 June 2016 16:00

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

I think those amps work very well for subs.

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Re: Crown amp [message #82808 is a reply to message #82806]

Thu, 09 June 2016 16:10

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Thanks.

Do the 3pi sub speaker kits still use the Eminence lab 12,
and are these kits currently available?

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Re: Crown amp [message #82809 is a reply to message #82808]

Thu, 09 June 2016 16:41

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

Yes to both questions. They are very popular.

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Re: Crown amp [message #82824 is a reply to message #82806]

Mon, 13 June 2016 14:49

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Another question on helper sub amplification-

If I were to try and use my old Adcom 555 amp for a pair of 3pi subs, while using a low pass, line level 100hz crossover,
must I apply some kind of high pass crossover protection as well?

I have seen high pass crossovers designed in amplifiers,
I assume, to prevent over-excursion of the subs.

I notice a lot of plate amps, and even the crown amps I asked about in my post above have this.
I wonder if it is necessary with the 3pi's?

I seriously doubt that my 1985 ADcom amp has this. I did have the amp modified by Jim Williams at Audio Upgrades.
Here is a quote of his from another site, explaining some of his mods to the Adcom's-

"There are only 8 el caps in that design. 4 are the large mains filter caps, no need to change those. 2 are bias filters at 4.7 uf, I use Nichicon HE sreies 6.8 uf.The 2 remaining caps are in the gain set stage, 47 uf/100v. Those are in the audio path. I use 220 uf 100V Nichicon HE series with premium film caps added. That extends the low end to below 5 hz and removes a bit of phase shift."

As you can see, The low end capability is below 5hz Shocked

I did run my 4pi's with this Adcom for quite a while, with no problems that Im aware of.

Can anyone advise?

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Re: Crown amp [message #82825 is a reply to message #82824]

Mon, 13 June 2016 16:40

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

I generally run the mains full-range unless I'm really pushing the power to them. For home hifi and home theater, no high-pass is needed.

When doing prosound work, I'd recommend high-pass for the mains at the Helmholtz frequency. That's because the speakers are being pushed harder, nearer their limits.

Indoor home levels are nowhere near this, most times less than 1/100th their capability. Still, you could run a high-pass at the Helmholtz frequency because there is no output below anyway. It's just that it isn't required at moderate listening levels.

That's all true for subs as well as mains. Most people don't high-pass subs but vented and horn-loaded speakers unload below their passbands. They don't provide significant output below their passbands and excursion rises, so if they're pushed hard, high-pass is a good idea. Not necessary at lower levels, but still not a bad idea.

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Re: Crown amp [message #82830 is a reply to message #82806]

Wed, 15 June 2016 17:23

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Thanks for that explanation Wayne.
I suspected as much, and this saves me some time not bothering with a high pass filter.

I may get started on my 3pi sub boxes next week.
Could you please send me the plans?

Regards!

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