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Old 22nd February 2004, 05:33 PM   #1
Speakerholic
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Default Here's where you guys can really help me... Bi-amping

This is my first attempt at bi-amping and I'm awfully green. In fact I don't even deserve a colour.
This is my first thought:

I will use my H/K (55wpc) as a pre-amp. I am thinking of running the pre-out to an active crossover and then to a Carver cube (400-500wpc) on each woofer (97dB @ 1 w). I want to then take the high end and put it back through the pre-in on the H/K for the tweeters (108 dB @ 1 w). I am thinking that with the difference in sensitivity, this might be a good match.

Please comment on this part, then tell me about the active crossover. I have no idea of good from bad. It would be great to be able to order from Parts Express.

I don't even know the difference between what they call an electronic crossover and a signal processer

Is this something I could use?

Active crossover

Thank you for your input, I'm not looking to wing it this time.

Cal
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Old 22nd February 2004, 06:07 PM   #2
sreten is offline sreten  United Kingdom
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JMO but I wouldn't hold out for too much tonal purity using a
carver cube for midrange.

Your sensitivity vs power arrangements sound perfectly sensible.

But the whole arrangement seems over SPL'ed for domestic use.

I've looked at the specs for the Beringher, will work, but you'll
still need to add pre-eq between pre-out and the c/o for baffle
step compensation and any tonal tweaking of the bass/mid.

sreten.
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Old 22nd February 2004, 06:12 PM   #3
JohnSz is offline JohnSz  United States
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Well, I haven't ever biamped, but thought about it many times

Quote:
I want to then take the high end and put it back through the pre-in on the H/K for the tweeters
You need to feed it back to the "main in", not pre-in jacks. Not sure if your HK has main ins. On models that have it, there is usually a jumper bar between pre-out and main-ins.
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Old 22nd February 2004, 06:28 PM   #4
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Hi sreten,

These are for outdoor PA use. Purity and tonal quality take a back seat here.

Baffle step compensation? Is that like time alignment? The coils are already in line, this is in an A7 box.

If need be, I can ad an EQ at a later date. No?

Hi JohnSz,

You're right it's the Main-ins I will be using. Pre-ins meant only as a generic term.

Thanks to you both,

Cal
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Old 22nd February 2004, 06:41 PM   #5
Ken L is offline Ken L  United States
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Default Re: Here's where you guys can really help me... Bi-amping

Quote:
Originally posted by Cal Weldon
Please comment on this part, then tell me about the active crossover.
Cal
Umm, well I think you're putting the cart before the horse here _grin_

Let's talk active crossover and that should get you further down the road.

I suggest you either go with a Marchand active crossover or a Behringer digital DCX 2496. or possibly a Driverack PA unit

You really need to go as high a quality here as you can because you're introducing an extra liink in the chain and your sound will only be as good as the weakest link in the chain.

The active crossover will have adjustments that will take care of gain matching.

Quote:
Originally posted by Cal Weldon
I want to then take the high end and put it back through the pre-in
I either don't understand what you are saying here or it doesn't work this way.

you come out of the preamp with one set of interconnects into the active crossover - the active crossover does the gain matching and crossover functions and splits the signal - leaving the crossover you have two pair of line level interconnects, each pair will go into the inputs of one power amp.

There was a post in another forum recently about the particular Behringer unit that you linked to. The poster was unhappy with the quality, and said it was unsuitable. Another poster was happy with his unit.

We all have different budgets and timing for purchases of things in our hobby of audio.

If you go as high a quality as possible with the crossover, it should remain with you for some time as you change out amps, preamps, etc. as you go along on the path of continual upgrade that we seem to follow _big grin_

There are several threads here on the Behringer -

Active pro crossovers that are not in the digital domain - such as Behringer, Rane and similar units have a questionable reputation for use in high resolution home audio systems.

I was one of the early adopters of the DCX 2496 and have been happy with it - some users have had problems with low-level noise - I have a need for delay in this configuration so in my case I needed to go digital. Most people do not need delay, and could do quite well with a marchand or similar unit.

The great thing about going digital is tremendous flexibility to match your current setup and then can make changes for future configurations.

DCX2496 can be had for $325.00 to your door in the US, I have seen Driverack PA on E-bay for under $400.

Marchand has a number of kits and configurations- and frequently turn up used on Audiogon.

The DCX2496 also has EQ functions that can easily do the EQ Sreten mentioned.

I am a beleiver that digital crossovers are the way of the future and that they are in their infancy for high resolution home audio. This means also that they will have growing pains that go along with it.

Regards

Ken L

I'm too slow typing - looks like there were posts while I was composing _grin_
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Old 22nd February 2004, 07:07 PM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Cal Weldon
Hi sreten,

Baffle step compensation? Cal
For PA use a phenomena usually completely ignored.

So you shouldn't buck the trend.

It is important in hi-fi especially when the amp has no
tone controls.

But if your really keen search for the term on the web.

sreten.
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Old 23rd February 2004, 11:48 AM   #7
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OK well Ill fill in the blanks and say what baffle step is.

Basically a loudspeaker radiates every sound it produces in the high frequencies forwards from the drive units out to the listener. But at lower frequencies the sound starts to radiate round the back of the enclosure. If you have listened to a loudspeaker from behind you may notice that you dont get as much high frequencies the lows, this is because of this.

What happens is above certain frequencies the speaker radiates 2pi and at others 4pi, when this happens is determined by the width of the front baffle. As the wavelength of high frequencies is small in comparison to the baffle width they all fly foward. But as the wavelength goes beyond the baffle width the sound starts to "Creep" and bend round the sides of the cabinet. This means you get some sound going direct to the listener and some dissapearing round the back of the speaker.

http://www.seas.no/excel_line/excel/e0015.pdf

look at this data sheet from seas, it highlites BS brilliantly.

As you can see here the frequency response starts to decrease in SPL at about 800hz, which is odd because this is a bass driver and can easily operated below this keeping up the SLP. The driver can operated lower then this before the roll off in the bass, look further along at about 150hz, you'll notice that the response evens out again, then rolls off as you would expect at about 100hz. This roll off between 150 and 800hz is due to baffle step.

Bare in mind that theoretically BS gives a slow roll off to the tune of 6dB from start to finish. In the real world however you get some gain from the room so the full 6 isnt normally required, usually 3dB will suffice.

I hope thats clear, I have a really hard time making things coherent.

Matt
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Old 23rd February 2004, 11:54 AM   #8
navin is offline navin  India
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Default Re: Here's where you guys can really help me... Bi-amping

Quote:
Originally posted by Cal Weldon
I will use my H/K (55wpc) as a pre-amp. I am thinking of running the pre-out to an active crossover and then to a Carver cube (400-500wpc) on each woofer (97dB @ 1 w). I want to then take the high end and put it back through the pre-in on the H/K for the tweeters (108 dB @ 1 w). Cal
u can macth the levels on the XO. just check our H/K has power in not pre in. pre in is for additional line level sources.

i checked the back of a vintage (1987) H/K amp (PM665) and sw it has pre out and power in. i hope yours is similar.
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Old 23rd February 2004, 06:23 PM   #9
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Thanks to Ken L,

I won't need to worry about upgrading amps etc. I should have explained these are my personal speakers, not used for pro PA. I believe the digital is a bit more than is required for the set-up at this time.

Thanks to sreten,

I believe you are the one who understands what I am attempting with the back feed into the H/K the best

Thanks to 5th element,

That makes baffle step compensation easier to understand.

Thanks to navin,

I will be using the level adjusters on the xover for my final matching.

Let me explain once more what I intend to do for those a little confused at this point:

My H/K AVR40 receiver will be used as a pre-amp AND an amp.

The low voltage output (pre-amp) will go to the new active Xover.

The bass frequencies low voltage output from the Xover will be split into two Carver cubes, one for each woofer.

The low voltage high frequencies from the new Xover will be taken back into the H/K low voltage input. The tweeters will then be run from the main speaker terminals in the H/K. I will not be running any high voltage back into the H/K.

I though that the sensitivity of the drivers would match well with the differences in the wattage.

I will do my final adjusting of the woofer/tweeter levels on the new Xover.

So I will have 55wpc into the tweeters, 500wpc into the woofers.

Hope this clarifies some issues.

Thank again for your inputs, bring on more!

Cal
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Old 23rd February 2004, 10:17 PM   #10
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Quote:
Originally posted by sreten
I wouldn't hold out for too much tonal purity using a
carver cube for midrange.
My experience with the Carver Cubes is that they put out a lot less power into a real world speaker than their ratings indicate -- just a heads up. (an NAD 3020 embarassed a 1st gen cube in power output before audible clipping)

dave
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