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Old 20th July 2007, 08:48 PM   #1
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Default Setting up a ESP active crossover with gainclone

Hi guys,

I'm after a little advice please,

I've just finished one channel of my active bi-amp gainclone setup.
I have built the ESP LR crossover in 2 way mode and am feeding it into 4 peter daniel premium LM3875's (dual 25V trafo 300VA into 6Ohm speakers)

Now, I have tested the gainclones as monoblocks without any active crossover and was really impressed by the sound.
I also fed the crossover into my 6ch surround amplfier (using separate speaker for L hi L low etc) which also impressed me (absolutly no noticeable coloration or hiss hum etc.)

Naturally when it came to testing the two together I expected to be blown away, but ermm wasnt!

Sounds good (cant really be more precise at the mo) but not quite what I think it can do .

I notice the ajustable level for each output on the LR crossover could someone point me in the direction as how to set it up both simple and also correctly (doing it 'by ear' doesnt seem to be great, I cant decide on a particular level)

I havent yet removed the existing crossovers (but have tested the channel with two separate speakers i.e low output fed into whole crossover on speaker so not to feed 300Hz into 2Khz Xover etc)

Or is it just me rushing it and need to wait until I finish the other chanel to be truly amazed?

Thanks

Dan
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Old 20th July 2007, 11:42 PM   #2
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Default Re: Setting up a ESP active crossover with gainclone

Quote:
Originally posted by Dan_Steele

I havent yet removed the existing crossovers (but have tested the channel with two separate speakers i.e low output fed into whole crossover on speaker so not to feed 300Hz into 2Khz Xover etc)
Hi,
I'm doing a similar project:
Active filter plus LM3886 - one board

You probably will get better results with the crossover out. What are the speakers?
You mention the low frequency, but what did you do with the high? Letting these signals go through a passive crossover will show no impovement., about the same as bi-amping.
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Old 21st July 2007, 09:16 AM   #3
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Speakers are Jamo E800 series, I have both the E800 bookshelf and E850 floorstanders. Cost around 1000 for the 4 about 3 years ago.

The set up I have for testing at the moment involves sitting the bookshelf ontop of the floorstander and leaving the bi-wire links in. The putting the low into the floor stander and high into the bookshelf.

I think I will have a go at removing the crossover today in one of the bookshelf's( I initally left them in as I figured they would serve some kind of protection for the speakers during testing)
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Old 22nd July 2007, 01:11 PM   #4
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Bit of an update:

Removed the crossover from the bookshelf..

Was a bit nervous at first, feeding 300Hz into a tweeter didnt seem right in my newbie(ish) books at first, also considering I havent implemented any delay in the amp outputs (maunaly connect after a few seconds) or speaker protection circuitry.

Still seemed a little under what i expected, but then I connected my heavily modded playstation (linear PSU, new output from dac etc etc)

Anyway, it now sings!!! Little bit of hum (seems dependant on where the phono input cable to the amps is located) but im sure I'll figure it out.

Would still be nice to have some kind of numerical setup on the crossover tho.

Regards

Dan
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Old 22nd July 2007, 05:09 PM   #5
BWRX is offline BWRX  United States
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Hold on there Dan. You're feeding frequencies as low as 300Hz directly into a tweeter? You shouldn't be doing that!

On the ESP site the 3 way active crossover is meant to be used with a 3 way system - everything below 300Hz is sent to the woofer amp, 300Hz-3kHz is sent to the midrange amp, and 3kHz on up is sent to the tweeter amp. If you're doing a two way with a midrange and a tweeter you would send everything below 3Khz to the midrange and everything above 3kHz to the tweeter. Most tweeters are not meant to reproduce frequencies below 1-2kHz.
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Old 22nd July 2007, 05:17 PM   #6
AndrewT is offline AndrewT  Scotland
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I see a new thread coming.
It might be titled " how do I rewire my tweeter"
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Old 22nd July 2007, 10:02 PM   #7
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hmm yeah kinda what i thought! I will have a look tomoro to see if i can recalcalatlate the components. Is 3khz a generally accepted value? Can see me having problems getting info regarding the tweeter & optimum frequency response being a purchased speaker and all. It sounds so good tho (hopefuly indication that no damage has occured )

Dan
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Old 22nd July 2007, 10:28 PM   #8
BWRX is offline BWRX  United States
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Most commercial two way designs with a ~1" tweeter and a 5.25-6" mid/woofer have a crossover frequency in the 1-3kHz range. You can use your computer as a source and generate test tones while only driving one driver at a time to try and determine by ear the approximate crossover frequency for your Jamo E800's.
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Old 22nd July 2007, 10:48 PM   #9
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Quote:
Originally posted by BWRX
Hold on there Dan. You're feeding frequencies as low as 300Hz directly into a tweeter? You shouldn't be doing that!

On the ESP site...

Dan seems to be following what is found on the ESP site for two-way. A cross at 310Hz.

Quote:
"Figure 1A shows the general concept for a full stereo version, with two identical filter sections (but without balanced inputs). With the component values shown, these have a crossover frequency of 310Hz (refer to the article on Bi-Amping to see the reason for my choice of frequency). "

A mistake?
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Old 23rd July 2007, 12:02 AM   #10
BWRX is offline BWRX  United States
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It's not a mistake. Have a look at his article on bi-amping and check out section 1.0. The first figure tells all. When he mentions a two-way crossover at 310Hz he intends it to be used to separate low frequencies for a woofer amp and mid/high frequencies for a mid/tweeter amp. His diagram clearly shows a passive crossover to split the frequencies for the midrange and tweeter. He explains why he chose to do that further down the article. If you're going to bi-amp a midrange and tweeter you will need to choose a higher crossover frequency. You run a high risk of frying a tweeter if you cross it over at 300Hz!
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