Hi all. Not sure if this topic should be under DIY or not...but that's what I'm doing...is a DIY speaker project and I've got a question about active cross-overs for it.


First off...I really have no experience using an active cross-over. Sure, I've done some reading...and I've heard some systems using an active cross-over...but what are some reasons why you may or may not be using an active over passive? Is there anything to look for when buying an active cross-over...or any brands that may be better or more reliable?

I don't really want to spend a ridiculous amount of money on an active(if I get one)...but I would like to get a decent one...what would the differences be with actives...making one better than the other?

any comments...suggestions?


thanks! :D for helpin' me out.

Gone,

Back in the 70's I built the active crossover in the National Semiconductor Audio Handbook from the 70's by Dennis Bohn. It is described starting on page 5-2. It uses the National LM-356 series FET input op amps on + and - 15 volt rails. It is 3rd order Butterworth with 18 dB/octave slope. I used the LF-256 in the metal cans. There is a chart to select the frequency determining component values for the x-over frequency you want. I made mine for 500 Hz. I used my P-P ultralinear 6CA7 amp to drive Altec 511B horns and a SS marantz 240 to drive the 15" woofers.

This unit operates at line level from the output of your pre-amp and tone controls or active EQ unit and drives the inputs of your two power amps.

You have to be really careful not to allow 60 Hz hum from touching the HP power amp input with your finger or an open RCA cable, or turn-on thumps to get to the HF driver, especially if it is a compression horn driver or you can blow out the voice coil/diaphragm (since the PA is connected directly to the driver now without a passive x--over in between to provide bandpass protection).

I was very, very pleased with the performance of this circuit. I installed an input level pot and also an output level pot on each HP and LP output as well as LED drivers and LEDs to show LP and HP channel activity on all four outputs (stereo).

I could scan the pertinent pages and post here or .gif by private mail if anyone is interested.

Rob

Rob...could you either post the info...or e-mail me.


thanks

Gone, All,

Please give me a few days and I'll post this crossover info. I'm tied up on something else just now.

It will be worth the wait. ;)

cheers,
Rob

Hello Gonefishing

I am thinking of doing the same some day. Well for the most flexabillity you would want adjustable slopes, level, frequency and delay. I like LR slopes but butterworth work fine too. If you are using a horn loaded compression driver you will also want a preset for CD horn compensation. You could get by with less but you need to know what drivers and what slopes will work best with them. Have you select the speakers yet or are you going to biamp an existing pair??


Rob2:)

Marchand electronics (www.marchandelec.com) has their tube cross-over kit on sale now for $600. 24db slopes standard but can be reconfigured for 18/12/6 and frequency can be adjusted with plug in cards. Have read this can be customized to achieve horn compensation if using 12 or 6db slopes. It uses tubes so if you have a tube system, this keeps the sand out.

I might get one of these to bi-amp Altec 604s.

Billf

Well I have a BMP of the Heathkit Schematic for the active cross used for Mono. I think I found it at a Heath Site.

Find it here
<www.circuitarchive.co.uk/heath.htm>

Thanks for the suggestions guys!


For those not familiar...here is a link that describes the speakers. (hmmm...where did that link go?...here it is)

LINK (http://www.audiokarma.org/forums/showthread.php?s=&threadid=1007)

thanks :)