Passive delay/phase adjustment circuit

[Tenson]

Helloooo!

Could someone talk me through to go about making a passive circuit to adjust phase/time delay? For example, if I needed a delay of 1.6ms how do I do it?

When I say passive, ideally I mean to go between amp and woofer.

Thanks for any advice!

[macboy]

The reason noboday has repsonded to this thread is because you are literally asking the impossible. You can't do what you want to do, where you want to do it. Adjusting phase or creating delays is possible, but really only using active and/or digital circuits at line level, not after amplification.

Phase is relatively easy, at line level. Refer to project 103 on the ESP audio pages. You chose the frequency at which you want the phase effect to be 'centered' (usually the crossover frequency for the sub), and you can vary the phase from roughly 0 to 180 degress.

Delay... literally impossible (or at least impossibly impractical) to do between amp and speaker. You could in theory set up a massive transmission line consisting of alternating coils and caps, but it would be ridiculously huge and expensive. And your amp would probably not like driving it at all. The only way to get high quality delay is digitally, especially with the old-style analog bucket brigade devices (BBDs) becoming nearly impossible to find.

[leadbelly]

I think it can be done with 2 Dixie cups and a foot of string: 600 ft/s x 0.0016 s = 0.96 ft. You'll want to use the big Dixie cups and not the small ones for mouthwash. Good luck.

[Tenson]

Originally posted by leadbelly
I think it can be done with 2 Dixie cups and a foot of string: 600 ft/s x 0.0016 s = 0.96 ft. You'll want to use the big Dixie cups and not the small ones for mouthwash. Good luck.

Thanks I'll try it and let you know!

Okay I didn't think it could be done passively, but I was reading the website for the CRAW subwoofer which I swear said it has a passive delay circuit between amp and woofer. Maybe I miss-read it though I'll go back and look.


Thanks

[macboy]

Originally posted by leadbelly
I think it can be done with 2 Dixie cups and a foot of string: 600 ft/s x 0.0016 s = 0.96 ft. You'll want to use the big Dixie cups and not the small ones for mouthwash. Good luck.

Actually just do away with the dixie cups and move the sub backwards. Sound travels in air at roughly 1 ft/ms so move the sub back about 1.6 ft or 20 inches to create a 1.6 ms delay.

[lndm]

I believe that it can be done using a transmission line equivalent.

For example, take a tweeter. Place an inductor in series with each lead. Place a capacitor from the amp side of each inductor and run it to the speaker side of each opposite inductor.

There was a program out there to calculate this and if my memory isn't fooling me it was the Bullock tools package - the one with RB's TL sim in it?


Edit: the program may have been called 'delays' or similar.