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-   -   Help with Veeper tweeker (http://www.diyaudio.com/forums/multi-way/228143-help-veeper-tweeker.html)

bart_dood 19th January 2013 04:13 AM

Help with Veeper tweeker
 
1 Attachment(s)
Hey folks, I am building a two way with Peerless 830875 woofers and Vifa PL27TG35-06 tweeters.

I'm close to having the cabinet's finished and I've been looking around at similar projects to get an idea for the crossover (basically trying to find something really close and do some tweaks).
I found a project at this URL:

Veeper TM Monitor

They are really close, very close volume of cabinet, almost the same FB, same woofers and tweeters that are very close.
My question is can anyone give me a pointer on what to adjust on the tweeter crossover for my slightly different tweeter? The basic differences are:

My tweeter is 0.5db less efficient (insignificant?)
Impedance of my tweeter is 6 ohms Vs 3.6 ohms for the veepers

Everything else is pretty darn close, even the frequency response. I'll attach the veeper crossover diagram for your reference. I'm thinking of copying the woofer crossover part exactly, I'm guessing I just need a resistor change on the tweeter portion to deal with the slightly different impendance of my tweeters (2 ohms more).

Am I correct in just needing a resistor tweak? If so which should I change, thanks!!

Chris

Dissi 20th January 2013 12:45 AM

2 Attachment(s)
A crossover proposal:

Attachment 325121

Attachment 325122

prairieboy 20th January 2013 01:48 AM

Question I have to ask:
Is your objective to have a good, proven, speaker? If so, buy the Vifa tweeter, make the Veeper and live happily ever after.
Or
Do you want to learn about designing a crossover? Is so, don't copy Lou's Veeper, but check out this forum, and design your own. http://www.diyaudio.com/forums/multi...asurement.html

bart_dood 20th January 2013 06:58 AM

Thanks guys, I think I should learn more about crossover design myself but I appreciate your help. Dissi I will study this and try it out in my model, I'm trying "the passive crossover design 7.0" in excel.
So far I've managed to put together a 2nd order from parts from my old speakers and they work very well although they are not optimal. I'll experiment some more before ordering the proper components!

Pascal GUERIN 20th January 2013 08:21 AM

Hi Chris,

You should post your simulations done with PCD :)

The two design I know using the 830875 use a ~3 khz crossover with LR24 slopes.
Set it as target in PCD and play with values coming from textbook calculations (Initialise textbook values).

system7 20th January 2013 02:19 PM

3 Attachment(s)
Quite an interesting bass driver, the Peerless 830875. It has some breakup rubbish around 4-6kHz that our Troels found merited a notch:

PEERLESS-NOMEX-164

He uses a "Tank" at 6.1kHz here across the bass coil to drop the troublesome cone breakup about 6dB. I fancied that 10uF was a bit steep with Veepers 1.5mH. Changed to 6.8uF and 1.5R, much the same as Troels did. The tweeter crossover looks fairly generic with 6 ohm 90dB tweeters and phase matching is nice. An 87dB tweeter would probably get away with second order and lose the 10uF, and have a smaller 3 ohms at the filter input to match levels.

For those who can't do this notch stuff in their head: Alan Yates' Laboratory - VK2ZAY's Engineering Calculators - LCR Resonance

The value of a tank capacitor varies with the bass coil, but I see no point in making it too deep. I've ended up with a 6.1kHz notch just like Troels. He knows what he's doing. :)

bart_dood 20th January 2013 05:59 PM

Here's some sims PCD
 
2 Attachment(s)
So I'm trying to understand phase on the tweeter on a 2nd order filter, from what I understand the tweeter should be flipped because on the first plot below the phase is 180 degrees from the woofer at the crossover point?

Flipping the phase means having to adjust the crossover and gives a phase profile that gradually slopes, this is more ideal?

bart_dood 21st January 2013 04:27 AM

Can anyone help me with this phase question? I searched and can't find it specifically explained. Thanks!

bart_dood 21st January 2013 10:41 PM

Can someone just confirm
 
1 Attachment(s)
That the phase in this plot looks correct? IE there are not supposed to be any reversals etc, esp around the crossover point?

Thanks

bart_dood 22nd January 2013 02:59 AM

2 Attachment(s)
Think I'm getting the hang of this a bit more now, Dissi I modelled up your Xover in PCD7.0 and then my crossover. Here's the comparison, yours is about 86db and mine about 90db.


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