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-   -   Crossover suggestions? (http://www.diyaudio.com/forums/multi-way/72590-crossover-suggestions.html)

trunkmonkey 25th January 2006 06:58 PM

Crossover suggestions?
 
2 Attachment(s)
3 way system. 41 litre enclosure for the woofer. 1 litre enclosure for the mid. Sealed. Using old boxes - solid walnut sides (I think its walnut) and MDF front and back.
Woofer - Vifa PL26WR09-08
Mid - Audax AM100Z0
Tweeter - Visaton G25ND
Specs are attached

Another couple of things. Current speakers have 1/2 " recessed front baffle. Should this be changed. I could laminate MDF into the recess.

tade 26th January 2006 04:25 AM

Warning, N008 advice:

I might fill the recess with felt or some sort of open celled foam and then cover with grille cloth for pretty.

As for crossovers, I really like active because if you can get enough amp channels the electronics become very cheap. and thus experimentation becomes cheap. It will cost me less than ten dollars to change the crossover frequency, or to compensate for baffle step, or to extend bass response. I like that flexibility. I would say that limiting the amp's duty range frees it up to sound better as wel...

good luck!

trunkmonkey 26th January 2006 04:31 PM

Thanks for advise on recess. I am using these boxes until summer when I can build some new ones outside (as soon as the snow melts - wife would kill me for building them in her new basement).
As for crossovers - I do have a friend who rebuilt his Mirage OM8 crossovers and gave me his old ones. They may work or not. He works for an electronics store so building new passive crossovers will not be a cost problem. Just looking for suggestions on what type of crossover to build.

trunkmonkey 10th February 2006 04:58 PM

first crossover design
 
2 Attachment(s)
Here is my attempt at designing a crossover for the drivers above. Any comments would be greatly appreciated.

thalis 10th February 2006 06:45 PM

It’s difficult to decide without having modeled driver curves-phases. It looks a good start. I believe the upper cross freq. will be at about 2K which is perhaps too low for the tweeter – 3K would be better. Phase should probably look ok, and impedance would look relatively smooth as well.
Regards,
Thalis

trunkmonkey 10th February 2006 06:56 PM

Tweeter
 
2 Attachment(s)
Tweeter specs

trunkmonkey 10th February 2006 06:59 PM

Audax Mid
 
2 Attachment(s)
Mid

trunkmonkey 10th February 2006 07:12 PM

Woofer
 
Woofer
http://www.tymphany.com/datasheet/printview.php?id=130

thalis 11th February 2006 02:21 AM

I did a quick model of these drivers. It’s not precise: The real boxes and baffles are evidently not modeled. Drivers are modeled in the same vertical plane, mid acoustical center 1cm behind the tweeter and woofer 2,5 cm behind. Midrange is modeled in a big closed enclosure (>6 litter), Woofer’s model doesn’t matter significantly for these crossover points. I also decreased a little some cone breakups since they will get somewhat smoothed in a real enclosure.
SPL magnitude of the circuitry looks like this:

http://img380.imageshack.us/img380/4558/mag13tm.jpg

Imp magnitude:

http://img51.imageshack.us/img51/125/imp11dh.jpg

If woofer and tweeter are positively connected and the mid inverted, SPl mag will look like this:

http://img51.imageshack.us/img51/7122/mag17tc.jpg

I changed a little some values in your circuitry:

http://img380.imageshack.us/img380/8...ssover26lg.jpg

I worked things out for some baffle correction, making some assumptions regarding your baffle according to the volume you stated. So, in the next frequency responses you should consider that beyond 400-500 Hz the real loudspeaker output will be less, hopefully at about the same order with the rest frequencies (if baffle step, woofers placement and room gain come into the equation together).
So, here is the SPL mag:

http://img380.imageshack.us/img380/9494/mag23ua.jpg

And impedance will be like this:

http://img51.imageshack.us/img51/6474/imp23fc.jpg

I also worked a slightly different circuitry, adding 2 values:

http://img380.imageshack.us/img380/4...ssover34vw.jpg

With these you get this SPL response

http://img380.imageshack.us/img380/3407/mag38tl.jpg

and this impedance curve

http://img51.imageshack.us/img51/9945/imp34dn.jpg

Normaly, these two are a good starting point. In reality you shouldn’t get considerably different responses. Nevertheless you should work your enclosures, measure your drivers in them, and then some improvements could be made.
Regards,
Thalis

trunkmonkey 13th February 2006 08:30 PM

Sorry for newbie response

What does the 1% on schematics mean - is this tolerance?
Also you state that the mid was modelled in a 6L enclosure. I have a 1L (or 1.25L) bullet shaped enclosure from SEAS.

As stated before I am going to drop in the drivers in old 41L boxes and build a new enclosures this summer. Does the mid enclosure need to be this big.

All in all - do you suggest I build crossover according to your second proposal.


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