5 Way Crossover design *HELP!*

[beeferer]

I have a pair of Infinity Reference Standard II's and I want to build new crossovers since they are over 30 years old and I am sure the electrolytes have dried up long ago. The crossover points are 60, 125, 1500, and 3000 Hz and all seven drivers are 4 ohm. I am looking to build a second order Butterworth 5 way crossover, unless of course someone can talk me into some other route. Replacing the caps is not an option. (Anyone know where I can get a 1600uF 100VNP 85C metalized polypropylene cap? Me neither.)

[Cal Weldon]

Thread moved to Multi-Way

[Cal Weldon]

Geez, that looks like fun. You can always parallel some caps to get the value you need.

[beeferer]

Thank you Cal-Your version includes the 600uF cap that Infinity Systems omitted in the drawing that they sent me. Would metalized Polypropylene caps be the way to go?

[Cal Weldon]

I am not the person to ask as I use all sorts in my XO's including the ones "they say" you're not supposed to. Especially the larger value ones.

[Cal Weldon]

Any chance you could use something like this or is this polarized? I don't know these things I just googled 1600 mfd caps.

MALLORY CGS162T400X4C3PH CGS 1600 MFD 400 VDC CAPACITOR | eBay

[AllenB]

I'd also parallel some electrolytics for that large one. I'd try to use the same type/value together. The other option would be an active crossover at that low point.

[beeferer]

Thank you all for your suggestions. The low end doesn't have much work to do. To find out why, the 18" sub here takes care of things:http://www.diyaudio.com/forums/gallery/showphoto.php/photo/4765[/URL]

[T101]

Infinity Reference Standard II B and II A Loudspeakers

Let me say, that I am a little skeptical about the outcome of altering the crossover of these.
For instance, you could see that the two outer mids are crossed lower and the inner is crossed higher, thus forming a sound column, but also mimicking one single driver that has one single acoustic center. Every driver will narrow it's emitting surface (diameter) as the frequency rises.

In the link above, you will find the schematics for the bass equalizing unit if you do not have one.

A pair of these and a whole day listening session were one of the reasons for the ignition of my interest in this hobby. They were bi amped with a 500W Krell and a 500W Accuphase with Accuphase tube preamp... For the next year and a half or so, I was approaching the owner with various offers about the whole system, he never agreed to sell even though he is a professional audio equipment seller and those were in his showroom. the components even had a price tags, but he said that he'll sell when he gets better system... five years later, he still haven't sold these

In addition, they are quazy acoustic suspension as the bass cabinet is ported with a port against the floor, so it is some sort of aperiodic enclosure.

From the crossover diagram Cal posted, it seems that the woofers have considerable coil inductance and considerable equivalent capacitance of the suspension and moving assembly. If you model a high mass, low QTS, low Fs, high Qms woofer with considerable Le in a software such as Bass Box, you'll find out that ordinary second order crossovers will induce or might induce a resonance peak at the crossover frequency and another resonance peak is possible several octaves above. I suppose that the top woofer circuit is designed to handle those issues - 5Mh+1,8Mh+125mf all shorted by Re and Le of the top woofer
Not to mention that both woofers in parallel with single crossover would produce allot more midbass than desired.

If I were you, I would restore the original crossover and obtain or build the bass eq unit if I didn't have one.

Also, those have a stated 25hz-25khz range and 29hz-25khz @+/- 2 db... Your 18 inch woofer might be loud, but does it do 25-29 hz @ -2 db?

Best Regards!

[beeferer]

I do not own either of the systems you have in your link- I have the original RS II's- not II A or II B. Also, I run the sub through an Audio Source Richter Scale active crossover. Using a spectrum analyzer I flattened the response all the way down to 21hz.