What should I use to build my own crossover?

[punkrokr1701]

Ok, here's the deal.

I'm just now starting to understand to concepts of speaker design technology but I still can't comprehend the design and engineering that goes into building crossover so I need some input on how to build my own crossover.

I need a 3-way for these speakers

woofer 50- 4000 Hz , 8 ohm
mid range 80 - 9000Hz, 8 ohm
tweeter 2kHz - 25 kHz 4-8 ohm

I haven't finished the cabinet yet and I was also wondering what I should tune each speaker to because I'm gonna make a tuned cabinet for each speaker.

Anyway, how do I make my own crossover and what parts should I use?

Also this is a high power application, I'm talking 1200 watts rms.
Please don't ridicule me for thesis ratings ok?
I just want to know how to build a 3 way crossover and what to use.
That's all.
Thanx.

[lndm]

Originally posted by punkrokr1701
I haven't finished the cabinet yet and I was also wondering what I should tune each speaker to because I'm gonna make a tuned cabinet for each speaker...

...I just want to know how to build a 3 way crossover and what to use.

Hi punkrokr1701,
That really is a big question.

Calculating a reasonable size for your cabinets, and rigging up a crossover that will prevent the drivers from self destructing could be your first port of call.

What info do you have on the drivers? Thiele/Small parameters, impedance plots, response plots?

[xplod1236]

For such high power ratings, I suggest that you tri-amp and build active crossovers. Here is a program which will give you a schematic and part values if you decide to go active. Do you have the XO frequencies picked out already? And yes, we need info about the drivers.

[punkrokr1701]

I'm only 14 and I have no idea how too use that wizard that you gave me. So if you know of any kind of crossover 101 or crash course it would help out ALOT.

Anyway, here's all the information I have on the speakers:

12 inch woofer:
*Power handling: 300 watts RMS/600 watts max *VCdia: 3" *Le: 1.33 mH *Nominal impedance: 8 ohms *Re: 6.0 ohms *Frequency response: 50-4,000 Hz *Magnet weight: 71 oz. *Fs: 42 Hz *SPL: 96 dB 1W/1m *Vas: 3.81 cu. ft. *Qms: 16.33 *Qes: .32 *Qts: .31 *Xmax: 3.5 mm *Dimensions: Overall Diameter: 12-1/8", Cutout Diameter: 11", Mounting Depth: 5-1/8".

6 inch mid bass:

*Power handling: 100 watts RMS/200 watts max *VCdia: 1.25" *Le: 0.57 mH *Nominal impedance: 8 ohms *Re: 5.9 ohms *Frequency response: 80-9,000 Hz *Magnet weight: 19.8 oz. *Fs: 76 Hz *SPL: 91 dB 1W/1m *Vas: 0.28 cu. ft. *Qms: 6.7 *Qes: 0.95 *Qts: 0.83 *Xmax: 2.3 mm *Dimensions: A: 6.54", B: 5.63", C: 2.9".

tweeter:
3 ¼" ALUMINUM BULLET HORN WITH 1" SUPER TWEETER 40 OZ MAGNET STRUCTURE 250/500 WATT PEAK POWER FERRO FLUID ENHANCED FREQUENCY RESPONSE: 2k-25 KHZ SENSITIVITY: 99db IMPEDANCE: 4-8 OHMS

And yes if you do thae math that adds up to 2 woofers, 2 mid bass and 3 tweeters. I've already built a smaller version of these cabinet but they only handled 400 watts rms so it wasn't hard for me to find a crossover. I know what I'm doing with these cabinets.

[lndm]

Hmmm. Just to throw some thoughts up and see where they land.

The 12" looks like a car speaker. These are often designed to rolloff at a higher frequency and use a small box.

Your 12" driver might work in a 1 cu ft box. It would begin to rolloff at about 90Hz. Maybe a vented box would be better, in that you might get a lower cutoff frequency. Your choice of box will have an effect on power handling.

Anyhow, the 12" is more sensitive than the mid. This means it will play louder. This difference is 5dB. Also, there is a phenomenon known as the baffle step. At the higher frequencies that the mid would handle, the sound will play louder from in front of the speaker, as the sound will concentrate in the forward direction. If you can make your crossover within this region of the baffle step, and with a little luck, the two may balance to some degree.

You may be talking about 800Hz give or take an octave or so. Is your woofer free of peaks in its response to beyond this region?

The volume of your mid enclosure is less critical. Given its parameters, you could put it in a box of perhaps a third of a cu ft, and keep the crossover above 400Hz if possible.

You should be concerned about keeping the crossover away from the mid's resonance frequency (fs) for sound quality and power handling, but on the other hand, letting the woofer handle the higher frequencies mightn't be as good. Hard to say with the available info.

Your tweeters are even more sensitive. Can I suggest you research the 'L-pad'.

For your upper crossover, the tweeter's lowest frequency of 2kHz and the mid's upper of 9kHz suggest a crossover of 4-5kHz. However, there is no indication of the tweeters fs, and no indication of peaks in the mid's response. Ideally, it would be best not to go too high with this crossover frequency, but in the absence of info, it would be best to go high. This would be safer for the tweeters and could improve power handling.

[punkrokr1701]

Here's all the info I have on the drivers and tweeter:

SELENIUM 12PW5-SLF 12" 300W PA DRIVER

http://www.partsexpress.com/pdf/264-370.pdf

SELENIUM 6W4P 6" WOOFER

http://www.partsexpress.com/pdf/264-422s.pdf

3-3/8" BULLET TWEETER

http://www.partsexpress.com/pe/showd...number=270-055

[lndm]

If you wanted to try a vented box, I would concern that the driver would not be supported by the box below the box resonance of 43Hz. This is just a matter of power handling, normally I would be OK with this arrangement. One possibility is a 2.1 cu ft box with a vent of 4" diameter and a length of 4.3", for example.

Your 6" driver has some cone breakup above 2kHz. First thoughts would be to select a crossover frequency below this point, and use a notch filter on the peak in the response.

There is still not enough information on the tweeter, it needs to be measured, or treated with caution. It appears anyway that it would not be suitable for a crossover at 2kHz.

Ironically, it appears as if the 12" would work up to a few kHz. Looking at the response plot, the response seems to roll off reasonably smoothly with a cutoff of 3kHz. Such a large driver will lose a bit in the treble off to the side of the speaker. This has its drawbacks but it may still be good.

You may not be advised to use the tweeter crossed over at 3kHz, but even if you cross it at 4kHz over to the 12" woofer, and there is a small dip in the 3-4kHz region, this may not sound too bad.

If you really want to use the 6" driver, you might want to consider a different tweeter, IMO.

[punkrokr1701]

Ok, I get some of what is said but if anyone could tell me exactly what parts I need to get and where to get them that would be really helpful.

Because I get lost in all the technical terms, etc.

Really, what I'm aking is alot, because that means you whould have to go and find the parts, and then post the pages for me but it would really helpful for me only being a 14 year old speaker builder.

Please reply if you know where and what I need.

[lndm]

Originally posted by punkrokr1701 Really, what I'm aking is alot, because that means you whould have to go and find the parts, and then post the pages for me but it would really helpful for me only being a 14 year old speaker builder.

Please understand, that to build a crossover takes much work, a good one can take years.

I understand that you would like something sooner

Why don't you try connecting the 12" woofers two terminals directly to the amps two terminals.

Get an 8ohm resistor and connect its two ends to the tweeters two terminals. Get a 4ohm resistor and connect one end to one tweeter terminal (+)

Get a 0.56mH inductor and connect one end to the free end of the 4ohm resistor, and the other end to the tweeter terminal (-). Get a 2.2uF capacitor and connect one end to where the 4ohm resistor and the inductor meet. Connect the other end to your amp terminal (+). Connect the tweeter (-) to your (-) amp terminal.

Don't turn it up too far yet. Come back with your progress

http://www.partsexpress.com/webpage....ID=197#15gauge

http://www.partsexpress.com/webpage....&WebPage_ID=69

http://www.partsexpress.com/webpage....WebPage_ID=322

These are some examples of parts that can work. YMMV.

Edit: corrections.

[dangus]

About the midrange efficiency thang: you'd either need to use several of them or horn load to get the efficiency up, because padding the other drivers down would be just silly. A column wouldn't be such a bad idea; it would have useful directional characteristics, but it could make for an awkward cabinet shape. OTOH, you're not looking for perfect imaging in a PA cabinet, so you could maybe have 4 mids in a column on one side of the front and the 12" and tweeter next to them. Putting a horn on the mid would involve some complex fabrication.

Crossover design is an art and a science. But if you were to use textbook values for a 2nd or 3rd order crossover, and put a Zobel on the woofer and midranges, you should get something usable.

Or just buy a readymade crossover by Selenium or Eminence.