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Cornscala woofer & x-over question


feket663

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I'd like build a Cornscala with APT150 supertweeter and Atlas PD5 VH mid driver on the Altec 511b midhorn for my home built SE 2a3 monoblocks (I don't like loud music...:), enough about 100 dB/1W speaker ). The problem is the woofer. I find this speaker: Eminence Kappa-15LFA. 8 ohm. Parameters: Le: 1.27 mH *Impedance: 8 ohms *Re: 5.4 ohms *Frequency range: 38-2,700 Hz *Magnet weight: 95 oz. *Fs: 39 Hz *SPL: 99 dB 1W/1m *Vas: 5.6 cu. ft. *Qms: 6.08 *Qes: 0.41 *Qts: 0.38 *Xmax: 5.5 mm

The question: can I use this woofer and which modifications necessary in the x-over? (i know the original x-over made for 4 ohm speakers.)

Unfortunately, the original or Crites's woofer shipping cost is very expensive from USA , however, this woofer can be obtained cheaply in Europe.

Plese help me!

Istvan from Hungary.

sorry for my bad English.

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Guest David H

This woofer would be a better choice, its 4 ohm and hopefully available in your area.

Eminence Kappa-15C 15" Driver 4 Ohm

Welcome to the forums.

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kg4guy: Thanks for help! GotHover: I examined the Eminence Kappa15C driver, but I read the tech. datas and the freq. response just go only 63 Hz in large vented box built by factory recommendations. I'd like good, low bass extension. This discipline better the Kappa 15 LFA. Thanks for welcome!!!

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Guest David H

Ok then I suggest you take a look at the Kappa Pro-15, because the 15LFA is not going to have enough SPL for your application.

I also urge you to look at the manufacturers graphs on these drivers from 20-600hz rather than the printed specs.

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Guest David H

The woofers I reccomend are the original K-33 available from the Klipsch parts dept, or the woofers from Bob Crites. If you are looking for a touch more bass, go with the Crites cast frame woofer. The only reason I suggested the Eminence is because of the exceedingly high international shipping cost. If you are in the U.S. I would stick with the tried and true.

Another question: Do you know other midrange horns that would fit?

Yes, I have got a few ideas on horns.
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Guest David H

I guess I'll go for the Kappa Pro 15A. This woofer looks really good on the sheet as I would expect from a PRO series Big Smile

Is the original woofer 8Ohm or 4Ohm? Can I use 4 and 8Ohm with the same crossover?

The original woofer is a 4 ohm. The factory type B crossover uses a 2.5mH inductor on the woofer, and crosses at 600hz.

The Kappa pro-15 is 8 ohm. the correct value for 600hz as dictated by a crossover calc is roughly 2.5mH. The crossover calc would lead me to believe the Cornwall crossover is better suited for an 8 ohm driver than the original 4 ohm.

I really dont have a good answer to you question. Hopefull a crossover expert will step in and clarify.

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Guest David H

I don't get it. It sees that it makes no difference. Is this right?

Inductor changes will have an effect on frequency, I just don't have the answer you are looking for. Johnny 5 is using the Pro 15 in his Cornscala's and uses a 2.2mH and sounds excellent.

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Guest David H

Maybe I need to reiterate.

The woofers I reccomend are the original K-33 available from the Klipsch parts dept, or the woofers from Bob Crites. If you are looking for a touch more bass, go with the Crites cast frame woofer. The only reason I suggested the Eminence is because of the exceedingly high international shipping cost. If you are in the U.S. I would stick with the tried and true.

I am not endorsing the use of the Kappa Pro or 15C, I have however seen both of them used successfully.

If you choose to use woofers other than the O/E or suitable replacement, you may have to modify your crossovers due to impedence changes. I have not run any tests on the woofers disgussed, therefore I do not know what crossover changes need to be made.

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Yes, I know what you said. I saw several CW3 and LaScalas on this Forum using the different Kappa woofers, that's why I thought it should not be a big problem.

You already told me that there would be maybe an change on the crossover, I just thougt someone of those users I saw maybe know what to change. Can't be that big thing. I mean...the K-33 and the Crites woofer are both from Eminence afaik.

When you all think it will not work, then I have to handle the high shipping costs to Europe. I just want to be sure that I have to.

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  • 1 month later...

I'd like build a Cornscala with APT150 supertweeter and Atlas PD5 VH mid driver on the Altec 511b midhorn for my home built SE 2a3 monoblocks (I don't like loud music...:), enough about 100 dB/1W speaker ). The problem is the woofer. I find this speaker: Eminence Kappa-15LFA. 8 ohm. Parameters: Le: 1.27 mH *Impedance: 8 ohms *Re: 5.4 ohms *Frequency range: 38-2,700 Hz *Magnet weight: 95 oz. *Fs: 39 Hz *SPL: 99 dB 1W/1m *Vas: 5.6 cu. ft. *Qms: 6.08 *Qes: 0.41 *Qts: 0.38 *Xmax: 5.5 mm
The question: can I use this woofer and which modifications necessary in the x-over? (i know the original x-over made for 4 ohm speakers.)
Unfortunately, the original or Crites's woofer shipping cost is very expensive from USA , however, this woofer can be obtained cheaply in Europe.

Plese help me!
Istvan from Hungary.
sorry for my bad English.

There is a new version 15LF-2. It will be an EXCELLENT woofer. Since you are building your own speaker, you will need a crossover designed just for it, don't automatically use the Klipsch network. For your small tube amps an 8 ohm woofer is better. However, don't stop with just one, use 2 in each cabinet. You will get 102 to 104 dB @ 1 watt @ 1 meter! Since you have 511Bs, I highly recommend picking up a pair of Altec 902-8B drivers and building it as a 2-way system. The 902 is 106+ dB on a 511B, with a hump below 2k Hz. The crossover below trims off the hump and crosses at 1k.

Peav-tecFinalschematic.jpg

Here is the Computer predicted response and I would say it sounds like this. I don't think you will think is sounds "soft" or want a tweeter. I designed the crossover using Xover Pro from Parts Express. You might want to play with the design a little to lower the crossover point and remove the peak the 15LF-2 has in the midrange.

Peav-tec%3DFinal.jpg

Here is the response of a 902-8B in a 511B, as tested and posted by Shawn Fogg on this Forum. Note the hump. If you remove it with the crossover the very high frequencies are right up there where you want them.

post-2142-13819499773048_thumb.jpg

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