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Four Pi plans and a question [message #35199]

Sun, 24 February 2002 16:08

dbeardsl
Messages: 127
Registered: May 2009

Master

Wayne,

I'm halfway through your Crossover document. This is very interesting stuff and I understand most of it (whooo hoo! good job!), I was planning to make a 3-way project using a 1st order butterworth. Now I think I'd like to use your Theater series Four Pi plans (if you wouldn't mind emailing them to me).

Question: How does a compression driver sound compared to a high eff cone driver in the 1-6k region, the only place I've heard compression drivers is at shows or concerts where it is way too loud to evaluate sound quality.

Nother question... I've noticed in a lot of Eminence's woofers (specially the LF ones) there is a big dip in the reponse between 30hz and 60hz. Whats up with that?

Also, would there be any advantage to using the Delta 15LF instead of the 15A in them Four Pi's?

Oh, also do you reccomend any parts suppliers for caps and resistors?

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You have mail [message #35200 is a reply to message #35199]

Sun, 24 February 2002 17:02

Wayne Parham
Messages: 18677
Registered: January 2001

Illuminati (33rd Degree)

When comparing a compression horn to a cone driver designed to cover the same range, you will find that the cone driver is incapable of providing the same dynamic range, or probably even anything close. It also can't beat the horn's low distortion. There are some technologies that improve distortion of a direct radiator, like shorting rings, but they can be used in a horn driver too. So the horn beats the direct radiator in terms of dynamic range and distortion. The only thing a direct radiator can offer is greater bandwidth, but that's not necessarily a good thing, since increasing bandwidth necessarily increases intermodulation distortion.

About Eminence woofers and their measurements, I had a discussion with them about consistency (and therfore, the reliability and accuracy) of their measurements. One thing I learned is they are installing the drivers on an infinite baffle for measurement, and that is likely a big contributor to response problems below 100Hz. Not all drivers are well suited for infinite baffle use.

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Questions [message #35204 is a reply to message #35200]

Sun, 24 February 2002 23:29

dbeardsl
Messages: 127
Registered: May 2009

Master

In the Plans, The two calculated values, R3 and C5. I'm guess the power rating should be the same as the others? 40W and 200V?

Also, have any suggestions on horn flares for the PSD2002?

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Answers [message #35212 is a reply to message #35204]

Mon, 25 February 2002 07:17

Wayne Parham
Messages: 18677
Registered: January 2001

Illuminati (33rd Degree)

R3 should be 8 ohm, 100W. C5 should be 20uF, at least 200V. Use the Eminence H290 or the Peavey CH-3 horn. The H290 mounts on a PSD2002 but the CH-3 mounts on a PSD2002(S).

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Sealed Four Pi? [message #35218 is a reply to message #35199]

Mon, 25 February 2002 09:26

dbeardsl
Messages: 127
Registered: May 2009

Master

I've always liked the transient-response in the low end from Sealed boxes (and the lessened distortion below the port tuning freq.), of course they have to be generally much bigger cabinets, just not sure if it would be a worthwhile trade off.

Anybody ever thought of sealing the FourPi's?

I suppose I could just build em with a port and try plugging it up.

I'm worried that I'll build these great speakers then see the woofers flapping when I put in more than 20 Watts.

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Super tweetie bird on Four Pi's [message #35220 is a reply to message #35199]

Mon, 25 February 2002 10:02

dbeardsl
Messages: 127
Registered: May 2009

Master

I'm a young feller and can hear pretty well in the upper region 16-20k
The theater four pi's are listed as 25-18k. How steep is the roll off up there? Anybody ever measured it?
Anybody thought of augmenting a piezo or a eminence APT Supertweet?

Jeez I sure talk a lot for never having heard them...

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The "Pi Alignment" is a ported alignment [message #35221 is a reply to message #35218]

Mon, 25 February 2002 10:08

Wayne Parham
Messages: 18677
Registered: January 2001

Illuminati (33rd Degree)

If you build a speaker that isn't ported, then it isn't a π Speaker. The "Pi Speaker Alignment Theory" document is a paper written that specifies a certain alignment, and it is a ported alignment.

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Re: Thanks Wayne!(nt) [message #35222 is a reply to message #35221]

Mon, 25 February 2002 10:40

dbeardsl
Messages: 127
Registered: May 2009

Master

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Re: Super tweetie bird on Four Pi's [message #35223 is a reply to message #35220]

Mon, 25 February 2002 11:51

Wayne Parham
Messages: 18677
Registered: January 2001

Illuminati (33rd Degree)

You can add a super-tweeter if you want. My biggest problem with it is there's no way to get the super-tweeter close enough to the compression horn to be within 1/4 wavelength. It causes an interference pattern that sounds "phasey" to me.

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Re: Sealed Four Pi? [message #35227 is a reply to message #35218]

Mon, 25 February 2002 15:05

Adam
Messages: 419
Registered: May 2009

Illuminati (1st Degree)

Unless you're using the basic Eminence drivers or a few select other eminence motors, you're asking for trouble.

These are P.A. woofers designed with generally high FS values and lower Q values. Very bad for sealed box operation. The enclosures will be very small, but extremely shallow on the bass and simply won't sound right. A few Eminence woofers (Kappa 18A, Kilomax) would work okay in a sealed box, but they don't have the xmax for high volumes.

Adam

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