800hz - 16khz 1" CD under 150 is it possible?

[Jerry Parker]

My current Main speaker setup is a pair of Eminence Delta 12LFA woofers, running in a 2.5 way with the lower woofer being crossed over at ~350hz with an inductor. The upper woofer is crossed over (right now with a DCX2496) at 1.2khz to an Eminence PSD2002 CD with Eminence H290 horn. The sound is good, but not great. The main problem I believe lies with the compression driver.

My plan is to get rid of the existing horn and CD, and replace them with a CD that can play from 800hz to ~16khz. I've looked at the entry level Radian model and it looks good at only 125 USD, but I also need to buy a new horn as well. This is the only reasonably priced model I could find: http://www.partsexpress.com/pe/showd...number=270-304 but I have no idea how that would sound, and for 14 dollars I wouldnt expect much.

Any suggestions?

[mordikai]

Why do you expect this horn to sound better? There is a theoretical 200 hz lower cutoff, but thats about it. You would probably be better off keeping your comp. driver and getting a better horn or wave guide.

[tinitus]

You know, harsh sound can easily be caused by XO faults, even with the best drivers
Morekai may have a good point though

[Wayne Parham]

You might check out the B&C DE250. Come over to my place some time and you can listen to it.

This is the response curve of a four Pi with JBL 2226 and DE250 on the H290 horn. I measured outdoors using a swept sine and no smoothing was applied.

[sreten]

Hi,

Your crossing over a driver at 1.2Khz that has a +6dB peak and roll-off
at 2KHz ? This needs a elliptical filter, a low pass section followed by a
bandstop ~ Q=2 at 2kHz.

The above might be the source of your problem.

I'll also note the exponential horn you show is not CD.

/sreten.

[sreten]

Originally posted by Wayne Parham

Hi,

That graph gets my far too good to be true of the year award.

/sreten.

[ttan98]

Originally posted by Jerry Parker
My current Main speaker setup is a pair of Eminence Delta 12LFA woofers, running in a 2.5 way with the lower woofer being crossed over at ~350hz with an inductor. The upper woofer is crossed over (right now with a DCX2496) at 1.2khz to an Eminence PSD2002 CD with Eminence H290 horn. The sound is good, but not great. The main problem I believe lies with the compression driver.

Hi,

I am thinking of purchasing Eminence Delta 12LFA woofers working in similar configuration as you, how do you find this woofer,

what is the low freq can you get?
what size of cabinet do you use?
The lower midrange below 1.2Khz?

[Wayne Parham]

Originally posted by sreten



That graph gets my far too good to be true of the year award.

I'm very proud of it, thanks. I've been making the four Pi speaker in this DI matched two-way configuration for over a decade. Plans are available free to the DIY community, and I encourage you to build one and measure it yourself.

This latest version has the B&C DE250 compression driver, which is very smooth as you can see and provides extension to about 18kHz. It's a very nice sounding driver. The Eminence PSD2002 is pretty good too, but isn't as smooth and rolls off at 16kHz.

The four Pi crossover has top-octave compensation to provide conjugate EQ for the power response of the driver. It is slightly different between the two, the version used with the DE250 has 2dB more attenuation under 6kHz. Both versions of the crossover have augmentation of 6dB/octave above 6kHz. Spice models are available online, as that is what was used to develop the crossover.

The three Pi model uses an Eminence Delta 12LF, just like what Jerry uses. In fact, I think he got his kits from me. Similar crossover, similar design style (DI matched two-way) and same horn and compression drivers are used. That's why I suggested it here - Jerry can swap out the PSD2002 with the DE250, make a couple crossover changes and upgrade his syetm to get response as shown above.

I use both the Smith & Larson WTPro measurement system and LMS. I like using WTPro for crossover design and LMS for high-power SPL tests of finished products.

The nice thing for me is that WTPro uses my existing Spice models and makes a DSP filter that exactly emulates the crossover circuit. That way I can measure the speaker with a crossover modeled in Spice, and change the values of any components simply by changing the values in the Spice model.

LMS is great for SPL testing outdoors using full power sweeps. It gives a calibrated SPL figure that you can depend on. It is also nice for doing polar charts, because you can make several sweeps at various angles and LMS will assemble a polar chart with them at the click of a button.

[jamikl]

What is meant by the "DI matched configuration"? I don't know whether I am having a dense moment or not but at this point I don"t understand.
jamikl

[sreten]

Hi,

Presumably it means "directivity index" matched at the c/o point.

/sreten.