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Old 15th October 2005, 05:54 AM   #41
mike.e is offline mike.e  New Zealand
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I would try to go ribbon rather than DOME aswell. The acoustics text ive read, all refer to domes as being inferior directivity wise.

You dont want large changes in directivity off axis,which lots of systems do.

Or just bite the $$$ bullet and get a compression driver and nice HF horn.
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Old 16th October 2005, 04:41 PM   #42
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Default Texts on the web

I've found a link to the Geddes texts on the web. There are 4 papers grouped together near the bottom of the list.

http://baseportal.de/cgi-bin/basepor...io/download_ex

I picked up one of the MCM "waveguides". I think it could provide sonic improvements over a flat baffle, BUT:

The throat begins at an angle outside of the axis of the driver. From the standpoint of the Geddes texts, the radiation pattern is flawed from the beginning. The walls of the throat of a waveguide should begin parallel to one another. How much of a comprimise this is, I don't know.

The MCM item must be altered in order to mate it with a driver that does not have a threaded fitting.
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Old 18th October 2005, 05:02 AM   #43
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OK!

first,I don't have money for a Raven or so!
My budget is restricted to something like Seas 27TBFCG and
L22RNXP!(I gave you an example just to see my budget, because in my country these drivers are much more expensive than USA)

Second, I don't believe that a big professional woofer/midrange would be a good ideea!
I need something more domestic!

And for the bass part, let's say that i want something closer to
F3@37Hz or better!
At least that's what I got when I simulated the L22RNXP in a 40L
BR @25Hz enclosure!
Is it good or bad?
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Old 18th October 2005, 06:45 AM   #44
Hennie is offline Hennie  South Africa
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The crossover will not be easy, success will depend on your filter design skills. You will have to accomodate the peak in the bass driver's response in your crossover design. If you do not have the software to do so, look at an active design with chip amps.

If you go passive have a look at the crossover filter topologies employed by Jon Marsh at htguide.com, maybe join and direct further questions at him. But the crossover may turn out to be complex and expensive, so keep this in mind. A further indication that it is worth looking at an active system.

I think the bass driver will start exhibiting some stored energy problems at around 1Khz or so, but I haven't seen any tests. So keep the crossover low and maximise the size of the waveguide to aid output on the lower end of the tweeter. At least 220 cm I would think. With its low fs the tweeter you have selected is the best you can do within your cost constraints. There are other options with better bottom end like the Morel Supreme or the Accuton C23 but they cost much more for only a few db's extra output.

With a 220cm shallow waveguide you will only get a few dB augmentation at around 1.3Khz, so I would be hesitant to go lower than that. The MCM 54-580 will not give enough augmentation for this application, go bigger. This implies making your own.

The bass alignment you did looks about right for your room.
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Old 18th October 2005, 06:19 PM   #45
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Even relatively shallow waveguides can make a significant difference in exactly the region where the music has more energy content (from the perspective of a tweeter anyways). Here a measurement of a monacor DT-300 with waveguide nicked from audiodiskussion.de:

Click the image to open in full size.

I have had good success by crossing with a 4th order Butterworth filter with deep notch filters on the DCX centered around problem frequencies of a woofer (compounding some high-Q notch filters even with significant improvements in CSD measurements) slightly above the crossover frequency and some EQ (generally boost) to make the transition area as well behaved as possible (also to relieve as much strain on the tweeter as possible as having it flat to as close as possible to the crossover frequency is counterproductive, in my case allowing me to do away with dynamic EQ above a loud 15" on a PA setup).
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Old 1st November 2005, 05:10 AM   #46
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OK, guys I'm back!

I had some problems!

As I stated before I want something cheaper drivers!


Something in the samepricerange with Seas 27TBFCG and
L22RNXP!
I don't want to spend more!

And for the bass part, let's say that i want something closer to
F3@37Hz or better!
At least that's what I got when I simulated the L22RNXP in a 40L
BR @25Hz enclosure!
Is it good or bad?
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Old 18th November 2005, 03:27 PM   #47
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Come on guys, please help me!

I really need to choose the drivers first and then to go simulating!
I don't have enough money to buy Volt speakers(by the way they are pro speakers, not audiophile ones!), or Raven tweeters (which cost up to 1700$).

I want normal(home/audiophile) speakers like Seas. Vifa, Peerless, Scan-Speak, etc.

As I said before for a speaker I have to pay around 40-50% more to have it!(import taxes, transport,tip, etc)

For the pair of woofers and tweeters I want to pay around 300$(including the 40-50%). But I will boost the budget a little bit more if there are major improvements!

I believe that an 8" woofer in a 40-50L enclosure would be best for the job because it reproduces HF better than a 10" one!

Should I expect a F3 close to 30hz and a F10 lower than 20hz, withoutdestroing the transient response?

Also I think that a 1,5Khz Xover point would be more attainable than the old 1,2khz one!

So any other new suggestions for the tweeter and the woofer?

By the way, what software should I use to desgin the crossover, and predict the overall performance?

Thanks!
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