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Multi-Way Conventional loudspeakers with crossovers

12" & Horn 2-way build
12" & Horn 2-way build
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Old 8th January 2020, 03:43 PM   #11
puppet is offline puppet  United States
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It's been my understanding that with a 2way horn system matching directivity at xo was fundamentally good practice. A 12" woofer should exhibit 90 degree pattern around 1.4 - 1.5khz. This is a function of cone diameter. A xo at 800hz would introduce mid frequency waistbanding off axis, while putting undo strain on the compression driver. IMO, this would be a poor design move. If you're after flat omnidirectional frequency response, other driver choices are in order. If not, xo that 12" driver around 1.5khz.
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Old 8th January 2020, 05:31 PM   #12
kipman725 is offline kipman725  United Kingdom
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Quote:
Originally Posted by puppet View Post
It's been my understanding that with a 2way horn system matching directivity at xo was fundamentally good practice. A 12" woofer should exhibit 90 degree pattern around 1.4 - 1.5khz. This is a function of cone diameter. A xo at 800hz would introduce mid frequency waistbanding off axis, while putting undo strain on the compression driver. IMO, this would be a poor design move. If you're after flat omnidirectional frequency response, other driver choices are in order. If not, xo that 12" driver around 1.5khz.

I was basing that off the PD124NR measurements here:
Click the image to open in full size.
You can see that the lower 45 degree trace is at -6dB at 800 - 900 Hz. There seems to be considerable deviation from ideal piston directivity for real drivers. This emphasises that the decision should be made from measurements of the real system.

There is also the other criteria to keep acoustic sources within 1/4 wavelength so they constructively superposition throughout all positions which i calculated to result in a crossover <1147Hz.
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Old 8th January 2020, 06:00 PM   #13
Decker is offline Decker  United States
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I use Altec 414-8c 12" woofers in ported boxes with Altec 902 compression drivers on Edgarhorn wooden horns. 1200 hz crossover frequency using a Marchand 24db/oct crossover. I don't have any experience with other compression driver and horn combinations, but this pairing sounds very good IMHO.
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Old 8th January 2020, 06:24 PM   #14
tommus is offline tommus  United States
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Puppet has it right, you want to XO the woofer in it's narrowing directivity zone (where it matches the horn) but before it's breakup. That would be somewhere 1.2 - 1.5 khz depending on the horn. This also allows for a 1" compression driver for better dispersion. I think these new 1.4" super CDs are overkill for the application. B&C DE250 is a good choice. Check out Faital CDs as well, they are very nice. I happen to like the sound of polymer diaphragms.

The Faital 12PR320 would be good here if you wanted to use it in a sealed enclosure and XO to subs at 80-100hz, it has 7+mm of Xmax and a very well-behaved breakup in the upper XO zone.

Below is an interesting article on integrating horns in a domestic setting, especially the part about using the crossover lobing between the woofer and horn to "punctuate" the vertical directivity pattern. In this case the C-to-C distance between woofer and horn is chosen deliberately, not just minimized...

http://www.pispeakers.com/Pi_Speakers_Info.pdf
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Old 8th January 2020, 09:25 PM   #15
Audio Elite is offline Audio Elite  South Africa
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Faital 12PR320, fantastic driver!
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Old 8th January 2020, 09:51 PM   #16
Think is offline Think  Netherlands
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12&quot; &amp; Horn 2-way build
As you use them with a sub, replace the 12" for 2x6" (or 8"); you get better (more detailed) mids and you can cross at 2kHz with good off axis response to a cheaper/ smaller CD that plays higher and more detailed.

IMO sealed sounds best and is most easy to integrate with a sub.

Last edited by Think; 8th January 2020 at 09:58 PM.
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Old 8th January 2020, 10:31 PM   #17
benno25 is offline benno25  Australia
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Quote:
Originally Posted by Think View Post
As you use them with a sub, replace the 12" for 2x6" (or 8"); you get better (more detailed) mids and you can cross at 2kHz with good off axis response to a cheaper/ smaller CD that plays higher and more detailed.

IMO sealed sounds best and is most easy to integrate with a sub.
Thanks guys.

Current speaker I have are 2x 8" and just don't have the kick I'm after.

Hard bounds for this design are as follows.
1. This is to be a 2-way design.
2. Horns are to be RCF HF94's.
3. Woofers are to be 12".
4. Cabinet width is to be around 15-16".

I'm leaning towards the following.

A ported design as most pro audio woofers seem to be more suited to this alignment and have much more output in the 100-200Hz region. My only concern was whether the extra group delay would cause issue when integrating with my subs. FYI my subs are sealed and will be placed throughout the room to give best frequency response in main listening positions.

A 1.4" compression driver as this will give me greater flexibility in the crossover and allow lower frequencies if needed. I'm thinking the HF1440 would be suitable and shouldn't restrict me higher in the frequency range.

I'm also looking at keeping the center to center spacing between woofer and horn as close as possible for better polar response. I can get this down to about 275mm.

Basic design I'm considering for now is shown in the attached picture.
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File Type: jpg Speaker.JPG (45.6 KB, 155 views)
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Old 8th January 2020, 10:38 PM   #18
benno25 is offline benno25  Australia
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Or another option I'd consider is a an MTM sealed design.
Would add to the cost a bit though and may not have any worthwhile benefit?

Cheers
Benno
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Old 8th January 2020, 11:05 PM   #19
kipman725 is offline kipman725  United Kingdom
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MTM will give +6dB more output, double the cost, more narrow vertical directivity. Vertical directivity could be too narrow though if crossover point to the tweeter is high. You could always go 3 way which would lower modulation distortion.

Have you considered coaxial? this looks pretty great if your not set on the horn:
FaitalPRO | Coaxial Loudspeakers | 10HX230

The problem with going over 1/4 wavelength spacing is not on axis, this can be corrected with appropriate phase shift for each driver not matter how far they are apart. The problem is the narrowing of vertical directivity and that there will be points illuminated off the listening axis. The reflected sound field is important and if the speaker puts out loads of energy into the room in off axis beams this is going to have a strong variance with frequency. A lot of effort has been expended by Danley, Genlec, EAW etc. producing novel designs focused on getting driver spacing as low as possible.
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Old 9th January 2020, 01:58 AM   #20
puppet is offline puppet  United States
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Benno25,
Have a look at FaitaPro 12FH500. I think the response around 1.5khz would be ideal.
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