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Multi-Way Conventional loudspeakers with crossovers

250Hz-2kHz horn for B&C 8PE21
250Hz-2kHz horn for B&C 8PE21
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Old 15th March 2019, 11:28 AM   #1
apolinary is offline apolinary  Poland
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Default 250Hz-2kHz horn for B&C 8PE21

Hi,
I,d like to build a horn for 8PE21 to be put between B&C DE250 attached to FaitalPro LTH102 horn and 15'' woofer in OB (FaitalPro 15FH510).
I hoped I would be able to find tons of projects or plans for such a "horn friendly" driver but I couldn't find anything for the given application. Hence the thread.
The idea is to cover 250-2000Hz band without any (or very little) EQ. Something Avantgarde midrange horns like. I thought I would modify the project from speakerplans.com website:

Speakerplans.com
Instead of two 10'' drivers I'll use one 8PE21 and downsize the horn proportionately: instead 15x21cm thorat (for one 10'' driver) I'll have 12x16,8cm (proportionate reagarding Sd of the drivers). And by the same method the mouth width would be 48cm instead of 60.
The big question is:
Is it totally insane?


I'd appreciate any valueble comments, ideas etc. I tried to use Hornresp but propably too stupid for that. I didn't buy the 8PE21 yet so they are not a must. What matters is the frequency scope and, if possible, Xover-less design.


Thanks.
Chris
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Old 15th March 2019, 11:32 AM   #2
AllenB is offline AllenB  Australia
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I assume you want a LeCleach horn. Try between 126-142Hz cutoff.
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Old 15th March 2019, 11:37 AM   #3
kipman725 is online now kipman725  United Kingdom
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this almost fulfils your requirement:
Sonitus MR8XT Mid-Range Horn << blog.bluearan.co.uk
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Old 15th March 2019, 11:42 AM   #4
apolinary is offline apolinary  Poland
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Hi Allen,
Would it be possible to go as low as 130Hz and still be able to maintain good response at around 2k Hz? I read that having 130Hz would limit the upper end to more less 1k Hz. Not mentioning the bigger mouth. I thing 250Hz would be good, I really like the OB bass up to that fq.
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Old 15th March 2019, 11:47 AM   #5
apolinary is offline apolinary  Poland
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Thanks Kipman,
I read about the Sonitus, a little bit too shy on the lower end... I was tempted seriously but decided I need at least 300Hz, 250 Hz ideally.
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Old 15th March 2019, 11:59 AM   #6
AllenB is offline AllenB  Australia
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To be honest, there is no free lunch when trying to extend a tractrix or LeCleach horn lower. It just doesn't work.

What you should consider is that group delay is affected by the horn at low frequencies. It is possible to change this by setting the rear volume and type of rear enclosure, but it is also effective to choose a conical horn and avoid horn loading.

Of course that would be a bold project indeed. Don't be discouraged.
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Old 15th March 2019, 12:04 PM   #7
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by apolinary View Post
good response at around 2k Hz
1. Make sure the wavefront is intact. Use a phase plug if necessary, although some would argue that 2kHz is OK without one.

2. Consider the narrowing directivity. The room walls are not going to be helpful here. Sure, it is good that higher frequencies don't reach the walls, but it is bad that the lows will be hemmed in.
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Old 15th March 2019, 04:00 PM   #8
apolinary is offline apolinary  Poland
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I'm open to ideas since my knowledge about horns is quite limited. I read a lot though, but no experience in designing/building.
I would love the upper around 2000 Hz but that's not a fixed value. I just am aware that midrange horn in one of Avantgarde speakers covers more less 200-2000Hz and that's why I assumed it would be possible to build similar one.
The project from speakerplans I mentioned above has 180-1500Hz coverage so my thought was that smaller/tighter horn would play a little bit higher on the both ends. But, of course, I may be wrong.
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Old 15th March 2019, 05:34 PM   #9
arcgotic is offline arcgotic  Romania
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Hello!
Just today I looked over the data of multiple midwoofers to find one to work 130-1100hz.

I also want something that you mentioned, OB (or sealed, I have 18FH500 now), mid horn, and the DE250 in horn. What I can tell you now, is that you want to be able to cross the DE250 lower than 2k, say at 1k. For this you need a bigger horn. I tried some horns and now have the RCF H100, and recently bought 2 Eminence H290. I will try them soon, no time yet.
The 'scene', voice intelligibility and all instruments sound better when DE250 is crossed lower, at 1kHz or 1.1kHz. Going lower is not ok for RCF H100, maybe you can find a bigger horn to try. Dr. Geddes studied and found that the brain needs all >1k content from 1 source, if I am not mistaken.

So my advice is to first see how you like the DE250 crossed lower and then maybe adjust the midhorn specs.

I had a tractrix loaded with Visaton FRS8M, 25cm throat area, 2400cm mouth, 50cm deep if I remember OK, here is the response. Click the image to open in full size. The sound was very good, at that time I crossed it at 2400Hz to some dome tweeters.

220tx-frs8m-horn-only-spl — imgbb.com

Good luck!
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Old 15th March 2019, 05:42 PM   #10
arcgotic is offline arcgotic  Romania
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Just looked over your horn specs, FaitalPro LTH102, I see they recommend 1kHz crossover. Start from 850Hz and go up in 50Hz increments, you will hear when it sounds OK.
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