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1.4" or 2" throat large constant directivity horns you can actually buy!
1.4" or 2" throat large constant directivity horns you can actually buy!
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Old 3rd November 2018, 07:03 AM   #11
ScottG is offline ScottG  United States
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Quote:
Originally Posted by kipman725 View Post
..For this the RCF HF950 looked quite attractive (especially as it has 50 degree vertical dispersion and claims 'perfect' constant directivity) (£55).
Test Bench: RCF ND950 Neodymium Compression Driver and HF950 Horn | audioXpress


Driver:

-I'd look to the 18 Sound 1460A or 1480A. Better linearity AND a much easier Impedance to work with..

Here is the 1460A on an 18 Sound XT1464:

The Raptor ... a 10" MTM
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Last edited by ScottG; 3rd November 2018 at 07:05 AM.
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Old 3rd November 2018, 07:28 AM   #12
Jack Arnott is offline Jack Arnott  United States
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Originally Posted by Jack Arnott Click the image to open in full size.
Re: solution 3. The BMS 4594 would be a great solution for that RCF 1.4” horn, since you already expressed interest in a BMS coaxial.

<Apart from the cost there seems to be few downsides to this setup. The driver seems to be basically the same as the 2" throat version? Do you know why this driver can play so much lower than most compression drivers?>


The BMS has a very large diaphragm area. It has "only" a 3.5" voice coil on the midrange, but it is a ring radiator, so it has a lot more of surface area outside the voice coil than inside it, and more surface area than a full dome with a 4" VC.



Quote:
Originally Posted by Jack Arnott Click the image to open in full size.
Regarding issue number 3; I think that in a one off situation, trying to match the exit angle to the horn would be very low on my list of concerns. Very low, like last on the list. If you had two horns that met every criteria, and one matched to driver’s exit angle and one didn’t, then I would go with the one that matched. Otherwise, I would not even ponder it.

<So this has only a minor effect on the systems response? is the effect of the mismatch to alter the on axis response differently to the off axis?>


I would think that if the driver has a different angle than the horn that this will cause diffraction, and differences mostly in the high frequencies. I think this will have less effect than many other considerations. If you were manufacturing your own horn, you would make sure this matched. It irks me when people put too much emphasis on this, and not on other considerations.



Quote:
Originally Posted by Jack Arnott Click the image to open in full size.
Regarding solution 3, SPL has nothing to do with driver exit size. EG, the BMS 1.4” driver will have the same SPL as the BMS 2” with the same characteristics, if the horn matches up the same.

<Doesn't the ratio of the exit to the surface area of the diaphragm define the compression ratio? so a larger diaphragm is usually going to have a larger throat and when running low like I would like to the SPL is going to be excursion limited so drivers that are meeting my requirements are more likely to have a larger throat.>


I should have qualified this by saying that if you have otherwise identical drivers, like the BMS 4592 vs the 4594, the smaller throat will not restrict the frequency response. The two drivers use the same diaphragms, and all the compression is done in the diaphragm exit, which is anular, so when it gets to the throat of the driver, all things are equal. The only difference is that the 1.4" exit driver is truncated, shorter. This means that you get into your horn sooner, and all the loading and dispersion is handled by the horn, and less by the driver. This gives the opportunity for better HF dispersion, and if the throat is loaded the same, and same final size requirements are met, the resulting frequencies that the combination can go down to will be the same.



Other drivers that are compressing into a phase plug might be limited by the horn being a smaller entrance.
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Old 3rd November 2018, 08:56 AM   #13
ScottG is offline ScottG  United States
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ooh, Jack quoting Jack.

-proving that Jack really does know Jack!


(..err, it's late for me - time to get some sleep.)
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Old 3rd November 2018, 10:05 AM   #14
Omholt is offline Omholt  Norway
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1.4&quot; or 2&quot; throat large constant directivity horns you can actually buy!
I'm working with Don Keele and Bjorn Kolbrek on a horn design that have several of the same specifications. A 2-way design that requires a separate bass/subwoofer solution. May also get a horn subwoofer designed with it.

- 80x50 coverage angle
- Frequency range 90 Hz-18KHz or higher
- Crossover at 600 Hz or lower if the driver permits it
- Very uniform directivity low in frequency
- Exit angle of 1.4" (Radian 951BePB driver) but could also be made for other drivers including those with an 1.5" exit
- Non resonant enclosure

Downside is the size the horn requires for constant directivty low in frequency and it's not cheap to build either. I have a Klipsch K-402 horn which I will use for comparison to the top horn. The top horn needs to be better than Klipsch for it to be worth it.

Already have measured and tested the midbass horn. While we'll may be making some adjustments to it, it does work tremendously well today. The horizontal directivty doesn't change much before you get to 100-150 Hz. Picture of it below with the Klipsch K-402 horn on top.
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File Type: jpg Midbass horn 002 (Large).JPG (255.3 KB, 469 views)

Last edited by Omholt; 3rd November 2018 at 10:29 AM.
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Old 3rd November 2018, 12:13 PM   #15
chris661 is offline chris661  United Kingdom
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The RCF HF94 gets a thumbs-up from me. I use it in my main PA system, and it does the job well. The HF950 appears to have a slight "pinch" before the final expansion, which isn't great for HOMs. It does load to a lower frequency, though.

I also use the 18Sound ND1460 (not -A. I use the titanium version - better for PA use), and that gets another thumbs-up. Titanium diaphragms are incredibly tolerant to abuse - you'll hear the diaphragm hit the phase plug in response to LF and little (if any) damage will occur. Aluminium diaphragms aren't so tolerant.

The thing to remember here is that larger exit diameters will beam at a lower frequency. A 1" exit driver will have reasonably good off-axis response past 10kHz, while a 2" exit driver will not. A 1.4" exit diameter is a decent compromise for a lot of applications.

Rod Elliott has a bit here: PA Systems
About compression driver exit diameters vs output vs LF cutoff.

The BMS coaxial compression drivers are really nice, but still constrained by the off-axis response of the exit diameter. ie, they might well get past 20kHz, but it could still be a laserbeam up there. Horns will constrain wavelengths that are trying to be omnidirectional, but when the compression driver itself is beaming, the horn becomes irrelevant.

My main PA system* will do what you're after with a bit of headroom, and sound good doing it. I wouldn't want to be in any domestic-sized space while it's run up to full power, though. Hopefully you're not planning on doing that.

*HF - 18Sound ND1460 on RCF HF94 horns
MF - 2x Faital Pro 10FH520
LF - Up to 4x Faital Pro 15HP1060
^ per side. You'd probably manage your SPL goals with 2x 15"s per side.

It'd be around 100 miles round-trip for you, but I'd be happy to demo that setup.
I've crossed over as low as 750Hz for PA use, which gives a really smooth off-axis response that matches to the 10"s well, but I usually run at about 1kHz out of concern for the HF driver's long-term health. No point in working them harder than necessary if the next band down can cover that range easily.

I also have a pair of 6.5" 2-way boxes that have 1" exit drivers. They'd probably manage 125dB peaks between them, but it'd be a couple of cycles "burst", while the 2x10"s can do >125dB sine waves.
If it's of interest, I wrote an article about SPL ratings in the PA world. It ain't pretty.
Spec Wars: Looking Inside Loudspeaker SPL Specifications - ProSoundWeb

Chris
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Old 3rd November 2018, 02:25 PM   #16
Soldermizer is offline Soldermizer  United States
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Thank you for posting the URL (Grimshaw). I see an article on "Home HiFi and Measurements", so something even for the home hobbyist. I don't "do" PA, but I am among the converts to using "PA" systems in the home. In my case, I got a trashed pair of Yorkville Unity U15 at a good price. Good for me, since my construction skills are limited.
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Old 3rd November 2018, 03:45 PM   #17
Jack Arnott is offline Jack Arnott  United States
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Originally Posted by ScottG View Post
ooh, Jack quoting Jack.

-proving that Jack really does know Jack!


(..err, it's late for me - time to get some sleep.)
I need to work on my multi quoting skilz. But it is handy to see what the response was to.
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Old 3rd November 2018, 03:52 PM   #18
scholl is offline scholl  United States
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Is your listening room a typical home living room 5 Meters by 5-10 meters? IF so you may not need constant directivity below 700hz where the XT1464 will match well to a 15 and deliver awesome results.


Another used option would be a JBL PD 5322 or another JBL compression driver cone mid combination. That's a hard to beat combo to 300hz.

Otherwise the SEOS 24 with BMS should be studied.
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Old 3rd November 2018, 06:20 PM   #19
RobWells is offline RobWells  United Kingdom
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I've used the P Audio BM D750's with some JBL 2385A horns crossed to a 15" driver at home and they do sound good. Only thing is the top octave doesn't sound as good as my beyma 380's. However the lower xo point gives better midrange compared to running the 15's up to ~1.5kHz.

The JBL's can be picked up on ebay, and P Audio do a copy I think.

edit: Think this is the P Audio copy

Last edited by RobWells; 3rd November 2018 at 06:31 PM.
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Old 3rd November 2018, 07:13 PM   #20
LineSource is offline LineSource  United States
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NOTE: Uses JBL CD standard of 1.5"

JBL 365359 001 Top WaveGuide for 3732 | $130 - $140
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