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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 2nd November 2018, 08:50 PM   #1
kipman725 is offline kipman725  United Kingdom
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Default 1.4" or 2" throat large constant directivity horns you can actually buy!

It's probably easiest if I start this off by explaining what I am aiming for. The speaker I'm designing is going to cover the range 80 - 18 kHz and ideally have a directivity of 90x40 (HxV). At the low end of the range I'm am willing to accept the speaker becoming a mono pole but I would like the directivity to extend as low as possible in frequency, however I would also like broad horizontal directivty even at low frequency. The speaker also needs to be able to output 125dB/1M peak AES SPL. The speaker is to be used at home where I will be listening 17 degrees off axis vertically (hence a speaker with nominal 50 degree directivity would be preferred over 40 degree) due to positioning constraints and also as a PA top where it will not have to array. I will be running different crossover settings depending on application, ideally I would like to get down to ~600 Hz if possible.

What I'm having trouble with is the lack of good quality data on horn/waveguide combinations. I'm aware of the following issues:
1. Large diaphragms only having high frequency output by operating beyond the pistonic mode but manufacturer data is very smoothed and as such I can't see if this is well damped or not.
2. Often I read about some wonder wave guide from a few years ago but the manufacturer doesn't exist anymore or has moved out of the market. Or the manufacturer dosen't sell to the public. (E.G the K402 waveguide looked very interesting).
3. The expected exit angle isn't listed for the waveguides and most manufacturers are not giving the compresion driver exit angle so matching a waveguide with a driver seems to involve expensive trial and error.
4. Many waveguides are not constant directivity at all and yet are listed as such by the manufacturer! (I.E I can see from the shape that its exponential)
5. The high frequency dispersion of a waveguide can be limited by the dispersion of the compression driver but no data is supplied on this.
6. Vast differences in price between various options with no clear data on why.

So taking on this difficult landscape I have come up with a few combinations and I wonder what you think of them and if you know of any more information I have missed:
1. P-AUDIO PH-4525 This is the largest P-Audio wave guide and is only £25 and has a mouth width of 425 mm with a throat of 2". I have read that a lot of P-Audio products are clones of JBL, if so does anyone know what model this would be? In terms of driver pairings they measure it with this P-Audio BM-D750 (£85) or there is the huge P-Audio BM-D950 (not sure where to buy) a 4" diaphragm seems to be pushing it in terms of possible breakup problems! P-Audio claim it can go lower than the D750 though...

There are some measurements of the D750 combo here seems that at least one person likes it.

2. The same horn but assuming the dispersion of these large diaphragm drivers is poor using the very expensive (for me) BMS 4592 ND (£430). This is a coaxial and carry's a number of risks that make me uncomfortable. Firstly I'm not sure if it will work well with this horn and secondly if using it I would like to have a passive crossover between the 1" and 2" driver which will add a lot of development time. Ideally as this driver can go super low (300Hz) I would like to mate it with a much larger horn but I don't know where to get one for sane cost. I would be willing to try and extend the mouth of an existing flare but building the throat area I'm not very confident I could do well. This is also more money than I would like to spend considering I will also need to add woofers, electronics, box etc.

3. An in-between driver not as expensive as the BMS but with better data than the P-Audio such as the HF200. This seems to be quite well damped as the frequency response isn't as smoothed (£187).

3. 1.4" exit drivers. As my SPL requirements aren't crazy this may actually make a lot of sense, as the horns will be smaller and dispersion better? and result in lower cost. For this the RCF HF950 looked quite attractive (especially as it has 50 degree vertical dispersion and claims 'perfect' constant directivity) (£55). For a matching driver the RCF ND840 ooked quite interesting and as its from the same manufacturer it may match up with the horn well? (£145)

*Yes I am aware that I should build a synergy horn type thing and I will but this will take a while and in the meantime I need better speakers...
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Old 2nd November 2018, 09:08 PM   #2
Jack Arnott is offline Jack Arnott  United States
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Re: solution 2, concern secondly, (passive crossover for the BMS coaxial compression driver. BMS makes a passive crossover specifically for that purpose.
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Old 2nd November 2018, 09:11 PM   #3
Jack Arnott is offline Jack Arnott  United States
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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.
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Old 2nd November 2018, 09:24 PM   #4
scholl is offline scholl  United States
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Take a look at Faital Pro and Eighteen sound. You might have to toe the bov in a bit.
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Old 2nd November 2018, 09:31 PM   #5
Jack Arnott is offline Jack Arnott  United States
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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.
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Old 2nd November 2018, 09:34 PM   #6
Jack Arnott is offline Jack Arnott  United States
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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.
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Old 2nd November 2018, 10:55 PM   #7
LineSource is offline LineSource  United States
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Your speaker goals match the Danley Synergy klones in this forum. Several wood Synergy builds have been documented.

The Klipsch K402 waveguide would be ideal if you can find one on eBay UK.
Have you tried to buy an SEOS24 or SEOS30 from Poland?

I have been impressed with the BMS 4594Nd coaxial CD on a SEOS24 waveguide, and this combination would simplify the required wood work.
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Old 3rd November 2018, 12:03 AM   #8
Cask05 is offline Cask05  United States
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See Heritage Klipsch - that big "theater" sound and "HOM" ? - Technical/Modifications - The Klipsch Audio Community

If you're wanting a cheap approximation of the K-510 to try out (with suitable EQ applied to tame the 1-4 kHz hump in response, and a little HF boosting ramp filter on the 5-16+ kHz...just like the K-510 horn needs), here is a very good horn that's also very inexpensive and that tests very well in terms of its polars relative to the K-510: 

2" Throat Horn Bolt-On 18"x10"For Assorted Bolt On 2"Exit Drivers 90degx 40deg(398) | eBay

First horizontal:
Click the image to open in full size.

Then vertical:
Click the image to open in full size.

The polars of the BMS 4592ND will be the even better up high (10-20 kHz) due to the absence of diaphragm breakup that the Klipsch K-69-A exhibits in the plots linked just above.

The K-402 used with a BMS 4592ND is superb. Here is an on-axis SPL/phase plot of the MEH version of that horn with dual 15" Crites cast frame woofers. Pay particular attention to the difference between the minimum phase trace and the total phase trace. (A hint: it's the best I've seen in a full-range horn.)

Click the image to open in full size.

Chris
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Old 3rd November 2018, 01:10 AM   #9
kipman725 is offline kipman725  United Kingdom
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Quote:
Originally Posted by Jack Arnott View Post
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?

Quote:
Originally Posted by scholl View Post
Take a look at Faital Pro and Eighteen sound. You might have to toe the bov in a bit.
Looking at the 18sound horns I don't see anything that goes very low? Constant Directivity High Frequency Horns

Quote:
Originally Posted by Jack Arnott View Post
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?

Quote:
Originally Posted by Jack Arnott View Post
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.
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Old 3rd November 2018, 04:27 AM   #10
AllenB is offline AllenB  Australia
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Matching the driver to the throat is going to ensure the wavefront remains intact rather than diverting to higher order modes. The size of the throat in comparison to the wavelengths can be considered. Also there are some waveguides where the shape asks for compensation or correction, especially when not round like the driver. Fixing throat issues can be simple in some cases and unreasonable in others. Fixing the angle can sometimes be done by extending the throat back with a radius.
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