Small format cone driver in horn thread

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Frangus,

How do you think these horns would do with FaitalPRO 3FE25s? I have a pair hanging around, and they're crying out to be used :)

EPB of 138 and good sensitivity - I reckon its worth a try. On paper its more suitable than the driver I am using but you would have to make a smooth chamber transition for the 3" driver to the 2" throat to get a smooth response
 
Hi, what are the dimensions of the "30mm length" horn/waveguide?

Hi,
The waveguide is 30mm length with 90° of opening angle and 10mm of 120° of opening angle at the exit... the total length is 40mm.

for other measutrements 30° is half of the opening angle of the round horn, the second number is the length and the third is the mouth entry diameter.
Responses are perhaps affected by the lack of low end loading of the conical shape.

PS : the 350Hz hole is the acoustic short circuit (25cm Mic capsule)
 
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The waveguide is 30mm length with 90° of opening angle and 10mm of 120° of opening angle at the exit... the total length is 40mm.

The SPX-31M spec sheet doesn't show any FR plots, but your results look pretty flat except for the dip between 6-7kHz and the bit of breakup above 10k which just about every 2-3" driver has. It does say the driver sensitivity is 86dB at 1W/m. What drive level were you using for your measurements?

So the total length of the waveguide is 4cm with two conical expansions. What's the diameter of the throat or the mouth?

Edit: a quick sim with some geometrical assumptions shows that without a rear chamber and no baffle you would get a null around 8.7kHz and 17.3kHz. With a larger baffle that would bring these down in frequency and could be causing the dip between 6-7k. Try making a simple sealed chamber for the driver and taking the measurements again. Acoustical power response is attached showing a 1L rear chamber (black) versus no rear chamber (gray).
 

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The SPX-31M spec sheet doesn't show any FR plots, but your results look pretty flat except for the dip between 6-7kHz and the bit of breakup above 10k which just about every 2-3" driver has. It does say the driver sensitivity is 86dB at 1W/m. What drive level were you using for your measurements?

So the total length of the waveguide is 4cm with two conical expansions. What's the diameter of the throat or the mouth?

Edit: a quick sim with some geometrical assumptions shows that without a rear chamber and no baffle you would get a null around 8.7kHz and 17.3kHz. With a larger baffle that would bring these down in frequency and could be causing the dip between 6-7k. Try making a simple sealed chamber for the driver and taking the measurements again. Acoustical power response is attached showing a 1L rear chamber (black) versus no rear chamber (gray).

The entry mouth is 75mm and i don't know exactly what is the SPL (forgot to calibrate my microphone :fight:)

i'm trying to minimise the internal volume occupied by the midrange driver, the open back driver configuration gain is 0.8L

Thanks for your simulation, the WG seems to load the transducer efficiently up to 200Hz... i'm really dubitative with the grey line simulation, is there something to improve in the mathematical model ?
 
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That changes everything if the throat area is 44.18 sq.cm. The other sim was based off of a throat area of 32 sq.cm.

Here are sims with updated data. you can run them yourself if you'd like.

The key things to note are that if the driver is truly open back and the waveguide has no baffle then you'll get cancellation in the lower frequencies and interaction with the front wave at higher frequencies. When the driver is put into a sealed enclosure the back wave no longer cancels and you get your lower frequencies back :)

The acoustic power plot is not frequency response. The falling power response is countered by directivity and beaming, so the frequency response is most likely much flatter above the upper power roll off.

Also note that the sims were done assuming a 2*Pi space. Using them in a room and close to a wall will make it 1*Pi.
 

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EPB of 138 and good sensitivity - I reckon its worth a try. On paper its more suitable than the driver I am using but you would have to make a smooth chamber transition for the 3" driver to the 2" throat to get a smooth response

Thanks for your response!

I'll look into some throat adapter designs and see which one I can mimic, that's also the most appropriate. Now's the time I wish I had a 3D printer :)

Or would it suffice to drill a 2" hole in a piece of wood, and then use a router and a roundover bit to chamfer the edge to 3"?
 
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Thanks for your response!

I'll look into some throat adapter designs and see which one I can mimic, that's also the most appropriate. Now's the time I wish I had a 3D printer :)

Or would it suffice to drill a 2" hole in a piece of wood, and then use a router and a roundover bit to chamfer the edge to 3"?

Yes I think that be the easiest way to do it. You just need a smooth transition, nothing fancy
 
Audiophile footwear

A picture of my latest set up

Same driver but with wool damping over the back aka a sock :) I was hopig to progressively dampen the higher frequencies to gain some clarity and better imaging. It seems to have worked very well

Still havent ordered any better drivers but looking at the 2" fountek or the TB...
 

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A pair of Peerless NE65W-04 and Fountek FR58EX arrived today. Both are very nice looking drivers. You know 2 inch drivers are going to be small but they just feel tiny! Hopefully some free time this weekend will allow for a bit of listening.

The mouth is 16 in (40.64 cm) by 9 5/16 in (23.65 cm), which puts the mouth area at 961.2904 sq.cm. The axial length is 11 7/16 in (29.0513cm).

Endless searching for horns/waveguides recently led me to some spec sheets for JBL/Selenium HM4750-SLF and HL4750-SLF horns. I have to say that it seems like the eBay horns were designed/modeled/copied around a combination of the HM and HL horns. The mouth dimensions are almost the same and the look is very similar but the eBay horn axial length is in between the HM and HF. The HM in particular has a coverage of 90x40 but is only 8.27 inches long. The HL has a coverage of 40x20 and is 13.86 inches long.

Edit: just noticed that the axial length in cm from my quoted post was incorrect, but has been corrected.
 
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Any update gentlemen? :D :)

I guess they gave up? :D

I was fascinated by this so I took an 3FE25 Faital 3" driver and mated it with a piece of 3/4" of MDF to a MRII594A Mantaray horn. This horn has a 1.4" input so I routed a small (shallow) rebate to mount the driver flush. I then used a 1-3/8" forstner bit to drill all the way though. Followed with a 1/2" shank 3/4" 45 deg. chamfer router bit.

Tried it out and it sounds pretty good, with a bit of EQ correction. I'm getting some Goldwood GM-450PB 2" horns tomorrow and will try some 2" drivers that are on order. This is gonna be fun :D
 
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