To get any absolute levels was not the aim, nor do I have the equipment for that, but it seems consistent with the BMS data:
https://www.bmsspeakers.com/index.php-473.html?id=4554_curves
What's important is how fast the higher-order harmonics diminish. And they do it really fast with this driver, it seems.
- Maybe this is the driver for a 800-20k waveguide after all.
https://www.bmsspeakers.com/index.php-473.html?id=4554_curves
What's important is how fast the higher-order harmonics diminish. And they do it really fast with this driver, it seems.
- Maybe this is the driver for a 800-20k waveguide after all.
I guess that all these BMS ring radiators are in fact similar, i.e. could be used this way.
The central black aperture is basically where you can start your horn -
(In 4554 this is ⌀16mm, probably the same as for their other similar CDs.)
The central black aperture is basically where you can start your horn -
(In 4554 this is ⌀16mm, probably the same as for their other similar CDs.)
That is very interesting! I have a pair of 5530ND on the way for a project I am working on. I suppose I should remove the bug screen and do a throat insert for that as well. I assume the BMS 4554 just had the mesh glued in place? Did you heat it a bit before removal, or just pull it off with brute force?
The mesh is typically only ~5 mm bigger than the exit aperture and glued. It's not necessary to remove the foam gasket, at least not the whole gasket. Sometimes it's even possible to take the mesh with pliers and just peel it off without damaging the foam. I've never heated any driver.
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The hardest part is typically measuring the internal geometry to make a tightly fitting adapter (if you don't have the equipment). I often end up with pieces of paper and cutting&trying them, until it's accurate enough and then measure those with a caliper.
Would be definitely interesting to see how different adapters work with different BMS drivers. A lot of luck is still needed, I suppose.
It's likely the 1.4" exit version of the 1" BMS 4550. The 4550 too has this shelved response in the low end which makes these drives a great basis for this. The 4544 seems to be very similar, but with a smaller magnet.
How about making 2 extension ducts for 2 drivers, forming a Y combiner? 🙂 Expanding into a rectangle or superellipse of minimally larger area than two 1" exits stacked vertically, then continued expansion by a WG of the same shape. Inspired by https://josephcrowe.com/blogs/news/2094 Or think a WG with narrow verticals, something like the JBL Synthesis 1400.
The B&C DH450 would come to mind if a very compact driver is needed for this (don't know). In post #15,840 shows the extension in the low end, maybe not quite as extended as the BMS drivers. The smaller DH350 16ohm seems to have its HF breakup like 1Khz higher, not sure about its low end.
The B&C DH450 would come to mind if a very compact driver is needed for this (don't know). In post #15,840 shows the extension in the low end, maybe not quite as extended as the BMS drivers. The smaller DH350 16ohm seems to have its HF breakup like 1Khz higher, not sure about its low end.
I guess that the only actual difference between 4550, 4554 and 4555 is the exit angle - it will be like 14°, 27° and 30°. So by itself, the 4550 will reach a bit lower than 4554 or 4555, just due to this. But that's still far from what can be gained by adding a considerably longer, slowly-expanding adapter. For the 4554 the gain is more than 12dB at 600 Hz with the same waveguide. What's special about these drivers is that the horn can start at a very small diameter, so that at 1" (or 1.4") it is already producing a wavefront suitable to feed the rest of the device without directivity issues. You couldn't start at 1" without severe beaming.
Be my guest 🙂
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Why so complicated? Check this BMS. The small slots above the ring diaphragms face eqch other and are guided to the center. From there to one sides outlet. So two diaphragms in one unit. They call it "loudest transcuder ever made....". I like their advertising style 🤷♂️😄
https://www.bmsspeakers.com/index.php-73.html?id=bms_4599he00
https://www.bmsspeakers.com/index.php-73.html?id=bms_4599he00
"Those capabilities make it best suited for:
- Systems for scattering birds from airports
- ...
- High End Audio Loudspeakers" 👍
I have a confession to make - I fell in love with this. It sounds so right and natural....
(4554/EXT)
(4554/EXT)
Serious question: if we double the displaced air volume by using two 4554 in compound as the 4599 does: how much lower would theese 6db bring us? I already have a bms midrange here which I wanted to modify for a synergy horn. So this 2-driver thing is rrally quite easy if you know the guts of theese drivers. I would just like to know if its worth the effort...
Yesterday I printed a test adapter with just one perimeter and see what happened.
red = the one-perimeter print
blue, green = the previous two adapters, two-perimeters prints
3rd, 4th, 5th harmonics:
I suspect that the one-perimeter print wasn't airtight, that's the only explanation I have. After I sprayed a layer of acrylic coat over it, the distortion jumped down to the levels of the other two. Strange things may happen and one has to be always careful 🙂
red = the one-perimeter print
blue, green = the previous two adapters, two-perimeters prints
3rd, 4th, 5th harmonics:
I suspect that the one-perimeter print wasn't airtight, that's the only explanation I have. After I sprayed a layer of acrylic coat over it, the distortion jumped down to the levels of the other two. Strange things may happen and one has to be always careful 🙂
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Did you ever measure distortion comparison for an extended vs. a 'regular' length adapter?