The BMS4550 seems to be a golden standard for 1" based MEHs. Are there any alternatives (with up to double its price)? I really like the Beyma CP755 compression driver, it is a 1.4", so its equivalent would be BMS4554. My next MEH build will use a planar driver for HF, but I still do not want to give up on the classic construction and its higher SPL potential - and I am still undecided whether 1" or 1.4" driver and which one. I think the horn itself can be built in a way that it would work for both dimensions with different 3D printed (or machined) throats.
I may be wrong, but I think that BMS4550 is used so often is because it can be crossed lower. I look at the datasheet and nsd1095n has a suggested Frequency Response: 1600-20kHz, with a recommended Crossover Frequency: 1600Hz
https://www.loudspeakersplus.com/18-Sound-NSD1095N-p/18-sound-nsd1095n.htm
https://www.loudspeakersplus.com/18-Sound-NSD1095N-p/18-sound-nsd1095n.htm
How about this one? Anyone has experiences with it?
https://audioxpress.com/article/test-bench-the-bms-1-5530nd-high-efficiency-compression-driver
https://audioxpress.com/article/test-bench-the-bms-1-5530nd-high-efficiency-compression-driver
The BMS4550 (and the new 5530ND) has a 1.75” (44.4 mm) voice coil centered in an annular (ring) diaphragm, which has less Sd (diaphragm area) than a dome diaphragm with an equivalent voice coil size.
The Beyma CP755 has a 2.87" / 72.2mm dome diaphragm, around 3 times more Sd than the BMS4554, which has the same Sd as the BMS4550.
Doubling Sd allows a 6dB increase in output level, the BMS4554 is not at all the equivalent of the Beyma CP755 or any other driver with more Sd.
The exit diameter of the driver has almost nothing to do with the low end response.
The high frequency driver’s low frequency output is excursion limited by its Diaphragm to Phase Plug Space (DPPS). The DPPS is generally less than 1mm. Even the large diaphragm (3” & 4”) JBL drivers have a DPPS of only .5mm.
Since HF compression driver excursion is so limited, Sd determines how much output level is available at 1kHz and below, where excursion limits typically will be reached well before power limitations occur in modern drivers.
Typical dome diaphragm size for 1" exit vary from as little as 1" to 2", a Sd range of .784 to 3.14 square inch.
Typical dome diaphragm size for 1.4" exit can go up to 4", 12.5 square inch Sd.
The difference in output around 1kHz could be more than 24dB depending on the diaphragm behind the exit..
Art
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Thanks for the clarification, Art. I mention the exit size due to construction. I found out I have also a D.A.S. M50 driver which should be good down to 1 kHz as well and fine with home SPL levels - and hopefully better HF than the DE500. The max SPL capability of the HF driver is something to keep in mind, very useful information.
Just a small update. I was lucky enough to get a pair of BC DE75s and Beyma CP755Nds second hand in perfect shape and for a great price, so these will be the base of my following synergy horn experiments.
But practicaly as a larger exit driver can have a larger diaphragm diameter they are likley to be able to be crossed lower. Attached are some images of high output Danley models if you want to play identify the compression driver. For high output the HF1440 looks good to me with a low minimum crossover and small size.
Attachments
Pelanj, I noticed from your 1st post that you intend to use a planar driver in your next build. The only manufacturer I know who produces them is Radian. I had such a driver mounted on one of their concentric speakers. The measurements were totally disappointing and the response from Radian was that this was normal. Caveat emptor.
Annular ring compression drivers don't seem to have a phase plug directly infront of the diaphragm so could be capable of greater excursion than domes?
https://patentimages.storage.googleapis.com/ee/3a/60/0178940b913c8a/US20130243232A1.pdf
https://patentimages.storage.googleapis.com/ee/3a/60/0178940b913c8a/US20130243232A1.pdf
@vacuphile In that post I am refering to this (WIP) design using GRS PT 6816 and Fane Sovereign 8 - 225: https://www.diyaudio.com/community/threads/ikea-kallax-meh-unity-synergy-speaker.382400/ Right now, I am enjoying this one (it still needs some crossover tuning) using ESS AMT https://www.diyaudio.com/community/threads/ess-amt-1-in-my-projects.349546/post-6891749
@kipman725 I think I am happy with the drivers I have now - both should be able to be crossed over around 800 and lower for home use. I am not aiming for PA SPLs, so the mids will be most probably 4 x 3FE22 and lows a pair of 10CL51. The mids will be maybe reconsidered - a quadruplet of the popular BC 4NDL34 seems like quite an overkill now, on the other hand the Faitals would be the weakest link...the main reasons I want to use them is that they work really well in my current prototypes. I need to do a high volume test if what I get is enough🙂
@kipman725 I think I am happy with the drivers I have now - both should be able to be crossed over around 800 and lower for home use. I am not aiming for PA SPLs, so the mids will be most probably 4 x 3FE22 and lows a pair of 10CL51. The mids will be maybe reconsidered - a quadruplet of the popular BC 4NDL34 seems like quite an overkill now, on the other hand the Faitals would be the weakest link...the main reasons I want to use them is that they work really well in my current prototypes. I need to do a high volume test if what I get is enough🙂