Best Compression Drivers today 2022?

Cask05 · 2023-04-11 9:35 am

Snickers-is said:
I can recommend that book, but it is kind of a heavy one in more than one way.

I think it is a good time to recognize this book referenced in the same light as Beranek's Acoustics and Olson's Acoustical Engineering (both originally published in the 1950s, and texts that I still refer to quite often). If you want to understand what are the best compression drivers for predominantly home hi-fi service, you also must talk about horns and bass drivers/horns at the same time, I believe.

These two gentlemen (Kolbrek and Dunker) did yeoman's duty to update and significantly expand the information in the other two texts referenced on the subject of horn loudspeakers. This is pretty important to the continued advancing of the state of the art (SOTA) for horn loudspeakers. There was a long standing need to update those older books on the subject of horns, and High Quality Horn Loudspeaker Systems has done that in my estimation, as well as preserve the historical record of horn loudspeakers from the early 1900s through to the present. I recommend it highly for horn DIYers. It will likely save a lot of false starts and dead-end projects in favor of much more informed and successful ones.

It is this additional need for domain knowledge that sets apart horn loudspeaker development from typical direct radiator loudspeaker projects. There really isn't a "loudspeaker cookbook" for horns, if you've searched for such a thing. It takes more knowledge to lead to successful horn designs than building a box and fastening bought drivers to it with some cookbook electrical balancing networks.

Chris

mountainman bob · 2023-04-11 1:14 pm

Pano said:
This summer I'd like to try the TexTreme Eminence drivers in place of the BMS, I hope that will happen. However I'm not sure if they will survive my lower crossover point. Eminence recommend a high pass at 800Hz second order. I'm currently at 499Hz 4th order Linkwitz-Riley, which puts almost 2X the power into the driver in the 500-650Hz range. I'll have to carefully measure how much voltage I'm sending out in that range.

I’m curious about your results because i’ve read several different subjective reviews on the N314X-8 and they all seem to come to the same conclusion that it sounds best above 1k ………. I’ve got a build in mind thats going to require 800hz and really like this driver but don’t want to find out the hard way.

Pano · 2023-04-11 1:19 pm

Well yes, that does worry me, as I can't really cross up that high. In the video they mention how well it does in the low end, but no specifics.
The BMS coaxials are very clean and smooth down at the bottom end of their range. I'll talk to the boys at Eminence before I try them.

grataku · 2023-04-11 7:07 pm

Is that a question of power or excursion at lower freq? I am measuring 150mW of power at more than enough listening levels on my compression drivers.
We're not talking outdoors spring break keg party levels. I have a sense it will be just fine. 😉

ErnieM · 2023-04-11 9:32 pm

Maybe the Faital HF1460 would do better down low with its larger surface area.

phase_accurate · 2023-04-12 8:10 am

Snickers-is said:
I can recommend that book, but it is kind of a heavy one in more than one way. But it lead me to develop this 460x400mm horn:

Horizontal:
View attachment 1163468

Vertical:
View attachment 1163469
It is powered by a 18s 1480Be, and it is clear by the simulations that what happens around 14-16k is related to the wavefront coming out of the phase plug.

I therefore started work on a compression driver that solves this issue. It is a carbon ring radiator with a 3D printed phase plug.

That looks very nice. What is the horn contour ? Is it exponential with an added roundover ?
At which frequency do you cross over ? If you don't need the LF extension of the ND4080BE you could use the ND3Be instead. But guessing from the horn's size you possibly cross lower than 1 kHz.

Regards
Charles

Snickers-is · 2023-04-12 8:50 am

It is not a standard contour, so that is a bit hard to answer in a simple way.

I cross it over at 750. Not sure what 4080 is, I guess it is a typo for 1480? Just to avoid any potential misunderstanding, I used the 1480, and not the 4015 as the horn is 1,4 inch entry.

BTW, the cutoff and depth of this horn fits very well with a Harsch filter.

phase_accurate · 2023-04-12 9:49 am

Yes, I meant 1480. And if you cross at 750 Hz, the ND3BE would most probably not like it.

Regards

Charles

Snickers-is · 2023-04-12 9:58 am

Well, I am not sure the 1480 is that much better at low end. The driver we are going to use is not finished yet.

Pano · 2023-04-12 12:16 pm

grataku said:
Is that a question of power or excursion at lower freq?

Yes, outdoor theater - 2800 seats. But moderate levels.

Snickers-is · 2023-04-12 12:25 pm

I am pretty sure you can not expect anything near what you get from a BMS 3,5" from that 314X at the low end.

grataku · 2023-04-12 2:00 pm

Pano said:
Yes, outdoor theater - 2800 seats. But moderate levels.

seriously? 🤣 my mistake.

Pano · 2023-04-12 2:51 pm

Yeah. They used to be in my home system, but are now entertaining far more people. If you are anywhere near Western North Carolina I'll let you know if I install the Eminence carbon fiber and you can come hear them.

mountainman bob · 2023-04-12 4:38 pm

I thought you moved to Panama……where abouts in WNC ?

Pano · 2023-04-12 4:53 pm

Cherokee NC. Will be there for the summer.

tiefbassuebertr · 2023-04-12 6:53 pm

milezone said:
The drivers which I am referring to are the Beyma CP755ND and its siblings, the Faital HF108, the BMS 4552, possibly the coaxial offerings from BMS and B&C though I have only tested the midrange sections of both drivers and I would say for dedicated midrange the Celestion is obviously superior either the BMS or B&C midrange. And I would concede the Celestion midrange is definitely superior to even an Altec 288 and maybe Beyma CP755ND -- it is able to be easily crossed over 250hz lower than the Altec and Beyma, and is clearer though maybe less musical than the Altec. In addition, in the video linked above, the Celestion engineer details the ways in which coaxial compression drivers have their pitfalls. With that said I have observed a huge advantage in a horn section of a two way or three way speaker functioning as a point source through using a single compression driver to cover a wide range, or a coaxial compression driver, versus stacked horns and drivers. The difference as it relates to coherence and resolution is night and day in my experience. Given this the only logical configuration I would consider if using a Celestion would be to have that driver cover 300hz to 2000hz with a large horn, and suspend a smaller horn concentric within that horn with the a driver that covers high frequencies properly, my choice would be the CP755ND mounted to a waveguide, and apply a time delay to the tweeter section. More interesting to me than this somewhat complex implementation would be an advancement at the driver engineering to recognize and properly implement the advantages of a point source coaxials allowing for the use of a single driver mounted to a single horn to cover a wide frequency band.

Arez · 2023-04-12 11:07 pm

A couple of interesting points on some of the newest, most expensive and frequently mentioned Compression drivers in this thread.

https://josephcrowe.com/blogs/news/celestion-axi2050

https://josephcrowe.com/blogs/news/bms-4599he-revisited

Lynn Olson · 2023-04-13 12:07 am

Surprisingly poor results on multitone IM distortion for the Celestion Axi2050. I would agree with Crowe it is not suitable for hi-fi use at home. The SB Audience Rosso 65CDN-T 1.4" driver that he tested measures 15 dB better, and has better impulse response, too.

Admittedly, the multitone IM test is very severe, but that's the point. The test signal is also closer to the dense spectrum of real music than single-tone harmonic distortion tests.

Cask05 · 2023-04-13 12:42 am

Arez said:
A couple of interesting points on some of the newest, most expensive and frequently mentioned Compression drivers in this thread.

https://josephcrowe.com/blogs/news/celestion-axi2050

Modulation distortion is really a function of the movement of the diaphragm: the more movement, the higher the distortion. When you look at the relative raw SPL on-axis of an Axi2050 vs. a TAD TD-4002 -- both on a K-402, you can see the relative sensitivities of the two drivers. Note the two plots were adjusted to cross at ~7 kHz to show their relative raw response flatness:

It's easy to see the difference in raw SPL at the frequencies that Mr. Crowe mentioned were the breakpoint for modulation distortion and "harshness" (i.e., 2-5 kHz). That's why I originally posted that plot-to show the relative sensitivities vs. frequency of the two drivers, and how much EQ is required to flatten their on-axis SPL responses.

JMTC.

Chris

P.S., it's really nice to see the modulation distortion measurements. I've asked for that capability to be added to REW, but I guess now I have a reason to spring for ARTA. I think that when you pay attention to this particular measure, you're going to see a lot more correlation to subjective judgments of sound quality.

Lynn Olson · 2023-04-13 6:24 am

Which leaves as a puzzle why the SB Audience Rosso 65CDN-T driver is so good ... in every dimension. Far lower IM distortion, first breakup at 17 kHz, waterfalls with fast decay, and yet, it's just another titanium diaphragm like so many other pro drivers.

Did SB nitride-treat the diaphragm? Is their phase plug that much better? How did they resolve the large-format breakup problem in the 10 to 20 kHz region without resorting to Beryllium or carbon fiber?

Conversely, why is the Celestion Axi2050 so poor, considering the scope of the research program that went into it? Yes, it has plenty of output in the lower part of its range ... no surprise given the generous size of the diaphragm. But the HF distortion is really quite poor, especially since J. Crowe is testing at a SPL level well below professional use.

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Best Compression Drivers today 2022?

Cask05

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Pano

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Arez

Lynn Olson

Cask05

Lynn Olson

Best Compression Drivers today 2022?

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