Lets talk phase plugs and drivers.

[The Dude]

So I have been kicking around the idea to give something with the Beryllium Diaphragm a try.  May not be until next year.  But here is what I was thinking.  Unless I score a pair of TAD's at $1200.00 with the snout, It could get costly (not to bad maybe 1400-1600).  I thought what if I blow one of these and need new diaphragms? Are the readily available, I don't see them all over the net.  So what if I went the JBL 2446 route with the Truextent Beryllium.  Even if I cant find JBL's at a steel with bad diaphragms.  I could pic up a pair for about $250 shipped, then install new diaphragms at about $1200.00.  This puts me at $1450.00 a pair.  The thing I like is that there is replacement diaphragms and no need for the snout adapter that the TADs take. 

 

That brings us to my two questions I have.  First is it the Beryllium diaphragm that makes the sound or does the phase plug come into play?  From the pics I have seen on the net, the phase plugs look similar.  I am not sure if any difference at all is going to make much of a difference in sound.  Second, hmm there was second question I thought, but maybe it was about the phase plug  It will come back to me if important enough.

[Chris A]

...is it the Beryllium diaphragm that makes the sound or does the phase plug come into play?

 

All 2" compression drivers wind up using phase plugs--that's due to the size of the diaphragm relative to the highest frequencies that are reproduced having short enough wavelengths that the diameter if the diaphragm starts to become significant. 

 

It's the material that's important: beryllium is 2.43 times less dense than titanium, and is 2.3x stiffer in bending.  It also has a tensile yield strength that is almost double that of titanium. See http://www.vueaudio.com/wp-content/uploads/2012/04/ALMA_Europe_Symposium_2011-PAPER_Small.pdf

 

There is no contest.  I'm actually amazed that so many "audiophiles" want to avoid using beryllium diaphragms.  To me it's a no-brainer:  it's the single most important factor to consider when comparing 2" compression drivers with a single metal diaphragm.  If you don't have the money for Be-diaphragm compression drivers, then you also shouldn't have the money for expensive preamps, amplifiers and expensive DACs, IMO.  It makes more difference than all of those other components put together in terms of sound quality.

 

Chris

[The Dude]

If you don't have the money for Be-diaphragm compression drivers, then you also shouldn't have the money for expensive preamps, amplifiers and expensive DACs, IMO

 

Considering that most components that people purchase cost more than a pair of TAD's.

 

It's the material that's important: beryllium is 2.43 times less dense than titanium, and is 2.3x stiffer in bending. It also has a tensile yield strength that is almost double that of titanium. See http://www.vueaudio....PAPER_Small.pdf

 

That answers my question.

[Coytee]

beryllium is 2.43 times less dense than titanium

 

(warning, OCD / retentive hat going on)

 

Question....would it not be more accurate to say that the BE is (for example) 43% as dense as TI?

 

Seems to me that if TI has a density of say "100", if you are 2.43 times less dense, you are in the realm of being negative dense? 100*(-2.43)=<243> 

 

I know and get what you mean....   I'm just a bit surprised at the math....unless I'm missing something.

 

Had you said TI was 2.43 times more dense than BE, it would make sense.

 

Now, had you used this to describe me, my wife would agree as she often describes me as being negative dense!

 

[Chris A]

Yes Richard.  Beryllium beats titanium or aluminum as a compression driver diaphragm material by a large margin.  It's not close.

 

I find that most people don't seem to be aware of the large difference.

 

Chris

[DrWho]

That brings us to my two questions I have.  First is it the Beryllium diaphragm that makes the sound or does the phase plug come into play?  From the pics I have seen on the net, the phase plugs look similar.  I am not sure if any difference at all is going to make much of a difference in sound.  Second, hmm there was second question I thought, but maybe it was about the phase plug  It will come back to me if important enough.

 

From a system perspective, they both matter...and one might even argue that the phase plug and diaphragm are designed together.

 

That said, I'm not sure I've seen any data comparing phase plugs between any compression drivers out there. I think that's probably because the diaphragms have the largest impact on the flavor of the sound.

 

I also don't tend to listen at 140dB SPL either....and I SPL match my distortion / wavelet comparisons.

Edited February 26, 2016 by DrWho

[Chris A]

From a system perspective, they both matter...and one might even argue that the phase plug and diaphragm are designed together.

 

I've seen data on a JBL 2452 drivers with Be diaphragms that were only marginally better than Ti.  That's an indication that there are some design issues when switching from Ti to Be.  There should be an obvious flattening of the phase and amplitude (in frequency response plots) using Be, and more output above 15 kHz.  If there isn't then I'd look at another driver and Truextent Be diaphragm combination.

 

Chris

[The Dude]

phase plug and diaphragm are designed together.

 

Something I read earlier over at James B. Lansing forum.  Which brought up another question. If drivers and phase plugs are designed to work with certain horns.  How could one tell if a driver of one brand is going to work with a horn of another.  Could it be that even engineering specs on paper couldn't answer this, but mainly trial and error?

 

 

If there isn't then I'd look at another driver and Truextent Be diaphragm combination.

 

That is why I was looking at the JBL 2446, however looking at the specs there seems to be a nice drop around 9000 hz. 

http://www.fullcompass.com/common/files/7948-2446.pdf

 

But would installing the BE change any of that, or just make it easier to eq the higher frequencies?

[Chris A]

Impulse measurements are usually the most revealing: http://www.audioheritage.org/vbulletin/showthread.php?31657-Truextent-diaphragms-measurements

 

They're testing the same diaphragms that go into the 2446H against the Truextent Be diaphragms, although they're not using the 2446 itself.  It should be representative. 

 

I don't see a lot of difference.  For instance, when you compare a TAD TD-4002 vs. a K-69-A, you see the following:

 

 

Guess which one is which...

[moray james]

 

phase plug and diaphragm are designed together.

 

Something I read earlier over at James B. Lansing forum.  Which brought up another question. If drivers and phase plugs are designed to work with certain horns.  How could one tell if a driver of one brand is going to work with a horn of another.  Could it be that even engineering specs on paper couldn't answer this, but mainly trial and error?

 

 

 

 

If there isn't then I'd look at another driver and Truextent Be diaphragm combination.

 

That is why I was looking at the JBL 2446, however looking at the specs there seems to be a nice drop around 9000 hz. 

http://www.fullcompass.com/common/files/7948-2446.pdf

 

But would installing the BE change any of that, or just make it easier to eq the higher frequencies?

 

all compression drives require EQ to achieve flat response that is normal. To match a driver to a horn you want the exit angle of the driver to match the entrance angle of the horn so you don't get reflections and the mouth area of the driver must match the throat area of the horn. That is the start then you need to establish if the horn and the drive work well together and that the horn has minimal reflections back into the driver. 

   You can try some home made in a few minutes Karlson K-Tubes on any driver you like and I think that you will find it difficult to find horns that can mate as well. You sure cannot beat the cost they are almost free to make and they can sound very good. I run a set of paper double cutaway K-Tubes on my EV DH1A drivers with the nose cup extender removed the driver has a 1.4" exit I prefer the K-Tubes to any horns I have used. YMMV why not experiment?

Edited February 27, 2016 by moray james

[DrWho]

 

 

phase plug and diaphragm are designed together.

 

Something I read earlier over at James B. Lansing forum.  Which brought up another question. If drivers and phase plugs are designed to work with certain horns.  How could one tell if a driver of one brand is going to work with a horn of another.  Could it be that even engineering specs on paper couldn't answer this, but mainly trial and error?

 

 

 

 

If there isn't then I'd look at another driver and Truextent Be diaphragm combination.

 

That is why I was looking at the JBL 2446, however looking at the specs there seems to be a nice drop around 9000 hz. 

http://www.fullcompass.com/common/files/7948-2446.pdf

 

But would installing the BE change any of that, or just make it easier to eq the higher frequencies?

 

 

You need to look at the plane wave measurement - not the frequency response of this driver mounted on the 2380A horn.

 

The only significant aberration I'm seeing is a big dip at ~12kHz. It's not clear to me if it's a cone breakup issue, or a phase plug issue - both can create a response anomaly like that. Unfortunately the impedance response is overly smoothed to not provide any clues as to the behavior - but even that isn't always conclusive. Also, a 2" plane-wave tube is too large to support true plane waves above 6.8kHz. So the combination of side-wall reflections in the tube, diaphragm flexing, and phase plug limitations can all be factors in that specific measurement environment. I think the dip at 12kHz is real, but some of that smaller sharper jaggedness can just be the measurement method.

 

All that to say, going to a stiffer diaphragm may smooth out the ripples that start happening above 7kHz, but I wouldn't hold my breath. I have read that part of the phase plug equation is keeping the pressure low enough to not overcome the diaphragm stiffness. The modifications to the phase plug to achieve that goal can lead to the phase plug itself causing ripples (due to phase cancellation of the multiple path-lengths, and lowering the resonant frequencies of the chambers). Going to a stiffer diaphragm would allow for a different phase plug design, but you're not changing the phase plug here.

 

 

Another thought to throw out there (since we're talking about diaphragm materials). No matter what, the diaphragms are going to flex - and we have source material that will have larger amplitudes followed by short amplitudes (the natural dynamics of music). To some extent, the sound that we hear is very akin to striking the diaphragm like a cymbal - which will ring and have its own characteristic sound. Actually striking the diaphragm is a bit exaggerated since we don't have that kind of impulse generated by our source material, but I think it's helpful to think that way when comparing the diaphragm types. It's much like using an impulse response to characterize the acoustics of a large hall.

 

Anyways, one of the reasons I like the BMS drivers is because they use Polyester diaphragms. It's nowhere the stiffness of Beryllium or even Aluminum, but it's intrinsically a much more damped material. Striking it like a cymbal almost makes no sound whatsoever. The stiffer Berrylium drivers ring a ton more - they just push it up higher in frequency. BMS is also taking advantage of the annular ring geometry to provide the stiffness they need. I wouldn't use these kinds of diaphragms for huge SPL environments, but for home listening I think it's a much more natural sounding diaphragm - and it matches closer to the distortion characteristic of the paper diaphragms we're using on the woofer sections. It basically allows for an easier to voice system. Ya, it might measure slightly higher distortion and the annular ring has to move further than a standard diaphragm since it inherently has less radiating surface area - and its radiating surface area modulates with excursion.....but all of those things matter less as the SPL gets lower and lower. The stiffness of the diaphragm is an issue at all SPLs - in other words, the diaphragm bending is proportional to the driving force - less SPL, less bending, but the bending proportion to the SPL stays constant so the distortion doesn't necessarily improve at lower SPL. This is way over-simplifying the topic and I bet the compression driver designers out there would probably cringe reading this, but it's the best I can understand it based on what I've read thus far...The simple observation I'm making is that BMS can achieve similar performance with a much softer material because they're using geometry to their advantage. One consequence is that they can use a more natural sounding material. The diaphragms simply can't ring because the material is over-damped. I personally don't listen anywhere near the levels of the rest of you crazies, but I personally would take the BMS over the TAD all day long. The fact that it's cheaper is totally irrelevant - although still certainly a plus. I wanna see BMS come out with a dual annular ring that fires from both sides - basically a free 6dB less distortion.

 

The only point I wanted to make was to consider the inherent characteristic sound of the various diaphragms as "measured" by its "cymbal-like" properties. Somewhere there is a CSD plot showing less in-band ringing from a Mylar diaphragm when compared against Titanium, Aluminum, and Beryllium. Having a Beryllium description doesn't automatically mean it's a better driver - it's gotta be designed with the specific system goals in mind. Most of the guys pushing for Beryllium are doing the crazy high SPL stuff. JBL almost openly admits their Vertec system is only about SPL...they're making tons of distortion compromises along the way to get there. They're the biggest user of Beryllium diaphragms that I know of...

 

And how come we don't see any Berylium direct radiators?

Edited February 29, 2016 by DrWho

[absolve2525]

Yamaha NS1000 speakers have direct-radiating Be mids, as well as Be tweeters. They've been around quite a while, and are highly regarded. Amazing sound. I don't discount BMS having amazing sound either. I had a set of their coaxial compression drivers when they first came out, and I imagine they're even better now.

Edited March 2, 2016 by absolve2525

[The Dude]

I didn't think to include aluminum as a materiel.  How does it compare to titanium?  If I have this right.

 

Faital PRO HF200 = Titanium

Most of JBL = Aluminum

BMC = Mylar

TA = Beryllium

 

Which most will have a different sound.  I need to see what the EV Dh1a have, those aren't bad. 

[Chris A]

If you look at the Truextent white paper, it discusses the relative physical properties of the type of Be, Ti, and Al alloys used in compression driver diaphragms. 

 

Generally, If I had a choice between only Ti and Al with very little other information, I'd choose Al since it rings less, all other things being equal.  There's a lot that the manufacturers of compression drivers don't tell you...for instance, go find compression driver TS parameters.  Good luck with that.

 

Ti diaphragms were developed mostly because they are more rugged and do not experience fatigue failures associated with commercial (PA, i.e., very loud) sound reinforcement, whereas Al can work harden and crack at extreme and extended periods of high SPL--a consideration that really doesn't apply to home hi-fi environments.

 

Chris

[The Dude]

I didn't think to include aluminum as a materiel. How does it compare to titanium? If I have this right.

Faital PRO HF200 = Titanium

Most of JBL = Aluminum

BMC = Mylar

TA = Beryllium

Which most will have a different sound. I need to see what the EV Dh1a have, those aren't bad.

Apparently i was wrong, the jbls and evs are titanium. Only the Radians are aluminum. Maybe the bmc's are as well.

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Edited March 2, 2016 by duder1982

[moray james]

Duder:  Be, aluminum, titanium, and way down the stiffness list are plastic resins. Hardest and lightest in order. Aluminum is a superior diaphragm material to titanium but ti does not work harden like aluminum. So if you over drive a pair of aluminum diaphragms and they slap the phase plug you will either break them or they will harden and break where ti will not and that is the reason ti is popular in pro it is harder to damage not better sounding in fact ti will break up sooner than aluminum and some folks are very sensitive to that break up and do not like them. Personally I am ok with it the ok club is much larger than the not ok club. If you read the JBL posts at Lansing Heritage you will find that the aluminum skins are preferred to the ti skins for sonic quality.

   Soft diaphragm materials can work well it compression ratios are kept on the lower side so they can and do work and they sound good they just cant do the high compression duty jobs.

[The Dude]

Talking drivers in general. I pulled my EV Dh1a off of the EV horn and noticed that the gasket material was squeezing out into the throat area.

Is this a problem? Should it be trimmed to give a clear shot through the throat?

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[moray james]

why don't you take the extender nose cup off and run them as 1.4 inch exit drivers rather than 2" exit drivers? Better top end extension that way.

[The Dude]

why don't you take the extender nose cup off and run them as 1.4 inch exit drivers rather than 2" exit drivers? Better top end extension that way.

I had thought of it at one point, but came across a decent deal on some 2" entrance horns.

[djk]

"why don't you take the extender nose cup off and run them as 1.4 inch exit drivers rather than 2" exit drivers? Better top end extension that way."

 

You could, but the bolt circle  is non-standard.