045Be and ~50kHz ultrasonic hearing

[Mr. Widget]

I'm with Ian. I think uber frequency response translates by implication to transient response and clean waveform (no ringing) in the audible range.

I have to admit, I really haven't given it a moment's intellectual energy... I only have a few of those moments so I must parse them out carefully...

My principal criterion for quality in tweeters and the like is how they sound. I have noticed that tweeters that sound really good to me, several ribbons, some of the better Dynaudio fabric domes, the Scan Speak ring radiator, the 045Be... and yes the TAD ET-703... coincidentally all extend way beyond my hearing range... I do not look for this ability, but the tweeters I have used and really liked have all had UHF extension.

I didn't mention any of the JBL dome tweeters since I have only heard them in JBL systems and don't have the same level of experience with them as these other tweeters. I didn't mention any of the JBL ring radiators since they don't have the extension and I don't think they sound as good as those mentioned above... I have only heard the new JBL/BMS ring radiator at Zilch's so it isn't a fair comparison... I have no idea what it's UHF performance is like, but it didn't have the air and ease that I attribute to a tweeter that has the UHF extension.

After all that... on to my point in response to the quote!

If the purpose of UHF extension is to lower some form of HF ringing in the audible range, why would JBL add super tweeters that start at 20KHz? As most of you know adding a tweeter at that frequency will add a heck of a lot of comb filtering and I can't see how that would help the ringing situation.


Widget

[speakerdave]

After all that... on to my point in response to the quote!

If the purpose of UHF extension is to lower some form of HF ringing in the audible range, why would JBL add super tweeters that start at 20KHz? As most of you know adding a tweeter at that frequency will add a heck of a lot of comb filtering and I can't see how that would help the ringing situation.

We could ask them, I guess, or we could speculate on the possibilites, one of which might be that, like you, they think it sounds better.

Related question: I have often wondered: In music it is not really sine waves we are talking about. Question: does the first rise of a fast transient of a lower frequency go to the HF driver instead (or both).

David

[speakerdave]

If the purpose of UHF extension is to lower some form of HF ringing in the audible range, why would JBL add super tweeters that start at 20KHz? As most of you know adding a tweeter at that frequency will add a heck of a lot of comb filtering and I can't see how that would help the ringing situation.

I have also seen (can't remember where, except it was not a flakey source) it said that above 10kHz all you need is noise for the effects you describe--air, that is.

David

[johnaec]

If the purpose of UHF extension is to lower some form of HF ringing in the audible range, why would JBL add super tweeters that start at 20KHz?

Personally, in the case of UHF crossed over at 20KHz, I'm willing to bet this was done to "keep up with the Jones" more than anything else, however unfortunate that motivation might be. Word probably got around that JBL's were "only" good up to 20K - 27K, and by extending this up to 40K, (and probably "quality" 40K), JBL is able to promote the new Studio L series as at least equal to so many other "audiophile" series speakers that promote this specification, regardless of how relevant it might be. In other words - marketing.

Of course, I could be wrong in this, though JBL usually releases some kind of Tech Note when they want to publicize significant new technology gains, (think of all the tech notes at the Pro site about technological innovations, and all the tech info on the K2 series). The lack of such info makes me question the significance of 40K UHF, at least in JBL's opinion.

John

[hapy._.face]

Another thing to ponder- is the frequency extension (in part) simply one of the inherent characteristics of beryllium?

[Mr. Widget]

Related question: I have often wondered: In music it is not really sine waves we are talking about. Question: does the first rise of a fast transient of a lower frequency go to the HF driver instead (or both).

It absolutely goes to both. If you play a square wave through a multiway speaker system and disconnect the tweeter it rounds the corners of the square wave (reduces the attack) and subjectively dulls the sound as expected.

I have also seen (can't remember where, except it was not a flakey source) it said that above 10kHz all you need is noise for the effects you describe--air, that is.

I believe this is a topic that is still controversial among noted professional audio system designers. It is certainly part of the logic behind upsampled low res digital audio.

Personally, in the case of UHF crossed over at 20KHz, I'm willing to bet this was done to "keep up with the Jones" more than anything else...

I hope that is not the case, but it may be. In the vagaries of the real world marketplace, businessmen will do anything to make a buck... JBL is not immune.

Another thing to ponder- is the frequency extension (in part) simply one of the inherent characteristics of beryllium?

I guess you are talking about the 045Be? Two ways to extend frequency response are by adding magnetic horsepower and by using a stiffer lighter diaphragm. In the case of compression drivers the phase plug also comes into play... but we were talking about the effects of UHF on sound and their relevance.


Widget

[gtimbers]

The plain and simple reason for the existance of the 045Be and 045Ti is that the 435Be and 435Al (2430 and 2435 are similar) have a substantial response problem around 10 kHz on many horns and are ceratinly dead by 15 kHz. In the digital age of SACD, our friends in Japan who requested the development of the K2.S9800 insisted on good response at least to 40 kHz. There is no way we could have just used the 435 and had it dump at 15 kHz. We needed to do something at least to clear 20 kHz and we didn't want to make a toy add-on device for a product of this stature. With this said, we did the best we could to develop a dedicated UHF compression driver using a 1" diaphragm. We have two diaphragm materials available for cost reasons. The raw Be diaphragm costs us $100 each! The Ti diaphragm we form in house for about $1.50

The Ti unit is pretty level out to 30 kHz (at 100 dB for 2.83v), then has a bit of a peak and finally dies around 40 kHz. The Be diaphragm is a straight line from 5 kHz, where it is 105 dB (2.83v) to about 60 kHz where it has declined to 95 dB. This is on a horn that holds a 60 H by 30 V pattern all the way out to 40 kHz before it starts to narrow. So there actually is a valid Engineering and Marketing reason for this device to exist.

Does it really matter that we go to 40 kHz or even 60 kHz? Good luck in figuring that out because I'm not going to touch that discussion with a 10 foot pole. I will say that this is our 60th year anniversary and the question may not be unanswered very much longer.

[Robh3606]

Thanks Greg for the post.

Rob

[JonathanKeehn]

I think some of the respondents to this thread have it backwards. The high frequency extension of the beryllium diaphram is a by-product and function of its inherent physical characteristics of super light mass, sound propagation velocity and pistonic stiffness, which incidentally, result in superior sound reproduction. The resulting high frequency extension is a nice collateral result to brag about on a spec sheet. In addition to my prized JBL speakers I still have a 29-year old pair of Yamaha NS-1000's which have beryllium domed tweeters and midranges. From my perspective, their tweeters sound better than the 2405's except for dynamics. I am glad that JBL finally went to beryllium in their best drivers. As to being able to hear a diference at 50Khz, I think there may be some psych-acoustic impact, but that is secondary. The main benefit is the overall sound improvement. Kudos to JBL. I am saving up for a pair of used K2-S9800's.

[speakerdave]

So cool.

[Mr. Widget]

....and the question may not be unanswered very much longer.

Hmmm thanks for the intrigue!

I'll add... I have listened to the 045Be extensively and love their sound quality and air. Yeah, yeah, I've said that before ...however I am able to enjoy this air with a digital front end that does not produce signal above ~24KHz... as with all digital devices any signal above a certain frequency determined by the designers and based on the sampling rate is filtered out... gone, nada... so if I can hear air with the 045Be and not so much with the 2405... well, I don't think it is due to the reproduction of the frequencies above my hearing range... it very well may be due to the fact that the distortion and break up have been pushed beyond my hearing.


Widget

[hapy._.face]

Well....that explains it all. They needed something to go over an already high frequency hurdle-

However, this is the best part:

The raw Be diaphragm

Note the word 'RAW'.

I always wondered if the Be was a coating, or "true" or 'raw'; Now I know.

The raw Be diaphragm costs us $100 each!

I'd also like to buy several boxes of those diaphragms at the "whopping" $100 each price!!

Seriously, it's nice to see that there were few compromises made in your desire to make a wonderful statement speaker. Your posts are extremely enlightening and highly welcomed. Thank you for taking the time to explain it to us! One last thing: did you guys ever do any animal testing (bats) when developing the 045be?

[Maron Horonzakz]

Now if I could only find a microphone that go,s to 60 K.

[hapy._.face]

Now if I could only find a microphone that go,s to 60 K.

http://www.bksv.com/pdf/Bp1844.pdf

Also here: http://www.acopacific.com/chart.html (models 7016 and 7017)

..and here: http://www.bksv.com/pdf/Bp1851.pdf

Actually, a google search will turn up many more. Manley has been making the gold ref mics for some time and they are rated flat (mind you) to 30kHz, but the roll off is much much higher.




Getting back to the origins of the thread, I stumbled on an interesting article while learning about the affects/effects of >20kHz response. It would appear that there is something altered with respect to phase (and it's relationship to overall sound quality) when sampling rates are diminished in UHF response; If so, it would stand to reason that preserving the actual frequency response of certain instruments throughout the entire sound reproduction chain could result in "better sound". This stuff is fascinating. A very good read: http://www.resolutionmag.com/pdfs/TECHNO~1/CAREAB~1.PDF

[Maron Horonzakz]

B&K 4938.....long term stability 1000 years I should live so long.