Tweeter question

[Coytee]

When I was in college, I asked one of the physics professors a question. I'll try to paraphrase it here.

If a tweeter goes up to "X" khz, if you had a similar tweeter that went up to say, "2 * X" Khz, since the second one that played higher could vibrate faster, would it follow that it MIGHT be able to 'fill in' with a bit more detail than the lessor tweeter, within the range of the 'lessor' tweeter?

Meaning, could the higher freq tweet sound better & more revealing at the same freq levels the first one is playing? (obvious the first tweet coudn't compete at the higher ranges if it didn't go there)

He kept telling me that I was asking a "power" related question. I never quite got the angle on how this question was related to power, so I finally acquiesced to his comments and left his office with him thinking he'd answered my question.

[mark1101]

When I was a little boy (like 40 years ago) my dad would sometimes say to me (as a joke for HIM), son...between me and your Uncle Joe...we can answer any question you could possibly think of. Coming from an engineering family this would be the kind of teasing I grew up on.

So, I'd always bite and come up with some outlandish question like....OK dad, how many teeth does a shark have? My dad would always respond the same way. Son.....your Uncle Joe knows the answer to that one.

I expect a post from Jacksonbart at any time now.

[JohnA]

Some people think so. They say the ear can't hear above 20k, but it can hear the "difference" between 20k and 30k (10k)

A
tweeter that can go higher can, theoretically, produce faster
transients, but does the music have transients that sharp? Don't
know..

[John Warren]

Coytee-

It's a comparison of bandwidth.

Assume tweeter A (K77) is flat from 4-13kHz and tweeter B (JBL 2404H) is flat from 4-20kHz. Tweeter B has a larger bandwidth and therefore has better transient behavior

jw

[DrWho]

Assume tweeter A (K77) is flat from 4-13kHz and tweeter B (JBL 2404H) is flat from 4-20kHz. Tweeter B has a larger bandwidth and therefore has better transient behavior

But with the same motor and diaphragm, Tweeter A (with the narrow bandwidth) is going to have less distortion in its bandpass, all other things being equal. I think that is what Richard is trying to get at??? As bandwidth increases, the efficiency decreases, and with the loss of effiency comes an increase in distortion (as PWK was always so adamently pointing out).

That said, the JBL 2404H has a much better motor...so it's not quite apples to apples. A tweeter with a wider bandwidth while maintaining the same efficiency is always going to sound better (unless there is something blatantly stupid with the driver).

Of course, the conclusion to this is that we should pursue systems with many different drivers playing narrow bandwidths. The problem here is that many-way systems are physically spread out, causing all sorts of other issues: like comb-filtering, and crossover distortions. "It's all about compromise"

[ZAKO]

JBL 2404 can be used with two typs of diaphrams....One is thinner .0022 in The mass being lighter will extend bandwidth. +_ 3db. 7k to 20k.. The thicker diaphram 5k to 15k. Same gap size & magnet.

[John Warren]

edit-

DrWho-

Frequency response and distortion are not related. They are two different things.

Bandwidth is directly related to transient behavior, higher bandwidth means better transient behavior. A 4kHz fundamental will have harmonics at 8. 12, 16, 20khz. A 4kHz fundamental with harmonics up to and including 20kHz cannot be reproduced accurately with a tweeter that has a operating bandwidth between 4-13kHz.

jw

[DrWho]

Bandwidth and efficiency are related (per Hoffman's Iron Law).
Efficiency and distortion are related (per PWK). Therefore bandwidth
and distortion are also related? Is not frequency intermodulation
distortion a direct function of the bandwidth and efficiency of the
system?

Take a driver that can do 6kHz - 20kHz and then modify the
suspension to achieve 3kHz - 20kHz. The efficiency of the driver will
go down...I wanna say 6dB? If you are using a squaker that is equally
good between 3kHz and 6kHz, then the tweeter with the smaller bandwidth
should sound better. It works the other way too, take a driver that can
do 6kHz - 40kHz and then modify it to do 6kHz - 20kHz. Shouldn't
efficiency increase by 6dB? Whether or not you need 20kHz, 40kHz, or
even 15kHz extension is up to the designer.

Klipsch obviously
feels that 17kHz is plenty and doesn't bother to sacrifice either
efficiency or costs for higher extension. It's not like they don't know
how to make a tweeter go higher in frequency... [^o)]

Btw, if a
person can't hear above 20kHz, then the extra transient response
obtained by a tweeter that can do 40kHz is also going to be inaudible.
Isn't transient response and frequency response just two different
perspectives of / two ways to describe the same thing?

I have
also read that the mass of the diaphragm has nothing to do with the
high-frequency extension or transient response (provided you don't run
into cone-breakup). I have read that it has only to do with the
inductance of the voice coil. So to get a tweeter to go higher in
frequency, you need to reduce the number of windings on the coil, which
then requires an increase in Bl to maintain the same force on the diaphragm.
I've read another article on it, but here's an article from a subwoofer
driver manufacturer. As far as I know, the acoustics for high and low
frequencies should be the same...

http://www.adireaudio.com/Files/TechPapers/WooferSpeed.pdf

So I wonder if the number of windings for the 2404 are the same for
both types of diaphragms that can be used??? And there just happens to
be a difference in weight because of it?

[John Warren]

There is no inherent relationship between efficiency and distortion.

jw

[John Warren]

JBL 2404 can be used with two typs of diaphrams....One is thinner .0022 in The mass being lighter will extend bandwidth. +_ 3db. 7k to 20k.. The thicker diaphram 5k to 15k. Same gap size & magnet.

Maron-Are you using those K55s I sold you as earphones?

[DrWho]

Then PWK was full of crap in the Dope from Hope, and also Rich Fields who gave a talk at the AES last year...[^o)]

I wish I had the formulas in front of me, but a decrease in efficiency results in an increase in cone movement for the same SPL. For a fixed diameter driver, the cone is still moving the same distance so those distortions won't change. However, the amount of power required will be increased and distortions related to voice coil temperature are going to increase. I know I'm really butchering this, but there were like 5 variables that affect the efficiency of the system - and as any of them changed to cause a decrease in efficiency, distortion increased. It's a direct conclusion of the math for modelling the behavior.

Is the model false? If so, you have but to name the better model you're using.

[PrestonTom]

Mike,

I don't think anyone is disputing PWK's observation that more efficient systems tend to show less distortion.

I believe John Warren was being very precise when he used the phrase that there was no "inherent relation". In this light, re-read & think about what he stated.

Good Luck,

-Tom

[linkalley]

hey john! it is good to know that horonzak bought your nasty ear phones. this incident only confirms what i have been telling maron for years. he cannot hear well. in fact, in ok. land, we say that maron cannot hear worth a damn. truly a shame since the man is so knowledgable & technical but nearly deaf!!! truly a cryin shame. now i understand why he is getting rid of his jbl2451 aquaplus drivers. he is passing the torch on.

maron, how are those ear phone k 55 drivers working???

[bodcaw boy]

There is no inherent relationship between efficiency and distortion.

jw

there is an inverse transfer function between efficiency and distortion in a given acoustic system.

[PrestonTom]

There is no inherent relationship between efficiency and distortion.

jw

there is an inverse transfer function between efficiency and distortion in a given acoustic system.

Roy,

We need to be careful on this.

On a "given system" there is only one efficiency and there is only one distortion. I believe the function requires that you look across various systems. This is more than a question of semantics. I don't dispute that the relation (in this case a correlation) is probably true. But you are now implying a mechanism. But really, any system can be driven into a non-linear range.

Gee, maybe I should let John speak for himself .....

-Tom

[pzannucci]

Are the operative words "in a given acoustic system" the key. That would say that any change in drivers, driver function such as voice coil, cone, etc, would change the given acoustic system. So am I missing something if I say that the theory is correct but the actual ability to implement the theory is the next to impossible part? This is why John's remark about the relationship between efficiency and distortion is wrong because you have to change the "acoustic system". There are many very low distortion lower efficiency speaker systems available. Sorry but just trying to understand where theory intersects with the real physical world.

[DrWho]

There are many very low distortion lower efficiency speaker systems available.

I
used to feel the same way until that talk Rich Fields gave and I did
some retrospective thinking on all the speakers I've heard...now I'm
not sure where I stand in terms of the theory meeting actual practice.
There are plenty of lower efficiency systems that sound fricken
amazing...but I'm not sure I could claim they are always lower distortion. How
I wish I could measure every attribute of every speaker I've ever heard.

I
know PWK tries hard to differentiate between frequency response and
distortion response in the Dope from Hope, and I also know Klipsch puts
efficiency before frequency response in the compromise chain (if I remember correctly). I wonder
just how good horns measure up to other speakers if you include the
frequency response in the distortion measurements. Of course I can say
that, but I have no clue how one would go about quantifying it accurately. There has gotta be a point where
sacrifices in frequency response don't justify the increase in
efficiency...(like the Klipsch CF-4?) [^o)]

[John Warren]

Well, theres a lot going on here!<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Roy-

I can only assume that the relationship you cite between efficiency and distortion is for a given horn configuration loaded using different drivers or alternatively a common driver loaded into different horn configurations. Thus, from a series of experiments, the functional relationship can be developed. This, at least in my minds eye, is not what I would consider an inherent relationship.

I consider an inherent distortion relationship the relationship between, say, excursion and distortion. As one goes up, so too, the other. In this embodiment, the system is established.

Also, when I examine Smalls relationship for electro-acoustic efficiency, its made up of linear terms (B, l, Sd, Re). The terms that account for loudspeaker distortion are non-linear (suspension compliance, axial magnetic flux anomalies and few others).

Having said all that, I do not see an "inherent" relationship between efficiency and distortion (at least that's what I was trying to get at).

jw

[ZAKO]

Link you dink... Link has been cut off from my inheritance & he,s still upset about it.... Warren will be added to my will & testament only if he learns to apply his vast knowledge to betterment of mankind.

[ZAKO]

John the anechoic chamber is still in use to cover the screems of the ears i sacrafice to the audio gods useing the K55 drivers.