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  »  New  The Active High Frequency Solution - AHFS..  Small problems with the camera lens can be mistaken for...  Playback Listening  Forum     5  38389  02-06-2008
04-27-2006 Post does not mapped to Knowledge Tree
paul williams


UK
Posts 7
Joined on 04-26-2006

Post #: 1
Post ID: 2340
Reply to: 2340
How to give bats a headache.
I've never understood the continual need to get equipment to have ever wider frequency response, to me (but then I'm a complete technonumpty) this just seems to be an exercise in chasing numbers to impress those that are impressed by spec sheets.  At a recent local exhibition focusing on the recording industry, one of the booths was showing the relative hearing abilities of various animals and humans (as they age). It also had a signal generator with digital display and headphones so you measure your own hearing abilities.  As I was there with my two sons (8 & 5) we gave it a go.

Me (50 this year) left ear 12kHz, right 12.45kHz (OK so if I really ramp up the volume 15kHz)
My 8 year old son left 19.30khz, right 19.25kHz
My 5 year old son left 19.40kHz, right - got bored and left

So what really is the point in striving for ever higher frequency extremes?  I would never spend the money on say, Townsend super tweeters, so I'll never really know if they have any benefit, even though some say they can transform speaker performance.  But how about a pair of these Golden Sounds Ultra tweeters to sit on top of those super tweeters;

"These remarkable speakers, sold in pairs, operate at extremely high frequencies -- much higher than the audio band - actually in the microwave band, above 1 Gigahertz (GHz). The Ultra Tweeters are connected to the output terminals of existing speakers with speaker cables - preferably light, flexible ones - since the Ultra Tweeters themselves are quite light. Ultra Tweeter principle of operation is very unconventional. They don't generate sound in the audio band, or even in the 20-100 KHz band like super-tweeters, but function in the Gigahertz frequency band (normally used for satellite and microwave communications). Ultra Tweeters organize and improve the energy flow in signal conductors as well as the internal wirings of speaker drivers, making the audio system perform more efficiently and synergistically."

Now I have to admit that even though I'm sonically challenge in the upper frequencies, I intensely dislike metal dome tweeters (fingernails on blackboard) find the sonic signature of most audio equipment to be too prominent in the higher registers and "Elton John - one night only (the greatest hits) concert" to be the most badly played live concert ever perpetrated by so called professional musicians - and they actually recorded and issued it (Mercury 548 334 -2) but that's off topic.  The thing is, if I'm loosing my ability to hear higher frequencies, which is the natural state of affairs, why am I so intolerant of most equipment.  Thinking back over all the equipment I've owned in the last thirty years, as those specs have gotten better I've been less and less satisfied with what I've heard - especially speakers & to a lesser extent phono cartridges (I won't go on about CD's the format which has contributed to the 'general' publics inability to physically handle recoded media with any care and consideration).  So if any of you more technically savvy individuals can explain the merit of producing really wide band equipment - I'm all ears.  The only reason I could come up with was, that if you push the performance boundaries beyond the normal usable requirements then that usable portion becomes more controlled or manageable.

PW

PS. I've not enjoyed drifting around a website so much in ages.
04-27-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,495
Joined on 05-28-2004

Post #: 2
Post ID: 2341
Reply to: 2340
I’m pro full-range but against the wrong tweeters.

I’m very much pro wider frequency response, as wide as possible. However, using juts a trim “wider frequency response” different people mean different thing perhaps…

I have written at this site quite a few articles stating the foolishness and luck of usefulness of many super tweeters, and particularly in that way how they used by fools. However, the term: “wider frequency response” has nothing to do with tweeters. In fact the super tweeters themselves are not as bad as the use of the wrong tweeters in a wrong way….

Well, way I would advocate the “wider frequency response” or something that I usually call the “full range”? Because the “full range” sets the reference to the sonic events. The extremes lowest and highest frequencies create the environmental “space” where the musical even unfold. Not to mention that the LF have a lot of modulate contribution to the auditable spectra.

How all of this relates to the fact that some people do not hear to low or to high. It is completely irrelevant.  When I am talking about the full range capable playback or equipment I am talking about aptitude and about what the playback or equipment dose while it handles the full range. I mean the potential and the functional capacity to operate in those extreme conditions of the full range while holding it’s sonic integrity and doing other things properly.

It has nothing to do with sound that we hear in listening rooms, well as least in that way how you portray it. The fact that you, I or somebody else hears no more then 12, 15 or 20 kilocycles is completely irrelevant. The only why we mistakably think about the HF amount of dB at specific frequencies is because we have a linear mathematics and machinery that calibrate for us HF. In fact those linear measurement concepts are completely not applicable at HF. there are many reasons why: starting form HF amplitude and phase resolution and ending with 8th order low-path filter that our ears have build-in at 15khz (or something like this). Yes, we do not “register” the 15Khz from the generator but we easily recognize tweeters distortion at 40khz, or PP amps phase anomalies at 25khz, or close loops HF alterations. The most important is that we very easy and with very high resolution hear those 15khz or 20khz or 25khz at certain amount of dB below the mathematical lineal zero.

For instance in my listening room I have 0dB at 10Khz. However, at 20Khz if I have minus 9 3/4 db then it sounds fine to me but the minus 9 2/4 I recognize is too bright. Furthermore, I clearly hear that a transformer with upper limit of 88Khz is less HF transparent then a transformer with 125Khz upper limit. So, it is not juts the linear numbers but rather the “linearity in decaying parabola” plus … many other things that playback dose… while it handles those numbers.

Generally, I’m very much form “full range” but of course the real full range of the reproduced realty (or the wider frequency response) is not juts adding those crappy tweeters to a playback systems…

Rgs,
Romy the caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-28-2006 Post does not mapped to Knowledge Tree
Gregm
Greece
Posts 91
Joined on 02-16-2005

Post #: 3
Post ID: 2342
Reply to: 2341
It's nice to dream about full range capability... but the ultra-super tweet ain't it
Two basic premises:
A) The concept we all operate on is: a chain of components connected between one another that pick up info from a medium, transform the info into ac and amplify that info; then, we attach speakers to the last of these components {amplifier(s)} to LISTEN to the result.
B) The most important frequency range for music is often defined as 100Hz-10kHz (I would prefer 50-10kHz), where the most fundamental musical content (+some harmonics) resides. This is well within our hearing capability -- even sine wave hearing capability.

Now, in order to reproduce these 50/100-10kHz IMPECCABLY, the system MUST be capable of much more: as Romy notes, a tweet hitting upper limit say at 40kHz can have anomalies a 1-2 octaves lower -- i.e. 20-10kHz -- and we can hear those, basically as anomalies compared to the rest of the music we're listening to. 
By the same token, a good tweet reaching 100kHz will not, in all probability, interfere annoyingly with the basic musical content...

So, it's not a matter of whether our ears catch a 15kHz sine wave alone -- it's how well we reproduce what our ears Do hear + perceive, as a whole...

Of course, all this applies IF the system as a whole is capable of undistorted reproduction -- which is a tall order...

Unfortunately adding another tweeter or two to each of the speakers won't make the result any better -- just different. It won't correct that narrow bandwidth tranny; nor that marvellous 2nd order passive crossover we have at 350Hz/ 1W that slips to third order, at 460Hz, at 10W, etc...

Finally, some practical points:
1) it is VERY difficult to ALIGN a drive unit operating over say 20kHz with the rest of the speaker. Think about it: the wavelength is less than 2cm -- if your acoustic centres are off by <1cm you;re already heavily out of phase... I love the idea of bringing 1MHz in phase!
2) While you're at it, you might check out the FR and the power response vs the rest of the spkr
3) Similarly, what about the filtering? Is it 1st order, 2nd, 65 order? Bessel, Butterworth, L/R?
4) Adding another component to the spkr changes the circuit the amplifier sees -- there we go again with the output trannies (tube) or the power capability (ss), etc, OR look for another amp...
5) For the rich, I thoroughly recommend Murata - the pro models. For a motley 3-4k each, they will play nicely from ~15kHz -~45kHz and reach their upper res ~120kHz.
6) I tried the Murata above, courtesy of friends. I won't go into the complication involved in trying to get this thing to work -more or less correctly. Suffice it to say that this was an excercise with radio techs involved. But it sounded good -- as long as you didn't touch it fm where the techs placed it.
Cheers
04-28-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,495
Joined on 05-28-2004

Post #: 4
Post ID: 2343
Reply to: 2342
Evan if we do “might” need them….
Gregm, you see, the Murata tweeters have no sensitively and vary narrow diagram and that makes those type of the drivers unusable, even if to accept then hypothetically. With the resonant frequency over 100Khz that those type of the tweeters beg to be used on transition slope, way up at the range. If they were 110dB then it would be fun to place then at ultra HF crossover point and let them arrive to the auditable rage at minus 8-9db. (My T350 sits at 50 Khz -60Khz I believe…) Some driver work remarkably on the slope…. However with 90dB sensitively what would you do with this driver? The 90dB! The electrostatics have 90dB and than are good only for producing sounds that attract transvestite mosquitos! The last time I head the Mahler Second on electrostats I thought it was Haydn #88… It would be fun to try building an array of a dozen HF high sensitively traducers but with huge amount to phase integration problems it would be virtually not accomplishable…. And it it would be done then it would be so tweakt that the “as is” result would rather be more pleasing….

Rgs,
The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-28-2006 Post does not mapped to Knowledge Tree
Gregm
Greece
Posts 91
Joined on 02-16-2005

Post #: 5
Post ID: 2344
Reply to: 2343
Ooops, please take my Murata comments with a grain of salt!
"...what would you do with this driver." 
Please don't anyone take my silly joke at face value. It's fine for what it is (they sell to radio stations & the like) -- bad for what it isn't (indespensable atop yr spkr; improvement for yr cell phone reception, etc)

"the Murata tweeters have no sensitively"
true, but then the spkrs system itself was 88db sine at ~18kHz. So, we just made it with +~10db boost

"it would be fun to place then at ultra HF crossover point" Yup, finally it was 1st order @ s/thing like 45-50kHz..


"The last time I head the Mahler Second on electrostats I thought it was Haydn #88…" 
Smile !
04-28-2006 Post does not mapped to Knowledge Tree
paul williams


UK
Posts 7
Joined on 04-26-2006

Post #: 6
Post ID: 2345
Reply to: 2344
OK so I need what I can't explicitly hear

OK, you would seem to be saying in a more technical presentation basically what I thought (in very, very simplistic terms) the explanation would be.  So to get this straight in my head;

For instance if we seek to record a single note of a plucked guitar string say ‘A’ above  ‘middle C’.  This has a fundamental (don’t know if that’s the right term) frequency of 440Hz and will have harmonics at every octave ………27.5, 55, 110, 220, 440, 880, 1760, 3520….. 9 octaves below takes to just under 1Hz and 6 octaves above to 26kHz.  At the same time the guitar itself will resonate and reproduce both this fundamental and ‘overtones’ also at 440x2, x4, x6……and at intervals below.  It is this non-fundamental element and their relative ‘strengths’ in the overall sound, that provide the timbre and pitch signatures that identify the individual elements of the note.  No two guitars would have the same signature, therefore sound different, as would ‘A’ played on different instruments, thus the ability to hear different parts of an orchestra, even when playing the same note.  If we throw Chords into the mix, we end up with the above but add frequency ratios (and their interactions) into the mix; Major chords with a ratio of 4:5:6, Minors 10:12:15 and Diminished with 160:192:231.

OK so I accept the need to be able to go both above and below 20 to 20kHz to ensure these vital elements are present, to give better representation of the truth, but does this mean that my treble intolerance to most modern hi-fi equipment is indicative that I don’t like the truth as presented or is the sonic signature portrayed inaccurate and this is the reason for my discomfort.  If the latter then I just need to get better equipment, if the former........

PW

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  »  New  The Active High Frequency Solution - AHFS..  Small problems with the camera lens can be mistaken for...  Playback Listening  Forum     5  38389  02-06-2008
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