bear said:
I didn't say that.
bear said:
My point is that this thread has been stolen, occupied with silly non-measuring issues by Geddes' followers. I don't want to go into detail. I have shown to be upset, right. But I'm not confused, take it for granted.
by
soongsc said:
Thanks - happy to hear that.
🙂
soongsc said:
Either way - you can simulate in CARA for tiny rooms as well but you will have to adapt some of the settings as well - or you simulate the wave guide in the size of a room (say you multiply by 10) and take the results with a down shift in frequency also by a factor of 10.
Basically what you entitle as "room modes" in my "bunch of pretty pictures" is what shows us HOM - or at least the effects of subsequent actions of "diffraction > reflection > delay > interference" taking place *inside* the horn (*not* in the room !) - its both the same thing (think of a bass horn the size of a room for example) - just other words for *slightly* different meanings (depending on the very definitions) in very different context.
😀
Of course the sound field from inside the horn will continue (to some extent) in the same way into the real room .
To put it different - what is cooked inside the horn contour is what get spilled out into the room (or open 4Pi space).
May I ask what you think about further narrowing the throat with respect to the diaphragm diameter.
Would you think your contour would allow for - say - 70% the effective throat dimension from now?
You know - I'd like to push the irregularity out of the audio band - meaning I'm looking for a push of roughly 30% upwards. One way might be to narrow the throat even further.
There will be measures to reduce mouth reflection in parallel though - will see what works best...
Michael
wxa666 said:
"If I didn't knew the Geddes claims I couldn't even understand a word of Yours. " - you said that.
In the usual english construction and understanding, "Yours" refers back the subject of the sentance which is "Geddes claims", therefore you are referring to 'my claims', of which I made none.
I think you wanted to say '...I couldn't even understand a word of your writing...'??
It is not important what others have done or said, if you don't care about HOMs why do you care where the thread has gone? And, if you have something to add to the measurement issue, then add it? But why are you addressing to me your angry responses, am I to blame for your opinion of where the thread has gone??
_-_-bear
I don't really have enough sims to make an guess about a smaller throat. But I do recall that a longer throat on the diaphragm side might improve the situation. I think this is where I will explore some more after I get the newest waveguide in and take some measurements.mige0 said:
I would also want to keep the compression section as low compression as possible. I'm not sure what kind of tweeter you have, but here is someone doing some interesting work.
http://www.ribbonspeaker.com.tw/ checkout the RT004A-D model This is probably as close to a plane wave as one can get.
Micheal, if this works, I think you have to use a different driver with a different phase plug and a smaller throat. Merely narrowing the throat area will create internal reflections...
_-_-bear
_-_-bear
Soongsc, the idea of a longer driver throat area would seem to contradict what Dr. Geddes suggests, which is a nil throat length, iirc... besides what difference is it if the throat area is part of the waveguide or part of the driver??
Btw, I think at this point the moderators might want to take this aspect of the discussion off to another thread?
_-_-bear
Btw, I think at this point the moderators might want to take this aspect of the discussion off to another thread?
_-_-bear
bear said:
Yes, a bit old fashioned grammar, isn't it. Or just faulty. I meant the words that You wrote, hence words of Yours.
Every thread in which "HOM" are mentioned some followers will swell the item of "HOM" all over the place. It's like an avalanche. But - for my understanding - it is driven by some severe misconceptions. People just admit to have no understanding but - talk. Speculating, ever citeing Geddes' here and there. Alas the originator of "HOM" and consequently soley OEM of HOM-less devices doesn't act against it with a force he has been seen to use against non-believers.
Sorry, You are not addressed above. Wouldn't You say that the topic has been drown in sillyness?
No offence!
I am not convinced a short throat is the answer. The important issue is how the wave is controlled from the diaphragm to the exit. In the waveguides that I had built, the first one had the shortest throat to diaphragm distance. The response was clearly not smooth even though CD was quit good.bear said:
bear said:
I don't think this is exactly at the point.
One could quite perfectly attach a OS wave guide to a loooong duct and it would work even better *if* we would not account to the resonating frequencies of the duct (transmission line).
The improvement we could expect is that the wave front of the compression driver gets smoothed out when travelling along the duct as seen in
fig 4.
(real world / non flat wave front compression drivers assumed here)
I not propose that compression driver > pipe > horn set-up for "normal" operation, mid you – its just to show that there *are* benefits as well – not only disadvantages.
In the context of soongsc's contour – it comes down to the distance of the pitch to the membrane IMO.
If you can keep that distance around the throat cross dimension – we should be fine.
"besides what difference is it if the throat area is part of the waveguide or part of the driver??"
I agree – no difference to my taste!
Michael
To get top octave constant directivity, it's certainly true that you'd want as short a throat as possible. There is another dimension, though, in that the longer pathlength enabled by a longer throat lowers the frequency to which the device can control directivity- which can mean less ripple near the cutoff, and a little less demand on the driver in that same range.
One would expect a little more top octave SPL at the cost of a little more directionality, from the throat flare in a throated driver. The suppression of HOMs in the throat may be improved with a longer length of foam, but that's speculation.
A couple of points here. First a compression driver is not a point source so Michaels analysis does not apply. Second there are so many interrelated aspects of what is being discussed here that "guessing" at what would happen is probably not a good idea. I would say that in general the throat should be shorter rather than longer and it should be made to match the waveguide and not some prescribed angle (which is done for manufacturing convenience).
HOMs are like the Big Foot of the audio world. A modern, mythical beast that has people all excited, but a beast that no one has has ever seen. Claims to have seen, sure. But no concrete evidence. Tho the believers trot out all sorts of shaky evidence a proof, none of it stands up to a closer look. It's fun to believe, but evidence is sorely lacking.
That doesn't stop the faithful, tho. For them there is a bigfoot behind every tree and a HOM in every horn. Lack of any solid proof or evidence only serves to make the myth grow. I'll wait for something more substantial before I believe they are real. 😉
That doesn't stop the faithful, tho. For them there is a bigfoot behind every tree and a HOM in every horn. Lack of any solid proof or evidence only serves to make the myth grow. I'll wait for something more substantial before I believe they are real. 😉
Call them HOM or whatever you like. I can hear diffraction slots, and there's a difference using throat foam (I've never gone whole-hog) with even low-diffraction devices. Minimizing the colorations we discuss as HOMs is valid.
Of course, there are smooth-profiled horns that don't hold constant directivity very well but would be expected to have very low HOMs. LeCleach for ex.
Pano
They were proven to exist, both theoretically as well as in reality. Just because you are ignorant of what's been done does not mean they don't exist.
Elephants don't exist because I haven't seen one?
You amaze me sometimes.
They were proven to exist, both theoretically as well as in reality. Just because you are ignorant of what's been done does not mean they don't exist.
Elephants don't exist because I haven't seen one?
You amaze me sometimes.
OK. I searched but found no evidence of measurements that show the existence of HOMs in horns
Show it and I'll believe it.
Elephants I've seen and smelled
Show it and I'll believe it.
Elephants I've seen and smelled
And HOMs you've heard. Proof is for the insecure who need external support for their own direct experience.
So if its not on Google it doesn't exist?
Makarski, AES - measured them at Aachen early 2000's.
Who has heard? If I hear a noise in the night and say "That's Bigfoot!!" does that mean I've heard one?
I just have not seen the evidence presented. If it's there, I'll believe it. Same with Bigfoot and UFOs.
I just have not seen the evidence presented. If it's there, I'll believe it. Same with Bigfoot and UFOs.
OK, that's a start. Got a name of the paper or a link to it? Maybe an except from it?
Pano
With your rude introduction I am not about to do your homework for you. You are wrong so now do the homework you should have done before you made your inept comments.
With your rude introduction I am not about to do your homework for you. You are wrong so now do the homework you should have done before you made your inept comments.
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