soongsc said:
Soongsc
This is not correct. As long as the diaphragm is not modal the radiation will be CD. There is no reason that a small honeycomb diaphragm should not be rigid to above 10 kHz. The Panasonic one was.
No I don't remember the model #.
gedlee said:
http://www.acousticdev.com/cms/inde...w-4q-speaker&catid=37:uncategorized&Itemid=59
Dan Wiggins did some work with Tang Band on a transducer like this.
An externally hosted image should be here but it was not working when we last tested it.
Here's a pic.
An externally hosted image should be here but it was not working when we last tested it.
So who's going to make a waveguide for it? 😀
There's a variation of the woofer for sale at Parts Express. (not the exact same model.)
gedlee said:
Allow me to question that – not for the reason of membrane break up but for the behaviour of throats entering the wave length dimension.
The mechanismim at work - like I see it - I outlined at:
http://www.diyaudio.com/forums/showthread.php?postid=1854398#post1854398
I might be wrong, though – but would expect a trend towards non-CD behaviour from what I have seen on my measurements and simus beginning at around 4-5kHz with the 4" er.
Depending on flare of course.
Definitely would like to see polars as soon something is built.
Hasn't this been the Putland issue, anyway ?
Michael
Patrick Bateman said:
The waveguide for a 4" speaker will get pretty big. And I suspect that it won't go all the way to 10 kHz as a single unit. This poses a problem as now you need something above this in the frequency range.
I would tend to work the other way. Start with the highest frequency that you want and work a waveguide to that. See how far down this will go and then you know what the system just below that has to do.
Going this way however dictates a 1" or smaller throat, without a compression driver its going to be hard to get the headroom that I look for. Thats how I ended up where I am. Any other approach, seems to me to end up with a three way system above 200 Hz. and that spells trouble with waveguides.
Perhaps a Hi-Vi planar?
Unfortunately it's no good below 3khz. Could be an interesting candidate for a small cheap 2-way with a waveguide tho.
Unfortunately it's no good below 3khz. Could be an interesting candidate for a small cheap 2-way with a waveguide tho.
My friend is going to make waveguides with CNC machine and negative mould. We can supply some to the group. Any suggestions appreciated.
John
Interesting reading about Acoustic Development. Looks like a bunch of Ex-Tymphany guys got together. Wonder how well this will work out for them. Looks more like an importing company for Chinese speakers than anything else.
Interesting reading about Acoustic Development. Looks like a bunch of Ex-Tymphany guys got together. Wonder how well this will work out for them. Looks more like an importing company for Chinese speakers than anything else.
gedlee said:
Hardly. Dan Wiggins is one of the most talented driver designers around and he holds several motor patents. His former company, Seattle based Adire Audio, went broke when he tried to set up a manufacturing plant in Chile and his 'partners' stole all his money. He learned his lesson and now he's a freelance consultant and ADI is his new company. If he got a contract to build drivers, he'd of course source them from Asia, but he'd be doing the design work.
Patrick Bateman said:
Absolutely. The thing that's a bummer is that I'll bet a number of people have bought the XT1086 and assumed it's a substitute for an OS waveguide, based on how the mouth looks. But the throat diverges from OS by quite a bit.
This is my elliptical OS waveguide mold. Sorry I don't have a better pic - this is before I applied glass and bondo. It looks a lot better than this now.
Here's a mold made from an XT1086. Note that the throat is muuuuuch longer than the OS waveguide, even though their coverage angles are comparable. The OS is 108x72, the XT1086 is 80x60.
I noticed Faital is selling a couple of "tractrix horns" which look very VERY similar to the XT1086. I wonder if it's the same designer? That sure doesn't look like a tractrix curve...
Note the baffle and the ribs on the waveguide are reminiscent of the XT1086.
$49.95 and $69.95, respectively.
Hello all
I am the one who wrote the waveguide article that appears on Rod Elliots site, and generally go by the moniker rcw.
When that article was written I discussed the general content and assumed knowledge and skill level of the target audience with Rod.
We agreed that what had become known as the"waveguide"was the latest thing that had seemed to hit audio, and naturally diy people were curious about whether it was just all hype or that such devices had some technical merit, and if they did have some validity how you would go about designing and constructing one.
Knowing that acoustics is considered a notoriously difficult subject, the only background I personally have in it, ( having taken an Msc. in geophysics), is in the field of seismology, in which the "acoustic approximation" is widely used for seismic sources that approximate point sources.
So in writing the article the intension was to pitch it at the audio enthusiast with practical bent who perhaps has technical qualifications up to certified engineer level, this being the general audience for Rods site.
This being so all of the formula in the article are of the practical engineering sort that allow you to approximately figure how the gadget will look and how big it might be, with the reference material comprehensively documented, so as to assist any brave soul who should care to delve into the theoretical matters mentioned, and to make the point that the article is rigourous and not derived from anybodies ouja board or as dictated by noises in their head, as is unfortunately so common in audio judging by the nonsence you come accross.
rcw
I am the one who wrote the waveguide article that appears on Rod Elliots site, and generally go by the moniker rcw.
When that article was written I discussed the general content and assumed knowledge and skill level of the target audience with Rod.
We agreed that what had become known as the"waveguide"was the latest thing that had seemed to hit audio, and naturally diy people were curious about whether it was just all hype or that such devices had some technical merit, and if they did have some validity how you would go about designing and constructing one.
Knowing that acoustics is considered a notoriously difficult subject, the only background I personally have in it, ( having taken an Msc. in geophysics), is in the field of seismology, in which the "acoustic approximation" is widely used for seismic sources that approximate point sources.
So in writing the article the intension was to pitch it at the audio enthusiast with practical bent who perhaps has technical qualifications up to certified engineer level, this being the general audience for Rods site.
This being so all of the formula in the article are of the practical engineering sort that allow you to approximately figure how the gadget will look and how big it might be, with the reference material comprehensively documented, so as to assist any brave soul who should care to delve into the theoretical matters mentioned, and to make the point that the article is rigourous and not derived from anybodies ouja board or as dictated by noises in their head, as is unfortunately so common in audio judging by the nonsence you come accross.
rcw
catapult said:
I've know Dan for years and the story about his manufacturing plant is not the same story that you get from the other side. Last that I saw him he was not working on Audio, more underwater stuff. He did not have the funds to start a new company and I noted that he is not the CEO. There are two of four people at that company that are recently departed from Tymphany - two of many.
I don't think that anything that I said was wrong.
I don't know the details of Dan's company but he used that company name when he was the only person working there. The others came later. Bill Gates wasn't the CEO of Microsoft either the last few years he actively worked there (chief software architect or some such nonsense) but everybody know who the boss was. 😉
rcw said:
HERE!!!! You must be kidding!? There is never anything posted at DIY that is not absolute fact - just ask the writer.
I didn't get a chance to read the article, could your give us a review?
I am sure that if you and I perused the net indipendantly and compiled a list of nonsence we found there, and then compared them Earl, they would be remarkably similar.
The formula outlined are called “Keeles asymptotic model” by Hendrickson and Ureda in the Manta ray horn reference, I have just converted them from imperial to metric units.
Johansen in his paper shows that they are fairly accurate for rectangular mouth horns as originally published, but need to be modified somewhat for axis symetry devices.
There is also an effect due to the flare shape near the mouth;- basically if you make a mouth section with a larger flare than the conical inner section the width for the same cut off can be reduced by 1.12, and if the total device consists of three conical sections the factor is around 1.24, the measurements I have made showing these hold up reasonably well if circular arcs replace the outer section in the first case, or constitute the whole device in the second.
As I have previously stated these are simple approximate formula that can give you a good idea of the form of a working device with a bit of calculator bashing, and measurements of actual devices and systems using them show that they are perfectly adequate for most practical purposes.
As far as directivity goes remember that two in phase sources 6db. down at the same frequencty sum flat and if you take one device away the result is 6db. Down, i.e. if one device has no output at all the maximum discrepancy is 6db. How many speaker builders can honestly say that about their creations?
rcw
The formula outlined are called “Keeles asymptotic model” by Hendrickson and Ureda in the Manta ray horn reference, I have just converted them from imperial to metric units.
Johansen in his paper shows that they are fairly accurate for rectangular mouth horns as originally published, but need to be modified somewhat for axis symetry devices.
There is also an effect due to the flare shape near the mouth;- basically if you make a mouth section with a larger flare than the conical inner section the width for the same cut off can be reduced by 1.12, and if the total device consists of three conical sections the factor is around 1.24, the measurements I have made showing these hold up reasonably well if circular arcs replace the outer section in the first case, or constitute the whole device in the second.
As I have previously stated these are simple approximate formula that can give you a good idea of the form of a working device with a bit of calculator bashing, and measurements of actual devices and systems using them show that they are perfectly adequate for most practical purposes.
As far as directivity goes remember that two in phase sources 6db. down at the same frequencty sum flat and if you take one device away the result is 6db. Down, i.e. if one device has no output at all the maximum discrepancy is 6db. How many speaker builders can honestly say that about their creations?
rcw
rcw said:
Good point.
My equations are even simpler, I think. If the waveguide angle is 45 degrees then the response will be down 6 dB at 45 degrees. Doesn't get much simpler than that.
One thing that I always find curious is that everybody talks about all the audio nonsense there is out there, but when you come up with something new, its considered nonsense. All the old stuff is nonsense and all the new stuff is too. Go figure!?
gedlee said:
Tom Danley made an offhand comment that BMS compression drivers are better suited to conical horns than traditional compression drivers. He used B&C when he was at Sound Physics Labs, and now uses BMS mostly, with a bit of Faital on the newer gear.
Maybe it's because of the diaphragm shape, which is basically a flat ring?
Then again, the phase plug on the BMS is very simple, in stark contrast to what you see on JBL and B&C.
Patrick Bateman said:
That tends to make the BMS cheaper. But having used their products I was not very happy withn them.
gedlee said:
What was wrong?
(..I've noticed that they have some excellent characteristics, but a few prob.s - like reduced dispersion at very high freq.s.)
gedlee said:
If you'd like to evaluate a BMS 4540ND, let me know. It is truly a unique compression driver. It is the only one I am aware of with clean output above 20khz that won't break the bank.
I have a pair of B&C compression drivers here, but I prefer the BMS due to it's extended response. The B&C will play lower, but we're often restricted at the low end by the size of the waveguide.
For instance, the Nathan has a crossover of 1.4khz which is well with the operating range of the BMS, and it plays higher than the B&C.
I'd be happy to throw them in a box and send them your way, if you'd like to try them out.