lovechild said:
These measurements do look great - a bit too good perhaps. I can never seem to get things quite that good myself - makes me wonder. In the past I have found 18-Sound to be a bit optimistic in their data sheets compared to actually measurments of their stuff.
Bottom line here is that I didn't design this waveguide, and I didn't take the measurements so I can't really say if they got it right or not. I can say that an elliptical waveguide is not as easy to do as an axisymmetric one and how its done is a big factor. I've done these kinds of designs in the past, but I have never told anyone HOW I do it, so it remains to be seen if this waveguide works as well as claimed.
I will say that it looks like it would work a lot better than about 90% of what I've seen out there.
The throat is obscured, so its hard to tell exactly whats going on there.
Giarsun said:
It is elliptical in shape and closer to the compression driver mounting interface than usual. Yes, it is not apparent from drawings or most photos.
I have not seen the horn personally, but someone whose judgement I trust has inspected it at the local 18S distributor.
I have seen an image on the net which does show up the diffraction device (for lack of a better term since it is elliptical), but that specific image does not show up in a Google image search.
Here is a thread with some discussion:
http://www.htguide.com/forum/showthread.php4?t=20386
Thank for this interesting link on Eighteen Sound horns.
Maybe this is the XT 1086 pic you saw ?
http://lscon.tripod.com/xt1086/index.album/horn?i=1
Maybe this is the XT 1086 pic you saw ?
http://lscon.tripod.com/xt1086/index.album/horn?i=1
http://lscon.tripod.com/xt1086/
Those measurements aren´t "tuned". There´s a picture of the "diffraction-slot" too.
Those measurements aren´t "tuned". There´s a picture of the "diffraction-slot" too.
Earl's Waveguides
Earl,
I'm interested in your 1" waveguides. Are they designed for a specific driver like the B&C? You mentioned before that the throat angle must match the exit angle of the driver which was 6.5 degrees on the B&C. I have some interest in BMS, Radian or TAD drivers. Do you know of any other drivers that are an exact match to your waveguide? Do you have available any polar plots, csd or response for these guides mated with your choice of driver?
Thanks,
Randy
Earl,
I'm interested in your 1" waveguides. Are they designed for a specific driver like the B&C? You mentioned before that the throat angle must match the exit angle of the driver which was 6.5 degrees on the B&C. I have some interest in BMS, Radian or TAD drivers. Do you know of any other drivers that are an exact match to your waveguide? Do you have available any polar plots, csd or response for these guides mated with your choice of driver?
Thanks,
Randy
The XT1086 employs a diffraction device at the throat, full stop. It is a weird elyptical device and potentially a lot cleaner in execution than something like a manta-ray but I felt a little let down when I drove 80kM in traffic one day to investigate after all the hype.
As to how benign the diffraction would be (they apply liberal "FEA" to their marketing literature, much akin to JBL) I have no Idea, but I decided to CNC-turn an OS waveguide and didn't really miss the XT (is cheaper though and excellent for the money compared to many competing products).
As to how benign the diffraction would be (they apply liberal "FEA" to their marketing literature, much akin to JBL) I have no Idea, but I decided to CNC-turn an OS waveguide and didn't really miss the XT (is cheaper though and excellent for the money compared to many competing products).
lovechild said:
I've been wondering the same thing myself for some time. What I've ended up using for my application (mated to a 12) is this: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-312 In order to use mine with a bolt on B&C DE200 I've cut off the screw on part and attached a couple rings of 1/4" masonite on the back to mount the driver on. The driver exit butts right up to the entrance of the horn, but the entrance is a little big. Here are some pics of the back:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
and the entrance:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I've taken some measurements and it does show some odd behavior above 12k not present with the same driver on other horns, but I don't know the exact origins of this- I'll be experimenting in the next few weeks to see if I can narrow down the source. Also, I lopped off 1.5 inches from one edge to cut that much off of the center to center spacing with the 12:
An externally hosted image should be here but it was not working when we last tested it.
As far as I can see, this waveguide seems to be about the best option for a DIYer who can't fork out $500 for a pair of OS waveguides or who doesn't have the machinery or skills to make one. And at the current price of $8.88, one can afford to get a few spares to mess around with!
I don't have access to my previous measurements right now, but I'll be taking more soon and I'll try to get them up here everyone. What I can tell you now is that below 10k, the polar behavior is as such: at about 1.5k it has a 90 deg BW, below that it loses control. From 2-3k there is the typical slight dip in the BW to about 60 deg, at 3k it is back to about 90 degrees and from there up to 10k it is smoothly decreasing to about 60 degrees. It really does look similar to the OS waveguide, except that the directivity generally increases slightly as you go up in frequency, meaning the system off-axis responses are a straight downward slope instead of a downward slope that levels off above 1.5k. The FR in general below 10k doesn't have any nasty stuff- I've been able to get where I want to go with about 4 bands of EQ. I don't think you'd want to try that passively though.
Dr. Geddes, do you have any comments on this particular horn?
Also, I'm curious what you have to say about two (not including side of the box) potential sources of diffraction shown in my pictures: the slight mismatch from the exit of the drive to the entrance of the horn and where the bottom of the horn is cutoff resulting in a slight bump at the top of the 12. Either way, when I start taking measurements in the near future I'll be putting clay in to these places to see if it makes any difference.
Another question- if enough people are interested, is there any way to get the OS waveguides produced cheaper? Perhaps something along the lines of making one mold for them and using it to produce many fiberglass replicas? I've tried to do something like this myself by stacking progressively smaller circles of wood on top of each other and then using bondo to smooth it out and a template to try to get the contour right but I don't have the skills or tools to make it symmetric enough.
gedlee said:
Dr Geddes,
Though your waveguides cost more, if I am not mistaken, they provide coverage down to 900hz, correct? The 18 Sound doesn't go that low, due to it's smaller size.
In my experience, commercial waveguides are improving, but they're still not optimum for this application. Custom waveguides are still the way to go (for now.)
:: PB ::
JoshK said:
I might be interested in joining in a group buy. Even though I know how to make my own, it's a serious p.i.t.a.
No joke, I've spent DAAAAAAYS making a single mold.
I've been using the same oblate spheroidal waveguide profile for everything, simply because I'm too lazy to make a new mold. I wrote a guide on how to do it, and posted it over on htguide.
The one that I'm using is 72 degrees vertical by 108 horizontal. (Which averages to 90 degrees overall.)
jzagaja said:
Please don't start a flame war over pricing
Seriously, there is exactly ONE person selling these, and I'm sure he has better things to do than build one-off waveguides.
If you don't like the price, go get a DDS or 18 Sound. As noted in this thread, they are NOT optimum. Close, but not quite there.
Keep in mind that the demand for tractrix horns is 10x as high as OS waveguides. OS is a seriously under-utilized curve.
jzagaja said:
Rybaudio said:
For the money that waveguide looks pretty good.
I would judge the mismatch of slope at the throat to be the worst offender regarding diffraction.
I should mention that at $250 I include an exactly matched foam plug and a driver mounting plate. These are the same waveguides as used in the Summa. They are a perfect match for the B&C 1" drivers.
On the LF capability - please understand that the concept of LF loading in a waveguide is a direct result of Horn Theory and does not occur in Waveguide theory - at least not in the simple form found in waveguide theory. Below some frequency the drive/waveguide combination does drop like a stone, but this is more related to the driver than the waveguide. The size of the waveguide does not really affect the LF loading, its the coverage angle and throat size that determine LF loading. Size is a dominate factor in pattern control and edge diffraction. A smaller device has more mouth problems and less LF pattern control. This is exactly why I said that I did not trust the data for the 18 sound waveguide as it looks flawless at the lower end where it should have problems due to its size.
I can get the price of the waveguides down in volume, but the foam plugs will always be expensive because the raw material is so expensive (I use one block not layers - much more expensive). The mounting plates cost about $25. So in volume we might be looking at $150, but below that is not likely to happen. These are not injection molded parts - thats a huge difference in cost.
gedlee said:
Thanks alot for the replies Earl, this is really getting interesting! Considering the total cost of a 1"/15" high efficency speaker project, $300 for a set of nice, ready to use OS waveguides is not dramaticly expensive at all - at least in my eyes. Maybe a regular 'Groupbuy', as it's very common in the electronics section, could generate enought interest to get in the $150 range.
And a Groupbuy of B&C 1" drivers could help reduce the total cost even more...
Would that have to be the 1"/15" waveguide or would a 1"/12" waveguide be an option? IMHO, the 1"/12" version could be a bit easier to handle, in terms of size, but also finding a selection of woofers that perform well enought in the midrange.
cheers,
martin
As for the available alternatives, it would really be interesting to see some well documented measurements on these.
He's the one for the XT1086, from the same place where the throat images comes from, but nothing is said about angles, conditions etc.
and the throat:
Well, looks like there is something going on, but I'm not experienced enought to judge it from this one shot.
@ Rybaudio
Thanks for pointing to the dayton waveguides, I'm really keen to see your measurments! I had actually seen these at PE, but forgot about them, as they are not available in europe and with shipping and import fees they come out more expensive than the XT1086. On the other side, I have good experience with the (also very cheap) Monacor waveguide for dome tweeters, so I think cheap not neccessarily means bad. Finding the right driver might be a problem though.
He's the one for the XT1086, from the same place where the throat images comes from, but nothing is said about angles, conditions etc.
An externally hosted image should be here but it was not working when we last tested it.
and the throat:
An externally hosted image should be here but it was not working when we last tested it.
Well, looks like there is something going on, but I'm not experienced enought to judge it from this one shot.
@ Rybaudio
Thanks for pointing to the dayton waveguides, I'm really keen to see your measurments! I had actually seen these at PE, but forgot about them, as they are not available in europe and with shipping and import fees they come out more expensive than the XT1086. On the other side, I have good experience with the (also very cheap) Monacor waveguide for dome tweeters, so I think cheap not neccessarily means bad. Finding the right driver might be a problem though.