Has anyone here tried this driver with a front horn loading? I'm looking for something to start off with rather simply, to play around with some profiles. Thought the Oris horns were rather nice when I heard them last, and wa thinking this might be a nice driver to try my hand with for not too much dough. I'm open to other drivers as well, especially if I'm looking at cheaper drivers 🙂 Just getting my horn feet wet now, and I figure the best way to do that is with an inexpensive project. That, and I want to try out some ideas for fabrication.
Can't see any reason why not. Don't forget the standard Fostex FE206E or FE207E either though. First stop if you haven't been there already: http://www.quarter-wave.com/Horns/Front_Horn.pdf for background reading, then get Martin's worksheet.
Cheers
Scott
Cheers
Scott
Works very well!
I don't know why people don't seem to use it in Oris-type of front horn, cause the driver's drawbacks (HF harshness) makes it ideal for such a use, as the front horn will bump up mids a lot more than the HF peaks, thus balancing the sound a bit. You probably will want a ST as well.
I tried the 168 in a 250Hz horn and was amazed by the results. I also made a baby oris for a FE108 with really good results too!
Now I'M trying to find a platic shop who can make the horns for the DIY market.
All in all, it's a nice way to use these drivers and you get awesome SPL as a bonus (down side, you need a bass cabinet that will match SPL...)
Good luck with your project.
Robert
By the way, you will need a small enclosure behind the driver, and it's a good idea to make it reflex, tuned at (or just below) the horn's LF cut-off to restrict cone movement.
I fried a 108 while running it full-range, so it also needs to be high-passed.
www.gemmeaudio.com
I don't know why people don't seem to use it in Oris-type of front horn, cause the driver's drawbacks (HF harshness) makes it ideal for such a use, as the front horn will bump up mids a lot more than the HF peaks, thus balancing the sound a bit. You probably will want a ST as well.
I tried the 168 in a 250Hz horn and was amazed by the results. I also made a baby oris for a FE108 with really good results too!
Now I'M trying to find a platic shop who can make the horns for the DIY market.
All in all, it's a nice way to use these drivers and you get awesome SPL as a bonus (down side, you need a bass cabinet that will match SPL...)
Good luck with your project.
Robert
By the way, you will need a small enclosure behind the driver, and it's a good idea to make it reflex, tuned at (or just below) the horn's LF cut-off to restrict cone movement.
I fried a 108 while running it full-range, so it also needs to be high-passed.
www.gemmeaudio.com
I'm rather computer un-savvy, so I've been unable to run any of the spreadsheet horn calculation applets. I don't have Excel, as I use Macintosh, and the MSOffice suite is hugely expensive. I can't seem to find it for sale by itself. I'm wondering if someone might be able to model this horn for me. I'm building a machine to fabricate the hard bits, as thats my specialty. I just need something better than my intuition to guide me in laying out the curves.
I'm no expert on front loaded horns -I've never had cause to model one before. However, after playing around in MathCad for a few minutes,this doesn't seem to be too bad, as far as FLHs go, for a first quick pass. It uses some of the dimensions Martin refers to in his FLH article, with modifications to the size of the rear chamber. Data entered is shown below, frequency response in the next post:
Attachments
And here's the predicted response. Remember in these models, the driver is mounted with the rear venting into a sealed box, in this case with a front and rear area equal to 4 times the driver surface area, and 4" deep. It fires forward into a much smaller front chamber, with front and rear areas equal to 1.5 times the driver's surface area, and 2" deep. The horn is attached to the front of this. It's throat area is equal to the surface area of the driver. It is 21.5" long, and its mouth is equal to 20.2 times the surface area of the driver.
Well, it's a start anyway!
Best
Scott
Well, it's a start anyway!
Best
Scott
Attachments
Thanks for running that for me, Scottmoose. 🙂 Looks pretty good, actually, but it looks like you used the data for the 208. 😀 The top (phase) plot is interesting, though. Now, assuming the 208, how do I go about creating the physical profile? Do I simply plug in the distance from the throat, etc. to the exponential formulae? My intent is to plot a template for a cutting tool to follow, so these can be turned from a suitable material, or to make a multi sectioned bowl, with the profile bent or cut into the sections. Ultimately, I'd like my large CNC router to do this automatically.
It is the data for the 168 -don't worry. The reference to the 208 is due to that driver being the default that's loaded into the worksheet. I changed the parameters, but I didn't re-name the driver in the title part up-top. Sorry for any confusion!
The get the physical profile, you'll simply need to plug the throat, mouth and length shown into the exponential formulae, as you mentioned above. The rear and front chambers are easy enough of course. I've no idea how you'd go about building one, apart from with great difficulty, but your above suggestions sound about right!
Best
Scott
The get the physical profile, you'll simply need to plug the throat, mouth and length shown into the exponential formulae, as you mentioned above. The rear and front chambers are easy enough of course. I've no idea how you'd go about building one, apart from with great difficulty, but your above suggestions sound about right!
Best
Scott
What did you set for the flare frequency? I was going to try running either 250 or 150hz. Also, I cant get the Sd in your example to jibe with the published specs: Moving piston is given as 60mm. The Sd listed in the factory specs states .0113m3, and I can acheive that result using the published number for "a", which I'm assuming is the piston radius. Is the factory Sd spec the one I should be using when creating the physical model?
Sd in Martin King's back-loaded or front loaded horn models is irrelevant. Hense the fact that there isn't anything entered by myself in that parameter; it's a bit confusing to begin with I know, but if you go to www.quarter-wave.com and read his articles on the design of horns, it will become clearer.
Here's a quote from the conclusions of his article on the design of a front loaded exponential horn:
"When sizing the front exponential horn sub-system, it is interesting to note that the driver’s size and Thiele / Small parameter do not enter into the calculations. The lower cut-off frequency fc determines the mouth cross-sectional area. The throat area and horn length are determined by the desired SPL boost above the lower cut-off frequency fc. Given two similar drivers that vary only in diameter, the same size horn
mouth would result for the same low cut-off frequency fc. The same exponential front horn could be used for similar eight inch and six inch diameter drivers."
Hope that's a help.
Best
Scott
Here's a quote from the conclusions of his article on the design of a front loaded exponential horn:
"When sizing the front exponential horn sub-system, it is interesting to note that the driver’s size and Thiele / Small parameter do not enter into the calculations. The lower cut-off frequency fc determines the mouth cross-sectional area. The throat area and horn length are determined by the desired SPL boost above the lower cut-off frequency fc. Given two similar drivers that vary only in diameter, the same size horn
mouth would result for the same low cut-off frequency fc. The same exponential front horn could be used for similar eight inch and six inch diameter drivers."
Hope that's a help.
Best
Scott
Open Offoce is an open source suite of office applications for any platform. Free and easy to use.Corvus corax said:
Link to Open Office
robertG said:
Robert, I built a front horn with the 108 with a throat size of Sd/2. Tractrix expansion tuned to 212Hz (I think that's right).
I had mixed results with this, and decieded to keep my 108 in a sealed enclosure in a wide range two way set up. If you could tell me a little bit more about your front horn with the 108 I wouild be very interested. Did you find the need for a super tweeter along with the horn? What throat size and flair did you use? If you are going to be selling horns similar to this and don't want to share your insights I understand, but I can't help but ask.
Joe
For the 108, I used an Sd just a bit larger than the area of the driver, no compression chamber, exponential, with a low cut-off around 300Hz (around 20 in. in diameter).
Needs a super-tweeter.
Test horns were made of 2in. thick hard-foam (the pink stuff) discs with different flare profiles, one on top of the other. When I reached the ideal combo, I smoothed out the inside with sandpaper.
Cheap and fun, except that I fried one 108 (no back chamber...).
I'll have another set CNC'd out of MDF discs (this time with a back chamber and high pass filter). If I'm happy, I'll have some thermo-formed to mate with my horn loaded bass cabinet and have a party!
Needs a super-tweeter.
Test horns were made of 2in. thick hard-foam (the pink stuff) discs with different flare profiles, one on top of the other. When I reached the ideal combo, I smoothed out the inside with sandpaper.
Cheap and fun, except that I fried one 108 (no back chamber...).
I'll have another set CNC'd out of MDF discs (this time with a back chamber and high pass filter). If I'm happy, I'll have some thermo-formed to mate with my horn loaded bass cabinet and have a party!
I stand corrected. Booyah! Unfortunately, I can't remember why I wanted the spreadsheet program to begin with! Probably had something to do with the Lecleach spreadsheet. Good information on your experimental horn profiling, also- thanks. I think I'll finish my automatic horn profiler NOW. I just need a router to make it work, and it will make any profile up to 48 inches deep by 72 inches wide. 🙂
Wo!
48 deep? 72 wide? As in 6 feet?
Not exactly a simple project!! I thought I was crazy...
What kind of LF cut-off are you looking at?
48 deep? 72 wide? As in 6 feet?
Not exactly a simple project!! I thought I was crazy...
What kind of LF cut-off are you looking at?
Those are simply the maximum capacities of the machine I'm building- The largest horn that could be fabricated without resorting to building in sections. I wanted to make sure I'd be able to handle larger horns if the need arose. But, if my off the cuff calculation is correct, a real world horn with about a 50hz limit or lower could be built. Good for a large woofer, even before boundary effects. But for now, I'm sticking with 36 inches or below... My 150 Hz Fe168 horn worked out to about a 27 inch diameter by 22 inches deep. I'll probably go up to 250Hz though, for the sake of overall sound. I found the Oris 150 a bit congested compared to the 250.
Martin King's Mathcad worksheets. You can get them for DIY use for $25; here's the link:
Quarter Wavelength Loudspeaker Design
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