I want to try building a back loaded horn based on the Fostex 206e. I do however have some size constraints. I was wondering if anybody knows of a design that isn't more than about 14" wide and maybe 15" deep. Height isn't an issue. If those requirements can't be met in an already designed speaker, can I modify an existing speaker, like the Fostex recommended one, to match those dimensions? What would be the problems if I did that? Thanks.
I don't know about designs which fit your criteria, but you could re-arrange the fostex cabinet to suit.
You need to draw the fostex horn out in a straight line and then re fold it to fit your floorspace.
The important factors are keeping the horn expansion and cross sectional area's as near as possible to their design, as well as the initial chamber volume.
In order to fit your criteria, there is little option but to go upwards (see the Hedlund horn).
Should be a fairly straightforward re design with which I could help you, if you like.
You need to draw the fostex horn out in a straight line and then re fold it to fit your floorspace.
The important factors are keeping the horn expansion and cross sectional area's as near as possible to their design, as well as the initial chamber volume.
In order to fit your criteria, there is little option but to go upwards (see the Hedlund horn).
Should be a fairly straightforward re design with which I could help you, if you like.
In my opinion, there is no such thing as a small back loaded horn enclosure that is not corner loaded to produce decent bass frequencies. This is independent of driver size and really only a function of required mouth area. Even corner loading has to be handled carefully to achieve the right SPL balance.
Most moderately sized back loaded horns that are intended to be placed out in the room, or even close to a rear wall, are behaving as transmission lines at low frequencies and transition to horn loading at frequencies between say 200 and 400 Hz. This transition frequency is also dependent on the horn's mouth size.
There is nothing wrong with this approach but the designer needs to recognize what is happening in the line to make sure it is accounted for when laying out the geometry. Almost all back loaded horn designs found on the Internet behave this way.
Most moderately sized back loaded horns that are intended to be placed out in the room, or even close to a rear wall, are behaving as transmission lines at low frequencies and transition to horn loading at frequencies between say 200 and 400 Hz. This transition frequency is also dependent on the horn's mouth size.
There is nothing wrong with this approach but the designer needs to recognize what is happening in the line to make sure it is accounted for when laying out the geometry. Almost all back loaded horn designs found on the Internet behave this way.
MJK said:
The Klien Horn being one of the few that is truly a horn.
An externally hosted image should be here but it was not working when we last tested it.
I'm working on a horn where i use the backwall & floor as the final part of a consistent horn, but to fit within the target footprint only 70-80 Hz is realistic (for FE108ES, with a goal of being able to adapt to 2 FE108ES or an FE126). Even this exceeds your width/depth by a bit (althou the width is "disguised" by a narrow front baffle).
Bob's Dalek horns are a more reasonable example of the size required (and it would need to be adapted from the 166e it uses -- different compression chamber? (althou i wouldn't be surprised, if when adaequatetly loaded, the 166 actually out-performs the 206 (especially mid-top range).
dave
PS: Bob -- got the plans. Thanx.
Thanks everybody for your responses. MJK, I agree that there are no small BLH enclosures. I guess I am just looking for the smallest I can find that has decent performance. I did find one pre-designed horn that fits my size requirements. The Lowther Bicor 200 is tiny! I am trying to find some reviews on that enclosure, but I can't find any. Has anybody heard anything about the Bicor 200? I realize that due the size it won't go as low as some larger designs. I use a subwoofer, so I really don't need it to go too low, maybe just 70-80hz. If anybody can give me a link to some more info on the bicor 200 I would appreciate it. BobH - If this lowther design ends up not working out, I just might take you up on the offer to help me re-design the fostex enclosure. Thanks again.
I have been reading this thread with interest, since I am working on a similar challenge. I am designing a BLH around an FE87E or an FE83. I am generally against sub woofers and stick with full range, single drivers in an effort to avoid XOs.
I also want a relatively compact design, which I concluded would necessitate a rear firing corner loaded design. That Dalek design looks like it might behave like a true horn, and very stylish to boot (Martin? any comments?) . Nice work Bob!!
At this time I am getting inspiration from the Buschorn design as a basis, but I am changing the geometry. I am learnig as I go, so I would like some advise on this. Martin, you comments would be really appreciated. Are there rules of thumb for the geometry? SInce I do not have mathcad (or perhaps the ability to use it properly) I am relying on using the fostex BLH recommended design for the 87E, and trying to keep length and expansion rations relatively close, but I am moving the mouth to the rear as to utilize a corner/back wall.
I am going to visit my brother in law (for thanksgiving holiday), who has a wood shop and will have about 6 days to complete a prototype. All advice is appreciated.
I will try to get scans of my current (rough) drawings to show you.
Cheers, Stuart
I also want a relatively compact design, which I concluded would necessitate a rear firing corner loaded design. That Dalek design looks like it might behave like a true horn, and very stylish to boot (Martin? any comments?) . Nice work Bob!!
At this time I am getting inspiration from the Buschorn design as a basis, but I am changing the geometry. I am learnig as I go, so I would like some advise on this. Martin, you comments would be really appreciated. Are there rules of thumb for the geometry? SInce I do not have mathcad (or perhaps the ability to use it properly) I am relying on using the fostex BLH recommended design for the 87E, and trying to keep length and expansion rations relatively close, but I am moving the mouth to the rear as to utilize a corner/back wall.
I am going to visit my brother in law (for thanksgiving holiday), who has a wood shop and will have about 6 days to complete a prototype. All advice is appreciated.
I will try to get scans of my current (rough) drawings to show you.
Cheers, Stuart
I have been working on some designs, reading Martin's very useful horn theory pages (trying deperately to understand them...I am not an engineer 
).
I am designing this one around the FE103E. I am using the Fostex BLH as a guide for geometry, but would like to go further towards a true horn and would like to calculate So, Sm, L, and compression chamber size for the FE103. And then I can work backwards though some necessary compromises. Does anyone have the consistant enclosure dimentions calculated for the FE103E' s?? This would be a big help to me.
Cheers, Stuart
). I am designing this one around the FE103E. I am using the Fostex BLH as a guide for geometry, but would like to go further towards a true horn and would like to calculate So, Sm, L, and compression chamber size for the FE103. And then I can work backwards though some necessary compromises. Does anyone have the consistant enclosure dimentions calculated for the FE103E' s?? This would be a big help to me.
Cheers, Stuart
Well, I did not want to go much larger than the Fostex recommend design (810mm tall, 450mm deep) although I was thinking to incorporate a flare in the width towards the bottom, if this would help. I would liek these things to be easily moveable. I may try designing the enclosure on CAD and using " emachineshop.com" to make an injection mold, or cast of some sort. It all depends on the materials they have and the price they will charge.
As soon as I have some good drawing/design to show, I will post. I struggle a bit with the math.
Stuart
As soon as I have some good drawing/design to show, I will post. I struggle a bit with the math.
Stuart
you might want to check out the Dallas II designed by Ron over at Fullrangedriver.com , its about 13" wide, 17" deep and is based on the FE206E. Plans are in the Gallery... Its suppose to sound VERY good.
-Jeff
-Jeff
Check these out!
am surprised that these have not been mentioned as they would seem to fit yout bill to a "T". Check out Onur's site.
http://www.yildiz.edu.tr/~ilkorur/
am surprised that these have not been mentioned as they would seem to fit yout bill to a "T". Check out Onur's site.
http://www.yildiz.edu.tr/~ilkorur/
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