Spawn of Frugel-Horn

frugal-phile™
Joined 2001
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As you know Scottmoose has been helping out with MJK sims of the Frugel-Horn (since MJK as yet doesn't do 1/8 space these are only of interest as a design reference when compared against one another)

Anyway, this spurred Scott towards implementing some of the stuff floating around in his brain and has spawned a new member of the Frugel Family... if the original Frugel-Horn is the mama, this is the tall-gangly -- but smart -- teenager.

Inspired by Terry Cain's double mouth BEN series, the Replikon (discussed here http://www.diyaudio.com/forums/showthread.php?s=&threadid=55721 and conversations with GM about the big box (CC) long exponential port bass reflex style horn as respresented by the Replikon, Scott came up with a box that is very tolerent of differing driver parameters. It also requires no curves to be cut.

Scott is building the 1st prototypes now, and will hopefully get a chance to let them get a listen at the upcoming EggFest.

The working name for this horn was the FrugelBEN, but unless Terry Cain gives his blessing, we'll need to come up with a different catchy name -- DoubleFrugel is kinda derivative.

I haven't got detailed plans ready yet, but i will, in the next series of posts, attach some teasres.

dave
 

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Hi Guys

Can I take it you like them, then? ;>) Dave's been a Saint, indulging my insane ideas and drawing like mad; so has Martin, who helped interpret the data (to say nothing of creating the worksheets I use to design everything), and Greg, for his encouragement and advice whenever I asked for it.

As Dave mentioned, I've got the first pair in hand at the moment, using a pair of his modified FE126Es (which arrived yesterday: think baby modified Decware 206 and you're on the right lines), so I'll let you know the preliminary results. Unlike the Frugelhorn, these are not intended for corner placement , but for more general room-use.

Re the responses. The lower mouth will see a reflection boundary condition (the floor) to a greater extent than the upper, so bass will likely be somewhat stronger than the 1/2 space sim suggests. We did toy with the idea of a reduction in the size of the lower horn to compensate for the different pressures this entails, but in the end, we decided symmetry rules.

Why a double horn? Terry Cain's magnificent double BEN designs provided the inspiration (so it's all your fault Terry, if you're out there... ;>), which is why we thought of calling them the FrugelBEN, partly humourous, but with a healthy dose of admiration in there too.

Aside from that, the benefits are considerable. Reduces footprint, it's a bit different from the things more usually seen, and also I / we wanted to explore the potential of a nominally symmetrical radiation pattern from the MDM (Mouth Driver Mouth ;>) layout. Why a Big Vent Reflex type horn, similar to a Replikon, instead of the more usual type? Again, variety. You don't often see them, which is a shame, because they work very well, so I though, why not?

BWRX said:


Do the really small throat and large mouth area have anything to do with the reasonably driver independent response?

Good question. It's a combination of factors. Greg and Martin can explain the technicalities of the system behaviour far better than I can. It's mainly because the system operates in a similar way to a reflex enclosure in that below 100Hz, the horn dominates the response, so within reason (i.e. so long as the driver's Vas doesn't swamp the chamber etc's volume, and it's motor is strong enough to drive said horn), it's pretty tollerant: it doesn't affect the driver's own SPL curve over 100Hz much either, so it's very well behaved.

The Jordan's should work. Their Fs is a little low, if anything, but I suspect they'll go in, no problem at all. I'll run a sim tomorrow to check. Unfortnately, you can't do a quick and dirty check in one of the simpler sheets with this box -it's the full-blown sections sheet or nothing, so it takes a little while. If anyone has any quick requests for driver checks, say so now and I'll do them as a job-lot tomorrow.

Cheers for now
Scott
 
:D I like that, Greg.


Re the other drivers and BIB comparison etc, it's difficult to say as there were very different objectives in mind.

I really designed them for drivers in the 4 - 4 1/2in range. However, I looked at the larger Fostex drivers out of interest. The only one that will have much of a chance of working in these particular boxes would be the defunct non 'E' FE168Sigma, (providing the full potential CC volume was used), as it's Vas is sufficiently low.

Regarding extension: well, using the 4in and 4 1/2in Fostex units, I reckon they'll be about equal to a BIB designed with those drivers, and rather more versitle in not needing a corner to work properly. However, a larger BIB -say one using the Monacor SPH-60X upward, would go considerably lower than these can achieve. I don't have a baby BIB myself, mine are somewhat larger, so I won't be able to do a direct comparison. For what it's worth though, I've designed and I'm building these for my FE126Es; not a BIB, love them though I do. The BIB really comes into its own with drivers sized about 5in upward, with an Fs of 60Hz or lower. For smaller drive-units, with a higher Fs, although you can build them, and they'll work well, I reckon there are equally good or better options. Hense this new double horn. They are of course a lot larger, and will have a different sound and presentation, so it's a case of whichever works best for you! Nice to have a few designs available to suit all pockets, rooms and sonic preferences.
Best
Scott
 
BWRX said:


Do the really small throat and large mouth area have anything to do with the reasonably driver independent response?

Greets!

It's the acoustically fairly large filter chamber (aka the misnomer 'CC'). It's a matter of impedance matching with the horn being overdamped and the CC underdamped, so when you get a 'close enough' balance, a ~flat response over whatever gain BW the horn vent defines is achieved.

GM