Frugel-Horn Mk3

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Is the 108 in the Frugel able to put out about the same amount of SPL as the Fostex recommended, before distortion, or does the 108 reach its limits significantly earlier than in the Fostex recommended ?

I can't speak to that. But i can say the FH3 sounds better. In the end our Fostex recommended horn was determined to be a waste of plywood and was burned.

dave
 
Should be much of a muchness WRT outright excursion; the Fostex 108 box isn't much to shout about on that front itself.

The fact is, from a technical POV, unless the 108 is high passed, it's distorting badly whatever you do with it. Since you seem to be happy with what you have, I'd probably stick with it and spend the money you save on enclosure materials for more music.
 
I can't speak to that. But i can say the FH3 sounds better. In the end our Fostex recommended horn was determined to be a waste of plywood and was burned.

dave

ok thats possible, I actually never tried the 108EZ in there, whats in there now is a 108ESII.
but in the Swan with corrected chamber, the 108EZ worked very well and sounds good.
 
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Ok, let's do a little error-correcting now, before things get out of hand. The main FH3 thread contains almost all the information you ask about, but it's spread over a wide number of posts. So.

Not true. That might be what you define as a back horn, but the physics are another matter. A back-horn does not automatically have to possess a low-pass filter chamber. End of story. The throat area is part of the horn (FH3 which is a tapped hypex corner horn has an St = 0, i.e. its throat has almost no physical area, although compression effects mean acoustically it has a small amount), and total efficiency is determined by the expansion profile.

FH3 has no connection to the Replikon. Like most back horns with a chamber, the Replikon is essentially a bass reflex box with a large vent. It's simply a matter of degree. FH3 takes exactly the opposite approach: it has no chamber of any kind, just the horn itself. There is a small choke in the horn expansion near the base; this has no effect on F3, it is merely there to provide a sharper upper corner frequency.

The FE108ESigma has the grand total of 0.28mm of linear travel before reaching advertised Xmax (definition of latter unspecified -there are quite a few), so if you're concerned about remaining within this, then you'll need to forget any attempt to extract LF from it and high pass 2nd order at about 500Hz. There is no enclosure, not even a full-sized horn, which will keep it within 0.28mm deflection while getting < 100Hz out of it.


I simulated it in Akabak, not exactly easy to connect the nodes right for a FH3 script, no wonder I do not have practice anymore =)

I see that the excursion is a bigger and the frequency graph is less peaky, indicating a smoother sound, but its some less loud too =)

Excursion, impedance and frequency plot do look like a horn, all tough its really squeezed to flat, could be that it sounds more compressed.
Nice design well made, thinking about making a pair and see what my ESII can do there.

thanks again for the help :)
 
Best location for bass traps with the FH3?

Since its a corner-loaded horn (mine use the MA CHP-70eN drivers) what is the recommended placement of bass traps in the room? I assume it's NOT the front wall corners behind the speakers. Would it be on the back wall (behind the listening position) or somewhere along the side walls? I'm trying to tighten up the bass a bit.

Tom
 
Since its a corner-loaded horn (mine use the MA CHP-70eN drivers) what is the recommended placement of bass traps in the room? I assume it's NOT the front wall corners behind the speakers. Would it be on the back wall (behind the listening position) or somewhere along the side walls? I'm trying to tighten up the bass a bit.

Tom



Mark's drivers already have a fair degree of BSC contour engineered into their frequency response and certainly don't need the corner loading as do drivers such as the FE126 .

Two things you might want to consider

- experimenting with levels of fill fiber within the enclosure
- pulling the enclosures further out from the apex of the corners
 
Bass traps? I wouldn't have thought you'd need them, since while FH3 isn't bad in the LF for a small horn, it's not exactly got the LF heft of a couple of 15in HE Altecs.

Before you start thinking bass traps, have you tried adding more damping to the enclosure? If not, add some below the driver, or a nice big handful stuffed into the bottom of the box through the choke.

WRT bass trap placement, there's no short answer unfortunately; it depends on the room acoustics & modes as to where they're most effective, assuming you're even able to place them where they're most effective. Bass traps are big.
 
Bass traps? I wouldn't have thought you'd need them, since while FH3 isn't bad in the LF for a small horn, it's not exactly got the LF heft of a couple of 15in HE Altecs.

Before you start thinking bass traps, have you tried adding more damping to the enclosure? If not, add some below the driver, or a nice big handful stuffed into the bottom of the box through the choke.

WRT bass trap placement, there's no short answer unfortunately; it depends on the room acoustics & modes as to where they're most effective, assuming you're even able to place them where they're most effective. Bass traps are big.

I've got the speakers pulled out 21" from the front wall and 12" from the side walls. These dims correspond to the 1/9th and 1/11th rule. I could pull them out even further, but they will start coming into the room pretty far if I do. I have stuffing below the driver now, but maybe I'll try some additional fill stuffed in through the choke (the tops are glued on now) and see what that does to tighten them up. Thanks.
 
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For anyone wishing to try the FH3 quickly and cheap in a slightly smaller format, I just built a 30 in tall one in an evening and morning using paper faced foam core boards from the dollar store and the Vifa TC9FD 3.5 inch driver with pretty good results. More info in this thread:
http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures-102.html

It is not an FH3. As soon as you changed the dimensions it ceased being an FH3. Nice to see the FH3 insporation for sure.

dabe


it could sound quite fine, and Scott/ Dave should probably be flattered

of course, if it doesn't, well then "Mr Phelps, the Secretary will disavow any knowledge of your team or mission" (did I get that more or less right?)
 
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it could sound quite fine, and Scott/ Dave should probably be flattered

of course, if it doesn't, well then "Mr Phelps, the Secretary will disavow any knowledge of your team or mission" (did I get that more or less right?)

Thanks for the support Mr. Secretary ;) To me, it sounds really good, so much so that I promptly ordered more drivers to build the other channel. I am playing with varying the stuffing and type of stuffing. The neatest thing is how light weight they are yet still manage to make such a lovely full rich sound with nice bass. The lightness makes me wonder if many speaker designs can be made with 1/4 in or even 3/16 thick plywood and work just fine. As much as this foam core design ceases to be an FH3 the moment dimensions are changed, it owes it's great sound to the design that inspired it. One other thing, if you are not sure if you will like it, the cost and effort to build isn't a big deal. And if you find that you like it in foam, you can go forward with a real wood and pricey driver build with confidence.
 
Does make you wonder about the obsession with void free Russian birch ply and associated loathing of other materials, MDF particularly which I for one rather like. My suspicion is that the stiffness of a board is less important then it's ability to store and return energy, isn't a material that's inherently lossy preferable? I always think, could you make an effective spring out of it? If so, it's probably not good.
 
I look at this problem as being three separate issues.

1. Panel resonance. This is where the panel will contribute sound at specific frequencies.

2. Panel breathing. This is where the panel moves in and out with the pressure wave within the box.

3. Panel transparency. This is where sound simply passes through the panel.

I did some very cursory experiments with a relatively small box and panel. The panel was 10"x17" 18mm TigerPly. The SPL contributed by the panel was better that 40dB down from the SPL of the driver. I found no spikes in the FR that would indicate panel resonance. I should have run a THD, but didn't. I would expect any resonances to appear in the THD.

I plan to run more exhaustive tests this summer, and my current opinion is subject to rapid change but:

If we are not talking about a sub or very large panels (whatever that means), cross bracing in irrelevant. As long as the panel is stiff enough to prevent breathing at the lowest frequency, don't bother.

In small panels, resonant artifacts are sufficiently low in SPL to be ignored.

The major issue in panel sound production is transparency. Wood is a pretty good conductor of sound. The stiffer and harder the wood, the better it conducts sound. This suggest that MDF might really be the better choice for small boxes. I am thinking of even softer materials; polystyrene bead-board or Celotex.

I don't want to restart the MDF/BB flame war and I will not address any response the tries to go there. I will address this later when I have hard data. Anyway, I am beginning to think that bracing is a small box, say 20L or less is a waist of time.

Bob
 
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Almost all materials used for cabinets will have "spring" to them, i.e., a Young's modulus value sufficiently high to allow them to be used in structural members. It's the amount of damping that is important. MDF probably has high inherent damping and wood boards used for guitar bodies probably much less. The foam core definitely has spring in it because you can push down on it and see it flexes back. There is however, damping in the foam and the paper as it is flexed. Horns and TL's are like flutes and other woodwind instruments - 1/4-wave aero-acoustic devices where the dominant acoustical prodcction results from the vibration of the air volume contained within the boundaries defined by the walls. The sound emanating from the walls themselves are a smaller secondary acoustic effect. Of course, this is an area of hotly contested debate - for example, the argument of which metal produces a better sound in a concert flute? Silver, nickel, gold? There may be very minor differences but the majority of the sound from a PVC or wooden flute will be indistinguishable from a nickel, silver or gold flute. So in a similar way, I am seeing a similar thing in horn and transmission line speakers. Of course, the vibrations in the walls of the speakers will produce sound and many will say that it colors the sound and you are not getting a true reproduction of the sound as recorded. True. However, people don't buy studio monitors (which are designed to have a flat response) to listen as their main speakers for the *enjoyment* of music. Some coloration is not necessarily bad as it may reinforce/copy the natural harmonics of certain instruments that are aero-acoustic like woodwinds, the human voice, horns, etc. If you ever look at the spectrum of a single note played on a flute or a single note of the human voice, it is not a single peak at one frequency but rather a distribution of peaks very much like the multiple peaks that a horn loaded speaker puts out. Sorry if this hijacked the thread.... I can continue this in another new post or a similar one regarding materials for speaker enclosures.
 
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I did some very cursory experiments with a relatively small box and panel. The panel was 10"x17" 18mm TigerPly. The SPL contributed by the panel was better that 40dB down from the SPL of the driver. I found no spikes in the FR that would indicate panel resonance. I should have run a THD, but didn't. I would expect any resonances to appear in the THD.

The major issue in panel sound production is transparency. Wood is a pretty good conductor of sound. The stiffer and harder the wood, the better it conducts sound. This suggest that MDF might really be the better choice for small boxes. I am thinking of even softer materials; polystyrene bead-board or Celotex.


Bob

I totally agree with Bob Brines. Real measurements - great! 40 dB down is pretty much in the mud. The suggestion of softer materials is interesting - foam core boards are definitely softer!