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Scottmoose
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#46

Post by Scottmoose »

StuG wrote:Just a quickie - is there any benefit to this style of manufacture?
None whatsoever. It is extremely wasteful of material, orients said sheet material in its weakest direction, and smoothing the path of a back-horn out simply promotes efficiency at the top end of its functional BW -viz. right where you want exactly the opposite.

-That looks like the original Frugel-horn. If you're thinking about it, do yourself a favour and don't do it. The latest version (Frugel-horn 3) is a big step forward in performance over the first one. If it wasn't, we wouldn't have released it.
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#47

Post by chris661 »

Pros: very very strong
Cons: expensive, very heavy.


The curves in the horn would increase the high frequency output of the horn compared to more angular paths, where pretty much only bass would come out the horn (the angles work as an acoustic crossover, filtering out the HF).

If there's excess HF coming out of the horn, it'll sound very weird - you'll get the HF from the driver, and then a little while later, some weird HF from the horn, which may or may not be in phase with the output from the driver.

In short, the curves depend on the intended bandwidth of the horn.

IMHO, for your build, stick to the plans - there's time for experimentation later.

Chris
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#48

Post by chris661 »

Scottmoose wrote:
StuG wrote:Just a quickie - is there any benefit to this style of manufacture?
None whatsoever. It is extremely wasteful of material, orients said sheet material in its weakest direction.
Ohh, didn't realise that.


Good for marketting hype, I'd expect.
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Greg
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#49

Post by Greg »

Hmmm, I'll agree the design uses loads of material, I'm not sure about laminate direction being a weakness using multiple layers of plywood in such a design. I would expect, assuming good sheet bonding/bolting, very serious rigidity and cabinet density. Would be a bugger to lift :lol:

Scott is the expert on the tuning aspect. I would never comment on that. If I was in the market for new speakers and asked Scott to advise me, it would be 'yes sir, yes sir, thank you sir, oh really, I thank you sir!'

He is the master :D
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#50

Post by simon »

I tend to agree on both accounts Greg - Scott's definitely the man with speaker design, no question.

Structurally though, in this application I doubt it would be any weaker and with the bracing/sides it might actually be stronger. Ply is strong in two dimensions but comparatively weak in the third; the composite in the photo probably improves the strength in the third dimension. But it wouldn't make any difference in reality I'm sure. It's horrendously wasteful of material too as said.
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#51

Post by planet10 »

StuG wrote: I will probably go for 22mm MDF for the enclosures, but I might just use 18mm as it seems to be widely accepted...
Hope i'm not too late or that someone else has chimed in.

15mm quality plywood would be better. You do need 18mm baffles for the A7 rebate.

Some will disagree, but MDF for speakers sucks. The chipboard prototypes we built when Scott, Chris & i were getting the Frugel-Horn Mk3 off the ground was better.

dave
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#52

Post by planet10 »

chris661 wrote:I'm not certain of the legitimacy of some of their claims: 95dB @1w, to 20Hz, from a single 8" driver?
With a rising FR you just have to choose the right place to pick a number :D

With a BIG horn giving lots of LF gain it is possible.

But some, despte claims -- like the Visaton B200 -- are really more like 90 dB

dave
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#53

Post by planet10 »

Greg wrote:Hmmm, I'll agree the design uses loads of material, I'm not sure about laminate direction being a weakness using multiple layers of plywood in such a design. I would expect, assuming good sheet bonding/bolting, very serious rigidity and cabinet density. Would be a bugger to lift
Higher density is not necessarily a good thing. Given the same stiffness, the ligher material is better. And if it is variable density, for an extreme example, carbon fiber over cork, even better.

You will note that the translams have much thicker walls then using the panel in the orientation it is designed for. I fully expect that 12mm quality ply would outperform what looks like a translam 2x thicker. And you can get an entire FH3 out of a 5x5 of BB (with some baffle trickery)

dave
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#54

Post by planet10 »

StuG wrote: boenicke
Scott & i have discussed their designs quite a bit. Now i haven't heard them, so any comments are pure cnjecture, but there looks to be more fashion than design.

The line behind the midbass certainly ignored a whole bunch of well-known design considerations.

dave
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#55

Post by Scottmoose »

chris661 wrote: Ohh, didn't realise that.
Good for marketting hype, I'd expect.
That it is Chris. Looks pretty, but that's about it as far as back loads go, except in some very particular cases.
Hmmm, I'll agree the design uses loads of material, I'm not sure about laminate direction being a weakness using multiple layers of plywood in such a design. I would expect, assuming good sheet bonding/bolting, very serious rigidity and cabinet density. Would be a bugger to lift
It's fine for the outer panels, but for thinner internal strips, for e.g. those that make up the front baffle, it can get rather flimsy & you start to run into some rather interesting resonance modes. I first learned of this when researching the armour of 19th century warships of all things, and their wooden backings. Translam is pretty, especially if perspex or toughened glass sides are used so you can see the internal form, but IMO it's not worth the effort.

The density side of things is a double-edged sword. Ideally, since you can't erradicate panel resonance, you want to push it outside the operating bandwidth (BW) of the box. When you try to go low, you need enormous thicknesses for a bass enclousre since panel Fs only drops to 0.707x that of a single thickness each time you double it. Worse, the lower the panel Fs, the higher the amplitude & wider the resonant BW becomes, so you end up needing huge amounts of damping. High mass is good for midrange enclosures though. :)

TBH, a lot of what I wrote above though is really pretentious. It's true enough, but once you get beyond a certain point, IMO life becomes too short (hifi wire anybody? ;) ). The more I learn about speakers, the more I realise how little I actually know.
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