ML TQWT for Fostex FE167e

[RaphTube]

OK, So I've decided I like the FE167e, and I can get it fairly easily.
And I'd like to try a TQWT (Tapered Quarter-Wave Tube), and it seems like ML (Mass Loaded) is a good idea.

So... my plan is to build a ML TQWT for the FE167e (like the thread heading suggests).

So far I'm looking at building the Demetri which I saw at Planet_10 hi-fi.

http://www.planet10-hifi.com/boxes-fostex.html#demetri

Is there anything I need to know about before I go ahead with this?

Let me just say, I don't have much experience, and I have limited knowledge when it comes to building speakers.
So I'm looking for something which is "tried & tested". I don't wan't to be calculating resonances, or comparing graphs.

-Raphael

 

[RaphTube]

Pointy Ends?

One thing I'm a little worried about with the Demetri design, is that it extends right to a point.

I can't recall why at the moment, but I vaguely remember that to be a bad thing, and that there should be a small surface area at the small end of the taper.

Any thoughts??

 

[planet10]

Re: Pointy Ends?

One thing I'm a little worried about with the Demetri design, is that it extends right to a point.

I can't recall why at the moment, but I vaguely remember that to be a bad thing, and that there should be a small surface area at the small end of the taper.

Originally it didn't, but the work Scottmoose did on the design showed that it made little difference, so we just left the endstop piece out. You do want to have fairly dense stuffing at the point.

Another design to consider is MJK's original ML-TQWT.

dave

 

[RaphTube]

Compatibility?

Thanks!

Yes I like MJK's Design very much.
Any Idea about sonic differences? I need something to base my decision on. I'm not worried about the wood-work, and both are fine aesthetically.

Can I just dump the FE167e MJK's box? (designed for FE164), or will I need to make any adjustments?

-Raphael

 

[planet10]

Re: Compatibility?

Can I just dump the FE167e MJK's box? (designed for FE164)

Yes.

dave

 

[chrisb]

I haven't heard the MJK design, but I can tell you that Demetri definitely performs ( I daresay no BSC required on this puppy), and while it certainly depends on the individuals, passed the WAF around here.

 

[Scottmoose]

FYI, a throat area (if a cabinet expands toward the terminus, it's technically a horn) of 0 isn't actually a bad thing if used properly -quite the reverse in fact as you get the maximum pipe-gain.

 

[RaphTube]

Thanks

FYI, a throat area (if a cabinet expands toward the terminus, it's technically a horn) of 0 isn't actually a bad thing if used properly -quite the reverse in fact as you get the maximum pipe-gain.

-Thanks
What do you mean about "maximum pipe-gain"

And Thanks generally for the input guys.
I'm still undecided about which one to go with though.
-I think a good question to ask would be: "which one will be more versatile when it comes to amplifiers, and music styles?" I have a very diverse musical taste, and although they will mostly be running on my home-made 10W 6l6 tube-amp, I'll probably be connecting them to anything with an 8 ohm output, tubes or no tubes.

-Raphael

 

[planet10]

If you ignore the LF these will be more similar than different... i've not heaed a set of the MJK pipes, but speaking in general terms based on experience & supposition:

1/ the wider baffle of demetri will give it a greater diffration signiture, but lowers the point at which baffle step occurs. Placed close to a wall, no BSC will likely be required. The diffraction signature can be larger ameriolated by using a supraBaffle to optimize wavelaunch and minimize late diffraction

2/ the high aspect ratio vent in Demetri is intended to minimize tuning errors due to the dynamic variability of driver (T/S) charateristics (it is like a resistor in series with the port). You lose some port gain (countered somewhat by the greater pipe gain due to the port), and in my experience gives the bass a sense of greater control (i always seem to by putting a wad of damping in the ports of BR, ML-V, and ML-TLs to kill what i feel is too much boom...

3/ cosmetic... i actually prefer the look of the MJK ML-TQWT (althou i'd change the presentation of the taper), Demetri with the 167 looks a bit out of place on the broad shouldered Demetri, this could be decreased i expect by dramatically rounding the top corners -- buit some would say that would make it look too much like a tombstone. Somewhere deep in my notes there is the basics of a slightly smaller monolith specifically for the 167 (not likely to go quite as low (maybe good, maybe not)

dave

 

[Scottmoose]

Re: Thanks

What do you mean about "maximum pipe-gain"

It means you get the maximum gain from a pipe of X length & volume. Smaller the throat, the higher the pressure.

 

[grindstone]

driver?

chris -- was your experience with 167's or 207's?

thanks

 

[chrisb]

Re: driver?

chris -- was your experience with 167's or 207's?

thanks

sorry for the delayed reply - the answer is FE167E

 

[RaphTube]

Going with Demetri!

OK, so I'm going with the Demetri.
Thanks for the input, I'm really getting excited about this one.

The diffraction signature can be larger ameriolated by using a supraBaffle to optimize wavelaunch and minimize late diffraction

This sounds interesting, but I couldn't get the link to work. Could I get some more info about this please.

-I'll post some pics as soon as I get started.

-Raphael

 

[planet10]

I've fixed the broken link, but here is the picture as an image... the sB is the walnut bit.

dave

 

[RaphTube]

Very Nice!

Thanks.

Would it do any good to extend the baffle above the top of the box?
-the driver sits quite close to the top, and that's the nearest edge.

-Raphael

 

[planet10]

Re: Very Nice!

Would it do any good to extend the baffle above the top of the box?

As pictured on PAWO it wouldn't work, but on Mileva & Demetri it is something i have already envisied... -- might even have a drawing. where it sticks up it should also extend backwards. The idea is to have a relatively small baffle with a large curvature at HF (the SB -- low and early secondary edge diffraction) and a larger baffle at LF (lower BS frequency). A larger sB would need to be thicker with a larger roundover.

dave

 

[RaphTube]

SB ??

The idea is to have a relatively small baffle with a large curvature at HF (the SB -- low and early secondary edge diffraction) and a larger baffle at LF (lower BS frequency). A larger sB would need to be thicker with a larger roundover.

Excuse my ignorance, -What is SB?

So the idea is to try "integrate" the box with the wall behind it?
Am I lost here?

 

[planet10]

Re: SB ??

What is SB?

supraBaffle

So the idea is to try "integrate" the box with the wall behind it?

Yes. At LF we'd like the box to seem very wide but the same time make the box look narrow at higher frequencies.

dave

 

[RaphTube]

Feet?

Not that I'm anywhere near the feet stage yet, but would you put three feet or four feet per box?

I would think three would be fine, but I'm worried that they will be a bit unstable with such a small box-depth.
-unless I put two on one side and one on the other (instead of two in front, and one at the back) but that might look funny!

Is there any real disadvantage to four, apart from it possibly rocking?

 

[planet10]

If you can make 3 work that is theoretically better, but 4 is probably more practical.

Here is the sketch of the supraBaffled Demetri i did... this is with 207 (and room for a tweeter in the sB)

dave