One Mid enclosure, several possibilities...

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I use a Flexunit 5" as mid from 225Hz to 2200Hz. As I have to rebuild the high/mid enclosure from my 3 way speaker (tweeter change), I am looking for the best type of enclosure to use.
For the moment, there are several possibilities:
-bass reflex because the flexunit is clearly designed for that. Verity Audio do that.
-sealed enclosure with a low Qt (0.5 at least).
-small closed transmission line like Egglestonworks for the Andra
-aperiodic-like as do Amphion for the Xenon and the Krypton.

As I know what will be the first reply, I think that I have not enough room for an open baffle mid.

All suggestions are welcome.


Open Baffle, Open Baffle, use an Open Baffle!;) . Ok just kidding of course. You haven't mentioned what type of bass alignment you plan to use. In the range that you are planning, I can't see any benefit of a reflex or TL other than complexity :xeye: . For simplicity the sealed would be the way. But then you have the same issues that plague every box speaker ( I won't bother to explain since S Linkwitz's site does). The Amphion approach is interesting in that (I believe) it is some type of attempt at cardioid radiation - which is good IMHO. Which leads me to a 5th possibility: a cardiod. Basically leaving the back of your midbass "box" open.
I believe that Gradient uses this type of approach (or something similar). It again depends on if you are using some form of active DSP type XO. Passive implementation may prove rather complex.
Perhaps you could give more info. The cardiod won't need quite as much rear wall distance as a true OB, but will retain some of the benifits. SL say's as much about Gradients approach.


It was a 2-way at first (10L vented but now sealed). Now it is the upper part of my 3-way speaker (Esotar+Flex 5"+Volt 2500). I found that the flexunit sound a little dark to my taste by moment.
Last, my speaker are tri-amplified with a Tact system.

Hi Christophe

I would agree with AJ- try to go for a type of open baffle. I say 'type of' because if you damp the rear wave it isn't strictly open-baffle anymore. One way of doing it would be to use an old patent idea I once saw (I can't remember who patented it). Basicaly it calls for staggered damping. IOW, you hang a sheet of damping material behind the driver, then leave a space open as deep as the damping material is thick, then add another piece of damping material, then another space, etc, etc. The patent does indicate that you can make holes in the damping material of a certain patern, but I can remember how. This does make the box design a lot more complicated, but should IMHO yield the best results. If open-baffle seems to much work, my vote goes for aperiodic. IIRC there once was an article that measured rise-time, and it found that aperiodic boxes had the fastest rise-times (if you understand what I am saying). Aperiodic has long been a favorite of mine (ranked just below damped open-baffle) for mids and upper-bass. Hope this helps. :)

Joined 2002
Simple experiment for aperiodic:

Knock up a box just slightly larger then the diameter of the speaker, and about 1/3rd the length of the lowest frequency it has to produce. Mount the driver in the front, then just stuff the back with as much filling as you can get in, then see if you like the result! If it's nearly right, then play with the amount of stuffing.
I like the idea of the cardioid radiation. I have never been able to find a picture of the head of the Gradient Revolution to find how it is built.
The Amphion seems very interesting and perhaps easier to build. I think that I will give it a try with my speaker this week. The holes on the sides are looking really small. Any idea about their size? For me, 4 or 5mm? Perhaps conical?

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