Crossbreed of transmission line and bass reflex?

TSalama

Member
2016-02-13 10:27 pm
Finnish Hi-Fi company Hifitalo has some DIY designs that incorporate their own (as far as they claim) TransFlex enclosure designs.

I've tried searching transflex, and browsed some resulting threads about tapped horn designs and transflex design, which apparently originally is an older idea that has been patented at some point(?) and that seems to incorporate an inward firing driver(?).

However, I'd like to ask if anyone knows how to calculate these "TransFlex" cabinets Hifitalo uses. By drawings they seem to be bass reflex cabinets with an outward firing woofer, but incorporating inner structure of adjacent chambers of increasing volume with ports in between with increasing port area. Hifitalo claims the enclosures have very controlled bass response and reduced woofer excursion.

Hifitalo is a fairly big Finnish Hi-Fi company that for instance is the official importer of Seas drivers in Finland. Hifitalo also bought an established Finnish loudspeaker company OR and continues their manufacturing with some very good results. I've also heard one of their DIY designs incorporating the "TransFlex" (Aw-3 Alu https://www.hifitalo.fi/aw-3_alu_rakennussarja) that sounded really good, especially the bass for that small a speaker. Based on all of this, Snake Oil isn't the first thing I'm thinking.

Does anyone know a way of calculating this kind of enclosures consisting of adjacent chambers that have ports between them? By intuition I'd imagine they might be essentially transmission lines or horns or derivatives thereof.

In the next posts I'll link a few of these designs I'm talking about. Hifitalo has descriptions (or actually marketing speeches) for the designs in Finnish, but I think the detailed blueprints speak more of the actual designs, so I'll link the blueprint PDF's. Every enclosure is supposedly designed for a specific speaker (or a specific woofer), so I'll include driver name and any essential info provided (as well as the original sales speech page as a link as well).
 
Ummm, dunno.

Looking at the first one, it appears that piece 8 (C-Pala) divides the overall volume into two separate chambers, small above and large below. Each of these volumes is further divided by pieces 6 and 9 which have some corners cut off - the last of the chambers thereby created are vented to the environment. I think pieces 5 are just braces - there is too much free space to be much of a restriction.

Looks like 2 DBR enclosures offset tuned in one box. Could be an effort to stagger tune the resonances for flatter response and/or impedance. Can't read the text so I may be miles off.
 
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TSalama

Member
2016-02-13 10:27 pm
So, by my calculations, for AW-30 Alu (L18RNX/P woofers for both enclosure parts) the cabinet volumes are as follow:

The upper woofer that crosses over with tweeter has behind it
- 2,96 liter chamber (minus the protruding parts of the woofer itself). 4*12,5 cm2 holes (combined 50 cm2 port) lead to the next chamber
- 3,02 liter chamber. 36,125 cm2 hole leads to the next chamber
- 4,64 liter chamber. A 45 mm diameter (63,6 cm2) and 200 mm long reflex tube leads out.

The lower woofer that acts as 2.5 woofer has behind it
- 2,96 liter chamber (minus the protruding parts of the woofer itself). 4*12,5 cm2 holes (combined 50 cm2 port) lead to the next chamber
- 3,02 liter chamber. 50 cm2 hole leads to the next chamber
- 5,69 liter chamber. 112,5 cm2 hole(s) lead to the next chamber
- 9,18 liter chamber. A 70 mm diameter (153,94 cm2) and 160 mm long reflex tube leads out.
 
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TSalama

Member
2016-02-13 10:27 pm
Ummm, dunno.

Looking at the first one, it appears that piece 8 (C-Pala) divides the overall volume into two separate chambers, small above and large below. Each of these volumes is further divided by pieces 6 and 9 which have some corners cut off - the last of the chambers thereby created are vented to the environment. I think pieces 5 are just braces - there is too much free space to be much of a restriction.

Looks like 2 DBR enclosures offset tuned in one box. Could be an effort to stagger tune the resonances for flatter response and/or impedance. Can't read the text so I may be miles off.

The C-Pala definitely divides the overall volume into two separate chambers, small above and large below. "Pala", by the way, is Finnish for 'piece' or 'part' etc. So it's C-piece, if it feels any more logical than the alien sounding Finnish names. :)

Looking at the 5-pieces (or A-Pala) at AW-30 Alu, the woofers go 78 mm deep from the outer plane of the baffle and have a 110 mm diameter magnet, so the magnet wouldn't fill the A-piece's hole at 120 mm depth from the baffle's outer plane, and the port to the next chamber would be fairly big (105 mm hole diameter at 32 mm away from the woofer's 110 mm diameter magnet plus the cutaway corners). Maybe it's just a brace and the holed A-piece just keeps filling out of the woofers way(?).
 
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TSalama

Member
2016-02-13 10:27 pm
So, the first piece behind the woofers probably just being a brace, the dimensions for the AW-30 Alu would be:

(L18RNX/P woofers for both enclosure parts) the cabinet volumes as follow:

The upper woofer that crosses over with tweeter has behind it
- 5,98 liter chamber. 36,125 cm2 hole leads to the next chamber
- 4,64 liter chamber. A 45 mm diameter (63,6 cm2) and 200 mm long reflex tube leads out.

The lower woofer that acts as 2.5 woofer has behind it
- 5,98 liter chamber. 50 cm2 hole leads to the next chamber
- 5,69 liter chamber. 112,5 cm2 hole(s) lead to the next chamber
- 9,18 liter chamber. A 70 mm diameter (153,94 cm2) and 160 mm long reflex tube leads out.
 
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