What kind of enclosure is this?

[sskloss]

The illustration below is of a Toby Loudspeaker’s tower that I have had a pair of for ages. The only thing I am not sure of is the height and placement of the internal baffle. I cannot remember the model number, but I and a couple friends made a copy for each of us and have enjoyed them since 1989. To this day, I do not understand their operating principle. They are not ported (tuning would be too high) and not a true Transmission line either. They are, however, very efficient and can play solid down to 35Hz or so (driver Fs). The sound great with whatever mid-bass you put in them. We even ran 6x9 coaxials in a scrap pair and they were great – Toby did this as well I believe. What is the secret in the sauce?

Is it a 1/8 wave T-line? The fact that the port exit area is equal to the 8” mid-bass driver cone area, leads me to believe it is somewhere down that road. I could be completely wrong. I would like to see if the design is scalable and maybe for sub use. Anyone have any idea? It has been driving me nuts.

[adason]

its a bastard child of TL and BR

[sskloss]

Thanks for the reply, but you say it like it's a bad thing. Is it?

[sskloss]

Ok, I can see that. Without the portion trapped behind the baffle, the enclosure is about the right size for the driver in a BR configuration. So, in stead of being loaded with a port working on air mass, it uses a T-line to load it with a portion of the backwave? Very interested here.

[tvrgeek]

Subs are best done sealed. IMHO. They sound better to me and I don't have room for 500L boxes in my living room.

If you want to know how this box works, prototype one. Measure the impedance and response. Let us know.

[Pano]

Let's see if GM steps in. He'd know.
To me it looks like a BR with a very long port.

[sskloss]

I really like sealed myself, but the power requirements are on the high side for me. I'm on an efficiency kick at the moment. As for space, luckily I am not limited there. I have a storage room under the stairs to utilize and vent into the room.

[Scottmoose]

As far as I can see it's a BR with a very large vent, which will likely require some damping to attenuate its harmonic structure (unless you happen to like that sort of thing -a lot of Onken-fanciers do).

[Jim Griffin]

Of course you can always call Toby and ask him. When I lived in the Fort Worth area I would visit his shop a few times a year to hear what new creations he had in work. An interesting dude and worth talking speakers with him.

Welcome to Toby Corp. of America

[sskloss]

Originally Posted by Jim Griffin

Of course you can always call Toby and ask him. When I lived in the Fort Worth area I would visit his shop a few times a year to hear what new creations he had in work. An interesting dude and worth talking speakers with him.

Welcome to Toby Corp. of America

I used to work just a mile or so from his shop and have also stopped in a few times for either parts or to see what was cookin’. Once, I actually did ask him about this and his answer was “Become an audio engineer and all will become clear.” This could be taken a couple of ways, but I chose to take it as encouragement to learn more about the hobby that I love. Have I learned enough for this to become clear? Obviously not.