Double Chamber Reflex Vent Question

[Guss]

What about 'double tuned bass reflex'? I'm looking for a good reading about those multiple BR chambers but there is a lot of junk among the info.

[kelticwizard]

Guss, what do you need to know? You have already received the necessary info on how to build one type of popular double tuned reflex.

I've never built one, but I have done extensive reading on them. Tell you what. Give me the Thilele-Small parameters of the woofer you are planning to use and I will design one for you step-by-step according to Weems' instructions.

The woofer you select should be usable for just a normal bass reflex box as well.

Okay?

[claudio]

Guss,
I thought that my HP explains in a simple way Weems' DCR: what do you think is "junk" in my explanation?

Regards
Claudio

[Guss]

Originally posted by kelticwizard
Guss, what do you need to know? You have already received the necessary info on how to build one type of popular double tuned reflex.

I've never built one, but I have done extensive reading on them. Tell you what. Give me the Thilele-Small parameters of the woofer you are planning to use and I will design one for you step-by-step according to Weems' instructions.

The woofer you select should be usable for just a normal bass reflex box as well.

Okay?

I can design it and yes the woofer I plan to use is suitable for BR. I know enough about the popular DCR, true, but I realized that there is another way to go, the one listed as DBR Fostex' on your page Claudio. From the drawings I guess the chambers are two perfect 1/2 of the total volume and the port is the same. Twas all I really wanted to know...

Weems :
2:1 woofr and the port
1:2 port
3 ports, same lengths , is computed as a dual ported box

Now correct me if I'm wrong
DBR fostex ?? :
1:1 woofer
1:1 port
2 ports , same lengths , might be computed as a single ported box?

[Guss]

Originally posted by claudio
Guss,
I thought that my HP explains in a simple way Weems' DCR: what do you think is "junk" in my explanation?

Regards
Claudio

There is no junk in your HP claudio, I meant on the net, google...altavista...

[GM]

>Nevertheless, it useful to know that Karlsen invented the box first, with Augspurger patenting an improvement in it. Up to know, I thought Augspurger came up with the whole concept.
====
Yeah, as the inventor Tom Danley has lamented, the ancients keep stealing all his 'inventions'.

Anyway, I got to looking at the math I did late last night since I do it so poorly and found I'd totally screwed it up. The K -15 is actually a quadra reflex chambered design, or DBR + BP depending on how you choose to view it and the DBR ratio is almost exactly 1.0:0.5 (2:1), so once the driver's Vb is subtracted out it should be ~spot on.

Just speculating, but it looks like Augspurger did like B*** and so many others have done in that once the original patents expired, applied for it as their own. Oh well, you can only manipulate a soundwave in so many ways and the more I've studied old patents, the more it appears that the audio pioneers pretty much tried them all.

GM

[kelticwizard]

Guss:

The Fostex style DBX can be modelled on the Adire freeware version of LspCAD, provided Adire has a woofer available with a Qts equal to or less than the woofer you plan to use.

The Adire version of LspCAD allows you to add a resistor in series to the woofer. This raises the Qts-Weems gives instructions on how to do it, I can help you with that. Then just come up with a box you like the graph of, and divide the box volumes by the same proportions of the Vas of the Adire woofer divided by the Vas of the driver you are using. If the driver you are using has half the Vas of the Adire driver, then the box volumes you need for your woofer are half the volumes that LspCAD says is required for the Adire woofer.

Am I making myself clear?

I have modelled a few boxes on the Adire freeware, and I should report that the Fostex style DBR has a notch in the response, frequently very significant. The freeware models the size of the notch.