Double chamber reflex rebellion

[kelticwizard]

Originally posted by Hezz
Thanks for all your responses guys. Except for Ron E.

My idea is to make the primary chamber the full size that the driver needs and have the sub chamber at the usual half volume of the primary. Now, if the primary chamber resonants at the Thiel/Small tuning and together they resonate an octave lower where the bass falls off more wouldn't this extend the response even further and still properly tune the driver. Granted it would take more cabinet space and it would effect driver impeadance differently. But I'm curious if it would be successful.

I was under the impression that according to Thiel /Small guidelines there was only one frequency to properly tune any given driver. If this is so, isn't the second tuning point moved away from the ideal.

There isn't. Thiele-Small simply predicted how a given driver would act when put in a certain size box and tuned a certain way. I suppose flat response was held up as the ideal, but the number can be used to predict response that vary from flat response as well.

David Weems recommends such in his book, pointing out that if you want a speaker put into a box half the size of the "ideal" one, yo ucan simply put it in the half size box, tune it half an octave above the "ideal" tuning, and you are set-provided you don't mind a 2.3 dB hump in the response the octave above cutoff. It's a compromise many home builders will make.

so if you waqnt to increase box size to go lower, it conceivably can work. Remember, according to Thiele:
Twice the cabinet volume = 6 dB more sensitive OR 1/2 octave lower. Either one, not both.

Yo might try asking Freddy for his Double Chamber Reflex Program as well. I think the shape of things might become clear then.

[kelticwizard]

If you are a fan of double action on your bass enhancement, have you ever looked at Martin J King's Mass Loaded Transmission Line worksheets? It usuallly results in a 5th order rolloff, but the bass response is definitely stretched downward. More excursion relief than a simple bass reflex as well.

[Hezz]

Kelticwizard,

Thanks for your feedback. I am also considering the mass loaded TL for this project but based on my experience the double chamber is easier to design and more forgiving.

I have some Dynaudio drivers around that I was contemplating using for this project but unfortunately these drivers don't perform well down low. They are a model designed for a very small box. This is why I am considering the double chamber reflex.

The mass loaded TL seems to be the ultimate. Isn't this the loading that the Von Schweikert VR-4's and up use. They are know for outstanding bass response in a small package.

[kelticwizard]

Not familiar with the Von Schweickert, though I have heard of them in passing as being very high end. From the sims I have done, yes, the the Mass Loaded TL's do stretch the F3 cutoff point down lower than the simple reflex.