Open Baffle With a Cancelling Driver, Anyone?

[borispm]

I like the open and uncolored sound of open baffles, but they are simply too large (or requires too much power and equalization), so I came up with such an idea, that is to add another driver enclosed in a box that is relatively large for the driver (the driver is wired in phase as the primary driver), and firing up to cancel the rear radiating wave of the primary driver.

I am not expecting the same level of performance of a real OB, but at least an improvement over original closed box.

The most likely candidate for the driver will be the Tangband W3 1364SA.

Can anyone give me some advice?

[ThorstenL]

Hi,

Originally Posted by borispm

I like the open and uncolored sound of open baffles, but they are simply too large (or requires too much power and equalization), so I came up with such an idea, that is to add another driver enclosed in a box that is relatively large for the driver (the driver is wired in phase as the primary driver), and firing up to cancel the rear radiating wave of the primary driver.

If both drivers are correctly equalised to have the same frequency response you will have made a cardiode system. This is probably not what you had in mind, but it is a good idea... I have been exploring such systems before but with much larger drivers and DSP to do the EQ.

Ciao T

[c2cthomas]

Sorta like these??? products

[chris661]

Discussed here some time ago.

new idea? to eliminate need for BSC

I'm considering trying again, with some '70s 6x9 drivers, and an 8" cancelling woofer, driven by a seperate amp.

Chris

[borispm]

I think it's something like the Tekton design thing...
But will it work without any kinda filter? Without BSC and much equalization, perhaps?

[borispm]

Something like the Tekton OB, but I'm not so sure about the bass reflex design of the cancellation driver, because it DOES add resonance (and more box-sound) to the cancellation driver than a seal box will.

[chris661]

You need to low-pass the cancelling driver (a single inductor will be fine for this).
I agree that sealed is the way to go for this.

You'll need minimal eq with this kind of set-up. A design like this took a 3" driver down to 60Hz. It couldn't go loud at that, but that's where it went to. Sounded lovely. Just limited SPL (small driver, what's to be expected?)

Chris

[mondogenerator]

interesting idea....not new i guess, from what others have said, but interesting nevertheless.

With a 90 degree angle of incidence you arent going to get anywhere near total cancellation though are you? I would be tempted to try 2 OBS back to back, with the rear one (the canceller) loaded into a closed box, (or even aperiodic TL) as described by you. That way you could play with their separation distance, to see what effect that would have on FR or SQ.

Obviously for the best results, ALL drivers would need to be the same

[borispm]

Originally Posted by mondogenerator

interesting idea....not new i guess, from what others have said, but interesting nevertheless.

With a 90 degree angle of incidence you arent going to get anywhere near total cancellation though are you? I would be tempted to try 2 OBS back to back, with the rear one (the canceller) loaded into a closed box, (or even aperiodic TL) as described by you. That way you could play with their separation distance, to see what effect that would have on FR or SQ.

Obviously for the best results, ALL drivers would need to be the same

By putting two OBs together, it would be something like a push pull (isobaric loading?) design, which should work well (but I'm not sure if it is art deco friendly)

You're right, I agree that identical drivers will perform better (more consistent between the two drivers)

[borispm]

Chris661, 150Hz is my goal.
I will go for a narrower baffle of around 8" (vs Tekton's 12") and cross it via first order to a supporting sealed woofer, maybe dual SEAS Prestige CA22RNX (H1288) . Just good enough for f3=60Hz, I expect something like 30Hz-20kHz +/- 10dB.

BTW, is someone adventurous enough to give this project a try? I am not free to build such a large scale project.