Hi
I am building a pair of FAST speakers with an 8" woofer in a QWTL, and a 3.5" cone "tweeter" (Vifa/Peerless TC9FD18-08) in a sealed box.
Cabinet work is 18mm MDF.
The Vifa has a large odd shaped flange which, with my limited cabinetmaking ability, I have been dreading having to make the rebate for.
I would also have to chamfer the rear of the cut-out to allow the tweeter to breath.
Now I'm wondering if I should mount the Vifa tweeter on the inside of the 18mm MDF baffle?
To do this, I would obviously have to chamfer the outer face of the hole in the baffle.
My questions are :-
1. Is rear mounting a good idea? (It puts the tweeter's Z offset closer to the woofer's offset)
2. Would a waveguide in the 18mm MDF actually work?
3. If so, what shape would be best? With a router can cut a 45deg. chamfer, or a 15mm radius round. Both could be further shaped with sanding.
Looking at the factory SPL graph, the driver looks prety ordinary above 10kHz, and horrible off axis.
I'm hoping that maybe a small waveguide might give a better SPL than surface mounting.
However, unless I can improve the SPL (with enclosure, waveguide, Xover), I intend to add a LF filter with a F3 around 15kHz.
I'm too old to hear anything above 12-14kHz.🙁
I am building a pair of FAST speakers with an 8" woofer in a QWTL, and a 3.5" cone "tweeter" (Vifa/Peerless TC9FD18-08) in a sealed box.
Cabinet work is 18mm MDF.
The Vifa has a large odd shaped flange which, with my limited cabinetmaking ability, I have been dreading having to make the rebate for.
I would also have to chamfer the rear of the cut-out to allow the tweeter to breath.
Now I'm wondering if I should mount the Vifa tweeter on the inside of the 18mm MDF baffle?
To do this, I would obviously have to chamfer the outer face of the hole in the baffle.
My questions are :-
1. Is rear mounting a good idea? (It puts the tweeter's Z offset closer to the woofer's offset)
2. Would a waveguide in the 18mm MDF actually work?
3. If so, what shape would be best? With a router can cut a 45deg. chamfer, or a 15mm radius round. Both could be further shaped with sanding.
Looking at the factory SPL graph, the driver looks prety ordinary above 10kHz, and horrible off axis.
I'm hoping that maybe a small waveguide might give a better SPL than surface mounting.
However, unless I can improve the SPL (with enclosure, waveguide, Xover), I intend to add a LF filter with a F3 around 15kHz.
I'm too old to hear anything above 12-14kHz.🙁
One would think this problem would be solved by now. Like .stl file that you can build or have built, which allows a "bolt-on, drop-in" solution. I'm in the same predicament, only it's a 4" driver; love to get it on the back side of the baffle board. Only need a flare that "gets itself and the baffle board thinkness out of the way" of the cone's front emitted radiation.
Strangely this 3.5" cone driver has it's gasket glued onto the front of the flange.
Hi Allen
I've had absolutely zero experience with waveguides.
I have been learning VituixCAD getting ready to design my Xover once I've completed my cabinets and have tested the drivers mounted.
Is there a dedicated software for designing waveguides?
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The waveguide idea has only come about because of the problem of rebating the odd-shaped flange into the face of the baffle.
Mounting the driver on the rear of the baffle would only require a simple round hole, which hopefully can be shaped to form some sort of waveguide.
As I've said, I know nothing about waveguides, but I was also hoping that a waveguide (in the 18mm MDF baffle) might improve the response above 10kHz.
Thinking a bit more about it, I could add an 18mm "doubler" to the back of the tweeter's baffle to produce a 36mm deep waveguide (if needed).
Sometimes adding a waveguide that is not the right size can be worse than none. However if you were wanting to mount a wider range driver behind a baffle it might be possible. Have you considered radiusing the baffle? That is one rear-mounting option. On the other hand keeping a small waveguide shallow might reduce the chances that it will become intrusive.
Radiusing the baffle is exactly what I'm suggesting.
The baffle is 18mm (approx3/4") thick MDF. It would be relatively easy to cut a simple round hole, then radius it with a 18mm radius router bit.
If needed, I could add another 18mm to the rear of the baffle allowing for up to 36mm radius.
BTW, I don't mind the asthetics of a waveguide.
Since starting this thread, I've found a thread where Dan N (dlneubec) has carried out some simple waveguide tests :-http://www.htguide.com/forum/showth...ide-testing-dome-tweeters&highlight=waveguide
However, he used a compression driver, and I'm wanting to improve a 3.5" cone driver.
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hornresp can simulate that kind of radius so you can learn a little about making it larger with a thick baffle.
Normally radiusing is preferred when woofers are mounted behind the baffle and the aim is to make it have little effect.
Normally radiusing is preferred when woofers are mounted behind the baffle and the aim is to make it have little effect.