With a woofer FAST those little 3.5in drivers sound quite rich and full. Better than a traditional 8in woofer with a 1in dome tweeter XO at 1800Hz. Having the 500Hz to 5kHz covered by a wide band cone sounds so much better than a little dome from 1.5k to 2k up. The 1in dome tweets lack the Sd to make convincing mids below 5k.
Picked up a pair of 10F 8424 drivers this morning, swung by the hardware store and bought a length of 4" PVC per Bob Brines then visited a friend who has a CNC router.
Cheers, Mack
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Cheers, Mack
Maybe you meant to mount this whole assembly behind a baffle. But you need a flat rectangular or trapezoidal baffle. Don't leave it round on the end of a cylinder. That's the worst shape for diffraction and you will turn the 10F, the flattest response driver into a big rippled response driver.
Look at the example with a round baffle from SL.
Diffraction from baffle edges
Look at the example with a round baffle from SL.
Diffraction from baffle edges
I see that round is the worst... I would have been baffled if these highly rated speakers didn't sound superb.... I would be baffled because the 10F 8424 weren't?
Is there a baffle calculator? I notice the small Pluto drivers don't have baffles, does Winkwitz use DSP to compensate for no baffle step?
Can anyone suggest the dimensions for a rectangular baffle? How 'bout teardrop shaped? The 8424 is Xed at 350hz.
Thanks! Mack
Mack,
How will the plywood mounts be secured in the PVC pipe? Did you size if for a press fit, or did you plan to glue it or otherwise secure it in the pipe?
I was really interested to see this, because it looks a lot like how I was thinking to mount the drivers for a project I'm just starting. My idea is to make an "adjustable" TL using PVC pipe and fittings.
Thanks,
Eric
Eric, I'm planing on cleaning and lightly sanding the inside of the PVC and epoxying the ring in. Undecided on how to treat the outside, maybe copper spray paint. Plywood will be sanded and varnished/oiled with whatever I have on hand.
Have noticed its a work in progress 🙂 but at IR/SR plot it looks there is mismatch somewhere in device chain for polarity MW verse MT, if target is a Harsch XO as mentioned in post 12 slope for MT looks off in it show more as a BW4 than BS2 slope. If it's a help attach a zip folder with target slopes for HARSH at either 300Hz or 500Hz, its IR-wav files that is easy import into REW for use in "Overlays" or "All SPL" window and then offset SPL to real speakers live measurement sensitivity. After some learning over at Rephase thread and confirmed by some simulated studys have in target files incorporated system stop bands set as BW2 25Hz / 17kHz, it makes a change in phase per pass-band target but also visible in frq domain as a light knee around 30Hz area for MT slope.
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Ah, well, er....
What's happening is that I really can't cross the 10F that low. The roll-off starts at BS2, but it quickly catches up with the natural roll-off of the driver which is essentially loaded IB. So, the two roll-offs add up to 4th order. I am going to have to go up, probably to 500Hz to prevent this.
Thanks for the target files. However, I can create these by tracing the target in the nanoDIGI.
Bob
That's where I ended up at 500Hz xo with 10F to hit the target 2nd order Bessel acoustic. Electrically was 1st order Butterworth at about 700Hz and the natural roll off adds up to be equivalent to 2nd order Bessel at 500Hz.
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