These will be the midrange drivers in a 3 way, with RS270P-04 woofers in bass bins and Peerless DA25TX00-08 corundum dome tweeters to round out the project.
The aperiodic vents are not being used at all to change the bass response, as these drivers will likely be crossed over in the 400-500 Hz range. They were basically free to make and will suppress the huge impedance peak at 49 Hz, thus making the passive highpass crossover easier.
Found this as an alternative slicing method:
It appears to create “tabs” of sorts. I wonder if the tab does much like a damper itself, or if it is just the geometry change that breaks up the resonance as it travels across the cone.
Good call on the Rs270p. I am still tweaking on my 4-way project using one and even using fancy expensive drivers for mids and highs, the Rs270p stands out to me as the star of the show. It’s crossed really low (150ish) in a big cab (1.75ft3) The bass is just solid and musical. Sure they could dig a little deeper or have a little more throw, but they sound so good as a woofer. Better than they should for what they are. Despite the flat back plate and modest motor size, I’ve never bottomed it either (which I understand to be a thing with Rs225s). Probably the best quality bass I’ve personally ever had in a home speaker.
I used them originally in my RSX, which these are a modification of, and I remember one of the mwaf judges commenting about good bass as well. The bass quality didn’t stand out to me as much in those because they were stretched to their limits in every way possible in that build, but it was noticed then too.
This is a cool build, I love the driver mods. I commend you, I don’t think I would have it in me to be able to plunge a blade into a moderately pricey driver lol.
Do you have any before and after measurements?
Forgot to ask. Is the duct cap really needed? It looks like a mesh
Disregard on the measurements question, I just read the original JBrunner thread. Impressive feedback from the Vapor guys.
yeah the Vapor guys had good ears
I second this question. Though it seems the dust cap is using the same kind as those “sonically transparent” ones used on some coaxial PA drivers. Removing it would lower the mms some, but the adhesive/damping added for sliced cone probably adds some back anyway. Don’t know if a dust cap would add any stiffness to the inner portion of the cone. But I’d bet just leaving it off with a filler/extension/plug in its place would be fine. I had wondered if there was a size of copper pipe and cap that would fit well. Fill it with something to make it sonically dead.
I’ve always wondered about those mesh dust caps too. Not enough stiffness to add any rigidity to the cone. And since they are mesh, dust is going to get in the gap. I suppose it keeps bigger stuff out, like pet hair.
Many drivers back in the day used porous dust caps, it allowed ventilation of the voice coil. This is before under spider and vented backplates became the norm.