mmm.. beefy. So I was fiddling with WinISD and it lead me down this path. "Why not go with an external port?" a friend suggested.
Turns out, tuned to 35hz, you'd need a ~ 25" long port at 3" in diameter. Same height as I'd use for some stands. So I abandoned my idea for an internal, 3D printed port/flares and got some aluminum pipe. It didn't list the OD or thickness, but as it turns out, Schedule-40 aluminum pipe in this size is 1/4" thick. So yeah... beefy.
I'm gonna try to make the way I attach it to the bottom of the box sorta "modular" so that I could maybe try a slot-load something something in the future. We'll see.
So.. am I missing something? is a big, long port w/ this smallish driver dumb?
Audio stuff - Album on Imgur
An externally hosted image should be here but it was not working when we last tested it.
Turns out, tuned to 35hz, you'd need a ~ 25" long port at 3" in diameter. Same height as I'd use for some stands. So I abandoned my idea for an internal, 3D printed port/flares and got some aluminum pipe. It didn't list the OD or thickness, but as it turns out, Schedule-40 aluminum pipe in this size is 1/4" thick. So yeah... beefy.
I'm gonna try to make the way I attach it to the bottom of the box sorta "modular" so that I could maybe try a slot-load something something in the future. We'll see.
So.. am I missing something? is a big, long port w/ this smallish driver dumb?
Audio stuff - Album on Imgur
You should make your port smaller dia and shorter. The problem with a 25on port is that it is long enough to have pipe harmonics and 1/2 wave is 270Hz - right in your critical mid bass region, and the 1/4wave is 135Hz right at your upper bass where “slam” is felt. A more reasonable length is say 7in or 9in. Or just use a passive radiator. There’s a reason vents aren’t not 2 ft long (except on huge car audio subs where they low pass it at 80Hz).
Also, it makes no sense to spend so much money on thick wall 25in long aluminum pipe. That’s pricey stuff when a PVC pipe will work just as fine. It’s internally hidden right? It’s not providing structural support is it?
Also, it makes no sense to spend so much money on thick wall 25in long aluminum pipe. That’s pricey stuff when a PVC pipe will work just as fine. It’s internally hidden right? It’s not providing structural support is it?
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Hi xrk, your the man ...... I have a question , I'm having a hard time figuring out what your dipole or dual Purifi Mid-woofer TL would look like , could you draw what you meant when you described adding the second Purifi woofer and changing your TL design to tall version for me?
This is a markup of the TL for an RS225-8, but it would be very similar in look and size to what I had in mind for how to do a bipole PTT6.5 TL. I would use a waveguide loaded dome on the bottom just like how I have it now and use the passive Harsch XO for a transient perfect speaker. The XO and TL design would have to be tweaked of course.
Attachments
- Hi xrk, Thank you for the help , now I understand what you were talking about, a drawing really helps - would you put some kind of support between the two drivers , a pole or something to help cancel out vibrations? - I was also wondering ,do thing that would lower the bass frequency cutoff like down to the low 30's - high 20's?
Mouser Electronics list VISATON Waveguide WG 148 R, does any one know what tweeters will fit the WG 148R? They are listed for around $15.00 u.s. each and appear to be 148mm diameter. Possible waveguide for use on XRKaudio build.
Seems the Purifi Woofer has such a smooth roll off that it could be allowed to run full range with a minimalist tweeter crossover around 3-4K.
VISATON list their 25mm tweeter's G25FFL-8 and KE25SC-8 compactable with the WG 148R waveguide, any one know anything about Visaton tweeters?
As long as the waveguide fits around the tweeter you have in mind, an adapter can be made for it. Sort of like what I did for the RS28F and Monacor WG300.
@hallcon, yes a brace made of a strip of 3/4in ply between the two magnets would be useful. Although the opposing cone motions will cancel out vibrations. The bass extension has to do with the TL length and taper ratio. The extra woofer will give more SPL and the bipole will reduce the baffle step loss and so in effect, increases the F3 bass extension deeper.
@hallcon, yes a brace made of a strip of 3/4in ply between the two magnets would be useful. Although the opposing cone motions will cancel out vibrations. The bass extension has to do with the TL length and taper ratio. The extra woofer will give more SPL and the bipole will reduce the baffle step loss and so in effect, increases the F3 bass extension deeper.
Awesome! Subbed to the thread! If it turns out okay, I'll make them my next build for sure!
Looking at the specs of the original LX Mini driver, Seas L16RN, I'm now wondering if there is much to be gained with the Purifi driver... ?
Regarding the bi-polar construction as shown in the drawing: At low frequencies it will work as expected. But at mid frequencies there have to be constructive/destructive interferences between "front fired" sound and soundwaves that originate from the back driver, "wrap" around the enclosure and then also propagate forward.
I have not yet... as I have sold my PTT6.5 and RS28F Waveguide TL's to my cabinet maker (he liked them too much to give them back after a loan to audition them). 🙂 I need to order another set of drivers from Madisound and get a another cabinet made. But can also try it with the Heils once I get another set of drivers in-hand.
Well, about the Raven "called" point source, I have yet to see some polar plot in both horizontal et vertical plane...
Thanks for the tip on the Raven. It looks interesting. I have a RAAL and a 3d printer does might try something like this. I have tried a deeper tractrix and there was too much destructive interference dips. But a shallower design like this maybe interesting. Although won’t give me the deeper physical setback I was looking for.
Oh no, hallcon83 how could you do this to me?
There I was minding my own business enjoying the advent of fall colors and coolness secure in the knowledge that Raven ribbon tweeters had joined the likes of Sony APM square woofers (About the amazing Sony APM-66ES – Sound Oddity – Blog !) categorized as endlessly fascinating HiFi unicorns passed from the realm of mere mortals onto the dream land of the unobtainium. You know, too bad they didn’t make it as a business but at least my HiFi budget is safe from the lusts of my heart.
And now you alert me to the continued availability of Raven ribbon tweeters. Hooray for another Made in USA HiFi company serving the lunatic fringe hanging in there through 2020. I see the pricing is also still OUCH. I only heard a Raven tweeter once, local high-end auto audio shop had the Ebb (Raven’s parent company ORCA used to import Focal drivers that were SOTA in automotive high-end back in the day). I recall it living up to my high expectations. Alas no clue how it would compare to SOTA circa 2020. The engineer designer side of my brain can’t help note I was just quoted $212 each for the new Mundorf AMT U40W1.1. So call it $450 pair landed vs $800 pair for the Raven Point Source. My head says Mundorf, the heart (or wherever audiophile lust is seated) says lets scratch the Raven itch.
Note 1: Acronym SOTA used above signifies State Of The Art.
Note 2: Recounting hearing the Raven Ebb it occurred to me that audition was also the first time I sat down to listen to HiFi and was handed a tablet and told “scroll ‘til you find what you like, tap, and it will play; use that slider to control the volume”.
There I was minding my own business enjoying the advent of fall colors and coolness secure in the knowledge that Raven ribbon tweeters had joined the likes of Sony APM square woofers (About the amazing Sony APM-66ES – Sound Oddity – Blog !) categorized as endlessly fascinating HiFi unicorns passed from the realm of mere mortals onto the dream land of the unobtainium. You know, too bad they didn’t make it as a business but at least my HiFi budget is safe from the lusts of my heart.
And now you alert me to the continued availability of Raven ribbon tweeters. Hooray for another Made in USA HiFi company serving the lunatic fringe hanging in there through 2020. I see the pricing is also still OUCH. I only heard a Raven tweeter once, local high-end auto audio shop had the Ebb (Raven’s parent company ORCA used to import Focal drivers that were SOTA in automotive high-end back in the day). I recall it living up to my high expectations. Alas no clue how it would compare to SOTA circa 2020. The engineer designer side of my brain can’t help note I was just quoted $212 each for the new Mundorf AMT U40W1.1. So call it $450 pair landed vs $800 pair for the Raven Point Source. My head says Mundorf, the heart (or wherever audiophile lust is seated) says lets scratch the Raven itch.
Note 1: Acronym SOTA used above signifies State Of The Art.
Note 2: Recounting hearing the Raven Ebb it occurred to me that audition was also the first time I sat down to listen to HiFi and was handed a tablet and told “scroll ‘til you find what you like, tap, and it will play; use that slider to control the volume”.