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Multi-Way Conventional loudspeakers with crossovers

Exploring Purifi Woofer Speaker Builds
Exploring Purifi Woofer Speaker Builds
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Old 20th September 2020, 12:07 AM   #441
xyvyx is offline xyvyx  United States
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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.
Click the image to open in full size.

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?
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Old 20th September 2020, 01:39 AM   #442
xrk971 is online now xrk971  United States
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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?
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Old 20th September 2020, 01:31 PM   #443
hallcon83 is offline hallcon83  United States
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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?
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Old 20th September 2020, 01:41 PM   #444
xrk971 is online now xrk971  United States
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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.

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Old 23rd September 2020, 03:10 AM   #445
hallcon83 is offline hallcon83  United States
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- 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?
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Old 23rd September 2020, 03:43 AM   #446
JimM is offline JimM  United States
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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.
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Old 23rd September 2020, 03:46 AM   #447
Octavia is offline Octavia  United States
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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.
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Old 23rd September 2020, 03:52 AM   #448
JimM is offline JimM  United States
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VISATON list their 25mm tweeter's G25FFL-8 and KE25SC-8 compactable with the WG 148R waveguide, any one know anything about Visaton tweeters?
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Old 23rd September 2020, 04:56 AM   #449
xrk971 is online now xrk971  United States
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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.
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Old 23rd September 2020, 07:08 AM   #450
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Quote:
Originally Posted by xrk971 View Post
Ask for dope and ye shall receive dope...
Awesome! Subbed to the thread! If it turns out okay, I'll make them my next build for sure!
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