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How not to build a 2 way MEH.

SDC

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I thought it would be good idea to build MEH out of 2384 which is easily available on the net.

So, without any simulation, just pure guessing I go.

Lets see how this ends...



driver used is 4inch and 6.5inch.

So I have large margin for errors.

the seam on the horn is my guide line for holes,

I'll drill right on the seam and measure FR.
 

kipman725

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skeptical of the pureifi woofers in this application, whats your intended crossover?
 
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voodooless

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I would probably put those rings even closer to the throat? The rings will also make for quite a bit of volume underneath the cone. You’ll probably need to fill that up again.

Looking forward to see where this ends :cool:
 
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SDC

SDC

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skeptical of the pureifi woofers in this application, whats your intended crossover?

Anywhere above 500hz. Woofer was selected not by parameter just my preference. If it fail it is just a pair of horn wasted units can be used for other applications.
 
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SDC

SDC

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I would probably put those rings even closer to the throat? The rings will also make for quite a bit of volume underneath the cone. You’ll probably need to fill that up again.

Looking forward to see where this ends :cool:

Then I can't remove the CD so close as I get I'm afraid.
The space was intended for purifi's excursion but donno whats gonna happen. No hornresp no sims just doing it.
 

Joe BKNY

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Lurking acronym-deficient member asks what does MEH stand for. If H stands for horn do I get partial credit?
 

voodooless

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The space was intended for purifi's excursion but donno whats gonna happen.
Just fill it up to follow the cone shape. Something like this:

1659706619300.jpeg
 
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gnarly

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Nice project. Looking forward to how it turns out.

I bought a 2384 for the same idea. I figure anything 8" and under fits on the top and bottom flats, after milling the ribs off.
Just haven't got to it...been too busy pursuing the usual DIY wood horns.

Where are you planning on putting the ports? And what size area vs Sd?

I've played with this a bit....have done like voodooless showed, with ports out toward the surround and filling in under the cone....and have done ports directly under the center of the cone, with no fill in.

If the CD reaches low enough so that ports don't need to be real close to the throat, I've found I like the "center under cone" method best.
It has smoother response and goes a litter higher (without needing filler between cone and horn).
Extends low end response a little too, being further out in the horn.
Disadvantage is ports in the middle of the horn supposedly disrupt CD flow more than in the corners, but my experience has been mouth termination matters more than any of that. (which is why the 2384 is appealing, huh? :))

Here's a few of the builds I've tried.
Second pict is the middle one before flares glassed and painted, so the center port under cone shows better.
The secondary flares were cut to match a K-402 as best as possible.
3 syn a.jpg


foam2.jpg
 
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SDC

SDC

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Nice project. Looking forward to how it turns out.

I bought a 2384 for the same idea. I figure anything 8" and under fits on the top and bottom flats, after milling the ribs off.
Just haven't got to it...been too busy pursuing the usual DIY wood horns.

Where are you planning on putting the ports? And what size area vs Sd?

I've played with this a bit....have done like voodooless showed, with ports out toward the surround and filling in under the cone....and have done ports directly under the center of the cone, with no fill in.

If the CD reaches low enough so that ports don't need to be real close to the throat, I've found I like the "center under cone" method best.
It has smoother response and goes a litter higher (without needing filler between cone and horn).
Extends low end response a little too, being further out in the horn.
Disadvantage is ports in the middle of the horn supposedly disrupt CD flow more than in the corners, but my experience has been mouth termination matters more than any of that. (which is why the 2384 is appealing, huh? :))

Here's a few of the builds I've tried.
Second pict is the middle one before flares glassed and painted, so the center port under cone shows better.
The secondary flares were cut to match a K-402 as best as possible.
View attachment 222561

View attachment 222563


Wow, amazing works! I'm planning two hole near the edge.
As you know 2384 don't load the CD well considering it's 30inch size, so higher than 500hz is acceptable but 700hz is best IMO.

And I can't drill holes larger than 32mm by the lack of tools right now. So two holes it goes.

If measurement shows your suggestion more appealing I might by a new 2384 to do it all again but for now I'll stick as planned.
 
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SDC

SDC

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drilled 4 holes ctc 10cm square. 32mm each

Think it is usable to 600.

Need to build a case for it to continue but have no idea right now. Didn't think I'll make it.

BTW mechanical low pass is really weird experience. There is this really steep filter I can't imagine how and why, it's just there.
 
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gnarly

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drilled 4 holes ctc 10cm square. 32mm each

Think it is usable to 600.

Need to build a case for it to continue but have no idea right now. Didn't think I'll make it.

BTW mechanical low pass is really weird experience. There is this really steep filter I can't imagine how and why, it's just there.

By 4 holes, i take it you mean two per driver......right?
I think two 1.25" holes like you did is about perfect for a 6.5" driver. Gives a little over an 8:1 compression ratio, which has worked well for me on whatever size cone I've mounted on a syn horn.

BTW, which Purifi model did you get? I looked at one and the funky surround ridges look like they protrude 6+mm.
Is that causing a mounting problem and the reason for the mounting rings? ( I'm another one of the guys wondering how well suited the Purifi is.....)

You might want to try it without a case.
My current synergy has 4" mid drivers to bridge between the CD and 10" lows.
I've tried it with the 4" sealed in a box, and open like shown in pict, and prefer the open. (This is with identical looking mag and phase traces.)
But my 4" mids are only being used from 300Hz to between 750-1000Hz. So I have no clue what open back lows would do (as my 10"s are enclosed )

And yes! the mechanical (or acoustic) low pass is neat huh?
Minimizing the volume between the cone and horn, both raises its low pass frequency and steepens the low pass order some.
I like when the acoustic low pass kicks in right above the notch frequency.
I've found notch frequency, the 1/4 wavelength distance, measured from the cones' ports to the CD mounting flange, to be pretty accurate in forecasting the notch frequency.
My guess is the ports you described have centers about 4.5" from the CD ....? If that's right, I'd think you'll get the reflection notch at about 750hz...
If after the notch, the acoustic low pass kicks in, you have it made ime/imo

Good luck. Eagerly awaiting some measurements :)

syn10t mids.jpg
 
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SDC

SDC

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By 4 holes, i take it you mean two per driver......right?
I think two 1.25" holes like you did is about perfect for a 6.5" driver. Gives a little over an 8:1 compression ratio, which has worked well for me on whatever size cone I've mounted on a syn horn.

BTW, which Purifi model did you get? I looked at one and the funky surround ridges look like they protrude 6+mm.
Is that causing a mounting problem and the reason for the mounting rings? ( I'm another one of the guys wondering how well suited the Purifi is.....)

I used two 6.5x08-naa aluminum long stroke per side.

with quick and dirty measurement I see high 2nd harmonic under 200hz so using purifi for exceptional mid lows are likely not going well.

Measurements done properly enough to post will take some time. But it will happen, my room is just not yet ready.
 

Lbstyling

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Considered doing this, so have the popcorn out!!
truExtent tho.... Ouch!
 
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