18Sound 15" and Audiohorn X-Shape 2-way build

[TulseLuper]

For example:
View attachment 527368
This is an old catalog, it's 15 years old.

Right, maybe it's fine, but my slope down to the low end looks more severe than I read here or on other similar woofers datasheets. People make passive 2-ways with woofers like this - how would that be possible?

 

[levimax]

I have some new measurements. I am confused about why there is just so little low end output here from the woofer. I might print a port with a larger diameter (this one is 4") and see if that helps.

These measurements seem as excepted for woofer output based on size of enclosure and driver specs, what lead you to believe it would be different? Trying to get enough SPL's out of a woofer to match a horn will always be the big challenge with these designs. There is never going to be situation where a 15" woofer has "reserve power and excursion" when trying to keep up to a horn down to 35 Hz.

I also notice you seem to be EQing room modes on you bass EQ? I know you have a big building for your measurements but that room is still far too small for accurate LF measurments I think. You would need to go outside and if you did the measurements would look much smoother than these I believe which would make them much easier and more accurate to EQ.

Your build quality look fantastic and I am sure you will get bugs worked out. DIY is great but when trying to build something like a JBL M2 you gain some perspective about how awesome the engineering and performance of some of these famous speakers really is. I have enjoyed following your progress.

 

[TulseLuper]

These measurements seem as excepted for woofer output based on size of enclosure and driver specs, what lead you to believe it would be different? Trying to get enough SPL's out of a woofer to match a horn will always be the big challenge with these designs. There is never going to be situation where a 15" woofer has "reserve power and excursion" when trying to keep up to a horn down to 35 Hz.

I also notice you seem to be EQing room modes on you bass EQ? I know you have a big building for your measurements but that room is still far too small for accurate LF measurments I think. You would need to go outside and if you did the measurements would look much smoother than these I believe which would make them much easier and more accurate to EQ.

Your build quality look fantastic and I am sure you will get bugs worked out. DIY is great but when trying to build something like a JBL M2 you gain some perspective about how awesome the engineering and performance of some of these famous speakers really is. I have enjoyed following your progress.

Thanks for the feedback I appreciate it. Very good to know this is normal low end response. Other than a pair of Bitches Brew open baffles, all my speakers have been 8” woofers or smaller and the frequency response there is often flat-ish to ~50 out of the box.

I have reserve power and excursion because my SPL requirements aren’t very high. This speaker is way overkill for my application. I realize the woofer is way behind the horn/CD. Trying something new to learn here.

The EQ pictured was with close mic on the woofer (less than 12” from baffle) just to see what I needed to get it flat, it’s not intended to be used in the final design. I will do the best I can to get good measurements and will not EQ peaks/dips in that range, just stick to broader contours/shelf filters. The plan is for Dirac to take care of room stuff.

You’re absolutely right that my appreciation for engineering behind M2 like speakers has increased.

 

[Elgrosso]

I have some new measurements. I am confused about why there is just so little low end output here from the woofer. I might print a port with a larger diameter (this one is 4") and see if that helps.

Here is on axis, ~18" from the baffle plus a measurement from the back side, 18" away from the port. Indoors ungated:

View attachment 527343


And here is are measurements at roughly 0, 15, 30, and 45 degrees. The falloff makes a lot more sense here than in my last set of measurements:

View attachment 527344

I finally started my build, and got similar result, but it was expected since it’s a small box (60-70L net), sealed, and the woofer has a higher Qts (even higher than on its spec).
Very quick checkup here at 30cm:

And you were right for the round overs, it’s not that hard by hand.
Well it’s not finished nor ready for paint but good enough for the next steps : measurements and validation before building either the second box or a totally different pair.

So I used a jigsaw first to remove most of the corner material, then belt sander and finish by hand.
The jigsaw was perfeclty fine for most of it, except in 2-3 spots where the blade went crazy.
These spots just gave me a lot of work to fill and sand later, more than the total time spent on cuts! I sure will pay more attention for the next box, but it works (and is way cheaper than buying a table router big enough for this kind of bits).

 

[TulseLuper]

I finally started my build, and got similar result, but it was expected since it’s a small box (60-70L net), sealed, and the woofer has a higher Qts (even higher than on its spec).
Very quick checkup here at 30cm:

View attachment 527683

And you were right for the round overs, it’s not that hard by hand.
Well it’s not finished nor ready for paint but good enough for the next steps : measurements and validation before building either the second box or a totally different pair.

So I used a jigsaw first to remove most of the corner material, then belt sander and finish by hand.
The jigsaw was perfeclty fine for most of it, except in 2-3 spots where the blade went crazy.
These spots just gave me a lot of work to fill and sand later, more than the total time spent on cuts! I sure will pay more attention for the next box, but it works (and is way cheaper than buying a table router big enough for this kind of bits).

View attachment 527684

Looks great!

 

[Elgrosso]

Not yet but I hope soon, the shape is fun but it’s more a proto, many details to fix in the next ones.
Did you start with vituix and all? I just started myself the outside measurements.

 

[Elgrosso]

Finally did some measurements outside, happy it went well as it was a first.

XO ended at 700Hz, LR8, there’s really not much to try once EQed the choice is self evident, 700-750hz were very similar depending of eq, above the DI suffered.
(steps of 11.25deg here)

Good enough for now, so I started the second box.

 

[TulseLuper]

Looks very good. Could you share more measurement details? Like mic distance, height, etc?

 

[Elgrosso]

Sure, mic at 1m, on axis with the horn, both 170/180cm high.
Rotation axis at the horn apex, so near the back of the box in this case.
Steps every 11,25 degrés, and 6ms gating

Pic of the setup, my first tentative here. The measurements I shared were done with a better mic stand but similar set.
Had to add some metisse (recycled cotton insulation) near the table edge, to fix a hole near 450hz.
Strangely a big stack of it on the floor between mic and speaker didn’t have any effect.