Help with the MHB-46

Hi guys,
I'm building a stack of 4 MHB-46, i'm now testing 2 boxes with 2 RCF LF18G401 with a DBX 234 XS Crossover and a t.amp Proline 3000

The boxes are in parallel so the cones are near to the maximun handling power...

The boxes are ok (maybe) i followed the project, but the first test wasn't a success...

I tryed to give an high pass filter to 40 hz and a low pass to 200 hz and the box was pushing air more than a big fan, whit the low frequency out to the reflex and the kick from the horn... BUT there are really big farts from the throat... it's unbelievable, i tryed all the things i know for try to remove the distortion (remember this was the first try to build speakers )

The only thing that work good but far from a perfect sound is to put the low pass to 70-80 hz.. But if you stay in front of the horn you can fell the distortion...

It's like if there was not enough space in the throat for the big moving mass of the cone, but the measure are ok! i don't know what to do, the box is perfectly sealed there are not leaks of air.. there is no damping material in the reflex camber..

I surrender, I need advice from people who know their stuff: D

Thanks and have a nice day.
Bye bye Canduz.

Ps. sorry for my bad english and many thanks for the site, projects and forums!!!

Hi Canduz, a little presentation please !

For MHB46 :
35 Hz 24dB/oct Butterworth High Pass and loss pass 100-120 hz BUT24
Have you a limiter on the DBX 234 XS ? for the LF18g401, 600 W rms is ok not more !

For more informations, i think that Marco could response you.

Hi, LIAMDJ
thank you for your answer!

I have tried to make a post in presentations but the forum open a window with no text, even after loading... i don't know if it's a problem of my computer/connection or just of the forum, i will try again later

By the way, so you think that the (BIG) distortion is because the crossover have a wrong filter? (DBX 234 XS uses a linkwitz riley 24db/oct)
Is it possible that such a slight difference in the curves of the filter can generate such a large distortion?

I'm just asking because is from 2 months that i'm studying on my own from internet and maybe this is too much complex for a newbie

I have not yet the limiter, but i found a guy who sell a compellor 320 at 180 € not far from me and maybe the next week i will buy it!

For now i'm testing the sound with a little 2 channel mixer, an aphex exciter, the dbx 234 and then the amps!

Is it possible that the box is not so strong, even if i used poliuretanic glue and 5 mm screws in all the panels?

The wood is 18 mm (13 layers) plywood

EDIT: [Vous devez être inscrit et connecté pour voir ce lien]

I tryed to give an high pass filter to 40 hz and a low pass to 200 hz and the box was pushing air more than a big fan,

You must cut lower : 100 to 120Hz. 200 Hz is too high.

It's like if there was not enough space in the throat for the big moving mass of the cone,

No it's a large throat : 800cm2, the martin WSX is 544cm2.

You're the first one reporting distorsion.

You must try lower cuttoff, buy a limiter, or digital processor with limiter, your amp must never clip. If you see clipping: it's not good !

Try this and see what it make's

I found the problem!
The boxes are bad builded...
The throat is vibrating too much... maybe i did something wrong in the costruction..
The amp wasn't clippig, i tried to cutting off around 100/120 and in fact it was playng better.. but still crap...

The projects are perfect, i'm the only one who report distortion because this is my first test to build some boxes!

Thank you for the help! I will try to build it again better whit better wood and give my report

See you! Bye!!

The box must not vibrate, something wrong in your construction yes. Try a low frequency generator like the one in REW (Room Eq Wizard) You can generate a sinus and ear easily where the box vibrate. Then add screws, glue, brace, where it needs.

Thank you for the help!
I will try!