3 WAY design WMTM (opinion needed)

[sabry]

Hi guys,

I need your help, i'm currently designing this cabinet, i already bought all the speakers except the 12" woofer on the side.

I'm using two HDS PPB 134 and one Fountek NeoCD2.0 for the tweeter.
The distance between the acoustic center and the midwoofer is about 127mm, i would like to design the passive filter using a 3rd or 4th BW or LR slope.
I was thinking to cross the 12" at 80 and the midwoofers at 2.5K but i'm not sure.
I would like to know which crossover frequency to choose?
I'm searching a good sounding 12" woofer with a sensivity of 92 93 db.



Thanks in advance for your help.

Sabry

[PeteMcK]

Troels crosses over the HDS 134s at ~3Khz, & 2.5 is what the manufacturer recommends for the Fountek, so it should be OK;
at the low end it depends on how you're dealing with baffle step, the simplest solution is to cross the woofer over at the baffle step freq, in your case ~ 575Hz

Don't limit yourself to 12" drivers - there are plenty of 8 & 10" drivers out there with good low end performance, and you'll probably find that their lower Vas makes it easier to get an acceptable sized cabinet

[tinitus]

wonder if anyone ever tried slightly different crossing on each mid driver, to tweeter

[chlorofille]

Hi,

Use L-R 4th order @ 3000Hz and 80Hz. Due to your side firing woofer, you cannot cross it too high as the upper bass might become localized. Bear in mind that you'll need huge inductors for the bass crossover

For the woofer I'd use a Fostex FW305 - 95dB SPL. The huge inductors you'll need to use will suck the life out of the woofer so the bonus sensitivity is a good thing !

IMO your design requires very high quality midwoofers which can handle the upper bass very well. If not , they will start sounding thin.

[tinitus]

no low cut on midwoofers

active dsp on woofer

woofer?
CSS TRIO8 from USA, "affordable" and no problem to import 4 woofers, 2 each speaker
I do not know it, but for the money I doubt you find better

[sabry]

Originally Posted by PeteMcK

Troels crosses over the HDS 134s at ~3Khz, & 2.5 is what the manufacturer recommends for the Fountek, so it should be OK;
at the low end it depends on how you're dealing with baffle step, the simplest solution is to cross the woofer over at the baffle step freq, in your case ~ 575Hz

Don't limit yourself to 12" drivers - there are plenty of 8 & 10" drivers out there with good low end performance, and you'll probably find that their lower Vas makes it easier to get an acceptable sized cabinet

I was not sure about the crossover frequency because the distance between both midwoofer is almost 10" and i'm supposed to cross it lower then 2k to avoid bad lobing (d'appolito theory) but that's my first MTM design, so i don't know how if it will be ok with a 3K HPF.

I have a volume of 80L for the woofer, i don't want use a fat 12" subwoofer, i would like to find a woofer that goes to 30hz but without comprise in sound quality.

[sabry]

Originally Posted by tinitus

wonder if anyone ever tried slightly different crossing on each mid driver, to tweeter

In fact, in the PA professional field, a lot of engineers cross differently both midrange, one is cross at the same frequency as the tweeter, and the other one is cross lower depending on the distance between both mid's.
But, i would like to do it as good as i can, that's my first HIFI cabinet, so i need your help for the desing.
I can change the design from MTM to MMT.

[sabry]

Originally Posted by chlorofille

Hi,

Use L-R 4th order @ 3000Hz and 80Hz. Due to your side firing woofer, you cannot cross it too high as the upper bass might become localized. Bear in mind that you'll need huge inductors for the bass crossover

For the woofer I'd use a Fostex FW305 - 95dB SPL. The huge inductors you'll need to use will suck the life out of the woofer so the bonus sensitivity is a good thing !

IMO your design requires very high quality midwoofers which can handle the upper bass very well. If not , they will start sounding thin.

It will be 2 way active between the woofer and the mid, passive between the mid and the tweeter. I will cross it with digital processor like the Dolby lake.

i will check the fostex, thanks for the advise

[sabry]

Originally Posted by tinitus

no low cut on midwoofers

active dsp on woofer

woofer?
CSS TRIO8 from USA, "affordable" and no problem to import 4 woofers, 2 each speaker
I do not know it, but for the money I doubt you find better

I will use a DSP processor between the 12 and mid's, passive crossover between mid's and the tweeter.

[chlorofille]

Ahh I see. You're using active on the woofers !
I wanted to suggest a good old Peerless XXLS 12'' but that probably will be classified as "fat bass". The Fostex 12'' should be quite satisfying in a 75-80L bass reflex tuned to 30Hz.

Let us know your max budget for each woofer.