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Old 7th May 2002, 05:42 AM   #1
diyAudio Member
 
Join Date: May 2002
Location: Australia
Question Help with Morel sub project

Hi ,

I'd love some help with a Sub project I want to build.
I've got 4 Morel 222 drivers available doing nothing.
The specs are as follows :
Fs=31Hz
Re=5.2ohms
L=0.5mH
Xmax=3.5mm
Qms=3.74
Qes=0.95
Qts=0.75
Vas=70litres
Cone=219cm2
Power=120W
Z=8ohm

When I plug the figures into my software it suggests ridiculously
large enclosure sizes >1000litres ??

Can anyone suggest an enclosure design utilizing these drivers
sealed/bass reflex/bandpass.....I don't mind. Good low bass , but
not "boomy" for use with HT & Music.

Thanks
Andrew
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Old 8th May 2002, 04:42 AM   #2
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Join Date: Apr 2002
Location: Baltimore
With that kind of Q, go for a sealed box
When Qc = 1.25, box volume is 3.5 ft3.

If you do a compound woofer configuration, the box will have two woofers in it and be 1/2 original enclosure size, 1.75 ft3. Efficiency will be that of a single woofer (assuming a 4 ohm parallel connection).
-andy

btw, if you can make it any larger than 1.75, i would recomend that you do so
I've never done anything with woofers with that high of a Q value, if anyone has any other suggestions please share.
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Old 9th May 2002, 06:10 AM   #3
Wizard of Kelts
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Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Okay, here are some suggestions.

Four boxes of different configurations. Two are 2 cu ft,
two are 3 cu ft.

Red. 3 cu ft. Closed box. Least output of the four.

Orange. Bandpass. 3 cubic ft total. 1.5 cu ft front chamber, 1.5 cu ft rear chamber. Tuned to 48 Hz.

Lt. Blue. Bandpass. 2 cubic ft total. 1.2 cu ft front, .8 cu ft rear. Front tuned to 60 Hz.

Dark Blue. Bandpass. 2 cubic ft total. .7 cubic ft front. 1.3 cu ft rear. Front tuned to 48 Hz.

Note that the bandpass boxes exhibit higher sensitivity and/or bass extension than the sealed.

Except for the dark blue, the depressions in the middle are not so unmanageable-2 or 3 db. Bear in mind that when a bandpass is near a corner, the tuning frequency is emphasized most of all, and that will fill in the middle depression.

The front chamber can also be tuned with a 10" or bigger passive radiator.

If you want less than 2 cubic feet, let me know,
but you are not going to get anywhere near 30 Hz output if it is smaller than that.

I have never built a bandpass box, but with the extra output it seems to put out, I plan to soon. I have also never used a passive radiator, but I understand the principles. I have built plenty of sealed and ported enclosures.

The graphs are only there to give you an idea of some possibilities.

Good luck!!
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File Type: png morel 22.png (6.2 KB, 143 views)
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Old 10th May 2002, 02:36 AM   #4
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Join Date: May 2002
Location: Australia
Found some more information which may help someone to help me !
The drivers were used in a Morel model MLP307 , 2 wired in parallel in a box with total of volume ~ 45 litres.
Each driver had it's own compartment of ~ 22 litres and each
compartment was rear vented with a aperedic?? port (not sure how to spell it) - (not a bass reflex port !)
These speakers had good low down performance , that's why I
thought of using these drivers.....

My "Spouse Factor" concludes that my sub needs to be built under
the coffee table , so I've got about 92 litres to play with.
So I'm trying to make the best of the available drivers & room space.

Many Thanks
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Old 10th May 2002, 05:29 AM   #5
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Well, I don't know that much about aperiodic vents, but here is a page that explains things:

http://www.snippets.org/ldsg/boxes.php3#APERIODIC

Frankly, I think I would use one speaker in a 3 cubic foot bandpass enclosure, but that's just me.

I have seen other aperiodic designs using 2 chambers but have no link. I will post the link if I come across it.

Good luck.
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Old 11th May 2002, 02:29 AM   #6
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Join Date: Apr 2002
Location: Baltimore
Default aperiodic vents

damp resonance impedence the same way adding 100% fiberglass fill does, according to Vance Dickason. This increases the effective size of an enclosure.

Do you plan to use all 4 woofers?
the bandpass idea is feasible, only large. How would the compound woofer setup compare soundwise? Could one design a coumpound woofer bandpass sub? I will see if I can find out.
andy
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