Which enclosure for best bass performance?

SpirosZ

Member
2013-01-18 11:27 am
I am still in the process of finding the right design for my HT using high efficiency pro drivers.
So far some of my favorites are the SEOS waveguide designs.

I am thinking about building one using the Eminence Delta 12lfa woofer but I want to get the best possible bass performance out of that driver.
Size in not a problem as long as it is not more than 45cm wide and 45cm deep (more or less).
I don't have a problem with height but I would like a design that brings the drivers at ear level when sitting.
Pi speakers uses that driver in a BR enclosure aound 105-110lt in the Three Pi speaker, Eminence recommends a BR enclosure between 25.5-102lt or a sealed at 19.8-28lt and WinISD recommends 218lt BR tuned @ 32Hz.
WinISD also gives me nice looking curves with boxes between 110-180lt tuned between 32-35Hz.
I did a few calculations for a TQWT enclosure and came up with boxes between 133-185lt
Most of them came out too deep but the smaller one looks fine with internal dimensions 86.8X38.3X41.6 (cm H/W/D) for an internal volume of 133.3lt and an f3 of 38.4Hz

If I model a box of 133.3 lt in WinISD tuned around 32Hz (using the same size port as the one in the TQWT enclosure) it looks nice with a sight downslping curve and an f3 at 34Hz and f6 at 27Hz (better than the f3 38.4 of the TQWT). .
The TQWT box is actualy just a BR box with a bracing that makes it act as a quarter wave tapped tube. What am I supposed to expect from it?
Will the TQWT design have any benefits compare to the simple BR box?
I cannot sim the response of the TQWT with WinISD and Hornresp is too complicated for me to even try a different design (it may be able to simulate the TQWT but I have no idea how).

Am I on the right track? Is there a better option that I haven't think of?
 
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Fully sealed enclosures always sound better.

Not really, the Eminence 12 Delta LFA has an efficiency bandwidth product of exactly 100 ....Putting it smack middle into the porting camp.
Running this driver in a sealed enclosure would be like having a race-horse pulling a buckboard.


_____________________________________________________Rick........
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Low Qts woofer in horn enclosure.
High Qts woofer in sealed enclosure.

Low Qts woofers tend to have weak bass, but when done properly/successfully, the quality of the bass is usually better than high Qts woofers.

Horn is the best for apparent reason (talking about single bass driver here): When you try to get the lowest octave (the bass) from a woofer, you loose the high octave (midrange) quality. Horn can restore the midrange quality while reaching the lowest octave (can be through big horn which is best, or through transmission line)
 
Me thinks that is a matter of the crossover, which hasn't been investigated yet.
You just choose the passband then try to linearize it :eek:
Not to mention that a real hi-fi project needs to be 3 way, 'cos efficiency is dictated also by driver's diameter related to the frequency to be reproduced.
 

SpirosZ

Member
2013-01-18 11:27 am
Me thinks that is a matter of the crossover, which hasn't been investigated yet.

I plan to use a ready design from diysoundgroup https://www.circuitlab.com/circuit/w3863p/seos12-delta12lfa/

Not to mention that a real hi-fi project needs to be 3 way, 'cos efficiency is dictated also by driver's diameter related to the frequency to be reproduced.

Idealy I should be using a subwoofer but with a 12" 96db/w/m midbass I will probably need a couple huge 18" subwoofers that I have no room for. Therefore I will have to live with out a sub for the moment.


What I cannot figure out is how bass performance affects mid-highs. It doesn't look right to me and I don't think it's true.
 
Yes it does make sense, and also Jay seems very sensible in writing about speakers & Co. :)
You can watch the problem from various points, from the excursion POV or by the diameter, or by the efficiency as I told you ( me very humble & ignorant!).
Taking the excursion row: if the woofer is 'pumping' for reproducing the very low frequencies, imagine and guess what it can do to reproduce the mids...in the spare time :p ( modulation issue)
For the diameter : it's called 'pistonic range' and it's very narrow, determined
by the diameter and stiffness of the cone; outside its pistonic range, the speaker ....:confused::D
For efficiency, you can derive from the freq response data of the manufacturer
and see what application could do a good job; you won't use it as a sub but for mid-wf application, then you can count on room gain .
I'd say why not ? TQWT or ML-TQWT ...but remember efficiency after you put it in the box and after filtering.
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
How is that happening?

I think it is due to how the cone has to move the air to produce low and high frequencies at the same time. It is always better if the driver has to produce limited frequency band only (sound is clearer and less muddy).

This is especially true when a small diameter woofer is "forced" to produce low frequencies with the help of enclosure. Here we will notice compromise in sensitivity, hence mid-range sonic. The bigger enclosure (especially vented) and the required stuffing will absorb some energy.

Many horn designs are actualy transmission line with extra horn to produce the mid-range. With horn shaped waveguide, less cone energy is required to push the air (to certain spl). This is where horn wins over classic TL.

Another way to restore the midrange (while also producing the lowest octave) is by putting the woofer in a shallow depth a-la MLTL. I like MLTL because basically it is a bookshelf (known with its good midrange) with a little extra bass extension.
 
It is always better if the driver has to produce limited frequency band only (sound is clearer and less muddy).

Correct, I always preferred the sound of a three way than a two way.
A good three way sounds always more detailed in bass and low mids.
If you choose the crossover points at around 250-3000 the midrange can cover the most part of the human voice, and the mid can work in his frequency band with the least distortion.
If you look at the distortion plots of drivers, you'll see the highest distortion is in the bass.
So for a two way the bass/mid must also work in the frequency band with the highest distortion: no good for your mids.
 
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Yes I understood that :)
The fact is that we are talking what happens to the back wave, not the front one
(indeed.....:) )
If the walls of the enclosure are not parallel, that's even better !
But it's not easy to make the enclosure ( only if you have access to a CNC router and have designer abilities to program the machine)

Looking at the crossover, well, I expect the whole 'thing' to have a little less sensitivity than the 96 dB/W/m.
The suggested BR box would then EQ the low end, by adding the reinforcement that comes out of the reflex duct.
 

SpirosZ

Member
2013-01-18 11:27 am
Correct, I always preferred the sound of a three way than a two way.
A good three way sounds always more detailed in bass and low mids.
If you choose the crossover points at around 250-3000 the midrange can cover the most part of the human voice, and the mid can work in his frequency band with the least distortion.
If you look at the distortion plots of drivers, you'll see the highest distortion in the bass.
So for a two way the bass/mid must also work in the frequency band with the highest distortion: no good for your mids.

I have decided that I will go with a constant directivity design.
That means midrange and tweeter directivity have to match precisely.
Usually those designs have crossover frequencies between 700-2500Hz depending on the midrange size.
One of my plans was with the Delta12LFa, Beyma 6MI90 midrange and SEOS6 or 8 with a Denovo CD and crossover frequencies at 500Hz and 2500Hz approximately.
That would be almost perfect as it would be ideal for a center channel as well. However I would have to design my own crossover for it and without measurement tools I'd rather stick to a ready made trusted design.
An other option would be a lower priced clone of the Daniel Hertz M1.
Perhaps in the future...