Made up a TL design... any comments ?

[Empee]

Dear Sirs,


Spend a day drawing and this is what I've come up with;
anyone care to give comments on it ?

Maybe someone can sim the TL-part ?
(please ?)


This is what it's supposed to be:

Low driver: KEF B139 SP1044
Mid driver: HEMP FR8c, whizzer removed
Tweet: Stage Accompany SA8525 (6" ribbon)

I know about the difference in sensitivity,
but the plan eventually is to bi-amp it all

Mid & top are in a sealed section, 36 ltr.

woofer's first section is 8,5 ltr.
line's CS starts @ 430cm2, terminates @176cm2
line length = 240cm

What's your opinion ?
any sugestions regarding stuffing ?


Hit me with some constructive critisism !
thank you very much !



Empee



KEF B130 SP1044 data:

Fs 25Hz
Qes 0.4
Qms 5.5
Qts 0.3729
Vas 164 ltr
Disp.area 354cm2

[pkitt]

I would love to model what you wrought, Empee, but need more T/S data for the B130 specifically Re, Le and Bl, although I can calculate Bl from the Vas if you don't know Bl.

[Empee]

Oh, sorry,

I see I wrote B130 but it should be B139...

These are the B139 SP1044 data:

Model: B139
Type: SP1044
Nominal imp. 8 ohms
Freq. range 25-500Hz
Sensitivity: 87 dB
Net weigth: 3.72kg
Closed box volume: 30-60ltr.
Reflex box volume: 60-140ltr.
power handling continues 28.7V rms
Power handling programme 100W
Flux density 0.85T
Total flux: 1.1mWb
Voice coil diameter 52mm
Max. continuous temp. 230 C
Max. internittent temp. 300 C
Thermal time constant 13.7s
Input Impedance R(E) 7.2 ohms
L(E) 1.04 mH
L(e) 0.97 mH
R(e) 4.87 ohms
R(ES) 110 ohms
L(CES) 116 mH
C(MES) 349 uF
Effective diaphragm area 349 cm2
Lineair excursion (pk-pk) 7 mm
Damage limited excursion (pk-pk) 12 mm
Effective moving mass M(MS) 54 g
Suspension Mechanical resistance R(MS) 1.43 mech ohms
Suspension compliance C(MS) 7.43x10E-4 m/N
Compliance equiv. vol. V(AS) 127 ltr
Free air resonance freq. f(S) 25 Hz
Force factor Bl 12.5 N/A
Damping factors Mechanical Q(M) 6.0
Electrical Q(E) 0.39
Total Q(T) 0.37


That's all I could find....



Cheers !

Empee

[planet10]

The lazy way to do a B139 TL would be to use the line dimensions of the B139 TL that Scott & i did. 2 different realizations are shown here:

http://t-linespeakers.org/projects/vProjects.html



There are a ton of possible variations.

Your end-loaded line doesn't take advantage of one of the most powerful tools used in a modern TL -- the offset driver.

dave

[pkitt]

The attached graph shows what I modeled for your TL with the B139 specs you listed. It's not an absolutely exact model, but it's close enough to see its shortcomings. I modeled with a stuffing density of 0.5 lbs/cu.ft. with the stuffing distributed throughout the line's whole length. This isn't necessarily the optimum amount of stuffing. As Dave said in his post, the driver's location at the beginning of the line is not good and the big dip in the response at about 120 Hz is the result of the driver's location. Moving the driver so it would be located at about 20% of the line's length from the closed end would be a big improvement. However, there are other problems to overcome, like getting rid of all those ripples in the response. These can be mitigated by increasing stuffing density and/or increasing the taper. Doing the first will just further kill the bass response, which is already weak, IMO. Doing the second will have the same effect because it will make the line's effective length longer, and the line is already too long making the 1/4-wavelength resonant frequency too low (it's about 20 Hz and probably ought to be more like 28-30 Hz). Dave also mentioned some TLs he's designed for this driver which would be more appropriate. I'll play around my self to see what I can come up with.

[planet10]

Originally posted by pkitt
Dave also mentioned some TLs he's designed for this driver which would be more appropriate. I'll play around my self to see what I can come up with.

Scott did the TL design, i instigated it, and did all the drawings.

This TL gets an anechoic F10 of just over 20 Hz, and was designed with a fairly gentle roll-off to better match room gain.

dave

[planet10]

Another thot -- you don't really want to try to use a B139 much above 250 Hz due to its breakup modes. You'll want to bi-amp right from the start with XO this low, and you'll want to set the exact XO point/box width to coincide for baffle step considerations.

dave

[Empee]

Hi Pkitt,


Thanks a lot for simming it !
well, I guess this isn't the optimal design for a B139,
so it's off to the drawingboard again...

No problem but it might take some days 'till I find the time.

In the meantime, let's try a bit of that lazy way;

Hi Planet 10 !
in your (and Scott's) TTL design, what are:

The line length
The starting CSA
The terminal CSA
The driver's location in the pipe ?

I could try to implement these four numbers in my re-drawn design !

BTW, that's how I came up with this design,
only I used the line-characteristics of Dr. Bailey's S.O.T.A.

Naturatly, I didn't get it exact so that's probably why my design
is not so state-of-the-art.....



Thanks a lot guys....

Empee

[Empee]

Originally posted by planet10
Another thot -- you don't really want to try to use a B139 much above 250 Hz due to its breakup modes. You'll want to bi-amp right from the start with XO this low,

Check !!
I allready planned bi-amping this thing,
XO'ing @ somewhere like 80Hz to 100Hz

That's why the cab for the Hempster FR8c is fairly large

Originally posted by planet10
and you'll want to set the exact XO point/box width to coincide for baffle step considerations.

dave

That thing about "baffle step" I still do not understand.
Do you know a good site or older topic / post where I can find out more about it ?

[planet10]

Originally posted by Empee
in your (and Scott's) TTL design, what are:

The line length
The starting CSA
The terminal CSA
The driver's location in the pipe ?

96" line, So = 124 in^2, Sl = 21 in^2, Zd = 32.25" (6:1 taper)

BTW, that's how I came up with this design,
only I used the line-characteristics of Dr. Bailey's S.O.T.A.

We've come a long ways since then...

dave