Ditton 33 to TL . . .

[royville]

Hi, a while back I decided I wanted to make some TL cabinets for my old ditton 33 speakers.
Heres what I've got so far...

First thing was to measure the T/S parameters for the bass unit which I did with the help of this site.

Measuring Loudspeaker Driver Parameters

I was able to get all the needed parameters except for the B*L parameter, I needed this because to find out what size to build the cabinet I used an alignment table spreadsheet (by Keith Webb) based on MJ Kings alignment tables which i got from here . . .

http://www.quarter-wave.com/TLs/Alig...tor_3_3_09.xls

I eventually fuund the BL parameter by purchasing a licence from MJK to use his worksheets and putting my T/S parrameters into one of them.

Now my question is this . . .

Which is the best way to go about designing a cabinet using the information gained from the alignment table spreadsheet?
Info given is;

Line length: 2.396 meters

closed end area: 0.1473 meters2

open end area: 0.0147 meters2

Is there any software around for example (preferably free!) that would do it?
I also read somewhere that you can reduce the size of the cabinet if you mass load the driver and use a small port. - how does one do this?

I would be greatfull for any ideas or suggestions for this project, and when I start building I will post pictures to show my progress.

Regards to all
Roy.

[pkitt]

Since you've already "bought" the license to use Martin's worksheets, use one of his TL worksheets to model your TL. I don't know what your driver's T/S values are, but based on what you listed from Martin's alignment tables, the 10:1 tapered line you propose has an actual length of ~94", but with a 10:1 taper, its effective length will be ~154" making its 1/4-wavelength resonant frequency be ~22 Hz. Now, if your driver's Fs is not close to 22 Hz with its Qts also close to 0.4, the resonant frequency of your proposed line will not likely be optimum for the driver. If you want, list you driver's T/S values and I'd be happy to do some exploratory modeling of both tapered and mass-loaded TLs for you.
Paul

Originally Posted by royville

Hi, a while back I decided I wanted to make some TL cabinets for my old ditton 33 speakers.
Heres what I've got so far...

First thing was to measure the T/S parameters for the bass unit which I did with the help of this site.

Measuring Loudspeaker Driver Parameters

I was able to get all the needed parameters except for the B*L parameter, I needed this because to find out what size to build the cabinet I used an alignment table spreadsheet (by Keith Webb) based on MJ Kings alignment tables which i got from here . . .

http://www.quarter-wave.com/TLs/Alig...tor_3_3_09.xls

I eventually fuund the BL parameter by purchasing a licence from MJK to use his worksheets and putting my T/S parrameters into one of them.

Now my question is this . . .

Which is the best way to go about designing a cabinet using the information gained from the alignment table spreadsheet?
Info given is;

Line length: 2.396 meters

closed end area: 0.1473 meters2

open end area: 0.0147 meters2

Is there any software around for example (preferably free!) that would do it?
I also read somewhere that you can reduce the size of the cabinet if you mass load the driver and use a small port. - how does one do this?

I would be greatfull for any ideas or suggestions for this project, and when I start building I will post pictures to show my progress.

Regards to all
Roy.

[royville]

Hi Paul,
Thank you very much for the offer, - it would be very welcome. I'm very much a novice when it comes to using MJK's worksheets.
Here are the parameters I measured as described previously . . .

Vs 1540 mV
Is 112 mA
Re 3.7 R
Rs 10 R
Fs 21.5 Hz
Vm 221 mV
Im 22.1 mA
Rm 59.68 R
r0 5.09
Ir 49.84 Ma
Vr 498.42 mV
Fl 15 Hz
Fh 27.5 Hz
Qms 3.88
Qes 0.26
Qts 0.24
Vas 225.62 ltr
BL 8.128

Its an 8" bass driver, so allowing for the rubber surround I a value of 315 cm sq for Sd.

I have an idea of how I want it to look but I don't know how, or what app to use to design it from my data.
Regards
Roy