DIY Speaker Cabs for Tannoy DCs - Advice Wanted

Lordy mama - where to start? First off, your graph and analysis are spot on..as you said, you can either have a 'bit more' at the very bottom - and lose a few dB @ 45Hz or have a 'maximally flat' curve to use the jargon. Not a lot gained is also how I would describe it
The trouble with modelling the passive bits is too many unknowns.

If you use their x-over, you would start by measuring the DC resistance of the inductor that feeds the bass driver, then add the resistance of your speaker wire. It might come to say 1 ohm..

Re = 6.3 ohm [datasheet] + 1 ohm = 7.3

7.3/6.3 = 1.159

1.159 x Qes = 0.5005

Qms = 5.32 [datasheet]
[ 1/.5005 ] + [ 1/5.32 ] = 2.186

1/2.186 = 0.45746

This is the new Qts and has gone from 0.4 to now 0.457 which sounds trivial but isn't. If the Q is above about 0.5 you will never achieve a curve like your 150 litre box line because the Q is too high. Try making a new driver model in WinISD with the new Qes and Qts [ call it DC 200 + 1ohm] and see how the new curves need much bigger boxes

 

Hi Dev!

I don't have params for the 2558 driver as I never had a pair to play with...bit thin on the ground. I was going to recone a pair of 2588's but never got round to it - sorry.

Mark

 

Try Electro Voice and you will change your mind.

Mark

 

i have( the sx200's are a pretty good alrounder),along with meyer,jbl,martin yamaha and sevral other manufacters offerings and still stick with the cougars

 

Dear Graham,

Many thanks - maybe we should have a new Forum - "Speaker Design 101"

I plugged the new figures in and it came back with a 135 litre box (quite a difference) and the port tuned to just over 26 Hz. The curve looks a lot better too - we've magically gained 5 Hz at the bottom end (see attachment, pink = 87 Litre box, green equals +1ohm and 135 Litre box).

Now I'll just have to get the real measurements for resistance (actually find someone who can do it for me - I wouldn't have a clue) and plug in the real figures.

As an aside - this small change to the paramaters has made a big difference to the optimal box size and port tuning - given that part of this change is down to the resistance of the speaker cable, could this be why speaker cables might make a difference? (no I don't want to start that old debate again, but it seems logical).

 

Well I guess that makes you a happy man...

Enjoy.

Mark