DIY Speaker Cabs for Tannoy DCs - Advice Wanted

[Graham C]

Hi Graham, Thanks for this. Just by coincidence I did a google trawl and downloaded this program a few hours ago and been messing with it. Is the aim to adjust the volume and port tuning to get an absolutely flat response that tails off or is the aim to get the response as wide as you can between the 0 and -3db lines?

I can go bigger (by quite a bit - probably up to 150 litres). If for example I plug in 150 litres and a the port tuned to 25Hz, the reponse extends a bit lower (though admittedly not by a whole lot) but starts to drop off far earlier, albeit very gradually so that it doesn't dip below -3db until it gets down to 25Hz (see attached graph nb. the pink line is the recommended 87 litre box and the green a 150 litre).. Sounds like not a lot gained for a lot more box, but I've got no experience interpreting what these things mean in practice.

Any idea roughly how much extra volume would be needed to account for X over and cable resistance?

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

 

[MarkS]

Any chance of providing these figures for SRM10B ?

Thanks in anticipation.

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

 

[MarkS]

oy dont knock tannoys,i reqularey use tannoy cougar monitor wedges,ive had the chance to replace them and wont cause they sound so good.its not olny me but all the incoming shows were we do noise love the sound of them also

Try Electro Voice and you will change your mind.

Mark

 

[themadhippy]

Try Electro Voice and you will change your mind

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

 

[Uncle Ants]

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

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).

 

[MarkS]

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

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

Enjoy.

Mark