Help with WinISD- building a subwoofer

[Xicarius]

I've got this subwoofer, and I'm trying to work out the box. From the Jaycar site, I've got this:

* Sensitivity: SPL - 87.2 db - 1 Watt @ 1 metre
* Power rated 250w RMS
* Voice Coil Resistance (Re): 1.3 Ohms
* Resonant Frequency (Fs): 23.7Hz
* Mechanical Q Factor (Qms): 3.976
* Electrical Q Factor (Qes): 0.382
* Total Q Factor (Qts): 0.348
* Equivalent Volume (Vas): 66.085 litres
* Xmax: 10mm

Which I plugged into WinISD, and it seems to be saying 40.6 litre box, which is quite small, with various port options. I'm still looking at them.

The thing is, on that Jaycar page it says "Specifications are for 1 driven voice coil only", as it has 2x2Ohm coils, which i'm going to be using together to present 1x 4Ohm to my amp (the Jaycar 240w plate amp)


What I'd like some help with is:

1) What will change based on the voice coil config I'm using?

2) Does the above Box info from WinISD look ok?

3) Box filler! Do I have to use it (I think I do), and is it taken into account in WinISD..?

This is my first audio project (soon, hopefully, to be one of many) so I just feel more comfortable checking a few things as I go along

[simon5]

I don't know if they shorted the 2nd voicecoil when they made these measurements...

1) Efficiency will be 3 dB better (louder per watt imput)
Le will double
Re will double
BL will double
Qes/Qms/Qts might change too, I don't know how they measured them, 2nd voicecoil can be open or shorted...
I guess you'll need to ask Jaycar about this, if they could give you the T/S parameters with both voicecoils driven, it would be easier hehe! You could also measure them when you get the driver if you have a multimeter and an amplifier nearby.

2) Yes it looks ok. 40 liters for a 10 inches driver is reasonable. You don't need to use the size WinISD suggest, it's a modeling tool, change the size, check the SPL and see if it's good or bad for you.

3) Box filler for a subwoofer is not absolutely needed. If you go ported, it's hard to use box filler because it mess with the tuning frequency. If you go sealed, then you can use box filler, the driver will see a bigger box, which is good most of the time. Don't use too much because box filler reduces SPL a bit. Box filler is not taken into account in WinISD. You could use UniBox who can take into account box filling.

You also need to take into account the very ugly 6 dB of bass boost at 35 Hz with that amplifier that will mess everything. You can use a parametric equalizer in the filter section in WinISD to simulate the effect of it. I think Q = 2.0, center frequency 35 Hz and 6 dB of gain would simulate it close enough.

Good luck!

[Collo]

Hi Xicarus

I have done a comparison of some of the Jaycar drivers with a view to using them for Home Theatre subs.

You might be interested in my thoughts on your driver...

http://www.users.bigpond.com/bcollis...er-CS-2366.htm

regards
Collo

[rabbitz]

I thought the the words "Jaycar, port, WinISD, sub" would be too much for you to resist Collo.

BTW, saw your latest sub and whoa..... you've got shares in a PVC pipe company. Blast Furnace not enough hey.

Cheers
Rabbitz

[Xicarius]

Thanks for that. my WinISD stuff is on my other computer, so I'll have a look at it tomorrow. Doesn't look like the best sub or amp in the world but it'll be a hell of a lot better then what I've got (Sony "Super Woofer" with a torn cone...its a 6.5" driver in a 4th order bandpass box).

Space is a bit of an issue, but I can proly cope with 68L. Out of interest, does that volume account for the space taken up by the ports or do I not need to?

[Collo]

Hi there Peter! Long time no see.
I couldn't help myself. 6 metres of 10inch PVC pipe - I just had to do something with it!

Xicarus. - the volume of the design doesn't include port volume. You can work it out with the old pi*r squared * length. Alternatively, while your on my site, dig around a bit and you'll find the "boxnotes" software that will do it for you. It also lets you mess around with different box dimensions.

[rabbitz]

You keep this up Collo, you'll have to redo your renovations as everything with crack up with all these subs

How's your eyeballs holding up with these subs? If I don't see you post for a while, I'll know

[Collo]

Turn volume up.... eyeballs go blurry ....can't see new cracks...no problem!

[Ron E]

I find it rather doubtful that they could design a speaker with a Q of 0.18 when both coils are driven - that also has an Xmax of 10mm. IMO, unless the parameters have been verified by someone's actual measurement, there is something wrong with how they have been published. If the Xmax spec is peak to peak, I might believe the Q spec....

At least in the USA and Europe, the typical convention for publishing specs on DVC woofers is with the coils driven in parallel as that gives the best sensitivity spec.

[Death By Bass]

Originally posted by Ron E

At least in the USA and Europe, the typical convention for publishing specs on DVC woofers is with the coils driven in parallel as that gives the best sensitivity spec.

I've found alot of manufacturers seem to give the BL with the coils in series, as this gives a better number... HMM!!

just my 0 cents (I have no money, give me a break)