AV15 Subs (design & construction)

[David Gatti]

Nice work Shin. I never knew you were a closet bass nut

I know too much is never enough, but are you sure these aren't overkill ?

I would have thought 1 sub would have been enough. Corner placed, a single one could probably reach 115dB at 20Hz!!

[richie00boy]

Nice work again Ant, hope you get better soon, but give up that dirty habit!

We looked at using the BK module for our sub, but in the end made our own complete plate amp with LT and everything, measuring just 12"x12" www.8ballaudio.com

If you need any help with the LT or measuring the driver etc just give me a shout, I have written a good guide on measuring T/S parameters.

[ShinOBIWAN]

Al

I'm confused

I took voltage reading and the 2 core wire had 5v - isn't that a bit much for a low level signal?

The 3 core looks to be the correct one but I measure 16-17v. How do I figure out which is ground BTW? I did measure around 33v when I was messing around switching between the connections.

Also, the large ceramic resistors that you can see in the pics on the last page get extremely hot. This is safe I presume?

[ShinOBIWAN]

Originally posted by richie00boy
Nice work again Ant, hope you get better soon, but give up that dirty habit!

We looked at using the BK module for our sub, but in the end made our own complete plate amp with LT and everything, measuring just 12"x12" www.8ballaudio.com

If you need any help with the LT or measuring the driver etc just give me a shout, I have written a good guide on measuring T/S parameters.

Hi Rich

The lowball looks nice, good work on that.

This TS guide you've written; is it any easier or more accurate than a moderately well calibrated Speakerworkshop setup? This is what I use at the minute but would be interested to take a look at another way. Please send me the details to:

zeroex_15 at hotmail . com

[ShinOBIWAN]

Originally posted by David Gatti
Nice work Shin. I never knew you were a closet bass nut

I know too much is never enough, but are you sure these aren't overkill ?

I would have thought 1 sub would have been enough. Corner placed, a single one could probably reach 115dB at 20Hz!!

I think everyone is a bass nut at heart.

I don't really listen at 100dB much let alone 115dB, what I'm aiming for is a natural extension to develop the Perceives into a 3.5way almost or rather a limited bandwidth 3-way with subs. The Perceives will happily reach down to 40hz but after this there's very little in the way of bass. This is where the AV15's will take over for stereo listening and offer stereo bass of course. They will be connected via highlevel for this.

For movies I'll just use both on the LFE channel via low level.

The BK amps are quite flexible and offer level controls for each input.

I think the main advantage of 2 subs is stereo bass for music and reduced distortion.

[pinkmouse]

Originally posted by ShinOBIWAN
I took voltage reading and the 2 core wire had 5v - isn't that a bit much for a low level signal?

Depends, if the amp module has a DC blocking cap, they may just have omitted any DC blocking on the crossover. Do you have access to a 'scope?

The 3 core looks to be the correct one but I measure 16-17v. How do I figure out which is ground BTW? I did measure around 33v when I was messing around switching between the connections.

With your meter set to DC, put the black probe on one pin, then the red probe on each of the others in turn. Hopefully you got it right first time, and you should measure -16V and +16V. If not, move the black probe to the next pin and repeat until you do.

Also, the large ceramic resistors that you can see in the pics on the last page get extremely hot. This is safe I presume?

Yup, that's why they're big and ceramic!

[ShinOBIWAN]

Originally posted by pinkmouse
Depends, if the amp module has a DC blocking cap, they may just have omitted any DC blocking on the crossover. Do you have access to a 'scope?

No scope.

With your meter set to DC, put the black probe on one pin, then the red probe on each of the others in turn. Hopefully you got it right first time, and you should measure -16V and +16V. If not, move the black probe to the next pin and repeat until you do.

I'm using BB OPA2134 in the LT, isn't 17v a bit much for for one of these?

Thanks for the ground tip.

Yup, that's why they're big and ceramic!

That's good then, always freaks me out when you smell that heat discharge from new components and boy do those resistor get very hot. I actually think its a bad design because the resistor are flush up to the PCB instead of stand off a couple of mm to allow air to circulate and there's also various caps in physical contact with them and these also got hot.

I would have spaced them out a little more but its all guaranteed and should it fail then BK are said to have very good after sales.

[pinkmouse]

The OPA can run on 18V rails.

http://focus.ti.com/docs/prod/folder...t/opa2134.html

[ShinOBIWAN]

Originally posted by pinkmouse
The OPA can run on 18V rails.

http://focus.ti.com/docs/prod/folder...t/opa2134.html

Al, you are indeed the master of common sense.

Now why didn't I think of checking the manufacturer's website for information on its products?