Help me to make something out of a old sub

[Mr.Mekulic]

Hi,

I've got a old Wharfedale Modus Sub Bass lying around. It’s a passive sub, so to make some use of it I bought a cheap kit amp to run it (http://www.velleman.be/ot/en/product/view/?id=360242), and installed it in the sub to make a diy active sub. You can see my effort here:

,
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Now here is the part I need help with. The sub is now playing, at least trying to play the whole audio band. So I need a low pass filter.
I stumbled across this


on this forum, and it seems exactly the thing I need.
Some questions about the filter. Do I put it before or after the pot in the sub? About wiring the 20k dual lin pot on the pic. I connect one channel of the pot to each of the positions indicated on the pic? And connect the ground of the pot to the ground point? What is the active component? Resistors will be metal-film 1/4w ones, and caps foil ones, is that fine?

Another question now. I’m not to happy with the sub now as it can’t go too low. Can something be done with making a new box, using these components I have? There are two 6 inch drivers in the sub working in push pull. The driver can be seen here:

and this is the only marking on them

Can someone work out what are these drivers? And how to better house them?


P.S. I’m trying to spend as little as possible on this project, as I’m not sure of the results.

[ocool_15]

For Low end extension smaller drivers are inherently limited.
To obtain Lower bass you need a better driver, more power or a larger box(ideally all 3)

Whats your budget and how large of box can you use?

[Mr.Mekulic]

Originally posted by ocool_15
For Low end extension smaller drivers are inherently limited.
To obtain Lower bass you need a better driver, more power or a larger box(ideally all 3)

Whats your budget and how large of box can you use?

I think I'll give up on the reboxing thing.

I would still like to make a low-pass filter thou.

[Kinnja]

Originally posted by Mr.Mekulic
Some questions about the filter. Do I put it before or after the pot in the sub? About wiring the 20k dual lin pot on the pic. I connect one channel of the pot to each of the positions indicated on the pic? And connect the ground of the pot to the ground point? What is the active component?

I think the presence of the op amp is what makes it an active filter, and I think active filters usually go between the source and the power amp.

Here is a link that might be helpful

http://members.hometown.aol.com/_ht_...b/mini-sub.htm

[Mr.Mekulic]

Originally posted by Kinnja


I think the presence of the op amp is what makes it an active filter, and I think active filters usually go between the source and the power amp.

Here is a link that might be helpful

http://members.hometown.aol.com/_ht_...b/mini-sub.htm

Thanks for the link, is NE5532 ok op amp for the filter ?

[davidlzimmer]

I used that very circuit (the one you showed) with an LM3886 amp that I built. It works suprisingly well. Use a resistive voltage divider to bring speaker level to line level and sum the two channels without loss of separation on the mains.

I admit, it's not as good as a good sub amp but, it did the job!

[Kinnja]

Originally posted by Mr.Mekulic
Thanks for the link, is NE5532 ok op amp for the filter ?

I don't know if NE5532's would work or not. If I were to build the circuit, I would use TL072's because that is what he used.