Considering building some speaker cabinets

[Gaz]

I have 3 sheets of 18mm Russian birch ply, 39x84cm plus 5 offcuts 25x39cm left over from a project.
I also have a pair of unused Kef Cresta 10s with slightly tatty cabinets.
Now I'm thinking to myself that I could build some cabinets to stick the Kef speakers and crossovers into, and I'm thinking of making them bigger than the originals just to use the wood up.
I know absolutely nothing about speaker design other than I need a box with two holes in the front for the speakers and one in the back for the cable connection thingy. I also fancy making them either sealed enclosure or front ported so they can go against a back wall if needed.
What could possibly go wrong?

[walpurgis]

What could possibly go wrong?

Where would you like me to start? :)

[Macca]

Making them bigger with a sealed cab will give more bass extension down to lower frequency, but at a lower level. But it should work.

Making them bigger and keeping the port is more complicated. Probably best to avoid attempting that.

[struth]

yeah, lots alas; thats not to say it wont work either but it will be in the lap of the Gods unless you have info of someone changing the size/porting of the originals.
Probably best sticking to the approximate size and port of the old one if you want to be sure.

[Macca]

yeah, lots alas; thats not to say it wont work either but it will be in the lap of the Gods unless you have info of someone changing the size/porting of the originals.
Probably best sticking to the approximate size and port of the old one if you want to be sure.

Keeping the same crossovers doesn't give much room for maneuverer, was my thinking.

[walpurgis]

This is the crossover. For a two way speaker it is reasonably complex.

http://i67.tinypic.com/5pmkp.png

[fatmarley]

I'd build them with the same baffle dimensions and internal volume. Drivers need to be in the same position on the baffle and port needs to be the same (although it's fine to experiment with the port length). You can change the port position if you want. Keep any stuffing well away from port and bass driver. Have fun!

[Gaz]

I can always add a port after I suppose?

[fatmarley]

I can always add a port after I suppose?

Unless the existing port is tuned to a very low frequency, you'll get no bass with a sealed box. Wont do any harm to try though.

[Macca]

You could keep the same internal dimensions and the port but make the new cab walls really thick with all the wood you've got. That would be interesting to see how it worked out.

[ianlenco]

I suppose it depends on what you are trying to achieve. I agree with the other folks who suggest you don't mess with the cabinet dimensions. You say the cabinets are slightly tatty so is this what you are trying to improve? Maybe you just want some fun! Looking at the images of the Cresta 10 the cutouts for the drivers overlap and I dare say Kef did this on purpose to keep the drivers as close together as possible. If you really want to make new cabinets rather than trying to tidy up what you have then maybe you should consider extracting the front baffle to make things a little easier for your build.

Good luck.

[Gaz]

I am only doing it for a bit of to see what happens really.

I'm having all kinds of crazy ideas like mini transmission lines but just guessing at dimensions.

What's the worst than happen?
Apart from wasting a few hours and £20 worth of wood

[Gaz]

Although my other plan is a new plinth for my turntable

[walpurgis]

I am only doing it for a bit of to see what happens really.

I'm having all kinds of crazy ideas like mini transmission lines but just guessing at dimensions.

What's the worst than happen?
Apart from wasting a few hours and £20 worth of wood

Go for it and have a bit of fun. Never mind the rightness or wrongness of what you may do. Actually, if the bass drivers have sufficient magnet damping to control a bass reflex box, then they will likely also be OK in the small transmission line cabinet you were thinking of. The existing crossover will probably work in that too. Go for a quarter wave line about 5.5 feet long and it may just work fine.

[fatmarley]

You could keep the same internal dimensions and the port but make the new cab walls really thick with all the wood you've got. That would be interesting to see how it worked out.


Yes that would be fine. Just increase the depth of the cabinet to make up for the lost volume.


I'd add lots of bracing (or experiment with constrained layer damping) line the walls with something like wool underlay or 1" thick acoustic foam. I find that it improves the bass but doesn't reduce it (assuming its kept away from the port and woofer)