Enclosures for external crossovers

[wiredmonkey]

Hi all,

I've been building a pair of speakers at an EXTREMELY slow rate (over 2 years now!) and have finally finished them!

I opted to use external crossovers because i will no doubt play with different setups.

Today I put together a 2nd order 2 way butterworth filter and it seems to work ok ( a little under the optimum 2700Hz 3db point but okay nonetheless).

I then went to put the crossover into a die cast enclosure with the thought that a grounded enclosure would reduce external hum from other electronics in the area. Well, my crossover point dropped by about 500Hz and the signal became quite noisy from the same source (sig gen - amplitude approx 3V)

It dawned on me driving home from work (built the crossover in my lunch break) that the enclosure itself would cause the field of the inductors to change substantially.

Is this right and if so, any recommendations to sort it all out?

Thanks in advance

(I've attached a pic of my still unheard speakers! - p13wh vifa woofer and d26 vifa tweeters

[Loren42]

Do the lights behind the speaker flash with the music?

I think you are right about the enclosure. It is a Faraday box. Any magnetic fields inside that box tends to get squashed if they are not static.

[Glowbug]

Is this right and if so, any recommendations to sort it all out?

Plastic project box

[mondogenerator]

an aluminium box will lower the inductance of the coils quite a lot, as would a brass box

A steel box would increase the inductance a lot

Either way you could also be having a faraday effect, or at least a compression of field lines, or even a coupling of 2 coils via the box.

best bet would be to use a ABS/plastic box, or make one out of MDF or other wood, if you are concerned about it vibrating(which i assume you are or why else use a sturdy metal one in the first place)

hope this is some help. i myself have been trying to finish my 1st REAL loudspeaker project for 10 years, and they have wires sticking out of ports STILL. I gave up and started another project instead, with a somewhat shorter timescale in mind.......

good luck

[wiredmonkey]

Thanks, I'm kicking myself I didn't consider the magnetic fields on the enclosure! Oh well, live and learn!

Loren, The lights only react when I switch the amp on with my completely over the top filtering capacitors and their slightly intimidating inrush current! :P