My first attempt at DIY speakers

Hello,

I have taken the plunge and decided to make my own speakers, I have been looking into DIY for some time now and it must be a very addictive thing to get into:p I'm very interested in the whole shooting match, I'm good with wood, veneering, French polishing etc.

Can any of you seasoned builders give me any pointers, regarding the crossover and box volume I've ended up with, here are the chosen components that I posses,

Crossover was designed by a "professional" on NETCALC but while the SPL plot looks ok, the phase plot looks alarming and I would like to avoid cancellation if possible

Morel MDT 32-s Tweeters
Morel MDM 55 Dome midrange
Morel MW 266 Woofer

Crossover is
woofer: second order L1 2.00 mH, C168.uF
Midrange: Second order L2 0.40 mH, C2 10.00uF, R1 4.70R
Tweeter: Second order C3 1.50uF, L3 0.18 mH, R2 6.80R, R3 8.20R. judging by the phase response graph C.O points are I think 1k and 5k

Internal box volume (sealed box) is 60 litres,

18mm MDF cabinet laminated with 15mm solid beechwood so 33mm total, heavily braced, dynamat extreme on the internal panels to reduce resonance and fibreglass fill, and I will be keeping the speaker baffle as narrow as possable.

Can anyone see any obvious mistakes or things that could be improved?

Happy building folks,

Stewart
 

cyscott

Member
2002-03-24 5:49 pm
might want to rethink

You might want to rethink your design. You have picked out some great drivers. The 55 is a very first order capable mid dome. If you used a first order tweeking the crossover is much simpler. Also with a narrow baffle you might want to look at step compensation.

Scott
 
I'm now looking/researching for a first order crossover, I think I read somwhere that a frist order can be in certan circumstances sonicly better if the drivers are up to it?,

as for the step compensation, could I resolve this by reducing the tweeter and mid level by 6db? also would I need to compensate in any way for bass suckout? my speakers will be around 4m apart and room is quite large. Theirs nothing worse to me than a set of speakers with compromised/lacking midbass/fullness.

Can anyone point me to a link to a description on the different types of crossover i.e butterworth, bessel, linkwitz riley (pardon my spelling) etc pros & cons

I guess I need to do allot more research before going any further, but thats part of the fun ;-)

Stewart.
 

cyscott

Member
2002-03-24 5:49 pm
My opinion is the fewer components in the crossover the better. However you must use enough to make it work. In other words their is such a thing as under doing it. A first order will do the best job of preserving the phase relationship of the drivers and use the least number of parts. Second order and other crossovers do have a place but with a 3 way design like you're planning first order is the way to go. The mid you're using has a very wide usable range. More than enough to get the tweeter out of the basement. You will want to crossover the tweeter at somewhere around 5000hz maybe more.

As for step compensation you can pad the mid and tweeter to do this if efficency is not a poblem. 3 db is really all you need not 6 unless your speakers are going to be used outdoors which I doubt. The drivers have more than enough power handling to make up for it. You will need to be very careful about where your low pass is placed in order for this to work right. You will need to find the step freq. and put your low pass 1/2 octive below it. this could put it very low depending on baffle width. The 55 is good down to about 700hz with a first order crossover so watch out for this.

As for a site on crossovers look at http://www.speakermania.com/

good luck,

Scott