MTM Boombox Crossover Help


2011-08-13 12:00 am
Looking to help my brother-in-law with a science project for class. He mentioned building a boombox and explaining how everything works. I have 4 W5-1611SA woofers and a pair of BC25SC06 tweets which I believe would make a great MTM. Both drivers, I believe, look pretty managable but I dont know where to start with the crossover. I know the W5 is a "fullrange" but I have read where it benefits a tweeter, so my thougbt was to cross somewhat high (5-8khz). They will be powered from an amp delivering about 70wpc. Havent settled on an enclosure yet, but Im leaning towards vented just to get into the F3 70-80hz range. Would anyone be willing to help on the crossover design?


2011-08-13 12:00 am
I see that you are alot of help...

The boombox that I will be making is that style, where there will be stereo speakers powered by a radio in one enclosure with two individual speaker chambers. Yes it will be portable. All of which should not concern anyone with the question at hand. Im aware that some BSC could come into play, but this is not a critical listening speaker. I am just looking for a simple crossover that is more appropriate than the online crossover calculators
I guess that MTM likes low crossover points, more towards 1 kHz than 5 kHz
It's not just a guess, as I see often it mentioned.
Having two near sources, such the M's of a M-T-M, there are some negative effects such as interference which might be destructive or additive.
BSC pertains to the lower register and it might not be a concern when using two woofers
Speakers should stay separate ( L and R channels) so anything that deviates from this it can be whatever :eek:
A)you can connect them in series and put a capacitor across one ( so a series crossover)
B)you can put 1 coil>speaker>another coil>speaker -sort of 0.5...( a more elaborate filter might be required, such caps etc for 2nd order filter ) +tweeter
C) classic 2 way -I got good results with 1st order on woofer ( fullrange) and 3rd order on Tw

...and -oh!- I copy the schemes :p
I don't know, it depends on the behaviour ("response") of the speakers.
I'd say go on with full speakers then you can decide if less is better.
2.5 might be good, I've never tried it. If it's for a high ( 70 W it's a lot ) power you need to distribute it to more and more speakers.
I see that the W5-1611SA is 8 Ω and has a very pronounced convexity of the cone profile.
Aside from this ( I cannot find the consequence of it :p ) you can try to series connect them -so 16 Ω load- and put a cap across one speaker's terminals
try 10-20-30 uF, maybe a 30-40 Ω resistor ( 20 W or more ) across plus and minus to tame impedance peak .
Would anyone be willing to help on the crossover design?


Attached is a basic crossover for a single MTM boombox. However, if I understand correctly, you are talking of two MTM speakers in a single cabinet? Then the baffle will look different and the crossover possibly has to be adjusted. A sketch of the baffle is required to say more. :)


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