First Time Building have a few questions.

[golgiapparatus]

I have been wanting to build a pair of speakers for a long time. I currently own a pair of B&W CM7's that I really like.

On Ebay I purchased a pair of used DM 602 LF 7" Wooker Unites ZZ10129.

The problem is I do not have any information on these speakers, does anyone have anyting on them, or how can I get the required information on them to forcast a cross over??


Thanks for the help.
Golgi

[picowallspeaker]

Speakers ( trasducers ) belong both to the electrical and the acoustical world ,and their construction determines a lot of variables that happened to be encoded in the Thiele & Small parameters . Once you put the naked woofer on the desk , you can measure its coil resistance and also its resonance frequency ,but to determine the Q ( quality ,also the 'shape' of the curve in pass-band filters ) it has to be mounted in a closed box ,so the other parameters can be calculated . So in the end you'll get some numbers ,most depending by the others , by being fractions or inverse of some forces ,being mass ,elasticity of inner (spider) and outer (surround) suspension , inner frictions determined by magnet and coil assembly ( also ferrofluid in tweeters ).
So a skilled professional (or amateur ) is able by just seeing the T&S parameters to determine the 'role' of a loudspeaker in a system , and how it fits . Total Q ( Qtc ) of a speaker in a box tells how it will sound at its resonance frequency ( Fc ) , if the acoustic response would be 'humped' or 'deaf' or will have a natural decay ,where :

Qtc (Q in cabinet) equals 1 at Fc there's no attenuation

Qtc > 1 there's a peak in the response

Qtc < 1 there's a fall in the response

So for a natural decrease of response , which is a Butterworth slope of second order (B2 ), if you 'throw' in the calculations a 0.707 of Qt you'll get
a -3 dB response at Fc ,and if you put 0.505 you 'll have 6 dB of attenuation at Fc .
..Ok , I want fast and fulmineous bass ,no big box , perfect transition to the treble section ,how can I determine the components of the crossover and the box shape ?? You can rely on the parameters given by the manufacturer or measure by yourself ,then use one of the softwares to determine 'which curve' you prefer better among the various 'alignements' .
You can get the demo version of ARTA to do the first (measuring ) ,then to do some box calculations ...there are others !!
Or just stick in a stupid coil and see what happens !!

[golgiapparatus]

picowallspeaker, Thank you for the info. This was a big help.

Golgi