parameter translation please

[KevinTams]

"A weighted at 50Hz to 80Hz Excursion 6.1mm linear, positive cycle, 5mm negative cycle. X mech, Mechanical Excursion 25mm +-
Recommended Sealed enclosure 35.300 litres. vented 28.303 litres, Port size 75mm X 120mm"

Can someone please translate that into what I use as xmax. I may use 4 of these in a w baffle woofer below my OB mains and use a sub below these.

http://www.shadowworks.co.uk/SW/HTML/products/nova.htm

Unfortunately Shadow Works aren't responding to my emails so I don't know enough about these except they are very cheap and cheap is good.

Kev

[richie00boy]

The easiest way is to use 5mm as it's the lowest one. However, if you were to make it down or upward firing the cone would shift a little bit from normal rest position so you must take this into account.

As you can see Xmech is massively higher than Xmax. Knowing the quality of Shadow Works drivers, I reckon you will be able to squeeze easy more than 5mm out of these drivers without straying too far into non-linearity. 5mm with these drivers will be within a very linear range, probably most other similar price drivers can only manage half as much Xmax with the same linearity.

[KevinTams]

Sounds like you've experience of Shadow Works product and like it.

Unfortunately I've no TS parameters for these drivers but from reading their blurb it looks as though FS is fairly low, possibly 28Hz and these drivers are the Nova but with Kapton voice coils with supposedly higher power handling. they recommend them for either closed box or vented so basically I'd be buying these with not much info.

Do you reckon they're worth a punt at £80 per pair?

Kev

[richie00boy]

Yes, I have experience of a couple of Shadow Works products and rate them very highly. A lack of T/S parameters is what put me off at first, but at the end of the day all their speakers are good and have been tuned/designed by experienced people so you are guaranteed not to get any real duds. I'm sure all have parameters that are within acceptable ranges.

Take a gamble as the price is good. I'm sure you'll be happy with them. And you can measure the parameters yourself if you so wish. I'll be putting a full 'how to' (suitable for beginners) article on my website soon.

[Svante]

Use a peak value of Xmax of 5 mm. It does not matter much, if 6.1 mm was the true value, the difference in maximum output level (MOL) would only be 1.7 dB, if Xmax limits the MOL.