linkwitz transform equalised sub + closed seas excel speakers

[deiksac]

Hello,
I am currently assembling a subwoofer (using 15" Beyma 15GT-200, equlised using Linkwitz transform). My main speakers are using seas excel w18ex001 and millenium tweeters but are somewhat big and ugly I did some simulations in LSPcad, which showed that W18ex001 will have na f3 of about 107 Hz in a closed enclosure with internal volume of about 4,5 l.
Do you think it is a good idea to cross the sub at the same frekv (107 Hz) at 12dB/oct? Anyone having similar system?

[richie00boy]

I would build your main speakers and measure the exact Fc and Qtc. You can make a complementary 2nd-order filter to give you a 4th-order Linkwitz-Riley overall response, which you then match with a 4th-order Linkwitz-Riley filter on your subwoofer.

That will give you nice power handling and very low distortion. However, if your sub is not situated very close to your main speakers or that sounds way over your head, then you could just use a 2nd-order Butterworth filter on the sub, but that won't be quite as good IMO.

Of course I'm assuming you are active on the sub and main speakers, I wouldn't recommend passive there at all.

[deiksac]

Richie, thanks for that; the sub will be sitting somewhere below my table and the speakers are going to sit on a shelf some 40 cm above the table, so probably no localisation problems should occur (if the final Fc stays somewhere around 110 Hz).

[deiksac]

I am just wondering - what is the benefit of having 4th order on sub and 2nd order electrically + 2nd order mechanically on main speakers to having 2nd order electrically on sub and 2nd order mech onj main speakers?

[richie00boy]

The higher order crossover will lower distortion and protect the main speakers from over-excursion, on the sub it will reduce mid output better so that localisation and image smear is less of a problem.

[deiksac]

As the simulation suggests, over excursion doesn't come into question - the speaker itsel has linear xmax (0-pk) 5 mm whereas the box will allow it only 3,5 mm when driven hard (which wont be the case anyway)
The original idea is to have main speakers full range. What you say about the sub makes sense.