Finally Finished the DB10, with a clamshell setup.
I was able to lower the resonance to 38Hz! Didn't expect this, but I'm very pleased of course.
Drivers are Monacor SP-250P.
This means 4 Ohm and 200Wrms at the terminal of the box.
The gap is now exactly 1".
I don't think there will be a lot of turbulence because of the relatively low power.
The braces don't take up too much space, because this box is built too long, so I had spare room for this.
They take about 3.1l of space. (about 13/16 gallon)
I was considering building a WO with these drivers, but then I realized I had to finished something once in a while.



Bart.

Thanks 60,

I can't measure frequencies at the moment, no equipment.  :-[
The resonance is at 38Hz, so I guess it would go a little lower, but, correct me if I'm wrong, a 4th order bandpass rolls off quickly, once it's under the resonance?  :-/

Bart

PS. any advice on how to determine the -f3 point?

Bart_West-VL. wrote on 12/09/07 at 18:22:53:


sure you can, play some of these and if you cant hear it its not there.

top of page look for 'downloads'


http://www.realmofexcursion.com/

Got a nice multi-meter today, only 50€.
Did some dB testing:
The highest peak was at 42Hz.
At resonance (38Hz) there was an average pressure.
Going down from there, it bumped up again at 23Hz
At 51Hz the pressure dipped, higher up it got louder again.

I thought you might be interested in these numbers.

Bart.

Oops, sorry I didn't respond yet. Thanks for sharing that!

In the mean while I was lucky enough to use a Wicked One for a few days and I was having trouble disconnecting it to go back to the Death Box 10" again, he he!
It bothered me that the DB10" sounded a bit boomy¿ or one-note-like¿ and I was disappointed because I read all those good things that can be with this design.

Till now I had the box standing upright with the opening near the floor.
I thought about 'sag' and maybe that this could have something to do with it, after all, even a isobaric configuration also has sag, no matter how stiff the drivers are.

Now its laying on its side so that the drivers are vertical, with the opening pointing sideways.
It made a big difference being a bit drier and better SQ, a lot less boom boom.

Now I'm considering to make the rear chamber even smaller again, I think it's still a bit large for these drivers, because it has to be half the size when clam shelling drivers.
For now it will have to wait, but when I changed this, I'll let you know about the results.

Thought you might find this useful,
Bart

Freeware
SineGen description
Precise software sine signal generator/source. Exhaustive parameter control: unlimited editing, accurate sliders, frequency and phase tweaking, double/half frequency. Real-time. Musical notes. Parameter presets. Timer. Well-done UI. Open source code.
http://e-cat.nm.ru/sinegen/

GET IIIIIT‼


Bart