Anybody with clamshell experience?

[Neo_frog]

I'm currently in the design phase of a ported clamshell with 12 10s in the Cruiser on 12kW. It's going to be a single stage baffle design with two rows of subs with a 19 degree incline/decline from the fascias (Similar to Frankie Rio's Fi Q setup). My question is about the subs unloading with doors open. I'm going to choke the port down and only have the 19 degree angle on the baffles to help with cone control, but I have no idea how the cones will react with no exterior loading.

Do you have any experience with this or is it something I shouldn't worry about? I asked this a long time ago, but I want to see if there's any fresh minds on the matter. I want to tune to (peak based on my cabin) 36hZ, but I don't want to rip up my subs during demos or Bass Boxing.

And if anybody has info on baffle angles' effect on tuning response that would be helpful too.

[Boon]

Treat the cabin as an added benefit, don't rely on it if it won't always be there. Clamshells work as a pseudo horn (Basically 2 tapped horns facing each other), the combination of waves in the 'mouth' of them provides additional loading. The port and internal airspace should provide sufficient loading anyway, if you're unloading with the doors open it's because you have way too much airspace or way too much port and you're relying on the cabin air.

Good luck tuning it... are you planning to tune it like a vented box or like a phase line (t-line or horn based purely on wavelength?)

Disclaimer, I haven't actually got around the building my clamshell yet

Edited April 12, 2010 by Boon

[Neo_frog]

Treat the cabin as an added benefit, don't rely on it if it won't always be there. Clamshells work as a pseudo horn (Basically 2 tapped horns facing each other), the combination of waves in the 'mouth' of them provides additional loading. The port and internal airspace should provide sufficient loading anyway, if you're unloading with the doors open it's because you have way too much airspace or way too much port and you're relying on the cabin air.

Good luck tuning it... are you planning to tune it like a vented box or like a phase line (t-line or horn based purely on wavelength?)

Disclaimer, I haven't actually got around the building my clamshell yet

Thanks for the info. I'm definitely building it for control without sacrificing response.

And that's the thing, I know the port tuning can't be calculated like a normal box. I'm using it more as a reference since the tight angles of the baffle will supply me with dropped tuning. My plan was to build a choked port tuned low, then run sweeps, shave off 1/2" then run again and keep testing to see how the different "port tuning" affects my peak.

I really wish I had more time to test different angles at set port lengths to derive some make-shift equations..

[Colin - STAPUFT]

I saw the topic title and I thought.... "Boon knows this stuff..." and I open it up and look what I see.

I built mine (got lots of design help here from Boon and other folks on SMD) and tuned it as if it were a ported box- just to get it in the ballpark. The best I could get mine to tune to (in the ported models) was something like 42 or 38 hz. Way too high for my liking. Boon and some other people as well told me that it would actually tune and go lower than that. If I had to guess, it is prob. tuned to low 30s somewhere.

My subs are getting right at their RMS each in a 1.75 cu ft box with a bigger than recommended port and I have NO issues with unloading. I really like the way it sounds too. I have had these subs in sealed boxes, "normal" ported boxes, really huge ported boxes and now this- and this enclosure sounds the best.

DO IT!!!!

Edited April 12, 2010 by Colin - 1HVYHTR