Box Help! Box too large?

[SVB847]

I was wondering if I can get the advice of some more experienced box builders on my current setup. I am running 4 - 18" Sundown Zv2 subs, each powered by a RF T15001bdcp amp. The box/wall is 39H x 49W x 28.5D.. Port is 30H x 10W x 17.5D.. With the baffle/woofer/bracing removed I am coming out to about 21.3 cubes and tuned to about 34hz according to the box calculator. The subs/box sound good, but at times the subs just sound as if they are working too hard on the low notes (sorry I dont know any other way to describe it, almost sounds like they are free air). I have set the gains w/ an O-scope, so I am fairly sure I am not clipping. I was wondering if perhaps my box/port are just too big and maybe I should make both a little smaller. Any input would be greatly appreciated. You can also see my build log in my sig to see the setup if that helps at all.

[big dee]

Probly unloading

[SVB847]

So do you suggest taking the box down to about 19 cubes and maybe slightly less port to maintain my tuning?

[Autruche]

when you say low notes, at around what frequency does it seem to do this?

[SVB847]

I would say around 32hz

[zx10intn]

with the way the box is put together, i wouldnt imagine they are unloading but its always possible. to me it sounds like the box may be a bit on the big side for the power they are getting, or could simply be(though not likely by looking at the build log), that the box is not as air tight as should be.

[SVB847]

Thanks for the input. I would say for the first week that may have been MOST of it, but we took literally 2 weeks of sealing/bracing/foaming/rodding everything to get it as tight as can be. It looks like I can take the box down to about 19 cubes and just shrink the port by 1/2 inch on each side to keep my tuning the same.

[zx10intn]

Thanks for the input. I would say for the first week that may have been MOST of it, but we took literally 2 weeks of sealing/bracing/foaming/rodding everything to get it as tight as can be. It looks like I can take the box down to about 19 cubes and just shrink the port by 1/2 inch on each side to keep my tuning the same.

cool. just test it out and see what you get... make the changes reversable so if it doesnt work out you can take them out and tweak it until you get it where you want it.

[SVB847]

For sure! Thanks! Maybe at the end of the day they just are getting enough power..

[Tarball]

I was wondering if I can get the advice of some more experienced box builders on my current setup. I am running 4 - 18" Sundown Zv2 subs, each powered by a RF T15001bdcp amp. The box/wall is 39H x 49W x 28.5D.. Port is 30H x 10W x 17.5D.. With the baffle/woofer/bracing removed I am coming out to about 21.3 cubes and tuned to about 34hz according to the box calculator. The subs/box sound good, but at times the subs just sound as if they are working too hard on the low notes (sorry I dont know any other way to describe it, almost sounds like they are free air). I have set the gains w/ an O-scope, so I am fairly sure I am not clipping. I was wondering if perhaps my box/port are just too big and maybe I should make both a little smaller. Any input would be greatly appreciated. You can also see my build log in my sig to see the setup if that helps at all.

What do you have your Subsonic (infrasonic) filter set to ?