Can somebody explain the pros/cons of adding cone mass?

[GuyPanico]

I'm looking too extend the lowend on my sub. It hasn't been built yet, as I keep learning new stuff every week (if not on a daily basis) from you guys. This keeps me changing (improving) my cabinet specs. What i'd like to know now, are the effects of adding mass to the cone. From WinISD, it appears to lower Fs and SPL, and raises the Qtc so you need a larger volume. Sometimes much more volume to keep the same Qtc. Also it seems to degrade transience at very low frequencies a little. I was considering adding 40-50grams to my cone, and about 1cuft. to my cabinet to maintain the same Qtc. Adding 40 grams gives me +3.79db @ 30hz, and 4.63db @ 20hz. Thanks as always guys.

Fs 25.5hz
Qms 4.57
Qes .28
Qts .26
Vas 4.7cuft
Re 4.16ohm

[SY]

Adding mass increases Q, decreases sensitivity (and thus max SPL), but lowers resonance.

[BassAwdyO]

adding mass isnt a great idea if you ask me.

You lose sensitivity only to lower Fs and increase Qts which means nothing really in terms of max output, but changes frequency response.

If you want your sub to go low, you need excursion plain and simple. Lowering the Fs trades higher frequency efficiency for a tiny bit of low frequency extension, but if your driver bottoms out at 30hz with no mass on the cone it will be just as loud when it bottoms out with mass on the cone!

[Stocker]

If you don't plan on ever driving the woofer hard enough to bottom it out, bottoming out is not so much of a problem. If you wanted the sounds coming out of it to be lower frequencies than currently possible, the high Fs *is* so much of a problem.

If you don't mind the efficiency hit, and you can design around the Q changing, and you don't plan to overpower the thing anyhow, I say go for it.

Just don't use a magnetic chunk of stuff right near the center of the cone on a very small woofer... excursion reduction through magnetic tug-o-war! (free woofers lead to experimentation)

[GuyPanico]

I really dont plan on shaking the walls. I'm in an apartment with whiney nieghbors. I was doing research and found that nickels (according to usmint.gov) are exactly 5grams each. If I do decide to try it out, i'll use nickels but i'm not sure what adhesive to use. Maybe good old polyurethane glue. My driver has a 13mm xmax, not monsterous, but a healthy amount of travel.

[SY]

BassAwdyO, in regions where the SPL is thermally limited, adding mass will reduce the max SPL. You're right that it doesn't change things in the excursion-limited region; the mass doesn't change Xmax, but it does change the efficiency.

[Cyrus_s]

Originally posted by GuyPanico
I'm looking too extend the lowend on my sub. It hasn't been built yet, as I keep learning new stuff every week (if not on a daily basis) from you guys. This keeps me changing (improving) my cabinet specs. What i'd like to know now, are the effects of adding mass to the cone. From WinISD, it appears to lower Fs and SPL, and raises the Qtc so you need a larger volume. Sometimes much more volume to keep the same Qtc. Also it seems to degrade transience at very low frequencies a little. I was considering adding 40-50grams to my cone, and about 1cuft. to my cabinet to maintain the same Qtc. Adding 40 grams gives me +3.79db @ 30hz, and 4.63db @ 20hz. Thanks as always guys.

Fs 25.5hz
Qms 4.57
Qes .28
Qts .26
Vas 4.7cuft
Re 4.16ohm

IMO The extra volume of the enclosure as well as the extra 4.63db isn't worth it.

3db is about an extra increment on your volume knob. Headroom is a beautiful thing.

[Ron E]

Originally posted by GuyPanico
What i'd like to know now, are the effects of adding mass to the cone. From WinISD, it appears to lower Fs and SPL, and raises the Qtc so you need a larger volume.

Interesting that some of the others just retell you what you have already stated. You seem to have a fair handle on it, thanks to some freeware. My suggestion is to experiment - build the box halfway between the two extremes and try it with and without the added mass.... You can attach nickels temporarily and for low volumes with double stick tape - if you start rocking out, don't be surprised if the nickels go flying For permanent attachment : www.thistothat.com

I wouldn't add mass to a speaker I was going to mount so it fired up or down...

[BassAwdyO]

SY, thanks for clearing that up.... I didnt mention the thermal limited power region because the goal of adding mass seems to be increasing efficiency at very low frequencys. At low frequencys the speakers are often excursion limited. But also there at the low frequencys volume displacement is the most important thing. Adding mass wont get you very far.

So why would you want to add mass again?

[Stocker]

Originally posted by GuyPanico
I'm looking too extend the lowend on my sub.

Guys, don't overlook the purpose of the excercise here.