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View Full Version : Just built up this new woofer, specs look awful. What to do?



hispls
04-11-2012, 11:26 PM
New 18" I slapped together with some parts I was very excited to try. This is coils in series, specs with coils in parallel are similar enough.



Re 5.49 [Ohms]
Fs 45.09 [Hz]
Zm 21.64 [Ohms]
BL 22.81 [N/A]
Qms 2.897
Qes 0.984
Qts 0.735
Vas 113.900 [liters]
L10k 2.86 [mH]
n0 1.01 [%]
dBSPL 92.15 [1W/1m]
Ms 329.30 [grams]
Cms 0.04 [mm/N]

This is very strange since I was really expecting a Q around .3 Any thoughts?

KyleBechtold
04-11-2012, 11:30 PM
I can't translate specs into performance so I am no help lol.. but if I remember anything about em doesn't adding/subtracting weight to the cone have a little play in Q?

RangerDangerV2
04-11-2012, 11:31 PM
is it an 8??? high fs...

hispls
04-11-2012, 11:41 PM
I can't translate specs into performance so I am no help lol.. but if I remember anything about em doesn't adding/subtracting weight to the cone have a little play in Q?

Mostly lowers Fs. Adding a kilogram of mass to the cone brings fs to mid 20hz, but that's not really a solution



is it an 8??? high fs...

I said 18.

Same motor with different coil, cone, and softer suspension

Re 2.83 [Ohms]
Fs 29.61 [Hz]
Zm 43.69 [Ohms]
BL 27.50 [N/A]
Qms 3.887
Qes 0.269
Qts 0.252
Vas 176.400 [liters]
L10k 2.38 [mH]
n0 1.62 [%]
dBSPL 94.20 [1W/1m]
Ms 386.90 [grams]
Cms 0.07 [mm/N]

These went pretty well, but unforunately I cannot get those spiders any more, the cones don't hang with 6K, and the impedence of those coils doesn't add up to anything my amp likes.

duanebro
04-12-2012, 12:40 AM
I have never built a sub. But would love to do it some day. Do you know what changes the specs? It looks like a very light cone for an fs that high. Any pictures? I don't have an answer to the question but I will be watching to see if someone can figure it out.

hispls
04-12-2012, 11:22 AM
I have never built a sub. But would love to do it some day. Do you know what changes the specs? It looks like a very light cone for an fs that high. Any pictures? I don't have an answer to the question but I will be watching to see if someone can figure it out.

Oddly enough I thought the old cones were lighter. Really I thought I understood what changed specs up until this one. Time to start beating on it and see what happens. My suspicion is the coil since the motor and coil should, in theory, be the dominant factor and generally these motors provide super low Q with any combination of softparts. Moving mass slightly changes Fs (adding 6oz mass to the cone lowered Fs about 5 cycles), but I'm not about to add 800 grams to the cone for the sake of modeling well at lower frequencies.

Pics will come after I see some responses from some of the box gurus. For now we'll keep it a mystery.

duanebro
04-12-2012, 12:20 PM
What are you using to get the specs for the woofer?

galacticmonkey
04-12-2012, 12:49 PM
I'm guessing you just went with a really light cone and a ton of stiff spiders?

hispls
04-12-2012, 03:50 PM
What are you using to get the specs for the woofer?

Dayton WT3


I'm guessing you just went with a really light cone and a ton of stiff spiders?

Cone feels about twice as heavy as the one on the previous 18" I did. Suspension is rather stiff, but it is a pressed style.

Bump. Testing in 6 cube tuned @ 37hz it sounds pretty decent but is way down from the previous 18. Culprit is definitely the coil/motor combo. I pulled specs from a 15" I did same coil and motor and Q is also close to .7 Fs is a bit lower, but that's a heavy cone/dustcap on that and suspension isn't quite as stiff.

galacticmonkey
04-13-2012, 03:29 AM
The come weight doesn't effect it as much as the spiders. Try a recone with like 2 medium spiders. I prefer softer subs. It's just more efficient overall and plays lower easier in daily setups without needing to best the crap out of the sub in order to get some lows.

hispls
04-13-2012, 07:51 AM
The come weight doesn't effect it as much as the spiders. Try a recone with like 2 medium spiders. I prefer softer subs. It's just more efficient overall and plays lower easier in daily setups without needing to best the crap out of the sub in order to get some lows.


6 spoke basket has me limited on spider options. Not many choices for that larger size spider and I don't want to sacrifice the height off the landing going down. I generally build as soft as I can get away with, but I did plan to possibly throw 6KW into one.

Also pulled some specs off a 15 I have built up with the same motor and coil. Very high Q on that as well, clearly a motor/coil combination issue. Though the 15 has a FS around 30hz and models fairly well in bandpass with net of @ 6 cube