For fun, I compared the Omega18 against the Selenium 18SW1P
18" subwoofer. Both PiAlign and BoxPlot give a ~3.3 cu. ft. box
for the Omega, which seems pretty small for an 18"er. The
Selenium has similar specs except for Qms. The difference is
between 5.53 for the Omega and 10.93 for the Selenuim. Vas is
12.5 vs. 13.3. The freq. plot for the two show the Omega -3dB
around 58Hz, and the Selenium around 36. Does the difference
in the specs make that much difference? Aside from the obvious
answer, why?
BTW, the BoxPlot box for the Selenium is 7.75cu ft. With a similar
sized box for the Omega, you get a sort-of ESB alignment, with a
similar -3dB point. Any thoughts? Anyone tried this Selenium?

Thx, Chris

While not being familiar with the Selenium 18SW1P, its specs indicate that it is tuned to be used lower. It will generate more output in the bottom octave at the expense of performance higher up. These kinds of optimizations are functions of the specifications of the woofer, which were designed to meet a specific goal.

The Omega 18 is more like the JBL 2241, while the Selenium 18SW1P might be more like the JBL 2245. Which is better for you really depends on what you plan to use them for.

I guess my question is about how to select a driver by reading its
specs. In this case, both have an Fs of 29Hz. The only remarkable
differences are the one point is Vas, and the significant difference
in Qms. Is it reasonable to think you can predict a speakers freq.
performance based on reading specs alone, or does this capability
come from running the numbers on a variety of drivers to get a
feel for how each of the specs effect the result? In other words,
plain old experience. I there a table that describes how each
of the specs inter-relate? Something like, "Vas and box size are
proportional. Qms is proportional to low end performance, but the
optimum value is around blah with a Vas around blah."

Thx, Chris

Another thing to consider is that the response curve can be modeled pretty well, but there are important properties that don't show up in this sort of model. Cone flex introduces behaviors that aren't considered in T/S models, but they are usually not an issue below a few hundred Hertz. Distortion performance is an important property that isn't described in the T/S electro-mechanical model either. It's largely the result of electro-magnetic properties, so you would need to model the motor system to determine LF distortion. My point is that there are some properties that determine quality to a great degree, but that aren't described in the electro-mechanical terms usually used to calculate cabinet dimensions. T/S models are pretty accurate at predicting bass response though.

Thanks for the comments...

>to guide you in this regard. The best thing to do is model a system
>based on speaker parameters to see what you can expect. So I'd always
>recommend that you model the system when considering a part or
>comparing it with another. These days, modeling is not very difficult
>at all.

Maybe that's my problem. I'm accustomed to having all the data available and being able to run command line tools in batch mode. If I could have that database of data, I could write the tools, then grep for the result I'm looking for. Now that's what I call a speaker selector! This whole enter the data, interactive GUI thing just isn't my bag. Way too slow.

>the motor system to determine LF distortion. My point is that there
>are some properties that determine quality to a great degree, but
>that aren't described in the electro-mechanical terms usually used to
>calculate cabinet dimensions.

OK. Its becoming more clear now, although depressingly so. It seems the best defense against lower quality motors is cash. Oh well...

Thx, Chris

just look at the games of today-all graphics,no story

DOS u say? command line :o whats that ! hahha
cd/games

my first DOS command when i was about 6,on an orange screen ,california games,xenon2,sopwith,etc etc.and the never ending game zeliard we couldnt finish,i wonder if i could get all of those agian,ive found xenon2 and sopwith2 hah

yep theres no replacement for displacement (and quality woofers)
:-D

id model in winisd pro,its fast.then to be sure,use a spreadsheet like Adrian macks,he has everything winisd does,and ofcourse you can Know whats going on because the equations are right there..

cheers
Mike

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