Axiom Home Page Forums General Discussion Stereo how can a 12" sub outdo a 15" sub?

ok. i realize i might be naive here..but i just don't get how a 12" sub (the hsu vtf3 mk2) can outdo my 15" deftech sub...now..i know from personal experience that in fact it does, but how? shouldn't the 15" move more air? and reach deeper? and be louder cause it's bigger? if there is a simple explaination, i'd love to hear it.

btw. i will be picking up my HSU VTF3 MK2 sub on saturday. :-)

The simple and short answer is:

The Thiele/Small Parameters.

Which include:

Mecanical parameters
Electrical parameters, and
Electomechanical parameters

Put them all together, mix them up, and you get a speaker designed to do what you want it to do in the box design you have in mind.

You can put a big honkin 18" speaker designed for it, in a moderate size sealed box and move lots of air to a moderatly low(say 40 hz)frequency and fil a skating rink. Or you can put a 10" driver designed for it in a ported moderate size box and tune it to 18hz and shake the walls and shatter the crystal in your apartment.

You can put a driver designed to best perform in a sealed cabinet in a 1 cu ft sealed box and get down to 43hz, put the same driver in a 1.5 cu ft box and get 38hz, put it now in a 3 cu ft box and get down to 30hz!

In a ported box things get a whole lot more complicated! Where in a sealed box the size is about all that matters(but don't you EVER let Fb exceed Qts)In a ported box size matters, but so does the port dia or slot size, but so does the length of the port. Then it has to be tuned to impedance peaks, yada yada yada, and so on.

Bottom line; the designer desides on what type of enclosure to us and what size driver to utilize and then takes about eighteen different parameters and mixes and matches to either design and build a new driver that works, or buys an off the shelf driver that fits all the parameters required.

Cool, huh!
Rich.

Wow. Rich really did a nice job on that!

I was just going to say "Excursion, Excursion, Excursion!" but his answer is all sciencey and stuff.

Yuck I just got home, and read what I had written concurrently with getting four Grandchildren off to school this morning, and me out the door as well. Talk about poor spelling and punctuation!

Well....sorta got the point across,.....if not very eloquently

A fun subject though!

man. i hate not knowing what i'm doing...but at least i'm trying to learn. i am SURE this HSU VTF3 MK2 will be better than my def tech 15" subs....just didn't know the how's and why's...

Well,...I've been Googling, and gargling(note; "Gargling" is what you do when you try to digest bad data, and it just won't stay down!) all over the place trying to find out exactly what it is that makes one better than the other, and I'm just about stalled in my attempts to find precisely what the PF15TL+ is all about.

Sometimes I think it may be a driver with passive radiators), but then something else pops in to say that it's not.

Then I get the impression that it goes low enough, but not loud low. Then it seems that maybe it does play low and loud, but only when high distortion is factored in.

I get the impression that it is foremost a musical sub rather than designed for HT,(but then some others contend that it's great for both)

It appears that lots of folks like it, but perhaps a few more don't.

...and it seeeems to be discontinued, making data gathering even more difficult.

Bottom line, of course, is that without lots and lots of information, including the T-S parameters(true sets, not doctored)on BOTH subs, plus detailed build dimensions, on both subs, and(most importantly)verified and comparable plots and graphs, on both subs, we ain't gonna get a good and honest comparison!

We can, and have, had a lot of fun looking for data(kinda like goin' fishin'.....when all is said and done, the fish goes back into the pond!)

It sounds, on the surface, that you may be making the right decision in your next sub purchase,......we just can't currently quantify why!!
Rich.




Oh,... I just gotta add something to the bottom about something John had said in responce to another thread you had started: Remember the "round vs square' question? He was talking about port length.

Just for fun, I had done a couple quick checks to find out what size port I'd need with my new driver IF I decided to run it in a ported alignment.(I wouldn't cuz it's designed to be in an acoustic suspension environment)But the port would have to be slightly over 5" in dia to not give any port chuffing, and be over FOUR FEET LONG!!!

Oh, and by the way, one bad reaction I got from my Wife when I suggested a round enclosure to house an iso-baric alignment, was that it looked like a hot water heater and it belonged in the utility room, NOT in the living room!!! Ah,...WAF again!

This IS a lot of fun though, isn't it?? And that's what it's all about
Rich.

On what grounds are you comparing the two subs. I ask only because to evaluate the two, they should be judged in similar setups.

The same setup would be ideal. Also to make an unbiased evaluation, you will need to place the subs in the same location, level match them, correct any room induced frequency bumps or dips. Then listen to source material on both.

Logically thinking, the 15" should outperform the 12" if all else is the same. But like already mentioned in the thread, how the sub is constructed plays a major role along with quality of the amplifier used to drive it.