mixing sub sizes

If you have two sound sources creating the same sound at the same time/amplitude/etc, there is of course a large change of cancellation. Wave cancellation is when waves of equal energy collide in such a way as you effectively dimish their energy. You can have cancellation without the sound waves being completely cancelled. Some freqs will be diminished, some may even be amplified due to wave reinforcement (same freq/amplitude waves close enough together to reinforce each other, opposite of cancellation).

The bottom line is the result will be an uneven frequency response, and one that likely will be all over the place. An EQ could adjust for it somewhat, but not completely.... and I really dont see the advantage of trying to do it.

You are simply trying to reproduce a bandwidth of frequencies accurately. A sub in a sealed enclosure gives a nice smooth flat response along the entire bandwidth usually, where as a ported box peaks output at a certain point, dropping off drastically below but remaining relatively flat above this freq (why low tuned boxes can have excellent SQ, contrary to what some people believe). So, why add another speaker of another size/brand/whatever that's going to complicate things?

What exactly is the purpose of wanting two 12's AND one 10 to play the same frequencies? If its to make it louder, you'll likely be louder with the two 12's alone. Certainly would be louder with three or four 12's instead of two 12's and a 10. So if its to make your stereo louder, that's a bad idea.

If its out of convenience (you already own the 12's and 10), Im sure you own a portable boombox too, why not strap it to the dash and have those speakers making noise too? Because as Im sure you already know, it would most likely hurt the over all sound performance, not help it. The same is true of mixing sub brands/sizes/models, it simply will not help the SQ performance. Just because you own it, and it makes music, doesn't necessarily mean it will help your car stereo's performance. So if its to make your stereo sound better, that's a bad idea also.

The only real way Ive heard of mixing sub sizes effectively was with a fairly compex xover setup so each sub size played its own frequency band. But you also have to consider how well each sub will perform in its particular bandwidth, how well they will blend together, the transfer function of the vehicle and its huge impact on the sound, etc. Things get very complicated, and after all is said and done, I still find myself asking .... why do it anyway?

It would be ok if you had different amps running the different subs and crossovered correctly to get all of the frequencies: the 10 being a little higher than the 12's.

That is MUCH easier said than done. To crossover everything correctly you need to be very familiar with how each driver will react in the specific car to which frequencies.

Beyond that...just to state the obvious, neither 12's nor 10's have a distinct advantage in one frequency range over one another.

neither 12's nor 10's have a distinct advantage in one frequency range over one another.

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Ehh...not entirely true. Given equal power and enclosure alignments, the 12 will get louder and play lower, as a function of its Fs, Mms, system Q, and BL product, not to mention a few other things //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I know...was just saying that the difference between the two is not large enough to defend splitting up the frequency range.

Was pointing to the idea that if you're going to mix sizes, and do it right, you'd get better results separating the spectrum with a 15 or 18, and a 10 (though I would still never do it).

hmmm... How does this sound:I'm thinking it would be nicer SQ/SPL wise to split those up. (yes i do have 2 amps that have the means to split the frequencies). I was thinking from about 20-25hz to 50hz for the 12's, and 50hz to 100hz for the DVC 10? Also, Audioholic, and everyone else, big help, thnx for the info. As for why doing it, because I can say then that I tried, and have the expirence of doing it to back up that it doesn't work. That and i'm on spring break.

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Here's the problem, when you start getting that high you are moving into midbass territory, and localization will start to be a problem. In other words, for best performance, you'd lowpass your subs (in the back) that low anyway (50-65hz), and then the midbass would take over as you want your 10's to, but the midbass drivers should be in front of you to not pull the bass localization towards the rear.... if you are wanting to talk about what would or wouldn't sound good. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Simply put, the bandwidth a subwoofer -should- play is very narrow already, there is really no need to try to split it between two subwoofer systems. You'd be better off dedicating that extra cone area to dedicated midbass drivers, in front of you, to blend with your front stage.

Ehh...not entirely true. Given equal power and enclosure alignments, the 12 will get louder and play lower, as a function of its Fs, Mms, system Q, and BL product, not to mention a few other things //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

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do you care to explain how the size of a woofer affects its parameters? because im not making the correlation...

Because a 15" will simply have more moving mass than a 12", for one //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif It's a function of design, Adire has published some good tech papers on it.

the moving mass alone does not dictate the Q's, the Fs, the Vas or any of that though. a large portionof that is determined by the suspension and motor. sure if you add mass to a woofer without altering the suspension or motor it is going to change those parameters, but just the size of the woofer alone isnt going to affect them.

as a generalization you can say that with most cheaper woofers this is true. but with a properly designed woofer you can have an 10" or 12" that will play just as low as a 15" or 18" woofer.

I'm with Hoss here Jack. Just because a woofer has a higher Mms, it does not mean that it's specs it always lend itself towards better LFE. You have to look at the entire design of the woofer (Bl, Mms, Cms, etc etc). To make an assumption based solely off of Mms is simply wrong. And whose to say that the 12 will even have a higher Mms than the 10? Maybe the 10 used heavier VC former or larger coil? Maybe a different, heavier cone material? Etc etc

So, to say that a 12" will play lower and/or louder of a 10" sub of a different brand/model (as is the case here), you would have to look at each individual sub and not just their diameter.

Anyways, as I said in your other thread jacko.....waste of time and effort. However, if you want to experience it first hand, go for it //content.invisioncic.com/y282845/emoticons/thumbsupwink.gif.129404938effda6ad9cca39e7f4b58a3.gif Again, just be sure you have a nice reference system so you can hear what an accurate reproduction of the music should sound like.