2 older fi q15 subwoofers in sealed box

[4Q15D1 0]

hello im building a sealed box for 2 q15 subs in my 1996 honda civic hatchback, i have a few questions?

1.... should i have each sub in seperate chambers or the same chamber? what is the pros and cons of doing either?

2.... what kind of difference in sound should there be between the largest recommended size encloser and somewhere inbetween? and whats the pros and cons of each?

3.... what kind of effect would there be having the subs down facing?

Now for my front stage i want some more midbass, i have 2 different types of 6.5 inch woofers, infinity perfect 6.1 and older set of diamond audio hex series, i was thinking of putting the infinitys in the doors and getting some q-form kick panels for the diamond hex. what are your thoughts on this setup?

i will have these crossed over at 80 herts, i dont have the tweeters anymore for these sets so i ordered some silk dome tweeters from parts express and hook the tweeters up to the crossover from the diamond set, then use the infinity perfect 6.1 woofers with their crossover without a tweeter, these two sets would be hooked up to a single stereo amp, what are your guys thoughts on this setup?

should i have the infinity set powered by a seperate amp and use the built in crossover on the amp?

well thanks for reading...... brian

[Impious 1,476]

hello im building a sealed box for 2 q15 subs in my 1996 honda civic hatchback, i have a few questions?

1.... should i have each sub in seperate chambers or the same chamber? what is the pros and cons of doing either?

Either way is technically fine. Separate chambers has the advantage that the wall separating the two airspaces acts as a brace to the enclosure, and if one of the drivers fails there is less chance of damaging the other driver. There's really no advantage to a common chamber enclosure, other than it's a little easier to build.

2.... what kind of difference in sound should there be between the largest recommended size encloser and somewhere inbetween? and whats the pros and cons of each?

Depends on what enclosure volume differences exactly you are referring to. Generally speaking the larger enclosure has a little better output on the low end with the trade off being less peak output. The larger enclosure will have "better" transient response, but that doesn't mean you'll necessarily like the "sound" of it better. Achieving a Qtc of .5 (larger enclosure) is considered to have the "best" transient response performance, but a Qtc of .707 (slightly smaller enclosure) is thought by many to be a better target as it's an more fair trade-off between acceptable transient response, peak output and low end response. Going beyond a Qtc of .707 (even smaller enclosures) will increase peak output while decreasing low end output & worsening transient response. Without knowing your preferences and attention to detail, there's no way to tell which you may like better or if you can even hear a difference. The larger enclosure will have less mechanical power handling.

How audible any of these differences are really comes down to how much difference in enclosure volume you are referring to, your music & listening preferences, how acutely you can hear differences, etc etc etc.

3.... what kind of effect would there be having the subs down facing?

With a properly designed down-firing enclosure & loading surface it wouldn't make much of a difference. Some subwoofers shouldn't be up/downfired due to the weight of their moving mass compared to the compliance of their suspension. Without running the numbers (which I haven't), I don't know if the Q falls into theis category of subwoofer or not.

Why do you ask?

Now for my front stage i want some more midbass, i have 2 different types of 6.5 inch woofers, infinity perfect 6.1 and older set of diamond audio hex series, i was thinking of putting the infinitys in the doors and getting some q-form kick panels for the diamond hex. what are your thoughts on this setup?

Don't do it. Not a good plan. Too many speakers, not enough control over them. It won't sound good and won't really help you achieve your goals without tremendous downsides and trade-offs.

i will have these crossed over at 80 herts, i dont have the tweeters anymore for these sets so i ordered some silk dome tweeters from parts express and hook the tweeters up to the crossover from the diamond set,

How do you know the tweeters from partsexpress will play nice with the Diamond crossover? What impedance was the Diamond crossover designed to be used with, and what is the impedance of the tweeters you purchased? What is the crossover point & slope of the Diamond passives, and what type of filter does the tweeter you purchased require? Does the Diamond passive use any type of zobel filter or anything else on the tweeter portion of the crossover?

then use the infinity perfect 6.1 woofers with their crossover without a tweeter, these two sets would be hooked up to a single stereo amp, what are your guys thoughts on this setup?

Don't do it. Not a good plan.

Also, certain passive crossover filters will present nearly a dead short to the amplifier if there is no load (speaker) connected to the crossover. So running the crossover without a tweeter may potentially damage your amplifier.

should i have the infinity set powered by a seperate amp and use the built in crossover on the amp?

You should simply not use the Infinities, period. You should also revisit your plan of using different tweeters with the Diamond crossovers. Based on your questions & statements here, I'm doubtful you've done the necessary research to verify those tweeters & that crossover are a good match. Last, not sure on your vehicle, but most Q-forms aren't great. Majority of them are poorly designed overall.

[4Q15D1 0]

thanks Impious for the reply, the down firing of the subs was mainly for protecting the subs, i like the sound of the diamond hex mids better than the perfects so i'll use them with no crossover, i have 2 ppi pc2600.2 amps, i'll use one on the mids and one on the tweeters as an active system, the crossover on the ppi amps is pretty good, the tweeters are 4ohm so it should work with the seperate amp.

the kinds of music i listen too is mostly metal, but i also listen to rock, country, blues, and everything inbetween, but no rap.

i like alot of midbass, plus i was told the Qs should be lowpassed at 80 hz, the diamond hexs have good midbass but really couldnt handle too much power , so if anyone know of some 7 inch or smaller mids that can handle around 150 watts rms and between play between 80 and 2k hz and have some good midbass thanks...

what i would like for my system is to sound like a live concert.

now for the subs should i just build the box like in the middle of the specs? I'll just have the sub box facing foward.

i'll also use two seperate enclosers for the subs....

has anyone used those cone shaped spikes for the bottom of the subwoofer box in a car? i would think that would help to stop some of the vibration and rattles??????

thanks for the reply ........ brian

[Impious 1,476]

What features do those amplifiers have for the crossover section?

As for the enclosure.....IMO build the largest enclosure you can fit, or build it towards the top end of the enclosure range. You can then always test it & see what you like best.....add some cut down 2x4's to the enclosure to methodically reduce the enclosure volume, see if you notice any change in sound & if you find the change to be an improvement or not.

I would not suggest using spikes in an enclosure for an automobile. Ideally you would have the enclosure secured to the vehicle, which would completely negate their effects anyways. But at the very least our resonance problems aren't going to be solved by those little pegs. That is what CLD sound deadening is for.