How much "tweaking" is possible?

[justin.kerr]

I noticed that the Fi Audio subs can be "tweaked" for specific application. What parameters are adjusted for a sealed application? I would love to model some drivers with modified parameters, to see how well these subs would perform in a fairly small, sealed box, and say, 32 of them.

[Fi Audio]

Let me know what you are looking to do... enclosure size, qtc, driver size, power per sub... all the details and Ill see what driver would be best suited and modified for that application. We have LOTS of parts to swap between as well as tons of machining options to really dial things in.

Thanks,
Scott

[justin.kerr]

I would love to keep the enclosure size 5 cubes and under, but 6 would be the max.
I would like to use 18" drivers.
I would like to drive each driver with around 800-1,000 watts, and not hit Xmech at full power until 5hz.
I would like to see the Qtc bellow, .6.

Can you come close to making that happen?

[Fi Audio]

Goes to the 5Hz to - 80 Hz flat response, 102 dB 1W/1m for an 18" sub in a shoebox enclosure

While we still need to follow the laws of physics, but let me see what I can come up with for something like that.
Ill get back to you soon.

Thanks,
Scott

[justin.kerr]

Fi Audio wrote:

Goes to the 5Hz to - 80 Hz flat response, 102 dB 1W/1m for an 18" sub in a shoebox enclosure

While we still need to follow the laws of physics, but let me see what I can come up with for something like that.
Ill get back to you soon.

Thanks,
Scott

If you could make them like that, I would only need 16 of them.

I am very interested to see what you come up with.

[Owen Bartley]

32 of them!? I'm interested to see what Scott comes up with too... but I'm more interested to see what you've got in mind Justin! Come on, give us a hint, you can't go around dropping numbers like that and then clamming up on us!

[justin.kerr]

Yes the 32 sub drivers will be a bit of a challenge to set up. I am still getting help on driver placement and layout.

[mrstampe]

Will that be a commercial application? If not, you better get some earthquake insurance for the house!!

[justin.kerr]

It will be for the new home theater.

[Mike P.]

32 sub drivers? I hope you have a camera! Everyone is going to want to see this!

[justin.kerr]

The last sub build came together very fast, http://www.hometheatershack.com/foru...-my-build.html

This build will take a lot longer to put together.
I am taking the information I gained from it, and hopefully, this will be my final sub build, for my home theater.

[Mike P.]

This build will take a lot longer to put together.....

No problem. We'll wait!

[Owen Bartley]

We'll definitely wait if you'll have lots of pics coming like in your last thread. I can't see how that setup could possibly be lacking output for you... but hey, whatever makes you happy!!

Seriously... 32? Man, this is going to be nuts, I can't wait.

[Fi Audio]

Hmmm... played around for a little bit and Im wondering how flat things needed without any sort of correction. It is easy enough to mass thngs down and increase motor strength while working with the 5cuft and .6 qtc, but you are talking about rather large motors and high Mms to do so. Definitely doable, but Im not sure if an 88.7 dB 18 is your thing... or you would rather have a 93dB 18 and have to boost 5 dB down low.
At 32 drivers, I would think that adding some equalization would be the best/least expensive route to go. And just deal with being 10dB at 20Hz vs 5.

Good old Hoffman and his Iron Law hard at work on this one. Xmax in the 25-30 mm range would be OK Im figuring. With 1000W at 20 Hz youd be looking at 55 or so mm of p-p excursion. In 5 cuft youd still be at about 65mm of excursion at 5 Hz... still within Xmech by a solid margin (albeit 30dB down off of reference).
Any reason why you dont go with half as many drivers and same space, but ported? You can get a fair amount more on the bottom end at that point.

Thanks,
Scott

[justin.kerr]

Thanks for the reply Scott!.

Maybe I need to use a different modeling program?, or maybe I am doing something wrong?
With WinIsd, using 16 drivers ported, in cabinets with 14 cubes, net, so actually the outside dimensions would be significantly larger than (32), 7 cubic ft. sealed, due to the port(s) and additional bracing needed. Tuned to 15hz.
Compared to 32 drivers in 7 cubes, it seems that the sealed beat the ported, by a large margin, down to around 30hz, and have virtually the same output down to 20hz, the ported has a noticeable advantage from 18hz to 12hz, but bellow that the sealed massacres it, up to 22db more output, down to 5hz.

I like the way the Q18's model sealed, they just need a very large enclosure to make it happen, and with 32 drivers, space becomes an issue.

A couple more questions, the Q18's use a foam surround correct? Do you have any idea of the typical life expectancy of the surround? I want this to be my final theater sub design, so longevity is also a concern.
What warranty comes with the drivers? Length? If there was a faulty driver, who pays the shipping for the new driver, and the return of the old driver?

Thanks again!

[Owen Bartley]

I haven't run any calculations for you Justin, and have never dealt with Fi Audio before either, but I just wanted to point out that it seems Scott is genuinely concerned with customer satisfaction here, as he made a recommendation for you to cut your order in half. Kudos to honest businessmen!

I hope you guys can work something out, this is going to be epic if it happens.

[justin.kerr]

Yes, I am all ears, open to all suggestions! If i can raise the efficiency and use less drivers, I am all for it!