Any reason JL didn't go with a passive radiator design in the F113? - Page 2 - AVS Forum
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post #31 of 47 Old 07-25-2013, 02:17 PM
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Speaking of DSP, I always wondered why JL kills the output on the Fathom at around 20hz. They have a good amount of amp and a beefy driver and they pretty much cut the legs out from under it.

It would rob the right of the graph but then ad to the left. Guess they fig 20 is good??

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post #32 of 47 Old 07-25-2013, 05:46 PM
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Originally Posted by Tack View Post

Well, I was speaking in general terms but you're right about the small PR. A 1 ft³ PR box will be no output monster, but you can have something that's flat to tune in a small box I guess. Depends on your goals.
Yes you can, above tune. There's nothing to be done below that.

I'm not trying to correct you, I just don't want anybody to get the wrong idea and sack their driver. " Dood I got 124db at 10hz from my PB12!" wink.gif

Speaking of DSP, I always wondered why JL kills the output on the Fathom at around 20hz. They have a good amount of amp and a beefy driver and they pretty much cut the legs out from under it.

Well sure box size is always the trade off vs either SPL or extension, Hoffman's Iron Law at work and all. The benefit to this route over a sealed EQ'd box is there is no compression of the low frequency signal. For example, If I have a 1000 watt amp on my tiny sealed sub, and I'm boosting below 30hz by 6 db, the sub will only be linear for the first 250 watts of output, as in the SPL achieved at 50 hz from a 250 watts is pulling 1000 watts from the amp where that 6 db of boost is applied. After that point you will no longer increase SPL throughout the boosted range of response, while the higher frequencies continue to get louder. Compression is occurring. This will not happen if a PR reflex design is used, and the fact that JL cuts the response below 20hz anyway removes one of the main perks of a sealed design, making it even more questionable (its about the $$).

Just so I dont come across as completely talking out of my a$$

This woofer
http://www.parts-express.com/pe/showdetl.cfm?partnumber=297-460

This PR with 750g mass added
http://www.parts-express.com/pe/showdetl.cfm?partnumber=293-680

In a 14" cube with 800 watts





Not saying this would specifically be better then the JL, just that subs like this are completely possible. You can see the price of the PR, and why they are not used wink.gif
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post #33 of 47 Old 07-25-2013, 07:50 PM
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Originally Posted by Tack View Post

Speaking of DSP, I always wondered why JL kills the output on the Fathom at around 20hz. They have a good amount of amp and a beefy driver and they pretty much cut the legs out from under it.
So that guys using EQ to try and get out of it more than it can give won't destroy them. Manufacturers hate warranty returns.

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post #34 of 47 Old 07-25-2013, 08:02 PM
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Hey Jay1 I never did notice you mention how the two you built sounded or any perception of SQ? Any chance of sharing a little regarding? We see so little info or experience with utilizing PR’s. Some over in DIY but never really any over here.

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post #35 of 47 Old 07-25-2013, 08:19 PM
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Originally Posted by steve nn View Post

Hey Jay1 I never did notice you mention how the two you built sounded or any perception of SQ? Any chance of sharing a little regarding? We see so little info or experience with utilizing PR’s. Some over in DIY but never really any over here.

Well, I originally had my drivers and amps setup as sealed subs, "ideal" enclosure volume Q 0.7. Switching to a 7 ft3 17hz box with the same driver/amp combo, literally the only difference I have noticed sonically is when those low bass scenes (and songs) hit the whole house feels like it's flexing. With the sealed setup all of the notes were there, but the visceral power was very much reduced.
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post #36 of 47 Old 07-26-2013, 05:55 AM
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Originally Posted by Jay1 View Post

Well, I originally had my drivers and amps setup as sealed subs, "ideal" enclosure volume Q 0.7. Switching to a 7 ft3 17hz box with the same driver/amp combo, literally the only difference I have noticed sonically is when those low bass scenes (and songs) hit the whole house feels like it's flexing. With the sealed setup all of the notes were there, but the visceral power was very much reduced.

Yes it would be. I think that’s why my favorite sealed sub I’ve bought came in at +-2dB at 18hz with nice SQ. I never could count on room gain to much due to being in such a leaky room, but overcame it with the BASSIS when running DIY sealed with no built in DSP.
Your prior model of the SP 10 coupled with the two VMP’s would be a fun sub to build... I’ve always wanted to play with that driver, but it would be admittedly hard to spend that kind of $$ on venting.. still! Thanks for your assessment.

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post #37 of 47 Old 07-26-2013, 07:17 AM
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That SP10 model only used a single PR. Some careful considerations would have to be made during box construction.
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post #38 of 47 Old 07-26-2013, 09:23 AM
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Originally Posted by Jay1 View Post


This woofer
http://www.parts-express.com/pe/showdetl.cfm?partnumber=297-460

This PR with 750g mass added
http://www.parts-express.com/pe/showdetl.cfm?partnumber=293-680

In a 14" cube with 800 watts





Not saying this would specifically be better then the JL, just that subs like this are completely possible. You can see the price of the PR, and why they are not used wink.gif

That's pretty interesting. Is that with 2 PRs? I assume you are within excursion limits at the spl you're showing there.

Ive never done a PR, buy I have thought about it as the ports start to get bigger. I stopped at 10 ins myself wink.gif Thats an eighteen that the flange is sitting on. Makes for a big box for sure.
Not real practical.

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post #39 of 47 Old 07-26-2013, 09:28 AM
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Ive never done a PR, buy I have thought about it as the ports start to get bigger. I stopped at 10 ins myself wink.gif Thats an eighteen that the flange is sitting on. Makes for a big box for sure.
Not real practical.

eek.gifbiggrin.gif How much you pay for that port Tack? I know that p$rt.. Lol

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post #40 of 47 Old 07-26-2013, 11:45 AM
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Originally Posted by Tack View Post

That's pretty interesting. Is that with 2 PRs? I assume you are within excursion limits at the spl you're showing there.

Ive never done a PR, buy I have thought about it as the ports start to get bigger. I stopped at 10 ins myself wink.gif Thats an eighteen that the flange is sitting on. Makes for a big box for sure.
Not real practical.


Pretty cool flare construction. Do you have more details on the build? A 10" port woul need some extreme length or a fridge sized box to get low.

The model shown was one pr with no excursion issues.
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post #41 of 47 Old 07-26-2013, 01:01 PM
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^^ I forget the companies name but they used to be around 10-15 years ago and made their splash offering large AL precision ports. They might still be around I dunno. Looks like maybe Tack built the flare himself?, but it does remind me of that Co. though.

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post #42 of 47 Old 07-26-2013, 02:58 PM
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I bought it from Carlos, formerly of Accupower, now experiencing an extended stay in the pokey.

I never built it after realizing how big it was going to be. I still have it, maybe one day Ill look into a sonotube build. The eight inchers I use are big enough.
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post #43 of 47 Old 07-26-2013, 03:40 PM
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Originally Posted by Tack View Post

I bought it from Carlos, formerly of Accupower, now experiencing an extended stay in the pokey.

I never built it after realizing how big it was going to be. I still have it, maybe one day Ill look into a sonotube build. The eight inchers I use are big enough.

Yeah Accupower, that’s it.. to bad about the poky though. wink.gif 8” is a very large port indeed!

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post #44 of 47 Old 07-26-2013, 03:59 PM
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wink.gif 8” is a very large port indeed!

Thanks for noticing. I have big feet too wink.gif

-OR-

Thanks, I just had it stuffed!




20 -25 hz is all I ever tune to so they aren't real long. No port noise but its amazing how much wind comes out when you do get it loaded up.
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post #45 of 47 Old 07-26-2013, 04:10 PM
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Thanks for noticing. I have big feet too
wink.gif


Just don't call me Shirly. biggrin.gif
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its amazing how much wind comes out when you do get it loaded up.

Yes! its amazing how much wind comes out when you do get it loaded up. smile.gif

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post #46 of 47 Old 07-26-2013, 04:26 PM
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You are making a killing around here today Steve smile.gif
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post #47 of 47 Old 07-26-2013, 04:35 PM
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You are making a killing around here today Steve smile.gif

You know Tack! maybe you have a good point there. cool.gif

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