Keager's Quad RE XXX 18 Underfloor IB Build - Page 5 - AVS Forum
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post #121 of 341 Old 05-28-2012, 11:22 AM
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Originally Posted by popalock View Post

Hummm, this is what the IB guys over at the cult suggested? I see now why I was a bit confused when you told us how you were mounting them. I've never seen this before.

Can you point me to a source that recommends this technique. I'd like to read up on it myself.

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Originally Posted by keager View Post

The main reason I'm mounting them this way is lack of space on one side. I don't think there is a large benefit or drawback acoustically. Possibly to balance out driver non linearity, which is something I'm not knowledgeable about.

Actually there is a benefit to mounting them this way. Just like keager mentioned it cancels out driver non linearity which will greatly reduce even order harmonic distortion. That said I'm pretty sure it's the odd order stuff that's been found to be the most audible/offensive. I did some googling for a reference but didn't find much. There's a reference at the link below under Compound ~ Push/Pull Dual Drivers but it mentions some think odd is cancelled while others think even:
http://www.danmarx.org/audioinnovation/theories.html

Here's an AVS post from a couple years back with some discussion as well (this one clearly states even and sounds pretty convincing):
http://www.avsforum.com/avs-vb/showt...6#post16482906



Here's a loose reference regarding even order vs odd order distortion in subs:

"Higher-order and/or odd-order harmonics have progressively lower allowable distortion limits, as these tend to subjectively be more offensive to the human ear than lower order and/or even-order harmonics."

Found near the bottom of this page:
http://www.audioholics.com/education...oofer-shootout
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post #122 of 341 Old 05-28-2012, 11:34 AM - Thread Starter
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Quote:
Originally Posted by lennon_68 View Post


Actually there is a benefit to mounting them this way. Just like keager mentioned it cancels out driver non linearity which will greatly reduce even order harmonic distortion. That said I'm pretty sure it's the odd order stuff that's been found to be the most audible/offensive. I did some googling for a reference but didn't find much. There's a reference at the link below under Compound ~ Push/Pull Dual Drivers but it mentions some think odd is cancelled while others think even:
http://www.danmarx.org/audioinnovation/theories.html

Here's an AVS post from a couple years back with some discussion as well (this one clearly states even and sounds pretty convincing):
http://www.avsforum.com/avs-vb/showt...6#post16482906

Here's a loose reference regarding even order vs odd order distortion in subs:

"Higher-order and/or odd-order harmonics have progressively lower allowable distortion limits, as these tend to subjectively be more offensive to the human ear than lower order and/or even-order harmonics."

Found near the bottom of this page:
http://www.audioholics.com/education...oofer-shootout

Thanks!
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post #123 of 341 Old 05-28-2012, 11:55 AM - Thread Starter
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And to clarify, mine are going to be wired reverse polarity to each other. So, both cones will be moving in opposite directions, like a traditional dual opposed. Just one driver is facing the other direction.
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post #124 of 341 Old 06-02-2012, 04:09 PM - Thread Starter
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Well I got the first manifold over to the location. Past water pipes and heater ducts. Have some "excavation" to do tonight to give me a little space to twist and turn the manifold to allow me to install the drivers and slide it in place. Very tight fit, but I think it will work. I'll take some pictures later. The manifold will pretty much be wedged between the ground and the floor joists.
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post #125 of 341 Old 06-02-2012, 04:20 PM
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You won't want to have the enclosure sitting on the ground though. Unless you weather proof it the wood will absorb the moisture from the ground and rot the wood.
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post #126 of 341 Old 06-02-2012, 04:27 PM - Thread Starter
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Yes, the ground has thick black plastic over it. Im temporarily moving the plastic to do some digging, then its going back in place. The area I live in is a high desert, but I agree with you completely.
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post #127 of 341 Old 06-02-2012, 05:07 PM
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Originally Posted by keager View Post

Yes, the ground has thick black plastic over it. Im temporarily moving the plastic to do some digging, then its going back in place. The area I live in is a high desert, but I agree with you completely.

Thats pretty much how you know this is a hardcore build! Digging to make room for more subs lol, not sure if i could sell the wife on this.

Do you have pictures of said location and clearance issues? Im sure lugging the baffle with woofers is a pita for sure.
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post #128 of 341 Old 06-02-2012, 06:45 PM - Thread Starter
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Thats pretty much how you know this is a hardcore build! Digging to make room for more subs lol, not sure if i could sell the wife on this.

Do you have pictures of said location and clearance issues? Im sure lugging the baffle with woofers is a pita for sure.

Hope to have some pictures tonight.
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post #129 of 341 Old 06-02-2012, 09:38 PM - Thread Starter
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here's some lousy pictures of under the house and the manifold sitting approximately where it will be mounted. More progress tomorrow.


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post #130 of 341 Old 06-03-2012, 02:36 AM
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This is all sorts of awesome. Kudos to you keager for going the extra mile for what is bound to be some awesome bass!

I do feel a bit sorry for your crawlspace situation though, I can't imagine what a PITA it must be to get those beasts in place.

Subscribed for sure, can't wait to see the rest of this build!

"Measure twice, then measure again. Only then should you even THINK about cutting."

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post #131 of 341 Old 06-03-2012, 03:44 AM - Thread Starter
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Thanks man!
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post #132 of 341 Old 06-03-2012, 06:27 AM
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Thanks man!

Looking good buddy. Hey, did you get my PM response? I tried to write you back twice. Let me know.
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post #133 of 341 Old 06-03-2012, 06:36 AM
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Originally Posted by keager View Post

here's some lousy pictures of under the house and the manifold sitting approximately where it will be mounted. More progress tomorrow.

Wow, what dedication. That must be a PITA working with that weight in that space. Are you going to use a small bottle jack to get those into place? This is very cool. I would love to near this when it is completed.
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post #134 of 341 Old 06-03-2012, 07:27 AM - Thread Starter
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Originally Posted by btinindy View Post


Wow, what dedication. That must be a PITA working with that weight in that space. Are you going to use a small bottle jack to get those into place? This is very cool. I would love to near this when it is completed.

I dont think I will need a jack. Gonna put the drivers in, which will basically have them resting on the ground, then hopefully shimmy and pry the manifold in place while a put in a few screws. Guess I'll find out...
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post #135 of 341 Old 06-03-2012, 07:51 AM - Thread Starter
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Can somebody explain a little in 4th grade terms how to read the impedence graph in WINISD? The numbers on the verticle axis don't correspond to any numbers I recognize. I am not sure what it means. trying to get an idea of the impedence of the XXX's. I know wired in series just sitting there are 4.2 ohm, but there is more to it than that, right?
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post #136 of 341 Old 06-03-2012, 08:09 AM
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i did something similar to this about 12 years ago when i moved into my house.

Only i was above a poured concrete basement, and the floors had not gone down yet, so i was able to work in the confines of an air conditioned home.

Bottom line is the bass sounded excellent, and the next time i get the bog to upgrade my subwoofer, i will go back to building it into the floor.

Tim
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post #137 of 341 Old 06-03-2012, 08:19 AM - Thread Starter
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Originally Posted by tundrSQ View Post

i did something similar to this about 12 years ago when i moved into my house.

Only i was above a poured concrete basement, and the floors had not gone down yet, so i was able to work in the confines of an air conditioned home.

Bottom line is the bass sounded excellent, and the next time i get the bog to upgrade my subwoofer, i will go back to building it into the floor.

I'm very interested to hear it myself. From what I've heard, IB subs sound far better than boxed subs. Hopefully other members in Oregon can take a listen as well. Seems to be an AVS desert of sorts.lol
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post #138 of 341 Old 06-03-2012, 10:02 AM
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i would love to have a crawlspace or basement like that. hell even a usable attic would be friggan sweet. darn arizona homes where you have to hit that 350K pricepoint before you get a basement
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post #139 of 341 Old 06-03-2012, 10:15 AM - Thread Starter
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i would love to have a crawlspace or basement like that. hell even a usable attic would be friggan sweet. darn arizona homes where you have to hit that 350K pricepoint before you get a basement

I definitely have the bare minimum in height down there. In central oregon here it is volcanic, and extremely rocky. Thus, its an act of congress to dig deep enough for a basement or deep crawlspace. I envy alot of the older houses on the east coast with basements ti turn into a theater. I just subtly(not) weasled my high powered audio gear into the living room/kitchen area. I like that, because you can watch movies and listen to music while doing the dishes etc.errr I mean ordering the wife to do dishes.lol
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post #140 of 341 Old 06-03-2012, 11:00 AM - Thread Starter
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Originally Posted by keager View Post

Can somebody explain a little in 4th grade terms how to read the impedence graph in WINISD? The numbers on the verticle axis don't correspond to any numbers I recognize. I am not sure what it means. trying to get an idea of the impedence of the XXX's. I know wired in series just sitting there are 4.2 ohm, but there is more to it than that, right?

Anybody have time to try to explain this or possibly a helpful link? Thanks!
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post #141 of 341 Old 06-03-2012, 01:46 PM
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Originally Posted by keager View Post

Anybody have time to try to explain this or possibly a helpful link? Thanks!

Horizontal axis should be frequency and vertical axis is impedence in ohm. So if I put in 4 XXX 18's in a 40000l enclosure I see from around 50hz and up it's right around that 4.2 ohm but below 50hz it starts rising to a peak of 38.5 ohm right about the resonant frequency of the "enclosure" which ended up being ~16hz for my 40kL enclosure. This is what Ricci mentioned earlier in the thread

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These are a 4.2 ohm DCR so in an actual enclosure the lowest effective impedance that you will ever see is maybe 4.4-ish with all 4 wired mono. Most of the pass band will be well above that.

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post #142 of 341 Old 06-03-2012, 01:52 PM - Thread Starter
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Originally Posted by lennon_68 View Post


Horizontal axis should be frequency and vertical axis is impedence in ohm. So if I put in 4 XXX 18's in a 40000l enclosure I see from around 50hz and up it's right around that 4.2 ohm but below 50hz it starts rising to a peak of 38.5 ohm right about the resonant frequency of the "enclosure" which ended up being ~16hz for my 40kL enclosure. This is what Ricci mentioned earlier in the thread

Gotcha. Thanks!
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post #143 of 341 Old 06-03-2012, 02:19 PM - Thread Starter
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Thats why he said he would run my existing amp in 4 ohm mono. I plan on crossing them at 60 hz, so really between 50 and 60 hz would be the problem area. Is that kinda on track? Of course he made the disclosure of him being crazy too.
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post #144 of 341 Old 06-03-2012, 09:29 PM - Thread Starter
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Too late to turn back now...

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post #145 of 341 Old 06-04-2012, 02:25 AM
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Too late to turn back now...

Point of no return...

Seems like it's going to get much more difficult before you cross that finish line.

We're all looking forward to seeing this one through with you man.
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post #146 of 341 Old 06-04-2012, 02:44 AM
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Be sure to get the grate on there before any small animals jump down there... I'm not sure they'd enjoy it down there once you're done :P

I'm also in Oregon, and I'd love to hear this system when you're done. I've got the DIY itch again, and I'm contemplating an IB setup.

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post #147 of 341 Old 06-04-2012, 06:44 AM - Thread Starter
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Be sure to get the grate on there before any small animals jump down there... I'm not sure they'd enjoy it down there once you're done :P

I'm also in Oregon, and I'd love to hear this system when you're done. I've got the DIY itch again, and I'm contemplating an IB setup.

Youre probably right, small animals, neighbors, lowflying aircraft, are all going to be a bit upset when I flip the switch. Glad there's a fellow oregonian around!
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post #148 of 341 Old 06-04-2012, 03:16 PM - Thread Starter
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So I'm going to order a 10000q clone amp soon, and I need to make sure I have connectors etc to connect from my minidsp 8x8(not hooked up yet) and my new amp. Would I be better off running 4 ohm stereo using all four channels or going 8 ohm bridged?
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post #149 of 341 Old 06-04-2012, 03:31 PM
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so i'm going to order a 10000q clone amp soon

yes!!!!!
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post #150 of 341 Old 06-04-2012, 03:46 PM - Thread Starter
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yes!!!!!

Better talk to popalock before you get too excited. He was first in line by hours.
First come, first serve.
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