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post #1 of 8 Old 09-20-2013, 06:14 PM - Thread Starter
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I'm building some dual opposed builds using sonotubes (circular enclosure). One firing up, and one firing down. The location I plan to put them is going to be directly under my main right and left speakers.

Will this adversely affect the acoustics of my main left and right?

Here's a picture. I figure the top woofer will be about 4-5" from the bottom of the main speakers enclosures.


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post #2 of 8 Old 09-22-2013, 05:32 AM
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I just read your stereo-integrity-18s-6-in-sono-tubes build thread, nice project.
(you should put live links in your SIG for that)

Sound waves above the transition frequency, approx 300hz, travels in straight line, hence we can use ray tracing to figure things out.
That is a false wall for AT Screen I gather? Are those sono-tube subs location fixed or can you tweak them to not be directly under your mains?

It really depends on where those sonotubs are located and your horn freq dispersion characteristics, if they are below and in front of those lower horns, you might have some un-desired reflections off them, then off your ceiling, then to your ears that "compete" for your ears attention with the direct sound.

Since I'm guessing you do not have the 3D polar plots of those speakers characteristics - and time for CAD analysis then, trial and error using ETC charts seems easiest, and you might have to apply some small acoustic treatment to your ceiling then. Or even put acoustic treatment on top of those sono-tubes to eliminate them right away.

Ideally, the design characteristics of those horns minimize up/down dispersion, however being so close to them you probably will have un-wanted early reflections to deal with.
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post #3 of 8 Old 09-22-2013, 10:44 AM - Thread Starter
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Thanks for your reply, and the suggestion. I will do so right after I finish this post. smile.gif

So.... the concern is actual reflection from the tweeter off the top of the sonotube baffle... gotcha.

I wasn't sure how all that air mass being output right into the path of the tweeter would affect the sound, if at all. I completely forgot about the reflections from the tweeter due to it being so close.

When I installed the mains on the ledge I made sure the cabinet hung over to avoid just exactly that. Reflections off the ledge.

The screen is AT, but I'm pressed for distance from seat to screen so It's back up a few inches from the center. So no room for the tubes behind the screen.

I can put treatment on top of the baffles but won't the sound reflect off the woofer too?

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post #4 of 8 Old 10-13-2013, 07:57 PM - Thread Starter
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This is how they land. No way of putting insulation around the baffles.


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post #5 of 8 Old 10-21-2013, 06:19 PM - Thread Starter
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163 views and one reply. lol..... the acoustics section is a special place.......smile.gif

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post #6 of 8 Old 10-22-2013, 12:01 AM
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Quote:
Originally Posted by pdxrealtor View Post

163 views and one reply. lol..... the acoustics section is a special place.......smile.gif

well now 175 views...
No, you obviously don't want to put anything to cover your subwoofer driver, ditch the acoustic treatment on top of those sono-tubes.

From your front view picture, I'm guessing from side view your RH/LH speakers are about 60-70% or so in front of your suboofer, so most likely you won't have much reflection issue with the mid-hi freq from those horns.

Only fact based way is to use REW, take ETC charts, and see if the reflections show up at your seating position(s).

Just a thought, why is your horn on the bottom?
If you flipped those 180 and horn on the top, then angled them slightly down at your HT seating then I'm guessing that would help mitigate any potential reflections off your sonotube baffle.
By Increasing the distance and angle from your horn to the top of your baffle.

In the end, not something to lose sleep over, just a minor/slight acoustic issue really.

btw, your avatar "Bass Fishing... Pro Angler", cool - you make your living fishing! Are you are writer for fishing magazines?
I have an 18' Four Winns bow rider with 190hp 4.3L V6 - not a dedicated fishing boat but good all around family boat
My 2 boys 9 and 11 love fishing with me on weekend camping trips.
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post #7 of 8 Old 10-22-2013, 12:28 AM - Thread Starter
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I actually got them pushed over so the driver center is under the outer port.

The speakers are upside down, because that ledge they are sitting on is over 50" from ground level. Placing the speakers right side up would put the tweeter over 6ft high.

I went round and round trying to figure out the best placement for those speakers while still keeping the tweeter as close to ear level as possible. Even talked to jbl cinema audio support. Theres a slight angle on them as they sit, i tried with more angle but they were too harsh with the tweeter aimed directly at ear. Currently they are slightly off axis. Amazing what such small adjustments make.

Anyways..... I was worried about the air produced by the subs might some how affect the audio coming out of the mains.

Ill use REW and do as you suggest. I just got my first reflection panels done.... 4" OC703 and a 3.5" air gap. Couple more things to do and Ill be ready to get some serious 'whole system' tuning done.

My avatar means bass as in speaker bass. smile.gif I don't really fish at all.

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post #8 of 8 Old 10-22-2013, 12:29 AM
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Ok - just saw this at your build thread, I usually see horns on the top, not bottom.....thought I was not seeing right. rolleyes.gif

Possible for you to flip them back "right up" and try your listening again?

[edit] I post this same time you posted above.....

Quote:
Originally Posted by pdxrealtor View Post

I got the L/C/R installed. The center is dead center and the left and right are spaced 10'6" a part.

As you can see they are placed upside down to keep the tweeter close to ear level. This was done to place the speakers on my foundation ledge which got me an extra foot of viewing distance.

I read for a few hours on the internet and then finally called JBL PRO tech support. They confirmed what I had been reading and that is I would have no ill affect having them upside down.

I used a laser device to align the tweeter angle at ear level and listened for a while. Toed in and no toe in. They sounded harsh (is 'bright' the word you use?). So I decided to take away most of the downward angle and give them a shot. Night and day difference. Much smoother sounding, yet still articulate.

In the end they are toed in as much as possible with my situation, the back side is measured at 5" off the back wall and both speakers are precisely aimed and the exact distance to the LP is the same for both L/R speakers.

***Tip***- to angle them forward I used composite shims found at Home Depot. These are what you use when install door jams, windows, etc. Get the composite ones, they are all identical where the wood ones vary in thickness.

Here's a picture of one tilted forward so tweeter aimed directly at ear level. As I said above, I ended up taking 99% of this angle out.





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