My multi location subwoofer thread inspired by Welti,Devantier,Geddes !!! - Page 3 - AVS Forum
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post #61 of 191 Old 01-06-2012, 11:54 AM - Thread Starter
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I shipped my OM back to PE for a tune up. Hopefully a couple week turnaround......

Any chance i can cheap out and pick up a pro audio 12" driver for less money and more sensitive, like 98db/spl.
It would require lower power from an amp.....we're only talking 40hz-80hz......
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post #62 of 191 Old 01-06-2012, 12:15 PM
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Quote:
Originally Posted by noah katz View Post

Unlike the odd-order modes, they're not cancelled from opposite wall placement, nor fail to be excited by midwall placement.

Good points, I'm trying to take in all I can wrt acoustics,...it's like a fractal, the more I learn, the more I learn I don't know


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Originally Posted by noah katz View Post


See the paper for more explanation.

What paper?


Thanks

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post #63 of 191 Old 01-06-2012, 12:32 PM
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Quote:
Originally Posted by kgveteran View Post

If i can measure at my seating positions, and get a response that is workable, as i did, isnt that enough....

Absolutely.

Noah
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post #64 of 191 Old 01-06-2012, 03:06 PM - Thread Starter
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post #65 of 191 Old 01-06-2012, 03:07 PM - Thread Starter
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Quote:
Originally Posted by FOH View Post

Good points, I'm trying to take in all I can wrt acoustics,...it's like a fractal, the more I learn, the more I learn I don't know




What paper?


Thanks

The paper that Geddes wrote on his theory.....
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post #66 of 191 Old 01-06-2012, 03:13 PM
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Quote:
Originally Posted by kgveteran View Post

The paper that Geddes wrote on his theory.....

Got it, misunderstood

Thanks

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post #67 of 191 Old 01-06-2012, 03:21 PM
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Quote:
Originally Posted by kgveteran View Post

Any chance i can cheap out and pick up a pro audio 12" driver for less money and more sensitive, like 98db/spl.
It would require lower power from an amp.....we're only talking 40hz-80hz......

Yes, but remember the only way to get efficiency at low freq is with size; it would take a ported box of several cf.

Quote:
Originally Posted by FOH View Post

What paper?

Quote:
Originally Posted by kgveteran View Post

The paper that Geddes wrote on his theory.....

No, this one:

http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf

I believe Geddes more or less pooh poohs it, saying it's too idealized to work in real rooms.

Seems to work in mine though, and it's from from the closed rectangular room the theory is based on.

Noah
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post #68 of 191 Old 01-07-2012, 04:52 AM - Thread Starter
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Quote:
Originally Posted by FOH View Post

Good points, I'm trying to take in all I can wrt acoustics,...it's like a fractal, the more I learn, the more I learn I don't know




What paper?


Thanks

Dont even try to know less than me hahahahaha. i am the King at knowing less !!!!
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post #69 of 191 Old 01-07-2012, 07:54 AM
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Quote:
Originally Posted by kgveteran View Post

Dont even try to know less than me hahahahaha. i am the King at knowing less !!!!

I've been hanging out around the acoustics area here at AVS, GearSlutz, reading SAC, and many studio design engineering/architectural articles everywhere I can find them. I've been reading, re-reading, Toole's most recent book. I carry it and Everest's Master Acoustics book with me as I run errands etc., any extra moment I have I dig in.

Several months ago, I began performing a variety of long term experiments in my room. This began with a discussion/disagreement between myself, and Dennis Erskine. Ethan Winer chimed in, however he's been very busy with a book he working on (due out sometime soon). We started discussing Toole's assertion regarding first mirror point reflected energy in typical small rooms, and how one interprets that in their own room.

Since that brief exchange, I've taken down all my treatments and have been listening to different mains, in various situations. Diffuse, scattering, absorption, totally reflective, re-directive with the energy, etc., I haven't tried everything, but it's been fun trying the combos I have tried. Upon starting down this route, I decided to really dig deep and spend significant time on as many combos of acoustic models and environments. I've discovered some really cool aspects that apply to my room. I do measure, but I'm trying to assign characteristics for each avenue, at the LP in my room,..as that's all that matters. This isn't a dedicated room, it's a family room that all four of us share,..so everyone's been very patient thru this process.

All this theory, but what really matters is my room, at the LP. Each aspect impacts other elements, and many acoustic answers are "it depends"...true. I'm trying to determine new mains for purchase. I've considered tightly pattern controlled mains, but that un-necessarily limits lateral energy components,... which may or may not be needed. Yes, a tightly controlled directivity is ideal for many apps. But too much pattern control, in the wrong room, doesn't allow you to utilize the side wall interaction if you need it. From what I've discovered in my room, I want it available in a controlled amount.

-------

kgveteran
I really like those diffusers/scattering panels you made,...and the pics I've seen of your room. And when you began with your OmniMic work/subs, I was interested on seeing what you'd discover. Your small sealed filler subs will be quite interesting too. I think they need to be fairly robust, but nothing exceptional. I'd want them to do more than just fill in. Just my approach, my 2 cents I certainly not the most savvy small sealed DIY'er around.


Continued good luck, sorry for the OT

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post #70 of 191 Old 01-07-2012, 11:03 AM - Thread Starter
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here is a quick sketch of my first subwoofer. with bracing i should still be over 1.5 cu ft. Internal volume needs to be bigger for bracing and amp, and driver. I ended up with 30" lenth and 18" height ( new pic to come )



if you want i can send you the plans to my diffusers. they are random depth and they have been critisized for this. i think they work great though.....
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post #71 of 191 Old 01-07-2012, 12:02 PM
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Quote:
Originally Posted by noah katz View Post

Yes, but remember the only way to get efficiency at low freq is with size; it would take a ported box of several cf.





No, this one:

http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf

I believe Geddes more or less pooh poohs it, saying it's too idealized to work in real rooms.

Seems to work in mine though, and it's from from the closed rectangular room the theory is based on.



Geddes can have pretty incisive words, and tends to dismiss much of what does not align to his product line.

I use the Toole/Welti/Devantier method, and it works for me. My subs are at the front wall's 1/4 points. At some point, I do want to add some rear subs.

Either method works. The one thing both have in common is measurement to confirm....the most impotant part, IMO.

JSS
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post #72 of 191 Old 01-07-2012, 12:14 PM - Thread Starter
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Quote:


Either method works. The one thing both have in common is measurement to confirm....the most impotant part, IMO.

Now with the OM, i will be able to document with out doubt. Looks like the 12" driver is out until Jan and the plate amp is out til march... Hohum... Really, March
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post #73 of 191 Old 01-07-2012, 01:01 PM
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Quote:
Originally Posted by FOH View Post

I've considered tightly pattern controlled mains, but that un-necessarily limits lateral energy components,...

This can be at least partially achieved by toeing them in, which will give a delayed reflection from the opposite side wall.

Noah
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post #74 of 191 Old 01-08-2012, 07:54 AM - Thread Starter
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Quote:


I use the Toole/Welti/Devantier method, and it works for me. My subs are at the front wall's 1/4 points. At some point, I do want to add some rear subs.
MaxMercy

I think my method will be a combination. Since my subs are front and center, welti would suggest a rear sub even out peaks and nulls.

I reread Geddes and see now that he uses three subs with corner placement starting off the process.

I'm in quite a state of "wait" now...patience..patience.....

...and with my smallish seating area i mite just get by with only one or two subs....
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post #75 of 191 Old 01-10-2012, 07:30 AM - Thread Starter
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So , am i over simplifying the multiple sub theory... I'm not filling in the null, I'm actually eliminating it, and combining the main subs with the AUX sub at the LP...
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post #76 of 191 Old 01-17-2012, 03:33 AM - Thread Starter
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PE was selling a 240 plate amp used on ebay 75.00 a Its the one that does not boost. Nice deal, now to get the DSP and the Dayton Driver....
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post #77 of 191 Old 01-22-2012, 03:57 PM - Thread Starter
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PE is now minus one RS 12" sub, should be here by weeks end...pick up the MDF tonite...
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post #78 of 191 Old 02-01-2012, 05:04 AM - Thread Starter
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Here's the final drawing


These drivers are pretty stout


Here's the amp, small ding in the fin


Here's the brace system


.....and the final project, sans the paint and bondo...that can wait
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post #79 of 191 Old 02-01-2012, 06:50 AM - Thread Starter
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So, after i ran some sweeps the proof is right there, as i moved the sub from wall to wall i could see on the graphs that at each location the null is filled in, but not seat to seat. Only way to smooth out the response is to build two more so all four wall positions are covered. I will confirm this by borrowing subs from my other systems and loading up my room.

Once i get the MiniDSP i will be able to tweak each subs response and delay.

My gut reaction is to cut up my four Tumults and end this madness right now!
I could build LT's for each cabinet and do this thing correct from the begining with the four outputs of the DSP.....I gotta sleep on this.....
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post #80 of 191 Old 02-04-2012, 06:24 PM - Thread Starter
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I guess it off to Lowes to get some more MDF to build two more cabs. Three of these will surround the seating position. The four Tumults act as one sub front center. Its response is flat from 10hz to 40hz, then it falls off due to the null.
Looking at some of the articles about multiple placement, i will be doing mid wall placements, not 1/4.
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post #81 of 191 Old 02-10-2012, 04:30 PM - Thread Starter
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Dont run sweeps without your mains and surrounds, I ran sweeps with just my subs and the response showed a huge null at 55hz. Then i clicked on one amp at a time, and the null was only about -8db ......

Dialed in the Aux Sub and it required very little gain to raise the response, but is Audyssey calibrating the sub all alone, and if so, it will not see the the increase added by the mains and surrounds......
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post #82 of 191 Old 02-21-2012, 05:13 PM - Thread Starter
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I disconnected my BASSIS and ran all four main subs, no EQ at all at the LP. This is the average at all three seats, while waiting for my MiniDSP. You can see the huge valley around 52hz.. That will fill in nice with my new subs.

What do you think of the graph ? 1/48th smoothing.. Impulse is at 5.0ms...

If you think something should be changed in my measurement settings let me know...

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post #83 of 191 Old 02-21-2012, 06:49 PM
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When the minidsp arrives I would try inverting the phase. I had a similar issue with my FR and once the phase was inverted the huge null had almost vanished. A few weeks back I spent a number of hours painstakingly changing the distance on my subs by .2 feet +/- to smooth out my FR at the crossover. I was able to achieve mildly acceptable results. It might be worth spending an hour or two to measuring and changing the sub distance.




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post #84 of 191 Old 02-22-2012, 04:37 AM - Thread Starter
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Here is a shot of a close mic sweep taken with no EQ



....and this is at the LP, check out the room gain.



Would you agree, that the smartest thing to do would be to create a filter to drop the peak to match the response below 40hz, instead of the usual boost the lowend ?????
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post #85 of 191 Old 03-04-2012, 09:55 AM - Thread Starter
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Slowest build thread project ever !!!! .... but it is moving forward :0)





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post #86 of 191 Old 03-09-2012, 08:44 AM - Thread Starter
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here are some pics of finished Sub #1, and where its going. No MiniDSP yet, second cab is finished but no parts yet. Slow going...



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post #87 of 191 Old 03-09-2012, 09:54 AM
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I have been following this for a while. I am very interested in seeing your results.
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post #88 of 191 Old 03-09-2012, 10:00 AM
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Quote:
Originally Posted by maxmercy View Post

Geddes can have pretty incisive words, and tends to dismiss much of what does not align to his product line.

I use the Toole/Welti/Devantier method, and it works for me. My subs are at the front wall's 1/4 points. At some point, I do want to add some rear subs.

Either method works. The one thing both have in common is measurement to confirm....the most impotant part, IMO.

JSS

http://www.aes.org/tmpFiles/elib/20120309/13680.pdf

I know what I will be reading today.
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post #89 of 191 Old 03-09-2012, 10:39 AM
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Looking good KG!!!
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post #90 of 191 Old 03-09-2012, 02:54 PM - Thread Starter
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Quote:
Originally Posted by filtor1 View Post

I have been following this for a while. I am very interested in seeing your results.

After being in this hobby for as long as I have and seeing different methods come and go, this is exciting....

Soon enough.....
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