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Old 20th July 2015, 04:53 AM   #1
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Default room resonance

Hey guys I want to know why there's specific resonance spots in my room with some frequencies... yesturday I was outside with my 2 THAM12, I set the EQ to fla the responce... I worked with the spl and everything was ok, not perfect but near.... now I'm in my room... I'm listening Californication_RHCP and it's really bad!!! Here's a drawing of my room... It's not the right dimenssions but it's just to show you where I got this nasty resonance! almost every place in my room got a little bass boost! but in front of the subs (the rejet line in front on the subs) there's no bass! it's hard to explain... english isn't my primary language! at 1 feet these bass but at 1M there's not! it's only the first meter in front of the sub but I think it's the enclosure that blocks... Maybe if I post a video you could understand better so I will do this tomorrow morning!
anyway... what can I do to remove this... More EQ? I can't make bass trap because there's my bed and my desk there... I would like to have a flat responce in my door too... but even when I EQ...some frequencies are stronger! I found this online...amroc - the room mode calculator when I enter my room dimensions (16X12X8) its about the same frequencies that resonnate that the site told me!

Thanks for your help, it's still me I got a lot of post here but it's never the same problem ahahaha my bad for this
and sorry for my bad english if you need a video or a more detailed sketchup plans of my room I'll do it! I don't this the problem is the tham12's... It's the same when I use my 15's...
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Old 20th July 2015, 07:12 AM   #2
sine143 is offline sine143  United States
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Inside a room, particularly a small one, the Room resonances DOMINATE response.

all you can do is move the enclosures (either coupled, or disperesed) around the room till you optimize the response at your desired listening positions. the frequency location and magnitude of the resonance effect will change as you change the location of your listening position... so you really need to pick 1 or 2 spots where you will get things set up to sound "good"
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Old 20th July 2015, 07:43 AM   #3
djk is offline djk
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Put the speakers where you want to listen, then move around and listen in the proposed speaker locations.

Move the speakers into the location that sounded the best.
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Old 20th July 2015, 01:44 PM   #4
Zwiller is offline Zwiller  United States
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To expound on sine, a small room is defined by acoustic engineers as < 1,500ft3. Pretty much anything you do in such a room is just one big juggling act and in the end you will just have to live with some of it. Does not surprise me at all that the best sound is nearest bed and closet which are basically bass traps and also that the worst areas are in the corners where the rooms modes are most dominant. Something that may interest you is the Geddes Lee method. Which from my limited research, is using 2-3 subs in strategic locations in the room which effectively assist in "equalizing" the modes. Never tried it myself, but there are some fanatics. EQ can help but will need to be a decent unit so you don't carve too much out of the signal. One nice corner trap near desk might help a bit too.
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Old 20th July 2015, 04:34 PM   #5
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ok so all I can do is move the subs until I got something better? ok I'll do this right now and after this i'mgonna do some testing I'll keep you informed!
thanks
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Old 21st July 2015, 04:48 PM   #6
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Default Geddes was right

I had 2 Lab12 based subs (OD-ML-TL's) sitting right next to each other and only 7 or 8 feet from my listening chair.
I was feeding them about 300W each maximum, 20-70 Hz, but only this much on widely spaced transients.
The subs where overwhelming and I usually did not even turn them on.
Then I moved them to each side of my room, 20 feet apart.
Now they blend in, they don't overwhelm the rest of the system.
When there is allot of LF content, they are definitely there.
But they sound so much more natural.
I couldn't be happier.
Moral of story.
Location, Location, location

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Old 23rd July 2015, 02:41 AM   #7
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thanks dave! I'll see whatr I can do but my room is already really full :P

Ok I have another question, this is not the same but I don't want to start a new post just for this.
Today I built a Bandpass 6th with a car subwoofer... 12"
It's ok, seriously I'm a bit mad about the result but the woofer are SCRAP!!! Legacy LW129X see the picture for the specs!
The front chamber is 17L tune to 80hz and the rear chamber is 70L tune to 29hz! It's my first Bandpass! so it was a try! It was not super on simultion but I change the 100L vented box because the woofer is so cheap that we can hear it moves! like a flapping noise! and I've try to seal it all the way and it wasn't better.
My goal was to get a got 40hz, the rest wasn't so important! see the simulation for details and there's also the plans! the box is 55cm tall and 52cm inside! what you see is just the botton, on it these is all the 52cm high panel plus the top panel! it makes about 17L and 70L on back if I don't miss something! I know that 80hz on the sim was only 100dB but in real life, it's about 60dB and 50hz is about 99dB max! and for the 30hz, I almost can't hear it... at 130hz it's 110dB but for a such big box (for a 12") I don't want a good 130hz, I want I good 40hz!!!
I don't think that the box is the problem, in the Legacy brochure, they told to cut a 11.57" (29,39cm) hole for the speaker so I did it and the speaker was almost falling down! It was too big! so maybe all specs are wrong? THANKS for your help, maybe the problem is small.

PS all mesurements are a 1W at 1 feet INDOOR in halfspace... this projet is really not my best one
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Old 23rd July 2015, 03:47 AM   #8
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Some notes:

1. With such a high Q, a 4th order BP box may be a better fit for that car audio subwoofer.
2. With the specs given, a quick HornResp sim with Vf=Vr=40L and vented with a 260 cm^2 vent that's 40 cm long should give you the 40 Hz, 93dB/2.83V/1M. Might be slightly less due to losses.
3. Make sure that all joints are airtight, and that includes the one around the driver. Even minor leaks can significantly reduce performance at low frequencies.
4. If you want even more LF performance out of the box, try a "trick" Kef used in some of their designs - add a small vent between the two internal chambers. Make the vent long and then cut it down to taste.
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Old 23rd July 2015, 04:03 AM   #9
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Quote:
Originally Posted by Brian Steele View Post
Some notes:

1. With such a high Q, a 4th order BP box may be a better fit for that car audio subwoofer.
2. With the specs given, a quick HornResp sim with Vf=Vr=40L and vented with a 260 cm^2 vent that's 40 cm long should give you the 40 Hz, 93dB/2.83V/1M. Might be slightly less due to losses.
3. Make sure that all joints are airtight, and that includes the one around the driver. Even minor leaks can significantly reduce performance at low frequencies.
4. If you want even more LF performance out of the box, try a "trick" Kef used in some of their designs - add a small vent between the two internal chambers. Make the vent long and then cut it down to taste.
1.I've not try 4th order because I can't find a good compromise between size and output, so I didn't try it! maybe next time!
2. Yeah but Vf=17L and Vr=70L ports are 104cm^2, I want to use this for movies! only movies! cost me a total of 65$ and about 2 days because I had to design a trap to put the speaker in and I had to cut a new speaker panel because the hole was too big for the speaker! what can I do now with this box?
3. the trap I talk about in #2 is probably not sealed right at this moment! but all joints are well sealed I put I lot of glue before I put on the top! but maybe there's some leaks were there's the driver!
4. Are big should I try to make them? the problem in general isn't the ouput itself... because I think I could listen to movies with it but the 80hz is really bad...


Do you have an idea, just like that with the box size and everything, what other driver can I use (the more cheap, my budget is already tight!)

thanks for your help tomorrow I'll try to make I work better!

PS: during the try I heard a compression in the port on the front chamber, why?
PPS: The box make some wierd noise at 30hz, like if something was flapping but everyting is tight is this box! I put a screw every 2 inch... the wood was drilled before, but when I bought it, it was curved, maybe this affects a bit too..?

thanks it's really cool to share your knowledge!
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Old 23rd July 2015, 04:39 AM   #10
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Hey I've sim the same box without the rear port (to make a 4th order) and it's about the same! there's no "peak" at 40 like with the 6th order! but Hornresp is more precise than WinISD so tomorrow I'll see what it gives me without this rear ports! hope I can get the 65-90hz frequencies flat with the rest of the bandpass!! I'll keep you inform
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