Topic: Subwoofer Problem in Sealed Room (Good Bass When Door is Open)

[Lancito]

I am currently having bass problems with my sealed dedicated AV room approximately 22 square meters.  When the room door is open, I have excellent bass response in my MLP.  When I close the door and use the air conditioner, I lose the bass.  Not sure if bass cancellation or bass cannot escape out of the room. Maybe someone can give tips how I can have good bass response even if the door is closed.

My set up :
-  Running dual SVS SB13ultras
-  Fronts PSB Imagine T, PSB Imagine center, PSB Image S5 surrounds (crossed at 80hz, LFE 120Hz)
-  Marantz 6010 receiver (Audyssey MultEQ XT32)
-  Auralex foam bass traps in all corners of the room

Below is the illustration of the room. (not to scale)

I look forward to tips and suggestions.

Regards.
 

[dm1179]

Do other family members observe the same? Have you tried different listening positions? Have you tried changing the location of the subwoofers?

Multiple Subwoofer Placement (Rules of Thumb)
In most circumstances two subwoofers will perform better than one. While you might assume this is for added SPL, the greatest benefit will actually be smoother bass response. Two subwoofers are easier to place and result in a flatter frequency response and creation of a much larger “sweet spot” for everyone in the room to hear smoother and more consistent bass.

For maximum output, some experts suggest that you put a single subwoofer in a corner for maximum output and place a second one in a less reflective area to smooth out the response. You can use the “crawl around the room” technique as described above for determining the location of the second subwoofer, except in this case, look for the minimum amount of bass output.

Dr. Toole suggests that in a rectangular room you should put one subwoofer close to the front wall in the middle, and another subwoofer at the back of the room in the same relative position. THX recommends placing them in the middle of the left and right walls. Dr. Toole also recommends some equalization to flatten the bass response so that all the seats in the primary listening area hear solid and even bass.

A Guide to Subwoofers (Part II): Standing Waves & Room Modes
http://forum.blu-ray.com/showthread.php?t=48286

Every wave has a wavelength—the physical distance that wave travels in the room is the time it takes to complete one cycle of vibration. Since low-frequency waves vibrate more slowly than mids or highs, their wavelengths are longer. Mids and highs may have wavelengths of anywhere from a few inches to a few feet, but lows often have wavelengths that approach and exceed the room dimensions themselves. When such a wave reflects between two parallel surfaces in a room, it doubles back on itself, causing interference, in the form of reinforcements and cancellations, at the particular frequency associated with that wavelength.

When this happens with mids and highs, these cancellations and reinforcements are distributed throughout the room. However, with longer, low-frequency waves, the cancellations and reinforcements are localized to specific areas in the room. The result is that the bass response of the room is uneven at certain frequencies—there will be too much bass at a particular frequency in some spots in the room, and not enough at others.

Studio Acoustics Part 2: Standing Waves
https://ask.audio/articles/studio-acoustics-part-2-standing-waves

[Lancito]

Thanks for the reply.

Everyone in my house notices the change in bass when the door of the room is shut.

I only have one listening position. I have yet to try other sub locations. However, I don't see how changing sub placement will change if it is okay when the door is open.

[sientobente]

Based on the illustration, it seems like bass reflects on the door when it's open which is why it amplifies the sound. Plus the material the door is made, which I assume is wood, that probably is the best material for bass to bounce off with.

I also noticed that there are bass traps on the diagram? Not sure if it is, but subs love corners for reflections. Bass traps reduce the LF.  You can try interchanging the position of those subs with your front speakers, moving them next to a corner then removing those traps. To reduce localization, set the crossover cutoff of your SVS lower(around 30hz), then let the fronts handle the upper bass.

[qguy]

Try relocating one of the subwoofers, try placing one on  the long wall. Since equidistant yung sub 1 and 2, yung dead spot nya would be identical...

[mykel18]

Run Audyssey then increase the bass from there.


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[Lancito]

Based on the illustration, it seems like bass reflects on the door when it's open which is why it amplifies the sound. Plus the material the door is made, which I assume is wood, that probably is the best material for bass to bounce off with.

I also noticed that there are bass traps on the diagram? Not sure if it is, but subs love corners for reflections. Bass traps reduce the LF.  You can try interchanging the position of those subs with your front speakers, moving them next to a corner then removing those traps. To reduce localization, set the crossover cutoff of your SVS lower(around 30hz), then let the fronts handle the upper bass.

Yes, those are bass traps. Although, Auralex foam traps don't really work at 100hz and lower.

I'll move the subs where the front speakers are. I hope there will be an improvement.

When you say "set the crossover cutoff of the SVS to 30hz" you mean set the crossover of the front speakers to 30Hz?

[Lancito]

Try relocating one of the subwoofers, try placing one on  the long wall. Since equidistant yung sub 1 and 2, yung dead spot nya would be identical...

Is it better than moving both subs to the front corners?

[Lancito]

Run Audyssey then increase the bass from there.


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Yes, that's what I did. Ran Audyssey with door closed. Bass still better when door is open after Audyssey. Using a SPL meter, 75dB at listening position. Nasasakal ang subwoofer kung sarado pinto. Parang cant move the air inside the room dahil maliit.

[qguy]

you can try moving both to the corners, its free

Is it better than moving both subs to the front corners?

[sientobente]

Yes, those are bass traps. Although, Auralex foam traps don't really work at 100hz and lower.

I'll move the subs where the front speakers are. I hope there will be an improvement.

When you say "set the crossover cutoff of the SVS to 30hz" you mean set the crossover of the front speakers to 30Hz?

Actually, I just mentioned that if the sub positioning now will make your bass a lot louder.

If ever it does, manual tuning is tricky to avoid localization. Although most people won't recognize where a below 40hz sound would be coming from, there is still a way to integrate the fronts with subs. Looking at the frequency response of the front speakers, Stereophile's measurement shows it is around 45 to 50hz. This may not be the perfect data though since it also varies per room. So it is really a trial and error process.

Pretty hard to explain, it is easier if I am there so I would know how sound interacts with the materials around your place. It will be nice too if you have an RTA. By the way there is an RTA app in iOS and a microphone that you can buy to connect to an iphone. Hehe. So assuming we have those, when you see the front speaker's FR starts to pick up at around 45hz, then set the crossover that way. Then on the sub, if it's FR starts to drop at 35hz, adjust it from 35 to 40hz. It's not a perfect science though, it is still trial and error. The key is to match where both points fall off, but we have to remember that even if it is the roll off point, there is still sound so crossing over both can still amplify the frequency in between. I hope I am making sense LOL.

By the way, I noticed that you got a carpet infront of the subs, those are additional sound absorping materials. So moving the subs to corners will be your best bet.

[mbtorn]

you can try moving both to the corners, its free

+1...exchange the position of your fronts with the position of your subs.

[Nelson de Leon]

You can also try using a single sub just to test if ganun din ang effect.
Have you tried moving your listening position more to the back?

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[Lancito]

Update : corner loaded both subs as suggested but bass became boomy and one note. Then from the original location, I pulled the subs away from the front wall around 12 inches. Big big improvement. Although not perfect, it is acceptable. I'll re-run Audyssey tomorrow to see if it improves further. Thanks for all the help.

[Lancito]

Actually, I just mentioned that if the sub positioning now will make your bass a lot louder.

If ever it does, manual tuning is tricky to avoid localization. Although most people won't recognize where a below 40hz sound would be coming from, there is still a way to integrate the fronts with subs. Looking at the frequency response of the front speakers, Stereophile's measurement shows it is around 45 to 50hz. This may not be the perfect data though since it also varies per room. So it is really a trial and error process.

Pretty hard to explain, it is easier if I am there so I would know how sound interacts with the materials around your place. It will be nice too if you have an RTA. By the way there is an RTA app in iOS and a microphone that you can buy to connect to an iphone. Hehe. So assuming we have those, when you see the front speaker's FR starts to pick up at around 45hz, then set the crossover that way. Then on the sub, if it's FR starts to drop at 35hz, adjust it from 35 to 40hz. It's not a perfect science though, it is still trial and error. The key is to match where both points fall off, but we have to remember that even if it is the roll off point, there is still sound so crossing over both can still amplify the frequency in between. I hope I am making sense LOL.

By the way, I noticed that you got a carpet infront of the subs, those are additional sound absorping materials. So moving the subs to corners will be your best bet.

Thanks sir, I am afraid to lose the punch if I crossover too low. I'll experiment but I never cross the fronts lower than 60hz. No problem to try. Thanks again.

[Gino]

A room with an opened door is a bigger room. The open area of the door is not reflecting back sound energy like a wall does.

The issue is room acoustics. The minimum room size that is treatable for very good bass is 17' wide x 23' long x 10' high. Any smaller and bass cannot be made perfect simply because there is no space for effective bass treatments.

For smaller rooms, you can treat for incremental changes but it will never be perfect. Move the sub in every possible position until it sounds best. Tune and move on.

[Lancito]

A room with an opened door is a bigger room. The open area of the door is not reflecting back sound energy like a wall does.

The issue is room acoustics. The minimum room size that is treatable for very good bass is 17' wide x 23' long x 10' high. Any smaller and bass cannot be made perfect simply because there is no space for effective bass treatments.

For smaller rooms, you can treat for incremental changes but it will never be perfect. Move the sub in every possible position until it sounds best. Tune and move on.

Perfectly described my room. Now, bass is better but not perfect. I can open the door to make it a bigger room. The hallway acts like a bass trap. Init lang ng panahon sobra kaya i need to use the AC when I watch. I'll need to sacrifice temp over good bass.

[JojoD818]

So the room is like a huge baffle box and the door serves as the port. Close the door and you have a sealed box, open the door and you have one huge bass-reflex box. The hallway may even serve as a bass horn.

[Lancito]

So the room is like a huge baffle box and the door serves as the port. Close the door and you have a sealed box, open the door and you have one huge bass-reflex box. The hallway may even serve as a bass horn.

You are correct.  I closed the door and moved my subs around.  Also moved my listening position 2 feet closer to the back wall.  I'll run a sine wave sweep and plot the readings.

[marty_e]

A guy once told me to place the sub where you sit and crawl around the room for the best bass response and then swap places. That's the starting point

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[Lancito]

For many many years enjoying this hobby, I still learn on how to set up my system properly. Position, position, position. Either the subs or listening area. Read it almost always but never applied to myself. Rearranged my subwoofers and now it sounds like a whole new system.

Thanks to all who helped and made recommendations.

[yygoob]

anong naging final layout ng sub nyo sir?

[Lancito]

anong naging final layout ng sub nyo sir?

Same which is 1/4th of front wall pero inatras ko ng mga 8 inches.  dinikit ko sa wall.  Lumabas yung bass sa MLP ko.  Grabe konting urong lang ang laki ng difference.  Kakasira ulo hobby na ito.

[yygoob]

I also have the same observation before mas ok ang tunog ng sub pag nakabukas ang door or  pag nasa labas ako ng room....guess its the size of the room....napagod na ako sa kakatulak ng sub to different positions.... even used a room eq software and mic...ended with both subs at the middle side of the room....mukhang room ang dapat palitan he he he

[Gino]

Low bass have very long length waves. It sounds better far. That is why it improves outside the room. It is the same reason why boom cars sound solid outside the car and at a distance. That is why there is an ideal room siz for very good sound. It must have space for meaningful sound treatment.

[comet]

sir Lance nagreduce ka rin ba ng absorbers for the bass or di na?


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[Lancito]

sir Lance nagreduce ka rin ba ng absorbers for the bass or di na?


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Hindi sir. We cannot have too much bass traps.

The Auralex I'm selling sobra sa binili ko. Wala na pagkakabitan.

[comet]

ok sir


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[too jazzy cool]

in my experience.. very limited . try the subs at the side wall.