I have an odd shaped room. think of a big square with rectangles cut out of 2 opposite corners. 39.5 square metres, 105 cubic metres (3700 cu ft), Longest diagonal is 10.4 metres. Tiled concrete floor, three very large windows, interior walls are plaster, exterior walls are brick 2.5 walls are external.
Mainly for music, quality over quantity. The Rythmik 15 is looks great but is really pushing the budget. I have a 300W/8 ohm 450W/4 ohm commercial amp for the sub. one channel is fried but I can fix it if needed for 800W/8 ohm bridged.
I have only 2 options for placement:
Inside an ornamental chest near the centre of the room, 5 cubic feet, downward firing. 1x15 or 2x 12 inch drivers.
Under the couch, down firing, box must be under 10 inches total height but up to 6 feet by 20 inches, a BIG couch. Either a couple of large drivers or an array of smaller cheap drivers in a honeycomb pattern. A big sonosub in the corner is out of the question.
Is relatively even response down to 20Hz acheivable in this room?
where is the best place for the sub? at one end of the big diagonal or near the centre of the room?
Mainly for music, quality over quantity. The Rythmik 15 is looks great but is really pushing the budget. I have a 300W/8 ohm 450W/4 ohm commercial amp for the sub. one channel is fried but I can fix it if needed for 800W/8 ohm bridged.
I have only 2 options for placement:
Inside an ornamental chest near the centre of the room, 5 cubic feet, downward firing. 1x15 or 2x 12 inch drivers.
Under the couch, down firing, box must be under 10 inches total height but up to 6 feet by 20 inches, a BIG couch. Either a couple of large drivers or an array of smaller cheap drivers in a honeycomb pattern. A big sonosub in the corner is out of the question.
Is relatively even response down to 20Hz acheivable in this room?
where is the best place for the sub? at one end of the big diagonal or near the centre of the room?
i dont have much idea about 
wat u saying, but i think 20Hz is too low freq to be acheivable in a room, plus i dont think mp3 audio n all does not have much below 30hz.
woofer placement is i think better at diagonal end, (yahama audio sysem manual i read 1ce suggests that woofer be placed 1-2 feet behind and 1-2 feet to the centre of the right speaker)
i think even better placement would be in the centre of the space left between 2 rectangles that is removed, that way ur woofer would be an a small room connected to a bigger room(if its not science fiction .. then it might act like a horn n give you some extra dB SPL gain) 😀
as i said cant help, ur setup is like pro audio i guess...lol
best of luck
wat u saying, but i think 20Hz is too low freq to be acheivable in a room, plus i dont think mp3 audio n all does not have much below 30hz.woofer placement is i think better at diagonal end, (yahama audio sysem manual i read 1ce suggests that woofer be placed 1-2 feet behind and 1-2 feet to the centre of the right speaker)
i think even better placement would be in the centre of the space left between 2 rectangles that is removed, that way ur woofer would be an a small room connected to a bigger room(if its not science fiction .. then it might act like a horn n give you some extra dB SPL gain) 😀
as i said cant help, ur setup is like pro audio i guess...lol
best of luck
I don't know how it is in this case, but there is a common misconception that a wavelength has to "fit" insida a room in order to make audible sound. That the largest room dimension should be at least a half or whatever portion of a wavelength.
This is not the case.
One can divide the frequency range in three parts:
"high" frequencies; those above the Schröder frequency (which typicaly is ~200 Hz). In this frequency range the sound field is reverberant, and there is little use in studying individual room responances since they are so many and close together.
"mid" frequencies below the Schröder frequency and above the lowest resonance of the room. For box shaped rooms, this resonance occurs when the longest dimension of the room* is half a wavelength. In this range, room resonances are often troublesome and cause an uneven frequency response. Some frequencies are emphasised and others are attenuated.
"low" frequencies, below the "mid" range. If the loudspeaker has a flat response down to DC in free space (which of course is very hypothetical), the response in an airtight room will increase by 12 dB/octave towards lower frequencies.
So, contrary to the common belief that low frequencies are hard to generate in a room, it is actually the other way around. Low frequencies are typically amplified inside a room compared to free space. The "mid" range is problematic, however, for hifi sound reproduction due to the unevenness that occurs.
*not the diagonal, but the wall-to-wall distance. For a room of 6x4x2.5 metres, this is 6 metres, and the frequency is 345/12=29 Hz.
This is not the case.
One can divide the frequency range in three parts:
"high" frequencies; those above the Schröder frequency (which typicaly is ~200 Hz). In this frequency range the sound field is reverberant, and there is little use in studying individual room responances since they are so many and close together.
"mid" frequencies below the Schröder frequency and above the lowest resonance of the room. For box shaped rooms, this resonance occurs when the longest dimension of the room* is half a wavelength. In this range, room resonances are often troublesome and cause an uneven frequency response. Some frequencies are emphasised and others are attenuated.
"low" frequencies, below the "mid" range. If the loudspeaker has a flat response down to DC in free space (which of course is very hypothetical), the response in an airtight room will increase by 12 dB/octave towards lower frequencies.
So, contrary to the common belief that low frequencies are hard to generate in a room, it is actually the other way around. Low frequencies are typically amplified inside a room compared to free space. The "mid" range is problematic, however, for hifi sound reproduction due to the unevenness that occurs.
*not the diagonal, but the wall-to-wall distance. For a room of 6x4x2.5 metres, this is 6 metres, and the frequency is 345/12=29 Hz.
Thanks guys,
Amit, no not pro audio, I'm an electronics tech so I understand things buy nuimbers, big gains can be had from minor things if I can understand where things matter. It's all a learning experience for me. You are right about the frequency content of music, Most music's bass is concentrated about 70Hz but I'd like to be able to see what "Angel" By massive attack should really sound like, I can see the bassline has most of it's energy around 32Hz.
After posting the original message I discovered the collaborative tapped horn project. That looks like it might fit under my couch if I lay over the driver partition inside the box at an angle instead of parallel to the front and back walls. This allows a slightly larger diameter driver in a flatter box. I am currently reading through the huge thread.
I haven't understood enough yet to determine if the two JBL 10 inch drivers I already have are suitable. So far I know a lot of the design depends on the right driver, a high moving mass helps, low Xmax is not a problem.
I need to measure the cross section under the couch to see if a folded tapped horn can fit or if I'm limited to 6 feet long for the box. 30Hz for a couple of sheets of ply and parts that are laying about the house would be a great acheivement.
Svante: Thankyou for taking the time to share your knowledge.
The room is mainly box shaped.
the longest flat wall to flat wall distance in the room is 7.5 metres so my troublesome "Mid" resonance is about 23Hz. one of those walls is where the sub will be placed.
Amit, no not pro audio, I'm an electronics tech so I understand things buy nuimbers, big gains can be had from minor things if I can understand where things matter. It's all a learning experience for me. You are right about the frequency content of music, Most music's bass is concentrated about 70Hz but I'd like to be able to see what "Angel" By massive attack should really sound like, I can see the bassline has most of it's energy around 32Hz.
After posting the original message I discovered the collaborative tapped horn project. That looks like it might fit under my couch if I lay over the driver partition inside the box at an angle instead of parallel to the front and back walls. This allows a slightly larger diameter driver in a flatter box. I am currently reading through the huge thread.
I haven't understood enough yet to determine if the two JBL 10 inch drivers I already have are suitable. So far I know a lot of the design depends on the right driver, a high moving mass helps, low Xmax is not a problem.
I need to measure the cross section under the couch to see if a folded tapped horn can fit or if I'm limited to 6 feet long for the box. 30Hz for a couple of sheets of ply and parts that are laying about the house would be a great acheivement.
Svante: Thankyou for taking the time to share your knowledge.
The room is mainly box shaped.
the longest flat wall to flat wall distance in the room is 7.5 metres so my troublesome "Mid" resonance is about 23Hz. one of those walls is where the sub will be placed.
...this might be also interesting for you:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1289574#post1289574
http://www.diyaudio.com/forums/showthread.php?s=&postid=1289574#post1289574
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