I haven't been able to get through to Macky888's website for the last couple of days...(where out thou Macky888?)
Macky recommends using 30 litres with 1 passive with 400g Mmp. Unibox shows this as 104db@24Hz (passive exceeds xmax below this).
32 litre enclosure with 600g passive = 102db@24Hz, but this design will extend to 20.5Hz@101.5db before reaching xmax.
32 litre enclosure with 230g passive = 107.5db@30Hz (passive exceeds xmax below this).
Above are all at max input (300W). What should be considered as more important: a couple of db at 25-30Hz, or the ability to strech a few further Hz? I like the idea of hitting 20Hz within excursion limits, but I don't have experience as to whether it should be traded off for the higher SPL a few Hz up. Is 5db increase a lot at 30Hz and worth sacrificing the stretch to 20Hz?
I will rarely be hitting it with 300W, but opinions on these design choices are important regardless.
Macky recommends using 30 litres with 1 passive with 400g Mmp. Unibox shows this as 104db@24Hz (passive exceeds xmax below this).
32 litre enclosure with 600g passive = 102db@24Hz, but this design will extend to 20.5Hz@101.5db before reaching xmax.
32 litre enclosure with 230g passive = 107.5db@30Hz (passive exceeds xmax below this).
Above are all at max input (300W). What should be considered as more important: a couple of db at 25-30Hz, or the ability to strech a few further Hz? I like the idea of hitting 20Hz within excursion limits, but I don't have experience as to whether it should be traded off for the higher SPL a few Hz up. Is 5db increase a lot at 30Hz and worth sacrificing the stretch to 20Hz?
I will rarely be hitting it with 300W, but opinions on these design choices are important regardless.
how about using the room response calculator at the FRD consortium site? this seemed to be pretty accurate when I used it for my room.
- Robert
- Robert
>room........generic transfer function.........
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Doesn't exist beyond the theoretical +12dB/octave below the 1st room mode of the longest dim, so if your room is 24ft long, then it begins at ~565/24 = ~23.4Hz, ramping up to +12dB/(23.4/2) = 11.7Hz, etc.. Construction losses, etc., normally limits this to 3-4dB in the rooms I've measured, though I did an underground basement that did the max until the access door started audibly flapping.
Most of your gain will come from putting it near/at a wall/floor or corner boundary. Again though, construction plays a big part in how much gain there is. A mid wall/floor position nets you up to +3dB and a corner up to +6dB referenced to 1/2 space. Again though, with few exceptions, the stick built room's I've measured only gained 3-4dB in the corners and 1-2dB up against a wall, but then I live in a fairly temporate climate, so I imagine the better built homes of the northern lattitudes will have a bit more gain.
This makes calculating a room gain curve a non-trivial pursuit since you have to sum it based on the speaker's position in the room, as well as how high up from the floor it is. I rely on Lspcad for an approximation when I'm interested enough to spend the time.
Mostly I just either design a max flat alignment and lower Fb as required, or for sub duty, it's always a low tuned EBS unless a sealed is specifically requested, in which case I go for as big a cab as will be tolerated to keep its roll off room friendly.
FWIW, in my room there's no gain above ~12.5Hz due to the ~open floorplan, and with the speakers in the only 'real' corners, a pair of EBS cabs tuned to 16Hz combined with a ~40Hz F3 yields a ~flat in-room response to 16Hz.
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>Also, even with room gain, is 101 dB really enough at 20 Hz?
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Depends on the app.. If you look at a human hearing loudness curve you'll see that ~101dB/20Hz has an equal amplitude of only ~60dB in our acute hearing BW, which is about how loud the background noise in an office is, so while it might be 'loud' enough to rattle the pictures, etc., it won't be audible due to the rest of the BW's amplitude masking it, even if they are only at TV listening levels.
DD/DTS reference specs 115dB/listening position, so it falls well short of this, but WRT music, unless you listen to pipe organ, the 1812 Overture, LF special effects CDs, or want to match the dynamic range of front row center at a large symphonic concert, it's plenty loud.
GM
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Doesn't exist beyond the theoretical +12dB/octave below the 1st room mode of the longest dim, so if your room is 24ft long, then it begins at ~565/24 = ~23.4Hz, ramping up to +12dB/(23.4/2) = 11.7Hz, etc.. Construction losses, etc., normally limits this to 3-4dB in the rooms I've measured, though I did an underground basement that did the max until the access door started audibly flapping.
Most of your gain will come from putting it near/at a wall/floor or corner boundary. Again though, construction plays a big part in how much gain there is. A mid wall/floor position nets you up to +3dB and a corner up to +6dB referenced to 1/2 space. Again though, with few exceptions, the stick built room's I've measured only gained 3-4dB in the corners and 1-2dB up against a wall, but then I live in a fairly temporate climate, so I imagine the better built homes of the northern lattitudes will have a bit more gain.
This makes calculating a room gain curve a non-trivial pursuit since you have to sum it based on the speaker's position in the room, as well as how high up from the floor it is. I rely on Lspcad for an approximation when I'm interested enough to spend the time.
Mostly I just either design a max flat alignment and lower Fb as required, or for sub duty, it's always a low tuned EBS unless a sealed is specifically requested, in which case I go for as big a cab as will be tolerated to keep its roll off room friendly.
FWIW, in my room there's no gain above ~12.5Hz due to the ~open floorplan, and with the speakers in the only 'real' corners, a pair of EBS cabs tuned to 16Hz combined with a ~40Hz F3 yields a ~flat in-room response to 16Hz.
====
>Also, even with room gain, is 101 dB really enough at 20 Hz?
====
Depends on the app.. If you look at a human hearing loudness curve you'll see that ~101dB/20Hz has an equal amplitude of only ~60dB in our acute hearing BW, which is about how loud the background noise in an office is, so while it might be 'loud' enough to rattle the pictures, etc., it won't be audible due to the rest of the BW's amplitude masking it, even if they are only at TV listening levels.
DD/DTS reference specs 115dB/listening position, so it falls well short of this, but WRT music, unless you listen to pipe organ, the 1812 Overture, LF special effects CDs, or want to match the dynamic range of front row center at a large symphonic concert, it's plenty loud.
GM
jewilson said:
It's called Visual Ears. I am co-author of it. I'm not sure if it's OK to suggest that you check it out because it's a commercial product but it's on my web site. I don't want to be accused of trying to hawk my software. But there is a limited FREE demo that you can learn a lot from.
Im using a peerless 850146 in a 100L 24hz box and in my fairly bassy room it doesnt provide enough punch, its clear, deep, undistorted, but its not special in anyway, i am supposed to be getting 105db without room gain and it doesnt sound very loud IMO. i am upgrading very soon as it has been quite disappointing.
Im not sure what i am trying to get at, maybe that 25hz 105db isnt that loud and thundering as it sounds.
Im not sure what i am trying to get at, maybe that 25hz 105db isnt that loud and thundering as it sounds.
Something doesn't match up here. So you're saying 12db is theoretical maximum, but in reality it is down to ~3db. So 3db up at 11.7Hz, 6db at 5.89Hz...It seems to start really low. Do I sum the results for the other dimensions too?
I can't see where you got the figure 565? Doesn't appear to be speed of sound?
In regards to SPL, it's only a 10" so it will give what it will give. I'm more interested in whether you would rather trade few db SPL at 30Hz for extension down to 20Hz at max output.
I think you hit the nail on the head. It's a single 10" you are dealing with here, although one which puts out the equivalent of two 10 inchers air-moved wise. Once upon a time, when a woofer had an excursion ±.25 inch it would be energetically labelled "super long throw" by it's manufacturer!
I remember when a friend and myself converted a large closet in his living room to a large subwoofer chamber. Forty-five cubic feet internal volume. We braced it as best we could, which wasn't great, and bought four Thump 15 inch subs which supposedly had an Fs of 18 and an SPL of 96 dB@ 1M/1W.
Thump subs are just cheap car subs and of course they didn't come close to matching the stated Thiele-Small specs. They had an irregular response, but we crossed it over at 50 Hz so we didn't much care. We hooked them up with an old Phase Linear 300 Watt amp that he bought used. We tuned the enclosure by using four 4" diameter ports which tuned the closet to 16 Hz.
Incidentally, despite the makeshift "enclosure", at resonance the port and the woofer shared equal output-yes, I adjusted the port reading, a lá Keele, for the fact that the port has a smaller diameter than the 15 inch diaphragm, therefore the SPL reading of the port will be higher.
We tested with a home made test generator and an SPL meter he got for free from AR years before. Whatever, the test tone generator was accurate. At 16 Hz you could hear some, but once you got up to 20 Hz it really, really roared. Bass sounded like it came from The Center Of The Earth.
But that was four 15 inchers in a closet.
When I see members here talk about taking a single one or two cubic foot sub down into the twenties, I have to chuckle a little bit. You aren't going to get any usable output down there with that setup. If you can get good, solid output down to 30 Hz with less than 2 cubic feet of total enclosure space, you have done a great job.
I think people sometimes forget how deep 30 Hz is.
My suggestion is-go for the 30 Hz tuning. You will be delighted you did.
I remember when a friend and myself converted a large closet in his living room to a large subwoofer chamber. Forty-five cubic feet internal volume. We braced it as best we could, which wasn't great, and bought four Thump 15 inch subs which supposedly had an Fs of 18 and an SPL of 96 dB@ 1M/1W.
Thump subs are just cheap car subs and of course they didn't come close to matching the stated Thiele-Small specs. They had an irregular response, but we crossed it over at 50 Hz so we didn't much care. We hooked them up with an old Phase Linear 300 Watt amp that he bought used. We tuned the enclosure by using four 4" diameter ports which tuned the closet to 16 Hz.
Incidentally, despite the makeshift "enclosure", at resonance the port and the woofer shared equal output-yes, I adjusted the port reading, a lá Keele, for the fact that the port has a smaller diameter than the 15 inch diaphragm, therefore the SPL reading of the port will be higher.
We tested with a home made test generator and an SPL meter he got for free from AR years before. Whatever, the test tone generator was accurate. At 16 Hz you could hear some, but once you got up to 20 Hz it really, really roared. Bass sounded like it came from The Center Of The Earth.
But that was four 15 inchers in a closet.
When I see members here talk about taking a single one or two cubic foot sub down into the twenties, I have to chuckle a little bit. You aren't going to get any usable output down there with that setup. If you can get good, solid output down to 30 Hz with less than 2 cubic feet of total enclosure space, you have done a great job.
I think people sometimes forget how deep 30 Hz is.
My suggestion is-go for the 30 Hz tuning. You will be delighted you did.
>Something doesn't match up here. So you're saying 12db is theoretical maximum, but in reality it is down to ~3db. So 3db up at 11.7Hz, 6db at 5.89Hz...It seems to start really low. Do I sum the results for the other dimensions too?
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Of course it doesn't! Theory assumes a perfectly rigid/sealed space, so unless you live in a bomb shelter or similarly constructed abode, then there's going to be losses and they will increase with decreasing frequency in a smallish room. Again though, unless you listen to stuff with serious LF output, this is moot.
No, above the first mode, boundary gain is your friend.
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>I can't see where you got the figure 565? Doesn't appear to be speed of sound?
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Eigenmodes (standing waves) develop at c/2L, or you can say (c/2)/L where c = ~1130ft/sec., ergo ~565/L.
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>In regards to SPL, it's only a 10" so it will give what it will give. I'm more interested in whether you would rather trade few db SPL at 30Hz for extension down to 20Hz at max output.
====
One more time, unless you listen to stuff with serious LF output, 40Hz-up, and especially 60Hz-up is where you want plenty of efficiency to keep distortion vanishingly low, with the 250-500Hz BW requiring the most.
That said, since the low note on a concert grand piano is 27.5Hz and 30Hz on an electric organ combined with the nature of their fundamental to harmonics amplitudes, I recommend tuning a sub around at least 27.5Hz, with an alignment that yields an in-room response to at least a 30Hz F3 to preserve their tonal balance.
GM
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Of course it doesn't! Theory assumes a perfectly rigid/sealed space, so unless you live in a bomb shelter or similarly constructed abode, then there's going to be losses and they will increase with decreasing frequency in a smallish room. Again though, unless you listen to stuff with serious LF output, this is moot.
No, above the first mode, boundary gain is your friend.
====
>I can't see where you got the figure 565? Doesn't appear to be speed of sound?
====
Eigenmodes (standing waves) develop at c/2L, or you can say (c/2)/L where c = ~1130ft/sec., ergo ~565/L.
====
>In regards to SPL, it's only a 10" so it will give what it will give. I'm more interested in whether you would rather trade few db SPL at 30Hz for extension down to 20Hz at max output.
====
One more time, unless you listen to stuff with serious LF output, 40Hz-up, and especially 60Hz-up is where you want plenty of efficiency to keep distortion vanishingly low, with the 250-500Hz BW requiring the most.
That said, since the low note on a concert grand piano is 27.5Hz and 30Hz on an electric organ combined with the nature of their fundamental to harmonics amplitudes, I recommend tuning a sub around at least 27.5Hz, with an alignment that yields an in-room response to at least a 30Hz F3 to preserve their tonal balance.
GM
27.5 Hz is only 1/8 of an octave below 30 Hz. That translates into only 1.5 dB lower in the bass region if you tune to 27.5 Hz instead of 30 Hz, plus you cover the lowest fundamental on the concert piano. So tune to 27.5 Hz.
As far as the inespensive BK 10P passive radiator, I Emailed BK electronics. The reply I received is posted here:
http://www.diyaudio.com/forums/showthread.php?postid=347271#post347271
So, it is up to you if you want to try it.
As far as the inespensive BK 10P passive radiator, I Emailed BK electronics. The reply I received is posted here:
http://www.diyaudio.com/forums/showthread.php?postid=347271#post347271
So, it is up to you if you want to try it.
Cabin gain important mainly in small rooms
Ignoring room gain that occurs above the lowest frequency standing wave (whose effects are going to be overwhelmed by the effects of the standing waves on bass frequency response
anyway):
The theoretical cabin gain is 12dB/octave below the lowest frequency room mode (565/length in feet for a rectangular room
= center frequency of lowest frequency room mode.
In general: cabin gain makes it likely that a decent subwoofer or speaker with port tuning in the 20-25Hz. range will overpressurize a small room at 20Hz. -- a sealed enclosure with roll-off under 30Hz. is likely to work better in a small (under 200 square feet) room ... and even then you may prefer leaving the door open so the room doesn't overpressurize at 20Hz..
Other than that statement above, the quantity and audible effect of cabin gain is hard to predict unless a room is unusually well sealed.
The theoretical cabin gain will be reduced by bass energy losses
(leaks) through open doors, doorways, windows = any pressurization leaks.
A cinder block room with a well sealed door canl pressurize at 12dB/octave.
A 1/2" plasterboard room with one leaky door will not.
This is difficult to measure at home -- I've tried comparing in-room response with subwoofer ground plane measurements in my driveway ... and all I accomplished was breaking my hand-truck hauling my subwoofer outside.
A further complication is that hearing/feeling ability at 20Hz. varies from person-to-person and also varies at different SPL's.
6dB of cabin gain at 20Hz. might be great news for someone who listens at modest volume where 20Hz. is difficult to "hear".
At high volumes where our ears have a flatter frequency response, an extra 6dB at 20Hz. could overpressurize the room and partially mask the other frequencies of music.
Below the lowest frequency room mode, the room acts as a "pressure pot" and all speaker locations will pressurize the room equally -- speaker position and listener position is not a factor, as one poster wrote.
Ignoring room gain that occurs above the lowest frequency standing wave (whose effects are going to be overwhelmed by the effects of the standing waves on bass frequency response
anyway):
The theoretical cabin gain is 12dB/octave below the lowest frequency room mode (565/length in feet for a rectangular room
= center frequency of lowest frequency room mode.
In general: cabin gain makes it likely that a decent subwoofer or speaker with port tuning in the 20-25Hz. range will overpressurize a small room at 20Hz. -- a sealed enclosure with roll-off under 30Hz. is likely to work better in a small (under 200 square feet) room ... and even then you may prefer leaving the door open so the room doesn't overpressurize at 20Hz..
Other than that statement above, the quantity and audible effect of cabin gain is hard to predict unless a room is unusually well sealed.
The theoretical cabin gain will be reduced by bass energy losses
(leaks) through open doors, doorways, windows = any pressurization leaks.
A cinder block room with a well sealed door canl pressurize at 12dB/octave.
A 1/2" plasterboard room with one leaky door will not.
This is difficult to measure at home -- I've tried comparing in-room response with subwoofer ground plane measurements in my driveway ... and all I accomplished was breaking my hand-truck hauling my subwoofer outside.
A further complication is that hearing/feeling ability at 20Hz. varies from person-to-person and also varies at different SPL's.
6dB of cabin gain at 20Hz. might be great news for someone who listens at modest volume where 20Hz. is difficult to "hear".
At high volumes where our ears have a flatter frequency response, an extra 6dB at 20Hz. could overpressurize the room and partially mask the other frequencies of music.
Below the lowest frequency room mode, the room acts as a "pressure pot" and all speaker locations will pressurize the room equally -- speaker position and listener position is not a factor, as one poster wrote.
In this post there is a link to site that shows a normalised room gain response over six different rooms with varying speaker placement. That graph (the last one) may be a good generic approximation for room gain.
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