Frank
Thanks for your apology, and in the interests of goodwill I offer a personal apology if I offended you.
As was stated, keeping track of everything posted on this board is difficult for us mods, especially as there are only three of us monitoring the situation, as Zardoz and Multiplexor mostly stay in video, Jason is busy at work, and AudioFreak currently spends most of his time coding stuff behind the scenes.
So, I would ask you all to help, if you see something wrong, don't be afraid to us the report button, that will get our attention directed to the right place to hopefully calm things down, or take action as required. You could also contact any of us privately if you feel better that way.
Anyway, Bob, where are you? I am looking forward to continuing our debate .
Thanks for your apology, and in the interests of goodwill I offer a personal apology if I offended you.
As was stated, keeping track of everything posted on this board is difficult for us mods, especially as there are only three of us monitoring the situation, as Zardoz and Multiplexor mostly stay in video, Jason is busy at work, and AudioFreak currently spends most of his time coding stuff behind the scenes.
So, I would ask you all to help, if you see something wrong, don't be afraid to us the report button, that will get our attention directed to the right place to hopefully calm things down, or take action as required. You could also contact any of us privately if you feel better that way.
Anyway, Bob, where are you? I am looking forward to continuing our debate
.
Hi Pinkmouse,
I have just tried to add to my last post but the edit is being refused as I have apparently exceeded the limit of characters.
What I tried to say, is that my last post was written early this afternoon, but when I came to despatch it, I couldn't get any access to the Forum for some reason.
I don't know why, did you have a problem at your end perhaps, but after trying for over 20 mins, I simply gave up!
Accordingly, I hadn't seen *any* of this afternoon's comments, from post # 273 ,several of which seem to relate to, or cross with my message.
This evening I have just looked at an article in the latest AudioXpress which turned up from the States this morning.
It relates to producing sounds in small rooms, and I'm a little uncertain as to the conclusions, as it is quite involved.
It's too late to finish reading and understanding it all this evening, but I will post the essence of it tomorrow, all being well.
In any event, for anyone who is genuinely interested in the matter, it would be worth looking out the article for themselves.
Regards,
I have just tried to add to my last post but the edit is being refused as I have apparently exceeded the limit of characters.
What I tried to say, is that my last post was written early this afternoon, but when I came to despatch it, I couldn't get any access to the Forum for some reason.
I don't know why, did you have a problem at your end perhaps, but after trying for over 20 mins, I simply gave up!
Accordingly, I hadn't seen *any* of this afternoon's comments, from post # 273 ,several of which seem to relate to, or cross with my message.
This evening I have just looked at an article in the latest AudioXpress which turned up from the States this morning.
It relates to producing sounds in small rooms, and I'm a little uncertain as to the conclusions, as it is quite involved.
It's too late to finish reading and understanding it all this evening, but I will post the essence of it tomorrow, all being well.
In any event, for anyone who is genuinely interested in the matter, it would be worth looking out the article for themselves.
Regards,
Tip.
Hi Bob,
A similar problem was experienced by me and quite likely other members...I had to get in through the back door :
http://www.diyvideo.com.
I'm sure the problem wasn't a local one but rather one or more servers had been brought to their knees affecting us Europeans.
It only lasted for a good 15 minutes though, after that all was as usual.
Cheers,
Hi Bob,
A similar problem was experienced by me and quite likely other members...I had to get in through the back door :
http://www.diyvideo.com.
I'm sure the problem wasn't a local one but rather one or more servers had been brought to their knees affecting us Europeans.
It only lasted for a good 15 minutes though, after that all was as usual.
Cheers,
Bobken said:
Basically, using as a test bed a very accurate Bruel & Kjaer test kit, that it is very possible to produce "bass in a small room".
I read this with sceptism since i have held for some time that you could not reproduce a waveform in a space smaller than that waveform.
I was not surprised thou, as i had seen this "myth" attacked before.
dave
Quit fighting
Some of the recent posts in this thread have pushed the boundary of even the broadly lenient latitudes we have been giving of late. I have swept a large number of inflamatory posts into Texas.
I invite anyone who's post is missing to defend it if they wish -- with so many, and it being past my bedtime i am sure there were some innocent victims.
I have also given a short cooling off period to those i felt fanned the flames. You can read all about that in the SinBin thread.
dave/planet10
(in official capacity)
Some of the recent posts in this thread have pushed the boundary of even the broadly lenient latitudes we have been giving of late. I have swept a large number of inflamatory posts into Texas.
I invite anyone who's post is missing to defend it if they wish -- with so many, and it being past my bedtime i am sure there were some innocent victims.
I have also given a short cooling off period to those i felt fanned the flames. You can read all about that in the SinBin thread.
dave/planet10
(in official capacity)
Re: Quit fighting
Yes, I noticed some posts had gone missing... One day, the count was over 280, next time I looked it was down to about 265....
planet10 said:
Some of the recent posts in this thread have pushed the boundary of even the broadly lenient latitudes we have been giving of late. I have swept a large number of inflamatory posts into Texas.
I invite anyone who's post is missing to defend it if they wish -- with so many, and it being past my bedtime i am sure there were some innocent victims.
I have also given a short cooling off period to those i felt fanned the flames. You can read all about that in the SinBin thread.
dave/planet10
(in official capacity)
Yes, I noticed some posts had gone missing... One day, the count was over 280, next time I looked it was down to about 265....
If anyone wants to test this theory, just take a normal woofer, place it in a sealed box where the compliance of the air is relatively large compared to the compliance of the woofer (just for argument's sake), and mount a microphone inside the box, and run a standard MLS sweep.
That way you'll have an infinite-baffle woofer (with respect to the inside of the box) firing into what amounts to a very small "room" inside the box.
You'll find that even though the largest dimension of the "room" may be 12 inches, that there will be a very large amount of bass output below the frequency corresponding to this wavelength - just like any good modeling program such as LSPCad or SoundEasy will predict.
You will of course get the requisite standing waves and comb filtering as constructive/deconstructive interference occurs at varying multiples of the dimensions of the box - this is to be expected and happens (and can be predicted easily, and measured) in all rooms, large or small.
LSPCad models this behaviour quite accurately, and in order to see how much easier it is to get large quantities of low bass in a small room, you can just play around with the room transfer curve generator in the demo version offered by Adire audio
http://www.adireaudio.com/miscellaneous/software.htm
It's easy to see that reducing the room size increases the amount of low bass, not the other way around.
Of course, that's just a simulation, and may or may not have any bearing on reality - it's up to the reader to run the tests him/herself to satisfy their curiosity.
Also, the fact that headphones fire into a "room" where the largest wavelength would support only a 7khz wave and yet can easily produce 40hz, 30hz, and even 20hz bass with remarkable accuracy isn't a result of exciting the inner-ear directly, but simply to do with the fact that smaller "rooms" augment the low bass, as opposed to hindering it.
Most headphones have a driver with a free-air resonant frequency of 100hz or above -- some as high as 400hz. My sennheiser HD600's have an Fs of 100hz, yet produce excellent bass down to 20hz. The small "room" in which the sennheiser's driver fires into, along with its open rear chamber for infinite baffle loading of the driver, contribute to its excellent low bass performance.
Measurements for the HD600 using a microphone mounted to a dummy head where the ear would be, thereby eliminating any psychoacoustic affects attributed to exciting the ear "directly" can be had here:
http://www.headphone.com/layout.php?topicID=3&subTopicID=26&productID=0020080600
It may be difficult for some to accept this, as it goes against what our intuition might tell us about the way sound waves propagate, but it is the truth.
Simple subjective analysis of bass performance in different rooms can be quite difficult - in many cases a larger room can have a better "perceived" low bass than a smaller one, usually due to different standing wave frequencies in the larger room. Smaller rooms usually have higher Q peaks and dips in the frequency response due to standing waves than larger ones, and depending on where they are in frequency, they might be more or less objectionable. This isn't a property necessarily inherent to small rooms, though. With proper diffusers/absorbers, it's possible to have a small room with little to no standing wave excitation and absolutely phenomenal bass down to 5hz, with a properly tuned system.
For those who have a formal understanding of physics, explore Art Ludwig's page at :
http://www.silcom.com/~aludwig/
It delves into a relatively rigorous and mathematical explanation of how and why this works, although you have to connect a few of the dots yourself.
Particularly, check out:
http://www.silcom.com/~aludwig/Physics/Main/Cavity_modes.html
http://www.silcom.com/~aludwig/Room_acoustics.html
And beyond all, simply perform one of the tests I describe above, trust your measurements, and smile and nod. Unless you're using it incorrectly, a well-calibrated measuring setup tends not to lie.
That way you'll have an infinite-baffle woofer (with respect to the inside of the box) firing into what amounts to a very small "room" inside the box.
You'll find that even though the largest dimension of the "room" may be 12 inches, that there will be a very large amount of bass output below the frequency corresponding to this wavelength - just like any good modeling program such as LSPCad or SoundEasy will predict.
You will of course get the requisite standing waves and comb filtering as constructive/deconstructive interference occurs at varying multiples of the dimensions of the box - this is to be expected and happens (and can be predicted easily, and measured) in all rooms, large or small.
LSPCad models this behaviour quite accurately, and in order to see how much easier it is to get large quantities of low bass in a small room, you can just play around with the room transfer curve generator in the demo version offered by Adire audio
http://www.adireaudio.com/miscellaneous/software.htm
It's easy to see that reducing the room size increases the amount of low bass, not the other way around.
Of course, that's just a simulation, and may or may not have any bearing on reality - it's up to the reader to run the tests him/herself to satisfy their curiosity.
Also, the fact that headphones fire into a "room" where the largest wavelength would support only a 7khz wave and yet can easily produce 40hz, 30hz, and even 20hz bass with remarkable accuracy isn't a result of exciting the inner-ear directly, but simply to do with the fact that smaller "rooms" augment the low bass, as opposed to hindering it.
Most headphones have a driver with a free-air resonant frequency of 100hz or above -- some as high as 400hz. My sennheiser HD600's have an Fs of 100hz, yet produce excellent bass down to 20hz. The small "room" in which the sennheiser's driver fires into, along with its open rear chamber for infinite baffle loading of the driver, contribute to its excellent low bass performance.
Measurements for the HD600 using a microphone mounted to a dummy head where the ear would be, thereby eliminating any psychoacoustic affects attributed to exciting the ear "directly" can be had here:
http://www.headphone.com/layout.php?topicID=3&subTopicID=26&productID=0020080600
It may be difficult for some to accept this, as it goes against what our intuition might tell us about the way sound waves propagate, but it is the truth.
Simple subjective analysis of bass performance in different rooms can be quite difficult - in many cases a larger room can have a better "perceived" low bass than a smaller one, usually due to different standing wave frequencies in the larger room. Smaller rooms usually have higher Q peaks and dips in the frequency response due to standing waves than larger ones, and depending on where they are in frequency, they might be more or less objectionable. This isn't a property necessarily inherent to small rooms, though. With proper diffusers/absorbers, it's possible to have a small room with little to no standing wave excitation and absolutely phenomenal bass down to 5hz, with a properly tuned system.
For those who have a formal understanding of physics, explore Art Ludwig's page at :
http://www.silcom.com/~aludwig/
It delves into a relatively rigorous and mathematical explanation of how and why this works, although you have to connect a few of the dots yourself.
Particularly, check out:
http://www.silcom.com/~aludwig/Physics/Main/Cavity_modes.html
http://www.silcom.com/~aludwig/Room_acoustics.html
And beyond all, simply perform one of the tests I describe above, trust your measurements, and smile and nod. Unless you're using it incorrectly, a well-calibrated measuring setup tends not to lie.
For the moment at least...
"The First and the Last, the Alpha and the Omega".
http://www.diyaudio.com/forums/showthread.php?postid=122502#post122502
"The First and the Last, the Alpha and the Omega".
http://www.diyaudio.com/forums/showthread.php?postid=122502#post122502
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