Great article for us audiophiles

[glassjaw7]

http://www.ethanwiner.com/believe.html
(sorry if this has been posted before)

 

[stephen sawall]

Interesting concept. I always though it was part of the typical illusion most people live.

 

[glassjaw7]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

 

[moltenmetalburn]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

use the directivity modifers, these are the ones:

http://jay-mitchell.com/dirmod.html

foam source:

http://www.mcmaster.com/#85735k72/=3w3766

these things are amazing and based on good science, I love them for beamy cabs.

 

[stephen sawall]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

use the directivity modifers, these are the ones:

http://jay-mitchell.com/dirmod.html

foam source:

http://www.mcmaster.com/#85735k72/=3w3766

these things are amazing and based on good science, I love them for beamy cabs.

+1 .... they work better than anything else I have tried.

 

[glassjaw7]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

use the directivity modifers, these are the ones:

http://jay-mitchell.com/dirmod.html

foam source:

http://www.mcmaster.com/#85735k72/=3w3766

these things are amazing and based on good science, I love them for beamy cabs.

Isn't this guy (Jay) on RT?
I read his whole explanation on why this works better than 'blockers' and I don't really understand it. This part right off the bat confused me:
"1. High frequencies come from the center of a cone speaker, and that's why they beam.

False. If you could actually get the high frequencies to be radiated exclusively by the "center" of the speaker - say the dust cap - you'd find them being radiated over a greater angle, not a smaller one."

Ok, so if high frequencies do not come from the center of the speaker, why then when moving a mic from the outer edge of the speaker cone to the center, does the sound get much brighter?

So with these 'doughnuts' you're supposed to do the opposite of beam blockers/tone bras and cover the outer cone, but leave the center of the speaker open?

I may buy a set of this foam and a set of tone bras to compare. The part about the blockers causing the tone to reflect, and then re-reflect on the cone, causing phasing issues and 'comb-filtering' made sense to me at least. I just don't see how 'absorbing' the sound from the outer cone will help. Seems like it would make it worse.

 

[stephen sawall]

Just try it and see if it works or not for you ? That's what I did. All my closed back cabs now have them.

 

[moltenmetalburn]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

use the directivity modifers, these are the ones:

http://jay-mitchell.com/dirmod.html

foam source:

http://www.mcmaster.com/#85735k72/=3w3766

these things are amazing and based on good science, I love them for beamy cabs.

Isn't this guy (Jay) on RT?
I read his whole explanation on why this works better than 'blockers' and I don't really understand it. This part right off the bat confused me:
"1. High frequencies come from the center of a cone speaker, and that's why they beam.

False. If you could actually get the high frequencies to be radiated exclusively by the "center" of the speaker - say the dust cap - you'd find them being radiated over a greater angle, not a smaller one."

Ok, so if high frequencies do not come from the center of the speaker, why then when moving a mic from the outer edge of the speaker cone to the center, does the sound get much brighter?

So with these 'doughnuts' you're supposed to do the opposite of beam blockers/tone bras and cover the outer cone, but leave the center of the speaker open?

I may buy a set of this foam and a set of tone bras to compare. The part about the blockers causing the tone to reflect, and then re-reflect on the cone, causing phasing issues and 'comb-filtering' made sense to me at least. I just don't see how 'absorbing' the sound from the outer cone will help. Seems like it would make it worse.

Did you read the principles of operation section? it explains how it all works.

Principles of Operation

In order to understand why/how it works, you have to understand a bit of the geometry and acoustics in a cone transducer. The cone is driven very near its center (where the voice coil former is attached to the cone). The mechanical excitation (the vibration of the cone) is not instantaneous. It moves outward in the cone with its own characteristic velocity, which is geater than the velocity of sound in air. As the excitation moves outward, the air in contact with the segment of the cone that is moving is also excited, and sound is radiated from that segment of the cone. If the angle of the cone is "just right" for the properties of the cone material, the sound that is radiated from each section will be almost perfectly in time with the sound that was radiated earlier, from a portion of the cone that is set further back.

When all this sound adds up (at distances of a few or more) out in front of the cone, you get a coherent wavefront to a relatively high frequency (as high as ~5kHz), but only on axis. At off-axis positions, the synchronization of arrival times falls apart very rapidly, to the extent that a typical guitar speaker will see its output above 1200 Hz fall off by as much as 15-20dB within just a few degrees off axis. The effects on directivity due to mis-synchronized off-axis arrivals are much less at lower frequencies, because the wavelengths of sound are larger than the cone, and the speaker is therefore not "beamy" at these frequencies.

Placing the absorber doughnut in front of the cone has almost no effect below 1kHz, because the material is too thin to have a significant effect at those frequencies. This is good, since, as we've seen above, the speaker's behavior below 1kHz is not a problem. At higher frequencies, the radiation from the outer portions of the cone is progressively absorbed, whereas the portion of the radiation from the center of the cone which moves straight forward is allowed to pass through the opening in the doughnut unattenuated. The result is that there is a net reduction in high-frequency content on axis, but the high frequencies that do get through are now radiated by a virtual source - the opening in the doughnut - which is much smaller than the actual speaker, and they are therefore radiated over a greater angle. The speaker's directivity is now essentially the same over the entire range of interest for electric guitar, and you're out a few bucks for a piece of foam and a few minutes to cut out and attach the doughnut.

as for the micing question he doesnt say that highs dont come from the center he says they dont come from the center exclusively, meaning that the rest of the cone of the speaker is also creating highs. highs that do not reach the ear at the same time as the highs from the center.

realize when listening to a speaker in a room you are hearing its full amount of sound projection. when you are close micing the cab you are only allowing a tiny section of the cone to be heard, the exact size of the mic diaphragm which is obviously much smaller than the entire speaker. remember these are meant to help the sound the entire speaker radiates into the entire room to be less directional.

jay is an engineer that owns his own loudspeaker company. this science is his life. Im sure if you look for contact info on the web he will answer your questions in more detail. if he truly is an RT member find his profile and pm him.

also as for the doughnut "absorbing" sound from the outer cone, Im pretty sure its actually delaying rather than absorbing.

try em! for a 4x12 its a little over 20 bux, def worth it.

 

[glassjaw7]

Interesting concept. I always though it was part of the typical illusion most people live.

Same here. Looks like there is some actual measurable proof that our biased ears are only part of the equation. I found that article while searching for different types of 'tone bra's' and 'beam blockers'.

use the directivity modifers, these are the ones:

http://jay-mitchell.com/dirmod.html

foam source:

http://www.mcmaster.com/#85735k72/=3w3766

these things are amazing and based on good science, I love them for beamy cabs.

Isn't this guy (Jay) on RT?
I read his whole explanation on why this works better than 'blockers' and I don't really understand it. This part right off the bat confused me:
"1. High frequencies come from the center of a cone speaker, and that's why they beam.

False. If you could actually get the high frequencies to be radiated exclusively by the "center" of the speaker - say the dust cap - you'd find them being radiated over a greater angle, not a smaller one."

Ok, so if high frequencies do not come from the center of the speaker, why then when moving a mic from the outer edge of the speaker cone to the center, does the sound get much brighter?

So with these 'doughnuts' you're supposed to do the opposite of beam blockers/tone bras and cover the outer cone, but leave the center of the speaker open?

I may buy a set of this foam and a set of tone bras to compare. The part about the blockers causing the tone to reflect, and then re-reflect on the cone, causing phasing issues and 'comb-filtering' made sense to me at least. I just don't see how 'absorbing' the sound from the outer cone will help. Seems like it would make it worse.

Did you read the principles of operation section? it explains how it all works.

Principles of Operation

In order to understand why/how it works, you have to understand a bit of the geometry and acoustics in a cone transducer. The cone is driven very near its center (where the voice coil former is attached to the cone). The mechanical excitation (the vibration of the cone) is not instantaneous. It moves outward in the cone with its own characteristic velocity, which is geater than the velocity of sound in air. As the excitation moves outward, the air in contact with the segment of the cone that is moving is also excited, and sound is radiated from that segment of the cone. If the angle of the cone is "just right" for the properties of the cone material, the sound that is radiated from each section will be almost perfectly in time with the sound that was radiated earlier, from a portion of the cone that is set further back.

When all this sound adds up (at distances of a few or more) out in front of the cone, you get a coherent wavefront to a relatively high frequency (as high as ~5kHz), but only on axis. At off-axis positions, the synchronization of arrival times falls apart very rapidly, to the extent that a typical guitar speaker will see its output above 1200 Hz fall off by as much as 15-20dB within just a few degrees off axis. The effects on directivity due to mis-synchronized off-axis arrivals are much less at lower frequencies, because the wavelengths of sound are larger than the cone, and the speaker is therefore not "beamy" at these frequencies.

Placing the absorber doughnut in front of the cone has almost no effect below 1kHz, because the material is too thin to have a significant effect at those frequencies. This is good, since, as we've seen above, the speaker's behavior below 1kHz is not a problem. At higher frequencies, the radiation from the outer portions of the cone is progressively absorbed, whereas the portion of the radiation from the center of the cone which moves straight forward is allowed to pass through the opening in the doughnut unattenuated. The result is that there is a net reduction in high-frequency content on axis, but the high frequencies that do get through are now radiated by a virtual source - the opening in the doughnut - which is much smaller than the actual speaker, and they are therefore radiated over a greater angle. The speaker's directivity is now essentially the same over the entire range of interest for electric guitar, and you're out a few bucks for a piece of foam and a few minutes to cut out and attach the doughnut.

as for the micing question he doesnt say that highs dont come from the center he says they dont come from the center exclusively, meaning that the rest of the cone of the speaker is also creating highs. highs that do not reach the ear at the same time as the highs from the center.

realize when listening to a speaker in a room you are hearing its full amount of sound projection. when you are close micing the cab you are only allowing a tiny section of the cone to be heard, the exact size of the mic diaphragm which is obviously much smaller than the entire speaker. remember these are meant to help the sound the entire speaker radiates into the entire room to be less directional.

jay is an engineer that owns his own loudspeaker company. this science is his life. Im sure if you look for contact info on the web he will answer your questions in more detail. if he truly is an RT member find his profile and pm him.

also as for the doughnut "absorbing" sound from the outer cone, Im pretty sure its actually delaying rather than absorbing.

try em! for a 4x12 its a little over 20 bux, def worth it.

Cool. Thanks for explaining a little more. I read it, but maybe didn't pay enough attention to certain parts of the article. I will try them and see how I like the effect! Oh, and I wasn't doubting Jay's knowledge on the subject as I can tell just from reading this that he knows his stuff! Thanks guys. -Jordan