One of the reasons Linkwitz didnt like the sound of boxed full range speakers was because of the delayed sound coming through the cone and giving coloration to the sound .
In the lxmini he used a 80 cm long pipe heavily stuffed with damping material at the bottom of the pipe , and with damping material all the way up to the driver . This avoided the reflected sound coming from the pipe and through the cone with about -40 dB .
I wonder how big this problem is with a more normal loudspeaker . If I got a 6,5 inch driver put in a rectangular box of 15 liters, with some light damping material inside , how much of the delayed and out of phase sound from the inside of the box will find its way through the cone, thus coloring the sound?
Is it in the magnitude of -20 dB below the direct sound from the driver , or is it less ?
Can it be heard ?
Is there any investigations done at this subject?
About dB and distortion levels :
benchmarkmedia.com
Linkwitz investigations :
”When a speaker driver is mounted in a box it radiates as much energy into the space in front of the cone as it does into the much smaller space behind the cone. What happens to the air borne energy inside? At long wavelengths it is common practice to store it in resonant structures to extend the steady-state low frequency response of the speaker. In general, the energy leads to very high sound pressures inside the box. A small amount of the energy is lost as heat in the stuffing material, some in the process of flexing the cabinet walls. Much of it reappears outside the box, because the thin cone presents a weak sound barrier. Just how much is difficult to measure, but it is a contributor to the frequency response. I am of the opinion that the effect is most notable in the low hundreds of Hz region, where stuffing materials are ineffective and the internal dimensions not small enough for the internal air volume to act as a pure compliance. Consequently, enclosures should be either very small (less than 1/16th of a wavelength) or extremely large, both of which are not very practical for different reasons. ”
In the lxmini he used a 80 cm long pipe heavily stuffed with damping material at the bottom of the pipe , and with damping material all the way up to the driver . This avoided the reflected sound coming from the pipe and through the cone with about -40 dB .
I wonder how big this problem is with a more normal loudspeaker . If I got a 6,5 inch driver put in a rectangular box of 15 liters, with some light damping material inside , how much of the delayed and out of phase sound from the inside of the box will find its way through the cone, thus coloring the sound?
Is it in the magnitude of -20 dB below the direct sound from the driver , or is it less ?
Can it be heard ?
Is there any investigations done at this subject?
About dB and distortion levels :
Interpreting THD Measurements - Think dB not Percent!
Distortion measurements (THD, THD+N and IMD) are traditionally expressed in terms of percent. But what do 1%, 0.1%, 0.01% or 0.001% mean in terms of loudness or audibility? If you are like most people you just know that 0.001% is the best of the three numbers listed above. If you are a...

Linkwitz investigations :
”When a speaker driver is mounted in a box it radiates as much energy into the space in front of the cone as it does into the much smaller space behind the cone. What happens to the air borne energy inside? At long wavelengths it is common practice to store it in resonant structures to extend the steady-state low frequency response of the speaker. In general, the energy leads to very high sound pressures inside the box. A small amount of the energy is lost as heat in the stuffing material, some in the process of flexing the cabinet walls. Much of it reappears outside the box, because the thin cone presents a weak sound barrier. Just how much is difficult to measure, but it is a contributor to the frequency response. I am of the opinion that the effect is most notable in the low hundreds of Hz region, where stuffing materials are ineffective and the internal dimensions not small enough for the internal air volume to act as a pure compliance. Consequently, enclosures should be either very small (less than 1/16th of a wavelength) or extremely large, both of which are not very practical for different reasons. ”
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