Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

Jump to Latest
#6,182
the logic would be :



-100% sealed (that doesn't exist) : compliance of air works as a spring; variability is the temperature (which is more or less constant in a modern home around 22%)


- vented or foam and not sealed dust caps: volume of air pushed and filled will be only the volume moved by the cone outside the port. These are the resonances in the port, the group delay and the resonance bo that are heard.


I mean, air is not pushed like water on a wave, sound is a vibration transmited across air mollecules like a wave ??????? main factor are air density (temperature), humidity and reflexions, vibrations of materials at resonance frequencies ?😕



Is this correct ? 😕
 
#6,183
I wouldn't be interested in sprinkling beryllium powder into a ported subwoofer, and sitting nearfield for an audition of the latest basswars album....Safety first gentlemen. Vibration is a swell catalyst for dislodging particulates that can become airborne inside the enclosure. Between displacement, diffusion, and convection, yes there will be air current/exchange, though it may be a small amount, a small issue over 10 years of exposure might have consequences... I have children, I am smart, to have pondered the issue. I'll try to address it practically.

Looks like mineral wool wins my affection...cheapest price per damping coeficient/sqft on the net for those not wanting to use polyfil but rather, a more density consistent product.
Insulation Wool 0 to 1200 Degrees F
 
#6,186
GM said:
FWIW/FYI: https://www.ranger5g.com/forum/attachments/box-builder-fill-er-up-pdf.35156/

GM
Click to expand...

I read the article and it states several points consistent with what is relayed on audio forums for many years. "fool the woofer into thinking its in a larger box". same box- "the one with stuffing should kick out lower bass"

I see something different when I measure and simulate. For a particular woofer, stuffing lowers the Q but does not fool the woofer into thinking its in a larger box in terms of low frequency extension, only the Q matches the the larger box. The low frequency extension in the larger box is lost in the smaller box..🙁

Hmmm, ??? what am I missing?
 
#6,188
Joel Wesseling said:
I read the article and it states several points consistent with what is relayed on audio forums for many years. "fool the woofer into thinking its in a larger box". same box- "the one with stuffing should kick out lower bass"

I see something different when I measure and simulate. For a particular woofer, stuffing lowers the Q but does not fool the woofer into thinking its in a larger box in terms of low frequency extension, only the Q matches the the larger box. The low frequency extension in the larger box is lost in the smaller box..🙁

Hmmm, ??? what am I missing?
Click to expand...

It's a little more complicated than that. Stuffing a box absolutely makes the box look larger, the resonance will fall (although this is not a huge effect.) Although over-stuffing can have the reverse effect because a dense damping material takes up more internal space than it creates. So packing density matters.

Also you will see a reduction in Q, but how much depends on the woofer. If Qe is dominate then damping will not have as much effect than a woofer with a higher Qe.

But "low frequency extension" is different than these other factors because it depends on your definition of "extension." Lower Q reduces the output over a range of frequencies around resonance, but it raise them below this region. So where you define "extension" matters.

There is no singular answer.
 
#6,189
Of the various Q's

The driver tested below is an Eminence Omega Pro-15a

As except as listed below*, the enclosure is of my design. A 2.8 cubic foot aperiodic.

Left side column raw/free air. Right side column in enclosure
Re ..5.8........ ................................5.8
Fs 33.5 .....................................Fc ..52.89
Qts .340 ...................................Qtc .. 0.6131
Qes 0.3586 Qes 0.7348
Qms 6.69 ....................................Qms 3.702

Fs 33.5 ......................................Fc 52.89 (2.8 APR enclosure)
Fc 57.6 *Empty 3.6 cubic foot box empty test enclosure*
 
#6,195
Lol! To be taken with a grain of salt.

That video shows what the average person could do...but doesn't....I've made my own hepa flow hood before...putting a hepa filter in front of a box fan will in fact screen the air no less than any other air scrubber claiming hepa that you might buy at walmart.

Does anyone know off hand what size radius is on the Summas? My driver baffle for the 15" is ~1.5" in depth and the wal's are 3/4"....whats the biggest radius I should use? I planned on purchasing a 1" radius tool for the router.
 
#6,198
gedlee said:
It's a little more complicated than that. Stuffing a box absolutely makes the box look larger, the resonance will fall (although this is not a huge effect.) Although over-stuffing can have the reverse effect because a dense damping material takes up more internal space than it creates. So packing density matters.

Also you will see a reduction in Q, but how much depends on the woofer. If Qe is dominate then damping will not have as much effect than a woofer with a higher Qe.

But "low frequency extension" is different than these other factors because it depends on your definition of "extension." Lower Q reduces the output over a range of frequencies around resonance, but it raise them below this region. So where you define "extension" matters.

There is no singular answer.
Click to expand...

How low does Qe have to be, to be considered, "dominant" ?
 
#6,200
In the cited example from the previous page, this is indeed the case. It has just recently become of interest to me, measuring the various Q's once a driver is installed in an enclosure.

I studied these results, and once I thought t all the way through, it makes sense. The Qms is reduced because of the *control* of an enclosure. All other Q's increase in value. I've only done one such test for one driver, so I am curious as to the results of others, to come in the near future.


The driver tested below is an Eminence Omega Pro-15a

As except as listed below*, the enclosure is of my design. A 2.8 cubic foot aperiodic.

Left side column raw/free air. Right side column in enclosure
Re ..5.8........ ................................5.8
Fs 33.5 .....................................Fc ..52.89
Qts .340 ...................................Qtc .. 0.6131
Qes 0.3586............................... Qes 0.7348
Qms 6.69 ....................................Qms 3.702

Fs 33.5 ......................................Fc 52.89 (2.8 APR enclosure)
Fc 57.6 *Empty 3.6 cubic foot box empty test enclosure.
 
You must log in or register to reply here.
Top Bottom