Glass wool, but the kind that btends to be itchy. I tried the techniwue once then switched to other techniques, and if i did similar agin i would use cotton insilation (UltraTouch)
dave
I was going to say that as well. Slowly, slowly, we are seeing many toxins removed from use. But we do need to deal with what is already in the system,
dave
Regarding the claims Mike has read that resistive loading "extends bass response", I will refer to the type of aperiodic loading known as the "distributed port" enclosure. Note that this is is a repeat of information I have proffered in past discussions on aperiodic loading.
A distributed port enclosure is more akin to a sealed enclosure than a reflex enclosure, and reduces the amplitude of the Q of its single bass resonance hump. The low frequency cut-off of a well designed DP enclosure is not as low as a reflex enclosure, but is better than a sealed box of the same volume, while its transient behaviour is said to be appreciably better than both, especially the reflex.
And, additionally, for the experimenters out there:
Steve Hutton, writing for Hi-Fi News, supplied an empirical formula for calculating the total area of the small holes in a distributed port enclosure.
A = 5.5 x V [0.818 (Fs/25) + 0.182]
Where A is the total area in sq in, V is the enclosure volume in cu ft and Fs is the resonant frequency, in Hz, of the driver in free air.
Given that 5 holes of 0.5" diameter have an equivalent area of 1 sq inch, the total area, A, can be made up of rows of the appropriate number of 0.5" diameter holes. The holes should be spaced 0.75" apart, measured from centre to centre.The distributed port would then be lined with woolen cloth, such as that used to make overcoats, in order to increase the acoustic resistance.
A distributed port enclosure is more akin to a sealed enclosure than a reflex enclosure, and reduces the amplitude of the Q of its single bass resonance hump. The low frequency cut-off of a well designed DP enclosure is not as low as a reflex enclosure, but is better than a sealed box of the same volume, while its transient behaviour is said to be appreciably better than both, especially the reflex.
And, additionally, for the experimenters out there:
Steve Hutton, writing for Hi-Fi News, supplied an empirical formula for calculating the total area of the small holes in a distributed port enclosure.
A = 5.5 x V [0.818 (Fs/25) + 0.182]
Where A is the total area in sq in, V is the enclosure volume in cu ft and Fs is the resonant frequency, in Hz, of the driver in free air.
Given that 5 holes of 0.5" diameter have an equivalent area of 1 sq inch, the total area, A, can be made up of rows of the appropriate number of 0.5" diameter holes. The holes should be spaced 0.75" apart, measured from centre to centre.The distributed port would then be lined with woolen cloth, such as that used to make overcoats, in order to increase the acoustic resistance.
Without all the variables being know we can only guess.
In the case of woofer in too small a box, the response nse often starts out humped, aperidicityh can flatten that out and "pusn the hump” down with a bit od bass extention. But it is a careful balance. Randomly adding aperiodicity to a random box gives random results,
dave
The December 1974 Hi-Fi News article, which included Steve Hutton's empirical formula given above, has this to say about the Q and resonant frequency:
"As the distributed port area increases from zero, the Q and resonant frequency fall. However, after the Q has reached unity it starts to rise again with the figures becoming multi-valued, hence unpredictable, below Q = 1."
"As the distributed port area increases from zero, the Q and resonant frequency fall. However, after the Q has reached unity it starts to rise again with the figures becoming multi-valued, hence unpredictable, below Q = 1."