Damping The vented box

[Aucosticraft]

I might very well have an effect at 160Hz, but typically subs are crossed over at 80Hz or below where standing waves are too long to be a problem.

Yes, I very much agree with you. also frequencies 80Hz and below show no direction compared to 120Hz.

On the LFE channel there is no information above 120hz. During recording there is a "brickwall" filter at 120.

“In the Dolby Digital encoding process, the encoder will brickwall filter the LFE signal at 120 Hz. To properly hear the LFE content, a sixth or seventh order 120-Hz low-pass filter must be included in the monitor chain"

Yes, I agree to this too. 160Hz was because JBL did it. The philosophy was, if the Harman kardon AVR137 receiver is tweaking (re-processing) with other channels to get rest of frequencies and adding it to LFE. more over if the playback is as Dolby standards then too there won't be any information missing.

FYI, the lowpass LFE filter is 3rd order 18 dB/octave. If crossed over at 80hz, 5db down at 110hz, ~7db down at 115hz, brickwall at 120hz.

Thanks for passing a good piece of information. but is this how its typically done ?

Well, not really recommends. That stuff is more like the SPEC of the LFE channel, not a playback recommendation. The playback recommendation came from research at THX (IIRC) that showed 80 Hz was "undetectable." Of course some skimpier systems cross over higher than that in order to use ultra teeny satellites.

However, feel free to cross over your subs at 3 Hz if you like. Tom Danley will be glad to build you something for that application.

3Hz not possible with the current one.

You said it right. Satellite speakers which are much smaller needs much higher cross over. And so is mine. my satellite crossovers at 100Hz @ -6 db
size constrain do not allow me to get frequencies low enough.
Rather I can say , its is playing the role of woofer and subwoofer.

As I mentioned above,I have AVR 137 mfg. HarmanKardon, Can some one please provide me what are the crossovers implemented by the receiver during each setting of speakers.

like when I select

1) mode

LFE - Yes (SUB)
Front -Small
Center-Small
Rear- Small

2)
LFE- YES (SUB).
Front - Large
Center- Large-
Rear -Large

3)
LFE- YES (SUB).
Front - Large
Center- small
Rear -small

etc.... different combinations. No information about crossover is given in owner manual.

 

[AllenB]

absorbent material has virtually no effect on Low frequencies.

It is possible, but sometimes easier to figure the dimensions of the box against the intended upper crossover point.

About 160Hz.

This is not unreasonable in a typical room, IMO, despite reputed localisation effects.