Hi GM,
Thanks for your input and figures.
I put your revised Fs, Qes etc figures into winISD and also get 4.7 litres, so that looks good.
For the vent, I'm thinking of lowering the Xover to the sub to around 80hz, as the sub is not situated between the speakers. It's to the side of the room and am worried about directionality at 120 hz.
If I tuned it to 80hz to start off with and then later decided to add some helper woofers to the lower part of the enclosure, could I then simply adjust the length of the existing vent to give a cut off at 120Hz? Or would it mean more drastic changes?
I take it that I wouldn't be adding a high pass crossover circuit to the driver, just letting the driver and box do that?
Sorry if that's a dumb question - I'm still learning
Cheers,
Martin
Thanks for your input and figures.
I put your revised Fs, Qes etc figures into winISD and also get 4.7 litres, so that looks good.
For the vent, I'm thinking of lowering the Xover to the sub to around 80hz, as the sub is not situated between the speakers. It's to the side of the room and am worried about directionality at 120 hz.
If I tuned it to 80hz to start off with and then later decided to add some helper woofers to the lower part of the enclosure, could I then simply adjust the length of the existing vent to give a cut off at 120Hz? Or would it mean more drastic changes?
I take it that I wouldn't be adding a high pass crossover circuit to the driver, just letting the driver and box do that?
Sorry if that's a dumb question - I'm still learning
Cheers,
Martin
Greets!
Yeah, I ran out of time, so was going to come back WRT sub integration. Ideally we need a < ~1/3 WL distance of the XO's -12 dB point, though due to room interaction down low and our falling hearing acuity, 1 WL is usually sufficient if the sub is either along the sound wall at some odd harmonic spacing or very near the listening position [LP].
Factor in that so much music seems to be mixed for mobile audio and consumer DD or DTS multi-channel play back nowadays that an 80 Hz/2nd or 4th order XO point/slope should theoretically be used and preferably lower if < 20 Hz playback is desired since most ‘sub’ drivers are only good for ~two octaves of ~flat BW.
The traditional rule is to have at least an octave of 'flat' BW on each side of the XO point for every 12 dB of slope order, so when mating to a vented alignment with its inherent 4th order roll-off, this becomes problematic unless either a very steep slope order is used and/or there's lots of room gain to offset the lack of speaker efficiency down low.
Historically, an extended bass shelf [EBS] alignment was used for woofer alignments to either ~blend with room gain or for mating to a sub system, but virtually all single drivers [FR] don't have sufficient acoustic efficiency down low to use it except in near-field [<1 m] apps.
With the advent of relatively inexpensive digital bass controllers though, just lower the 4.7 L cab’s Fb to 40 Hz. Of course this doesn’t factor in the room, so merely a cab alignment starting point and without knowing the Pensil’s net Vb, I’m inclined to adhere to my ‘BIB’ philosophy to allow some tuning flexibility, so recommend just tuning them to 40 Hz and use a digital controller along with maybe some additional vent damping to make them blend in room until if/when you decide to either replace or partition them off to add woofer systems.
Ditto for if you want to try higher XO point/slope.
GM
Yeah, I ran out of time, so was going to come back WRT sub integration. Ideally we need a < ~1/3 WL distance of the XO's -12 dB point, though due to room interaction down low and our falling hearing acuity, 1 WL is usually sufficient if the sub is either along the sound wall at some odd harmonic spacing or very near the listening position [LP].
Factor in that so much music seems to be mixed for mobile audio and consumer DD or DTS multi-channel play back nowadays that an 80 Hz/2nd or 4th order XO point/slope should theoretically be used and preferably lower if < 20 Hz playback is desired since most ‘sub’ drivers are only good for ~two octaves of ~flat BW.
The traditional rule is to have at least an octave of 'flat' BW on each side of the XO point for every 12 dB of slope order, so when mating to a vented alignment with its inherent 4th order roll-off, this becomes problematic unless either a very steep slope order is used and/or there's lots of room gain to offset the lack of speaker efficiency down low.
Historically, an extended bass shelf [EBS] alignment was used for woofer alignments to either ~blend with room gain or for mating to a sub system, but virtually all single drivers [FR] don't have sufficient acoustic efficiency down low to use it except in near-field [<1 m] apps.
With the advent of relatively inexpensive digital bass controllers though, just lower the 4.7 L cab’s Fb to 40 Hz. Of course this doesn’t factor in the room, so merely a cab alignment starting point and without knowing the Pensil’s net Vb, I’m inclined to adhere to my ‘BIB’ philosophy to allow some tuning flexibility, so recommend just tuning them to 40 Hz and use a digital controller along with maybe some additional vent damping to make them blend in room until if/when you decide to either replace or partition them off to add woofer systems.
Ditto for if you want to try higher XO point
GM
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