Hi there.
I'm building a subwoofer cabinet for the Ground Zero GZHW 30XSPL-D2.
This is really bugging me now- I'm looking at the recommended port sizing as follows, from the user manual:
Bassreflex / vented 90 Liter netto / 3.18 cu.ft. net
Recommended enclosure Port (dimensions) 40 x 250 mm / 1.57 x 9.84”
Portlänge / port length 257 mm / 10.11” F3 (-3 dB) 25 Hz
This gives a 100cm2 port area for a 90 litre cabinet. This seems to me to be very small! All the built cabinets I can find have port areas of 150+cm2.
Can this recommendation possibly be a good one? I'd rather trust the recommendation if it's credible, but really scratching my head about it.
Hornresp shows a peak particle velocity of 2.8m/s @1 watt. And 125m/s at program wattage.
Thanks!
I'm building a subwoofer cabinet for the Ground Zero GZHW 30XSPL-D2.
This is really bugging me now- I'm looking at the recommended port sizing as follows, from the user manual:
Bassreflex / vented 90 Liter netto / 3.18 cu.ft. net
Recommended enclosure Port (dimensions) 40 x 250 mm / 1.57 x 9.84”
Portlänge / port length 257 mm / 10.11” F3 (-3 dB) 25 Hz
This gives a 100cm2 port area for a 90 litre cabinet. This seems to me to be very small! All the built cabinets I can find have port areas of 150+cm2.
Can this recommendation possibly be a good one? I'd rather trust the recommendation if it's credible, but really scratching my head about it.
Hornresp shows a peak particle velocity of 2.8m/s @1 watt. And 125m/s at program wattage.
Thanks!
Last edited:
Greets!
I assume this driver is for a mobile audio app, so the vent is designed to 'choke' the driver when over powered; if so, you're good to go, but if for HIFI/HT apps then the pioneers made it really simple by making the vent area (Av) = driver piston area (Sd) and if too big, then use a passive radiator (PR) and with today's high power, best to use at least one on two opposing sides.
Another option is to calculate the low vent mach size no matter how big an (Av) is required and either make an 'el pipe-o' or folded variant.
I assume this driver is for a mobile audio app, so the vent is designed to 'choke' the driver when over powered; if so, you're good to go, but if for HIFI/HT apps then the pioneers made it really simple by making the vent area (Av) = driver piston area (Sd) and if too big, then use a passive radiator (PR) and with today's high power, best to use at least one on two opposing sides.
Another option is to calculate the low vent mach size no matter how big an (Av) is required and either make an 'el pipe-o' or folded variant.
Ok thanks. Yes, it's car audio.
I suppose it's highly unlikely that the manufacturer would make bad recommendations, but it was rather unnerving to see the how small the area looked when I drew it out.
Is this choking to prevent over-excursion?
I feel like I'm going to add a bit of area just in case, because I don't want extreme chuffing.
I suppose it's highly unlikely that the manufacturer would make bad recommendations, but it was rather unnerving to see the how small the area looked when I drew it out.
Is this choking to prevent over-excursion?
I feel like I'm going to add a bit of area just in case, because I don't want extreme chuffing.
Wow , german engineered china sub. 45mm (total) Xmax is like a dayton ultramax 12. same 75mm coil , 400/800W , not 3K !
Dayton with just 20mm Xmax (40 total) wants 176cm/sq. ... a full 6" pipe. 100cm-4.5" pipe - would "chuff" away.
Dayton with just 20mm Xmax (40 total) wants 176cm/sq. ... a full 6" pipe. 100cm-4.5" pipe - would "chuff" away.
Yeah, that’s what I’m concerned about. I’m aiming to build a subwoofer rather than a steam engine.
Then use PRs or some form of TL per above or inverse tapered like I did being an excellent choice SQ wise, though can't imagine such a 'beast' having much, ergo recommend limiting BW to ~ its 42.4*2/0.6 = < ~141 Hz Fhm and 42.4*0.6/2 = > ~13 Hz Flm.
I have the low profile dayton LS12-44 , and just a 4" pipe (80CM/Sq) which is fully flared. At just 20mm total Xmax , I just start
to hear port noise with a test tone. un-noticable with music. I did build the 'beast' Dayton tuned to 20Hz , 6" pipe with an elbow - 22" total.
Tiny bit of port noise right at Xmax (50mm total). man, a LOT of air ... blew my hair across the room !!
to hear port noise with a test tone. un-noticable with music. I did build the 'beast' Dayton tuned to 20Hz , 6" pipe with an elbow - 22" total.
Tiny bit of port noise right at Xmax (50mm total). man, a LOT of air ... blew my hair across the room !!
I guess ground zero must know what they're talking about.. I'll just enlarge it a bit to have some 'safety factor' and flare it.
I know TLs are not particularly hard to build, but I want to KISS in order to make the woodworking as easy as possible.
thanks again
I know TLs are not particularly hard to build, but I want to KISS in order to make the woodworking as easy as possible.
thanks again