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Discussion Starter · #1 ·
i'm planning a pair of tempest x's when they become available again in march...


would two 4 inch ports PER woofer be sufficient?


i'm planning on tuning them to 18hz or so, at about 11 cubes each sub/box...


just wanted to make sure i wasn't sufficating them or anything...they'll have 1.25 inch flares on each end...


i know two 4 inchers are usually good enough for car audio tuned to low to mid 30's but wasn't sure if it was different for HT/home music...


thanks

2 lee
 

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The answer depends on how much power you're feeding them. With an 18Hz tune, you'd probably need to keep the input power fairly low by some standards. I have two 3" ports and don't get chuffing with my Tempest-X with actual program material, but only because my box is tuned to 12Hz and I only have about 400w on tap - if I played at reference. I do not, so my power needs are even less than that.


Since you have a pair of Tempest-X, you're splitting the power between them, unless you want to run them hot compared to the mains (many people do), so that somewhat reduces the power for each, assuming they are placed to constructively combine their output.


Most, including DIY Cable, suggest a minimum of a 6" vent for the Tempest-X, the equivalent of four 3" vents.
 

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It's much easier to get the port volume you need to avoid chuffing by using a slot port... and usually cheaper (no ports to buy, just MDF).
 

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Discussion Starter · #4 ·
thanks for the inputs guys...


i'll be using the ep2500 at 4 ohms stereo so each one should get around 750rms...


if going the 4 inch port versions, they'd be pvc so it'll be plenty cheap...


Aaron, wow your sub is tuned low...i could try going to 15 or so, but i don't know if i'll be able to go that low...anyways, seems like your (2) 3 inchers are doing fine so i'm assuming my dual 4's should be ok too...
 

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Given 750 watts as max and 11cuft tuned to 18Hz, port air speed for 2 4" ports will breach 26 meters per second at 23 hz and max out below tune at 46 meters per second. I don't see a substantial problem with port chuffing as you'll probobly won't be a full load very often. A single 6" will perform better in regards to port air speed and can be done even cheaper than PVC with sonotube and a simple router and roundover bit at the port exit and entry, assuming the inlet of the port is mounted in a brace as it probobly should be in either case.


Good luck with the build and either way, i'm sure they'll sound fantastic.


Of course the 14hz tune would be even better with a single 6" port if you can fit a 30" long port in the box but at 11cuft, i bet you can.


PS...Don't forget the subsonic/high pass for below tune.
 

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one thing you might do is take a look at what size ports are used in commercial designs.


epik subwoofers seem to have arrived at 6" port for one 15" long throw driver.


the svs pb13u, which is a very long throw 13" driver uses three 3.5" ports.


elemental designs uses a 6" port for their 15" implementation.


quad 4" have a cross sectional area of 324 cm^2

dual 6" have a cross sectional area of 365 cm^2

(three 3.5" come in at 186 cm^2, which might be a little small)


so, you are in the right ballpark. using a single 6" per driver would be more in keeping with some of the proven commercial designs.


with your design, you should be able to hit 115db full reference with about 300 watts and have 8.5m/s air velocity with quad 4" ports. you shouldn't have any chuffing problems at that level.
 

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Quote:
Originally Posted by LTD02 /forum/post/15580786


one thing you might do is take a look at what size ports are used in commercial designs.


epik subwoofers seem to have arrived at 6" port for one 15" long throw driver.


the svs pb13u, which is a very long throw 13" driver uses three 3.5" ports.


elemental designs uses a 6" port for their 15" implementation.


quad 4" have a cross sectional area of 324 cm^2

dual 6" have a cross sectional area of 365 cm^2

(three 3.5" come in at 186 cm^2, which might be a little small)


so, you are in the right ballpark. using a single 6" per driver would be more in keeping with some of the proven commercial designs.


with your design, you should be able to hit 115db full reference with about 300 watts and have 8.5m/s air velocity with quad 4" ports. you shouldn't have any chuffing problems at that level.

The only problem is at an 18Hz tune the ports would need to be 34" long. At 14hz tune, they'd be 57". Kinda hard to fit in an 11cuft box not to mention port resonance and compression.
 

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Quote:
Originally Posted by mayhem13 /forum/post/15583476


The only problem is at an 18Hz tune the ports would need to be 34" long. At 14hz tune, they'd be 57". Kinda hard to fit in an 11cuft box not to mention port resonance and compression.

Which is why you see a lot more designs using slotted ports these days...
 

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Discussion Starter · #10 ·
wow thanks for hte killer replies guys...i'll def re-read these posts when i'm ready to fire...again, thanks a bunch!


qq - mayhem, i just got my ep2500 and haven't had time reading it yet...anyways, does anyone know if the ep2500 have a subsonic filter built in? if not, how'd i got about getting one?


i'm a vet with car audio and know their mono amps usually come with subsonic filters built in...i'm a HT newb though...


would tuning it to 18hz be good enough for HT/home music use? i mean a good compramise? i can understand people like tuning their ht subs to 14ish for those movies but i know that you loose output in the 20's and 30's hz for music...correct?
 

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No the Amp has no filters. You'd need some kind of control/eQ system. An Elemental Designs eQ.2 will do the trick with the added benefit of peQ.


Personally, i like the TempestX in a sealed enclosure of about 5cuft with eQ. No subsonic required here. Two of these would be monsterous!!!
 

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Discussion Starter · #12 ·
ok thanks...i also ordered the DSP1124P...it already came in this past weekend...


again, i've been quite busy and haven't gotten to reading all the materials on the ep2500 or the DSP1124P...i plan to get a ton of that done this spring break and to get everything running by late spring, early summer...


thanks for all your help everyone...


edit - i noticed that the DSP1124P doesn't have a subsonic filter, i'm guessing i could use the DSP and the eD eQ together if I went ported? and like you said, skip the eD eQ if just going sealed...


again, sorry if these questions are "DUH!" questions...i'm in the semi-early stages of planning still and haven't done that much reading yet...
 
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