This will possibly be my first ported subwoofer build. I generally stick to sealed for simplicity and to keep the bass tight. Currently looking at a pair of Eminence Lab15 drivers in their "Medium Sized Vented Club Sub" configuration, 2 drivers / 2 cabinets. Distributed bass, you know the drill.
My question is this. They're asking for a 6.5x6.5x21.9 port, which equals 0.535cuft of port volume. If I rearrange that as a slot of 17x2.5x21.75 (0.534cuft), will I be running in to any issues with box tuning? Not sure if a slot reacts any differently than a rectangle port or whatever. Really boils down to cabinet aesthetics and the slot seems to tie in better with the dimensions I'm after.
Link to cabinet: https://buyeminence.com/img/product/description/LAB_15_cab.pdf
TIA all. Appreciate any criticism, constructive or otherwise.
My question is this. They're asking for a 6.5x6.5x21.9 port, which equals 0.535cuft of port volume. If I rearrange that as a slot of 17x2.5x21.75 (0.534cuft), will I be running in to any issues with box tuning? Not sure if a slot reacts any differently than a rectangle port or whatever. Really boils down to cabinet aesthetics and the slot seems to tie in better with the dimensions I'm after.
Link to cabinet: https://buyeminence.com/img/product/description/LAB_15_cab.pdf
TIA all. Appreciate any criticism, constructive or otherwise.
I watched a presentation on this recently - it was like a Ted talk. Ultimately, cylindrical ports are superior to slots. (It has something to do with uniformity of air-speed within the vent).
I believe slot ports result in 'lazy' bass. When I don't understand things due to my technical limitations I try to imagine the application in an alternative 'real world' scenario.
How far can a smoker blow a smoke ring with a smile on his face? Whenever we need to inhale and exhale quickly - we purse our lips.
#shitwedontneedaspreadsheetfor.
I believe slot ports result in 'lazy' bass. When I don't understand things due to my technical limitations I try to imagine the application in an alternative 'real world' scenario.
How far can a smoker blow a smoke ring with a smile on his face? Whenever we need to inhale and exhale quickly - we purse our lips.
#shitwedontneedaspreadsheetfor.
With this driver rated at an fs of 28 hertz...it's just too high. I consider an f3 above 25-30 hertz just "too light".
I recently modeled a full-range driver with an F3 of 23 hertz & was pleasantly surprised it would reach that low...Now, a purpose-built subwoofer should actually reach down to our hearing limit, not hit an F3 till it's passed below 20 hertz. These low frequencies exist, a pipe organ bottom note is around 16 hertz. Granted these tones are well into a sensation, rather than a heard thing...it is a grey area. Myself, I can oddly hear well towards & thru 20 hertz. Drivers do exist which will model into the mid-teens no problem. The "large enclosure" on Eminences website with an F3 at 20.37 hertz would be a far better choice if your fully prefer that driver...don't compromise with the smaller enclosure.
-------------------------------------------------------------------------Rick......
I recently modeled a full-range driver with an F3 of 23 hertz & was pleasantly surprised it would reach that low...Now, a purpose-built subwoofer should actually reach down to our hearing limit, not hit an F3 till it's passed below 20 hertz. These low frequencies exist, a pipe organ bottom note is around 16 hertz. Granted these tones are well into a sensation, rather than a heard thing...it is a grey area. Myself, I can oddly hear well towards & thru 20 hertz. Drivers do exist which will model into the mid-teens no problem. The "large enclosure" on Eminences website with an F3 at 20.37 hertz would be a far better choice if your fully prefer that driver...don't compromise with the smaller enclosure.
-------------------------------------------------------------------------Rick......
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"Drivers do exist which will model into the mid-teens no problem."
This is fortuitous timing, since I'm still in the searching stage for a 15" which will give me an F3 of 25 to 30 Hz in an approximately 7 to 8 cubic ft. box, ported. The Eminence Lab 15 has some nice qualities, but I'm concerned about its upper end, since I want the driver to handle up to about 150 Hz. Eminence specs 100 Hz as the usable top end.
I don't care about 32 foot organ pipes. Can't remember the last time I listened to an organ piece which used that. But, I do like and want some of the LF of thunder, trains, etc.
Do you have some recommendations of high quality high output drivers which will do both 25 Hz and 200 Hz? (Not "modelling", real world.)
Thanks!
This is fortuitous timing, since I'm still in the searching stage for a 15" which will give me an F3 of 25 to 30 Hz in an approximately 7 to 8 cubic ft. box, ported. The Eminence Lab 15 has some nice qualities, but I'm concerned about its upper end, since I want the driver to handle up to about 150 Hz. Eminence specs 100 Hz as the usable top end.
I don't care about 32 foot organ pipes. Can't remember the last time I listened to an organ piece which used that. But, I do like and want some of the LF of thunder, trains, etc.
Do you have some recommendations of high quality high output drivers which will do both 25 Hz and 200 Hz? (Not "modelling", real world.)
Thanks!
Thank you all for the responses thus far.
I have no want nor need for anything below the upper 20s really. How deep does a Hammond tonewheel go? The only organs I ever hear are wheeled on stage and wheeled back off at the end of the show. Every once in a while it's scotch and cigars but our lives are mostly the beer and tequila kind.
Each subwoofer needs to occupy a 2x4 space flanking a fireplace. This space also needs to be shared with a pair of stand mounts. As you can see, it's quite limited and I would much rather trade space in the room for a few extra Hz.
I'm also flirting with the idea of those Peerless units but I'd need to double my amplification. Currently have an unused Crest Pro-Lite 3.0dsp, which should decently power a pair of the Eminence, but I'd need a 2nd one for the Peerless drivers.
Seems with the Eminence I can theoretically keep a slot tuned to 30Hz (dimensions are at work, sorry) on a 24dB filter at 25Hz and have a port velocity of 18m/s. When I was originally modelling this driver, I had a few parameters off so I was getting super funky port data out of winISD. How does this work in life vs theory? That's the question...
I also have 4 Precision Ports in storage that I'll have to dig out. Maybe that's a better option? Can't remember what size they are though.
I have no want nor need for anything below the upper 20s really. How deep does a Hammond tonewheel go? The only organs I ever hear are wheeled on stage and wheeled back off at the end of the show. Every once in a while it's scotch and cigars but our lives are mostly the beer and tequila kind.
Each subwoofer needs to occupy a 2x4 space flanking a fireplace. This space also needs to be shared with a pair of stand mounts. As you can see, it's quite limited and I would much rather trade space in the room for a few extra Hz.
I'm also flirting with the idea of those Peerless units but I'd need to double my amplification. Currently have an unused Crest Pro-Lite 3.0dsp, which should decently power a pair of the Eminence, but I'd need a 2nd one for the Peerless drivers.
Seems with the Eminence I can theoretically keep a slot tuned to 30Hz (dimensions are at work, sorry) on a 24dB filter at 25Hz and have a port velocity of 18m/s. When I was originally modelling this driver, I had a few parameters off so I was getting super funky port data out of winISD. How does this work in life vs theory? That's the question...
I also have 4 Precision Ports in storage that I'll have to dig out. Maybe that's a better option? Can't remember what size they are though.
None still available.
Anyway, to the 1st approximation:
Low corner sets Fs = 25*.707 = ~17.68 Hz Fs
For vented, Vb sets Vas for optimal Fs tuning = 8 ft^3*1.44 = 11.52 ft^3
Qts' sets BW = ~17.68*2/200 = ~0.1768 Qts'
Vb sets box efficiency, so guessing per chart: 8 ft^3 = ~1.5% = ~93.76 dB
Qts' = Qts + any added series resistance [Rs]: Calculate new Qts with Series Resistor
You might find a driver with 'close enough' specs at some exorbitant price, but down low were're normally trading efficiency for BW, smaller box.
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Ragtag,
1)The lowest Hammond low footpedal note is "C", 32.69 Hz, though a Leslie speaker has little output that low- the second harmonic (65.38Hz) is predominant.
For comparison, low note on a grand piano is "A" 27.5 Hz, low "B" on a 5 string bass is 30.87Hz, 41.2Hz low "E" on a four string bass. On those string instruments, the second harmonic will usually be 6-10dB (or more) louder than the fundamental.
2) The turbulence noise from 18m/s will not be audible above the levels in typical music at a distance of a few meters.
I have extensively used dual LAB12 subs with similar simulated port velocity, even without the top cabinets couldn't detect any port noise using trianglular corner ports using music, though could just detect noise using sine waves at full power at Fb.
3) Flared port ends are a good idea, you can use 45 degree angles on square or rectangular port inlets and outlets. If you have the 4" Precision Ports, three would still be less than the area of 6.5" x 6.5". A pair of their 6" ports would be a bit more area, requiring a longer port length for the same tuning.
Art
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