Lots of styles to chose, search ebay for "fostex speaker box" From Moldova
Speaker box for Fostex FE126E pair, ebony, Bass Reflex Type | eBay
Speaker box for Fostex FE126E pair, ebony, Bass Reflex Type | eBay
What port size and length should I use for a 0.76L box with a 4" driver? the calculator sites dont let me choose a 4" driver and just give me errors or "infinity" when i choose anything bigger than 0.1inches diameter and negative port length of infinity?? It also doesnt work if I choose a tuning frequency below 100hz. the port length becomes infinity or some ridiculous number
Last edited:
The port length depends on port radius, box size, and desired tuning frequency. See the attached formula below. (note that the formula assumes that the port is mounted flush, with the other end free. keep the free end away from interior walls by a couple inches if possible.)
"Lv" is the vent length (meters).
"c" is the speed of sound in air ~ 343 m/sec.
"R" is vent radius (1/2 of diameter, meters).
"Vb" is net air volume in box (m^3).
"fb" is the tuning frequency. (Hz)
There is a minimum vent diameter, which depends on the driver parameters, but since there are no measurements on this one, some assumptions (maybe based on experience) need to be made. I would estimate that you could use maybe a minimum 3/4" diameter or possibly a 1-1/2" diameter port. Notice how "Lv" gets longer as the port radius gets larger. The formula assumes all metric units, so convert from inches to meters (not mm or cm). Also, input Radius, not diameter for the formula.
And as far as fb, without speaker measurements, I would guess that with a 4" woofer, you might be able to get down to 80 or 90 Hz, or possibly 60 Hz -- depending on the woofer.
Use consistent units (metric: meters, seconds)
Hope this helps.
Attachments
Last edited:
Just a reminder - be sure to input volume Vb in m^3, not liters.
And mounting the port, you can have the free end sticking out, but the other end needs to flush with the inside of the panel in that case. The 1.463 factor accounts for that configuration. If you have it partially sticking into the box, and part of it out so that both ends are free, then all bets are off on using that formula. The 1.463R is an end correction factor, assuming one end flush mounted, and one end free.
And mounting the port, you can have the free end sticking out, but the other end needs to flush with the inside of the panel in that case. The 1.463 factor accounts for that configuration. If you have it partially sticking into the box, and part of it out so that both ends are free, then all bets are off on using that formula. The 1.463R is an end correction factor, assuming one end flush mounted, and one end free.
Last edited:
FWIW, while the pioneers preferred an Av = Sd for max power/efficiency, a 4" has a ~3.15" effective diameter [TL size vent], medium power = 1/3 Sd = ~2.3" dia., low power = Sd/4 = 1.25" dia..
GM
Should be large enough if they don't get 'hit' with > ~25 W @ Fb [tuning].
Well, low as practical is ~0.707x Fs, but we don't know what that might be unless it was listed on the box it came in. That said, way back when, 4" mobile audio was around 80 Hz with a high Qt, so guessing ~56 Hz is about as low as practical.
GM
Actually, 1.463R happens to be 2x one baffled-one free [~0.732], so apparently whoever came up with this formula apparently planned/assumed the other end would be braced/supported with an end plate that had at least a ~0.613R larger area basic pipe end correction. If true, then free-free = 2x 0.613 = ~1.2276.
All that said, I don't recall this formula being all that accurate, tuning too low, so this lower end correction would tune it even lower.
IIRC, Pi Align's vent calc was more accurate: http://www.pispeakers.com/PiAlign.doc
GM
I've been using that 1.463 correction factor for years. Had to scratch around a bit to recall where I got it. 
In the text, "Basic Acoustics" by Donald E. Hall, (1993 Kreiger Publishing Co.). end correction factors are given as alpha = 0.61 for unflanged long pipe, 0.82 for flanged long pipe. These add to 1.43. End correction factor for a flanged short pipe is given as 0.79.
Hall notes, "For a pipe of finite length, the proper factor is presumably somewhere between 0.79 and 0.82." For all practical purposes, it's not a big difference.
He also provides some experimental results that were obtained using different flange widths vs. pipe radius, referencing earlier work by Benade and Murday. There is a curvefit of the data, showing the factor ranging from 0.61 to 0.82, as a function of the ratio of flange width to pipe radius.
I've used the 1.43 factor with consistent results. It is likely somewhat conservative, but it seems appropriate for the low to medium power levels that I tend toward. And it's a convenient mounting configuration to build. Works for me.
In the text, "Basic Acoustics" by Donald E. Hall, (1993 Kreiger Publishing Co.). end correction factors are given as alpha = 0.61 for unflanged long pipe, 0.82 for flanged long pipe. These add to 1.43. End correction factor for a flanged short pipe is given as 0.79.
Hall notes, "For a pipe of finite length, the proper factor is presumably somewhere between 0.79 and 0.82." For all practical purposes, it's not a big difference.
He also provides some experimental results that were obtained using different flange widths vs. pipe radius, referencing earlier work by Benade and Murday. There is a curvefit of the data, showing the factor ranging from 0.61 to 0.82, as a function of the ratio of flange width to pipe radius.
I've used the 1.43 factor with consistent results. It is likely somewhat conservative, but it seems appropriate for the low to medium power levels that I tend toward. And it's a convenient mounting configuration to build. Works for me.
Last edited:
Material thickness: 1/2”
Cutout dia: 3-3/4”
Mounting depth: 2-1/4”
Overall size: 5-5/8” L x 5-3/4” W x 3-1/8” D
Speaker box size that I have. I have two of them.
they are made of some kind of MDF
the speaker magnet area and basket area in the box is not very large. so doesnt take up much of the box. about average size for a cheap 4" speaker driver
the dustcaps have a neat feature where they pop out if you push them in accidentally and are quite tough dustcaps too. not easy to dent them inwards unless your trying to. and they pop right back out.
Cutout dia: 3-3/4”
Mounting depth: 2-1/4”
Overall size: 5-5/8” L x 5-3/4” W x 3-1/8” D
Speaker box size that I have. I have two of them.
they are made of some kind of MDF
the speaker magnet area and basket area in the box is not very large. so doesnt take up much of the box. about average size for a cheap 4" speaker driver
the dustcaps have a neat feature where they pop out if you push them in accidentally and are quite tough dustcaps too. not easy to dent them inwards unless your trying to. and they pop right back out.
I've been using that 1.463 correction factor for years. Had to scratch around a bit to recall where I got it.
FWIW, a vent length formula using the 1.463R correction factor was published in one of the Audio Amateur / Speaker Builder magazines, late 80's. I don't remember who was given credit for it. It's bound to still be in a box around here somewhere.
well I learned the speaker enclosure I had was very undersized and produced extremely little bass
I bought some dayton audio MK402 bookshelf style speakers and they sound great but have some port chuffing noise. I stuffed the ports with an 18650 battery cell with a sock around it and they sound the same but with no port noise. amazing sound from them sounds like a subwoofer is in my room because of the amount of bass. these can output. very clear sound quality crisp sparkling smooth treble mids and rich deep smooth clear bass
I bought some dayton audio MK402 bookshelf style speakers and they sound great but have some port chuffing noise. I stuffed the ports with an 18650 battery cell with a sock around it and they sound the same but with no port noise. amazing sound from them sounds like a subwoofer is in my room because of the amount of bass. these can output. very clear sound quality crisp sparkling smooth treble mids and rich deep smooth clear bass
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.