OK, bear with me a moment.
Goal: for $100 or so, get the most pleasant PC sound I can at a wall-facing table. (10'x10' room, home office) I've already ordered one of those $30 "Sonic Impact" digital amps that have been discussed elsewhere.
Simplicity and small size seem to point to (a) single drivers and (b) a t-line enclosure as described here (http://www.t-linespeakers.org/design/rules.html)
Were I to use the Fostex FE-103E, which seems to be the best that fits my budget and which has an Fs of 79.5 Hz, that indicates a 42.5" straight t-line, with an appropriate width and taper, a project that seems simple enough with mdf and some damping substance, plus the requisite stuffing. These things would be smack up against the wall (I'm happy to sacrifice imaging) and I'm hoping to manage w/o baffle-step correction.
Listening would be nearfield, like about 3 feet away -- the speakers would be more or less jammed between table and wall. I worry about the upper-treble unevenness of these drivers, being that close. Might it make sense to point the drivers at the ceiling instead?
More importantly, am I nuts? Am I overlooking something crucial? Thanks in advance for any sage advice.
Goal: for $100 or so, get the most pleasant PC sound I can at a wall-facing table. (10'x10' room, home office) I've already ordered one of those $30 "Sonic Impact" digital amps that have been discussed elsewhere.
Simplicity and small size seem to point to (a) single drivers and (b) a t-line enclosure as described here (http://www.t-linespeakers.org/design/rules.html)
Were I to use the Fostex FE-103E, which seems to be the best that fits my budget and which has an Fs of 79.5 Hz, that indicates a 42.5" straight t-line, with an appropriate width and taper, a project that seems simple enough with mdf and some damping substance, plus the requisite stuffing. These things would be smack up against the wall (I'm happy to sacrifice imaging) and I'm hoping to manage w/o baffle-step correction.
Listening would be nearfield, like about 3 feet away -- the speakers would be more or less jammed between table and wall. I worry about the upper-treble unevenness of these drivers, being that close. Might it make sense to point the drivers at the ceiling instead?
More importantly, am I nuts? Am I overlooking something crucial? Thanks in advance for any sage advice.
Been there. Done that. They sound great. Use the FE107E rather than FE103E. It has a smoother response, and a bucking magnet.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36305
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36305
thanks
Thanks! Much to think about. Did anyone ever build the Locust 2? It looks interesting too. There was also brief mention by GM of another taller speaker with the 127E (Locust 3?)
Any advice would be welcome; anything up to 48" high would work.
And a dumb question:
At what point does a t-line become a ported box, or does it matter? (More prosaically, are Locusts 1 and 2 being figured with the the ported box or t-line worksheets?) I notice Locusts don't taper; on the other hand I noticed with the open-end t-line worksheets that really small vents sometimes worked nicely, which is more or less what the locust 1 seems to have.
Thanks! Much to think about. Did anyone ever build the Locust 2? It looks interesting too. There was also brief mention by GM of another taller speaker with the 127E (Locust 3?)
Any advice would be welcome; anything up to 48" high would work.
And a dumb question:
At what point does a t-line become a ported box, or does it matter? (More prosaically, are Locusts 1 and 2 being figured with the the ported box or t-line worksheets?) I notice Locusts don't taper; on the other hand I noticed with the open-end t-line worksheets that really small vents sometimes worked nicely, which is more or less what the locust 1 seems to have.
progress...
I'm answering some of my own questions ... in Martin King's ported box worksheet, and FE127E specs produce nice-looking results for
L=40
zdriver=2
zport=36
S0,SL=60
Density=.9
rport=.75
Lport=.75
especially if you add a little resistance -- can I just up Re by an ohm or two to experiment with an added series resistor?
The bottom-end output is definitely better-behaved (at least in the model) than in the t-line. I can't figure out how to get the worksheet let me try different stuffing levels in different parts of the box ... or does that not matter?
Given that the worksheet only does top-to-bottom standing waves, should I worry about sideways waves? I'm thinking about say 12 inches wide and 5 deep as interior dimensions.
I'm answering some of my own questions ... in Martin King's ported box worksheet, and FE127E specs produce nice-looking results for
L=40
zdriver=2
zport=36
S0,SL=60
Density=.9
rport=.75
Lport=.75
especially if you add a little resistance -- can I just up Re by an ohm or two to experiment with an added series resistor?
The bottom-end output is definitely better-behaved (at least in the model) than in the t-line. I can't figure out how to get the worksheet let me try different stuffing levels in different parts of the box ... or does that not matter?
Given that the worksheet only does top-to-bottom standing waves, should I worry about sideways waves? I'm thinking about say 12 inches wide and 5 deep as interior dimensions.
Sorry I missed the read-me-first! Where is it? And yes, you seem to be right about t-lines.
The worksheets are highly educational -- I know this is clear to most folks on this board , but I now understand why t-lines tend to use bigger speakers than 4" and why the smaller speakers work better with horns or ported boxes. And the exchanges between folks on this board that quote worksheet results are useful, as you get to see how people move between the model and the real world.
The worksheets are highly educational -- I know this is clear to most folks on this board , but I now understand why t-lines tend to use bigger speakers than 4" and why the smaller speakers work better with horns or ported boxes. And the exchanges between folks on this board that quote worksheet results are useful, as you get to see how people move between the model and the real world.
CD said:
First link in the ToC (right after the donations links)
http://www.t-linespeakers.org/readme1st.html
dave
It depends on how you define a TL, something that seems to vary over the decades and folk's opinions. My description is a well stuffed 1/4WL straight taper tube that has an FR very close to the driver's IB response. Once it begins to exhibit 4th order roll off characteristics it becomes a ML-TL IMO.
Yes, but you must also change Qed and BL:
Qes' = Qes*(1+Rs/Rvc), where Rs is the series
resistance and Rvc is the driver's DC resistance, so:
Rs = (Qes'/Qes-1)*Rvc. Remember to include the series
resistances of your amplifier/cable/inductors in Rs,
so the actual resistor you buy may be somewhat
smaller than calculated value.
Qts' = Qes'*Qms/(Qes'+Qms)
Vas is unchanged
Then to find B*L:
Cms = Vas/(Sd^2*rho*c^2)
where:
Vas is in m^3 (liters*0.001)
Sd is in cm^2
c is in meters/sec*0.0001 to get Cms in mm/N
then:
Mms = 1/[(2*pi*Fs)^2*Cms]
BL = [(2*Pi*Fs*Re*Mms)/Qes]^0.5
Note that there's no need to calc Qts' since the WS will, I just copied/pasted this info from another post of mine on another TL thread.
It can. Which version of which WS?
Since these are 1/2WL, the dims have to quite large before they fall into the BW where the stuffing won't damp it sufficiently, or if little is used, like in most of my designs and why I use golden or acoustic ratios for width/depth in straight pipes.
GM
Thanks GM! As far as the worksheet, I'm having difficulty with "Driver in a Ported Box (Bass Reflex) - Acoustic and Electrical Response 12/20/03" Variable section-stuffing was easy in "TL Sections," but in "Ported Box" it looks like I need to specify something else first before I can vary stuffing densities.
OTOH I can't find anyone out there who stuffs ported boxes variably so maybe it doesn't matter.
Thanks lots for the other guidance!
OTOH I can't find anyone out there who stuffs ported boxes variably so maybe it doesn't matter.
Thanks lots for the other guidance!
Serious designers do!CD said:
You're welcome!
OK, this looks like the earlier version, so just highlight, right click on one of the '0.lb.ft^3' to copy it, then double click and paste it in the various 'density' fields. If you decide that some fields can always be the same, then change them back to 'density' and input it just once in the 'enclosure geometry definition' section.
GM
results
Since folks were so generous with advice I wanted to report back on results. Ended up with the Fostex FE127E in a t-line as short as it was wide. Internal dimensions were about 22”x5.5” at the driver end, narrowing to the vent which is 5.5” across and just over 0.5” wide; internal height is 22” In the language of the Martin King worksheets L=22, S0=11Sd, SL=0.3Sd. This let me make the thing in the shape of an isosceles right triangle, and cut all the front and back panels (24”x24”x~34” triangles) from one 2’x4’ sheet of Home Depot particle board. So the driver is at one 24” end, and the cabinet then narrows, asymmetrically, to a point at the vent end. Cabinets were braced, damped, foam-lined, and stuffed at the driver end.
I turned the cabinets upside down, with the vents facing up, and bolted them to either side of the shelving unit that extends above the back of my desk. So listening is substantially off-axis.
Sound: I tried them with both a NAD 304 and with the low-power Sonic Impact amp they were made for. Bass: recessed but well-defined, and I can fix some of this with EQ on the PC. Midrange: nice and fairly natural-sounding. Voices are good, sometimes startlingly good. Highs: only tolerable -- to my ears there's something hard-edged and limited about this driver's upper end. Dynamics: at low levels, fine. For the price I’m quite happy with them, but if I were to spend much more I think I’d move to a good tweeter and crossover. I'd love to hear the fabled Jordan fullrange driver, though.
Since folks were so generous with advice I wanted to report back on results. Ended up with the Fostex FE127E in a t-line as short as it was wide. Internal dimensions were about 22”x5.5” at the driver end, narrowing to the vent which is 5.5” across and just over 0.5” wide; internal height is 22” In the language of the Martin King worksheets L=22, S0=11Sd, SL=0.3Sd. This let me make the thing in the shape of an isosceles right triangle, and cut all the front and back panels (24”x24”x~34” triangles) from one 2’x4’ sheet of Home Depot particle board. So the driver is at one 24” end, and the cabinet then narrows, asymmetrically, to a point at the vent end. Cabinets were braced, damped, foam-lined, and stuffed at the driver end.
I turned the cabinets upside down, with the vents facing up, and bolted them to either side of the shelving unit that extends above the back of my desk. So listening is substantially off-axis.
Sound: I tried them with both a NAD 304 and with the low-power Sonic Impact amp they were made for. Bass: recessed but well-defined, and I can fix some of this with EQ on the PC. Midrange: nice and fairly natural-sounding. Voices are good, sometimes startlingly good. Highs: only tolerable -- to my ears there's something hard-edged and limited about this driver's upper end. Dynamics: at low levels, fine. For the price I’m quite happy with them, but if I were to spend much more I think I’d move to a good tweeter and crossover. I'd love to hear the fabled Jordan fullrange driver, though.
Many full-range drivers, such as the FE127E and Jordan JX92S, take on a different personality when driven by a tube or current source amp.
http://www.6moons.com/audioreviews/firstwatt/firstwatt_2.html
http://www.6moons.com/audioreviews/firstwatt/firstwatt_2.html
To cut a long story short ...
I have worked on this driver and since I am now aware that Fostex will not continue manufacturing these anymore, I gave up building.
If you can place the speaker unit lower then the start of the line you can prevent midrange to enter the line. By this way, you can have a well balanced sound.
I worked this out with AJ-Horn and if you need the simulation response, I can send it to you to your private email address.
-Onur
I have worked on this driver and since I am now aware that Fostex will not continue manufacturing these anymore, I gave up building.
If you can place the speaker unit lower then the start of the line you can prevent midrange to enter the line. By this way, you can have a well balanced sound.
I worked this out with AJ-Horn and if you need the simulation response, I can send it to you to your private email address.
-Onur
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