The use of passive radiators is perhaps one of the most compact ways to extend bass. The Logitech x-140 speakers do this and sound real nice at $28, it will be tough to beat this price as a DIY for same small volume. As Sreten said, cannibalizing parts of these speakers is a lot less expensive than buying parts on their own.
What about a flat low profile box as a transmission line? I did one as a stereo pair and they sound great with 3.5 in drivers. You can scale the enclosure smaller and it will still sound pretty good I think, check post 35 in this thread if you are interested.http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures-2.html
The nice thing about flat enclosures is that you can lean them against a wall and not have to deal with power robbing BSC circuit.
I have been thinking about building a stereo PC speaker flat panel pair tml for my desk computer with 2 in drivers.
as the tweeter is closer to the wavelenghts to be reproduced...it's its field!
otherwise, the highs from a cone speaker come out pretty from the center
of the driver , being too fast for the whole membrane. Add to this the fact
that as the frequency rises ,also the beaming is more and more focused
on axis to the driver only ... etc etc etc.
So the dispersion is when you can ear even from an angled position the
same broad spectrum range that you hear in front of the speaker. so it's also
a matter of how energy is transmitted to the air through these 'devices'
XKR971,
I think you may have meant post #16? Those definitely look interesting...
I would definitely be interested in this. I will have to figure out how to scale it. Could I build a "boombox" style enclosure but make the inside flat like this? Would this remove the need for a tweeter and possibly filters?
Granted, I realize filters are probably the way to get the best sound, perhaps this design would just give me a decent solution?
I think you may have meant post #16? Those definitely look interesting...
I would definitely be interested in this. I will have to figure out how to scale it. Could I build a "boombox" style enclosure but make the inside flat like this? Would this remove the need for a tweeter and possibly filters?
Granted, I realize filters are probably the way to get the best sound, perhaps this design would just give me a decent solution?
Yes post 16, my mistake. If you use it flat against a wall, no filter is needed and if you use the TC9FD you do not need a tweeter as this thing excels at the high end if you look at specs. In fact it is used as the tweeter on the Manzanita OB project with great results. The filter is needed if you are away from wall to kill off the high end, but you may find that it is still suitable as is with some EQ'ing.
I scaled it by making cross sectional area of line at least 3x to 4x of Sd and length to be set at your desired low bass tuning freq given size constraint. Driver placement is at about 1/3 of distance from closed end. That's pretty much how I scaled mine down from original design posted on German forum.
In a boom box, you can fold 3 dimensionally to get longer lengths. See post 450 in thread http://www.diyaudio.com/forums/full-range/88787-tabaq-tl-tang-band-45.html to see how I did this for a mass loaded transmission line - the Tabaqube.
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xrk971,
Great, thanks for this tip. I will definitely check out those drivers and work up a design. I will post a cross section of my plan just to make sure I am thinking about this correctly.
I actually have the same lepai amp and was planning to use it. I took it out of the enclosure though because I had fit it into a different project. Do you think it will have any interference problems without its housing? I plan on using it in this boombox...
Great, thanks for this tip. I will definitely check out those drivers and work up a design. I will post a cross section of my plan just to make sure I am thinking about this correctly.
I actually have the same lepai amp and was planning to use it. I took it out of the enclosure though because I had fit it into a different project. Do you think it will have any interference problems without its housing? I plan on using it in this boombox...
Check out this link for tips on designing TML's - very helpful tips. S.A.M. "Saburov Audio Manufacture"
One quick note on the vibration I saw/heard:
-the speaker is snug inside a cutout hole
-the top cardboard piece is not glued, but flush
-rest of enclosure is held by hot glue
The vibration seemed to be originating from the inside edge of the b3s driver(like on a rubber membrane). It is not always present in every song I played. It is possible that the membrane happens to be flapping against the cardboard, now that I think about it.
I just wanted to know if this sort of noise could be something else that I have not considered.
I will read up on the TML design, I am working with a relatively small box (since my original design wasa 5",5",5" cube) but shall see what I can come up with.
-the speaker is snug inside a cutout hole
-the top cardboard piece is not glued, but flush
-rest of enclosure is held by hot glue
The vibration seemed to be originating from the inside edge of the b3s driver(like on a rubber membrane). It is not always present in every song I played. It is possible that the membrane happens to be flapping against the cardboard, now that I think about it.
I just wanted to know if this sort of noise could be something else that I have not considered.
I will read up on the TML design, I am working with a relatively small box (since my original design wasa 5",5",5" cube) but shall see what I can come up with.
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Do the vibration disappear at lower volumes? Have you tried to press the different sides of the cardboard to see if it disappears? I would not worry too much, cardboard is pretty flimsy and starts to vibrate quite easy especially if you have a closed box.
Regarding the dispersion of the high frequencies, it is easy to determine if you think you need it or not. It is sort of personal taste I think.
Sit directly in front of the speaker, so the speaker is "pointing" towards you face (ears) You will hear the "full range". Then move like 30 degrees of axis, so the speaker is no longer pointing directly towards you. You will hear a different frequency response where the high freqs are weaker. Then do the same for 90 degrees.
If you still think the music sounds ok and not dull, then you do not need to add tweeters.
This is a special problem that arises for boom boxes and radios, but never for conventional hifi systems where the listeners are confined to a well defined space (sofa) in front of the systems. For boomboxes and small radios, the listeners tend to be all around the system. So it sort of depends of your user case.
Regarding the dispersion of the high frequencies, it is easy to determine if you think you need it or not. It is sort of personal taste I think.
Sit directly in front of the speaker, so the speaker is "pointing" towards you face (ears) You will hear the "full range". Then move like 30 degrees of axis, so the speaker is no longer pointing directly towards you. You will hear a different frequency response where the high freqs are weaker. Then do the same for 90 degrees.
If you still think the music sounds ok and not dull, then you do not need to add tweeters.
This is a special problem that arises for boom boxes and radios, but never for conventional hifi systems where the listeners are confined to a well defined space (sofa) in front of the systems. For boomboxes and small radios, the listeners tend to be all around the system. So it sort of depends of your user case.
I will check on this and get back to you.
Thanks for clearing this up, I will check. I think the speakers sounded pretty good from the side. I bet I could keep it simple and avoid the tweeter.
I am reading up on the TML calculation, I am not sure what wavelength I should try and calibrate to...
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Can anyone direct me to a good website (other than the S.A.M) that can explain how I properly calculate and layout the TML channel dimensions?
I think (for my driver ) that a channel cross-section area of about 30cm^2 or 2" by 2" would be good. I am unsure how long I should make it be though, especially since I read that you can stuff the channel with stuff to decrease the necessary length. Since I am trying to work within a small footprint, I think I may have to do something tight, like
S.A.M. "Saburov Audio Manufacture"
But on the other hand, maybe this sort of design would suffice:
How do I apply the golden ratio for something like this?
I think (for my driver ) that a channel cross-section area of about 30cm^2 or 2" by 2" would be good. I am unsure how long I should make it be though, especially since I read that you can stuff the channel with stuff to decrease the necessary length. Since I am trying to work within a small footprint, I think I may have to do something tight, like
S.A.M. "Saburov Audio Manufacture"
But on the other hand, maybe this sort of design would suffice:
How do I apply the golden ratio for something like this?
Hi, As you say being a cannibal is good, but some don't like it, rgds, sreten.
The dynamic bass management in the X-140's is AFAIK impossible to DIY.
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Agree that it would be hard to DIY for reasonable cost, not sure if 'impossible' would be the word. Just two passive radiators will set you back $20. Personally, The x-140 is so good and nice, it would be a shame to cannibalize it. I am just saying there is a treasure trove of parts in these mass produced PC speakers.
oops, a little late..."how to apply the GR to something like this?"
Well you need to have an idea about the length of the line required and the placement of the driver within the line. Determine a cabinet width (many times this seems to be almost arbitrary, but depending on the driver the width obviously must be narrower than the mounting "width"). So we know the line length, and a width. So we can determine a taper ratio. It can be a bit of hit and miss (I've never sat down to do the mathematics of it though). I use Google's "sketchup" drawing program, and draw a 2-D rectangle and try to fit the line within the envelope of an arbitrary box. Remember though that the line length is a function of the driver dimensions (as a start).
But on the other hand, maybe this sort of design would suffice:
How do I apply the golden ratio for something like this?
Well you need to have an idea about the length of the line required and the placement of the driver within the line. Determine a cabinet width (many times this seems to be almost arbitrary, but depending on the driver the width obviously must be narrower than the mounting "width"). So we know the line length, and a width. So we can determine a taper ratio. It can be a bit of hit and miss (I've never sat down to do the mathematics of it though). I use Google's "sketchup" drawing program, and draw a 2-D rectangle and try to fit the line within the envelope of an arbitrary box. Remember though that the line length is a function of the driver dimensions (as a start).
Try modeling it with HornResp, it will open up many possibilities rather than relying on golden ratio. You will have to imagine how stuffing will dampen out peaks when using HR. But it gives good idea of bass extension and where first few resonance peaks will be. Pretty easy to use software.
This trinagular labyrynth on the same driver has smaller footprint, but it is taller:
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Its the same labyrynth pipe like you quated but turned just once
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