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Old 1st December 2012, 01:55 PM   #21
xrk971 is offline xrk971  United States
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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.
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Old 1st December 2012, 02:04 PM   #22
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by chrisb View Post
If those are internal dimensions, I think you're actually at 186.5 in^3 = 3.05 liters - if sealed, probably not much of an issue.

How about trying to apportion dimensions (for each compartment) on a GR basis? - IOW, .618 x 1 x 1.618

I use a cube root calculator to find the central value based on the net volume, then factor the other 2 from that figure

In the above case, those numbers would work out to 3.55"D x 5.75" W x 9.3"H. - might be a bit shallow, but you get the idea..
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.Foam Core Board Speaker Enclosures?

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.
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Old 1st December 2012, 02:14 PM   #23
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Quote:
Originally Posted by scales11 View Post


mrduke,
How can I check for distortion and the dispersion you mention?
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'
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Old 1st December 2012, 02:16 PM   #24
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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?
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Old 1st December 2012, 02:23 PM   #25
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by scales11 View Post
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?
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 TABAQ TL for Tang Band to see how I did this for a mass loaded transmission line - the Tabaqube.

Last edited by xrk971; 1st December 2012 at 02:40 PM.
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Old 1st December 2012, 02:51 PM   #26
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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...
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Old 1st December 2012, 03:03 PM   #27
xrk971 is offline xrk971  United States
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The Lepai is a great amp for this, I love it, and for the price you cannot beat it. If you are currently using the Lepai sans case and it works, I see no reason why it would not work in your boom box. I look forward to seeing your plans.
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Old 1st December 2012, 03:35 PM   #28
xrk971 is offline xrk971  United States
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Check out this link for tips on designing TML's - very helpful tips. S.A.M. "Saburov Audio Manufacture"
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Old 1st December 2012, 05:40 PM   #29
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One quick note on the vibration I saw/heard:
Click the image to open in full size.

-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.

Last edited by scales11; 1st December 2012 at 05:50 PM.
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Old 2nd December 2012, 02:56 AM   #30
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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.
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