[MacTheCat]

PartsExpress has a fairly large gallery of projects to look through. I am thinking of building 5 of these for my soon to be home theater.

 

[Garbz]

I should have mentioned the arguement for bookshelf too. Smaller cabinet means less box resonance. Easier to support internally. And judging by your plans to corner load one speaker or place one under the stairs this is important.

Regardless of which design you choose internal bracing of the speakers and reduction of cabinet sound should be a primary priority if your speakers will be in restricted spaces like that. But I am sure plenty of DIY speaker sites will explain how to do this adequetly anyway.

 

[Chops]

Speaking of speaker projects and going for somewhat different, one-off designs, here's my next project, hopefully before the year's end.

It's an Open Baffle (dipole) design utilizing two 15" high efficiency drivers per channel and an Altec 511B/902-8B horn/driver combo. It will be bi-amped and should be right around 102-105dB @ 1W/1M.

If you haven't tried a dipole design before, then you don't know what you're missing. Think of it as open-cans vs closed-cans.

 

[Garbz]

Correct me if i'm wrong but dipoles have the bass drivers surrounding the tweeters not the tweeter on top so that everything appears to come from a co-herent point?

Mind you I think that definition changes depending on how the theory of it is applied. How is your design dipole?

 

[Chops]

Quote:

Originally Posted by Garbz /img/forum/go_quote.gif Correct me if i'm wrong but dipoles have the bass drivers surrounding the tweeters not the tweeter on top so that everything appears to come from a co-herent point? Mind you I think that definition changes depending on how the theory of it is applied. How is your design dipole?

Hate to say it, but no, that is wrong.

Dipole Speaker:

"The term dipole derives from the fact that the polar response consists of two lobes, with equal radiation forwards and backwards, and non perpendicular to the axis. This can be useful in reducing the stimulation of resonant room modes at low frequencies. It also results in high frequencies being reflected from any rear wall, which can enhance the naturalness of the sound in typical listening rooms by creating more diffuse reverberation, though in theory it could detract from stereo location.

A dipole speaker works by creating air movement (velocity) rather than pressure. It is large and flat, and open at both front and back, as is the case with electrostatic or ribbon loudspeakers, though a conventional loudspeaker driver mounted in an open baffle also works as a dipole loudspeaker. These enclosures are characterised by a "figure-of-eight" radiation pattern where the loudness falls towards the sides of the enclosure. Sometimes the enclosure is modified into an "H-frame" with the driver located on a wall dividing two open compartments. Such enclosures require some sort of control over the radiated sound from the rear of the enclosure to achieve the desired response. This is usually done by mounting two drivers one over the other in a push-pull configuration.

An advantage of dipoles is that the sound is concentrated in the listening area due to the figure-of-eight polar response. This means that for a given loudness, places that fall within the "dead-zone" of the speaker do not perceive as loud a sound as they would with more traditional enclosures."

 

[digitalmind]

Quote:

Originally Posted by rayq /img/forum/go_quote.gif How about ProAc Response 2.5 clone (http://www.geocities.com/diyproac25/links.htm)? I listened to the original one and loved it but it costs $6500 CAD, ouch!

I've seen that one before and while it may be a very nice sounding speaker (I'm going to sound a bit lame here), it doesn't look different at all. For the ultimate listening experience I'll keep the RS-1's around. I want something that's pleasing to the eye and sounds better than the average speaker.

Quote:

Originally Posted by Wodgy /img/forum/go_quote.gif No, the idea that back ported speakers are harder to place is a common misconception. It stems from people actually putting the speakers right up against a wall, which obviously does block the port. If there's adequate airflow, however, it makes no difference. All speakers sound better away from room boundaries, but again, you can reduce the baffle step compensation if you really do want speakers to go in a tight space right up against a wall. Back ported speakers also have the advantage of reduced midrange leakage towards the front (bass frequencies wrap around the cabinet because they have a longer wavelength). The first layout you gave would work. You may get a slightly more bass heavy sound from the left speaker and a slightly more uneven midrange from the wall reflection, but the advantage of being able to listen from your desk sounds like a worthwhile tradeoff to me. No one has a perfect room. It looks like you'll have adequate space behind each speaker.

Ok, that explains alot. Thanks again for the great response.

Quote:

Originally Posted by MacTheCat /img/forum/go_quote.gif PartsExpress has a fairly large gallery of projects to look through. I am thinking of building 5 of these for my soon to be home theater.

I got my main idea from there! Great site.

Quote:

Originally Posted by Chops /img/forum/go_quote.gif Speaking of speaker projects and going for somewhat different, one-off designs, here's my next project, hopefully before the year's end. It's an Open Baffle (dipole) design utilizing two 15" high efficiency drivers per channel and an Altec 511B/902-8B horn/driver combo. It will be bi-amped and should be right around 102-105dB @ 1W/1M. If you haven't tried a dipole design before, then you don't know what you're missing. Think of it as open-cans vs closed-cans.

Definitely keep us updated on that! Looks interesting. Not entirely my thing though -- looks are important here like said before. I want something that'll sound better than the average speaker but will look great. In my own weird version of great, that is.

Nice little discussion on bi-pole above. Interesting and learnsome!

I think I've found what I want to build. The Totally Tubular project here that MisterX linked (http://www.partsexpress.com/projects...lar/index.html) got me hyped up, so I did a little design on how I would make it. I"ll have 7-8 weeks to finalize plans, gather information, find all the parts, and then I can start building. I'm wondering, will there be ill effects on laying the MTM design on it's side rather than upright?

Here's what I've been doodling for the last 2 hours. It's the Totally Tubular on a stand. I'm thinking a glossy red for the actual speaker and piano black for the stands. If I can pull that paint job off, offcourse. The stand is just a quicky, but I like the look of it. It's a wide base with the top half in size of that base. The middle one is to be a tweeter offcourse -- I was lazy and just copied the woofers and made it shorter. I'll fix that tomorow.

What do you think?

Now I may be going over the top here for first time project -- but I'm thinking it'd be a cool idea to integrate a large woofer in the base.

 

[Wodgy]

Unfortunately, it's not a good idea to build the "Totally Tubular" design horizontally as you've pictured it. The Tubular is an MTM, and due to the phase interaction of the two woofers, the off-axis response of an MTM along its longest dimension is quite poor. Here's a graph showing the lobing behavior of two MTM woofers, no crossover (this is obviously the worst case, but it illustrates the principle):

http://zaphaudio.com/audio-speaker16...TM-offaxis.gif

In general, lobing in the vertical direction is not a large problem, because the range of locations where people's heads can be vertically is small, plus the ceiling is far away. On the other hand, you want to make the horizontal off-axis behavior as flat as possible, not just so that you can move around the room and have the sound be the same, but also because you want the reflections off walls to be similar in character to the main sound.

To be honest, I'm quite skeptical about the off-axis behavior of the Tubular design even as specified. There are no off-axis measurements and so it's impossible to quantify the effects of baffle diffraction, but at least the project isn't that expensive so it's not a huge risk to build it and try. But I would build it vertically as specified, not horizonally.

 

[blip]

Quote:

Originally Posted by Garbz /img/forum/go_quote.gif Correct me if i'm wrong but dipoles have the bass drivers surrounding the tweeters not the tweeter on top so that everything appears to come from a co-herent point? ?

Chops is right. What you are thinking of are coaxial speakers.

Anyway, glad to see that you are going with the tubular concept. Those things look amazing! But I'm a bit worried about using PVC. It seems like PVC resonates very differently from wood... I wonder how that will effect the sound? I suppose you can always dampen it down if necessary.

As for building a woofer into the base, it should be do-able. In fact I think I saw a similar design a few days ago.... Ahhh... here it is: http://zaphaudio.com/BAMTM-2.00-MTM-Sub.pdf

 

[digitalmind]

Quote:

Originally Posted by Wodgy /img/forum/go_quote.gif Unfortunately, it's not a good idea to build the "Totally Tubular" design horizontally as you've pictured it. The Tubular is an MTM, and due to the phase interaction of the two woofers, the off-axis response of an MTM along its longest dimension is quite poor. Here's a graph showing the lobing behavior of two MTM woofers, no crossover (this is obviously the worst case, but it illustrates the principle): In general, lobing in the vertical direction is not a large problem, because the range of locations where people's heads can be vertically is small, plus the ceiling is far away. On the other hand, you want to make the horizontal off-axis behavior as flat as possible, not just so that you can move around the room and have the sound be the same, but also because you want the reflections off walls to be similar in character to the main sound. To be honest, I'm quite skeptical about the off-axis behavior of the Tubular design even as specified. There are no off-axis measurements and so it's impossible to quantify the effects of baffle diffraction, but at least the project isn't that expensive so it's not a huge risk to build it and try. But I would build it vertically as specified, not horizonally.

Ok, that makes sense. I'm learning more from your posts than all the reading I've done so far on DIY sites. Thanks

I'm off to play with Sketchup again.

Quote:

Originally Posted by blip /img/forum/go_quote.gif Chops is right. What you are thinking of are coaxial speakers. Anyway, glad to see that you are going with the tubular concept. Those things look amazing! But I'm a bit worried about using PVC. It seems like PVC resonates very differently from wood... I wonder how that will effect the sound? I suppose you can always dampen it down if necessary. As for building a woofer into the base, it should be do-able. In fact I think I saw a similar design a few days ago.... Ahhh... here it is: http://zaphaudio.com/BAMTM-2.00-MTM-Sub.pdf

They do look amazing but I also don't really like that they use PVC. Still, it'll be fairly easy to make and easy to tweak if there is resonation.

Nice link, definitely an interesting design.

I know that bass tones are non/less directional than other sound frequencies, but is there a reason why some (mostly high end) speakers have the woofers firing sideways? I can understand downfiring, rear firing, and front firing, but what's the advantage of having the woofer fire sideways?

Here's what I'm looking at now:
http://xs.to/xs.php?h=xs110&d=06486&f=iso.png
http://xs.to/xs.php?h=xs110&d=06486&f=left.png
http://xs.to/xs.php?h=xs110&d=06486&f=front.png

 

[Wodgy]

Quote:

Originally Posted by digitalmind /img/forum/go_quote.gif They do look amazing but I also don't really like that they use PVC. Still, it'll be fairly easy to make and easy to tweak if there is resonation. Nice link, definitely an interesting design. I know that bass tones are non/less directional than other sound frequencies, but is there a reason why some (mostly high end) speakers have the woofers firing sideways? I can understand downfiring, rear firing, and front firing, but what's the advantage of having the woofer fire sideways? Here's what I'm looking at now: http://xs.to/xs.php?h=xs110&d=06486&f=iso.png http://xs.to/xs.php?h=xs110&d=06486&f=left.png http://xs.to/xs.php?h=xs110&d=06486&f=front.png

PVC tubes actually aren't a problem. Cylinders have a strong physical resistance to radial expansion and are fairly immune to resonance, much moreso than boxes (except for the one potential resonance along their length). See Linkwitz' remarks about that here:
http://www.linkwitzlab.com/Pluto/construction.htm
also, just generally, it's worth taking a look at the Pluto and Pluto+ designs:
http://www.linkwitzlab.com/Pluto/intro.htm
http://www.linkwitzlab.com/Pluto/subwoofer.htm

People use side-firing woofers because of convenience, mostly. It lets you have a cabinet with a slim front baffle and yet still have a relatively large woofer. Also, not all sub drivers are suitable for being used in a down-firing configuration. You can find how to do the math for suitability of down-firing drivers on Parts Express' site.

 

[ooheadsoo]

Not to mention the school of thought that says the less re-radiation of sound from the baffle, the better the imaging.

 

[Uncle Erik]

Have you considered taking a conventional design and then building a second, more exotic cabinet around it? Or does the unusual shape have to be functional, as well?

Personally, I'm a big fan of the ProAc 2.5 clone (not perfect, but damn good for the price and effort) and while it's a simple box, there's little reason you couldn't dress up the exterior with cutouts and/or interesting stands.

Either that, or you could pick up some exotic, figured veneer and do something interesting with a basic shape.

 

[digitalmind]

Quote:

Originally Posted by Wodgy /img/forum/go_quote.gif PVC tubes actually aren't a problem. Cylinders have a strong physical resistance to radial expansion and are fairly immune to resonance, much moreso than boxes (except for the one potential resonance along their length). See Linkwitz' remarks about that here: http://www.linkwitzlab.com/Pluto/construction.htm also, just generally, it's worth taking a look at the Pluto and Pluto+ designs: http://www.linkwitzlab.com/Pluto/intro.htm http://www.linkwitzlab.com/Pluto/subwoofer.htm People use side-firing woofers because of convenience, mostly. It lets you have a cabinet with a slim front baffle and yet still have a relatively large woofer. Also, not all sub drivers are suitable for being used in a down-firing configuration. You can find how to do the math for suitability of down-firing drivers on Parts Express' site.

Ok. The Pluto looks interesting so I'll have more to read again, thanks.

Quote:

Originally Posted by ooheadsoo /img/forum/go_quote.gif Not to mention the school of thought that says the less re-radiation of sound from the baffle, the better the imaging.

I'll have to look up why that'd be better and in what way -- but I'll do so. Thanks for bringing it up.


Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif Have you considered taking a conventional design and then building a second, more exotic cabinet around it? Or does the unusual shape have to be functional, as well? Personally, I'm a big fan of the ProAc 2.5 clone (not perfect, but damn good for the price and effort) and while it's a simple box, there's little reason you couldn't dress up the exterior with cutouts and/or interesting stands. Either that, or you could pick up some exotic, figured veneer and do something interesting with a basic shape.

Yes, I actually have. And the more I think about it the more it seems like the most logical and wise plan, as a first speaker. Still, logic and wisdom aren't the most fun, are they?

Ok, I'm definitely getting ahead of myself here and I have no idea if the tube bass unit like this would work, or how I would tweak a crossover to make it sound anywhere near decent. But, I was playing around a bit again and this is what I came up with... Like I said, I'm getting ahead of myself. Still, it's nice to dream, right?

 

[pne]

theres no need to rip of the gallo reference speakers....

jk.

 

[digitalmind]

Quote:

Originally Posted by pne /img/forum/go_quote.gif theres no need to rip of the gallo reference speakers.... jk.

Ah, so that was the one. I knew I was making it look like something I'd seen before but I couldn't remember the name. Still, the Gallo is so much nicer.

So, back to the drawing board I go. I wonder what you get when you cross the Gallo with my evil brainchild.

Edit:
Here she is!
The Digitalmind "Gallo" Sexyspeaker!