My first OB speakers...

I found some very impressive full range drivers in a set of Pioneer CS-51 speakers. So I made these speakers with what I had lying around. It was fun, they sound pretty good. Only one tweeter worked, so I used it, but I think I like the way the one without the tweeter sounds better. Maybe the caps are so old that they arr not functioning properly.

Nice. The FR units are monsters.

Dang, those magnets look like they should be containers for holding radioactive material:
"This is heavy duty, Doc. This is great. Uh, does it run, like, on regular unleaded gasoline? "
"Unfortunately no, it requires something with a little more kick - plutonium. "

Seriously though, those speakers look like fun. I've never heard any open baffles (really should). Perhaps with those full-rangers, you might want to look into getting some supertweeters.

...... So I made these speakers with what I had lying around. .....

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I've thought about using OSB, and it's not normally discussed by speaker cabinet building people. What are your thoughts, now that you've actually used it in an audio application?

thought about using OSB

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I read somewhere that luthiers never use OSB, so speaker builders shouldn't either. Or something like that. And since this is my first project, I don't know if good quality plywood might be an improvement. The panels really resonate, I don't know if that's good or bad. They're heavy and coupled to the floor well, so they don't rattle, but you can really feel the vibrations when you put your hand on them.

FoolForARadio said:

I read somewhere that luthiers never use OSB, so speaker builders shouldn't either. Or something like that.

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I wouldn't be too worried about what a luthier would use. I doubt they are too keen on using MDF, and it gets used for speaker cabinets all the time. For a cabinet, we want something that is acoustically dead, and structurally rigid, since we don't want the cabinet to contribute it's own sound.

And since this is my first project, I don't know if good quality plywood might be an improvement. The panels really resonate, I don't know if that's good or bad. They're heavy and coupled to the floor well, so they don't rattle, but you can really feel the vibrations when you put your hand on them.

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Looks like we are at about the same spot then...... I don't have enough working expereince cabinet building to know, either. I'm hoping OSB would be a nice compromise between MDF and Plywood. MDF has a vey even density, but it isn't very rigid and it's heavy. Plywood is much more rigid, has acceptable density uniformity and is lighter than MDF.

FoolForARadio said:

I read somewhere that luthiers never use OSB, so speaker builders shouldn't either. Or something like that. .

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I've heard that quote too, and I have to wonder who ever came up with it. Musical instruments are made to resonate - that's what creates their tone. Speakers should not resonate. If they do, then they are producing a sound which is not in the original recording. Speaker resonance = distortion of the original source material.

Mark

I've done a little online research now, and it seems that OSB is rated the same as Plywood for architectural construction purposes..... code actually doesn't differentiate between the two.

Let me see of I can find some of the articles I read again......

Here we go:

http://www.umass.edu/bmatwt/publications/articles/osb_vs_plywood.html

The above article states that OSB is about twice as strong as plywood in shear, and that OSB is about 7% less stiff that plywood...... that's got to be better than MDF.

All in all it seems that OSB is quite a controversial material. I didn't realize that it's only been around snce the late 70's. The house I grew up in was built in 80/81 and it had OSB roof decking..... at least over the garage. I had no idea the house was built with any new (for the time) technology.

I have an Altec Lansing cabinet that looks like it's a OSB type material. It was built in the 90's. They used it because it was available with a woodgrain vinyl coating that could be stained or painted.

I think it's something I'd like to try.

I have been asked to post details of my open baffle project.

Well my journey started very cheap. I took some nice 8" drivers salvaged by someone else from a philco solid state console and some free scraps of particle board and made my ghetto OB system as a proof of concept.



I was absolutely blown away by the results so I stuck a dome tweeter on top and supplemented with an 8" AR sub and used it as my main system for quite some time. There is a small top plate and unequal side plates on the baffle.

As you can see the Spousal Acceptance Factor is quite low on those so I began work on a more polite system.

I had some old Radio Shack 5 1/4" FR drivers which appear to be Foster OEMs so I decided to use those as the basis of the project.



The silver ring is just an adaptor used to mount the driver in a car. These were of course removed before use. These drivers start rolling off at about 200Hz (most likely due to a stiff surround) but that was OK as I planned to use a helper woofer anyway.

Being a cheapskate I chose to use a budget 10" woofer from Parts Express. The rather high Q is appropriate to a small baffle system such as this one.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-325

My design was intended to mitigate one of the downsides to an OB system. For an OB to perform to the utmost it needs about 3' of breathing room behind the speakers. So to get around this I made them into something that someone would want to have out in the room a bit. They are little knick-knack tables on which one can place flower arrangements, pictures or whatever.

So step one is to make baffles using some junk wood from an organ console that I parted out. It sounded pretty good so I began building the rest of the table. using pine 1x6 boards that I picked up at Lowes.



I use a cheapo version of bi-amping currently that takes advantage of the FR driver's natural rolloff. I daisy chain the main receiver, via. the headphone output, to another receiver with the bass turned all the way up and the treble all the way down on the second receiver. It works better than you might think but I am at work on an amp for the FR that will include an active crossover for the woofers and the subwoofer.

I found a pre-made pine table top at Lowes and affixed this to the top and added a base plate. I will add small feet later.



The completed speakers received a couple of coats of Minwax stain and several layers of Teak Oil. Being my first woodworking project of substance I made some mistakes in the process but the increase in SAF is significant.



You will notice the "second fireplace" behind the left speaker. This is a subwoofer I built to replace the 8" AR sub that I had been using. I modified the plate amp from the AR slightly to decrease the low frequency rolloff that was built in to protect the little 8" driver. It now has significant output to below 20Hz.

I took the wooden parts of a defective electric fireplace that I picked up for $5 and installed a closeout 12" paper cone woofer from Parts Express (no longer available) that had perfect parameters for the 5 or 6 cubic foot sealed enclosure that results. It is a vast improvement from the AR.



I am pleased with the results so far and am sure that a proper crossover will make it even better. Due to the simplicity of the system upgrading the FR drivers to something better is easily done.

Some day an architectural tapped horn should replace the fireplace sub.

Hope this doesn't qualify as too much information.

mike

My apologies I meant to post my response here...

http://www.audiokarma.org/forums/showthread.php?t=206082

I am not sure what happened.

mike

nice!

Those baffles look a lot nicer than I would have assumed...... They almost have a artistic quality to them. Give them a splash of stain, a little poly... then case them, I bet they would end up looking pretty nice.

How do they sound?