Open Baffle musings

[mgrabow]

Re: Open Baffle musings

Very Interesting...

[Paul W]

Re: Open Baffle musings

Some magnet strength may be shunted through the ferrous strap between the poles...something to check.

[charlielaub]

Re: Open Baffle musings

How does it sound?

Fantastic! Great imaging. There is really a discernible benefit to the elimination of cabinet resonances in the upper bass and midrange.

Speaker is very good down to 100 Hz. I am running it full range, and the bass output down to about 40Hz is surprising. I have some subwoofers that I can pair this with, crossed over around 80-100 Hz.

I will be bringing this to the DIY meeting on the 20th of this month and am looking forward to hearing other people's opinions.

-Charlie

[greywarden]

How does it sound?

[charlielaub]

Re: Open Baffle musings

I've come up with REV 2 of the mounting for the midrange and tweeter after deciding that REV 1 needed to go on a diet. I came up with a new idea to try - just hang the two smaller drivers off of the magnet of the woofer (which is pretty beefy) since they are all located near each other in space. This required much less material and looks much cleaner visually. It took me a while to glue it up, but this seems like a better approach.

Marc - I was already contemplating whether I could use the strapping. It turns out that it is made of galvanized steel or something like that, which happens to be strongly attracted to the OD of the magnet. I formed two pieces that slip over the wooden ears that are at the 12-o'clock and 6-o'clock positions and help to hold everything in place.

The whole mounting system is removable since it could be easily snapped off during transport if it was permanently mounted. One nice perk is that now I can easily replace the particle board main baffle with whatever I want without having to make any changes to the mount for the M and T. I might pick up some butcherblock countertop material at IKEA and use that. It is pretty dead, about 1.5" thick, and stiff because of the butcherblock construction. It comes in a 24"W size, so I only need to cut it to length and then re-route the woofer mounting hole.

Here are a couple of pics of the current state of affairs:








-Charlie

[WernerM]

Re: Open Baffle musings

Charlie what about this to hold the tweeter dowel in place...

http://plumbing.hardwarestore.com/52-300-pipe-tubing-straps-and-hangers/galvanized-metal-strap-252346.aspx

You could wrap it all the way around the underside of the dowel, and apply glue to the top of the dowel for extra support...

[charlielaub]

Re: Open Baffle musings

Today I cut some wood and made a prototype of the rear "fin", now with support for the midrange and tweeter. This is testing out the concepts I had in mind for holding on to the drivers. So far I think that worked out OK, although I need to figure out a better way to hold the dowel rod onto which the tweeter is mounted to the fin, other than yet more duct tape!

Here are a couple of pics from various angles:








I need to make some mods to the fin. Let me illustrate with this doctored image of the rear view:



The fin is pretty weak above the point where the cutout for the woofer is made. The fin is just 5/8 particleboard, and you can shake the fin and get the top section to "wiggle" side to side. It needs to be stiffened. To do this I will glue on each side (in the brown area) some baseboard molding that I have left over from a recent project. The glue joints should stiffen up the fin quite a bit. Next I will add two braces between the fin and the main panel, as shown. This should provide additional stiffness to both.

Finally, I will probably trim off some of the top of fin at the back. The less that is sticking up visually the cleaner it will look, if you can call a particle board mess like this "clean". Then I will need to blast on some primer and some kind of thick paint. I haven't done this before with particleboard, but I don't have time to cut more baffles and make it nice since I need to start wrapping up so that I can bring these to the NorCal DIY Audio meeting in a couple of weeks.

Thoughts or suggestions on the fin stiffening, etc. is always welcome. Any thoughts on how to paint/finish the front of the main panel so that it looks OK are also definitely welcome.

-Charlie

[WernerM]

Re: Open Baffle musings

Thanks for the thoughts. Good luck and I hope it works out.

[charlielaub]

Re: Open Baffle musings

Being that I am still learning and still a newb, I have to ask, is there a possibility of the PVC drain cover you're using to mount the midrange causing reflections? Or would the effects from that be miniscule

The cover won't cause any reflection problems for the midrange, because it is smaller in diameter than the feature on the frame that the spider is mounted to. It's only slightly larger than the magnet, and so it is probably not going to present any problems for the other drivers, at least any more than the magnet itself would.

I don't anticipate any problems from these mounting approaches. Hopefully it will turn out that way.

-Charlie

[WernerM]

Re: Open Baffle musings

Being that I am still learning and still a newb, I have to ask, is there a possibility of the PVC drain cover you're using to mount the midrange causing reflections? Or would the effects from that be miniscule

[charlielaub]

Re: Open Baffle musings

Charlie, what about using a peice of MDF sideways, like the example of a baffleless design. IOW rotated on the Y axis 90 degrees from the front baffle, and cutout so that it wraps behind the drivers without touching the magnets, but has peices that come forward for mounting through the driver holes (It would be positioned similar to the way your clamp is now). Kind of like a T if viewed from the top... Or a spine on the back of the baffle...

Good call! That's what I have decided to do, more or less. I already have a perpendicular rear "fin" stabilizing the back of the panel, but it's short. I will just build another one that is tall enough so that I can mount the midrange and tweeter to it via their magnets. Hmmm, how to do it.... how to do... well, I had a couple of fuzzy ideas, but when I want to do my thinking I head to the hardware store and look around for ideas. I settled for the following scheme:

For the tweeter, I found a dowel that is about as wide as the magnet cup. When I got this home, I took some dull grey duct tape that I had lying around (1001 uses) and I wrapped first a layer with the sticky side outwards, then put a second layer on top of that with the sticky side inwards. I wrapped this tightly around the dowel as I made it but was able to slide it off when finished since the surface of the duct tape is pretty slick/smooth. Next I slid it over the magnet (a tight fit) and then I slid the whole thing back on to the dowel rod. Here's the result:






For the midrange, I considered using some ABS or PVC pipe and elbows but that seemed a bit more material than I wanted hanging off the top of my speaker. In the end I discovered that a slotted drain cover fit almost perfectly over the magnet structure from the back. My plan is to screw this on to the edge of the rear support fin through the slots. I will trim the fin so that it is at the right height and having a cutout for the Anarchy woofer. Then I will add some extra material along the edge where I need to screw in the midwoofer and then screw on the slotted drain cover. When I need to mount the midrange, I can just press it into the opening. Here's a view of the driver with the slotted cover over its magnet:




The dowel rod behind the tweeter will also mount to the fin somehow.

-Charlie

[WernerM]

Re: Open Baffle musings

Now, if I can only figure out how to mount the midrange and tweeter for real [/B]instead of jury rigging something, I will be able to bring these to the NC DIY AUDIO meeting. Any bright ideas on how to mount these drivers?


-Charlie

Charlie, what about using a peice of MDF sideways, like the example of a baffleless design. IOW rotated on the Y axis 90 degrees from the front baffle, and cutout so that it wraps behind the drivers without touching the magnets, but has peices that come forward for mounting through the driver holes (It would be positioned similar to the way your clamp is now). Kind of like a T if viewed from the top... Or a spine on the back of the baffle...

like this

[charlielaub]

Re: Open Baffle musings

I managed to put together and connect the second speaker, and enjoyed a few hours last night doing some listening. These really sound great! They are definitely not too bright in my room.

Now, if I can only figure out how to mount the midrange and tweeter for real instead of jury rigging something, I will be able to bring these to the NC DIY AUDIO meeting. Any bright ideas on how to mount these drivers?




-Charlie

[Face]

Re: Open Baffle musings

Well, brightness is in the eye (or ear!) of the beholder. If they sound OK to you, then that's what matters!

It depends on the room too. If his room is on the dead side, IMO, those wouldn't sound bright at all.

[fjhuerta]

Re: Open Baffle musings

Well, brightness is in the eye (or ear!) of the beholder. If they sound OK to you, then that's what matters!