Speaker design myths revealed

PHY KM 30 SAG.

Cdc, I am currently in the process of putting together an "open baffle" design. If you are interested, I will let you know my impressions when the drivers are broken in.

No Gregm, no piano hinges.

I am going to experiment with plywood baffles until I find the size of baffle that seems to be optimum and then I will have the baffles made out of Lexan if I like the results of the plywood. It will be a flat baffle with no hinges. Others have had great success with this design.

I have a friend that has just done this and he and another friend said the results have been nothing short of phenomenal. But he used piano hinges, but many others haven't. The open-baffle PHY's may suck in my room, but time will tell.

No additional tweet. The PHY KM 30 SAG has a time-aligned piezo-electric tweet that goes to 30kHZ.

They will require subs for sure.

From the experience of numerous other people, the baffle does not have to be very large to be effective if you aren't concerned about low bass frequencies. 50-60HZ is about what one could expect with a small baffle (see link below) and the subs come in where the bass begins to roll-off determined by the in-room response of the baffle.

Here is a link with several pictures:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=19883&perpage=10&highlight=lexan&pagenumber=7

And another:

http://www.dietiker-humbel.ch/micromag.htm

There are many more pics and threads elsewhere online about OB, but this is an example of the type of OB I am experimenting with.

I know jack**** about all this, but I trust both my friends and their ears. They both currently have really high-end systems and have been through several other high-end systems. My friend said his OB PHYs wiped the floor with his previous $$K speakers and all who have heard his OB's have been very impressed.

"this info is mostly for jordans only or other OB drivers, OB drivers need much help to produce any kind of range.Other drivers wouldnt perform well in theses type of designs."

Johnk, if you are referring to the PHY driver, then sorry to disagree. Qt primarily determines whether a driver is suitable in OBs.

The manufacturer recommends the PHY KM 30 SAG for open baffle designs. For OBs, one just has to accept a compromise between bass response vs. baffle size. With subs, baffle size options can more real-world.

Thanks Twl, I am starting with a baffle about twice that size (but rectangular, not square) with the driver mounted off-center. In my earlier post, when I said smaller baffles, I didn't mean "reeeeal" small, I just meant in the four foot range with a plan to use subs crossed-over where the PHY rolls off.

Thanks for the info Tom.

4' x 29 1/2" is what I am experimenting with using Birch ply, but the drivers are brand new and they need to be broken in. When I have about 250 hrs. on them I will do some in-room measurements to see exactly what type of bass response I am getting.

When I actually decide on the final dimensions of the baffle, I will be using .5 inch Lexan (stiff). I don't think it will flex!

Also I am going to try a unique baffle plan. I have an idea to make a wooden baffle like the Maple one pictured in the first link I posted. My baffle will be made from Koa, a beautiful wood native to Hawaii. But here's the unique part. Mounted between the driver and the wooden baffle, I am going to place a donut of 1/2" Lexan about 1/8" larger than the outside edge of the driver. So sandwiched between the driver and the Koa baffle, will be a 1/2" thick, Lexan donut. The big 4' x 29 1/2" Lexan baffle will have a hole cut about 1/16 larger than the Lexan "donut". (BTW, the Koa baffle will be 1/2" wider than the Lexan baffle around the sides and top so the 1/16" gap between the large Lexan baffle and the Lexan donut will have a backing.

When I am ready to listen, I can take the big Lexan baffles out of our coat closet, lean them against the smaller, wooden Koa baffle/driver, slipping the hole in the big baffles over the Lexan donut & driver for a really nice fit. This will be a removable baffle that is completely flush from the driver to the edge of the baffle. I suspect this may also reduce some resonance of the large Lexan baffle since there will be a 1/16 gap between the Lexan and the Lexan donut (which is sandwiched between the driver & Koa baffle.)

I plan on using an easily adjustable spike system underneath the "base" of the Koa baffle/driver to slightly raise or lower the Koa baffle/driver to perfectly fit the hole in the large Lexan baffles. The up & down adjustment will be from the top side of the "base" for convenience.

If everything was sitting directly on the hardwood floor, raising or lowering the Koa baffle/driver wouldn't be necessary, but since we have a 13 x 20 Persian rug (plus pad) which the speakers will be sitting on, there will be some settling of the Lexan baffle, as well as with the Koa baffle/driver.

When I am not listening, it will take less than a minute to remove the large Lexan baffles and place them in the closet for WAF. All that will be left in the room will be a rather small and neat 36" high x 15" wide Koa baffle/driver. (Plus subs)

To my knowledge this idea hasn't been tried, but I am pretty confident it will work pretty well (I mean the removable baffle). I simply need to break the drivers in and experiment with baffle size.

Thanks for your interest.

PS - and I apologize if my description is not clear, but it really is rather simple, just a little hard to describe on paper. If you look at the pic of the OB in the first link I posted with maple baffles it may help to visualize the removable baffle.

Thanks for the tip, Gregm. That is terrific food for thought! Shouldn't be very hard to experiment with.