Speaker design myths revealed

PHY KM 30 SAG.

I have owned Carolina Audio JTM speakers for about a year now. These speakers use the Jordan driver in a wide baffle transmission line enclosure. I have owned many other speakers, including five other brands at present. So far, compared with these other speakers I have found this implementation of the Jordan driver to be the best all-around speaker for typical rooms I have yet owned. As Sean pointed out, the wide baffle helps with the bass. With the JTMs bass is very accurate and satisfying without a sub. They are easier to place than any speaker I have owned- much less sensitive to side and rear wall distances (perhaps the limited off-axis dispersion of single driver speakers helps with this as well- this is a liability as well). The design does a good job of highlighting the strengths of this 4'' Jordan driver, while achieving in-room bass comparable to many floorstanders out there.

The Jordan drivers themselves measure flatter than most other single-drivers (see the Nelson Pass measurements on 6moons comparing different single drivers), and when used in this kind of enclosuse, can deliver fairly flat in-room response without a lot of tweaking. Considering how good these drivers are, surprising there aren't more speakers out there using them. Seems like most interest in single drivers is for use with low power SETs. A shame since this kind of speaker works well with more common solid state and tube audiophile gear.

Wow, Fiddler. I expect you're trying out Phy's recommended open baffle with the piano hinges on the side flaps... Planning to use a tweet???

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.

Fiddler, you can calculate the size of the needed baffle by using the quarter wave formula.

It depends on how deep in the bass you want these things to produce.

Pick a frequency above the F3(resonant freq) of the driver, and deep enough into the bass region to satisfy you.

For example, if you want 32Hz to be able to be reproduced by the system(assuming the driver goes that low), you will need a baffle that is at least 1/4 wavelength of the (32')32Hz wavelength, which would be 8 feet across. If you want to get only to 64Hz(16' wavelength), then you'd only need a baffle that is 4 feet across. If you want to "split the difference, and get 48Hz, then you could use a baffle that is 6 feet across.

All frequencies above the frequency determined by the baffle board will be reinforced by the boundary effects of the baffle board, and will not be subject(much) to the "wrap-around" cancellation effects that will adversely affect the frequencies below the capability of the baffle board to handle.

While it is a matter of discussion whether to mount the driver in the center of the baffle board, due to the relative "smoothness" of the response curve, mounting it in the center would give the best result in getting to the deepest bass for a given size baffle board.

The determining factor(in size) for the baffle board's effectiveness is based upon the smallest outside dimension that goes across the driver. So the smallest outside dimension will dictate your reinforcement frequency, and any larger dimensions will have little effect, but they may do a little. Thus, a circle shape will be the minimum sized shape that you could use, but it is more difficult to stand up and use. A square baffle is typical, but only the largest diameter circle that you can draw around the driver will be doing the work, and the corners doing very little.

Remember, if you make it tall and narrow, you are losing your effectiveness, so make it just as wide as it is tall.

Having the piano hinges, and angling the sides backwards to a small degree will do just as well, and helps to make the baffle more visually acceptable. It also keeps the edges out of the diffraction plane.

The best thing would be to make the whole baffle shape like one of those "snow saucers". It would allow the driver to be placed at the foremost part(center), and have uniform shallow radius sloping backward all the way around, for most smooth response and minimum diffraction. But it would need to be big, and I've never seen a 6 foot snow saucer!

For the easiest construction, flat and square works.