DIY Open Baffle Full Range Speakers from Wal-Mart . . .

[Jezz-the-Fezz]

I know this'll probably sound a little daft at first, but has anyone thought about doing an isobaric/baffle combo?

[DMD]

Originally posted by Scottmoose

To give one example, a 26" wide baffle will begin to run into baffle-step issues (-3db point) at around 175Hz I believe.

Hey, howdja get that? I was just putting together some Wal-Mart open baffles myself for breaking in and tweaking my Fostex drivers, and I was a bit confused with the roll-off frequency formulae and charts I found on a forum search. For example, I don't think I grok this calculation that Dave posted last year, and I was thinking of posting and asking if he or someone else might like to spell it out for me:

Originally posted by planet10

There are 3 or 4 different of these floating around, including one i made based on Olsen. It seems that the most accurate results flow out of Linkwitzes work and, IIRC, this boils down in its simplest form to 0.17 x f(bafflewidth) for the roll-off point.

dave

...also this later post:

Originally posted by planet10

.... There was quite a long discussion here on the forum, and the 0.17 figure of merit seemed to best correspond with measured data (i actually plotted some data provided). A 1 m wide baffle should get you to 58 Hz.

This is way better than the 170 Hz or so that Olsen predicts (see attached chart).

dave

Here is the chart that Dave attached (it would give about a 39 inch baffle width for 175Hz).

Anyway, mrpopgun, this page and the one or two following, which I got the above quotes from, have plenty of discussion and potential clarification/confusion that you might have some fun with.

Everyone be good and take care,
Don

[el`Ol]

I am using the Ciare CH250 in the center of 100x55cm baffles, originally with 17.5 cm side walls. I extended the side walls to 45cm to get the same acoustic short circuit in both directions and this was essential to get some bass. Rolloff should start at 85Hz now and that`s what it does. According to the fostex site the side walls shouldn`t be too long to avoid pipe sound. An alternative is to make the side walls not parallel, like in these examples:

http://www.auditorium23.de/PHY/Plaene2.html

Or build plain baffles that are partly made of glass to avoid killing the room, The most popular variant in this forum.

[el`Ol]

This may also be a solution for some rooms, I once tried it with a small Qts 1.5 driver and the 60° needed to listen on axis also sonically seemed to be the optimum.

[sumacSK]

Hi el`Ol

Could you please write more about your Ciare HX201. It seems to be very nice new driver and there is not much info about it around.

Thanks Martin

[el`Ol]

Hello Martin!

I am going to use the HX201 as omnidirectionals, looking to the ceiling in a 40l-BR without correction, reflector or supertweeter. Tests in sealed enclosured showed that this definitely works, except bass, but the simu looks fine. I have suggested to try this with the B200, because it has a similar rise in frequency response, but in a thread about omnidirectionals in the loudspeaker forum one person said he is not so pleased with that and is using the B200 30° tilted with crossover and supertweeters. I tried the 30° tilt with the HX201, sounds very shouting and the omni-typical spacial image is gone. There is probably some difference between the B200 and the HX201. I couldn`t imagine to use the HX201 on axis without correction, like many people do with the Visaton.

Greets, Oliver

[Rudolf]

Originally posted by mrpopgun
I always see OB and references to the width of the baffle. What about the height? I would think that both have to be taken into account, but have no idea what the relationship should be.

In fact it´s not so much the width of the baffle that defines it´s response but its area. Even more important is the distance from floor to driver. The best tool available to learn more about the interaction of T/S parameters, baffle dimensions and driver position is xlbaffle.xls courtesy of Kuei Yang Wang:
http://baseportal.de/cgi-bin/basepor...&cmd=all&Id=15

[el`Ol]

Some people from the Saba vintage scene calculate with length of the short-circuit = quarter of the wave length for the special case of a plain round baffle. In my case the vertical short circuit is one meter and vertical one is around 1.1 meter, so it comes pretty close to the ideal and rolloff should start at 85Hz or 78Hz respectively. But that`s too close to discriminate, because I don`t have a micro and do subjective tests with a function generator.

[planet10]

The 0.17 figure of merit doesn't take into account the driver's Q (ie assumes a Q of 0.7).

Thorsten's (Kuei Yang Wang) SS does.... particularily of use to take max advantage of a high Q driver such as vintage Sabas or Isophons (and many others) -- the high Q driver needs a narrower baffle of just the right dimension that the dipole cancellation interacts with the rising response of the driver to get flat down as far as possible.

dave

(PS the SS is also on my site)

[gilbodavid]

Hello all. I've been reading threads for three days, and am excited about visiton B200's. Re the baffle, a guy who seemed to know his stuff on the gravity well of a dark star thread on audiocircle was saying that having a 10-14" front baffle that's not too high and wider at the bottom, and having two 8" ish wings on either side, swept back at 60 degrees and not hinged, with an upwardlysloped "roof" on it, with the whole thing riggidly held by crossmembers, would behave like a 48" wide flat baffle in his experience, and keep the openess. Anyone here up with his imput, because if it works, its a hell of a smaller object! I hope I've got what he said accurately. Thanks