Tips for building open baffle?

irishpatrick33 · « **on:** 19 Feb 2009, 12:52 pm »

I realize much about open baffles are debated. And I realize part of the fun is figuring out what works best for you.

I am going to build some open baffles. I probably will try a few different designs. I will be using a single B200 in each open baffle.

So I am wondering about some good tips. I have already read that baffle width should be no larger than 2.2X the diameter of the cone. Any other tips? I saw something else mentioned about decoupling the speaker from the baffle, but they didn't go into much detail.

mcgsxr · « **Reply #1 on:** 19 Feb 2009, 01:47 pm »

Welcome to AC, and to the OB circle, AND to b200 ownership!

The best advice I can give, is to experiment with cheap material first, prior to committing to a shape with more expensive woods, finishes etc. You might play around with adding wings too. Lots of opinion about wings, but your ears are the right tool to guide you.

Many believe that decoupling can be achieved by mounting the driver from the rear with clips, rather than screwing it directly to the baffle from the front.

For the record, I have just bolted them to the baffle (through bolts) and have lived with it for years.

I later added a sub per baffle, but should have taken the advice to mount those separately - they do vibrate the baffle considerably, and do muddy the mids. My next implementation will have the woofers firing through, but not attached to, the main baffle.

irishpatrick33 · « **Reply #2 on:** 20 Feb 2009, 02:58 am »

Thanks for the tips.

Could you explain the clipping on driver part? I have never seen this.

irishpatrick33 · « **Reply #3 on:** 23 Feb 2009, 02:45 pm »

I'll describe a bit of what I am doing.

This will be a FR open baffle. I plan on the baffle being a circle.

I have two worries. I wonder what the best solution for the edge of the baffle is. Is it a square edge? One side rounded? Or both sides rounded? Sloped?

I plan on mounting through the baffle, as opposed to pressed up against it. So I wonder whether the inside edge of the mounting hole should also be square? Rounded? Sloped?

Rudolf · « **Reply #4 on:** 23 Feb 2009, 03:44 pm »

Quote from: irishpatrick33 on 23 Feb 2009, 02:45 pm

This will be a FR open baffle. I plan on the baffle being a circle.

Don´t tell me you are going to mount that fullrange in the center of that circle.

Rudolf

richidoo · « **Reply #5 on:** 23 Feb 2009, 04:17 pm »

If you mount it in the center, the step response of the baffle will cause the volume to fall off at one frequency. If you offset the driver, then the distance to an edge varies in all directions, thus varying the dropoff frequency, and making a smoother transition through the baffle step. With a circular baffle, no matter where you put the driver, there will always be two directions with equal distance, but that's OK, better than every direction is the same distance to the edge. Another approach is to use a square baffle to maximize the bass response, and place the driver so that the distance normal to each edge increase by a fixed amount on each edge.... So the driver is 3" from left edge, 6 inches from top, 9 inches from right edge, 12 inches from bottom. The 3" interval can be any number, or it can vary. Use your imagination... But a circle probably looks the nicest anyway..

The baffle step can also be corrected electronically with a filter which will make your frequency response flatter through the transition. http://www.trueaudio.com/st_diff1.htm But that will cost you some efficiency, making the speaker sound only half as loud above the step frequency.

Edges should be fully rounded over because a sharper edge causes diffraction at higher frequencies. Even the rounded over edge will diffract at a lower frequency, but less frequencies are affected when it is rounded. Spatial cues dependent on high frequency information will sound better.

To get as much bass from your full range driver, you will want the largest possible baffle. But a large baffle messes up the staging because sound reflects between the front wall and the rear of the baffles. Cover the baffles in sound absorbing material to avoid this.

"Clipping on a driver" is not an official term, but what he's talking about is mounting the driver in the baffle hole so that it is not touching the baffle. It is held in place from the magnet at the rear or some other creative arrangement. This prevents the vibrations from the driver frame from getting into the baffle, where they will be amplified and distort the sound. Another approach to this problem is making the baffle from high mass material like granite or thick maple which will still vibrate, but at a lower amplitude. Two pieces of 3/4 MDF laminated together with [urlhttp://www.greengluecompany.com/]greenglue[/url] will work good, because it damps vibrations. Then you get a thicker edge to roundover too. Bending the baffle material slightly stiffens it in the direction of the bend, reducing vibration in that direction. There are many possibilities, read through past threads on this circle for ideas.

Software for designing open baffle speakers: http://quarter-wave.com/ Good articles there too.

ultrachrome · « **Reply #6 on:** 23 Feb 2009, 05:27 pm »

Here's some info on driver mounting: http://www.linkwitzlab.com/frontiers_2.htm#N

I'd recommend doing most of your prototyping with Edge. http://www.tolvan.com/edge/. Much more educational and time effective than making test baffles especially if you lack measurement equipment. Like others are saying, avoid round and/or too wide. Tapered baffles are the new black.

I just spent 3 days constructing a pile of sawdust for my two test baffles.

What are you using to EQ the dipole artifacts?

panomaniac · « **Reply #7 on:** 23 Feb 2009, 07:51 pm »

Quote from: ultrachrome on 23 Feb 2009, 05:27 pm

I just spent 3 days constructing a pile of sawdust for my two test baffles.

An interesting way of looking at it.

Rudolf · « **Reply #8 on:** 23 Feb 2009, 09:42 pm »

Quote from: richidoo on 23 Feb 2009, 04:17 pm

To get as much bass from your full range driver, you will want the largest possible baffle. But a large baffle messes up the staging because sound reflects between the front wall and the rear of the baffles. Cover the baffles in sound absorbing material to avoid this.

richidoo,
you are giving some good advice in this thread, but I strongly believe that the above is plain wrong. I´ve heard it before from others. So I feel I should explain my objection:
Sound is not playing pool billard. It´s not about sound rays being reflected time and again between mirror walls. Sound is radiated in spheres. And from the "balloon" of sound emerging from the rear side of the baffle to the front wall there will be only a very small amount (the area around the first contact), that is reflected directly to the baffle. More than 90 % of the radiation will be reflected into the room without meeting the rear of the baffle again.
It is true that a large (compared to driver size) baffle will mess up the staging. But this is the result of heavy edge diffraction with uncontrolled directivity which increases with increasing width of the baffle.

irishpatrick33 · « **Reply #9 on:** 24 Feb 2009, 08:26 am »

Thanks for the tips!

Rounded edges, mount offcenter, and find a way to decouple the driver.

I'll try some of those programs. But a lot of that stuff goes over my head.

There's more to what I am doing. But I would rather wait until it's a completed product before I show it. nothing real elaborate, more likely a bit off the beaten path.

The rounded edges part really saves me a lot of time. Otherwise I would have had to try every possible mock up to determine the best. I am grateful somebody else did the legwork for me.

-Richard- · « **Reply #10 on:** 1 Mar 2009, 03:32 am »

Hi irishpatrick33 ~

I used one B200's in a simple flat baffle for almost 2 years.

I experimented with different separate "integration" bass augmentation methods. For example, I used dedicated enclosed bass drivers (woofers) with their own internal SS amp with variable crossover points. I also used another pair of wide-range box speakers that intrinsically had a good bass response, powered by a dedicated tube amplifier with tone controls which also allowed me to "dial-in" a workable cross-over point.

Both methods had interesting results. Aesthetically, I did not like having to use separate speakers... too much "stuff" visually to look at... and the sound integration did not thrill me... although it did work.

For a long time I just powered the single B200's with a tube integrated amplifier with tone controls... using the bass tone control to flesh out the lower frequencies... and it did sound quite nice... I could live with it (and did) without feeling I was being deprived.

So here is a simple experiment... once you have your baffles finished and playing (remember, burn-in time for the B200's... which will give you a more "relaxed" sound... begins after perhaps 200 hours) invite a friend over who has a tube amplifier with tone controls... and try the bass tone control to see if it fleshes out the bass in a satisfying way.

I am currently using 1 Alpha 15A per baffle with the B200's and a very nicely designed EL 84 tube amp with tone controls... a completely modified Heathkit... and the sound is quite convincing.

Please keep us informed of your experiences.

Warmest Regards ~ Richard