Irregular/Curved shaped baffle - how to design? - diyAudio
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Old 19th September 2012, 04:38 AM   #1
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Default Irregular/Curved shaped baffle - how to design?

Hello,
I have a question that may require a simple answer but I would like to know. I have been looking at designing speakers using a "without measurements" guide and calculators online.

From what I've seen the box and baffle step corrections are all for rectangular shaped boxes but I have not been able to understand/see how one would design an irregular shaped speaker. F

or example this version of Tarkus. How would I go about designing an "irregular" shape like that? Do I do my calculations by using the rectangular box calculations and just make sure that the surface area (for the baffle) and the internal volume are the same?

Thanks for your help
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Old 19th September 2012, 09:59 PM   #2
tvrgeek is offline tvrgeek  United States
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"Without measurements" is going to bite you. Measurements make life easier. You ear is always still the last say. ( it is a measuring device) Anyway, the very most important thing about the baffel is to reduce edge diffraction. A radius of 3/4 inch is the minimum I will accept any more. It happens to be the largest bit I feel safe spinning in my table. Anyway, the baffle dimensions then effect the pole and zero of the baffle step which you will want address. It is not the surface area of the baffle, it is the distance from the sound sources to the edge that is important. Might head over to True Audio and read their piece on diffraction. Then get a copy of The Edge to model various baffles. It assumes a sharp edge, but you can learn a lot about position on the baffle. You actually have to measure to see the real results.

You are wondering how to determine the volume of an irregular object? Three ways. Horrible complex math, estimate by calculating an average close enough shape, and three , peanuts.

"Design without measurements" Well, blind people can paint, but I bet I would not like their paintings.
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Old 19th September 2012, 10:10 PM   #3
tvrgeek is offline tvrgeek  United States
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Just another thought. I have designed and built dozens of systems over about 35 years. I have not graduated from square boxes as there is still more I have not yet learned; both in acoustics and in woodworking skills. I can make a square box sound darn good, if I say so myself. You may have heard the old adage about learning to walk before you run. My preference, but I go for sound first and aesthetics second. Everyone has their priorities.
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Old 20th September 2012, 04:41 AM   #4
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tvrgeek, thanks for the reply!!!

I've already built my first speakers (although still not painted lol) and they sound pretty amazing. I built the ZX Spectrum by Paul Carmody

Although in his original design he calls for 90degree edges i gave mine a 15deg chamfer on the baffle and lined the inside with 1" Acoustic (egg carton) foam.... and the speakers sound phenomenal.

I do like aesthetics tho and I would like to build a pair of desktop 2-way speakers and I have some really nice design ideas brewing in my head.

I did look up how to do measurements and it looks like I can do it for spending about $100 on a calibrated mic and mic-preamp. I already have an X-fi sound card and a tripath amp I bought cheaply from PE.


I guess I'll have to do measurements if I want to be a bit more serious.

But if I am do do an "irregular" shaped speaker with a funky baffle. Say my goals are a 30Hz-20kHz 3-way rear/front port design.
In the initial design stages, before measurement, can I estimate my frequency response, port size and internal volume (let say I can measure the internal volume of the irregular shape) for my parameters? Do I have to worry about baffle diffraction and baffle correction in the initial (pre-building the enclosure and pre-measurement), design stages of the speaker? Than after I build the enclosures I will do a frequency response measurement and that will take care of my baffle correction and crossover design?

In other words, do I have to worry about the baffle correction and crossover calculation until I do frequency measurements after making the enclosure?


thanks
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Old 20th September 2012, 09:17 AM   #5
tvrgeek is offline tvrgeek  United States
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I think you have come to the conclusion so many miss. You have to prototype. All the simulation is very useful, and it can get you pretty close, but before spending big bucks on fancy woodwork, you need to prototype, measure and listen. Box tuning won't be quite right, crossovers are never quite right, and the big one, your room, is not part of the model but it is critical to the end result. Crossovers are a lot easier to play with if they are on the floor behind the speaker so you can jumper in and out parts.

The baffle behind the woofer should be radiused, but it is the four baffle edges of the box that are the most critical. In my last pair, I was surprised to find further improvements from all 12 edges being eased. A lot of speakers use large angled for facets around the baffle. Easier to put wood vernier on. My small scale testing suggests it is better than 90 degrees, but not as good as a big radius.
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Old 21st September 2012, 03:21 AM   #6
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thanks for the info.

I think I will go with modeling/designing for a rectangular enclosure with rounded or chamfered baffle edges and than when the box is build i will measure the FR and finalize the crossover.

tvrgeek, do you have pics or a build thread of your projects?
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