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Multi-Way Conventional loudspeakers with crossovers

A few simple questions
A few simple questions
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Old 18th October 2011, 02:55 AM   #1
gray5596 is offline gray5596  United States
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Default A few simple questions

I was asked by a high school student for assistance to build some home speakers for a school project. He is a good kid with some woodworking abilities, but I was hesitant for 2 reasons:

1. He seemed convinced that he could buy some raw speakers and cross-overs on-line, throw them in a box and it would sound great. (Oh to be young and optimistic again)
2. I have had success building amps but the speakers I built many years ago sounded less than desirable and left a bad taste in my mouth. Wanting to spare him the disappointment of building some crappy sounding speakers caused me to think about a pair of Atlas FAP82T speakers left over from a recent job and how they might be a perfect donor for his project. They are a two way tuned port speaker in a metal enclosure used for PA applications, 8 woofer and a 1 tweeter. http://www.parts-express.com/pdf/242-808s.pdf

My thought was to build a MDF cabinet of approximately the same cubic inches as the metal enclosure and use the same speakers, crossover and port diameter. However, having no experience building a good sounding speaker, I had a few questions.

How critical is the port location?

Because the original case is metal and cylinder shaped, what effect will a rectangular wood cabinet have on the sound? In other words, should we make the wood case smaller, larger or same size?

Keep in mind that his primary interest is a good looking cabinet, so I am merely interested in getting these speakers to sound reasonable. Later if he enjoys this project, I plan to help him build some more serious speakers.

Thanks for any advice you might give.
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Old 18th October 2011, 03:27 AM   #2
AllenB is offline AllenB  Australia
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A few simple questions
These speakers were designed to be mounted flush in a ceiling. Although I have no idea how well they achieved their objective, in theory mounting them on a box would leave them somewhat bare with a crossover change needed at the least. I suppose failing other options you could use as wide a frontage as didn't look too out of place, and adjust the tweeter level later if it didn't sound right. Leave the port and internal volume the same.
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Old 18th October 2011, 04:58 AM   #3
gray5596 is offline gray5596  United States
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Allen, thanks.

Yes, they are designed to be ceiling mounted, but I picked the FAP82s because they had a lower dispersion rate (100 degrees) than most ceiling mounted speakers. We put a pair of these on my bench, forward facing and about 8 feet apart. We stood back about 10-12 feet, played various music thru them and they sounded remarkably well. Again I realize these speakers have some limitations, but he heard the 8" woofer and was convinced that was what he wanted to use. (Something about young men and booming bass)
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Old 18th October 2011, 05:10 AM   #4
AllenB is offline AllenB  Australia
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A few simple questions
And dispersion. This year I am using 15" midrange drivers for this reason. You'll probably prefer the wooden cabinets. They may be a little more solid and less resonant, and an improvement on the round frontage of the units currently when freestanding. You should also add a little stuffing to the box.
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Old 18th October 2011, 02:53 PM   #5
sreten is offline sreten  United Kingdom
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Location: Brighton UK

You will have some "hifi" issues using that speaker in a normal
box but it will work in a fashion, though not that optimally,
as its designed for flush mounting. In a box you will get
weak bass due to the "baffle step" a box introduces.

Something like Zaph|Audio - Bargain Aluminum MTM
would be in a entirely different quality class. The
floorstanding version has very good bass extension.

rgds, sreten.

(see if nothing else, the excellent FAQs)
FRD Consortium tools guide
RJB Audio Projects
Jay's DIY Loudspeaker Projects
Speaker Design Works
HTGuide Forum - A Guide to HTguide.com Completed Speaker Designs.
Humble Homemade Hifi
Quarter Wavelength Loudspeaker Design
The Frugal-Horns Site -- High Performance, Low Cost DIY Horn Designs
Linkwitz Lab - Loudspeaker Design
Music and Design

Great free SPICE Emulator : SPICE-Based Analog Simulation Program - TINA-TI - TI Tool Folder
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Old 19th October 2011, 12:54 AM   #6
gray5596 is offline gray5596  United States
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Screten, thanks for the links. If he enjoys the 1st project, these links will give us many choices for future projects.
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