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Old 27th August 2013, 02:25 AM   #1
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Lightbulb thesis project: in-ceiling loudspeaker: survey

I'm an industrial engineering student and as my thesis project in product design and development I will present this semester a design for an in-ceiling loudspeaker for commercial application. Right now I'm at a phase where I must choose between several proposals or come up with more that deal with typical problems in PA systems that use in-ceiling loudspeakers. I could use everyone's opinion around here. Just so you know, a little background: my knowledge on loudspeakers is very DIY. I've been building cabinets and putting systems together since I was 11. I use some basic software for designing cabinets and crossovers and one of my aims is to learn more about speaker measurement techniques with my thesis project. I also need to achieve a system-level design together with a "frankenstein" prototype by the end of the project, in order to validate my thesis.

Here are five proposals to which it has come down to. You can rank them on the basis of commercial feasibility. More proposals are welcome. These are just short descriptions. If you want the longer descriptions (more technical) or book references send me a message.

A. An in-ceiling loudspeaker for commercial use that limits leakage of low-frequency sound into building structures by the use of mechanical insulation or better cabinet design. (the goal: reduce costly use of other means of insulation, result in more efficient use of power and so use a less powerful and cheaper system setup)

B. An in-ceiling loudspeaker for commercial use that provides a wider angle for sound dispersion on a listening plane (different to the normally specified polar dispersion) throughout the working frequency spectrum on a drop ceiling setup. (the goal: wider dispersion in a wider frequency spectrum allows for better area coverage and thus, less speakers per square meter: Cheaper setups)

C. An in-ceiling loudspeaker for commercial use with narrow dispersion for high-ceiling applications where late-reflections (>30ms) are not desired for speech intelligibility during “paging”. (the goal: improve speech intelligibility in large halls with directional loudspeakers, but still with a typical setup installation on high ceilings)

D. An in-ceiling loudspeaker for commercial use that makes use of wireless transmission of audio data where installation with cable is not possible or expensive. (the goal: reduce installation costs where cable is expensive or permanent installations are not the case)

E. An in-ceiling loudspeaker for commercial use that makes more efficient use of power and flexibility for transmission and reproduction in distributed sound systems by means of discrete class-D amplification and active crossover design. (the goal: using class-D amplifiers at each loudspeaker together with active crossovers would yield a more power-efficient and cheaper system than traditional 70.7/100 V systems with heavy and costly transformers and central amplification units)


There you go, help me rank them and please comment on any.
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Old 27th August 2013, 03:23 AM   #2
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E. is certainly an interesting, modern approach. Of course you have to run both power and signal to it, unless you combine it with D.
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Old 27th August 2013, 04:08 AM   #3
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Have you interviewed sound system professionals in your market area? Have you actually identified some of these goals of yours as existing problems for sound contractors? it is one thing to hypothesize that reflections are going to interfere with intelligibility, but it is another to find it as a real problem. In other words, I hope you are not a solution looking for a problem. For a commercial product to have an advantage it needs to solve a problem that other products do not. I suggest talking to people who install such systems and ask them what features the current products do not have that they would like to have. And ask them what consistent problems they face during installation and in system performance.

And have you analyzed the performance expected of such speakers? In your home listening or home theater setting, you are probably listening to the sound as a primary activity - paying attention, in other words. Ceiling speakers implies commercial or industrial settings, and the needs there are very different. No one sits in a restaurant critically listening to the background music. Not unless it sounds so terrible as to become your focus. For example an FM receiver that is dropping in and out of tune or speakers that are particularly garbles is very noticable and annoying while dining. But otherwise, the music is only there to provide a soothing background. No one will be listening for soundstaging and flay EQ from 20-20kHz. PAging only needs to be heard and understood, it doesn't have to sound hifi. SUbwoofers add dimension to home theater, but I feel serve little purpose in a commercial ceiling installation. Until you listen side by side, no one every thinks the telephone sounds all that bad, but it has a very restricted response range. People will think ceiling speakers sound fine even without wide freq response.

A. Just my impression, but I think the main source of sound leakage into the building would be from the sound itself rather than conduction through the frame structure. If you need to market this, then come up with some specific scenarios that would validate the need. In an airport no one cares what sound escapes to the roof. Same in a stand alone restaurant. If the installation has other noises, like a busy kitchen, then there would already be insulation above if there were residential above the commercial. You mention cabinet. Many ceiling speakers have no cabinet, and there are inexpensive molded enclosures available. Have you surveyed existing products with that feature? In general a restaurant - as a typical install - has speakers in the drop panels with open back.

D. A wireless connection to the speaker means the speaker will have to be powered - have its own power amp - and that means it has to have a source of power. Either a mains outlet or distributed low voltage supplies. If you can run those wires to the speaker, I don;t know why signal wires could not be run instead, but i am sure there are cases. But a commercial product ought to be something most could use, rather than be for very special circumstances. There are existing wireless powered speakers, I was in fact looking at some a couple hours ago. They are great for something like an outdoor auction. It seems to me that if you are installing ceiling speakers, rather than hanging wall speakers, you are already in the land of permanent installations, at least permanent enough. Wire may not be cheap, but a 70v line works just fine on cheap zip cord. And if you are striking your system in a month, abandoning a couple hundred feet of zip in the ceiling is not a high price to pay compared to the increased complexity if wireless and multiple small amps.

E. This sounds made up to me somehow. An active crossover to me means you plan to biamp, so that means at least a two-way speaker at each point. And thus two amplifiers at each point. Plus the power all that runs on must be distributed. I don;t see a lot of saving there. I have never thought of 70v transformers as large and heavy. The transformers at each speaker are small, a 10w transformer costs less than $5 and weighs less than a pound. They can mount right on the speaker frame, simplifying installation. And 10 watts is really pretty loud. When I do a restaurant I am more likely to tap it at 1 or 2 watts than any higher. There are many choices of existing ceiling speakers that come with transformers already on them. What sort of installs do you have in mind? Power efficiency sounds good on paper, but if I put up 20 speakers tapped at 2 watts, that only adds up to 40 watts. KNocking that down to 35 won;t impress anyone.
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Old 27th August 2013, 12:51 PM   #4
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Nine out of ten businesses suffer from a combination of poor music choice and crappy acoustics which I am afraid might be too difficult of a problem to fix .
The large box stores generally have the least offensive hardware installed as they have the resources to do so.

Now a DSP system that could transform a machine shop into a library would be amazing, again it is acoustics of the building that is the major factor in voice intelligibility and accurate music reproduction.
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Old 27th August 2013, 01:16 PM   #5
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Getting AC power to in-ceiling speaker's would add to the cost and complications.

a] Any in-ceiling AC power wiring has it's own set of code rules.
b] AC power wiring will require a licensed electrician rather than an installer.
c] AC power wiring will require a building permit and an inspection.
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Old 27th August 2013, 01:28 PM   #6
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Quote:
(the goal: using class-D amplifiers at each loudspeaker together with active crossovers would yield a more power-efficient and cheaper system than traditional 70.7/100 V systems with heavy and costly transformers and central amplification units)
Transformers for these types of Speakers come cheaper than multiple class-d amps. Cost efficiency and sometimes reliability (depending on the exact usage you might have to achieve some proven figures).

I would concentrate on the speaker alone if I were you.

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Charles
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Old 27th August 2013, 01:35 PM   #7
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The main reason I use 100v line is because the sound need not be HiFi quality as it is intended for background and one can send a DC level down the cables to activate the speakers, that have been switched off by the listener, for announcement by way of speech.
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Old 2nd September 2013, 03:15 PM   #8
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That's an interesting type of control Jon. Not seen that before.
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Old 2nd September 2013, 09:33 PM   #9
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Sounds like everything you list already exists.
Are you up to date with all the products available and currently on the market?

Most of the bad sounding ceiling rigs you've heard are simply because clients wants the lowest cost. So even though there are really good products out there that do just about everything you listed (including self-powered POE-type systems) they are simply too pricey to justify for most businesses.

Other than that, it is amplifier techniques and equalization that tend to be lacking even with good speakers. So you could do a "Bose" type setup with a DSP/amplifier box that feeds your speakers via cat-5 or wireless (if you solve the local power supply issue.) Something like the Meyer Sound MM4XP and the MPS-488HP system but in a flush ceiling-mount setup maybe.

However your point "E" is wrong in the sense that there's probably nothing as cost effective or simpler to wire than a 70V or 100V type distributed system (and meets codes)! -

Quote:
Originally Posted by davidbosch View Post
I'm an industrial engineering student and as my thesis project in product design and development I will present this semester a design for an in-ceiling loudspeaker for commercial application. Right now I'm at a phase where I must choose between several proposals or come up with more that deal with typical problems in PA systems that use in-ceiling loudspeakers. I could use everyone's opinion around here. Just so you know, a little background: my knowledge on loudspeakers is very DIY. I've been building cabinets and putting systems together since I was 11. I use some basic software for designing cabinets and crossovers and one of my aims is to learn more about speaker measurement techniques with my thesis project. I also need to achieve a system-level design together with a "frankenstein" prototype by the end of the project, in order to validate my thesis.

Here are five proposals to which it has come down to. You can rank them on the basis of commercial feasibility. More proposals are welcome. These are just short descriptions. If you want the longer descriptions (more technical) or book references send me a message.

A. An in-ceiling loudspeaker for commercial use that limits leakage of low-frequency sound into building structures by the use of mechanical insulation or better cabinet design. (the goal: reduce costly use of other means of insulation, result in more efficient use of power and so use a less powerful and cheaper system setup)

B. An in-ceiling loudspeaker for commercial use that provides a wider angle for sound dispersion on a listening plane (different to the normally specified polar dispersion) throughout the working frequency spectrum on a drop ceiling setup. (the goal: wider dispersion in a wider frequency spectrum allows for better area coverage and thus, less speakers per square meter: Cheaper setups)

C. An in-ceiling loudspeaker for commercial use with narrow dispersion for high-ceiling applications where late-reflections (>30ms) are not desired for speech intelligibility during “paging”. (the goal: improve speech intelligibility in large halls with directional loudspeakers, but still with a typical setup installation on high ceilings)

D. An in-ceiling loudspeaker for commercial use that makes use of wireless transmission of audio data where installation with cable is not possible or expensive. (the goal: reduce installation costs where cable is expensive or permanent installations are not the case)

E. An in-ceiling loudspeaker for commercial use that makes more efficient use of power and flexibility for transmission and reproduction in distributed sound systems by means of discrete class-D amplification and active crossover design. (the goal: using class-D amplifiers at each loudspeaker together with active crossovers would yield a more power-efficient and cheaper system than traditional 70.7/100 V systems with heavy and costly transformers and central amplification units)


There you go, help me rank them and please comment on any.
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Old 2nd September 2013, 09:48 PM   #10
Pano is offline Pano  United States
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Quote:
Originally Posted by ndcraig View Post
However your point "E" is wrong in the sense that there's probably nothing as cost effective or simpler to wire than a 70V or 100V type distributed system (and meets codes)! -
That's what I was thinking, glad to hear someone else say it.
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