Speaker Design

Of all the electronic items made over the years, the one that appears to have changed the least is the speaker. They have always been pretty much the same. Originally they used electro magnets, then changed to fixed magnets. The cones have used different materials, but mostly paper and plastics, some with a foam at the edges. There was a time when a small cone was added to the middle of a large speaker to act as a tweeter, although they were not very effective and is no longer in use. The coils have always been pretty much the same. I see little change in speakers in the future, other than the trend seems to be smaller speakers which can still deliver high power. However there seems to be limitations on sound quality with smaller speakers. Also, plastic cabinets will never replace real wood, and never sound (or look) as good as wood.

The one thing that I have noticed are the Bose speakers. From what I read, they use an enclosure which directs the sound in a way that causes air pressure to move inside a room, and thus makes more powerful bass from their sub-woofers. From what I understand, the speaker itself is the same, but the cabinet is different. It's capable of delivering more bass from less speaker size.

It appears that Bose is very closed mouthed about how they achieve this. Their speakers are probably the most expensive available, so it makes sense that they keep secret how they design these cabinets. My reason in posting this is because someone must know how they do it. But I have not been able to find anything on the web.

Does anyone know of any websites that explain in detail how they design their enclosures (cabinets), and what is used? I have always built my own speaker cabinets, and would like to try a similar design.

Thanks

Reply to
tangerine3
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Fractional horsepower motors haven't changed much in a hundred years, either. Probably for the same reasons. A speaker *is* a motor, after all. ;-)

More midrange, anyway. They aren't very good speakers.

They're just folded horns, AIUI. They do have a bunch of patents but mostly, no one wants to make sound like them. They sure don't sound that good to me, particularly for the price they want.

You're probably out of luck if you want to copy Bose. I think you'll need simulation to match them. I'm sure the formulas for more "normal" speaker enclosures are on the net somewhere.

Reply to
krw

Bose = crappy speaker and a signal processing unit to make it sound 'right'.

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Reply to
Nico Coesel

A good high-pressure hydraulic servo can hit hundreds of Hz. A few of those could drive a piston the size of, say, your wall.

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John Larkin                  Highland Technology Inc
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Reply to
John Larkin

I experienced such a hydraulic "shake-table" at Kodak, powerful enough to shake a Mack truck. We were warned not to stay on the table while your gear is being tested... "you'll lose your kidneys" :-( ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

** The AC supply transformer has changed the least.
** Could say that about the automobile - still have four wheels and an internal combustion engine.
** Twin cone speakers are still around, common in ceiling speakers for BGM and paging.
** Hard to beat copper wire - but some makers are using CCA or Cooper Clad Aluminium wire.
** You have not noticed the major changes over that last 50 years.

Dome tweeters and mid units were not always around.

** Strewth !! So he notices giant leaps backwards ??
** If you are alluding to the "Acoustimas" - that is no secret at all. Its a "bandpass" box, probably 8th order.

Other designs have uses simple porting or long pipes and Bose are famous for using custom equalisers in the amplifier chain - eg in the 901 and 801 series.

Worst speaker idea ever thought of.

** Or you could aim higher ...

.... Phil

Reply to
Phil Allison

Back 20+ years ago when I worked in electronic service, I recall the Bose 901 speaker had 8 or 9, small speakers (4" or 5") in series. The rep once said the hooked one up to the 120 volt AC outlet and it played until it shook a wire loose from one of the speakers, it still worked after repairing the broken wire. Mikek

Reply to
amdx

"amdx"

** All the drivers have 1 ohm voice coils and the cabinets were tuned to about 60Hz.

Earlier versions used 8 ohm drivers wired in series parallel.

** Did the Bose rep really say that ?

Amasing ....

.... Phil

Reply to
Phil Allison

Yes.

I can't vouch for the truth of his story, just that he said it.

Mikek

Reply to
amdx

Yea, but hooked to 120 volts AC, what's it going to play? 60hz hum is about all it could emit, and by that time, every coil would be glowing red from the heat, and the cones would burn up. Somehow I dont buy into this...... Sounds like a folk-tale to make sales. I'd be more likely to believe it being connected to a 1000w amplifier or something like that.....

Reply to
tangerine3

** The story might even be true.

With the divers all wired in SERIES, if a feed wire on any one failed, or as more likely the case here simply BURNED OUT - all sound stops.

The lie is that it lasted more than two seconds.

.... Phil

Reply to
Phil Allison

I was thinking more in terms of electronic components. whereas an electric motor is more of an electric device. However you're correct, in that motors have not changed much over the years.

I sure can't think of any other way to convert electrical energy into horsepower attached to the end of a rotating shaft. It's kind of odd, when you think that modern motors are built smaller for their HP rating, much due to better insulator materials, compared to the old enamel and cloth used on the old motors. Yet, the old motors seem to outlast most of the newer ones.

Of course, much of this is planned. Im years past, products were built to last, and engineers were educated to design better and longer lasting products. These days, products are built to make a fast buck, and engineers are educated to design products which make the biggest buck and fail shortly after the warranty ends, so they can make another fast buck.

Reply to
tangerine3

ther.

;-)

Then you probably need to look at linear synchronous motors.

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The problem with loudspeaker motors is that you have a long magnetic path length, thus a low magnetic field across the motor coil. A linear synchronous motor allows shorter magnetic paths and higher magnetic fields across a number of separate coils, but you've got to adjust the magnitude and direction of the current through each coil to match the sense and magnitude of the magnetic field at each particular coil when the moving element is at a particular point along the travel.

You could make a more efficient speaker that way, but construction and control would both be more complicated and expensive. It doesn't seem to be cost effective.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

I think the story needs to be verified. Who has some 901's? Mikek

Reply to
amdx

The 901 manual says it's "compatible" with receivers up to 450W RMS (sic), but gives the speaker rating as "250W IEC", so presumably rather less than 250W continuous.

120VAC across the nominal 8 ohm impedance is 1800W. The Z might be a bit higher at 60Hz, but still, it's gonna break or fry either immediately or in pretty short order.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Nice bent perception of reality you've got there.

Reply to
Chieftain of the Carpet Crawlers

Hmm.. okay, suppose the Z at 60Hz is actually more like 12 ohms, and they connected the speakers in series-- that's 600W. I might believe they would survive that for a few unpleasant seconds.

Best regards, Spehro Pefhany

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"it's the network..."                          "The Journey is the reward"
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Reply to
Spehro Pefhany

There are lots of kinds of motors

Brushed with powered field Brushed with PM field Variable reluctance Hybrid PM/VR, like most steppers Induction AC synchronous Synchro/resolver Linear solenoids, which are really VR, I guess Electrostatic Piezo Memory wire Thermal Electrohydraulic Plasma wind

and linear variations on the above. Several of those types have been adapted as speakers. But the conventional cone and horn types seem to work pretty well.

The speaker type that has no corresponding motor is the weird directional nonlinear ultrasonic thing.

Sirens are awfully loud; maybe you could make a speaker using that mechanism.

It's kind of odd,

When I went to engineering school, we didn't learn how to build products at all. It was mostly electronic theory, and rightfully so.

These days, products are built to make a fast buck, and

Consumers steer the market. Businesses and companies make what people will buy.

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John Larkin                  Highland Technology Inc
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Reply to
John Larkin

What is your special "accurate" method for that?

Hint: It ain't an ohmmeter readout.

Reply to
Chieftain of the Carpet Crawlers

And electronic components are not?

Steam powered maybe ;-)

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Reply to
Fred Abse

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