But a speaker is nothing more than a linear motor. There have been some improvements, but mostly materials (rare earth magnets, and such).
They're smaller, mostly because they're engineered closer to the edge. They don't last as long for similar reasons.
No, it's more an issue of cost. There would be no market for a washing machine with a better motor if it cost $100 more. For one thing, motors rarely fail, now. For another, the competition will beat you to a pulp.
Just what I want, a calliope in my living room. ;-)
Have you tried Windows Steampunk Edition?
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As far as I know, they are bandpass boxes, using pipes, and some use boxes and pipes. I don't think they produce any more bass than other ported speakers. A fellow wrote up building and tests many years ago in speaker builder magazine. I'm not going to search them myself. Bandpass boxes come in different orders.
Wood does not make the best sound. Whizzer ones are still being used. The 901 is a ported loudspeaker.
Greg
I get 1200 watts at 12 ohms.
Greg
Should be 8 ohms at 100 Hz.
Greg
Of course the 901 came with 3 sets of drivers from what I know. Series one, made in USA by cts. Series two, I think Japan. Series 3 up, Probably made by Bose. Series 1-2 closed box design, with proper stuffing. Series 3 up, plastic echo boxes, no regards to damping material.
Greg
With two in series?
Best regards, Spehro Pefhany
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When I was a kid, I took one of those cheap 2 inch transistor radio speakers, put a line cord on it, and plugged it in to a 120VAC outlet. It went into a puff of smoke instantly, and sort of exploded in the process. It didn't blow the 15A house fuse either, (still had fuses).
I did a bunch of experimenting 40 years ago. The objective at low frequencies is to make the resonant frequency as low as you can get it. Couple tightly to the air. Then damp the resonance and boost the crap out of the area below resonance. Some combination of acoustic porting and electronics is used.
You can do some interesting things with negative output impedance amps. Even better to sense the cone position and use that for feedback. I expect there's some interesting stuff to be done with today's DSP horsepower. Problem is making the electronic filters narrow enough to cancel the acoustic stuff without sounding like an echo chamber.
You can make the frequency response flatter, but the cost is usually phase error. Looks good on the amplitude response plot, but can sound like crap.
Starting at ground zero, take a single-tone signal source and a sound level meter. Move the source and meter around the room and plot the frequency response for different locations. You can do the test with noise, but it will mask much of the resonance.
The plot will look horrible in most cases. The best combination of source and listening locations is rarely anywhere near compatible with your room arrangement. Fixing it with electronics is an exercise in futility. You can do some good for exactly ONE listening location...maybe.
If you're not gonna fix the room, you're wasting effort tweaking speakers. So, go buy some anechoic chamber cones to line the room. Then you're ready to start thinking about speakers.
What do you listen to? If you want the movie theater experience and like to watch movies that blow stuff up, you're gonna need some serious transient acoustic power. That means BIG speakers, or lots of small ones, and long cone throw... or some acoustic matching transformer. I have Klipsch Corner Horns @105dB/watt and 100W/ch.
The horns aren't flat and my room is crap, but I can hear stuff blow up. I've been afraid to plot the room since I took out the carpet and put in laminate flooring. I don't want to know.
If you listen to the symphony, you may not like the sound of Klipsch Horns. I had some big Magneplaner ribbon speakers that I liked better, but my amp got really hot at relatively low volume.
I thought about building some straight exponential horns, but decided I'd rather park the car in the garage.
I listen to popular music while at the computer. I've found the Yamaha YST-MS50 to be the best of the under $5 garage sale computer speakers. Sound good enough if you don't need a lot of volume. And the incremental power consumption is low. I rarely fire up the horns any more. The key to a happy life is low expectations!!
If you like woodworking, building speakers is as good a hobby as any.
Your biggest problem is characterizing what you have. Invest in some acoustic measurement tools. And be prepared to haul it out into an open field for making measurements. Inside measurements are pretty much useless unless you have a "flat" room.
There are some interesting audio spectrum analyzer programs for a PDA. I've never found a good free one, but the pay ones often have a demo mode that runs for a minute. That's long enough to get a reading. A PDA isn't necessarily flat, but once you get the feel for it, it makes a useful survey tool. Better microphone can help too.
I tried to get a handle on phase by measuring step response. Got nowhere, but that was 40 years ago before serious computing was available.
I saved this off the web:
Subject: Re: Speaker models for SPICE simulations Date: Sun, 29 Dec 2002 22:29:57 GMT From: Jim Thompson Organization: Cox Communications Newsgroups: sci.electronics.design
On Fri, 27 Dec 2002 09:17:39 GMT, analog , In Newsgroup: sci.electronics.design, Article: , Entitled: "Speaker models for SPICE simulations", Wrote the following:
| |Happy New Year everybody! And a little offering for the group: | |Here is an example of a SPICE model that very accurately mimics |measurement. It is for a speaker with both an actively driven cone |and a passive radiator cone. | [snip] | 1.3m | | | | | | | / | +---+ | | +---+ | Resa \ Faa | ,!. | | Fap | ,!. | | 90 / [i]( I ) | | [i]( I ) | | | 588m | `+' | | 235m | `+' | | | | | | | | | | | o------+-------------+-------+---}---+----+----+-------+---)---+ | _|_ | / | | / / / Acoustic | Ro \ 1 ohm | | Output | / | | Vo o--+--------+----------------+ | [snip] |Hope you liked it. Let me know what you think and what other such |SPICE models you may have found useful. -- analog
Hi analog, Just getting around to entering your model into PSpice.
Couple of questions on the "F" sources:
Do I presume correctly that current entering the *top* of the "[i]" blocks, is times the gain (588m and 235m respectively) and exits (is sourced) from the "+" terminal?
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat | |
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I love to cook with wine. Sometimes I even put it in the food.
Nope and have no idea what it is.
Know any ohmmeters that modulate their test circuit?
Ok, Z. I think the r is close to 7.2 ohms.
Greg
"Chieftain of the Carpet Crawlers"
** An ohm meter will measure the impedance of a speaker system like the Bose 901 and tell you if all the drivers are connected. A reading of 6.6 ohms is correct and equates to a nominal value of 8 ohms. In general, a woofer's impedance at 250 Hz is 1.2 times the DC resistance.Since the later versions of the Bose 901 used a box tuned to 60Hz, the measured impedance is close to 8 ohms at that frequency too.
If high power is applied, voice coils heat and DC resistance values can double at the extreme temp limit just before destruction.
... Phil
Bose uses nothing but the best marketing...
I measured mine using a 1 ohm resistor as a current shunt. After subtracting the voltage drop across the resistor I got,
7.88 ohms as the impedance of the speaker at 60hz2.485Vpp / 0.315mapp = 7.888 ohms
Spot on there Phil!
FWIW, I got 34 ohms at 129hz.
Mikek
** That must be the upper resonance of the driver in the tuned box.
There is another one at 30 or 40 Hz with a between at the box frequency of
60Hz.Around 250 to 400Hz you will see another, broad impedance minimum.
... Phil
I came close as I just remembered measuring one late driver. The series I, II, used standard 8 ohm 3 series, 3 parallel arrangement.
Greg
Never measured current drivers, but in general, that 250-400 range is one fault of them. There seems to be a rise in volume there.
Greg
"gregz"
** Yep, cos 24 / 3 = 8The original Bose 800 PA speaker used eight 16 ohm drivers.
Four series wired pairs connected in parallel.
32 / 4 = 8.... Phil
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