Speaker Design

[[email protected]]

And electronic components are not?

Steam powered maybe ;-)

Just what I want, a calliope in my living room. ;-)

 

[gregz]

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

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

 

[gregz]

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

I get 1200 watts at 12 ohms.

Greg

 

[gregz]

Chieftain of the Carpet Crawlers

What is your special "accurate" method for that?

Hint: It ain't an ohmmeter readout.

Should be 8 ohms at 100 Hz.

Greg

 

[gregz]

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

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

 

[Spehro Pefhany]

I get 1200 watts at 12 ohms.

Greg

With two in series?


Best regards,
Spehro Pefhany

 

[[email protected]]

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.

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).

 

[mike]

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

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 <Jim-T@analog_innovations.com>
Organization: Cox Communications
Newsgroups: sci.electronics.design

On Fri, 27 Dec 2002 09:17:39 GMT,
analog <[email protected]>,
In Newsgroup: sci.electronics.design,
Article: <[email protected]>,
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 ) |
| | 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 ""
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 Voice480)460-2350 | |
| Jim-T@analog_innovations.com Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

For proper E-mail replies SWAP "-" and "_"

I love to cook with wine. Sometimes I even put it in the food.

 

[[email protected]]

Have you tried Windows Steampunk Edition?

Nope and have no idea what it is.

 

[Chieftain of the Carpet Crawlers]

But since you ask the question, you must think your a fucking genius.
Mikek

This the dork who claims he never insults anyone?

It is "you're" by the way, dipshit.

 

[Chieftain of the Carpet Crawlers]

Chieftain of the Carpet Crawlers


Should be 8 ohms at 100 Hz.

Greg

Know any ohmmeters that modulate their test circuit?

 

[gregz]

Chieftain of the Carpet Crawlers

Know any ohmmeters that modulate their test circuit?

Ok, Z. I think the r is close to 7.2 ohms.


Greg

 

[Phil Allison]

"Chieftain of the Carpet Crawlers"

What is your special "accurate" method for that?

Hint: It ain't an ohmmeter readout.

** 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

 

[Ralph Barone]

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

Bose uses nothing but the best marketing...

 

[amdx]

"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

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 60hz

2.485Vpp / 0.315mapp = 7.888 ohms

Spot on there Phil!

FWIW, I got 34 ohms at 129hz.

Mikek

 

[Phil Allison]

"amdx"

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 60hz

2.485Vpp / 0.315mapp = 7.888 ohms

Spot on there Phil!

FWIW, I got 34 ohms at 129hz.

** 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

 

[gregz]

"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

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

 

[gregz]

"amdx"



** 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

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

 

[Phil Allison]

"gregz"

I came close as I just remembered measuring one late driver. The series I,
II, used standard 8 ohm 3 series, 3 parallel arrangement.

** Yep, cos 24 / 3 = 8

The original Bose 800 PA speaker used eight 16 ohm drivers.

Four series wired pairs connected in parallel.

32 / 4 = 8



..... Phil

 

[Sjouke Burry]

[email protected] wrote in

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

What is stopping you from opening one up??
You will find that mostly they squashe 90 percent of the input power
to make the remaining power appear as a flat spectrum. thats why you
need 2X100 watts amplifiers, with an efficient speaker 75 milliwatt will
produce voice level audio in your room.
No Bose speaker will ever be found in my house( four sets of bass-reflex
sets of assorted breeds sitting around my house)