Revised technical question:

[Shawn Sutherland]

What is the best capacitor value for audio frequencies between 100 HZ and
6000 HZ into an impedance of 1K ohms?

Please let me know.

Shawn

 

[Myron Samila]

1k ohm for audio? as in where in the circuit?? speaker? active part of the circuit?
passive crossover?

A capacitor cannot limit bandwidth on the top end, you'd need a bandwidth limiting
crossover network to limit frequencies between 100hz and 6khz.

We need the following information:

Application?
What you are trying to achieve??

 

[Brian Oakley]

A cap cant limit on the high end?? Are you sure about that? If you take an
appropriate cap across a speaker, doesnt that short out some of the high end
freqs?

 

[Myron Samila]

You wouldn't use a cap to limit bandwidth in parallel in audio.

You'd use a coil to limit high frequencies at a rate of 6db/octave, in series. A cap in
series with the speaker will filter low frequencies.

Passive crossovers are horrible anyhow, bi-amping or three way (active xovers) work best.

Yes, the OP won't get his question answered because it is too vague.

 

[Brian Oakley]

It depends on his application. As I said in my post "across the speaker"
will roll off the top end. As you stated in your post, a cap in series will
roll off the low end. We dont know what kind of circuit application he is
using, hifi, mono, etc. He may be looking for a filter for his ham radio
reciever for all we know so a crossover may not even be what he needs.
Anyway, until he is more specific, we wont be able to answer.
Brian

 

[Switch]

It depends on his application. As I said in my post "across the speaker"
will roll off the top end. As you stated in your post, a cap in series will
roll off the low end. We dont know what kind of circuit application he is
using, hifi, mono, etc. He may be looking for a filter for his ham radio
reciever for all we know so a crossover may not even be what he needs.
Anyway, until he is more specific, we wont be able to answer.
Brian

How does a cap across the speaker roll off top end? I believe that is incorrect. Hifi,
mono, 5 channel, it doesn't matter. A passive filter is a passive filter, period, ham
radio or not (I have friends who are operators and I've built many bandwidth filters for
them. The only way to roll off high frequencies to a speaker is to put a coil in series
with the speaker or resistor across the speaker (high value resistance will absorb
frequencies at a specific attenuation, as 6db/octave typical). Putting a capacitor across
a speaker is the same as putting it in parallel. Trust me, it won't work, even when a
12db/octave filter is used, the cap goes in series with the load, the coil goes in
parallel to the load for low-pass applications, reverse for high pass applications.



A crossover is a filter, exactly that, highpass vs lowpass vs... bandpass..... all
crossovers (a term used in the audio field).

Top posting is bad, stop it.

 

[Brian Oakley]

How does a cap across the speaker roll off top end? I believe that is incorrect. Hifi,
mono, 5 channel, it doesn't matter. A passive filter is a passive filter, period, ham
radio or not (I have friends who are operators and I've built many bandwidth filters for
them. The only way to roll off high frequencies to a speaker is to put a coil in series
with the speaker or resistor across the speaker (high value resistance will absorb
frequencies at a specific attenuation, as 6db/octave typical). Putting a capacitor across
a speaker is the same as putting it in parallel. Trust me, it won't work, even when a
12db/octave filter is used, the cap goes in series with the load, the coil goes in
parallel to the load for low-pass applications, reverse for high pass applications.



A crossover is a filter, exactly that, highpass vs lowpass vs... bandpass..... all
crossovers (a term used in the audio field).

Top posting is bad, stop it.

I will accomodate your wish about top posting. And dont be telling people
what to do.
A cap does roll off the frequencies when placed across the speaker. If you
study filter design, the coil in series does what a capacitor in parallel
does. The point is the capacitor needs to be the correct value to do so.
Granted, it may be a large capacitor, but it does work. Try it. Also, the
ARRL Handbook has some good theory on filters.'
Brian

 

[Brian Oakley]

"Switch" wrote ...

A capacitor's impedance goes down as the frequency increases.

Someone that understands!
B.

 

[Switch]

I will accomodate your wish about top posting. And dont be telling people
what to do.

Usenet rules.... read the FAQ and rules and regulations of usenet, it is in black and
white.

A cap does roll off the frequencies when placed across the speaker. If you
study filter design, the coil in series does what a capacitor in parallel
does. The point is the capacitor needs to be the correct value to do so.
Granted, it may be a large capacitor, but it does work. Try it. Also, the
ARRL Handbook has some good theory on filters.'
Brian

Brian, in my time of designing filter networks, reading books, using crossover/filter
design software, there is no where that suggests the use of a capacitor in parallel to a
speaker to limit frequency. If so, what is the predictable filter slope??

Anything less than 6db/octave is useless in audio.

 

[Switch]

A remarkably rash pronouncement. We'll write it off
to youthful indiscression and inexperience.

Why would that be considered rash? if you are trying to limit bandwidth (lets say low
pass) from 250hz up to 20khz, then at anything less than 6db/octave, you will still hear a
great deal of program material at the next lower octave. The slope is too great,
typically, in home audio filter networks employ a minimum of 6db per octave, and then
higher quality ones use 24db/octave, Butterworth, Linkwitz, Bessel, Bec... depending on
the desired Q.

Look, if you want to limit bandwidth in audio, I am simply suggesting that your method is
not practical and not used.

ie: 8ohm speaker, bandpass 500hz-6000hz, use a 40mF (non polarized) cap in series with a
coil of .212 mH, this will bandpass at an effective slope of 6db/octave on the upper and
lower end of the shelf.

What now?? Qualify yourself, otherwise your posts aren't of any use.

 

[Switch]

You clearly haven't studied many schematics if you think
that simple "1-pole" R/C filtering "is not pracical and not
used" it is used in virtually every AC-coupled circuit ever
made. Perhaps you don't recognize it because it is so pervasive.

We are talking audio (AC), not any other type of AC coupled circuit. You are clearly (not
to you though) missing the point.

Someone suggested you can bandpass audio using only a cap, how?(bandpass passively on the
output of an amp) Where does it filter the low end? Are you going to put a 100,000 mF
capacitor at 200V to cut out frequencies at 8 ohms? Practical? ummmmmm.......

The suggestion of bandpass came up regarding ham radios........ that is why we are on the
topic of audio, nothing to do with the OP.

Well, if you go back and read the original post, it wasn't
even detailed enough to mention anything about using it
in speaker crossovers (or any other identifiable application).

I was responding to someone who said you can use a capacitor across a speaker to achieve
bandpass, not the OP.

Did you even understand the concept of the Shakespear quote?

We're talking electronics here.....I'm not in the alt.shakespear.chat.forum, his rants are
about as out of date as your theorems.


You're still incorrect unless you can prove otherwise. Show me an example using ONE
capacitor how you would filter frequencies between 100hz and 5000hz with an 8ohm speaker
load?? we are assuming the signal is audio, from an amp. That is what I was arguing, it
is incorrect and cannot be done, period......

Lets stop the misinformation here. I wasn't referring to the OP at all, all previous
posts have snips of the question I was answering.


Do you own a stereo? Do you understand what I'm talking about at all??!?! That is my
only question. If there is any other way of doing what I'm suggesting, why doensn't
anyone else do it?

Just like the thread about 50hz vs 60hz motors, oh my, don't even get me started on that
one. So much WRONG information, I only wish I jumped in on that one.

 

[Myron Samila]

Hate to say it Richard,

This person is right........ You cannot create a bandpass audio filter with just a cap
across a speaker load as was mentioned that you could in a previous post. If you put a
cap in series with the speaker load, you create a filter. (filtering out low frequencies).

I think you missed the initial point that I brought up in this thread a while back.

And you don't need to study schematics to understand how a speaker crossover or bandpass
filter works. Usually, there are no more than 4 components (in a 24db/octave slope
passive crossover), this is the only component between a speaker and an amplifier.

I think I also talked about the ham radio application and such, but whatever. Points get
missed, heheh.

All I do is live and breathe professional audio, have done so for the past 10 years, wind
my own air core coils, built hundreds of passive and active crossover networks . I've
never put a cap in parallel (across) a speaker load to achieve what you guys are arguing
about, ?!?! heheh. If a cap could be used as a bandpass device in audio, that would be
great, since then I would start to wonder why we use coils (which are expensive, power
robbing, expensive, oh and did I mention expensive?, high quality audio air core coils can
reach upwards of $400!!!! or more (Cnd), for only 100Watts power dissipation!!!

Anyhow, great discussion!! A lot can be learned here!

 

[Brian Oakley]

Usenet rules.... read the FAQ and rules and regulations of usenet, it is in black and
white.

Doesnt matter, its not your job to tell people what to do. You can explain
the rules, but assuming to be the boss doesnt make you someones boss kid.

 

[Brian Oakley]

Hate to say it Richard,

This person is right........ You cannot create a bandpass audio filter with just a cap
across a speaker load as was mentioned that you could in a previous post. If you put a
cap in series with the speaker load, you create a filter. (filtering out low frequencies).

I think you missed the initial point that I brought up in this thread a while back.

And you don't need to study schematics to understand how a speaker crossover or bandpass
filter works. Usually, there are no more than 4 components (in a 24db/octave slope
passive crossover), this is the only component between a speaker and an amplifier.

I think I also talked about the ham radio application and such, but whatever. Points get
missed, heheh.

All I do is live and breathe professional audio, have done so for the past 10 years, wind
my own air core coils, built hundreds of passive and active crossover networks . I've
never put a cap in parallel (across) a speaker load to achieve what you guys are arguing
about, ?!?! heheh. If a cap could be used as a bandpass device in audio, that would be
great, since then I would start to wonder why we use coils (which are expensive, power
robbing, expensive, oh and did I mention expensive?, high quality audio air core coils can
reach upwards of $400!!!! or more (Cnd), for only 100Watts power dissipation!!!

Anyhow, great discussion!! A lot can be learned here!

--
Myron Samila
Toronto, ON Canada
Samila Racing
http://204.101.251.229/myronx19

I think the question that Switch asked was how does a cap across a speaker
roll off frequenceis at the top end. He didnt say anything about bandpass. A
bandpass filter consists of several poles made up of caps and coils. But a
cap across an 8 ohm load can roll off frequencies at the top end. Like I
said it depends on the size and type of the cap. Xc =2pi*f*C. This is the
formula one would use to calculate the capactive reactance to frequencies
with a given capacitance. Plug in the frequency in question with the
reactance in question and it will give you a capacitance that you need. Find
a good electronics book and a physics book. it does work.

 

[Brian Oakley]

We are talking audio (AC), not any other type of AC coupled circuit. You are clearly (not
to you though) missing the point.

No I think he understands the point as it was originally described in the
original post.

Someone suggested you can bandpass audio using only a cap, how?(bandpass passively on the
output of an amp) Where does it filter the low end? Are you going to put a 100,000 mF
capacitor at 200V to cut out frequencies at 8 ohms? Practical? ummmmmm.......

The suggestion of bandpass came up regarding ham radios........ that is why we are on the
topic of audio, nothing to do with the OP.

The original post about filtering in ham radios was my post. It doesnt
mention bandpass, nor 8 ohm load for that matter. The original post says
1000 ohm impedence. There are a lot of things you can do with audio at 1000
ohms that may not be practical at 8 ohms. We are not talking hi fi audio
here. We are more than likely talking about a lowpass filter using a cap
across the speaker leads of a 1Kohm speaker (or headphones).

I was responding to someone who said you can use a capacitor across a speaker to achieve
bandpass, not the OP.

Im not sure where you keep getting the idea about bandPASS. BandWIDTH was
what was mentioned, and a cap can effectively limit the bandwidth by rolling
off the high end frequenceis. We were talking about a rolloff filter, one
that rolls off the higher frequencies. Theres a big difference.

We're talking electronics here.....I'm not in the

alt.shakespear.chat.forum, his rants are

about as out of date as your theorems.


You're still incorrect unless you can prove otherwise. Show me an example using ONE
capacitor how you would filter frequencies between 100hz and 5000hz with an 8ohm speaker
load?? we are assuming the signal is audio, from an amp. That is what I was arguing, it
is incorrect and cannot be done, period......

Again, 8 ohms was not mentioned in the original post. 1000 ohms was the
load. For all you kids out there that dont know it, there is a lot of older
equipment that use higher impedence output audio. It can range from 6k ohms
on down to 8 these days. If Im not mistaken, PA systems use higher impedence
loads to limit the current drawn from the system.

Lets stop the misinformation here. I wasn't referring to the OP at all, all previous
posts have snips of the question I was answering.


Do you own a stereo? Do you understand what I'm talking about at all??!?! That is my
only question. If there is any other way of doing what I'm suggesting, why doensn't
anyone else do it?

Like I said above, youre thinking high end hifi, not high impedence
communication audio amplifiers.

Just like the thread about 50hz vs 60hz motors, oh my, don't even get me started on that
one. So much WRONG information, I only wish I jumped in on that one.

Not gonna comment on that.
Brian

 

[Switch]

Again, 8 ohms was not mentioned in the original post. 1000 ohms was the
load. For all you kids out there that dont know it, there is a lot of older
equipment that use higher impedence output audio. It can range from 6k ohms
on down to 8 these days. If Im not mistaken, PA systems use higher impedence
loads to limit the current drawn from the system.

Yep, you'd be mistaken

PA systems run in very low impedance

2 ohms is common thru to 8 ohms. Only high frequency drivers use 16ohms as nominal
impedance. Series Parallel is never used on low frequency transducers.

Qsc Audio, Crown, Carver, Bryston, Crest, BGW, Peavey, all manufacturers of power amps for
PA use. All have minimum impedance of 2ohms, and typically, a dual 18" subwoofer has a 4
ohm impedance (2 8ohm 18" drivers in parallel)

Ever put a cap across a speaker load? Introduces harmonics that aren't supposed to be
there, even at low power levels. Ummmm??

 

[Switch]

Doesnt matter, its not your job to tell people what to do. You can explain
the rules, but assuming to be the boss doesnt make you someones boss kid.

Contrary:

abuse of the usenet can be reported to your isp for traceroute. Everyone (even dynamic)
IP addresses get authenticated.

Usually [email protected] fill in your isp. (ie: someone posting illegal material in
newsgroups can't get away with it, hate mongerers etc...)

Please understand that your post appears to not only this newsgroup, it gets posted on
almost every electronics website with a forum, that means, MILLIONS of people get to see
your top post.

http://www.faqs.org/faqs/usenet/posting-rules/part1/ (just an example, try google)

Read up sometime, not following the rules doesn't mean you're better than anyone else.

 

[Switch]

No, you are the one who is mistaken.



Real PA systems use what is needed for the job at hand.


You are confusing musical equipment with real "PA" equipment. It is
meant for portable setups with short cables, and temporary use.

These are not musical equipment, they are power amplifiers, the SAME type of amp you can
drive a 70V speaker system with, just put a transformer on the output of the amp!!!!! duh.

Those are not the only "PA" amps. There are a lot of 25V, 70V, and
100V constant voltage systems which are high impedance. Tell me how far
you can run 200 watts at 2 ohms?

read below, 200watts at 2ohms is quite low power, several hundred feet with the
appropriate AWG wire. I've installed ElectroVoice MTL-4 (2ohm sub cabinet uses 4 18"
woofers in a manifold/bandpass box), with a 1800W/ch power amplifier using 10AWG wire in a
nightclub over 200 feet. The damping was only slightly affected because the amplifier had
a damping factor of >2000, amplifiers with low damping factors cannot dampen the speakers
over a long distance of wire. Read below for an explanation of damping.

A 70 volt system would be 5000/200 or

25 ohms. which can stand a five ohm loop resistance better? How about a
25 watt speaker with a 3000 foot loop? <I didn't really understand your question here,

impedance matching is all done in parallel, each speaker down the line is on a transformer
that has tappings.

You're absolutely correct, except the way a 100V or 70V system works is if you have a 100W
amp, you can run (10) 10W speakers. Impedance isn't typically necessary to calculate,
wire size isn't even a factor, you can use 16AWG, 18, heck, even 24AWG will do it!!

Yes, the wire length does make a difference, my company happens to install the stuff on a
regular basis into hotels, restaurants, banquet halls, etc...

The impedance of a 70V system is irrelevant because of how high the impedance is, as well
as there won't be any noticable difference when you remove or add speakers in the line.

70V is pretty much the standard for North America. I buy 100V systems from Europe, same
difference, just higher voltage.

The speakers are still 8-16 ohms on the other end, the matching transformers are tapped so
you can select the W, typically .5,2,4,8,20 watts being the highest as most transformers
start to saturate at high power levels (including those being produced by the amp).

A Crown MacroTech 3600 (which is a stereo power amp typically driving 2-8ohm loads) in
bridge mode can run 100 10W tapped speakers without worry about the "head" transformer
getting saturated, because it can run right off the amp into all your tapped speakers down
the line.


70V and other transformer speaker loads are not capable of playing full range (20-20Khz).
They are low power.

You can typically drive a 2500W/ch stereo amp at 2ohms using 10AWG wire about 200feet. At
this distance, the damping factor is way out of wack, which means the amplifier has very
little control over what the driver is doing. A short wire run from an amp creates the
highest damping possible, when the music stops playing (bass hit), the amp will control
the speaker and it will not 'flop' around.

In this case of high power, it is desirable to put the amplifier behind the speaker
stacks, run balanced XLR signal cable out to the amps (up to a maximum of 1000 feet
without distribution amplifiers), and voila.

200 watts is super low power. A Crown MacroTech 5000 is 5000W bridged into a 4ohm load
using a 220V/30A supply and has such a high damping factor, that if you use 8AWG wire, you
could literally blow up any speaker load you put on it.
The use of such an amp is strictly for driving low frequency cabinets.

I've been doing professional audio in North America for the past 25 years.


PA means public address, 25,000 screaming concert goers, or a million people at the
Million Man March still need to hear, heheh, I don't think we'd use 70V systems in that
case.

Little known fact, 70V and similar audio systems make up for 80% of the sales of
professional audio equipment, may even be more now!

 

[Brian Oakley]

Contrary:

abuse of the usenet can be reported to your isp for traceroute. Everyone (even dynamic)
IP addresses get authenticated.

Usually [email protected] fill in your isp. (ie: someone posting illegal material in
newsgroups can't get away with it, hate mongerers etc...)

Please understand that your post appears to not only this newsgroup, it gets posted on
almost every electronics website with a forum, that means, MILLIONS of people get to see
your top post.

http://www.faqs.org/faqs/usenet/posting-rules/part1/ (just an example, try google)

Read up sometime, not following the rules doesn't mean you're better than

anyone else.

As I said in my last post, its not your job to tell someone what to do. You
may explain the rules but youre attempting to be the boss is inappropriate.
If you dont like the way I post, youre free to complain to whomever you
wish, but you dont have the right to tell anyone what to do.
Brian Oakley

 

[Winfield Hill]

Switch wrote...

Anything less than 6db/octave is useless in audio.

This is wrong. There are many uses of 6dB/octave or lower
response slopes, such as in areas of feedback stabilization,
line equalization, signal processing, etc. And a -3dB/octave
filter is the easiest way to make pink noise from white noise.
Although it may not seem so to some, pink noise generation is
an important capability to many audio experts. Plus it makes
a great background-masking sound for sleeping.

Thanks,
- Win

whill_at_picovolt-dot-com