# High power inductor

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Sean

June 10, 2004 8:43:42 AM

Archived from groups: rec.audio.high-end (More info?)

Hi all,

I'm doing some crossover calculations for my 4-way, 2000 watt speakers

that I'm planning on building and of course the first roadblock is the

very large physical size of the inductor coils that will be necessary

to split the sub and the mid-bass at 300 Hz. I would very much

appreciate some advice on how to create a 12 mH inductor in the

smallest amount of space possible, and still can safely handle about

1500 watts. I've seen different types of cores that can be used to

reduce the number of windings but I've also heard of the various

acoustical drawbacks to having non-air cores, and so I'm hoping that

there's an alternative out there. Anybody have some ideas?

thanks in advance,

Sean

Hi all,

I'm doing some crossover calculations for my 4-way, 2000 watt speakers

that I'm planning on building and of course the first roadblock is the

very large physical size of the inductor coils that will be necessary

to split the sub and the mid-bass at 300 Hz. I would very much

appreciate some advice on how to create a 12 mH inductor in the

smallest amount of space possible, and still can safely handle about

1500 watts. I've seen different types of cores that can be used to

reduce the number of windings but I've also heard of the various

acoustical drawbacks to having non-air cores, and so I'm hoping that

there's an alternative out there. Anybody have some ideas?

thanks in advance,

Sean

More about : high power inductor

Anonymous

June 11, 2004 5:08:57 AM

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:2GRxc.74236$Ly.52521@attbi_s01...

> Hi all,

>

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz.

First off, I'd be curious as to why you would cross a sub at such a high

frequency. 100Hz or lower is more common. In a 3 way system 300 Hz would

be about right, but not IMO, for a subwoofer.

I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

>

You can pick up a copy of AudioXpress and check the ads for custom winding,

or do what I beleive is more practical and go to Adire Audio's web site and

check out their subwoofer amps. www.adireaudio.com .

They offer several amps for sub use and 2 in particular that should meet

your needs quite well, the HS 500 at 750Watts at 4 ohms for $629.00 or the

HS 1400 with 1400 Watts for $899.00. They both have electronic xovers and

therefore eliminate the need for inductors of any size.

> thanks in advance,

> Sean

>

Your welcome.

wendy

June 11, 2004 5:20:02 AM

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz. I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

> thanks in advance,

> Sean

Use active filter and separate amplifiers. It is a bloody waste of energy

to use passive networks with such powers. What is more, your sound will

improve dramatically.

Grtx, Wendy

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Anonymous

June 11, 2004 8:17:50 AM

On 6/10/04 12:43 AM, in article 2GRxc.74236$Ly.52521@attbi_s01, "Sean"

<delphiconsultingguy@yahoo.com> wrote:

> Hi all,

>

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz. I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

Large fans? If you are planning on running that amount of power - the coil

is likely to get really hot - making a fan work much better.

Anonymous

June 11, 2004 4:56:54 PM

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:2GRxc.74236$Ly.52521@attbi_s01...

> Hi all,

>

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz. I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

With that kind of power, ferrite cores will saturate like crazy. An air core

is possible but it will be huge, and I don't think any are made that big

commercially. 12 mH transformer cored inductors are readily available and

they might be your best bet. I'd suggest you have a word with a manufacturer

of transformer cored inductors regarding power handling. You might be lucky.

Stephen

Sean

June 12, 2004 3:46:12 AM

Hi all again,

I appreciate all the advice so far but I'm hell-bent on making a

passive crossover for this setup. If someone can please tell me how

to get the highest inductance possible in the smallest space possible,

or perhaps suggest a completely different mechanism for adding

inductance to a circuit, I'd be most grateful.

thanks again,

Sean

Anonymous

June 12, 2004 8:57:01 PM

Sean,

I'm not sure where you are getting the 1500 Watt figure for the

inductor power handling. If it needs to handle that much power, your

speaker cables may melt long before the inductor is bothered. Let's

assume an inductor with a DC resistance (DCR) of 0.75 Ohms (i.e., at

low frequencies). If it must handle 1500 Watts, this equates to a

current through the inductor of:

square root (1500 / 0.75) = about 45 Amps

If that power is being consumed by the inductor, then your speaker

cable needs to pass that current on to the inductor.

I suggest looking at this another way. Let's assume that the 12 mH

inductor you've described will be in series with your low frequency

driver, perhaps as part of a 2nd order LC filter (especially since any

inductor in the high frequency driver path should very likely be of

much smaller value). Now start with your low frequency loudspeaker

driver, which you intend to feed 2000 Watts (I assume peak). If it's

an 8 Ohm driver, the maximum current requirement for the driver would be:

square root (2000 / 8) = about 16 Amps

and the maximum voltage across the driver would be:

square root (2000 x 8) = about 130 Volts

Thus at low frequencies, you'll have at most 16 Amps flowing through

your speaker cables and through any in-line (i.e., in series)

inductor. And with a music signal, the average signal power level

will be much lower:

- about 10x lower for rock music (200 Watts, 5 Amps, 40 Volts)

- about 30x lower for jazz (75 Watts, 3 Amps, 25 Volts)

- about 50x lower for classical (40 Watts, 2.2 Amps, 18 Volts).

At 0 Hz an inductor with 0.75 DCR in series with an 8 Ohm loudspeaker

driver need handle only:

16 x 16 x 0.75 = about 200 Watts

At a crossover frequency of 300 Hz, the inductive reactance of the 12

mH inductor will be:

2 x pi x 300 x 0.012 = 22.6 Ohms

and, ignoring any capacitor for now, the impedance of the inductor-low

freq driver leg as seen by the amplifier will now be:

22.6 + 8.0 = 30.6 Ohms

with a maximum current flow of:

130 Volts / 30.6 Ohms = 4.25 Amps

giving an inductor power requirement of:

4.25 x 4.25 x 22.6 = about 410 Watts

These are peak power levels. As noted above, your average power

levels will be 10-50x lower depending on the type of music. This does

not seem to be a particularly onerous requirement as long as you pay

attention to saturation issues at peak power. Potential sources:

http://www.alphacore.com/inductor.htm [12 GA, foil, air core - they

can probably make a custom 12 mH inductor for you, but it will be

large, expensive and heavy]

http://www.madisound.com/inductors.html [15 GA, permeable steel core -

they don't say what the power handling is on these before saturation,

but you can call and ask; if it's under 450 Watts you can always buy 4

of their 12 mH inductors, connect two each in parallel, then connect

the two parallel sets in series for an equivalent 12 mH inductor with

4x the power handling capability]

If you are looking for a maxed out solution at reasonable cost, you

can go with the second choice here and use the suggested 4 inductors

per side in a series-parallel connection for lots of headroom before

saturation - cheap at $65.00 per equivalent inductor, and likely able

to handle a full 1500 Watts or better with ease. This would probably

cost you 1/3 of the equivalent AlphaCore air core inductor, be much

lighter, have half the DCR, and have a smaller footprint.

Best regards,

Terry

Sean wrote:

>

> Hi all,

>

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz. I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

>

> thanks in advance,

> Sean

Anonymous

June 12, 2004 8:57:42 PM

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:cadg8404v6@news3.newsguy.com...

> Hi all again,

>

> I appreciate all the advice so far but I'm hell-bent on making a

> passive crossover for this setup. If someone can please tell me how

> to get the highest inductance possible in the smallest space possible,

> or perhaps suggest a completely different mechanism for adding

> inductance to a circuit, I'd be most grateful.

>

> thanks again,

> Sean

As I said before, pick up a copy of audio and check the ads, or check with

the DIY places like Madisound, Speaker City, and Zalytron.

If they can't help you directly, they will know who can.

Now, lets assume you get what you want, this is going to be a stand alone

sub or part of a single box system? Maybe something like one of the side

fire models? If it's going to be stand alone, why 300 Hz? Free standing

subs are useful because they can be positioned for best flat response. To

do that they need low crossover points, lower than 300 Hz.

I'm very curious as an sometime DIYer why that crossover point, particularly

if it's a free standing sub.

ban

June 12, 2004 8:58:39 PM

Sean wrote:

> Hi all again,

>

> I appreciate all the advice so far but I'm hell-bent on making a

> passive crossover for this setup. If someone can please tell me how

> to get the highest inductance possible in the smallest space possible,

> or perhaps suggest a completely different mechanism for adding

> inductance to a circuit, I'd be most grateful.

>

> thanks again,

> Sean

Sean,

your approach and the level of your understanding guarantees an acoustical

desaster with these speakers. You have to take in account the

interdependence of your speaker and the xover components. The loudspeaker

resonance will alter the desired characteristic or has to be compensated.

The baffle size will strongly influence the radiation in the midrange. All

this can be calculated and simulated. I suggest the very good simulation

software Akabak. To operate this software will require a steep learning

curve.

A coil is just that- a wire wound many times in a circle. If you use air

core, which means there is no saturation with higher current and the

inductivity will stay constant, you need a lot of turns. since this is the

case you have to use a big diameter wire. There is no trade off with space

and cost. If you want a 12mH choke, the cost for a ready made unit will be

around 200 bucks for the amount of current (20Arms with 4R speakers). There

are ways to make crossovers to use only 1 coil both for the highpass and

lowpass. But again simulation will be needed to find the right values.

The midrange will need a lowpass and a highpass in series. Both will

influence each other and additionally interact with the speaker impedance.

Only a lengthy simulation can find the optimal values.

Another problem will be the capacitors. Forget about electolytics, this

amount of power needs a lot of paralleled MKT foil capacitors, I have here a

47uF/160V in the size of a coffee mug, and you will need a couple of them.

If you do a 3-way xover you will need at least 500 bucks in parts and

lengthy simulation and measuring.

The loudspeaker measuring hard- and software will be pricey and it will take

a long time to get reasonable results. I want to encourage you though to go

this way, it is satisfying to learn and understand this matter when you like

music.

--

ciao Ban

Bordighera, Italy

http://www.pupazzo.page.ms/

Anonymous

June 13, 2004 5:47:48 PM

On Thu, 10 Jun 2004 04:43:42 GMT, delphiconsultingguy@yahoo.com (Sean)

wrote:

>Hi all,

>

>I'm doing some crossover calculations for my 4-way, 2000 watt speakers

>that I'm planning on building and of course the first roadblock is the

>very large physical size of the inductor coils that will be necessary

>to split the sub and the mid-bass at 300 Hz. I would very much

>appreciate some advice on how to create a 12 mH inductor in the

>smallest amount of space possible, and still can safely handle about

>1500 watts. I've seen different types of cores that can be used to

>reduce the number of windings but I've also heard of the various

>acoustical drawbacks to having non-air cores, and so I'm hoping that

>there's an alternative out there. Anybody have some ideas?

>

>thanks in advance,

>Sean

OK, here goes:

inductance in uH is: (.315 * r * r * N * N)/(6r + 9l +10d)

r is radius in cm

N is # of turns

l is length of coil (cm)

d is depth of winding (cm)

let's use 5 cm for radius, 10 cm for length, 1 cm for depth (this is a

guesstimate). Set inductance to 12000 (in uH), solve for N. I get 89

turns (which is not all that bad)!.

Now take the 89 turns, convert it to legth (89 * 2pi * r), convert

to feet, and I got 91.7 feet. Resistance for 91 ft is:

14 AWG: .23 ohms

12 AWG .14 ohms

10 AWG .09 ohms

Assume your current is 20 amps (that is a grossly high estimate,

because it assumes you are running the amp flat out). I also assume

your speaker resistance is about 4 ohms. Power dissipated by the coil

would be:

14 AWG: about 90w

12 AWG: 60w

10 AWG: 37w not too bad for the size of coil, but give it

room to dissipate heat. My guess is that it

would run 60-100 degrees Celcius. There isn't much

to happen if it gets too hot, as long as it doesn't char or catch

something on fire. By that time your voice coil will be flaming!

Since you seldom run a speaker flat out (what do think would happen

to your voice coil with 1500 watts across it for 20-30 sec.), you

could assume a current of, say 10 amps, then because power is

proportional to current squared, you could reduce the above powers by

4.

The inductor is not all that atrocious. Due to the high powers

involved, I'd recommend some form of sustained overcurrent protection.

If you DID put 20 amps continuous into this system, there are

possibilities of fire! Use a coil form that is not flammable (and not

metallic). I would also put a breaker on the power amp, on the 110 or

220 volt supply, and have it trip at say, 500 W. That way the amp can

deliver its peak powers without problem but will trip if the sustained

power exceeds 500 W (which is going to sound pretty rough, because of

the limited headroom).

-Paul

................................................................

Paul Guy

Somewhere in the Nova Scotia fog

Anonymous

June 13, 2004 8:42:23 PM

Keep in mind that the room will also have an effect on the speaker's

impedance. I had good results before by building the speakers first, putting

them in place, measuring what I ended up with and then designing the

crossover. Something no manufacturer can give you.

"Ban" <bansuri@web.de> wrote in message

news:3DGyc.32803$HG.2253@attbi_s53...

> Sean wrote:

> > Hi all again,

> >

> > I appreciate all the advice so far but I'm hell-bent on making a

> > passive crossover for this setup. If someone can please tell me how

> > to get the highest inductance possible in the smallest space possible,

> > or perhaps suggest a completely different mechanism for adding

> > inductance to a circuit, I'd be most grateful.

> >

> > thanks again,

> > Sean

>

> Sean,

> your approach and the level of your understanding guarantees an acoustical

> desaster with these speakers. You have to take in account the

> interdependence of your speaker and the xover components. The loudspeaker

> resonance will alter the desired characteristic or has to be compensated.

> The baffle size will strongly influence the radiation in the midrange. All

> this can be calculated and simulated. I suggest the very good simulation

> software Akabak. To operate this software will require a steep learning

> curve.

>

> A coil is just that- a wire wound many times in a circle. If you use air

> core, which means there is no saturation with higher current and the

> inductivity will stay constant, you need a lot of turns. since this is the

> case you have to use a big diameter wire. There is no trade off with space

> and cost. If you want a 12mH choke, the cost for a ready made unit will be

> around 200 bucks for the amount of current (20Arms with 4R speakers).

There

> are ways to make crossovers to use only 1 coil both for the highpass and

> lowpass. But again simulation will be needed to find the right values.

> The midrange will need a lowpass and a highpass in series. Both will

> influence each other and additionally interact with the speaker impedance.

> Only a lengthy simulation can find the optimal values.

> Another problem will be the capacitors. Forget about electolytics, this

> amount of power needs a lot of paralleled MKT foil capacitors, I have here

a

> 47uF/160V in the size of a coffee mug, and you will need a couple of them.

> If you do a 3-way xover you will need at least 500 bucks in parts and

> lengthy simulation and measuring.

> The loudspeaker measuring hard- and software will be pricey and it will

take

> a long time to get reasonable results. I want to encourage you though to

go

> this way, it is satisfying to learn and understand this matter when you

like

> music.

> --

> ciao Ban

> Bordighera, Italy

> http://www.pupazzo.page.ms/

>

Anonymous

June 14, 2004 8:03:33 PM

High power inductor -- one of the critical elements of switch mode power

supply design is specification of the inductors -- if you can get it there

is a 2-part series of article in the amateur radio experimenter magazine

"QEX" (probably at a university library) -- Sept/Oct 2002 and Jan/Feb 2003

which goes through the math and core selection. You want to select a

material which won't saturate at the current you are pumpling thought. The

QEX series of articles explains the heat transfer which has to be dealt with

in coil design -- of course the problem is that at such high current the

wire size becomes problematic.

A good source for ferrite and iron core toroids is Amidon, Inc.

www.amidoncorp.com

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:2GRxc.74236$Ly.52521@attbi_s01...

> Hi all,

>

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers

> that I'm planning on building and of course the first roadblock is the

> very large physical size of the inductor coils that will be necessary

> to split the sub and the mid-bass at 300 Hz. I would very much

> appreciate some advice on how to create a 12 mH inductor in the

> smallest amount of space possible, and still can safely handle about

> 1500 watts. I've seen different types of cores that can be used to

> reduce the number of windings but I've also heard of the various

> acoustical drawbacks to having non-air cores, and so I'm hoping that

> there's an alternative out there. Anybody have some ideas?

>

> thanks in advance,

> Sean

>

Sean

June 15, 2004 2:16:11 AM

> If it's going to be stand alone, why 300 Hz?

Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and

my woofer is faithful down to 70, so I chose the happy medium in the

middle such that the power distribution is biased to the big speaker.

The final product I'm shooting for will be a pair of 4-way speakers

with the mid and tweeter being satellites (separate enclosure). Most

of the time though they will operate as a single stacked unit.

Anybody else feel I should lower the sub crossover point?

Ban, Thanks for the software recommendations, though I wouldn't mind

hearing from other people on this forum about how much I really have

to gain from this approach. I'm not looking for perfectly faithful

speakers in terms of intrinsic flatness (my apologies to audiophiles

out there), I'm merely looking to have a very, very loud set of

speakers that I don't mind digitally eq'ing the heck out of to flatten

the signal. In this light, the simulator and the accompanying

learning curve may be overkill.

Stephen, I did some research about cored inductors and found a lot of

information about transformers and inductors but I'm not sure if

there's some hybrid that you're specifically mentioning here.

Terry, I like the alphacores and will probably be pursuing that route

for my inductance needs. Your suggestion about parallel-serializing 4

small inductors seems only impractical in the sense that they still

individually need to be 12 mH each, meaning that there would be 4 very

large coils instead of 1 super-large one, but I think the super-large

one would still be smaller in net volume than the other 4 combined.

Not to mention $$$. I'm hoping that alphacore will be able to help me

out with a super-coil. Thanks for the links!

Sean

Anonymous

June 15, 2004 7:04:17 AM

On Sat, 12 Jun 2004 16:57:01 GMT, Zagar <openskyseven@comcast.net>

wrote:

>Sean,

>

........some stuff deleted.....

>

>At a crossover frequency of 300 Hz, the inductive reactance of the 12

>mH inductor will be:

>

> 2 x pi x 300 x 0.012 = 22.6 Ohms

>

>and, ignoring any capacitor for now, the impedance of the inductor-low

>freq driver leg as seen by the amplifier will now be:

>

> 22.6 + 8.0 = 30.6 Ohms

>

>with a maximum current flow of:

>

> 130 Volts / 30.6 Ohms = 4.25 Amps

>

>giving an inductor power requirement of:

>

> 4.25 x 4.25 x 22.6 = about 410 Watts

>

You cannot calculate dissipated power of an inductor by multiplying

its impedance by the current squared. The power dissipated by an

inductor (ignoring iron and eddy losses) is simply the current squared

times the DC RESISTANCE of the coil.

It is true that there is a power (stored energy) associated with

the reactive element (2*pi*f*L), but it does not release as heat, it

is released back into the circuit itself.

You can have an enormous reactive power, and yet get no heat. If I

place a good (oil) capacitor across 110 volts, I can draw several

amps, yet the capacitor will dissipate no heat. That is because the

current and voltage are 90 degrees out of phase - the product averages

out to zero.

I'd find it easier to use air coils, simply because there are

accurate formulae to determine the inductance, you don't need a

difficult core, and you never need to worry about saturation,

hysterisis, losses etc. It might use a few pounds of copper, but you

could always make a "pancake" style coil which would easily fit

against the inside of the cabinet. Once you have a large diameter

coil, it does not take a lot of turns to make up a high inductance.

However, you DO need a fair length of wire.

I'm assuming you did your homework and have determined the proper

crossover frequency, phase response, etc., for a smooth transition

with minimal phase or directional artifacts. I have pretty limited

familiarity with crossover technology, but it does not seem all that

simple. It is not as simple as determining impedance at crossover,

since you need to remember that both speakers are active at crossover,

and they have their own phase shifts, along with the fact that they

are separated by a distance that will cause effects at the listeners

position. If my memory serves me... you want a 4th order Linkowitz

network???? or something like that. I believe John Vanderkooy or/and

Stan Lipschitz from Waterloo did a fair bit of work with this. Dick

could probably fill you in with the relevant theory and history.

-Paul

................................................................

Paul Guy

Somewhere in the Nova Scotia fog

Anonymous

June 16, 2004 4:09:46 AM

Keep in mind that the room will also have an effect on the speaker's

impedance. I had good results before by building the speakers first, putting

them in place, measuring what I ended up with and then designing the

crossover. Something no manufacturer can give you.

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:Lspzc.35982$eu.12652@attbi_s02...

> > If it's going to be stand alone, why 300 Hz?

>

> Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and

> my woofer is faithful down to 70, so I chose the happy medium in the

> middle such that the power distribution is biased to the big speaker.

> The final product I'm shooting for will be a pair of 4-way speakers

> with the mid and tweeter being satellites (separate enclosure). Most

> of the time though they will operate as a single stacked unit.

> Anybody else feel I should lower the sub crossover point?

>

> Ban, Thanks for the software recommendations, though I wouldn't mind

> hearing from other people on this forum about how much I really have

> to gain from this approach. I'm not looking for perfectly faithful

> speakers in terms of intrinsic flatness (my apologies to audiophiles

> out there), I'm merely looking to have a very, very loud set of

> speakers that I don't mind digitally eq'ing the heck out of to flatten

> the signal. In this light, the simulator and the accompanying

> learning curve may be overkill.

>

> Stephen, I did some research about cored inductors and found a lot of

> information about transformers and inductors but I'm not sure if

> there's some hybrid that you're specifically mentioning here.

>

> Terry, I like the alphacores and will probably be pursuing that route

> for my inductance needs. Your suggestion about parallel-serializing 4

> small inductors seems only impractical in the sense that they still

> individually need to be 12 mH each, meaning that there would be 4 very

> large coils instead of 1 super-large one, but I think the super-large

> one would still be smaller in net volume than the other 4 combined.

> Not to mention $$$. I'm hoping that alphacore will be able to help me

> out with a super-coil. Thanks for the links!

>

> Sean

>

Anonymous

June 16, 2004 7:03:34 AM

"Sean" <delphiconsultingguy@yahoo.com> wrote in message

news:Lspzc.35982$eu.12652@attbi_s02...

> > If it's going to be stand alone, why 300 Hz?

>

> Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and

> my woofer is faithful down to 70, so I chose the happy medium in the

> middle such that the power distribution is biased to the big speaker.

> The final product I'm shooting for will be a pair of 4-way speakers

> with the mid and tweeter being satellites (separate enclosure). Most

> of the time though they will operate as a single stacked unit.

> Anybody else feel I should lower the sub crossover point?

>

A xover at 300 Hz does not IMO qualify as a subwoofer. A driver with an f3

of 70 Hz doesn't either.

A crossover at 300 hz should be to something like a midrange of about 5.5".

I think a 4 way may be overkill, but would very likely work well if the sub

is a real one crossed at 100 Hz or lower from a driver that can't go down to

20 Hz.

Eq is fine, but you need to consider excursion limits. A good 12'' sub like

the Adire Shiva can move a lot of air with bottoming out and play loud as

hell, without EQ. A lesser woofer, may blow itself out out it's voicecoil

if it isn't built for big xmax.

> Ban, Thanks for the software recommendations, though I wouldn't mind

> hearing from other people on this forum about how much I really have

> to gain from this approach. I'm not looking for perfectly faithful

> speakers in terms of intrinsic flatness (my apologies to audiophiles

> out there), I'm merely looking to have a very, very loud set of

> speakers that I don't mind digitally eq'ing the heck out of to flatten

> the signal. In this light, the simulator and the accompanying

> learning curve may be overkill.

>

> Stephen, I did some research about cored inductors and found a lot of

> information about transformers and inductors but I'm not sure if

> there's some hybrid that you're specifically mentioning here.

>

> Terry, I like the alphacores and will probably be pursuing that route

> for my inductance needs. Your suggestion about parallel-serializing 4

> small inductors seems only impractical in the sense that they still

> individually need to be 12 mH each, meaning that there would be 4 very

> large coils instead of 1 super-large one, but I think the super-large

> one would still be smaller in net volume than the other 4 combined.

> Not to mention $$$. I'm hoping that alphacore will be able to help me

> out with a super-coil. Thanks for the links!

>

> Sean

>

Anonymous

June 19, 2004 6:35:15 PM

Paul Guy wrote:

>

> On Sat, 12 Jun 2004 16:57:01 GMT, Zagar <openskyseven@comcast.net>

> wrote:

>

> >Sean,

> >

> .......some stuff deleted.....

>

> >

> >At a crossover frequency of 300 Hz, the inductive reactance of the 12

> >mH inductor will be:

> >

> > 2 x pi x 300 x 0.012 = 22.6 Ohms

> >

> >and, ignoring any capacitor for now, the impedance of the inductor-low

> >freq driver leg as seen by the amplifier will now be:

> >

> > 22.6 + 8.0 = 30.6 Ohms

> >

> >with a maximum current flow of:

> >

> > 130 Volts / 30.6 Ohms = 4.25 Amps

> >

> >giving an inductor power requirement of:

> >

> > 4.25 x 4.25 x 22.6 = about 410 Watts

> >

>

> You cannot calculate dissipated power of an inductor by multiplying

> its impedance by the current squared. The power dissipated by an

> inductor (ignoring iron and eddy losses) is simply the current squared

> times the DC RESISTANCE of the coil.

> It is true that there is a power (stored energy) associated with

> the reactive element (2*pi*f*L), but it does not release as heat, it

> is released back into the circuit itself.

Thanks for pointing this out. The sources I've read to date have

really not delved into this, but had led me to believe that the

reactance values could be used in the power formula when dealing with

a 2-port component. I'd appreciate any reference you can provide here

for my future use.

> You can have an enormous reactive power, and yet get no heat. If I

> place a good (oil) capacitor across 110 volts, I can draw several

> amps, yet the capacitor will dissipate no heat. That is because the

> current and voltage are 90 degrees out of phase - the product averages

> out to zero.

With an AC signal, I agree that it averages to zero, but I was trying

to deal with worst case peak values to make a point to Sean. If there

are two sine waves 90 degrees out of phase, at regular intervals their

product will have an absolute peak value of 0.5 (=0.707 x 0.707),

which would have put my 300 Hz calculation off by a factor of 2 too high.

Best regards,

Terry

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