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Old 18th July 2007, 20:10   #16
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Originally Posted by DerAlte View Post
Errr... umm... what's a "whiteapple"? Or is it something like the "CCBT" concept?

Silly old me, I even googled the term, and it doesn't seem anything comprehensible!
whiteapple = MacBook
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Old 18th July 2007, 20:53   #17
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whiteapple = MacBook
Thanks, @Hydrashok, I had suspected so. Navin-ji was referring to "limited capabilities", which led to the doubt. Too many googlies going around - better to check.
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Old 18th July 2007, 21:04   #18
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Originally Posted by santosh.s View Post
Forgot the "Q" discussion on the other thread so soon? Open is like having no amp-damping at all (for that particular coil), while short is like making it as good as it can get.
"Ek to karela, oopar se neem chadha". I thought I had understood that, but it will take me a while to remember it like the EO's. I was limiting my thinking to the sub, didn't look at it from the amp p-o-v. Bhimrati!

But: Open voice coil has nothing to with the amp - no connection. Forget amp Q.

My surmise was the effect on the mechanical system by the shorted-coil sub-system (2nd coil traverses magnetic field, current generated in coil, causes magnetism in other direction, acts against the main coils' motive force. Ergo, damping). I couldn't see the connection between the (isolated, shorted) 2nd coil and the driver's Qes, which is linked with the main current carrying coil.
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Old 18th July 2007, 23:33   #19
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Originally Posted by DerAlte View Post
didn't look at it from the amp p-o-v. Bhimrati!

But: Open voice coil has nothing to with the amp - no connection. Forget amp Q.
Amp as such has no role in the damping, only it's o/p impedance matters. I mentioned the word "amp" just because it is popularly known as an amp's spec (damping factor!).

Quote:
My surmise was the effect on the mechanical system by the shorted-coil sub-system (2nd coil traverses magnetic field, current generated in coil, causes magnetism in other direction, acts against the main coils' motive force. Ergo, damping). I couldn't see the connection between the (isolated, shorted) 2nd coil and the driver's Qes, which is linked with the main current carrying coil.
Agree, it shouldn't affect the connected coil (and hence Qes). But the damping effect surely will be observed and it will implicitly modify Qms, and thereby Qts.

BTW, that is leading me back to basics- any conducting object moving in magnetic field should give rise to damping effect... that means speakers with metal formers should have its own damping effect. Anyway, everything should indirectly get factored in the Qms.

AFAIK, the same principle is used in eddy current braking, also seen in fitness bikes/ellipticals which claim smooth & silent "magnetic" technique instead of belt-friction.

Last edited by santosh.s : 18th July 2007 at 23:35.
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Old 19th July 2007, 07:05   #20
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Hi thanks for the suggestions, specially bridging the 4 channels into pairs and driving each voice coil of the sub. But I already have connected the rear speakers through a pair of channels. However I will try out what Navin had advised. Also one more query the amp is rated at continous power of 55Watt RMS at 4 ohms X 4 channels and the subwoofer is rated at nominal =400Watts and max=1000 watts. If I connect the left and right channels of the rear pair of the amp to the two individual voice coils, will 55Watts RMS per voice coil be sufficient to drive the sub rated at nominal 400Watts. Also how about connecting a resistor of say 2 ohms in series to a speaker to increase its impedence from 2 ohms to 4 ohms ???. Sorry If it is a stupid question as I am not very clued up with all these resistor-capacitor mumbo jumbo. Cheers
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Old 19th July 2007, 10:55   #21
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Originally Posted by santosh.s View Post
the damping effect surely will be observed and it will implicitly modify Qms, and thereby Qts.
Sure, Navin was correct in his observation on the lowering effect on F3 and roll-off.

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Originally Posted by santosh.s View Post
BTW, that is leading me back to basics- any conducting object moving in magnetic field should give rise to damping effect... that means speakers with metal formers should have its own damping effect. Anyway, everything should indirectly get factored in the Qms.
Not ANY conducting object - there has to be an electrical path for current produced by the magnetic field traversal to flow.

The alu former is 1 shorted turn effectively, and the damping, though non-zero, is but insignificantly finite compared to the large motive force of the voice coil.

Shorting the second coil, which has same number of turns as the driven coil, is producing significantly more damping (the magnetic field of the 2nd coil is much much weaker than BL so they don't totally cancel out; also, it is complex interplay, the waveforms will not synchronize time-wise, 2nd coil is lagging).

Quote:
Originally Posted by santosh.s View Post
AFAIK, the same principle is used in eddy current braking, also seen in fitness bikes/ellipticals which claim smooth & silent "magnetic" technique instead of belt-friction.
Yes, same principle as eddy-current braking and "regenerative" braking used in hybrid / electric cars and fitness machines.
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Old 19th July 2007, 11:06   #22
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Originally Posted by Lifewater View Post
Also one more query the amp is rated at continous power of 55Watt RMS at 4 ohms X 4 channels and the subwoofer is rated at nominal =400Watts and max=1000 watts. If I connect the left and right channels of the rear pair of the amp to the two individual voice coils, will 55Watts RMS per voice coil be sufficient to drive the sub rated at nominal 400Watts. Also how about connecting a resistor of say 2 ohms in series to a speaker to increase its impedence from 2 ohms to 4 ohms ???. Sorry If it is a stupid question as I am not very clued up with all these resistor-capacitor mumbo jumbo. Cheers
There are no stupid questions, @lifewater, only stupid answers.

Bridging 2 channels of 55W rms nominal will produce 110W rms. Even though this is looks low compared to the 400W rms of the sub, it will produce substantial thump. 400Wrms is "nominal power handled" and will produce a really big THUMP if driven at that level. But, since your ears' ability to differentiate power is logarithmic, you will not notice the difference in the car normally, the bystanders outside would.

Now who are you playing the music for? If only for yourself, it is not bad. If it is for others, maybe a monoblock 300Wrms would be better. 600Wrms in moderation (whatever that means to you) EVEN better - but might fry your sub if you are pushing 1000W peaks too often. Your choice. I would recommend doing it step by step and stopping when you are satisfied with the loudness levels.

The 2 ohms resistor will only warm the interiors of the car, but not produce any sound, sir.

Last edited by DerAlte : 19th July 2007 at 11:08.
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Old 19th July 2007, 11:18   #23
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Quote:
Originally Posted by DerAlte View Post
Errr... umm... what's a "whiteapple"? Or is it something like the "CCBT" concept?

Silly old me, I even googled the term, and it doesn't seem anything comprehensible!
Quote:
Originally Posted by hydrashok View Post
whiteapple = MacBook
Quote:
Originally Posted by DerAlte View Post
Thanks, @Hydrashok, I had suspected so. Navin-ji was referring to "limited capabilities", which led to the doubt. Too many googlies going around - better to check.
Ehhhh... Not too fast Anoop! You're wrong there!!! Just think why will Sam's posting capabilities be hurt because he's typing on his Mac Book???

Der Alte - Think opposite of what Navin posted, more specifically on the lines of "Black" & "Berry"

And needless to say the Old Man of ICE has a very wicked sense of humour!!
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Old 19th July 2007, 11:59   #24
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Originally Posted by hydrashok View Post
whiteapple = MacBook
Nope the techies call them Blackberries or something like that. Irratiating little devices. My tech friends are litterally all thumbs nowadays even at the dinner table. Hate them so I figured calling them any coloured fruit would do. So that we are no confused next time i'll call it a pink mango ok?

Last edited by navin : 19th July 2007 at 12:07.
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Old 19th July 2007, 12:08   #25
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Originally Posted by iraghava View Post
And needless to say the Old Man of ICE has a very wicked sense of humour!!
Der Alte is the new Old Man!

Wicked? I thoight it was just plain warped. esp if I use Hindi.
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Old 19th July 2007, 12:10   #26
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Originally Posted by DerAlte View Post
The alu former is 1 shorted turn effectively
I think you are underestimating it by counting it as just 1 turn. The net effect will not only dependent upon the number of turns but the current carrying capacity of each one of them. 1 turn@10A = 5 turns@2A = 10 turns@1A. Think of the Aluminum former as comprising of a number of turns wound like a coil, but without insulation! The number of turns to be assumed here is up to you, but the net result is guaranteed to be the same. Now, do you think it will be very negligible as compared to the copper voice coil? I don't think so.
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Old 19th July 2007, 12:17   #27
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Originally Posted by iraghava View Post
Ehhhh... Not too fast Anoop! You're wrong there!!! Just think why will Sam's posting capabilities be hurt because he's typing on his Mac Book???
Quote:
Originally Posted by navin View Post
... So that we are no confused next time i'll call it a pink mango ok?
Another case of 1 + 1 = 11 from me (duh!)

You forgot to say "Elementary, my dear Watson", Ishaan
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Old 19th July 2007, 13:24   #28
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Originally Posted by DerAlte View Post
Bridging 2 channels of 55W rms nominal will produce 110W rms.
If the amp is 55 watts rms in 4 ohms then if we go in theory the the specs will be

55 x 4 at 4 ohms
110 x 2 at 8 ohms
220 x 2 at 4 ohms
440 x 2 at 2 ohms

but in this world nothing is perfect . as the output section is weak or the power supply section is weak which makes them lose the output...but here is a example of a solid amp...

Gt-trading - Attivitą


Power 4 ohm stereo Watt RMS - 11 to 14,4 Volt -> 50 x 2
Power 2 ohm stereo Watt RMS - 11 to 14,4 Volt ->100 x 2
Power 1 ohm mono Watt RMS - 11 to 14,4 Volt -> 200 x 2
Power 0,5 ohm mono Watt RMS - 11 to 14,4 Volt -> 375
Power 0,25 ohm stereo Watt RMS - 11 to 14,4 Volt -> 700
Power 4 ohm mono Watt RMS - 11 to 14,4 Volt -> 200
Power 2 ohm mono Watt RMS - 11 to 14,4 Volt -> 400
Power 1 ohm mono Watt RMS - 11 to 14,4 Volt -> 750
Power 0,5 ohm mono Watt RMS - 11 to 14,4 Volt -> 1400
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Old 19th July 2007, 14:14   #29
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Originally Posted by low_bass_makker View Post
If the amp is 55 watts rms in 4 ohms then if we go in theory the the specs will be

55 x 4 at 4 ohms
110 x 2 at 8 ohms
220 x 2 at 4 ohms
440 x 2 at 2 ohms

but in this world nothing is perfect . as the output section is weak or the power supply section is weak which makes them lose the output...but here is a example of a solid amp...
More theory...
Power, P = (Voltage, V)^2 / Resistance, R.
Since you are getting a constant voltage in the car amp (might vary from 11V to 14.4 volts.. but for our theory sake lets take it 12V), you get a varying power output for different resistance (R) that is connected to it..
When you bridge the channels, you are basically doubling the available Voltage (eg. +12V to -12V).
When applied to the above formula you get
P = (2V)^2 / R ==> P = 4 V^2/R
==> P = 4 P0 where P0 is the initial power output...
So there you go.. in theory you get 4 times the power output than from a individual channel.
But like LBM has mentioned but in this world nothing is perfect .
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Old 19th July 2007, 19:50   #30
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The alignment of the stars is not favourable today.
Quote:
Originally Posted by navin View Post
Der Alte is the new Old Man!
Wicked? I thoight it was just plain warped. esp if I use Hindi.
Navin, you are "the Old Man of ICE", I'm just plain "Old Man"!
You *should* have tried it in Hindi.
PinkMango would be an Open Source, Linux based device

Quote:
Originally Posted by santosh.s View Post
I think you are underestimating it by counting it as just 1 turn. The net effect will not only dependent upon the number of turns but the current carrying capacity of each one of them. 1 turn@10A = 5 turns@2A = 10 turns@1A. Think of the Aluminum former as comprising of a number of turns wound like a coil, but without insulation! The number of turns to be assumed here is up to you, but the net result is guaranteed to be the same. Now, do you think it will be very negligible as compared to the copper voice coil? I don't think so.
Ahem, OEO!
Without insulation that makes it 1 single shorted turn (even if you assume separation, it assumes insulation). And not current carrying capacity, but instantaneous current produced by the magnetic field traversal. The alu former's current capacity is quite large (check longitudinal cross-section area of the former)
* The voltage produced by mag field traversal is proportional to the LENGTH of conductor in the mag field (hence number of turns) and speed of traversal (technology of old electric cigarette lighters, long before quartz-based ones)
* The current in the coil is proportional to this voltage, the motive force applied and the load: the principle of electric generators
* When shorted, the load is the effective resistance of the coil itself
Exact inverse of this is Motors (that's what drivers are): push current through a coil by applying voltage, which produces a magnetic field, which pushes against the mag field of the magnet and pushes the cone. Greater the dv/dt or di/dt, faster the deflection (the battery test).

Quote:
Originally Posted by low_bass_makker View Post
If the amp is 55 watts rms in 4 ohms then if we go in theory the ... Power 0,5 ohm mono Watt RMS - 11 to 14,4 Volt -> 1400
Bhai-ji, BRIDGED!
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