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Multi-Way Conventional loudspeakers with crossovers

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Old 18th January 2013, 04:50 PM   #11
Mooly is offline Mooly  United Kingdom
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It is getting confusing as to what you are actually doing.

Are you feeding the output of the filter into an amplifier ? This circuit isn't meant to feed a speaker directly.

Your problems will all come down to the signal levels you are feeding into the circuit and what you are connecting the output of the circuit too.

Tell us exactly what the circuit is connected to.
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Old 18th January 2013, 05:12 PM   #12
pranab is offline pranab  India
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Quote:
Originally Posted by cT equals piD View Post
Either the videos and forums are incorrect or you have misunderstood the information. A sub-woofer (passive speaker system) generally has impedance of 10 Ohm or less. With a 1 k Ohm resistor in series with the sub-woofer, the woofer at any frequency does not receive more than 1/10th of the voltage applied across the resistor-woofer in-series.

That is, exactly what the previous post says.

Regards,
Pete
It is possible that the videos and forums may have incorrect information or or or I may have misunderstood it but the video which shows LPF making and testing seems to be working perfectly ............... I am really very thankful for giving me the information that 1 KOhm resistor will definitely Block most of the voltage and this is the reason when i hook up my home made circuit why the 90% of the volume goes off.......
If we keep all the questions aside .... I have only one question ...How can i make a simple thing that blocks the mids and highs from my subwoofer (circuit shud be passive)
Kindly help me , I have even searched the whole market for a Low Pass Filter Or a 2 Way Crossover but it is impossible to find something like this in India where people havnt heard words like LPF and Crossover.
Lemme tell you guys one thing that it was nearly impossible to actually find a Sub-Woofer at my place. After searching for so many days I found one.
I am making this SubWoofer project with a small Sub. If i get success then I will be making a big one with a bigger sub and hopefully tune it as low as possible.
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Old 18th January 2013, 05:25 PM   #13
pranab is offline pranab  India
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Quote:
Originally Posted by Mooly View Post
It is getting confusing as to what you are actually doing.

Are you feeding the output of the filter into an amplifier ? This circuit isn't meant to feed a speaker directly.

Your problems will all come down to the signal levels you are feeding into the circuit and what you are connecting the output of the circuit too.

Tell us exactly what the circuit is connected to.
Sir the output of the Amplifier goes to the circiut and the output of the circuit goes to the speaker ...... (Amplifier - circuit - Speaker) .
The circuit shud be blocking the mids and highs as shown in the tutorial videos but it is not working. Figured Out Simple Low Pass Filter AND single Capacitor LP filter - YouTube
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Old 18th January 2013, 05:40 PM   #14
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At around 2:30 of that video ( nice music ) I hear...positive..negative...resistor...capacitor.. .source!
So it is clear that the filter operates at line level, as it should be for the
very low power (1/4 W) of the resistor, as also the value of the cap.
Source>preamplifier>LPF>amplifier>speaker
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Old 18th January 2013, 06:05 PM   #15
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by pranab View Post
Sir the output of the Amplifier goes to the circiut and the output of the circuit goes to the speaker ...... (Amplifier - circuit - Speaker) .
The circuit shud be blocking the mids and highs as shown in the tutorial videos but it is not working. Figured Out Simple Low Pass Filter AND single Capacitor LP filter - YouTube
It is as several of us suspect. You must feed the output of this circuit into an amplifier.

Just think about it for a minute... a 1K feeding an 8 ohm speaker. Not much will get through. For every volt you put in, only 8 miilivolts appears across the speaker.
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Old 18th January 2013, 06:23 PM   #16
gootee is offline gootee  United States
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Quote:
Originally Posted by Mooly View Post
It is as several of us suspect. You must feed the output of this circuit into an amplifier.

Just think about it for a minute... a 1K feeding an 8 ohm speaker. Not much will get through. For every volt you put in, only 8 miilivolts appears across the speaker.
Or change the circuit.

Pranab, what other speakers, if any, will be fed from the same amplifier's output?

If you allow only the bass to go to the sub, are you also wanting to allow only the mids and highs to go to some other speaker(s)?

How much output power are we talking about, in Watts? Do you have a multimeter or any other test equipment?

Last edited by gootee; 18th January 2013 at 06:46 PM.
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Old 18th January 2013, 07:01 PM   #17
gootee is offline gootee  United States
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You could replace the resistor with a large coil (inductor). And the capacitor would need to be a large-ish electrolytic type, with a voltage rating that is higher than the peak output voltage of your amplifier.

Here is an example filter calculator:

Car Audio - 4th Order Butterworth Crossover Network Design Formulas & Calculator

You would use the low-pass filter, for the subwoofer. I don't know if you would need two stages, as shown, or not.

You might wind the coil(s) yourself. If so, maybe you could take the magnet wire (no thick insulation, just lacquer usually) out of an old electric motor from a washing machine or something, or a car alternator; any medium-sized electric motor (or generator).

Here is an air-core inductor calculator (don't wind it on anything conductive or metallic):

Pronine Electronics Design - Multilayer Air Core Inductor Calculator

If you add something (goop/paste or maybe even liquid of: epoxy, varnish, glue, paint?) that will hold the wires tightly after it dries, adding some after each layer is wound, the result will sound better. You could also soak the whole thing in varnish, after it was wound, and then put it in the sun, or a warm-but-not-hot oven, for a day or two.

NOTE: If you can wind the coil around some ferrous metal, like steel, instead of air, you would need MUCH less wire, and the coil could be MUCH smaller. But I don't have a link for doing that. Try Google.com, after first searching here at diyaudio.com.

Either way, the larger the wire diameter is, the less resistance the coil will have, and the better it should perform. But I would not use larger than about 14-gauge, since it gets dificult to work with, and would be rough on your fingers.

Last edited by gootee; 18th January 2013 at 07:08 PM.
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Old 18th January 2013, 09:26 PM   #18
WSJ is offline WSJ  United States
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100 Hz Low Pass 4 Ohm Crossover


Convenient crossovers that work great in any application requiring economical and flexible filtering. Designed to be wired in-line between amp and speaker by using .205" disconnect terminals or soldering.

Specifications: Approximately 250 watts RMS Type: Low pass Driver impedance: 4 ohm Crossover frequency: 100 Hz Roll off: 12 dB.

Click the image to open in full size.
100 Hz Low Pass 4 Ohm Crossover 266-444
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Old 19th January 2013, 01:04 AM   #19
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pranab,

Most likely the integrated preamp/ power amp in your player is two channel, that is, stereo. It would be helpful if you told us if that is true or not. That presents the additional problem of mixing the left/ right channel signals in order to drive your sub-woofer with a L + R signal.

Have you looked at the rear panel of your player in detail? If your player is a very simple basic piece of equipment, it probably doesn't have any facilities for running a sub-woofer. But there is no harm done in looking. Do you have an owner's manual for the player?

-Pete
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Old 19th January 2013, 04:26 AM   #20
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I have some vintage subs at home (never needed) and they all have two woofers connected to the stereo in a bandpass type enclosure.
In this case what you need is a small inductor to connect in series with the woofer/sub.
Look at projects of 4th Order Bandpass Systems.
The Subwoofer DIY Page - 4th Order Bandpass Systems
Nothing complicate for a passive crossover. As a starting point use a table of 1. order crossovers. (It all depends of the type of woofer driver and impedance). Use a small inductor like 1mH or 2mH as an example for testing with the 8 Ohm woofer. You will notice that this projects are most of them 4th order bandpass with isobaric type systems enclosures some with two woofers others with 1 driver and double voice coil,...
6 dB per Octave Crossover Table Values
SUBWOOFER 8” 8Ω 75W - iwaispeakers
Solid Core Inductors
Jantzen 1.0mH 15 AWG P-Core Inductor
ERSE 2.0mH 18 AWG I Core Inductor

Last edited by Inductor; 19th January 2013 at 04:37 AM. Reason: Inductors
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