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I am working on Active Noise Cancellation project.
For my project, I need a simple woofer(loudspeaker driver) to drive the microphone at one meter away for frequencies 50-250 Hz.
I have a 5" woofer in my lab. I designed amplifier and tested it, well it might be taking around 10 watt power(cant really increase more without distortion) but the sound reproduction is very poor, even when the microphone is too close, the waveform looks too bad.
Now I have to buy a woofer and decide on power amplifier to be used. Initially I was thinking, I might need driver size of around 8" and 30 Watt power but looking at this experience, I am kind of confused now.

My question is how much power is required to accurately reproduce the sound at 1 meter away microphone for 8" or 10" driver for 50-250 Hz frequencies?

Please suggest me if anyone has some experience.Thank you!
PS: I cant use subwoofer sets because of their size nor the sub woofer chassis as they are too costly for me.

EDIT: I have microphone ATR ATR3350 Omnidirectional Condenser Lavalier Microphone
and I am using LM1875 power audio amplifier with basic circuit given in the data sheet.

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  • Unless you are conducting your experiments in an an anechoic chamber you will get waveform "distortions" at any distance because of reflections and interference. This has nothing to do with the power of the amp/woofer. In fact, your question does not make sense. What does "accurately" mean in this context? If loudness is not an issue you most likely can use what you already have, just amplifify the signal after it is picked up by the microphone to get the desired signal level. – Johannes Feb 18 '16 at 15:57
  • I meant for "accurately" in a sense without distortion in waveform. I am working in a regular environment,no anechoic chamber still I could reproduce the sound waveform clearly for higher frequencies above 300 Hz but when I am going for low frequencies same speaker with same power can not be able to reproduce the waveform. Can you please check my comments below to the Rory Alsop answer and tell whether what I am thinking is correct or not. Tq – charansai Feb 18 '16 at 16:12
  • Yes, I understand. But if you are picking up a good waveform a couple of cm away, and a "distorted" one a meter or so away, your problem is not lack of power but standing waves and reflections. More power will simply make you problem worse! You cannot expect to pick up a "perfect" waveform at a distance, regardless of the power, unless you use a treated room. – Johannes Feb 18 '16 at 16:27
  • Ohh kk If possible can you please provide some reference explaining the problem associated with the reproduction of waveform at some distance for low frequencies. I need to dig deep into the details. Tq – charansai Feb 18 '16 at 16:32
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This question as it stands is not quite answerable.

You could use a 5" or a 12" and both could be accurate in that frequency range. Size just allows for more movement of air.

And they could be accurate at 5 Watt or 250 Watt - but the higher the power the more likely you are to overload the mic and distort it.

And you really want to look at the cabinet, as it has an awful lot of impact on frequency response.

So maybe the question should ask, "What do I need to look for in a speaker to provide accurate reproduction?"

To answer that, basically, what you should look for is a speaker sold as "flat response" - so studio monitors might be a good type to look at.

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  • Let us continue this discussion in chat. – Rory Alsop♦ Feb 18 '16 at 15:27
  • I am sorry, I texted you but I guess I dont have enough reputation for chat! – charansai Feb 18 '16 at 15:42
  • k but my doubt if the woofer is provided with less power then it could influence the microphone only at few cm away. I am getting very good waveform for my woofer just in front of the speaker but not for when it is bit away I need clear waveform at 1 meter away. Obviously it has to depend on how much power we are providing to the speaker it will decide with how much power it could push the air around it, so this pressure will sustain for long distances. Is it not ? – charansai Feb 18 '16 at 15:47
  • My question is how much speaker power is rougly needed to drive the -54 dB sensitivity microphone located one meter away. May be I have to try for different powers and check individually but my power amplifier has limit of 30 watt. So.. I am thinking how much powerful amplifier i need to buy now. – charansai Feb 18 '16 at 15:48

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