Hi guys, I'm planning to build a DIY subwoofer but I'm new to these audio stuffs.
I have a 20w speaker and a 25w amp to drive the speaker. The amplifier is driving the speaker with all audio frequency signals but I need only low frequency bass signals to be amplified. So I made a low pass filter using 741 Operational amplifier and connected between output of amp and the sub. But the result was worse. Instead of filtering the low frequency signals the LPF attenuated the signals.So my question is, was my choice of putting a low pass filter is correct? If yes, where is the correct position to insert the LPF? Before amp or after amp?
And my last doubt is, whether 20w sub is powerful enough in a 4*4 metre room.
Please give me some suggestions.
I have a 20w speaker and a 25w amp to drive the speaker. The amplifier is driving the speaker with all audio frequency signals but I need only low frequency bass signals to be amplified. So I made a low pass filter using 741 Operational amplifier and connected between output of amp and the sub. But the result was worse. Instead of filtering the low frequency signals the LPF attenuated the signals.So my question is, was my choice of putting a low pass filter is correct? If yes, where is the correct position to insert the LPF? Before amp or after amp?
And my last doubt is, whether 20w sub is powerful enough in a 4*4 metre room.
Please give me some suggestions.
Operational amplifiers work at signal levels, the output of a power amplifer is high power and completely unsuitable for active filtering - passive cross-over filters are used after a power amp, using large inductors and capacitors.
To low-pass filter with an opamp you need to do this before the power amp at line-level.
The 741 is not appropriate for audio, its noisy and poor performance. NE5532's are the to-go easy to source opamp for general audio use, there are others too but for price/performance ratio few compete.
How low in frequency do you want to go with the sub? What driver and enclosure are you using/contemplating? Ported (bass reflex) or not?
To low-pass filter with an opamp you need to do this before the power amp at line-level.
The 741 is not appropriate for audio, its noisy and poor performance. NE5532's are the to-go easy to source opamp for general audio use, there are others too but for price/performance ratio few compete.
How low in frequency do you want to go with the sub? What driver and enclosure are you using/contemplating? Ported (bass reflex) or not?
Hello,
You can't put an op amp or DSP based low pass between the amp and the speaker. Op amps are for doing very precise things to small, weak signals. Amps deliver big, high-power signals to speakers to drive the magnets. Assuming the amp didn't break the opamp filter (a possibility if it is only 25W) then go ahead and put it at the input of the amp.
Brian
You can't put an op amp or DSP based low pass between the amp and the speaker. Op amps are for doing very precise things to small, weak signals. Amps deliver big, high-power signals to speakers to drive the magnets. Assuming the amp didn't break the opamp filter (a possibility if it is only 25W) then go ahead and put it at the input of the amp.
Brian
Oh ok.....
I would like to amplify the signals with a frequency up to 150Hz.
I'm using a 25w+25w TDA7492P Bluetooth amp as a driver and I'm planning to use a simple wooden enclosure.
I would like to amplify the signals with a frequency up to 150Hz.
I'm using a 25w+25w TDA7492P Bluetooth amp as a driver and I'm planning to use a simple wooden enclosure.
A driver is a loudspeaker unit, without the box. What driver are you thinking of.
What size of enclosure? Ported or not ported?
I have a 20w speaker which I got from my friend's old creative home theater system.And I've not yet decided the dimensions of enclosure.
Today I tested my speaker with a low pass filter connected before the amp, low frequency signals got filtered out and amplified pretty well. But I had observed an other problem..... The bass was not at all audible even though the cone paper of the driver was vibrating pretty well.
I tested this by just keeping the driver on the table without any enclosure. What will be the problem?
I tested this by just keeping the driver on the table without any enclosure. What will be the problem?
> The bass was not at all audible even though the cone paper of the driver was vibrating pretty well.
I tested this by just keeping the driver on the table without any enclosure. What will be the problem?
You NEED a box.
I tested this by just keeping the driver on the table without any enclosure. What will be the problem?
You NEED a box.
Ok. Which will be the best enclosure if I want to get louder bass. Ported or not ported?
Also can you please give me a best dimensions for the enclosure. The driver I'm using is of 4 inch, 20w RMS
Also can you please give me a best dimensions for the enclosure. The driver I'm using is of 4 inch, 20w RMS
This like pulling teeth...
Which exact driver are you using? Do you have all the specifications for it?
You'll need the Thiele-Small parameters if you want to design a subwoofer, and there are various web apps out there that can do the work for you, but without the data for the driver you'll be guessing wildly, and drivers differ a lot.
I have got 5.25 inches by measuring the drivers dia, there it has been printed as CSW 20W, 4 Ohms behind the driver and it has got dual magnets in it. These are the only specifications I have.
No not a round one. It looks like this:
ESP 5 Inch Powerful Subwoofer 4 Ohm 30 Watt 5 Inch Subwoofer 4 Ohm 30 Watt for Home Theater Subwoofer Price in India - Buy ESP 5 Inch Powerful Subwoofer 4 Ohm 30 Watt 5 Inch Subwoofer 4 Ohm 30 Watt for Home Theater Subwoofer online at Flipkart.com
The shape,looks and size are exactly same as shown in above link. But the output power of my driver is 20w.
ESP 5 Inch Powerful Subwoofer 4 Ohm 30 Watt 5 Inch Subwoofer 4 Ohm 30 Watt for Home Theater Subwoofer Price in India - Buy ESP 5 Inch Powerful Subwoofer 4 Ohm 30 Watt 5 Inch Subwoofer 4 Ohm 30 Watt for Home Theater Subwoofer online at Flipkart.com
The shape,looks and size are exactly same as shown in above link. But the output power of my driver is 20w.
I think what you’ll soon find out is that you cannot design (nor can anyone recommend) a box without the TS parameters. I’ve never measured my own but perhaps someone here will instruct you.
Or, just build a modest sealed box and see how it sounds. Make the box as big as you can tolerate. It will make more bass than sitting on a table, not as much as a properly tuned ported enclosure, but something.
Or, just build a modest sealed box and see how it sounds. Make the box as big as you can tolerate. It will make more bass than sitting on a table, not as much as a properly tuned ported enclosure, but something.
For the vast majority of domestic speakers: multiply advertised diameter by about 1.1. Cube that. Build a box that size. Preferably different on all three dimensions. Half fill it with wool blanket, socks, or even fiberglass. This will almost always give a Q of 0.8 to 1.6, and pretty near optimum output.
So 5.25", times 1.1, is 5.775. Cubed, is 193 cubic inches.
7" times 6" times 4.5" is 189 cubic inches.
This is NOT a precision prescription. A 4 liter box is fine. 7 inches of 6-inch drain pipe is fine.
So 5.25", times 1.1, is 5.775. Cubed, is 193 cubic inches.
7" times 6" times 4.5" is 189 cubic inches.
This is NOT a precision prescription. A 4 liter box is fine. 7 inches of 6-inch drain pipe is fine.
Thank you very much.
But I didn't understand what is 7 inches of 6 inch drain pipe? Is that a port dimension?
But I didn't understand what is 7 inches of 6 inch drain pipe? Is that a port dimension?