need help in buiding an amplifier

[nightcatz]

hi guys ,
I have got a 8 inch sub-woofer ...now I want to buiild an amplifier for the sub-woofer but I dont know the ratings of the speaker ....Is there any way to measure the wattage of the sub...

 

[Nigel Goodwin]

hi guys ,
I have got a 8 inch sub-woofer ...now I want to buiild an amplifier for the sub-woofer but I dont know the ratings of the speaker ....Is there any way to measure the wattage of the sub...

Only by destroying it - where did it come from?.

 

[audioguru]

An 8 inch speaker is a woofer. It is too small to move enough air to be a sub-woofer. A 10 inch speaker is marginal to be a sub-woofer and 12 inches works very well.

 

[nightcatz]

you did not answer my question what should be the wattage of the amp that can drive the 8 inch woofer

 

[TrevorP]

Well why not find out the Resistance and Power of the Speaker?

 

[Nigel Goodwin]

you did not answer my question what should be the wattage of the amp that can drive the 8 inch woofer

You didn't answer mine either - it was asked for good reason!.

 

[audioguru]

If the 8 inch woofer is a name-brand then look at its spec's on the manufacturer's website.

 

[nightcatz]

i bought it from an electronics spares vendor ....non branded...what i know is that it is an 8 inch sub

 

[Gayan Soyza]

I can say it is more than 30W.

 

[audioguru]

Speakers usually play music which is short pulses of power with pauses between. The speaker won't be driven at high power continuously.
So use the TDA2050 amp as mentioned in your PM and it will produce the 28W at clipping without problems.

Since the woofer doesn't have any spec's, make a fairly large sealed enclosure for it. If you guess at the size and dimensions for a vented enclosure then it will probably just produce a "boom" at a single frequency or it won't produce any bass.

 

[mneary]

You probably ought to confirm that it's really a sub. Find its free-air resonant frequency by sweeping from about 10 Hz to 200 Hz or so, watching the impedance. The resonance will be evident where the impedance peaks.

Using the resonant frequency, go to a website that tells how to design the enclosure. You're still missing a lot of "important" information, but you might end up with a listen-able enclosure.

If it's really a sub woofer, you can safely drive it to the point where the speaker travels about half of its available excursion, at the minimum frequency.

 

[nightcatz]

audio guru u have suggested me to build a fairly large sealed enclosure .....will a 11"x11"x11" cube be fairly large for the 8inch sub...more over will the sealed enclosure produce bass reflex like the vented one..please tell me the polarities of the capacitors c2-c6 in the split supply version

 

[Nigel Goodwin]

audio guru u have suggested me to build a fairly large sealed enclosure .....will a 11"x11"x11" cube be fairly large for the 8inch sub...

That's a tiny box - not a fairly large one!.

 

[audioguru]

audio guru u have suggested me to build a fairly large sealed enclosure .....will a 11"x11"x11" cube be fairly large for the 8inch sub?

The enclosure is so small for an 8 inch woofer that it will boom at about 150Hz and will not have any deep bass.
Look at the 8 inch speakers at a stereo shop. They are just ordinary woofers that go down to about 60Hz and have enclosures that are 20 inches high, 10 inches wide and 9 inches deep. They use good quality woofers with a low resonant frequency.

Your woofer is no-name without any spec's. It might not produce any bass frequencies. The bigger the box, the lower it goes.

will the sealed enclosure produce bass reflex like the vented one?

A sealed enclosure goes pretty low if it is large and the woofer is good quality.
A vented bass-reflex enclosure goes very low if it is large, the woofer is good quality and the enclosure is designed together with the spec's of the woofer.

please tell me the polarities of the capacitors c2-c6 in the split supply version

The schematic in the datasheet shows polarities. The open bar on the capacitor symbol is the positive wire.
I would use a non-polar electrolytic for C2 but it doesn't have DC across it so an ordinary polarized electrolytic will work fine for a while.

 

[Armagdn03]

I disagree with that first statement. The size of the speeker deturnines its frequency range a great deal, but not its travel. I have heard some 8 insh subs that are quite loud and deep, not so much as a 10 or larger, but still a sub none the less. I think it has more to do with its travel and response than anything else.

 

[audioguru]

Some guys on diyAudio.com are getting some bass from dinky little 3" full-range speakers in huge transmission line enclosures. The max power is only 10W so they aren't very loud.

My clock radio has a pretty good replacement 3" speaker and 20dB of bass boost at 100Hz. The volume control is tapped and below the tap gives full bass boost and above the tap the boost is reduced to avoid amplifier clipping and speaker damage. It sounds a lot bigger than a little clock radio.

I equalized my Acoustic Research speakers and some more I made with bass boost. Their 8" woofers sound almost like sub-woofers but you can't feel the bass like a good sub makes.

The 10" sub driven with 200W in my car shakes my bones pretty well. The rear deck 6x9 speakers are the first time I ever saw 2 ohm speakers.