Can't know if amplifier will run my subwoofer

[vascobrissos14]

Hello, I'm currently building a boombox and I'm having some troubles with the woofer (sub).
I picked a GW525 8Ohm from parts express https://www.parts-express.com/goldwood-gw-s525-8-5-1-4-poly-cone-woofer-8-ohm--290-302

And a 100W mono amplifier from ebay http://www.ebay.com/itm/322254477895

My question is if the amplifier will drive the speaker properly because i can't see the ohm rating on the amplifier.

I tried to check the chip specs but understood nothing... that's why I came here.

I chose a 100w amplifier so I don't clip it and destroy the woofer. (From what I saw on youtube).

Thank you for any help!

 

[Kenton82]

A very similar amp board to this covers 8Ohms, so i would say you are fine although the woofer is very small at 5 1/2" And the ammount of air displacement you will get from this will be minimal. Also the RMS rating of the speaker is 70W, but i doubt the amp is 100w RMS. Where are you going to use this? In a car, or in your home?
Kind regards,
Kenton

 

[vascobrissos14]

I'm going to use it on a boombox. A portable Bluetooth speaker. And thank you for the reply

 

[Kenton82]

Ah, my mistake, i thought you were going to use it as a dedicated subwoofer!
No problem, sounds cool! Just make sure you get all frequency's through that speaker.

Good luck man.

Kenton

 

[vascobrissos14]

Thanks! I asked Parts Express if it was still possible for them to change the woofers (the 8 ohm for the 4 ohm model) but if they can't I guess theres no problem from what you said. Thanks again

 

[Kenton82]

Hey, no problem! Glad to help, sounds like a cool little project! Personally i would stick with the 8 Ohm one. This is average benchmarking resistance for most amps.

Have fun!
Kenton.

 

[vascobrissos14]

But I saw that the lower the impedance the more power will be drived thru the speaker. Is this true? Or will the 8 ohm work the same as the 4 ohm one? Thanks!

 

[Kenton82]

The lower the impedance, the more power is needed to drive it. So, a 4ohm speaker offers 50% less resistance, so it will require more current. The amp has to provide more current to the four ohm load so the output transistors have to be more robust.
In your setup, you are better off sticking with the 8ohm because it is more likely a better suit for the amp.
I cant find any schematic diagrams or further info on that amp board unfortunately.

Kenton.

 

[vascobrissos14]

Ok thanks m8!