New low cost project

[Salamanteiga]

Hello!
I've been given recently some speakers. They came from computer speakers that broke, usually the wallwart or the power transformer. The speakers themselves are ok, I have tested them all and they all sound good, some where from Creative and JBL speakers but most are unbranded. I also have some 2.25'' tweeters that I got pretty cheap.
I was thinking about building some small 3 way cabinets with some of them, using some balsa wood that I have from previous projects.
In terms of power, they are 3-4w and 4-8 ohms each. The tweeters are 20 w 8 ohm.
How can I connect them to get the most power out of them? What kind of crossover should I use?
I know that I won't get the same quality as with top quality speakers but my goal is low or no cost, I just wanna use these speakers.
Thanks in advance.

[AllenB]

In your case I would listen to each of the woofers on their own and use only the ones that sound good without a crossover.

[MCPete]

Assuming that the computer speakers are 4 inches or less in diameter, there is no point in assembling a three-way system. Generally a three-way system is necessary when it includes a woofer with insufficient higher frequency response to match with the typical tweeter that should be limited to handling frequencies equal to or greater than 2 kHz.

So that the power handling in the low range can more nearly match the power handling of the tweeters that you have, you could try connecting multiple computer speakers in parallel and series network aiming to yield total nominal impedance equal to 8 Ohm.

How thick is the balsa that you have? Probably you would want to use T-nuts to mount your computer speakers and tweeters to it, as balsa is very soft and I think unlikely to support much weight attached to it wit wood screws. Also balsa unless very thick would lack rigidity and so may not be suitable for a speaker box, I would think.

Not knowing the parameters of your speakers, probably a closed-box system would be best.

Regards,
Pete

[planet10]

Pictures?

dave

[Salamanteiga]

Hello again.
I'm sorry for the lack of information about the project but when I did the the first post I was going to add some pictures but I had to travel and forgot to bring the camera.
The balsa that I have is 5mm thick, it's quite rigid and strong but maybe the screws will get loose over time. A T-nut is the best option now I just need to find where to buy them.
The tweeters are 8 ohm 20 w. In the drawing attached what power would I get from the paralel+series configuration if 1 and 2 are 3W and 3 and 4 are 4W (all 8 ohm)? Do speaker powers just add and the resulting power would be 14W?
Since the tweeter is 20w would it get more power and make the speaker too bright and harsh?
Thank you all.

[MCPete]

Originally Posted by Salamanteiga

Hello again.
I'm sorry for the lack of information about the project but when I did the the first post I was going to add some pictures but I had to travel and forgot to bring the camera.
The balsa that I have is 5mm thick, it's quite rigid and strong but maybe the screws will get loose over time. A T-nut is the best option now I just need to find where to buy them.
The tweeters are 8 ohm 20 w. In the drawing attached what power would I get from the paralel+series configuration if 1 and 2 are 3W and 3 and 4 are 4W (all 8 ohm)? Do speaker powers just add and the resulting power would be 14W?
Since the tweeter is 20w would it get more power and make the speaker too bright and harsh?
Thank you all.

Another option to the T-nuts might be to use some wood that is sturdier than balsa for the baffle, that is, the panel at the front of the box that the speakers will be mounted on. I'm not certain what your motivation is for using Balsa to make the speaker boxes, but if you wanted to avoid using some other wood for the baffle, then perhaps you could glue some sturdier wood to the back of the baffle of balsa for the mounting screws to grip into.

The wattage rating of a speaker is the amount of electrical power that the speaker can withstand (without being destroyed). So with your configuration of two speakers 3W each connected in series and two speakers 4W each connected in series, 6W would be the maximum power handling for your configuration.

Sensitivity is a different issue from the wattage figure usually printed on the speaker. Usually sensitivity is understood as voltage sensitivity, or how much sound intensity output a speaker will produce for a given voltage drop across the input terminals of the speaker.

Without knowing the sensitivity figures for the computer speakers and the tweeter of your configuration, it would be difficult to say whether the configuration you propose would approach having flat frequency response. If all of the computer speakers 1-4 are 8 Ohm each, then the network of computer speakers and the tweeter would be equally powered. It is a question of the relative voltage sensitivity that would determine whether or not your speaker system would have too much treble output or not.

At a minimum there should be a capacitor in-series with the tweeter of your network rolling off power in the frequency band with an upper limit near the resonant frequency of the tweeter. The tweeter can be easily destroyed if you don't connect a high-pass filter to it and subject it to a full spectrum audio signal.

-Pete