Resonance and dB

[Hero999]

Listen to audioguru he is right.

Normal loudspeakers are very inefficient, you need a really powerful horn speaker. Also I wouldn't risk blowing a decent amp up I'd build an inexpensive h-bridge driver and power it from that.

The reason I was suggesting connecting a transducer to the glass earlier on is because it will save you having to tune to the resonant frequency becaue ti will automatically oscillate at that frequency when placed next to the speaker.

 

[Marks256]

I'd build an inexpensive h-bridge driver and power it from that.

What is an h-bridge? Power what from what? Power the speakers from the h-bridge? Ok, but what is an h-bridge?

 

[Roff]

Do you have a better idea?

Memorex and Ella Fitzgerald?

 

[Roff]

What is an h-bridge? Power what from what? Power the speakers from the h-bridge? Ok, but what is an h-bridge?

Google.

 

[Someone Electro]

Just make a H bridge out of high curent MOSFETs.You could use a half h bridge if you have a dual supply.

If you saturate the mosfets there will be very litle heat and a huge power output.

I recomend IRF3205,Its on resistance is 0,008 Ohm so it can hande a huge curent whithout overheating.Altrough they only work up to 55V so it needs a realy low inpendace load.

 

[Marks256]

Google.

Duh. I just looked up schematics. They do looks simple, but what exactally are they? Like a simple AMP, or what?

Just make a H bridge out of high curent MOSFETs.You could use a half h bridge if you have a dual supply.

If you saturate the mosfets there will be very litle heat and a huge power output.

I recomend IRF3205,Its on resistance is 0,008 Ohm so it can hande a huge curent whithout overheating.Altrough they only work up to 55V so it needs a realy low inpendace load.

Ok. I will try to find one. I am on a $35 budget, though...

 

[Hero999]

It's easier to understand if you picture it as switches.
https://en.wikipedia.org/wiki/H-bridge

All you do is put a squarewave into the speaker, it's no good for music but the most efficientway of producing a single very high powerd tone.

I suggested a horn speaker because it's the most efficient and it's proably the only way you'll get enough power to destroy the glass.
https://en.wikipedia.org/wiki/H-bridge

 

[audioguru]

Half the power of a square-wave is the frequency you want. The other half is the distortion harmonics. Very few higher frequency speakers can handle their rated power continuously, since music and voices have levels that change continuously.

 

[Marks256]

from the schematics i have seen on the net, i kinda figured it was something like a switch.

 

[audioguru]

An h-bridge switches a motor on and off quickly for PWM speed control. It can also reverse a motor. It could switch a speaker so it moves forward and backwards until it melts or breaks.

 

[Marks256]

An h-bridge switches a motor on and off quickly for PWM speed control. It can also reverse a motor. It could switch a speaker so it moves forward and backwards until it melts or breaks.

*Drool* ugh, so much power..... So i take it that this would be a good device to use for this application?

 

[Someone Electro]

Well a audio amp is somthing like a H brige but the transistors in it a precicly controled to make a variing voltage.

The power output entierly depends on your semiconductor swicthes.The more you transistos in the H bridge can hanlde the more it wil output.But most amps use linerar drive to them.So they waste a lot of heat.This is fixed by those expensive class D amps where they use mosfets or igbt and are PWM controled by a very high inaudable freqecy.Since they keep the transistors saturated there is litle heat.These kind of amps are the most expensive kind.

You can do the same as a D amp exspect lose the very complicated control circuetry and high freq PWMand simply drive that frqecy you want right in.

The IRF3205 costs here about 2,50$ a pice.The chip inside is rated for 110A but becuse the pins on the TO-220 are so thin this is limited to 80A.And are repetivly pulse rated for 300A.

But becuse of its low voltage the max this could output in a 4Ohm load is 700W.Curent trough the mosfets is about 14A wich will make very litle heat on this mosfet(That is if you give its gate at saturation wich is 15V)

 

[Hero999]

Half the power of a square-wave is the frequency you want. The other half is the distortion harmonics. Very few higher frequency speakers can handle their rated power continuously, since music and voices have levels that change continuously.

Then add an LC filter on the output to select the required frequency.

 

[Marks256]

Well. I have about 4-6 IRF224s, and about 8 TIP3055s. Would either of them work?

 

[audioguru]

Then add an LC filter on the output to select the required frequency.

An LC filter would be big and also needs its frequency to be tuned. How?
A lowpass filter won't work well. Maybe a series resonant circuit in series with the speaker?

 

[Marks256]

I don't mean to be too demanding, but;

I have about 4-6 IRF224s, and about 8 TIP3055s. Would either of them work?

 

[audioguru]

You could make an audio amplifier or an h-bridge with the transistors and a pretty big power supply but you don't have a speaker that is loud enough to break a glass.

 

[Marks256]

you don't have a speaker that is loud enough to break a glass.

No, probably not. But the transistors would work? Cool....

 

[Someone Electro]

Those transistors wont work very well if you want lots of "juce".IRF224 has a on resistance of 1.1Ohm Thats afuly a lot its rated for 3,8A aontinues in a TO-3 package.Its datasheet looks prety old.As for the TIP one that is a NPN bipolar transistor rated for 15A contines and only 20 hFE.

So you wont be able t make someting very powerfrul out of this.

Altrough if you can find a very low resitance mosfet whith a voltage of like over 100V use it.Cause the limitation of this IRF3205 is its max voltage.Its more ment to be for like a inverter or a motor driver and other stuff that has high curent draw.

Your in the USA so you could use rectified mains for your powersuply you need some big caps trough.Then you need some high voltage mosfets that can handle someware 40A or more.Then you can push 2,5kW in a 4Ohm load.

EDIT:I forgot what is the max power you can draw from a mains outlet in USA? Cause i think that can trip the breaker if you find such a 2,5kW load.I just know in EU breakers trip at a litle more then 3kW

 

[audioguru]

In Canada and the USA our homes have stove and air conditioner outlets with very big wires providing 240V/30A which is 7200W.

The TIP3055 was used in many old stereo amplifiers. Its hFE is a minimum of only 5 at a collector current of only 10A and is not mentioned at 15A.
Its plastic case can dissipate about 50W on a pretty big heatsink.