Building speakers

Stupid question: how does one take a speaker signal and convert it to the pulses needed to drive the magnets in a speaker coil? Are there any intermediary electronics needed or do I just connect the wires?

The motivation for the question is that I have an idea for a new speaker design, and I’d like to test it out.

the signal driving a speaker is typically not pulses ( unless you are talking about a class d amplifier ) …

The alternating current in the wires goes directly to the speaker’s wire coil. The magnets are permanent magnets and not electified. If there is more than one “driver” in an enclosure where each is devoted to a different range (e.g. woofer and tweeter), then there is a crossover circuit before the signal gets divided by frequency. Try this:
http://en.wikipedia.org/wiki/Loudspeaker

er…are you telling that you are going to make an experiemental speaker cone and coil /magnet by yourself or just use something existing and re-design the box around it ?

braunie

Interesting you should mention Class D, I was thinking of getting a new pair of active class D PA speakers for one of my rooms, but am a little bit worried about a couple of things, one is the reliability of the SMP and the other is what happens if a driver fails? But then the supplier Digital Village does have a four year guarantee :stuck_out_tongue:

Anyway I do believe that the signal the speaker sees is basically the same, after its gone through a low pass filter, as class AB or A

Anyway, to the OP just connect the wires making sure the speakers impedance and power rating match the quoted amplifier spec.

Unless you are going to use a tweeter or Hf horn then you will need a crossover to split the signal into Hf and Lf components.

Ummm… if it’s already a ‘speaker signal’ then why would you need to convert it to drive a speaker? And in fact it’s not actually the magnets that get ‘driven’ it’s the coil. But you’re forgiven, you did afterall open by saying ‘stupid question’ :smiley:

I think before embarking on your idea there may be some merit in understanding that basics first. Before you reinvent the wheel you probably should at least understand how the wheel works in the first instance. :stuck_out_tongue:

http://electronics.howstuffworks.com/speaker6.htm

Seriously though, what’s this new idea youve got in mind? Or…maybe it’s top secret? :confused:

Many years ago I used to build speaker enclosures. The maths was complicated - particularly vented designs based on a the Helmholtz resonator principal, fortunately today there are tools readily available to do all the calculations for you. Just punch in the appropriate driver (speaker) parameters and away you go!

I once built this very effective sub-woofer, using to 12" passive radiators, and one active 12" woofer, all mounted in a custom-built tri-faced angular enclosure. I had to add extra weighting to the passive radiators center to get their resonant frequency down to a suitable figure, but unfortunately this added weight over time eventually distorted their cones (actually they were flat diaphrams) and put too much strain on the roll surround. Bugga. :imp:

Some tube-amp designs can handle a certain amount of impedance mismatch. Many Fender output stages rated for an 8-ohm load can operate at 4 ohms or 16 ohms if the amp isn’t dimed for hours-on-end at a Death-Valley open-air festival in August.

I do not operate tube amps with LESS speaker load than the output stage is rated for. Remember that the lower the speaker impedance, the closer you’re getting to the amp output stage seeing a dead short. Also recall that the impedance is a nominal measure; not exact … and is frequency dependent. Plugging another cabinet into the extra speaker jack of a Super Reverb with 4 speakers already presenting a 2 ohm load … and something is going to let the smoke out. That’s particularly bad for a tube amp. So I don’t recommend it. Never, ever run a tube amp without a load on it. Never.


Interesting reading here:
http://www.prestonelectronics.com/audio/Impedance.htm

Solid state amps typically have a ‘minimum load impedance’ indicated near the speaker terminals, and the total speaker impedance must be equal to or greater than that value. Tube amplifiers typically have a switch on the back to adjust for the speaker load impedance. Tube amps have different output characteristics than solid state amplifiers, and too low a load impedance will not normally damage them, but the total output will become weaker and muddy. So too little load impedance is still undesirable. Too high a load impedance on a tube amp can cause high voltages inside the amp that can damage power output tubes or the output transformer.

Indeed, a keyboard player once thought they’d do me a favor and switch on my JCM800 only thing was the speaker wasn’t connected. Result, two knackered output valves, lucky it didn’t spark over in the output transformer :imp:

It is a totally new concept…at least as far as I know.

This isn’t a new idea for me, but spending the time talking to Larry Hartke lately when I’ve stopped by Sam Ash the last few times has resurrected the thought.

I’ll read the links, and I’ll consult my father. Many, many years ago he was extremely knowledgeable about electronics.

You may be onto something there :stuck_out_tongue:

Using a liquid nitrogen cooled niobium-titanium super conducting electromagnet to replace the permanent magnet, creating an immense magnetic field you could build an incredibly powerful very loud speaker to blow your neighbors off the planet :laughing:

Ok so “pulses” was a really poor choice of words. I read both of the links and everything in there was pretty much as I understood things.

So in a grand generalization I was correct that I could take the output from an amplifier like in a home stereo and basically connect it to a coil that acts as an electromagnet. The magnetic field generated interacts with a permanent magnet to push and pull the speaker cone, and that generates sound pressure waves.

I know the devil’s in the details, but that’s essentially it correct?

Yep, that’s basically it.

There are some variations…

like electrostatic panels where a the power amp voltage is stepped up to a very high electric voltage across a pair of mesh plates between which a very thin static-sensitive film sits. This film then vibrates in sympathy with the applied electrostatic field.

Or pizzo transducers that take the amplifier voltage, applied across a crystale that vibrates as a result. this is coupled to a diaphram. This is typically used in pizzo horn tweeters, because the crystal response drops sharply at lower frequencies.

There are also various hybrid designs around such as magnaplanar, ribbon and NXT transducers that excite a flat surface to create the sound.

Of course for traditional moving coil speakers, the diaphram material and the box play a massive part in the final sound, and there are books full of the maths involved in the design of a working product.

Well the actual fidelity might be questionable… But:

http://youtu.be/LVDmjnCQ1g4

Musical Tesla Coils!

edit… Actually, far more impressive:

http://youtu.be/PdrqdW4Miao

Fing brilliant and far more fitting than that blaspheming orchestrated current Dr Who theme tune which should be all electronic keeping the spirit of the original masterpiece alive… IMO :laughing:

"The original 1963 recording of the Doctor Who theme music is widely regarded as a significant and innovative piece of electronic music, recorded well before the availability of commercial synthesisers. Delia Derbyshire of the BBC Radiophonic Workshop used musique concrète techniques to realise a score written by composer Ron Grainer. Each and every note was individually created by cutting, splicing, speeding up and slowing down segments of analogue tape containing recordings of a single plucked string, white noise, and the simple harmonic waveforms of test-tone oscillators which were used for calibrating equipment and rooms, not creating music. The swooping melody and pulsating bass rhythm was created by manually adjusting the pitch of oscillator banks to a carefully timed pattern. The rhythmic hissing sounds, “bubbles” and “clouds”, were created by cutting tape recordings of filtered white noise.[1]

Once each sound had been created, it was modified. Some sounds were created at all the required pitches direct from the oscillators, others had to be repitched later by adjusting the tape playback speed and re-recording the sound onto another tape player. This process continued until every sound was available at all the required pitches. To create dynamics, the notes were re-recorded at slightly different levels.

Each individual note was then trimmed to length by cutting the tape, and stuck together in the right order. This was done for each “line” in the music – the main plucked bass, the bass slides (an organ-like tone emphasising the grace notes), the hisses, the swoops, the melody, a second melody line (a high organ-like tone used for emphasis), and the bubbles and clouds. Most of these individual bits of tape making up lines of music, complete with edits every inch, still survive.

This done, the music had to be “mixed”. There were no multitrack tape machines, so rudimentary multitrack techniques were invented: each length of tape was placed on a separate tape machine and all the machines were started simultaneously and the outputs mixed together. If the machines didn’t stay in sync, they started again, maybe cutting tapes slightly here and there to help. In fact, a number of “submixes” were made to ease the process – a combined bass track, combined melody track, bubble track, and hisses. Eventually, the piece was finished.

Grainer was amazed at the resulting piece of music and when he heard it, famously asked, “Did I write that?”. Derbyshire modestly replied “Most of it”. Unfortunately, the BBC—who wanted to keep members of the Workshop anonymous—prevented Grainer from getting Derbyshire a co-composer credit and a share of the royalties"

I love pioneers but speaker/enclosure design? it’s all been done. There’s tons of stuff about passive radiators, porting, cone material, magnetic materials/flux, impedance, solid state vs valves (tubes) etc., etc., and everything else on the Internet.

When I was a lad I played an AC 30. Someone I worked with told me the latest thing was transistors which would blow away my AC30. He built me a 60 watt solid-state (2N 3055 output transistors) and he proudly brought it to my house where it farted weakly. Another guy told me he’d invented a small speaker enclosure that would out-perform a Marshall stack. He demonstrated it in my own house and managed to impress my hamster, but not me.

The lesson here is - it’s all been done before, trust the pros and not the wannabees. Unless, foolomon, you’ve discovered the secret of Grados and want to translate that into guitar speakers! :laughing:

Ken Fischer (may he rest in peace) took the magic of the AC30 circuit and further refined it into something truly spectacular, and even more magical. Thank goodness he had the vision and entrepreneurial drive to see it to fruition.

http://www.ultimateguitargear.com/kens_column.htm

http://www.trainwreck.com/

Yeah but I know what I’m doing with songs…I think. :stuck_out_tongue: I don’t know squat about speaker design.

I know what I’m talking about - see here: http://www.brianrobinsonmusic.co.uk/

(BTW Jeff Beck is trialing Tayden speakers - ask Paul Seago at http://www.taydenspeakers.co.uk/)