Loudspeaker basics

[telbert twang]

I am very dumb on speakers thing, getting more and more interested on that though. Is there somewhere a good source or good people to get answers to some loudspeaker basics questions?

1) How and what the voice coil diameter influences in sound?

2) What is the ´ribbed´ and ´smooth ´cones basic difference/point?

3) What is the good/reasonable sensibility value for 10" speaker (dB), and is it little bigger with bigger speakers (for example - 95db for 10", 100dB for 12") ?

4) The wattage - lets say we have 2 otherwise identical speakers, only one is 25W and other is 35 ? Is there any difference in the context of <25W amp?

5) What can be achieved by ´speaker (acetone, etc) treatment` and how´s the procedure?

tt

[jefrs]

1) magnet size...
2) flexibility - allegedly.
3) this is the efficiency of the speaker, and it varies (a lot) with frequency. Celestion post frequency curves which all look the same to me but they definately sound different. In this case I think the dB is the ratio of applied signal voltage to sound pressure at different frequencies, I doubt the speaker is being driven at full chat.
4) amp should always have speaker rated for more. Example- makers fitted 30W G12H in a 5W amp or 100W G15 in 10W bass amp. Prolly 'cos they sound nice, more clean headroom etc. Good speakers are conservatively rated, so you will get away with 25Watter in 25W amp - if you crank it up you get cone 'break-up' (what ever that is) earlier.
5) acetone is a particularly nasty solvent with a flash point of -4 Celcius, it could strip all the insulation off the voice coil and then catch fire. Just blow the dust out, if it works, don't fix it.

All speakers are equal, except some are more equal than others.
Ears are the bext assessment. Some speakers suit certain amp/cabs, and playing style, some don't.
Example- combo drives a closed cab:- Speaker type A sounds great in the cab, but when it's put into the combo it's lacking. Speaker type B from the combo sounds the same as type A when it's in the cab. Go figure.
Your choice of 25 or 35 Watt - which sounds best?

[giantslayer]

Good speakers are conservatively rated, so you will get away with 25Watter in 25W amp - if you crank it up you get cone 'break-up' (what ever that is) earlier.

One caveat - the amp power ratings are usually clean power, so if you're blessed enough to be able to overdrive the snot out of your tube power section, it will probably be putting out more than the rated wattage.

[Ricky D.]

Originally Posted by telbert twang

I am very dumb on speakers thing, getting more and more interested on that though. Is there somewhere a good source or good people to get answers to some loudspeaker basics questions?

1) How and what the voice coil diameter influences in sound?

2) What is the ´ribbed´ and ´smooth ´cones basic difference/point?

3) What is the good/reasonable sensibility value for 10" speaker (dB), and is it little bigger with bigger speakers (for example - 95db for 10", 100dB for 12") ?

4) The wattage - lets say we have 2 otherwise identical speakers, only one is 25W and other is 35 ? Is there any difference in the context of <25W amp?

5) What can be achieved by ´speaker (acetone, etc) treatment` and how´s the procedure?

tt

1. Voice coil diameter - relates to power handling and efficiency. It is too deeply interrelated to other design choices to isolate as an indicator of how a speaker will sound.

2. Don't know. Absent a controlled experiment - comparing two speakers with different cones but otherwise identical - any answer would be BS.

3. Sensitivity is a defined measurement. It is the SPL at one meter on axis with the speaker driven at 1000 hz. by one watt. It has nothing to do with the diameter of the speaker. It has a lot to do with the strength of the magnet and the amount of wire in the voice coil.

4. It's sensible to use speakers that are rated for more than the rated output of the amp.

5. Never heard of it.

[BluesOwl]

acetone applied to cone edge ring can age it a little...to help achieve an aged speaker.
Supposedly matchless amp co. does this with the celestion spkrs they put in their amps.

[Dacious]

IMO I would match speaker spec to amp spec. Putting a 30 watt rated speaker with a 5w amp will only tend to dampen it, because the higher-rated components will be harder to drive. The voiceoil is like a spring, it has to be distorted through electromechanical energy to push the speaker cone and surround, thicker and stiffer in the higher-rated amp. Like putting 22" dubs on a Toyota Corolla. Same with 100 watts on a 30 watt amp. Won't hurt, wont be optimal.

Yes you can do it, and if you run the amp constantly dimed the higher wattage speaker will live better. But maybe in that case you should consider a more powerful amp.

Going say 50 or 60 watts on a 40 watt amp is more sensible. Speaker rated for the amp will cope with transient peaks - speakers used to be rated for program (continuous music) at X watts, single instrument RMS at 2X watts, and peak at 4X watts.

If you are constantly diming your amp and overdriving the front with a Metalzone you probably need the vastly overrated speaker. It will delay rather than prevent the inevitable pop. JBLs and EVs get toasted too.

But anyone who is using the amp as a musical instrument extension and not a vortex generator will be better off getting a quality speaker of about the same powerhandling as the amp output.

Note that overdriving the front of a small wattage amp through a big wattage speaker can still toast the speaker; they don't like being driven by square sine waves which comes awfully close to feedback. When that happens, the voicecoil tries to move the cone in and out at once. That's what fries coils, as well as too much power which can overextend the coil/cone.

[Ricky D.]

Originally Posted by Dacious

IMO I would match speaker spec to amp spec. Putting a 30 watt rated speaker with a 5w amp will only tend to dampen it, because the higher-rated components will be harder to drive. The voiceoil is like a spring, it has to be distorted through electromechanical energy to push the speaker cone and surround, thicker and stiffer in the higher-rated amp. Like putting 22" dubs on a Toyota Corolla. Same with 100 watts on a 30 watt amp. Won't hurt, wont be optimal.

Yes you can do it, and if you run the amp constantly dimed the higher wattage speaker will live better. But maybe in that case you should consider a more powerful amp.

Going say 50 or 60 watts on a 40 watt amp is more sensible. Speaker rated for the amp will cope with transient peaks - speakers used to be rated for program (continuous music) at X watts, single instrument RMS at 2X watts, and peak at 4X watts.

If you are constantly diming your amp and overdriving the front with a Metalzone you probably need the vastly overrated speaker. It will delay rather than prevent the inevitable pop. JBLs and EVs get toasted too.

But anyone who is using the amp as a musical instrument extension and not a vortex generator will be better off getting a quality speaker of about the same powerhandling as the amp output.

Note that overdriving the front of a small wattage amp through a big wattage speaker can still toast the speaker; they don't like being driven by square sine waves which comes awfully close to feedback. When that happens, the voicecoil tries to move the cone in and out at once. That's what fries coils, as well as too much power which can overextend the coil/cone.

Speakers just don't work like that. And electricity doesn't work like that.

A voice coil is nothing like a spring in any way whatsoever. The voice coil is not "distorted through electromechanical energy". There is no such thing as a square sine wave (it would be a square wave, not a sine wave), and feedback has nothing to do with waveforms.

The voice coil never tries to move the cone in both directions at the same time. The coil moves one way for a positive voltage, the other way for a negative voltage. If positive and negative voltages are applied at the same time, they superimpose and literally cancel out.

The idea that a high power rating means a poor sound in lower power operation just isn't supported in reality. If it sounds good loud, it will sound good soft. Have you seen an amp that sounds good loud or soft?

Now, high power speakers cost more. So there is an argument for not over-specing the speaker. It just isn't any of the arguments above.

[Dacious]

I guess my wording was sloppy. A 'square' sine-wave doesn't mean it has to look like a i/o block i.e. on or off.



A severely clipped sine wave will cause a speaker to try to move in and out at the instant it reaches the squared-off part of the curve, At that point the speaker can't respond.

Instead of smoothly transitting the peak and riding the sinewave back past centre. Because the flattened off portion to the speaker looks like DC - it's stopped alternating. If I put a 9v DC battery across the poles of a speaker it will move one way and stop and the coil will heat up very quickly. There's no squeal because no variation in voltage/current. Would be if there was a cycling wave clipping on the other side. The squeal is the bounce between the two.

As to there being no difference in sound quality on a low power amp with much higher rated speakers.:

Tweed Deluxe using Eminence Legend 12 alnico, 20 watts. Low-power rated speaker. Light cone, small voicecoil, small magnet, small gap. Low power rating. High efficiency.

Similar response chart and efficiency to:

PV Scorpion - bigger voicecoil, bigger gap, stiffer cone and surrond - less small amplitude compliance but much greater power handling @ 125 watts. Bigger magnet, more dampening. Less response. Lower resonant frequency. Sure - it will never develop cone cry or distort.

But it also loses a lot of the sparkle of a Tweed Deluxe. Sounds darker, less volume output.

'Distorted through electromechanical energy' is not perhaps the correct wording to use, as coil doesn't stretch like a spring - it travels. But it does resonate and is heated up a lot, hence suffers distortion - not of the audible type unless it scrapes the housing. Why there's a gap in the voicecoil between the former and housing, which is greater for larger coils and higher power handling.

I'd agree: anything that sounds good, is good. But automatically putting high-wattage speakers with a low wattage amp doesn't necessarily make sense. The coil still has to move over the magnet or magnet tube despite the stronger pull of the larger magnet, and pushed by less power still has to bend/stretch the stiffer cone and tighter surround to respond. The greater gap means lower amplitudes are likely to be less effective in moving the coil.

Poorly responsive, low-efficiency, speakers will sound crap, high-wattage or low-wattage rated.

The odds of gettting a highly responsive, highly efficient high-power speaker for anywhere near the same price as a highly-efficient, highly responsive low-power speaker are small. Unless you're talking Cel Blue which is sort of a special case.

I've sure seen 400 watt dual speaker cabs filled with 15" JBLs ruined in ten minutes by a guy funk-slapping a bass through a 200 watt head without a crossover and horns. Not much clipping, but repeated small excursions still within the peak capability of the speaker. He left them a buzzing mess. The rehearsal studio wondered why he quickly left so soon after arriving and hiring them.

So to me, if the reason for using higher rated speakers is better sound, I'd say not in my experience unless you're comparing very poor speakers with very good ones. If for avoiding damage due to abuse I'd say sure - but why not just not abuse them?