What's to chat about?

[Grant Bunter]

You're completely right Grant. I did say "assuming", however it wasn't a blind assumption. I intentionally ruled that out of the equation for the sake of conversation. It's intended as part of the construct of a hypothetical situation. And you're right that it's real and matters. But, it's not impossible for a 3 way system to have nearly identical impedances at some point in each drivers bandwidth.

For instance, this plot is essentially 4.5Ω at 60Hz, 600Hz, and 6000Hz.



Are you seeing the logic in my line of inquisition? It's still not making complete sense to me. I'm still in a state of quandary. Does it make sense to you?

I do.

I wonder if you considered when looking at the chart you put up, that what you're looking at is the sum of impedance across the cabs bandwidth.

I know you're simplifying it for the sake of discussion, but it's also around 4.5ohms at 150Hz and 10K as examples.

Go back a step.
Look at each driver chart in the three way system. You will see that each chart contributes to the "sum" chart.

So, one could extend the immutable fact "impedance is frequency dependent" further to: "impedance is frequency dependent, but different drivers may/will/do have different impedance at the same frequency".

Other than that, impedance is resistance and reactance. It's reactance that alters impedance on a frequency dependent basis, not resistance. Resistance stays the same regardless of frequency.

To alter power in P = I x V, you would need to alter the value of 1 item in V = I x R to do that. So, if resistance stays the same , and current is constant, V can't change. Current is already constant, and so is voltage, so power stays the same...

[Rich4349]

Oh this guy is FUNNY!

For those of you who took stuff apart as a youngster and haven't seen or heard of an AvE BOLTR video, you're welcome.

[himhimself]

For those of you who took stuff apart as a youngster and haven't seen or heard of an AvE BOLTR video, you're welcome.

No, Seth. No. Not welcome. Another way to waste endless hours. Geez, stop already... No wonder I can't get my projects finished.

[Seth]

Nope. The power is split 3 ways. 1+1+1 in this case equals 1. Besides, discussing sine waves doesn't really relate to discussing sound waves, which are not only complex, but the power density drops by 3dB with each octave increase in frequency. A tweeter rated for use in a 100w system will seldom see more than 5 watts, while 75% of the power is typically below 500Hz.

So, I'm guessing that if the signal amplitude into the 3 way crossover was 10v, it wouldn't measure 10v at any of the speaker terminals. Is that correct?

[Bill Fitzmaurice]

Do so with pink noise and you'll see that's the case. Pink noise is used for testing because it more or less duplicates the spectral content of music. Music is never used because the content is too dynamic.

[Seth]

I do.

I wonder if you considered when looking at the chart you put up, that what you're looking at is the sum of impedance across the cabs bandwidth.

I know you're simplifying it for the sake of discussion, but it's also around 4.5ohms at 150Hz and 10K as examples.

Go back a step.
Look at each driver chart in the three way system. You will see that each chart contributes to the "sum" chart.

So, one could extend the immutable fact "impedance is frequency dependent" further to: "impedance is frequency dependent, but different drivers may/will/do have different impedance at the same frequency".

Other than that, impedance is resistance and reactance. It's reactance that alters impedance on a frequency dependent basis, not resistance. Resistance stays the same regardless of frequency.

To alter power in P = I x V, you would need to alter the value of 1 item in V = I x R to do that. So, if resistance stays the same , and current is constant, V can't change. Current is already constant, and so is voltage, so power stays the same...

I understand all of that very clearly. And again, I intentionally removed it from the conversation to better focus on the other variables. I'm happy to discuss impedance. It's just a separate discussion and it's own ball of wax.


Consider using 8Ω resistors in place of a speaker.

Single sinewave or a complex waveform made up of several sinewaves: Amp to one resistor, amp see's 8Ω. 8.94 volts measured at the amp output is 10 watts.

Amp, to a 3-way crossover, to 3 resistors... one on each output of the crossover. Amp still "see's" 8Ω nominal. 8.94 volts is still 10 watts out, but with a complex waveform filtered into one sinewave per resistor. It's impossible to have 30 watts out of the crossover if there's only 10 watts in, so the only way I see that working out is there must be less than 8.94 volts at each crossover output. I'm curious what it may be. Would the power available at the crossover input get split evenly across the 3 outputs? 5.16volts/3.33watts at each?

If the 60/600/6000 Hz numbers were used, would one of them measure higher and one lower than the rest? All the same?



If you really want to include impedance in the conversation...
If we do take into account the variable impedance of a driver, a whole slough of additional questions arises... If adding more sinewaves to an initial sinewave doesn't change power in and of itself, it makes sense that the resultant power would default to whichever sinewave occurs at the point of lowest impedance for the driver. True? Dunno. If so, do all the other sinewaves and the impedance at which they occur, have zero effect to the resultant power? Or, do they accumulate and calculate the same way as adding multiple Ω value drivers to a circuit? In other words, if one sinewave occurs at a point that the driver has 45Ω (resulting in 1.78 watts with a 8.94 volt signal) and the second sinewave occurred at a point that was 10Ω (8w at 8.94v) would the amplifier be putting out 8 watts based on the least impedance or is it variable based on all that occur in the moment? If the 10Ω frequency was played first, would the effective impedance change (and thus power) if the 45Ω frequency is added in too?

And now it's pretty clear why I eliminated the impedance variable from the start... it's too complex to address all of it at the same time. Pertinent? Yes. But also adds confusion where it could be avoided and simplified by it's exclusion.

Honestly, if impedance is what you want to talk about, I'm very much game. It's just that it skirted and skewed the question I have. That is, unless I missed your point Grant. Completely possible too.

[Grant Bunter]

You've already been told by Bill it's about power density and were prepared to accept that.

In a three way system, the input voltage, or watts, if you prefer, are paralleled three ways to three filters.
You're not providing 10watts or volts to to each of three different filters, you're providing the same 10 W or V to the three filters to provide adequate power to get the response from the cab you want without blowing the drivers.
Massive difference.

Each filter consequently has the same input, but the filter itself is designed to not only affect frequency, or a frequency pass band, but applies a power correction (eg "corner frequency of 2K with 12dB reduction in power"), as, only the "woofer" can handle the higher power. The "lesser" drivers will blow with the same power.
Any "excess" power, as always, is dissipated in heat, and the inefficiencies, of the drivers it's applied to.

There is no point banging on about resistance, see my earlier post.
Reactance is another thing...

[Seth]

Hmmm...


Interesting writeup Grant. It's not entirely clicking upstairs, which is a good thing. I'll let that sink in a little and re-read it a few times.


And Bill, I did hear and take note of the two times you eluded to power density. I'm rolling that around in the attic too.

[Seth]

You're the one with the wacky ideas and experiments- you tell us! No offense meant, I admire your excursions into the (semi)-unknown!

Didn't know how to respond to this Rich. I assume, like many/most of you/us, I check the site daily for something interesting to read. Well, that's an assumption. I do, anyway. When there's nothing going on, I take it upon myself to introject a little stimulating thought... or whatever I'm thinking in the moment. I completely admit that my personal curiosities and questions are beyond normal inquisitions. Completely.

But, really... when you check the site for new posts, are you really looking to regurgitate the same info that's here already? Voltage limits (personally, still out to lunch on the absolute imperativeness on that one), IITP, will this driver work, how many cabs do I need, is there a cab for an 18" driver... all the standard questions. Is that all us as regulars are here for???

Not me. I enjoy exploring this hobby. For me, it's more than "hoorah for Bill Fitsmaurice designs". It's more than horns rule. To me, we have a quaint little group of guys that can shoot the shit about the little in's and out's of audio. A tight group that can share experiences. A group that is interested in the same stuff. Aren't we? Seems we are.

I'll tell ya... I'm into engines. But not like V8 vs. V6. I'm into them at a molecular level... Stoichiometry, the effects of non-stoichiometry on combustion, thermodynamics, thermal management, sonic choke, airflow efficiency, convergent-divergent nozzles ("rocket science")...

I do have "whacky ideas". I do express curiosities. I do find answers.

And really, the only reason I bring them here is so we (you and others) have something to read about when you're drinking your morning coffee. And I hope that, as internet friends, we have something to talk about.

If the consensus is that I'm a whacko and ya'll would rather I don't post this kinda stuff, I won't waste my time. It just seems to me that it's better to have something to read than nothing. And the expansion of the mind and our craft is valuable.

But, that's just me. And, I'm different... apparently.

We should converse openly. Agree and disagree. Discuss stuff. I enjoy all of you and relating to all of you. Isn't it incredible that we're spread across the globe and we're all here at the same place, thanks to this website? (thank you Bill) It is to me, and I appreciate all of you... even if you think I'm weird. (I am)

"You're the one with the wacky ideas and experiments"... I do truly take that as a compliment even if it's not meant to be. It's true. I am.

[Tom Smit]

But, that's just me. And, I'm different... apparently.

You too?

We should converse openly. Agree and disagree. Discuss stuff. I enjoy all of you and relating to all of you. Isn't it incredible that we're spread across the globe and we're all here at the same place, thanks to this website? (thank you Bill) It is to me, and I appreciate all of you... even if you think I'm weird. (I am)

[Bruce Weldy]

If the consensus is that I'm a whacko and ya'll would rather I don't post this kinda stuff, I won't waste my time. It just seems to me that it's better to have something to read than nothing. And the expansion of the mind and our craft is valuable.

Hey Whacko! This is your thread - you can post any damn thing you want to!

Seriously, the site has slacked off over the last couple of years - not nearly as many guys coming on to ask questions and post their builds. Who knows, that may turn around. In the meantime, it's a place to talk to guys around the world with a common interest......so, you just keep throwing stuff out there to talk about. Just be forewarned.....if it's way over my head, then I'll probably just make fun of you.

[himhimself]

If the consensus is that I'm a whacko and ya'll would rather I don't post this kinda stuff, I won't waste my time. It just seems to me that it's better to have something to read than nothing. And the expansion of the mind and our craft is valuable.

Hey Whacko! This is your thread - you can post any damn thing you want to!

Seriously, the site has slacked off over the last couple of years - not nearly as many guys coming on to ask questions and post their builds. Who knows, that may turn around. In the meantime, it's a place to talk to guys around the world with a common interest......so, you just keep throwing stuff out there to talk about. Just be forewarned.....if it's way over my head, then I'll probably just make fun of you.

+1 Thanks for keeping things interesting, Seth!

[Rich4349]

Oh Seth, I sure didn't mean that as an insult or discouragement. On the contrary, I also enjoy your explorations. I'm usually the boundary finder in my neck of the woods, so I am right there with you finding "new ways to get there."
Don't stop being you and doing your thang- you may be a Tesla or Edison in the making!

[Seth]

Well okay then! Thanks guys. I appreciate the words Rich. You did say no offence intended. It just read a little sideways on my end, which is really my responsibility anyway.

Moving right along then

So, here's what I'm thinking. My mixer has a tone generator which I can assign to a channel and a bunch of my Ashly amps also have a tone generator which I can assign to the signal pass through/out of the amp, which I can patch into two other mixer channels. So, I'll have three independent sinewaves that can be individually mixed and muted.

I should probably pick up one of those kill-a-watt meters to monitor amplifier power consumption. I'd also like to have an amperage reading on the speaker outputs too. Not sure about how I'd go about doing that yet... and some 8Ω 100w resistors.

I got a basic oscilloscope as a gift this past year. I'd don't have the slightest idea how to use it yet. But, with a little googling, YouTube, and friendly pointers I'm confident we'll be able to see what we want to see.

I'd like to test 1 and 2 sinewaves (maybe 3) into a static load. I expect the results to be just what Bill said. No change as long as the maximum amplitude hasn't changed.

Then I'd like to test with a passive crossover. Three way crossovers are kinda spendy just to fiddle fart with. So, I'm thinking of just testing with a 2way crossover. It'll be interesting to see what comes out of the passive crossover. Waveform and voltage.

Then run the same tests, but through an active crossover and separate amplifier channels.

It'll be interesting to see how cleanly the crossovers separate the frequencies into their original sinewave, where and how the "Power" is distributed, and where losses occur.

[Grant Bunter]

^ Just remember that amplifiers put out AC volts and current.

You could probably do most of part 1 simply by multiple calculations, and confirm with a half reasonable multimeter.

And, also remember that resistors are used to reduce current flow, adjust signal levels, to divide voltages, and bias active elements.
As they heat up, and approach their limits, resistance may increase or decrease. Immediate variable.

Ducks guts, don't run your tests for a long time. Something will have to give, probably your amp.

How well do you understand passive crossovers? There's shunts to ground and heat I would suspect as immediate losses.
In order for you to quantify results, you need to know exactly what type of crossover you're using.

Someone much smarter than me once said "Energy can neither be created nor destroyed, it can only be transformed to another form of energy".
I only throw this in because, you might find that the expectations don't match the results. Doesn't mean that the expectations are wrong though, because there are intangible or insensate losses, losses you may not be able to or can't identify. But the energy in has to = the energy out. In which ever form it takes...