First Audio Build (Need Math Help!)

[Xbdition]

Originally Posted by stugray

That's what I am saying: Take a "4.0 Ohm" speaker and measure the resistance across the coil, it will not be 4 ohms.

Impedance is not the same as resistance.
You cant just measure it with a DMM and add it up like they are resistors.

I like your sig quote. It's not always engineers either.

[stugray]

Originally Posted by Xbdition

Does all the discussion about whether distortion kills speakers or not really matter? The pointless distinction that people make is that its not distortion "alone" that kills speakers. So what? Would you ever recommend someone drive their amps with a distorted signal even if they only listen at low volumes? The added harmonics may not sound bad at low volumes, but it would still be a stupid suggestion to run a distorted signal.

Take for example a speaker rated for 50watts thermally. Why even discuss whether that speaker could thermally handle 10 watts of a square wave? That 50 watt thermal rating is not for a clipped signal and a speakers thermal rating goes out the window when you are sending a square wave. So much hot air. See what I did there?

I AM SAYING that yes I could probably ruin a 100 watt speaker with a 50 watt amp if I can use an amp of my choosing.

I do Acoustic testing of Billion dollar spacecraft for a living.
We Hire Maryland Sound to bring their entire speaker stack every other year or so.
We are doing it again in ~Jan/Feb.
Maryland Sound could only drive their whole speaker stack at max power for a few seconds with the waveform WE ask them to run OR THEIR SPEAKERS OVERHEAT.
They can do all day long concerts while driving the system with plain old MUSIC.

I also personally helped Lockheed Martin built their Reverberant Acoustic Test Facility for testing the Atlas Launch Vehicle and spacecraft, but whatever you say.
I dont know what I am talking about.
Now back to our regularly scheduled Internet Expert hour.

[Xbdition]

Yes, we are on the same page. Perhaps if you read closer you will see I wasn't addressing you. In fact, I hadn't even really read anything you wrote until you responded to my post.

Gotta say though, I reaaaallly love it when people rattle off their resume when they feel questioned. Internet expert hour, thats a nice one.

[TOOSTUBBORN2FAIL]

Originally Posted by stugray

Attempting to drive a speaker with a mismatched impedance can over heat the speaker drive coil, the amplifier, or both.

Another thing that can overheat a speaker is by driving it in a way that it cannot respond.
If a speaker is given a drive current that it cannot respond to (say too high of a frequency on a very large {heavy} cone) the result is not movement of the cone, it generates heat in the coil.

So if you have a set of speakers that cannot respond to a large range of frequencies yet you try to drive it simultaneously at a large set of frequencies, the speaker coils will get hot.
Another way to say "large set of frequencies" is a "spread spectrum".

Classical music is typically composed of a small number of pure frequencies so will look like a forest of trees on a spectrum analyzer.
This type of signal is typically easy for a speaker system to respond to.

The example of Slipknot is a perfect example of a wide-band spread spectrum "NOISE".
This type of signal will look like more level "sea" or noise floor on a spectrum analyzer.
Speaker systems typically cannot respond to NOISE as well as they can respond to TONES.

Trying to drive speakers with noise will invariably heat the coils more than driving them at pure tones (within the response of the speaker coil/cone system).

Therefore I will repeat:

"So you could blow a speaker playing slipknot but NOT blow the same speaker at the same volume playing classical Beethoven."

Driving at high levels of distortion is the same as adding noise.

I'm on my phone, so ill be short.

Classical music is not "pure tones". It is the combination of pure tones and harmonics from the instruments. This is why no two violins sound the same. The reason that classical music looks like "Christmas trees" on a spectrum analyzer is because classical music is generally mastered well, and has maintained it's dynamics, instead of being brickwalled. The reason slipknot looks like "a seabed" is because it is brickwalled, and clipped during mastering.

As an aside, this is the only benefit of vinyl records over cds, better mastering. You can't brickwalled a record the way you can digital because it won't function correctly.

Again, if played at the same volume, slipknot will be sending more power to the speaker than beethoven because of this difference in mastering. Slipknot has a crest ratio of about 6db, the same as pink noise. Well recorded beethoven should have a crest ratio more around 15-18db. This means on average, over time, slipknot is sending 8-16 times more power to the speakers than beethoven.

[TOOSTUBBORN2FAIL]

Originally Posted by Xbdition

Does all the discussion about whether distortion kills speakers or not really matter? The pointless distinction that people make is that its not distortion "alone" that kills speakers. So what? Would you ever recommend someone drive their amps with a distorted signal even if they only listen at low volumes? The added harmonics may not sound bad at low volumes, but it would still be a stupid suggestion to run a distorted signal.

Take for example a speaker rated for 50watts thermally. Why even discuss whether that speaker could thermally handle 10 watts of a square wave? That 50 watt thermal rating is not for a clipped signal and a speakers thermal rating goes out the window when you are sending a square wave. So much hot air. See what I did there?

No one is suggesting using a distorted signal. It's important to know the real cause of speaker damage though, and it's not clipping, or distortion, or not sending them enough power. The VAST majority of music now days is clipped, if it was the case that distortion killed speakers, few speakers would still be working.

[stugray]

Originally Posted by Xbdition

Yes, we are on the same page. Perhaps if you read closer you will see I wasn't addressing you. In fact, I hadn't even really read anything you wrote until you responded to my post.

Gotta say though, I reaaaallly love it when people rattle off their resume when they feel questioned. Internet expert hour, thats a nice one.

Sorry, I mixed you up with TOOSTUBBORN.
And my "rattling off of my resume" was to point out that I am more than a Internet "Expert" I actually DO this stuff.
It was relevant.

[TOOSTUBBORN2FAIL]

Before assuming I'm some "Internet expert" that doesn't do this stuff, let me dispel that. I build high end sound systems. My last car was a state sound quality championship level build. I was trained in electronics by my dad, who has a master's in physics and has designed power supplies for the military, nasa, and many other industries where failure can be catastrophic. I also play the violin, and master music as a hobby.

If you can prove what you are claiming, I will listen. I can objectively prove what I am stating. Tomorrow I will load up some varying music on the computer and post the spectrum analysis of each.

[MidnightMonkey]

I think i'm gonna just figure it out on my own...

[Mr.ac]

Ok....... That was a lot of useless talk. To the op,
Yes you can use those speakers. I'm assuming they are a component set up. So yes do use the crossover.
As for your amp, any and I mean any new name brand amp can handle 2 ohm loads.
1, 2, 4, 6 channel amps are can handle lower ohms.

So yes go ahead use it you'll be fine.

Most of the time you kids love to over think shit.
Polk makes awesome car audio stuff. They also know that their stuff will work with any head unit and amp that with in their wattage range.

[MidnightMonkey]

Originally Posted by Mr.ac

Ok....... That was a lot of useless talk. To the op,
Yes you can use those speakers. I'm assuming they are a component set up. So yes do use the crossover.
As for your amp, any and I mean any new name brand amp can handle 2 ohm loads.
1, 2, 4, 6 channel amps are can handle lower ohms.

So yes go ahead use it you'll be fine.

Most of the time you kids love to over think shit.
Polk makes awesome car audio stuff. They also know that their stuff will work with any head unit and amp that with in their wattage range.

I'm gonna try to run all of the drivers off their own channel using a 4 channel amp. Since that removes the passive crossover, each speaker's impedance should be 2 ohms. I just noticed the back of the midbass clearly state 2.

I'll probably pick up an omni-directional mic too and start messing around with time alignment and EQing to the speakers themselves instead of by ear. Just to see what that yields.

I love Polk's older home audio stuff. I'm kinda sad to see the direction they've been going in.

[Shankenstein]

Mine's bigger.

[Mr.ac]

Originally Posted by MidnightMonkey

I'm gonna try to run all of the drivers off their own channel using a 4 channel amp. Since that removes the passive crossover, each speaker's impedance should be 2 ohms. I just noticed the back of the midbass clearly state 2.

I'll probably pick up an omni-directional mic too and start messing around with time alignment and EQing to the speakers themselves instead of by ear. Just to see what that yields.

I love Polk's older home audio stuff. I'm kinda sad to see the direction they've been going in.

Ah I see. Yes that would still work out fine.
Now question is what kind of amp do you plan to get/have?
I hope the amp has a nice crossover set up built in. Or have an external kick ass independent eq then signal it to the amp. Otherwise it's useless to have a mic and adjust the gains/levels on the head unit/amp alone.

[TOOSTUBBORN2FAIL]

His headunit has 16 band eq, time alignment, and very flexible crossovers built in.

[MidnightMonkey]

Originally Posted by Mr.ac

Ah I see. Yes that would still work out fine.
Now question is what kind of amp do you plan to get/have?
I hope the amp has a nice crossover set up built in. Or have an external kick ass independent eq then signal it to the amp. Otherwise it's useless to have a mic and adjust the gains/levels on the head unit/amp alone.

I can't decide on an amp. I really don't know who makes quality, reliable stuff.

The DEH-80PRS has a 16 band EQ for left and right and time alignment adjustments. I'm gonna start off using it's settings to see what I can make happen. I'm sure it'll be better than anything I've ever set up before, which hasn't been much. All the reviews I've read on it have been excellent.