[Maxamus]

A few questions for you knowledgeable guys. Could someone explain to me what the following refer to interms of speakers:

* Frequency Response
* Sensitivity
* Crossover


Example.

Speaker A:

* Frequency Response: 80Hz - 18Khz
* Sensitivity: 89 dB/w
* Crossover: None

Speaker B:

* Frequency response: 43Hz - 40kHz
* Sensitivity: 88 dB/w
* Crossover frequency: 280Hz - 2.8kHz


Which is better, and how and why?

[Russ7]

You can't really say that either of those speakers is better, as we are only presented with some technical performance details.

I'll explain the terms you've listed for speaker B

Frequency response: 43Hz - 40kHz
Frequency response is usually defined as the -3dB of a speakers response to a flat input. Ideally this means that the speaker produces a flat(ish) response between 43Hz and 40kHz in the speaker B example. At 43Hz and 40kHz its response is 3dB less than that of the flat response between those frequencies.

If you do a search for images of frequency response, you'll see a graph of what I mean.


Sensitivity: 88 dB/w
This is a measurement of how much acoustic output is produced by the speaker with reference to electrical input (basically how efficient the speaker is).

Crossover frequency: 280Hz - 2.8kHz
In the case of a two-way speaker (two drive units, ie mid/bass and tweeter), the input signal needs to be split, to send high frequencies to the tweeter and low to the mid/bass, a crossover splits this signal at a certain frequency. In the case of Speaker B, its either a three-way speaker with cross-overs at 280Hz and 2.8kHz, or (this option I don't think is the case though), its a variable crossover.

Neither speaker is 'better'. I can only comment on the differences;

Speaker A is ever so slighter more efficient (Sensitivity)

Speaker B covers a wider acoustic range (ie, lower bass and higher treble)

Speaker B is probably a three-way speaker, with inbuilt crossover. Speaker A is possibly a full range speaker (ie one type of drive unit), with no inbuilt crossover.

hope this helps.

[phil t]

Originally Posted by Maxamus

Which is better, and how and why?

As Russ says, it’s impossible to say which one will sound better based upon technical figures.

Are these real speakers that you’re trying to decide between?

[Mark.Yudkin]

Just to expand on Russ's answer with the maths:

1) Although the "norm" for frequency responses is -3dB at the extreme, many speakers today quote at -6dB (!), hence it's important to consider this part of the spec. 1 Bel (10 deciBel) means a factor of 10 (it's a log10 scale), hence -3dB is 10**0.3 ~= 0.5 the power (Sound Pressure Level) and -6dB is 10**-0.6 ~= 0.25 of the power (SPL). From a hearing perspective, -1B is generally considered to be between "half" and "third" as loud. From an amp perspective, you need 10 times the power to achieve 1Bel, or roughly twice the power for each 3dB.

Human hearing tops out at 20Hz - 20kHz, achievable by a select collection of young children. If you're a young female adult, you might still be close, if you're a male adult, you're probably already maxing out well below 18kHz. A speaker quoting "40kHz" is playing a number's game.

2) Sensitivity is the SPL an is usually measured at 1 metre and 2.83V. Since W=V**2/Z, this is the same as 1 Watt into 8 Ohms. As you move further from the speaker the power drops to 25% (factor 4, -6dB) per doubling of distance (sound covers an area). So 89dB at 1m is 83dB at 2m, 77dB at 4m, etc.

As Russ and Phil have said, your last question cannot be answered based on these figures.

[phil t]

Originally Posted by Mark.Yudkin

Human hearing tops out at 20Hz - 20kHz, achievable by a select collection of young children. If you're a young female adult, you might still be close, if you're a male adult, you're probably already maxing out well below 18kHz. A speaker quoting "40kHz" is playing a number's game.

Not forgetting that the highest frequency reproduced by a cd player is around the 22KHz mark.

[BlueWizard]

Excellent responses from all.

In your A and B speaker example, I would say, speaker 'B' has better specs, but that doesn't mean it is a better speaker. Though in general, a single cone speaker, unless it is massively expensive, is going to have some problems.

Here is a link to a frequency response graph for a single cone speaker.

Goldwood GW-8003/8 8" Full Range Driver w/Whizzer

http://www.parts-express.com/pdf/290-379g.pdf

Notice how uneven everything gets above 1khz. This is typical. Now the speaker in the link above is only US$25, so we can't expect miracles.

However, here is a link to a single Dayton 4" single cone full range speaker that has been equalized with a graphic equalizer to produce amazing response.

HTGuide Forum - " Full Range " Dayton RS100S project

Compare the two graphs in post#1 with the graph the link at the top.

As pointed out, the frequency response rating is either -3db or -6db down from the average level. Three db is a slight but noticeable change in the sound level, but it represents a doubling or halving of the power levels.

But the tuning of the speaker cabinet has a great deal to do with how you perceive the bass level. You can tune a cabinet to have a slight peak in the bass, but that means, below the peak, it drops off at a faster rate. If this cabinet tuning get too extreme, you have a cabinet with what is called 'one note bass'; in other words, a typical 'boom' box.

Using this cabinet tuning technique, you can make a speaker that has poor low end response sound like it has good bass. So, the Speaker 'A', could sound good, yet still have a seemingly poor 80hz cutoff on the low end.

As to Sensitivity, initially, upon its inception, it seemed like a good idea since it provided a way to compare all speaker with the same input. Typically it is measured with a calibrated microphone and an Sound Pressure Level (SPL) meter at a specific level at a specific distance.

But a controversy occurred. Should speaker all be fed the exact same signal, 2.83 volts, or should the be fed the same power (1 watt). Speaker are actually voltage driven devices. You feed them a voltage signal and they consume power. So, that school of thought says the fair way to compare speakers is with a fix and known (2.83v) signal.

Other say if you feed 1 watt to an 8 ohm speaker, then you should feed 1 watt to a 4 ohm speaker. But the voltage necessary to feed one watt to a 4 ohms speaker is 2 volts, and the voltage necessary to feed one watt to 16 ohms is 4 volts. To get these voltages, you are either turning the volume control up or down to reach one watt. But how can you say you compared two speakers equally when you turned the volume up or down for one of them?

So, frequently if you look at full specs, it with either say, 90db at 2.83v measured at 1 meter. Or it will say, 90db at 1 watt measured at 1 meter. Unless the speakers are both 8 ohms, that's not necessarily a fair comparison.

Most have adopted a uniform 2.83 volts, others choose which ever method gives them the better numbers.

The crossover frequencies are nice information to have and give you some sense of the underlying design philosophy, but you can't really make a value judgment based on that information. Again, it is just nice to know information.

So, I guess when you add it all up, even though there seem to be standards for these various rating, they are not all that standardized. For example, if you want to inflate your frequency response, that is, make it seem lower and higher than it really is, you simply quote it at -6db instead of -3db. Typically that will gain you roughly 5hz or possibly a little more on the low end.

If you want higher apparent Sensitivity, you test it at both a fixed 2.82volts and a 1 watt and use which ever number is higher.

Remember from above, that 3db represents twice as much power. So, if you have two speakers, and one is rated at 90db and the other is rated at 87db, the 90db speaker is going to take half the power to reach a given volume.

But also remember that power and volume aren't linear. It takes 10 TIMES the power to double the volume, and a slight but noticeable change in volume represents a doubling of the power. So, in the example, even though it takes twice the power for one speaker to equal the perceived sound level of the other, that is only a slight difference in perceived volume level.

So, the conclusion is that you can't rely totally on specs. They do give you valuable information, but nothing tells you more than a good long listen to the speaker using material you are familiar with.

So in summary -

Frequency response is the working range of the speaker. But the sound doesn't absolutely cut off at those frequencies. At those rated frequencies, the sound has started to roll off or fade, and continues to fade on a shallow downward slope. You do get sound below these rated level, it is just reduced sound. So, even a speaker rated at 40hz might still allow you to hear 30hz noted, they just won't be very loud.

Sensitivity is a supposedly standardized method of indicating a speakers efficiency. The higher the number the more efficient the speaker is. Most speaker are in the range of 85db to 95db, with most being in the high 80's and a few in the low 90's. This is mostly a concern if you are using a low powered amp. But it does give some way of making a relative judgment on a speaker.

Crossovers are neither good or bad. If you have a speaker with more than one driver, it must have a crossover of some type. The specific frequencies can give you some underlying sense of the design, but there is nothing you can do about them. The selected frequencies have been matched to the specific speakers, and must be where they are.

Another aspects of a speaker, is whether it is ported or sealed. Ported speakers are generally more efficient, but that doesn't mean sealed speaker sound worse. A seal speaker or acoustic suspension or infinite baffle speaker and better control cone movement, and in better speakers, can actually sound better.

Ported cabinets or Bass Reflex cabinets have an extra hole or opening cut into them which is tuned by a tube or port to a specific frequency; usually a very low frequency. This raise the overall efficiency of the speaker and cause it to resonate at a predetermined low frequency that help re-enforce the bass.

Either cabinet design done wrong will sound bad, but, if done right, either type can sound very good.

Ported cabinets come in various type. They can be front ported, rear ported, and technically the port can be on the bottom, the top, or the sides, it really doesn't matter.

Rear ports are more common now, but it is mostly a trend. The problem with rear ports is they require a certain amount of distance between the speaker and the wall behind. Many living rooms are too small to accommodate this distance. Though, fairly, the distance is only significant for larger speakers.

Just a few additional thoughts.

Steve/bluewizard

[Maxamus]

Wow thank you very much for the detailed responses.

Speaker A is the Anthony Gallo Micro
Speaker B is the Kef IQ5SE floor standers

i just wanted to know how they compare.
I have the Kef's as the fronts and the Gallo's as center and rears

[Sawdust]

Originally Posted by Maxamus

Wow thank you very much for the detailed responses.

Speaker A is the Anthony Gallo Micro
Speaker B is the Kef IQ5SE floor standers

i just wanted to know how they compare...

Don't get too hung up on the measurements, just listen to them both and buy the ones you like the sound of the best. Of all the things in the sound reproduction chain, speakers are the hardest to judge by how they measure

Mike

[BlueWizard]

Speaker A is the Anthony Gallo Micro
Speaker B is the Kef IQ5SE floor standers

Well, now that we've answered your question, you have to establish some context for it. It seems odd that you are considering these two VERY different speakers.

Unless I am mistaken the Anthony Gallo Micros are small globe shaped speakers, and you are comparing these to the very substantial Kef floorstanders? Again, it seems odd that you would compare two such seriously different speakers.

How do they compare on price?

Likely, the Anthony Gallo are not meant to be stand alone speakers, but speakers specifically intended to be part of a system the certainly includes a Sub.

But the Kef floorstanders should stand alone nicely as either stereo speakers or speakers in a surround system.

So, again, please establish some context as to why you are comparing such an odd pair of speakers.

Steve/bluewizard

[Axl]

Originally Posted by Maxamus

i just wanted to know how they compare.
I have the Kef's as the fronts and the Gallo's as center and rears

Originally Posted by BlueWizard

So, again, please establish some context as to why you are comparing such an odd pair of speakers.

Steve/bluewizard

.

[BlueWizard]

W Axl Rose,

Thanks, I missed that part.

Steve/bluewizard

[Russell.Williams]

Yesterday, I started typing this:

Speaker A has no crossover so is a single full range driver.

Speaker B has two crossover points and is therefore a three way system which given that it contains driver dedicated to a specific part of the frequency spectrum, explains why it can achieve both higher and lower frequencies simultaneously.

Speaker A could be a single four inch Jordan driver in a small sealed box, or it could be a large electrostatic panel.

Speaker B is more likely a moderate box, possibly floor-standing.
I then got tired and went to bed, but the window was still open when I got back to me pooter this evening.

I wasn't that far out, although in the context of the intervening discussion I'd I'd take a look at dumping the Gallo centre and have a look at the iQ6c as a matching centre. It would be a tonally and dynamically superior match.

I'd also add that whilst only schoolgirls and bats can register over 18kHz, if being young or furry was all there is to hearing quality treble, then tweeter development would have stopped with the KEF T27 in about 1982. In reality, a treble unit's ability to reproduce ultrasonic frequencies cleanly, has a bearing on it's capabilities within the audible band so whilst not total proof of a driver's quality, it does have a bearing on it. There are plenty of sources that will output ultrasonic frequencies these days and if they're not handled cleanly, then the dome's breakup modes will affect treble quality within the audible range.

If you think this isn't an issue, then you probably think electrostatics are the last word in speaker fidelity.

Russell

[Axl]

Originally Posted by BlueWizard

W Axl Rose,

Thanks, I missed that part.

Steve/bluewizard

No worries. I enjoy your comprehensive posts, didn't want to see you carry on down the same track after missing what Maxamus had written.

[Jeroen1000]

I hope the TS doesn't mind me asking a question too. It's all related and so may be useful.

Can someone elaborate on what sets a high-end speaker apart from a 'cheaper' one?

Take a loot at my set here: http://www.techarp.com/review/Logite..._specs_big.JPG

As you see the frequency response is quite good. I'm neither a bat or a young schoolgirl so there isn't much more to gain in that area.
The rated sound pressure level is 115 dB. I'm not quite sure what that means (although already explained here I know). It appears to be rather high to me.
Lastly, what does input impedance mean?


Anyway, aside from the questions, this is a fairly cheap set and I think is has good specs. What makes the super pricey ones that much better than?

[phil t]

Impedance of a speaker is its resistance, capacitance and inductance, this is measured in ohms. It is normal to give impedance as a nominal figure, this is because capacitance and inductance vary with frequency. A nominal resistance of 8 ohms was “standard” for a long time although 6 ohms is becoming more common and 4 ohms is not unheard of.

Almost more important is the rarely given minimum impedance, this will give an indication of whether a particular speaker is a “tough” load ie the lower the minimum impedance the harder the speaker is to drive.

[BlueWizard]

On the speaker system spec sheet that was linked to. First, while the 1000 watts may be impressive, in reality, the subwoofer is a so-so 188 watts and the main speaker channels are a modest 62 watts, and we don't know the nature of those power ratings; are the peak power, dynamic power, RMS power, we don't know.

Since this is a package, that is probably enough power to drive these speakers. The power ratings are tolerable, but nothing impressive.

Next, 115 db is the MAXIMUM SPL (Sound Pressure Level) not the rated Sensitivity. It only takes 1 watt (or 2.83 volts) to any drive a speaker to its very substantial sound pressure levels of its Sensitivity rating. Add more power and it gets louder. I suspect 115db is painfully loud in a normal sized room. Also, while it may be able to make noise at that sound level, that doesn't mean that noise will sound good.

Now to the frequency response, 35hz to 20khz would be quite good for a single bookshelf or floorstanding speaker, and exceptionally good for an 'egg/pod' speaker. But, you are not seeing the response of the main speakers, you are seeing the response of the entire system.

Yes, the Sub many go down to 35hz, which is only so-so for a sub, but it is very unlikely that the satellite speakers are even close to that. So, again, that is not the response of one speaker, it is the entire system.

I suspect I sound very negative, but budget and personal requirements drive everything. For computer speakers, for a very modest budget movie system, or for a modest gaming system, this might be a good setup. Again, it depends on the price, for £150, it is probably a very good system, but for £1500, I'm afraid it is probably going to fall very short.

Anything you can use in there???


On Impedance -

Phil T is right, impedance is not fixed for speakers, even though speakers seem to have a fixed impedance rating. So, a speaker that is nominally 8 ohms is more or less sort of 8 ohms.

If you look at this PDF file for a Dayton 8" Classic woofer, over on the bottom right, you will see the impedance graph.

http://www.parts-express.com/pdf/295-310s.pdf

Also, before we go further, speakers have an Re rating; 'Re' meaning electrical resistance. This is the purely resistive aspect of the speaker, and you can see this on the chart at the top left of the PDF link above. Re for this particular 8 ohm speaker is 6.5 ohms which is typical. That is the lowest possible impedance this speaker can present to the amp.

Now the difference between Resistance and Impedance. With pure Resistance, voltage and current are always in phase. With inductors or coils, the voltage across the coil can shift so it is out of phase with the current. Capacitors works in the same way, voltage and current are out of phase, but shift in the opposite direction. This phase shift is frequency dependent.

So, impedance is a complex combination of resistors, capacitors, and coils. You will see a lot of electrical equipment rated in VA or Volt Amps. Volts times Amps equals Power (P = VxA). So if Volts times Amps equal Power, why rate something in VA instead of just rating it in Watts. The answer is Phase Angle. When the current and voltage are not in phase, the simple multiplication of Volts times Amps does not give a true indication of power at any given time. To get the true power, you need to multiply the [Voltage at it's phase angle X the Current at it's phase angle].

You don't really have to understand this part, its just for background.

So, if we look at the chart for impedance, we see, at low frequencies, it starts out at about 6.5 ohm the quickly rises to 45 ohms, then quickly drops back down to 6.5 ohms, then gradually rises back up to over 70 ohms.

Before we move to the next part, let me say that the low peak of 45 ohms at 31 hz is call the Resonance of the speaker. You can see this in the chart on the left as the fs specification. Now to some extent the peaks can be controlled. Bass Reflex or Ported Cabinets are more accurately termed 'Helmholtz Anti-Resonance Chambers'. By tuning the cabinet to resonate at the same frequency as the speaker resonance, we can make them resonate against each other, and keep that resonance peak in the speaker lower.

The gradual rise in impedance as frequency increases can be controlled with a Zobel network. Zobel networks are also used to stabilize the impedance of woofers at their resonance frequency. Just one drawback, Zobel Networks add resistance in parallel to the speaker, and can therefore, under the right circumstances, lower the overall impedance.

So, certainly we are concerned about how low a speakers impedance goes, but why do we care how high it goes? The answer is, the Crossover Network.

When you have more than one speaker in a system (eg: a woofer and a tweeter), we have to separate out the frequencies and make sure only highs got to the tweeter and only lows go to the woofer. We do this with a crossover network. For a crossover network to work, it depends on the ratio of impedance of various coils and capacitors that have been added to the circuit and the impedance of the speaker itself. We try to set crossover frequencies or location at very specific precisely chosen frequencies. If the impedance of the speaker changes, as we see that it surely does, so does that crossover point. So, within our ability to control it, we want the speaker's impedance to be as stable as possible to keep the crossover points from shifting all over the place.

But why are we concerned about how low the impedance goes. Most amps, and virtually all consumer amps, can only handle total per channel loads or impedance in the range of 4 ohms to 16 ohms. Below 4 ohms the demand for current becomes too high, and the power amps and the power supply simply can't handle it. They will overheat and shut down, if you are lucky. If you are not so lucky, you will damage the amp.

If impedances goes above 16 ohms, the amp becomes unstable and begins to self-oscillate. Self-oscillation is like feedback in a PA system, it is a loud high-pitched uncontrollable squeal.

Now some commercial amps for big public address systems, are capable of handling fractional ohm impedances. In other word, you could put a combination of speakers on them that totaled 0.5 ohms and they would take it. Though 1 or 2 ohms is a little more common. There are even a few consumer amps that are 2 ohm stable.

Also, keep in mind that the people who make amps understand the people who make speakers, and they understand speaker. They know that impedances are not fixed, and that is built-in to the design of an amp. Amps can handle speakers with nominal impedances in the range of 4 ohms to 16 ohms, because the designers understand what 'nominal' means and allow for it in their designs.

Now you do get a few tricky speakers, that would be called 'hard to drive'. While they may still qualify for a nominal 8 ohm rating, there impedance at certain specific frequencies can drop pretty low. I saw on 8 ohm rated speaker that had a side note saying the impedance could actually drop down to 5 ohms. Other manufacturers will rate their speakers are a most unhelpful 4 to 8 ohms. You are OK with a speakers like this as long as you only put ONE speaker on each amp channel. The load would probably be too much if you tried two of the speakers on one channel.

Hopefully that wasn't too confusing, and hopefully someone can get something out of my rambling.

Steve/bluewizard

[ChrisAV]

Originally Posted by BlueWizard

Now you do get a few tricky speakers, that would be called 'hard to drive'. While they may still qualify for a nominal 8 ohm rating, there impedance at certain specific frequencies can drop pretty low. I saw on 8 ohm rated speaker that had a side note saying the impedance could actually drop down to 5 ohms. Other manufacturers will rate their speakers are a most unhelpful 4 to 8 ohms. You are OK with a speakers like this as long as you only put ONE speaker on each amp channel. The load would probably be too much if you tried two of the speakers on one channel.

Hi Steve - how does this relate to attaching a subwoofer via the high level filter to the main speaker terminals - I assume its safe but is there anything to watch out for?

Hopefully that wasn't too confusing, and hopefully someone can get something out of my rambling.

Er, yes...but I'll keep reading til it makes sense!

Steve/bluewizard

Cheers

Chris

[BlueWizard]

Chris,

Regarding the Subwoofer. Let me make sure I understand what you are asking.

You connect the Subwoofer to the amp - This doesn't matter because the Sub has its own amp and the input impedance of the amp is likely 10,000 ohms, so it really has not effect on the amp.

Then, you use the Subwoofer amp to filter out low frequencies, and feed the remaining frequencies to the front speakers. The input to the front speakers passes through the Sub?

Is this the setup I understand you to be describing? The frequencies to the front speakers are limited by the Sub?

Or, are you saying rather than connect the Sub output of the amp to the Sub input, you connect the speaker output of the amp to the Sub????

If the second option, then because the speaker outputs have speakers on them, that sets the perceived inpedance. The additional 10,000 ohms of the amp mean very little in parallel to the speakers.

What happens in the High Level Inputs, that is different than the standard RCA Low Level Inputs, is that there is some mechanism inside the amp to drop the very high level speaker signal down to a very low level signal that the Sub amp can process. Most likely the first stage of this is simply a resistive voltage divider.

In the Voltage divider, a large resistor is in series with the speaker input, then there is a very small resistor to ground which feeds the pre-amp stages. The large resistor 'eats' the bulk of the voltage, leaving only a small amount across the small resistor to feed the amp's pre-amp stages.

Though fairly, you can't count totally on the voltage divider since Resistor tend to be noisy. I know that sounds ridiculous when you consider there are resistors all over the place in an amp, but when you are dividing the voltage down this far, resistor noise does come into play. Likely, the incoming voltage is divided down in stages to keep noise to a minimum.

So, the input impedance of the Sub amp is so large as to be insignificant compared to the impedance of the front speakers themselves.

Does that answer your question?

Steve/bluewizard

[ChrisAV]

Hi Steve


To clarify (in this instance using a BK Gemini as an example), I mean by using a 3 way Nuetick cable which at one end connects to both red main front speaker terminals and a third to either of the corresponding black terminals. The other end terminating at the amp with a special high level plug.

Link to manual in case still not clear : 'method 1 connecting using the high level input' on page 3 of BK Gemini manual http://www.bkelec.com/HiFi/Sub_Woofe...i%20manual.pdf.

The idea is that when using the amp in Pure Direct mode all AV processing is bypassed and only stereo is passed to the front main speakers. Attaching the sub in this manner allows the sub to be used to complement the main speakers by setting the appropriate crossover point (in my case around 50Hz which is as far down as my 9.1's will go).

I think however you have answered my question anyway, attaching a sub isn't the same as adding a normal speaker because (if I understand correctly) you're actually connecting to another amp rather than driving the speaker directly.

Cheers

Chris

[Jeroen1000]

Thanks Steve, your reply was very helpful! The effort you put into each reply is very admirable. I've printed it out to get a better understanding of things.

Originally Posted by BlueWizard

are the peak power, dynamic power, RMS power, we don't know.

Sorry for deleting some sections of your reply, but I wan't to avoid all too large quotes for the sake of clarity.

In this setup the sub overpowers the little pod speakers so I'm feeling it's a bit too powerful for my small room. To answer your question, we are in fact dealing with RMS power. 2 * 62W for the fronts, 69W for the center and 2 * 62W for the rears. The sub is 188W.

Originally Posted by BlueWizard

Now to the frequency response, 35hz to 20khz would be quite good for a single bookshelf or floorstanding speaker, and exceptionally good for an 'egg/pod' speaker. But, you are not seeing the response of the main speakers, you are seeing the response of the entire system.

Yes, the Sub many go down to 35hz, which is only so-so for a sub, but it is very unlikely that the satellite speakers are even close to that. So, again, that is not the response of one speaker, it is the entire system.

You make a good point that I missed. I thought 35hz was for the sub and 20khz for all the others. Why is it only so-so as I'm older than 20 so I won't be able to hear below 35hz anyway? Why would the satellite speakers have to go this low? I thought it was the sub's job to handle the lows up to a certain frequency? What I mean is, I assumed the sub will handle 35hz to ... (k)hz (some number here) and the satellites pick up where the sub left of from ... (k)hz (some number here) to 20khz. Are you saying each separate speaker should be able to cover the entire frequency range?

Originally Posted by BlueWizard

I suspect I sound very negative, but budget and personal requirements drive everything.

Anything you can use in there???

Not negative but fair. I once bought them because they were exceptionally good for computer speakers and good enough for modest surround. I spent most of my cash on the video part. I'm hoping to calibrate the TV after some time. The result of all this, is that I've become fairly knowledgeable in the video department but am seriously lacking the basics about audio.


On Impedance -

Phil T is right, impedance is not fixed for speakers, even though speakers seem to have a fixed impedance rating. So, a speaker that is nominally 8 ohms is more or less sort of 8 ohms.

If you look at this PDF file for a Dayton 8" Classic woofer, over on the bottom right, you will see the impedance graph.

http://www.parts-express.com/pdf/295-310s.pdf

Originally Posted by BlueWizard

You don't really have to understand this part, its just for background.

I sort of get it. The amount of power an amp will need to supply depends on the frequency (which has an influence on the impedance), or better put on how much current and voltage are out of phase. Or perhaps you are indicating how much watts will come out of a given speaker? I looked into this briefly when deciding which PSU to buy for my computer. A switching PSU tries to rectify this (well the better one's will, but nowadays most of them will probably do this). I will still have to look up what exactly resonance is, but I'm not lazy and I'm going to.

I pretty much understand the rest you said (after reading it 5 times, I admit). I really appreciate the details of the story!