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post #1 of 33 Old 08-10-2014, 06:43 PM - Thread Starter
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Brightness vs volume level

Why do high frequency sounds start sounding harsh well before it seems like a receiver would be clipping? Is this due to human hearing response? Something that you notice more when you get older?

I have seen equal loudness contours and I can see that HF levels in the contour don't change much with volume, so it does't seem right it's as simple as response changes as overall SPL increases.

Curious about it.

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post #2 of 33 Old 08-10-2014, 07:15 PM
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This is just a theory of mine, but I believe you are hearing the receiver start to run out of gas. The bass frequencies can't get any louder, but the mid and higher frequencies can, and as the volume continues to go up past the amps ability to amplify the bass, the mids and high frequencies can still get louder.

I think this is a contributing factor to blown tweeters and not really clipping in and of itself, as the normal power ratio between the woofer and tweeters when played under ideal conditions changes and the ratio difference starts becoming less so instead of say 10:1, maybe it's 5:1, with more power than normal towards the higher frequencies. A typical loudspeaker rated at 100 watts may have a woofer that can handle it, but the tweeter may only be able to take 10 watts, and usually with music played within the amps capability the tweeter would never receive more than 10 or so watts with a 100 watt amp, but if the ratio changes the tweeter may be seeing peaks of 15, 20, maybe even 30 watts. So not only can that clearly damage a speaker, but the tonal balance shifts towards more higher frequencies than is normally present.

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post #3 of 33 Old 08-10-2014, 08:42 PM
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Quote:
Originally Posted by MichaelJHuman View Post
Why do high frequency sounds start sounding harsh well before it seems like a receiver would be clipping?
It may be clipping. One of the symptoms is that the high frequency harmonic content increases, causing the sound to at first seem brighter, progressing to harsh as THD rises. Equal loudness does enter the equation as well, although to a far lesser degree than with low frequencies.

The bass frequencies can't get any louder, but the mid and higher frequencies can, and as the volume continues to go up past the amps ability to amplify the bass, the mids and high frequencies can still get louder.

That's pretty much the textbook definition of clipping.

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post #4 of 33 Old 08-10-2014, 09:37 PM
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Since I like it loud and the human ear is most sensitive to HF, I actually apply a dynamic compressor once the tweeter exceeds a few watts, this allows the bass to level up to the ear's HF sensitivity at loud SPL; and below that it deactivates back to its normal flat-response. Also the human ear is insensitive to bass so I apply a dynamic expander at low SPL and it deactivates to a normal flat-response at higher SPL.

The combination of the two seems to solve the problem.

But also my speakers are 100db/watt and my tweeters are rated for 120watts and I have them on 1200watts a piece (yes, just the tweeter), with active XO's and triple quad monoblocks for the LCR.
My tweeters never sound harsh unless the track demands it to be so or until the volume is at gross levels (like above reference, or much more beyond). That is true even without the dynamic DSP stuff enabled.

In your case it could very well be that your amp is not able to supply enough power, and/or, the speaker not being able to handle the power it is already getting.

So it's probably a combination of the three.

Sounds like you need a high efficiency 3-way speaker like mine, powered by a good amount of watts, like say an class-H EP4000 or Emotiva XPA-2; and also double the amount of subwoofer wouldn't hurt none.
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post #5 of 33 Old 08-10-2014, 09:52 PM
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In the simplest example, you can see that clipping of a single frequency creates harmonics which are multiples of the original frequency.

If the original frequency is a power hungry bass tone and drives the amp into clipping the higher harmonics may well be above the crossover frequency and pass to tweeter and be heard as harshness.


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post #6 of 33 Old 08-10-2014, 10:19 PM - Thread Starter
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Thing, is, I would say SPL levels were such that the amount of average power would seem to have been in low wattage range. Admittedly peak power needs could have been ten times that or more.

"But this one goes up to 11"
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post #7 of 33 Old 08-10-2014, 10:20 PM
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Quote:
Originally Posted by MichaelJHuman View Post
Why do high frequency sounds start sounding harsh well before it seems like a receiver would be clipping?
Superposition.

The final full band signal recorded is the sum of all the components. Because music is very complex, I'll use Rod Elliotts graphics to explain.
If you had a 100Hz sine wave and a 1kHz sine wave they would add to form the third waveform.



Now when the combined signal exceeds a voltage rail, and clips, it is the smaller (generally) HF that gets clipped first as per graphic:



If the distortion products created are in the 1-6kHz range where our hearing is more sensitive, they will be more audible still.
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post #8 of 33 Old 08-11-2014, 03:40 AM
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Quote:
Originally Posted by MichaelJHuman View Post
Why do high frequency sounds start sounding harsh well before it seems like a receiver would be clipping? Is this due to human hearing response? Something that you notice more when you get older?

I have seen equal loudness contours and I can see that HF levels in the contour don't change much with volume, so it does't seem right it's as simple as response changes as overall SPL increases.
I find this question to be unanswerable because the conditions of the listening experience are so ambiguous.

If perhaps you had a SPL meter and used it to monitor levels while you were experiencing this, an answer could be found:

Here's a good one for about $30:

http://www.ebay.com/itm/30-130dB-USB...-/251425940110

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post #9 of 33 Old 08-11-2014, 03:52 AM
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Quote:
Originally Posted by mtn-tech View Post
In the simplest example, you can see that clipping of a single frequency creates harmonics which are multiples of the original frequency.

If the original frequency is a power hungry bass tone and drives the amp into clipping the higher harmonics may well be above the crossover frequency and pass to tweeter and be heard as harshness.


This can go either way.

Here is the spectral content of clipped and unclipped versions of a recording that has a lot of high frequency content:



The green lines are before clipping, and the red lines are after clipping the peaks by 12 dB.

A number of changes have taken place:

(1) The average power has increased.

(2) The energy in the range from 5 KHz to about 12 KHz has decreased.

(3) The energy in the range above about 22 KHz has increased.

Subjectively it is duller sounding, but technically the increase in energy above 22 KHz has made it more likely to kill tweeters.

The overall increase in energy with the same peak level means that an amplifier with a given power rating will be more likely to damage speakers even though its power rating is unchanged.

I've also done this experiment with 20 dB of clipping and the highs are generally reduced.
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post #10 of 33 Old 08-11-2014, 10:27 AM
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Originally Posted by BassThatHz View Post
the human ear is most sensitive to HF,
No, it's the mid frequency range.
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post #11 of 33 Old 08-11-2014, 11:46 AM
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Quote:
Originally Posted by A9X-308 View Post


If the distortion products created are in the 1-6kHz range where our hearing is more sensitive, they will be more audible still.
This is why bi-amping with digital XO's is more optimal at high SPL, even if you have cascaded analog passive XO's, you will still have double the available headroom to avoid amp clipping.
With two cheap DSP amps like the inukes it isn't as expensive as it used to be.

Of course this only works if you have a speaker that has two unlinked binding posts, or one for each driver.

Since tweeters are almost always the first thing to blow, it is all the more important to give it every clean watt it is rated for. The pictures above are a pretty good visual of what happens when you don't.

Speakers that measure flat at all SPL's and frequencies might look scientifically-superb in a whitepaper or spec sheet, but in the real world with thermal compression and power compression & clipping, and human ear sensitivity/insensitivity, it makes our audio hobby that much more difficult, and less superb sounding.

Below about 90db you need massive bass boost or treble cut to make it sound "smooth", and it needs to stop boosting or cutting above 90db as things level off and before you approach the threshold of discomfort.

If you listen at 50db, you will need 30db of bass boost so that it doesn't sound "anaemic".
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post #12 of 33 Old 08-11-2014, 12:48 PM
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While the above responses may very well be the answer, another answer is you may be experiencing comb filtering in the frequencies in question causing them to sound harsh. Comb filtering is caused by high gain early reflections (typically) recombining with the direct signal.

Just another possibility.

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post #13 of 33 Old 08-11-2014, 05:07 PM
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Quote:
Originally Posted by BassThatHz View Post
T


Of course this only works if you have a speaker that has two unlinked binding posts, or one for each driver.
Nonsense. No home speakers have their binding posts disconnected from the relevant crossover section. Of course pro pa stuff may indeed give you direct access to the drivers, but most folks on this board aren't running real PA speakers because those speakers ate optimized to sound best about 50 feet behind a normal listening position in a real house.

The tweeter is connected to the high pass side of the crossover. The woofer (in a two way) is connected to the low pass side of the crossover. Using outboard crosdovers simply stacks the two rolloffs unless you physically bypass the crossover components in the speaker. Go nuts. Bye bye warranty when you rip the ctosdover outta your BWs.
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post #14 of 33 Old 08-11-2014, 05:42 PM
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Sorry to have to be rude, but spreading bad information is worse.

Quote:
Originally Posted by BassThatHz View Post
I actually apply a dynamic compressor once the tweeter exceeds a few watts, this allows the bass to level up to the ear's HF sensitivity at loud SPL; and below that it deactivates back to its normal flat-response. Also the human ear is insensitive to bass so I apply a dynamic expander at low SPL and it deactivates to a normal flat-response at higher SPL.
Really? You manipulate the artistic intent of the sound and call it good? That's actually what I call distortion.

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Originally Posted by BassThatHz View Post

But also my speakers are 100db/watt
No they're not.

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Originally Posted by BassThatHz View Post
This is why bi-amping with digital XO's is more optimal at high SPL, even if you have cascaded analog passive XO's, you will still have double the available headroom to avoid amp clipping.
Could you please tell us mere mortals what a cascaded analog passive XO is? Sound really cool Perhaps you could explain what just a regular passive XO is?

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Originally Posted by BassThatHz View Post
With two cheap DSP amps like the inukes it isn't as expensive as it used to be.
This is true. But how many people on AVSforum know how to measure drivers, CAD the appropriate slopes, consider the acoustic design requirements of the drivers and configuration, and test the final implementation? General, that's not useful advice to most people here. And the people who do know how to do that already do if they find active filtering to be suitable for their application.

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Originally Posted by BassThatHz View Post

Of course this only works if you have a speaker that has two unlinked binding posts, or one for each driver.
Like the above poster said, what kind of speaker has this option available. And like I said, how is it useful to 99.9% of avsforum members. Hint, just plugging in LR4 at 2khz is not an active XO. At all.

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Originally Posted by BassThatHz View Post
Speakers that measure flat at all SPL's and frequencies might look scientifically-superb in a whitepaper or spec sheet, but in the real world with thermal compression and power compression & clipping, and human ear sensitivity/insensitivity, it makes our audio hobby that much more difficult, and less superb sounding.
Flat anechoic frequency response looks scientifically superb because it is the scientifically documented method of speaker design. There's nothing wrong with that. The human ear's sensitivity curves are completely irrelevant to speaker design. They're only relavent to the music artist and/or sound designer. It's not up to you to decide when an electric guitar should be louder or quiter. That's what heavy and light strums on the strings are for. Compression is just a weakness of speakers that need to be considered when applying them to a given purpose.

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Originally Posted by BassThatHz View Post

Below about 90db you need massive bass boost or treble cut to make it sound "smooth", and it needs to stop boosting or cutting above 90db as things level off and before you approach the threshold of discomfort.

If you listen at 50db, you will need 30db of bass boost so that it doesn't sound "anaemic".
90db what? Average? Peaks? Where does your information come from? You need 30db of bass boost for listening below 50db??? 50db is near most people noise floor. Do you know what 50db of average sound with 80db bass would sound like? It would sound like subs playing with the mains turned off. You have strange tastes.
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post #15 of 33 Old 08-11-2014, 05:49 PM
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To the OP. I think harsh tweeter sounds at higher volumes is a matter of clipping, listening fatigue, and room related reflections. These are all difficult for the average person to quantify or even identify. Like Arny said, the question is difficult to answer because the details are fuzzy.

If you like to listen to high volumes, a downward tilt in your listening position frequency response can be a more enjoyable sound. If you don't have a mic, see if you can eq in your receiver. Just winding it, I'd suggest even something as slight as a slope about -1 to -3db from 2 to 10khz. IME, 1db at 2khz is audible when pushing things. It will not be a dramatic change though, so don't expect one.
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post #16 of 33 Old 08-12-2014, 09:52 PM
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My experience is that it's often the result of dome tweeters being pushed too hard. Not clipping from the amp, just distortion in the driver. I find domes very hard to listen to at anything above moderate volume.

Cheers,
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post #17 of 33 Old 08-12-2014, 11:30 PM
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Quote:
Originally Posted by Peter M View Post
My experience is that it's often the result of dome tweeters being pushed too hard. Not clipping from the amp, just distortion in the driver. I find domes very hard to listen to at anything above moderate volume.

Cheers,
Surely not all soft domes are created equal. Some may exhibit what you describe, but I doubt it is inherent in all domes as a general statement. I've never noticed it with any half way decent tweeters.

What would you say doesn't, ribbons, compression drivers?
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post #18 of 33 Old 08-13-2014, 01:06 AM
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Originally Posted by JHAz View Post
Nonsense. No home speakers have their binding posts disconnected from the relevant crossover section. Of course pro pa stuff may indeed give you direct access to the drivers, but most folks on this board aren't running real PA speakers because those speakers ate optimized to sound best about 50 feet behind a normal listening position in a real house.

The tweeter is connected to the high pass side of the crossover. The woofer (in a two way) is connected to the low pass side of the crossover. Using outboard crosdovers simply stacks the two rolloffs unless you physically bypass the crossover components in the speaker. Go nuts. Bye bye warranty when you rip the ctosdover outta your BWs.
Unh, whaddaminute there, chief.

If you bi-amp using two amps, with reasonably sharp crossover set far away from the actual speaker crossover (i.e. higher for the bass side, lower for the HF side), you can in fact get a lot of clipping protection on the high side, and not mess up your crossover much, if any. You do have t be careful to get it right.

In any case, you won't splatter crap into the HF side unless you clip the HF side, under such circumstances.

Now, to the OP, there re too many variables left out to make an informed guess as to what's wrong, I must say. Need more information like:

Amp power
Amp current rating
Speaker power rating
Speaker impedence curve

Just those 4 could lead to a whole ocean of stuff. That's without assuming anything is broken.

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post #19 of 33 Old 08-13-2014, 01:37 AM
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Originally Posted by jj_0001 View Post
Unh, whaddaminute there, chief.

If you bi-amp using two amps, with reasonably sharp crossover set far away from the actual speaker crossover (i.e. higher for the bass side, lower for the HF side), you can in fact get a lot of clipping protection on the high side, and not mess up your crossover much, if any. You do have t be careful to get it right.

In any case, you won't splatter crap into the HF side unless you clip the HF side, under such circumstances.

Now, to the OP, there re too many variables left out to make an informed guess as to what's wrong, I must say. Need more information like:

Amp power
Amp current rating
Speaker power rating
Speaker impedence curve

Just those 4 could lead to a whole ocean of stuff. That's without assuming anything is broken.
What the... That doesn't sound like a good idea at all. Using a steep sloped active crossover at different values than the passive crossover? That will alter the original crossover points for starters, and who knows what else to the overall tonal balance of the speaker. I cannot recommend this strange technique...especially the idea of using an active crossover value lower than the passive crossover, if I could even recommend any of it, which I can't.

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post #20 of 33 Old 08-13-2014, 02:34 AM
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Quote:
Originally Posted by 89grand View Post
What the... That doesn't sound like a good idea at all. Using a steep sloped active crossover at different values than the passive crossover? That will alter the original crossover points for starters, and who knows what else to the overall tonal balance of the speaker. I cannot recommend this strange technique...especially the idea of using an active crossover value lower than the passive crossover, if I could even recommend any of it, which I can't.

Obviously you don't even understand what I said, I said use s steep active crossover set ABOVE the crossover point for the woofer, and BELOW the crossover point for the HP driver. In other words, provide both sides of the passive crossover with full signal in their transition range.

It won't affect the crossover frequency then, unless you blow it by getting too close to the passive crossover frequency.

This will keep any clipping on the bass side out of the HF side. That's what somebody was suggesting.

I would suggest that in the future you do one of the following:

1) Learn filter theory
or
2) Read what the other person said BEFORE you go off like that.

Note: In any system set up and designed properly, this should not be necessary. That's a different issue.

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post #21 of 33 Old 08-13-2014, 02:46 AM
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Note, I am also assuming that one is doing this digitally, because that way, one can equalize the linear-phase portion of the group delay of, say, a 5th order butterworth, so as to not mess up the phase of the passive crossover. Even without that, there's precious little problem as long as you stay at least 2 octaves out on either side.

With FIR filters, this is triviality itself, of course, and there will be no consequences except that both amplifiers will experience less load than otherwise.

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post #22 of 33 Old 08-13-2014, 02:54 AM
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Quote:
Originally Posted by jj_0001 View Post
Obviously you don't even understand what I said, I said use s steep active crossover set ABOVE the crossover point for the woofer, and BELOW the crossover point for the HP driver. In other words, provide both sides of the passive crossover with full signal in their transition range.

It won't affect the crossover frequency then, unless you blow it by getting too close to the passive crossover frequency.

This will keep any clipping on the bass side out of the HF side. That's what somebody was suggesting.

I would suggest that in the future you do one of the following:

1) Learn filter theory
or
2) Read what the other person said BEFORE you go off like that.

Note: In any system set up and designed properly, this should not be necessary. That's a different issue.
I don't want to be rude, but I'd prefer you don't offer me any advice again. You are clearly mistaken.

If you set the crossover BELOW the passive crossover for the tweeter, you are altering the systems original design...and not in a good way. In fact, I suggest no one take your advice and try anything even remotely similar. In addition, using active and passive crossovers together makes zero sense.

But that's just my opinion. I'll call it opinion even though it is 100% correct.
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post #23 of 33 Old 08-13-2014, 05:58 AM
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Quote:
Originally Posted by Peter M View Post
My experience is that it's often the result of dome tweeters being pushed too hard. Not clipping from the amp, just distortion in the driver. I find domes very hard to listen to at anything above moderate volume.
There are remarkably few differences between dome tweeters and midranges as compared to comparable cone based drivers other than diameter, when it comes to dynamic range and low distortion, all other things being equal.

It was interesting for me to listen to what Villchur, arguably the inventor of the first practical dome tweeters, had to say about them in this video:

http://www.aes.org/historical/oral/?ID=49

Cut to the chase, Villchur seems to see domed drivers as an evolution of cone tweeters, idealized for higher frequencies.

The dynamic range of either domes or cones is based primarily on Xmax, diaphragm size, and the thermal capacity of the voice coils. While there are large domed drivers, most of their limitations come from the small diameter of so many of them which is also usually their most valuable feature.

The big surprise is the fact that domed drivers basic technology is so robust.

At this time nearly 40 years later so-called dome tweeters are known to be quite enigmatic. The diaphragm can be convex, flat or concave; it can be made of the hardest materials known including diamond and beryllium, or it can made of almost floppy soft treated cotton or silk; it can be supported at only its edge or also in the center yielding a diaphragm that is more like a ring. No matter what, the speaker's dynamic range, frequency response and directivity are almost entirely dictated by the diameter and robustness of its voice coil.

The comparison to horns is even closer, because a dome tweeter is just a slightly degenerate form of a compression driver lacking only the phasing plug and throat/flange for attaching the waveguide/horn. This similarity had to be accounted for in Villchur's patent applications.

The horn often has dramatic benefits in terms of the efficiency of the overall assembly, which means that the cone and diaphragm does not have to work so hard to be loud. We now have a fair number of speaker systems based on dome tweeters mounted in the throat of a shallow waveguide, primarily for directivity control. The horn itself can become a path to more nonlinear distortion if it is not large enough to support the desired low frequency extension.
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post #24 of 33 Old 08-13-2014, 06:49 AM
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Originally Posted by Peter M View Post
My experience is that it's often the result of dome tweeters being pushed too hard. Not clipping from the amp, just distortion in the driver. I find domes very hard to listen to at anything above moderate volume.
The same applies to all drivers, not just domes but all tweeters, not just tweeters but midranges, woofers and even subs. At some point the driver runs out of xmax at the lower end of its passband, so more power applied does not give more output. But as xmax has not been reached at higher frequencies more power applied does result in higher output there, resulting in a higher degree of harmonic content than the original signal. In effect the driver will clip the signal, just like electronics do. The most common example of this is electric guitar drivers, woofers intentionally made with a very short xmax so that they will give very high THD. The average 12 inch sub driver has about 14mm xmax, the average 12 inch woofer 8mm xmax. The average 12 inch guitar driver has 1mm xmax, so that it will start clipping the signal at 10 watts or less. Put 50 watts into that driver and the THD is so severe that the resulting tone bears no resemblance at all to an acoustic guitar, and that's the point.
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post #25 of 33 Old 08-13-2014, 07:53 AM
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Originally Posted by jj_0001 View Post
Obviously you don't even understand what I said, I said use s steep active crossover set ABOVE the crossover point for the woofer, and BELOW the crossover point for the HP driver. In other words, provide both sides of the passive crossover with full signal in their transition range.

It won't affect the crossover frequency then, unless you blow it by getting too close to the passive crossover frequency.

This will keep any clipping on the bass side out of the HF side. That's what somebody was suggesting.

I would suggest that in the future you do one of the following:

1) Learn filter theory
or
2) Read what the other person said BEFORE you go off like that.

Note: In any system set up and designed properly, this should not be necessary. That's a different issue.
but if you set your outboard low and high pass so that they don't significantly affect the speaker's FR in the crossover range, it seems to me you're not doing anything real to preserve the drivers. Conceptually, I'd want to be at least at or beyond the -10db point in the passive crossover to assure I don't cause audible changes in te\hh FR. When the passive crossover element already has power attenuated to 1/10 (-10dB), I'm not sure further attenuation is particularly relevant under normal circumstances. You'd have to be overpowering by a factor of 20 times or more for the outboard filters to do anything that needed doing, seems to me. ALthough it's an interesting idea, at least . . .
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post #26 of 33 Old 08-13-2014, 02:39 PM
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Originally Posted by 89grand View Post
If you set the crossover BELOW the passive crossover for the tweeter, you are altering the systems original design...and not in a good way.
Stuff and nonsense, you haven't altered anything at all. The passive crossover is still in circuit, just like it's always been, and so you don't have any difference to speak of going into the tweeter. This is a basic filter design issue, and a very, very obvious one.

This is an obvious fact. I have no idea why you don't see it, but since you seem immune to correction, I'll let you go on your mistaken way.

Note: Nobody here is taking the crossover OUT of the speaker, nope. Uh uh. If you are, then a completely different crossover is called for, but that's not what we're talking about.

And, I have to say, I'm not in favor of taking the tweeter crossover completely out in any case, just due to standard circuit and DC issues.

Oh, and I do this for a living, so telling the world I'm wrong, when I'm not, is an extremely serious action. I would suggest that you back off completely and apologize now.

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post #27 of 33 Old 08-13-2014, 02:42 PM
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Originally Posted by JHAz View Post
but if you set your outboard low and high pass so that they don't significantly affect the speaker's FR in the crossover range, it seems to me you're not doing anything real to preserve the drivers.
What you are doing, specifically, is to prevent clipping from the LF amp from getting into the tweeter.

As the bass (driver or amp) is not even electrically connected to the HF driver now, that's a done deal.

As I said, this should not be necessary in a standard setup, but that's been an issue more than once.

Also, given some really strange crossover designs that have really wacky impedence curves around the crossover point, you may lighten the load on the amps, or maybe not, depending on the crossover.

I've seen some strange stuff, especially in the phase of the impedance, in some speakers.

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post #28 of 33 Old 08-13-2014, 08:09 PM
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Originally Posted by 89grand View Post
Surely not all soft domes are created equal. Some may exhibit what you describe, but I doubt it is inherent in all domes as a general statement. I've never noticed it with any half way decent tweeters.

What would you say doesn't, ribbons, compression drivers?
When I said "domes" I didn't mean to differentiate them from "cones". It's just how I tend to describe tweeters, as these days they nearly all seem to be domes.

I have listened to many very expensive speakers and tweeter distortion at high volume in large spaces has been present in all of them.

Horns and compression drivers are generally superior in my experience. I can't comment on ribbons as I haven't spent enough time with them.

Quote:
Originally Posted by arnyk View Post
There are remarkably few differences between dome tweeters and midranges as compared to comparable cone based drivers other than diameter, when it comes to dynamic range and low distortion, all other things being equal.

It was interesting for me to listen to what Villchur, arguably the inventor of the first practical dome tweeters, had to say about them in this video:

http://www.aes.org/historical/oral/?ID=49

Cut to the chase, Villchur seems to see domed drivers as an evolution of cone tweeters, idealized for higher frequencies.

The dynamic range of either domes or cones is based primarily on Xmax, diaphragm size, and the thermal capacity of the voice coils. While there are large domed drivers, most of their limitations come from the small diameter of so many of them which is also usually their most valuable feature.

The big surprise is the fact that domed drivers basic technology is so robust.

At this time nearly 40 years later so-called dome tweeters are known to be quite enigmatic. The diaphragm can be convex, flat or concave; it can be made of the hardest materials known including diamond and beryllium, or it can made of almost floppy soft treated cotton or silk; it can be supported at only its edge or also in the center yielding a diaphragm that is more like a ring. No matter what, the speaker's dynamic range, frequency response and directivity are almost entirely dictated by the diameter and robustness of its voice coil.

The comparison to horns is even closer, because a dome tweeter is just a slightly degenerate form of a compression driver lacking only the phasing plug and throat/flange for attaching the waveguide/horn. This similarity had to be accounted for in Villchur's patent applications.

The horn often has dramatic benefits in terms of the efficiency of the overall assembly, which means that the cone and diaphragm does not have to work so hard to be loud. We now have a fair number of speaker systems based on dome tweeters mounted in the throat of a shallow waveguide, primarily for directivity control. The horn itself can become a path to more nonlinear distortion if it is not large enough to support the desired low frequency extension.
As I said above, I wasn't meaning to single out "domes".

Quote:
Originally Posted by Bill Fitzmaurice View Post
The same applies to all drivers, not just domes but all tweeters, not just tweeters but midranges, woofers and even subs. At some point the driver runs out of xmax at the lower end of its passband, so more power applied does not give more output. But as xmax has not been reached at higher frequencies more power applied does result in higher output there, resulting in a higher degree of harmonic content than the original signal. In effect the driver will clip the signal, just like electronics do. The most common example of this is electric guitar drivers, woofers intentionally made with a very short xmax so that they will give very high THD. The average 12 inch sub driver has about 14mm xmax, the average 12 inch woofer 8mm xmax. The average 12 inch guitar driver has 1mm xmax, so that it will start clipping the signal at 10 watts or less. Put 50 watts into that driver and the THD is so severe that the resulting tone bears no resemblance at all to an acoustic guitar, and that's the point.
No argument on this. I was trying to compare "normal" tweeters to horns / compression drivers.

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post #29 of 33 Old 08-13-2014, 08:31 PM
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Originally Posted by Peter M View Post
No argument on this. I was trying to compare "normal" tweeters to horns / compression drivers.
Horns tend to be able to go louder with lower THD because they have much higher sensitivity, so they require far less diaphragm excursion to reach much higher levels. That applies to all horns, be they tweeters, midranges, woofers or subs. If you want to go loud and clean horns are the way to do it.

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post #30 of 33 Old 08-13-2014, 10:02 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Horns tend to be able to go louder with lower THD because they have much higher sensitivity, so they require far less diaphragm excursion to reach much higher levels. That applies to all horns, be they tweeters, midranges, woofers or subs. If you want to go loud and clean horns are the way to do it.
Yeah, very true, as long as you don't get to too high SPL's at the maximum point in the horn. When you start to hit 120dB SPL air starts to get nonlinear, after all, and at 140dB SPL it's rather nonlinear, so you want to keep the horn throat below those levels if you want "clean".

Within those issues, though, horns are the way to get very high SPL. Usually, (but not always, of course) there will be more frequency response peakiness with a horn due to the various acoustic impedance-matching issues.

Still for high SPL's at midrange, horns are more or less your only choice, really, unless you want the Grateful Dead setup, which has its own problems.

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