"BL^2/RE": how is this the 'force factor" in a driver? - Page 5 - AVS Forum
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post #121 of 144 Old 11-13-2013, 12:40 AM
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Originally Posted by noah katz View Post

A sealed speaker system with Q=.7 rings, as shown by programs like UniBox that plot impulse response.

Since it's already flat, no EQ is required, so it would seem that your example from Linkwitz (very interesting, thanks) does not apply.

I can see only step response in Unibox, but it doesn't matter here.

The problem is that every high-pass or low-pass-filter changes phase. Q only describes the shape of amplitude and phase change. But even a Q of 0.1 changes the phase and in conclusion it changes the shape of impulse and step response. If you want a impulse/step response without ringing you have to equalize to DC. And if it shall be ideally short in time you have to equalize to infinite Hz. But since the shape of impulse responses does not correlate to what we hear this is not a very reasonable goal.

Another way is to use FIR filters which can equalize phase and amplitude separately. But the lower the phase gets linearized the higher will be the inherent filter delay. For equalization to 3 Hz this may be not a good choice. I don't think anyone wants to hear the bass attack 0.5 s after explosion on the screen. wink.gif

From my point of view the whole Q thing is a relict of the last century. Only Qtotal (signal chain + subwoofer + room) is important. Nowadays analog or digial equalizers can change Q on the fly. I would not depend on Qtc when designing a subwoofer. A better way is to optimize maximum SPL for all frequencies by selecting a smaller Vb in that way that driver's mechanical and electrical limits are coincident. Then measure in-room frequency response and put a linkwitz transform on top of this.

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Originally Posted by bossobass 
BTW, I read FoLLgoTT's thread with interest and learned new stuff in the process. He's an asset to the forum and his exercises and results are not only well done, they're required reading for anyone interested in this hobby, IMO.

Thank you. smile.gif

I read many of your postings and I learned much from you. I never had the idea to play single digit frequencies. But now I want to try this out!
Today I'll buy MDF to build my new subwoofer wall. I already have two circuit boards for linkwitz transform, but I cannot buy the capacitors until I measured in-room frequency response. When all that is finished I will post measurements. smile.gif
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post #122 of 144 Old 11-13-2013, 09:34 AM
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Originally Posted by LTD02 View Post

"If as Josh and others have said, and I agree wholeheartedly, a system can be built with drivers that have enough Bl^2/Re to result in a flat response in a given room at the desired playback level, what's the question?"

that's kind of a funny way to put it because josh has eight 18" drivers and arc welding capable amplifier firepower behind them, so in some sense he has got (BL^2*8)/re. :-) the point about looking at the whole system is right on as doubling drivers (or doubling, doubling, doubling drivers) will amp up 1w/driver sensitivity by 6db per doubling. so long as you can hit your target, whatever it may be, all is good and that is as I've stated is probably the most significant point folks are trying to get at when looking at motor strength. all this other stuff about group delay at 3 hz or infinitely low q is interesting, but has no practical application.

First, 8X18" is a waste of resources unless the 18s used are the type you prefer, in which case he needs 16 of them. That's kinda what I've been saying for 11 years. wink.gif
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all this other stuff about group delay at 3 hz or infinitely low q is interesting, but has no practical application.

How would you know? tongue.gif

The point is to explore. In this discussion of what the practical app is, the initial goal is to move distortions caused by FR amplitude non-linearity down in frequency until there is no audible distortion.

To do that, you build a system with signal integrity (least roll off) and signal shaping to perfectly mate the specific room gain profile with the anechoic response of the system.

This is not a difficult task.
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post #123 of 144 Old 11-13-2013, 09:36 AM
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Originally Posted by FoLLgoTT View Post


From my point of view the whole Q thing is a relict of the last century. Only Qtotal (signal chain + subwoofer + room) is important. Nowadays analog or digial equalizers can change Q on the fly. I would not depend on Qtc when designing a subwoofer. A better way is to optimize maximum SPL for all frequencies by selecting a smaller Vb in that way that driver's mechanical and electrical limits are coincident. Then measure in-room frequency response and put a linkwitz transform on top of this.

There it is in one neat little paragraph.
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post #124 of 144 Old 11-13-2013, 09:38 AM
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Originally Posted by FoLLgoTT View Post

If you want a impulse/step response without ringing you have to equalize to DC.

OK then.

So is it correct to conclude that different subwoofers EQ'd to the same freq resp but with different Fb's have different impulse and perhaps sonic signatures?

Noah
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post #125 of 144 Old 11-13-2013, 10:33 AM
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Originally Posted by noah katz View Post

So is it correct to conclude that different subwoofers EQ'd to the same freq resp but with different Fb's have different impulse and perhaps sonic signatures?

When they have different fb and the equalization does not change the cut-off frequency then their frequency responses are not the same. And of course their impulse/step response etc. are not the same either.

Only when the frequency responses are completely equalized the transient behaviour is the same. This means that when you overlay both frequency responses you have to see only one single graph. They must be congruent.

All this counts only for minimum phase systems (common sealed and bassreflex subwoofers). For example a commercial subwoofer with activated phase control does NOT count to this group. The phase control is usually implemented by a variable all-pass filter. An all-pass filter changes only the phase leaving amplitude untouched. This converts a minimum phase system to a non-minimum phase one. The same thing counts for multiple ways (low, mid, high). Each way alone stays minimum phase, but the sum doesn't.
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post #126 of 144 Old 11-13-2013, 10:51 AM
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Originally Posted by FoLLgoTT View Post

When they have different fb and the equalization does not change the cut-off frequency then their frequency responses are not the same. And of course their impulse/step response etc. are not the same either.

As I said in an earlier post, they would be EQ'ed for the same response, to an F3 to well below the range of Fb.

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post #127 of 144 Old 11-13-2013, 10:54 AM
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Originally Posted by noah katz View Post

As I said in an earlier post, they would be EQ'ed for the same response, to an F3 to well below the range of Fb.

In this case their transient response is the same, too.
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post #128 of 144 Old 11-13-2013, 04:29 PM
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Originally Posted by FoLLgoTT View Post

In this case their transient response is the same, too.

OK, I belatedly read the link to the Linkwitz example and the key is "This signal will force upon the driver a response correction so that it is no longer dominated by Fp = 55 Hz and Qp = 1.21."

Pretty slick; does this work for a vented system with a suitable filter?

Noah
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post #129 of 144 Old 11-13-2013, 06:15 PM
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LTs are pretty much only useful for sealed systems. No reason you couldn't do it to a vented system that has a sloping response, but somewhat impractical.
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post #130 of 144 Old 11-13-2013, 08:12 PM
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Quote:
Originally Posted by noah katz View Post

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Originally Posted by FoLLgoTT View Post

In this case their transient response is the same, too.

OK, I belatedly read the link to the Linkwitz example and the key is "This signal will force upon the driver a response correction so that it is no longer dominated by Fp = 55 Hz and Qp = 1.21."

Pretty slick; does this work for a vented system with a suitable filter?
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LTs are pretty much only useful for sealed systems. No reason you couldn't do it to a vented system that has a sloping response, but somewhat impractical.

Actually it is an ideally suited filter to generate whatever target response you want from a ported box of a given tuning frequency. You can often get very close with fewer filters, but if the circuit is already available it makes for a more precise response correction.

Noah - Take note of FoLLgoTT's specifically mentioning the response must completely match. The transient response does match the corrected magnitude response, but the out of band roll offs or other behavior has to match as well. This is also why it is easy to add a high pass filter to a sealed subwoofer and match the basic transient response of a ported box.

The catch of course is that this all holds true so long as the behavior of the system remains constant / non-changing. Under some conditions the response eventually changes, and the nature of those changes are linked to Fb, Q and inductance. As such, the wildly different Fb & Qs will telegraph through the response when pushed a bit. While certainly visible in the incrementally increasing sweeps seen at Data-Bass and elsewhere, the effects seem subtle as the stimulus is a single sine wave and there is rarely enough excursion at the upper frequency ranges to show what happens with a wide bandwidth, complex signal.

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post #131 of 144 Old 11-13-2013, 08:18 PM
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In WinISD I just compared a sealed/Q=.7 system with a vented system using a low Qts driver.

I got the initial rolloffs poretty well matched, howver the vented of course steepens to 4th order.

However if for use as mains and HP'ed with L-R 4th, the net responses are very similar, and so presumably would the transient response.

Or not?

I see that Mark was typing while I was WinISD'ing...
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Noah - Take note of FoLLgoTT's specifically mentioning the response must completely match. The transient response does match the corrected magnitude response, but the out of band roll offs or other behavior has to match as well.

So if the magnitude responses of EQ'd sealed and vented are the same, under ideal conditions (no heating of VC's and parameters changing; seems like a pro audio woofer loafing along in HP'ed mains would adhere pretty closely to this)), the same freq resp = impulse response outcome applies?

Noah
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post #132 of 144 Old 11-13-2013, 09:46 PM
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"First, 8X18" is a waste of resources unless the 18s used are the type you prefer, in which case he needs 16 of them. That's kinda what I've been saying for 11 years."

...or vented enclosures or horns in which case 4 would be just fine. that's kind of what jbl has been saying that since before you were born. :-)

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post #133 of 144 Old 11-13-2013, 10:12 PM
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Originally Posted by LTD02 View Post

"First, 8X18" is a waste of resources unless the 18s used are the type you prefer, in which case he needs 16 of them. That's kinda what I've been saying for 11 years."

...or vented enclosures or horns in which case 4 would be just fine. that's kind of what jbl has been saying that since before you were born. :-)

Got a link with a date on it?
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post #134 of 144 Old 11-13-2013, 10:19 PM
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Actually it is an ideally suited filter to generate whatever target response you want from a ported box of a given tuning frequency. You can often get very close with fewer filters, but if the circuit is already available it makes for a more precise response correction.

Noah - Take note of FoLLgoTT's specifically mentioning the response must completely match. The transient response does match the corrected magnitude response, but the out of band roll offs or other behavior has to match as well. This is also why it is easy to add a high pass filter to a sealed subwoofer and match the basic transient response of a ported box.

The catch of course is that this all holds true so long as the behavior of the system remains constant / non-changing. Under some conditions the response eventually changes, and the nature of those changes are linked to Fb, Q and inductance. As such, the wildly different Fb & Qs will telegraph through the response when pushed a bit. While certainly visible in the incrementally increasing sweeps seen at Data-Bass and elsewhere, the effects seem subtle as the stimulus is a single sine wave and there is rarely enough excursion at the upper frequency ranges to show what happens with a wide bandwidth, complex signal.

You keep saying that. Be more specific. Like, what is "pushed a bit"? The SubMersive is displacement handicapped and so is designed with limiter clamps. In that case what you say is true and it's because that's the choice you made when designing the sub, but that doesn't make it a global truth.
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post #135 of 144 Old 11-13-2013, 11:16 PM
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Actually it is an ideally suited filter to generate whatever target response you want from a ported box of a given tuning frequency. You can often get very close with fewer filters, but if the circuit is already available it makes for a more precise response correction.

Noah - Take note of FoLLgoTT's specifically mentioning the response must completely match. The transient response does match the corrected magnitude response, but the out of band roll offs or other behavior has to match as well. This is also why it is easy to add a high pass filter to a sealed subwoofer and match the basic transient response of a ported box.

The catch of course is that this all holds true so long as the behavior of the system remains constant / non-changing. Under some conditions the response eventually changes, and the nature of those changes are linked to Fb, Q and inductance. As such, the wildly different Fb & Qs will telegraph through the response when pushed a bit. While certainly visible in the incrementally increasing sweeps seen at Data-Bass and elsewhere, the effects seem subtle as the stimulus is a single sine wave and there is rarely enough excursion at the upper frequency ranges to show what happens with a wide bandwidth, complex signal.

You keep saying that. Be more specific. Like, what is "pushed a bit"? The SubMersive is displacement handicapped and so is designed with limiter clamps. In that case what you say is true and it's because that's the choice you made when designing the sub, but that doesn't make it a global truth.

I say that to prompt others to take a deeper look on their own and come to their own conclusions, not proclaim some ideal solution or conclusion for them. Statements of absolutes are not my style as there are always multiple factors to consider, and most real phenomena onset gradually rather than hitting a specific point when things change dramatically. The argument of where on such curves is "good enough" or inaudible is fuzzy and open for debate and plenty of varying opinions.

Whenever response changes with level the fingerprint of the original driver is observed. While it would require a screen capture to directly post here, 2 good examples of this are found at Data-Bass by selecting the "Extended Charts" tab for the measurements of the Stereo Integrity HT18D2 and the Fi SSD 18D2. Looking at the lower "Long Term Compression (Magnitude)" graphs the Stereo Integrity is rather consistent at lower levels where the driver starts it's more obvious change in response shape around and past the nominal "110dB" curve. By comparison, the same graph of the SSD 18D2 shows more variation at low levels and start where the driver starts it's more obvious change in response shape past the nominal "105dB" and "110dB" curves.

While the SSD looks like it compresses twice as much at first glance, a check of the levels shows it was driven harder into overload. Separate from any argument of preference is the fact that the *shape* of the dynamic change is different, and they will sound different. The detail not easy to quantify from these graphs is what happens when high excursion from low frequency content is coincident with content above ~40Hz, which will make some of these problems onset much sooner, and introduce new variations which the single swept sine doesn't test.

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post #136 of 144 Old 11-14-2013, 12:17 AM
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I agree with Mark regarding parameter shift. I have several Klippel diagrams including Q(x), fs(x), Le(x) etc. All this small signal parameters change with excursion. A Qts of 0.5 can change to 0.7 when reaching Xmax. Usually the largest change is in the second half on the way to Xmax. If you want a very linear subwoofer and want to keep THD extremely low it is a good idea to use only 1/2 of Xmax. But this is not new at all.

Unfortunately I'm not allowed to post the Klippel graphs.
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post #137 of 144 Old 11-14-2013, 12:57 AM
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"A Qts of 0.5 can change to 0.7 when reaching Xmax."

or worse...as noted in post #73.

certainly one reason why lower (initial) q systems could hold together better at the limits.

btw, does anybody know how to determine the q at the tuning frequency of a ported cab? is it simply through frequency response transform again or is it a non-linear effect?

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post #138 of 144 Old 11-14-2013, 11:06 AM
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"A Qts of 0.5 can change to 0.7 when reaching Xmax."

or worse...as noted in post #73.

certainly one reason why lower (initial) q systems could hold together better at the limits.

I've wondered what you mean by "hold together better" as you've made this statement a few times now. Assuming EQ is used to correct the response to the target, we are then concerned more with change in Q and any other ramifications of that. The same % BL drop starting from a Q of 0.5 vs 1.0 is not very different when looking at the change rather than the absolute. There are other ramifications of what happen to possible excursion around Fb with high vs low Q, but the significance is related to the box/amplifier choices and mechanical limits of the driver.
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btw, does anybody know how to determine the q at the tuning frequency of a ported cab? is it simply through frequency response transform again or is it a non-linear effect?

Q and energy dissipation over time is still directly tied to frequency response for a ported box and any common electrical filters short of FIR filtering. With a great range of possibilities in a 4th order system it is less simplistic to calculate or have a Q directly equate to a filter shape/type.

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post #139 of 144 Old 11-15-2013, 07:04 AM
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Originally Posted by Mark Seaton View Post

I say that to prompt others to take a deeper look on their own and come to their own conclusions, not proclaim some ideal solution or conclusion for them. Statements of absolutes are not my style as there are always multiple factors to consider, and most real phenomena onset gradually rather than hitting a specific point when things change dramatically. The argument of where on such curves is "good enough" or inaudible is fuzzy and open for debate and plenty of varying opinions.

Whenever response changes with level the fingerprint of the original driver is observed. While it would require a screen capture to directly post here, 2 good examples of this are found at Data-Bass by selecting the "Extended Charts" tab for the measurements of the Stereo Integrity HT18D2 and the Fi SSD 18D2. Looking at the lower "Long Term Compression (Magnitude)" graphs the Stereo Integrity is rather consistent at lower levels where the driver starts it's more obvious change in response shape around and past the nominal "110dB" curve. By comparison, the same graph of the SSD 18D2 shows more variation at low levels and start where the driver starts it's more obvious change in response shape past the nominal "105dB" and "110dB" curves.

While the SSD looks like it compresses twice as much at first glance, a check of the levels shows it was driven harder into overload. Separate from any argument of preference is the fact that the *shape* of the dynamic change is different, and they will sound different. The detail not easy to quantify from these graphs is what happens when high excursion from low frequency content is coincident with content above ~40Hz, which will make some of these problems onset much sooner, and introduce new variations which the single swept sine doesn't test.

Although I get the point when citing single driver systems with no signal shaping and being fed sine sweeps outdoors and I agree that these do not properly examine the DUT with actual complex program, these are snapshots and thus misleading.

In-room is what matters and designing the system for the room is the task. Sorry, but your statements on the subject do indeed give the impression that reversion to anechoic response is a fact of life "when pushed".

notnyt's sweeps and my own show no reversion to anechoic response to desired playback under sine sweeps.



And with extremely difficult actual program played back at the desired level, again, no reversion to anechoic response:



If response changes with level, the hardware is not up to the task at hand. Continually focussing on what to expect with that failure to execute seems pointless to me. It bears mentioning as 'what not to do', but the discussion should definitely be more of 'what to do'.
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post #140 of 144 Old 11-15-2013, 11:16 AM
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While most drivers with sufficient excursion capability can be made to behave similarly with enough EQ, especially when using 16 of them, as soon as you push them a little there are differences related to what the behavior is before EQ is applied.

You can't increase Bl and hold all else the same.

How exactly do you push a 16 driver system in you home theater? I contend that it's they which will push you.

Looking back I see had missed this question. My last statement here was misunderstood and not clearly stated in that I was agreeing that when using many drivers (I said 16 to make the point), most drivers are very consistent as they rarely get past a fraction of Xmax. In the latter part I should have said "as soon as you are using fewer and need to push them a little (lets say use to 1/2 to full Xmax), differences related to the native response and Fb."

I get the sense that some of the angst was coming from thinking I was suggesting that this is an issue no matter how many drivers are used, which is not what was intended. My point was that most drivers are far from ideal and when using somewhere between 1/4-3/4 of Xmax or some level of current through the coil, behavior changes and can be audible enough to create measurable and subjective differences. An extreme example of this is comparing a compact sealed box vs. an IB when both are EQ'd to the same frequency response.


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I say that to prompt others to take a deeper look on their own and come to their own conclusions, not proclaim some ideal solution or conclusion for them. Statements of absolutes are not my style as there are always multiple factors to consider, and most real phenomena onset gradually rather than hitting a specific point when things change dramatically. The argument of where on such curves is "good enough" or inaudible is fuzzy and open for debate and plenty of varying opinions.

Whenever response changes with level the fingerprint of the original driver is observed. While it would require a screen capture to directly post here, 2 good examples of this are found at Data-Bass by selecting the "Extended Charts" tab for the measurements of the Stereo Integrity HT18D2 and the Fi SSD 18D2. Looking at the lower "Long Term Compression (Magnitude)" graphs the Stereo Integrity is rather consistent at lower levels where the driver starts it's more obvious change in response shape around and past the nominal "110dB" curve. By comparison, the same graph of the SSD 18D2 shows more variation at low levels and start where the driver starts it's more obvious change in response shape past the nominal "105dB" and "110dB" curves.

While the SSD looks like it compresses twice as much at first glance, a check of the levels shows it was driven harder into overload. Separate from any argument of preference is the fact that the *shape* of the dynamic change is different, and they will sound different. The detail not easy to quantify from these graphs is what happens when high excursion from low frequency content is coincident with content above ~40Hz, which will make some of these problems onset much sooner, and introduce new variations which the single swept sine doesn't test.

Although I get the point when citing single driver systems with no signal shaping and being fed sine sweeps outdoors and I agree that these do not properly examine the DUT with actual complex program, these are snapshots and thus misleading.

The point is that signal shaping can only be applied to one of the curves seen in those outdoor measurements. The relative changes between the curves remain.
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In-room is what matters and designing the system for the room is the task. Sorry, but your statements on the subject do indeed give the impression that reversion to anechoic response is a fact of life "when pushed".

I never said the response reverts to the anechoic response, just that the changes are related to driver non-linearities and Fb of the system.
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notnyt's sweeps and my own show no reversion to anechoic response to desired playback under sine sweeps.



And with extremely difficult actual program played back at the desired level, again, no reversion to anechoic response:

And these are way too coarse a display to see what is going on from curve to curve. A direct subtraction of the data between the curves is required to see finer details of what is or is no changing between curves. The spectrograms can be very interesting, but would tell dramatically more if they were instead difference measurements showing the deviation rather than the total result where we can only see distortion or omission in areas of limited content with a fairly coarse scale.

Thinking the response effectively reverts back to the anechoic response suggests a misunderstanding of what the anechoic measurements are really showing.

At some point in raising the level 5dB more enough times, any amp will clip. Of course with a constant Voltage input vs. frequency it clips first where the EQ's transfer function has the highest gain. The misunderstanding comes from seeing that we can keep driving the upper range in a sweep that only tests a single moving sine wave through the frequency range. In real use, it doesn't matter if 80Hz causes the clipping or 10Hz, the amp has no more to give at that point, so there is no room for the upper range to keep going further. Adding a limiter only changes how the amp sounds when it approaches clipping. Assuming it's a limiter of max Voltage and not a more complex function that is frequency dependent, at some point the level stops getting louder as the limiter engages or the amp clips. Amp clipping is a form of limiting; it just often sounds worse if you get there. Any signal input that hits the limits caps anything else coming through at the same time. There most certainly are devices with more complex limiting, but it is hard if not impossible to decipher which is being used when only looking at a set of sine sweeps.
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If response changes with level, the hardware is not up to the task at hand. Continually focussing on what to expect with that failure to execute seems pointless to me. It bears mentioning as 'what not to do', but the discussion should definitely be more of 'what to do'.

"What to do" when gross excess is not practical comes back to understanding the problem and what causes it. From that it is possible to look at outdoor measurements to evaluate the more ideal limits and how much things change as you get past those ideal limits. The 2 drivers I grabbed for reference both have similar Xmax but show notably different changes in their frequency response. Assuming much of their Xmax is put to use (so as to not be wasteful of resources) they will have somewhat different sonic signatures. For those not using many drivers at a fraction of their maximum capability, these differences can matter, and in the complex, modulated situation of real program material, the differences hinted at in the incremental sine sweeps are magnified.
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post #141 of 144 Old 11-15-2013, 11:50 AM
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mark has been perfectly clear on this across the several threads that it has been discussed. even if it is not "gross" excess, but anywhere there is a limitation, the same would hold. it's not that ideal isn't ideal, but that ideal is usually beyond most folk's means or the example cited wouldn't be eight x $900 drivers and 32+ kilowatts of amplifier power. the question then turns to what is the best strategy in that world. eq'ing for wideband response and then limiting the bottom end as the output surpasses its capability so as to continue to provide the bass where it matters the most is a completely reasonable approach.

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post #142 of 144 Old 11-16-2013, 06:42 PM
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Originally Posted by Mark Seaton View Post


I get the sense that some of the angst was coming from thinking I was suggesting that this is an issue no matter how many drivers are used, which is not what was intended.

Yeah, this was pretty funny…angst. I have angst over thinking about what you suggest. biggrin.gif

I never said the response reverts to the anechoic response, just that the changes are related to driver non-linearities and Fb of the system.

Sure you did, a half dozen times or so.
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Just take a look at the maximum output measurements Josh took recently of the Paradigm Sub 2. These pretty well track what is likely the pre-EQ response of the 6 10" woofers in the relatively compact package:

I'm sure of what you meant, so please don't offer an alternate meaning or add a missing sentence or two. smile.gif

You've said this ^^^ and related comments that suggest that somewhere at an as yet undefined point below X-max, drivers shed the EQ'd FR and some sort of as yet undefined combination of non-linearities becomes dominant, altering the sonic signature. And, as the sub is pushed to its limit, it will "pretty well track what is likely its pre-EQ response".


And these are way too coarse a display to see what is going on from curve to curve. A direct subtraction of the data between the curves is required to see finer details of what is or is no changing between curves. The spectrograms can be very interesting, but would tell dramatically more if they were instead difference measurements showing the deviation rather than the total result where we can only see distortion or omission in areas of limited content with a fairly coarse scale.

That's your opinion. The prog sweeps and SL data are detailed enough for me and correlate to what I hear vs the claim that they should be becoming audibly different and pretty well tracking the pre-EQ response as playback level is increased from -20dBRL to reference level.
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post #143 of 144 Old 11-16-2013, 06:46 PM
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Originally Posted by LTD02 View Post

mark has been perfectly clear on this across the several threads that it has been discussed. even if it is not "gross" excess, but anywhere there is a limitation, the same would hold. it's not that ideal isn't ideal, but that ideal is usually beyond most folk's means or the example cited wouldn't be eight x $900 drivers and 32+ kilowatts of amplifier power. the question then turns to what is the best strategy in that world. eq'ing for wideband response and then limiting the bottom end as the output surpasses its capability so as to continue to provide the bass where it matters the most is a completely reasonable approach.

I really have no idea what you're trying to say here. smile.gif

There's only one world, it doesn't require eight $900 drivers and 32KW and I'm aware of what Seaton has said on the subject and it's far from perfectly clear.
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post #144 of 144 Old 01-05-2014, 01:18 PM
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Some light Sunday afternoon reading for sure!...Wow! Some real heavy hitters here and I have forgotten how spirited these discussions can become.

I can't add anything except to say that I'm currently in heretic mode, as after seeing Ricci's excellent testing of the B&C 21SW152, I have developed a fetish for 21" pro sound drivers, replete with all that nasty High BL, f3, Fb and paltry xmax. However, I do like what I have seen in the 10-20Hz band distortion sweeps. I have just procured an RCF LF21N451 to replace the B&C 18SW115 and it is very likely that it will become a dual-opposed 2x21" at some point. The drivers may change, in hopes of a bit more xmax, but I have pretty much moved on from 15" and 18" drivers, no matter the xmax. The ability to get 2 hulking Neo 21" drivers into a single, smallish enclosure while still retaining a Q = .5 is just my own particular and polemic persuasion. I have my reasons and they have less to do with SPL than sound quality, not to impugn others tastes of course.

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