Compression Driver Compensation

[Robh3606]

Hello Zilch

Happy New Year!!


I believe that's harder than I've ever pushed 2435s, Guido, and if my sims are correct, 6 dB harder at 20 kHz than the Timbers filter:


Nothing is getting pushed. Guidos crossover does not increase the power into the driver. All of these crossovers work by attenuation of the midband response. That is all you are doing.


Also, I don't understand the reference to "Unity," or zero dB at the high end. The amount of boost is relative to where it begins, and, using the notch at 2 kHz as benchmark, Timbers has 14 dB to 20 kHz from there, whereas you've got 20 dB, looks like....

There is no boost. 0db is the reference to a given signal level in this case 2.83 Volts or 1 watt input. What you seem to miss is the 14db is really a negative number. It is 14db down from the input voltage. Simply said the network provides 14db of attenuation at the frequency.

Gregs filter is 7db from unity at 20K. Take a look at the voltage drive.

Rob:)

[Zilch]

Happy New Year, Rob! It's still 2007 here; I'm always behind you guys.... ;)

Whether we call it boost* or attenuation, the result is the same -- the HF driver is being driven harder at 20 kHz than it would be without compensation, by the dB differential. To achieve that, we attenuate the midband, yes, taking advantage of the higher sensitivity of the compression driver relative to that of the woofer. If it were not for the compensation, though, as with an exponential horn, for example, we'd be attenuating the full bandwidth of the HF driver to bring the two into balance.

The net result is that the compression driver is receiving differentially more drive at 20 kHz than it is at 2 kHz, and in the in the instance of 20 dB of differential, it's 100 times more power there. Others have suggested there are consequences to doing that, and in the case of 4430, I have earlier shown that increased distortion at the higher frequencies is among those consequences. Thus, when I am cautioned to apply compensation conservatively i.e., not to force 2435HPL beyond pistonic mode, and instead to let the response roll off above that, I look and find the specifications and actual practice of Timbers and others to be consistent with that approach.

I also find in my own experience that the Be diaphragm does not push all that easily beyond pistonic, or, at least, not as easily as the aluminum 2431H does, and I am seeing further evidence of that here....

*I found a JBL technical paper which used the term "boost" in describing the practice of CD compensation, which I consider as comprising renewed license to use the term in this context without guilt or shame.... :p


I think there is a fair amount of unit to unit variation above 10-12KHz with these drivers. One pair of drivers may require quite a bit more kick than another pair.Here's 18 of them:

http://audioheritage.org/vbulletin/attachment.php?attachmentid=22507&stc=1&d=1170485467
http://audioheritage.org/vbulletin/attachment.php?attachmentid=23506&stc=1&d=1173572501
http://audioheritage.org/vbulletin/attachment.php?attachmentid=24293&stc=1&d=1176274843

[Robh3606]

Hello Zilch




Thus, when I am cautioned to apply compensation conservatively i.e., not to force 2435HPL beyond pistonic mode,

You have no data at all to back that statement up. That is complete conjecture on your part. There should be no effect at all as far as the diaphragm remaining pistonic or not. There is no change in relative power input. You are running the drivers at a greatly reduced power levels across the board. With the power density of music there is very little power above 10K most of it is right where the attenuation is. You also reduce the actual diaphragm excursions by attenuating the midband. Also a good thing.


I look and find the specifications and actual practice of Timbers and others to be consistent with that approach.

That is what we are all doing. Then we season to taste.

Here are the power and distortion graphs for the 4430 horn. You can see the abrupt change in level in the second harmonic. You can also see how added power really makes this jump. These are at power levels that you would expect to be used in a professional application. I doubt any of us would push them that hard where your average power input would be 25 watts.

Attached are the THD plots for my 2435's from the above measurements. I don't see that same knee as the 4430. I don't have as much power going into them but the measurement is at typical levels I would use them at. If I dumped 25 watts into them I am sure the THD would rise but that is not going to happen. Especially out at 20K.

Rob:)

[Robh3606]

This started in another thread. Moved the posts over so we didn't hijack the thread.

Rob:)

[Ian Mackenzie]

Hi Rob,

I've always seen this driver EQ was cutting the mid band with a contour to match the mass rolloff.

You simply cannot have more than you got to start with.

I think what Zilch Von Curvee' is about is he's using active Eq.

But the point is once you normalise the compression driver output level to match the woofer if you looked at the overall voltage drives the compression driver voltage reduces with frequency.

We are assuming the compression driver and horn is at least 10 db more sensitive in the midband.

[Zilch]

You have no data at all to back that statement up. That is complete conjecture on your part. There should be no effect at all as far as the diaphragm remaining pistonic or not.It's the old "Intended purpose" thing I get smacked with all the time here; use the drivers within their designed performance envelope:

http://www.jblpro.com/vertec1/doug%20button%20258%20final%20rev%20c.pdf

Breakup mode is virtually by definition a bad thing.


We wished for the first break up mode of the diaphragm to be at the very top of the band of audibility.

Guido's "Pushing" the drivers into breakup mode at three times the rate of the Timbers filter above 10 kHz.

Me, I'm the premiere "Booster" here, you may recall, slavishly pumping up the 2435 VHF response up there, clear back to early work with the AM6212 filter nearly three years ago.... :D

[Robh3606]

Guido's "Pushing" the drivers into breakup mode at three times the rate of the Timbers filter above 10 kHz.

Like I said you have nothing to substantiate your allegations that these filters are driving the compression drivers into break-up mode any faster than they would normally get there.



It's the old "Intended purpose" thing I get smacked with all the time here; use the drivers within their designed performance envelope:


http://www.jblpro.com/vertec1/vertec_manual/VerTec%20Chap%205A.pdf

That is the correct document to cover the intended use. It tells you how to set up the Loudspeaker Controllers for the Vertec system. When used in the line arrays they actually do use active EQ to bring up the last octave. They obviously don't want to sacrifice SPL in this application. They add at least +12db @ 16K of active EQ depending on the controller. Then they are low pass filter it at 22K. You know like a CD player does.

You really think that attenuating the midband response is an issue when in the actual application they hit them with +12db of active EQ at 16K??

I would say that what we are doing definitely fits into intended use and designed performance envelope.

Rob:)

[Mr. Widget]

I would say that what we are doing definitely fits into intended use and designed performance envelope.I fully agree with that statement. :)

As far as I know, JBL started in this direction with the 4430/35s and has continued in that direction with many of their consumer and professional designs. Since they are not building professional monitors with compression drivers these days, I feel that only their work on the consumer side really relates to what we are doing when we are talking about high end music playback for the home. The Vertec and other JBL offerings are PA systems and as such have different requirements and sonic quality benchmarks.

In the consumer stuff the designs using these 3" drivers typically have additional tweeters also. The Everest II does carry on in the tradition of the 4430/35 especially when you consider the super tweeter being active only above 20KHz anyway... actually when you consider the 4435 with helper woofer, the Everest II is really an updated and upgraded direct descendant... but I digress.

As for this compression driver compensation thing, I am not alone, but I do think I am of a minority opinion in this group when I complain of the sonic "quality" of these compensated compression drivers... my criticism is not limited to the JBL 3" drivers either. I have tried to do a similar design with both the TAD TD-4001 and with the TD-4003. Both of these drivers are rated by their manufacturer as to having response to 20KHz and beyond... that may be, but like the smaller JBLs, this HF content is unacceptable to my ears. The Everest II's 476Be on the other hand seems to be free of the hard, edgy, metallic, unpleasant extreme top end that I have experienced with all of these other drivers. I asked Doug Button about this at last year's CES and he attributed it to the 476Be's higher mass break point. I have to assume he knows what he is talking about.;)

For me the solution is to "tack on" a super tweeter above the midrange and therefore only use the midrange in it's optimal performance area. This is a compromise too however as it introduces time alignment and comb filter related issues. I personally am less sensitive to these than I am to the "edgy" sound of a pushed driver.


Widget

[Zilch]

Like I said you have nothing to substantiate your allegations that these filters are driving the compression drivers into break-up mode any faster than they would normally get there.I don't recall alleging that they are driving them there faster, rather, that they are driving them harder once operating in the breakup region. That's certainly obvious in Guido's voltage drive curve where he kicks the rate of "Boost" up to ~13.2 dB/octave above 10 kHz to achieve 6 dB additional drive at 20 kHz, whereas Timbers maintains it linear at ~4.2 dB/octave, by my crude measurements of the slopes. That may not get it there any sooner, but it clearly increases the intensity of breakup mode output at the high end by that 6 dB, as is apparent in the frequency response curves illustrating the result. :yes:


You really think that attenuating the midband response is an issue when in the actual application they hit them with +12db of active EQ at 16K??Uhmm, the Timbers filter hits them with +12 dB of PASSIVE EQ at 16 kHz, as well, relative to the midband. At 20 kHz, he's at +14 dB; you guys are kicking it an ADDITIONAL +6 dB to +20 dB total there.

To the best of our knowledge, I believe, pistonic operation of 2435HPL becomes break-up mode somewhere in the region of 18 kHz, perhaps lower, consistent with what Doug Button states in that paper, with Greg Timbers' implementation of the passive equalization, and with 4313B's observations with respect to the preferred use of the device, according to design, in the UHF region.

http://audioheritage.org/vbulletin/attachment.php?attachmentid=22497&stc=1&d=1170461963

See also the Vertec curves. Even in SR, they do not push 2435HPL past 16 kHz; in fact, NO JBL product, either Pro or Consumer, employs it in the manner you contend to be "within the design performance envelope."

http://www.jblpro.com/vertec1/new_vertec/pdf/VT4889.pdf


I fully agree with that statement. :)You agree that "pushing" 2435 at 20 kHz by 20 dB over it's midband response falls within the design performance envelope of that driver?

On what basis, that we're not going to exceed the maximum power capacity of the driver doing that at home SPL levels?

Without regard for any compromise of sonic quality which may occur as a consequence of doing that?

[Robh3606]

Place Holder

Do you know what a negative number is??

Rob:)

[Mr. Widget]

You agree that "pushing" 2435 at 20 kHz by 20 dB over it's midband response falls within the design performance envelope of that driver? I wasn't being so specific, I meant that in general this is how JBL uses these drivers... as for how much is too much, in my opinion for critical listening applications it is all too much if a tweeter isn't there to help them out. This is not a scientifically derived opinion, simply one that I have concluded after listening to JBL's own systems as well as several of your experiments and also my own with both JBL and TAD drivers.


Widget

[tomee]

This started in another thread. Moved the posts over so we didn't hijack the thread.

Rob:)

Anyway to link to the original thread? I'd like to see where this all started. :)

[Zilch]

Anyway to link to the original thread? I'd like to see where this all started. :)http://audioheritage.org/vbulletin/showthread.php?t=19399

Especially:

http://audioheritage.org/vbulletin/attachment.php?attachmentid=30242&stc=1&d=1199124748

Versus:

http://audioheritage.org/vbulletin/attachment.php?attachmentid=30247&stc=1&d=1199164095

[Robh3606]

Good

Glad you posted both drives.

The difference between the 2 drives at 20K is 3db.


Uhmm, the Timbers filter hits them with +12 dB of PASSIVE EQ at 16 kHz, as well, relative to the midband. At 20 kHz, he's at +14 dB; you guys are kicking it an ADDITIONAL +6 dB to +20 dB total there.


How are you getting +12 db for Gregs Voltage Drive?? It's about -8db down. That means with 1 watt you have under 250mw at the driver.

With the active drive used in the Vertec system you have +12 @ 16KHZ with a fairly wide Q so it effects frequencies on both sides and actually does a good bit of the compensation for the mass roll off.

With 1 watt in with +12 db we have about 15 watts in so each driver see's about 5 watts.

Big difference between the two.

Rob:)

[edgewound]

I have a question.

What does all this have to do with a passive, full-range network?

You can't have "boost" of a particular frequency band within a passive network....excluding the use of an equalizer in a full-range, non-biamped system.

Is the term "boost" here relating to the relative amplitude of the high frequencies after attenuating the mid-frequencies, therefore giving the illusion of "boosted" high frequencies.

Biamping is a whole 'nother discussion of various voltage drives...but this discussion is a cacophony of semantics.


You can't get something from nothing.

[Zilch]

How are you getting +12 db for Gregs Voltage Drive?? It's about -8db down. That means with 1 watt you have under 250mw at the driver.You're measuring from the wrong place, Rob, by my view. Unity, or 0 dB is irrelevant to the issue under discussion, significant in an absolute sense only relative to the sensitivity of the particular woofer it's mated with, and how much "headroom" is available for accomplishing the passive compensation. Envision, for example, if you were working with a 103 dB woofer, set at 0 dB. The compensation for the HF would all be +dB.

I'm measuring the relative "boost" from the midband, where, presumably, there is none required. That's the baseline, for the discussion, not some arbitrary relationship to a random woofer, and I've chosen 1.8 kHz, where the Timbers filter begins the HF compensation, as the benchmark. Looking again, the Timbers "boost" is 13 dB to 20 kHz, whereas Guido's is 21 dB, and you earlier stated yours is even more aggressive than that. :dont-know

The major difference between what Timbers and Guido are doing occurs above 10 kHz, where Guido increases the rate of "boost" by three fold over what Timbers uses up there. I'm suggesting that there are likely sonic consequences inherent in doing that; I'd guess Timbers would desire to achieve flat response out to 20 kHz himself, if it were feasible within the performance limitations of the driver.

******

I'm having difficulty finding the response curve of the Timbers system as has been posted on several occasions by the member formerly know as Giskard here. Most notably, on at least one occasion, he stated that he was well satisfied with letting the driver roll off naturally at the high end, thereby avoiding certain (indeterminate) performance compromises. Does anyone have a link to that, or have it saved for reposting here? It'd be worthwhile to illustrate the differences in actual system frequency response which result from the two approaches under consideration here, as companion to the voltage drivers.... :yes:

[Zilch]

I have a question.

What does all this have to do with a passive, full-range network?

You can't have "boost" of a particular frequency band within a passive network....excluding the use of an equalizer in a full-range, non-biamped system.Yes, of course, and all of the participants understand the difference, but the net result is the same; the passive approach merely takes advantage of an available headroom differential between the woofer and HF driver to accomplish the task. In this case, the passive filter may be driven actively, as well, and several of us are using it that way. The active controllers do it the same way, when all is said and done, actually.

BUT, unless what is going on is viewed from the perspective of "Boost," it's easy to ignore the consequences, as is apparent in this discussion. Do we begin the midband attenuation at 40 kHz, 20 kHz, or 16 kHz? How rapidly do we have it occur in the last octave? No matter? I doubt it....

[Robh3606]

You're measuring from the wrong place, Rob, by my view. Unity, or 0 dB is irrelevant to the issue under discussion, significant in an absolute sense only relative to the sensitivity of the particular woofer it's mated with, and how much "headroom" is available for accomplishing the passive compensation. Envision, for example, if you were working with a 103 dB woofer, set at 0 dB. The compensation for the HF would all be +dB.

Well no. The amount of attenuation from unity or Zero Db line is what the networks is actually doing to the input signal. What the Zero Db line ends up being based on the woofer sensitivity is irrelevant to what the actual attenuation is. If the attenuation is 10db down from "0" you use 1/10 the applied power at that frequency. This is a passive crossover and in almost all cases the tailoring done is attenuation.


BUT, unless what is going on is viewed from the perspective of "Boost," it's easy to ignore the consequences, as is apparent in this discussion.

Nothing is being ignored. It's a choice that we are all free to make. If you want to run your drivers at -7db down as opposed to -4 go right ahead. If you are concerned that the break up modes could be more audible with the 3db change that's fine too. They may be. What ever is there is less that a 2425 judging from the distortion curves.

If you take Widget's position that you need a tweeter under any circumstance that's fine too.

The reason I posted my THD curves was because there was no indication it was rising or had a step function like the 2425 does in the 4430 crossover.

Rob:)

[edgewound]

Yes, of course, and all of the participants understand the difference, but the net result is the same; the passive approach merely takes advantage of an available headroom differential between the woofer and HF driver to accomplish the task. In this case, the passive filter may be driven actively, as well, and several of us are using it that way. The active controllers do it the same way, when all is said and done, actually.

..

I respectfully disagree with your point of view Zilch.

In a passive network fed from a full range signal, excluding an equalizer of course, you aren't adding gain to a particular filter section of the network. All you are doing...as Rob said...is taking energy away from the frequency range you are tailoring with a filter....there by giving a relative "boost" illusion which isn't a boost at all. It just seems to sound like one.

As far as woofer sensitivity is concerned, it makes all the difference in the world on compression driver distortion. The lower the sensitivity of the woofer the more you have to pad down the HF driver, which in turn makes gobs of headroom for that loafing driver that is hardly on due to it's gargantuan relative sensitivity/efficiency.

The controllers on the other hand do have some active tonal shaping going on which in turn does add some gain....just as a boost/cut equalizer does.

[Zilch]

Well no. The amount of attenuation from unity or Zero Db line is what the networks is actually doing to the input signal. What the Zero Db line ends up being based on the woofer sensitivity is irrelevant to what the actual attenuation is. If the attenuation is 10db down from "0" you use 1/10 the applied power at that frequency. This is a passive crossover and in almost all cases the tailoring done is attenuation.Zero dB is established by the woofer sensitivity in Guido's curves. The HF compensation curve will simply move up or down depending upon what that sensitivity actually is, and how hard the HF driver is being driven depends upon the absolute input voltage. dB is a ratio, relative to a reference, in this case, Guido's woofer sensitivity.

In the Timbers curve, Zero dB is where LEAP (or whatever was used) started the highpass slope, somewhere out beyond 200 kHz, according to my sims. There is no woofer, as the filter was designed for active use. It may be used as a passive filter, but the attenuation would have to be independently established relative to the sensitivity of the particular woofer used. It's apples and oranges here, with respect to unity.

Fortunately, however, since dB IS a ratio, the curves may be compared, not with respect to their relative attenuation from unity, but rather, with respect to the differential amount of attenuation, in dB, employed in each case to accomplish the compensation. To make that determination, two reference points are required: a starting point and an ending point. Whether we choose those points to be 10 kHz and 20 kHz, or 1.8 kHz and 20 kHz, it's clear that Guido is employing MORE attenuation between those reference points than Timbers, i.e., from the reciprocal perspective, more "Boost," in order to achieve flat response out to 20 kHz.

Guido acknowledges that, but offers that he does not hear anything untoward in the response. You state that your approach is even more aggressive, and it sounds fine to you, as well. I am merely suggesting (and I trust, demonstrating,) that this comprises a departure from what might be considered prudent practice according to the evidence I find from those who know more about the limitations of these devices than we do.

Everyone is entitled, and welcome, presumably, to do whatever they like in this regard, but I am continuously reminded here of the importance of operating within the limits of the design intent and the performance envelope, as best we are able to ascertain these, as outsiders not privy to them in their entirety, from what information is available to us.

For me personally, of course, there is delicious irony in this, having been the pioneering practitioner of pushing this specific performance envelope. I have since backed off from that somewhat, and am explaining my rationale for doing so. If I find a particular driver plays to 20 kHz on a particular horn or waveguide with compensation conservatively applied, so much the better. If it rolls off above 16 or 18 kHz, however, thats no big whoop, either, necessarily; what most matters is finding and working within the practical limits.... :yes:

[Zilch]

As far as woofer sensitivity is concerned, it makes all the difference in the world on compression driver distortion. The lower the sensitivity of the woofer the more you have to pad down the HF driver, which in turn makes gobs of headroom for that loafing driver that is hardly on due to it's gargantuan relative sensitivity/efficiency.Well, sure, but then you crank them BOTH right back up to deliver the requisite SPL to satisfy the use. The HF driver gets the same power independent of the woofer sensitivity.

That's all somewhat irrelevant, however. No matter how we get there, the fundamental issue here is whether it's appropriate to be delivering proportionately more power to the driver in breakup mode for the purpose of extending the frequency response flat to 20 kHz. :yes:

******

Headroom is headroom, and ultimately, as you say, you can't make something out of nothing, either passively OR actively. When you're out of gain, you're out of gain, in both cases, and it's merely sematics in this context, whether you call it gain or, reciprocally, attenuation, boost or cut....

[Robh3606]

In the Timbers curve, Zero dB is where LEAP (or whatever was used) started the high pass slope, somewhere out beyond 200 kHz, according to my sims. There is no woofer, as the filter was designed for active use. It may be used as a passive filter, but the attenuation would have to be independently established relative to the sensitivity of the particular woofer used. It's apples and oranges here, with respect to unity.

That is incorrect. The 0db line is simply where the woofer curve normally lies for the simple fact that you don't attenuate woofers. They have the lowest sensitivity and with the exception of a Zobel only have a low-pass filter to roll the response off at the crossover point. Here's a case in point for the L250Ti Jubilee Crossover.

That is my LEAP curve plot of Greg's crossover.


Guido acknowledges that, but offers that he does not hear anything untoward in the response. You state that your approach is even more aggressive, and it sounds fine to you, as well. I am merely suggesting (and I trust, demonstrating,) that this comprises a departure from what might be considered prudent practice according to the evidence I find from those who know more about the limitations of these devices than we do.

Considering that in actual use they use +12db @16KHZ of active equalization when running the Vertec system there is no question in my mind that these are extremely robust drivers and no passive EQ is going to force them to misbehave at the power levels we use them at.

I also see no sign of increased distortion in my sine measurements.


Rob:)

[Robh3606]

Well, sure, but then you crank them BOTH right back up to deliver the requisite SPL to satisfy the use. The HF driver gets the same power independent of the woofer sensitivity.

No you don't the attenuation of a passive network doesn't just disappear. You are still putting much less power into the compression driver. If the attenuation is 13db on the compression driver to match the woofer sensitivity the power ratio is 20:1 in favor of the compression driver. If you dropped 200 watts of broadband noise into the system you would have only 10 watts into the compression driver. The rest of the power is dissipated in the network as heat.

Rob:)

[Zilch]

That is my LEAP curve plot of Greg's crossover.I'm seeing a familiar 4-way there, Rob.

[Not that there's anything inherently wrong with that, of course.... ;) ]

[Robh3606]

I'm seeing a familiar 4-way there, Rob.

Well let's see how long this 4-way takes to happen. I have had the drivers for over a year and, started building the crossovers, and my surround receiver just died on me last night:banghead::banghead::banghead:

I am looking at options that have a real analog pass through for both CD and on the 5.1 input for SACD and DVD like on my older receiver . Really bad timing. Think I will start a new thread or revive an old one.

Rob:)

[Guido]

I planned to stay away from this discussion, but as I find my name here so often I should say something useful.

The reason for implementing a HF bump was simply a result of a 2 week listening session to the GT network. FOR ME (only my opinion) the speaker didn't sound fullrange. I didn't want to add a tweeter cause I believe in 2 way designs. So I did start modifications.

The sensitivity of my system is somewhere between 95dB and 96dB. So the 2435 is padded down very well. Even at the voltage drive peak it operates 4 dB lower than sensitivity.
You won't be able to squeeze out noticable distortion out of this speaker at medium to high home levels. The 2435 in this speaker sounds SO relaxed that I can't believe it.
I respect the listening impressions that you report and I respect that you hear "problems" of this driver above 10kHz or so. I just can't reproduce it.
Try different capacitors, try a nice amp or whatever. It will sound good....

[toddalin]

No you don't the attenuation of a passive network doesn't just disappear. You are still putting much less power into the compression driver. If the attenuation is 13db on the compression driver to match the woofer sensitivity the power ratio is 20:1 in favor of the compression driver. If you dropped 200 watts of broadband noise into the system you would have only 10 watts into the compression driver. The rest of the power is dissipated in the network as heat.

Rob:)

I have to agree with Zilch on this one. While the attenuation of the network doesn't disappear, one ends up turning up the volume control to compensate for the reduced compression driver output thereby pushing it just as hard. :blink:

If the compression driver puts out 100 dB at 1 watt at 1 meter, and you listen at 100 dB at 1 meter, you turn the amp up to where the compression drive is putting out 1 watt. If the network attenuates the driver by 10 dB, you turn the amp up to 10 watts to get the 1 watt. If the network attenuates the driver by 20 dB, you turn the amp up to 100 watts to get the 1 watt. But either way, you still end up with 1 watt at the driver. ;)

[Robh3606]

I have to agree with Zilch on this one. While the attenuation of the network doesn't disappear, one ends up turning up the volume control to compensate for the reduced compression driver output thereby pushing it just as hard. :blink:

??????

The compression driver is reduced by an attenuation network to match the woofer. It doesn't matter how much you turn it up the volume the attenuation in the network remains the same. With a passive network you don't turn the compression driver up seperately. They use the same amp source. You can't turn one driver up without doing both.

Rob:)

[Zilch]

I have to agree with Zilch on this one. While the attenuation of the network doesn't disappear, one ends up turning up the volume control to compensate for the reduced compression driver output thereby pushing it just as hard. :blink:Well, harder, actually, at 20 kHz, where we've bumped the drive up an addtional 6 - 8 dB over the Timbers filter at the same time.

I think Rob and Guido's view is, "No matter, these drivers can easily handle it."

I don't have any Aquaplas-damped drivers here, and there is some possibility the "damps spurious anomalies" thing is at play, but once those arrive, I'll certainly be breaking out the AM filters again and checking it out.... :yes:

[Zilch]

The compression driver is reduced by an attenuation network to match the woofer. It doesn't matter how much you turn it up the volume the attenuation in the network remains the same. With a passive network you don't turn the compression driver up seperately. They use the same amp source. You can't turn one driver up without doing both.Help me, now. Where's Guido getting the 25 dB of headroom shown in his voltage drives?

What IS the sensitivity of 2435HPL on these horns? 120 dB? :dont-know

[Ian Mackenzie]

Zilch,

Rather than bore the absolute crap out of us with all this conjecture how about setting up on real measurements at different power levels and EQ settings to actually prove what you are talking about.

There is not a lot of point to this thread otherwise .

ieIf you can shatter a diaphragm by forcing it as you refer to it would also least prove something.

[Robh3606]

Help me, now. Where's Guido getting the 25 dB of headroom shown in his voltage drives?

He has 5db more attenuation at the 1k-2K range than the original filter. If you look at the measured response it looks to me like you can see it there. Could be just the way the curves were spliced. You should really ask him anyway they are his measurements and Voltage Plots.

Bottom line is, he is happy.

Frankly I don't understand what your point is.

Rob:)

[edgewound]

What IS the sensitivity of 2435HPL on these horns? 120 dB? :dont-know

These are considered medium format drivers...3" diaphragm.

The 2425 has 110dB sensitivity...figure in that ball park, which is at least 15dB more than the woofer.

To my knowledge there is no published specs...but you should be able to get an idea with the instruments you have.

Vertec uses three drivers on a wave guide and they need to make lots of clean out put for concert venues.

They don't break a sweat in home use....unless you are completely deaf.

[toddalin]

Seem to me that all of this talk is based on compensation for the compression driver. But what of the horn that it is mounted on? This will also have a profound impact on the HF, even on-axis.

When I did crossovers for the surrounds that use the W10GTI and 2425, the resistor values for the HF compensation on the P. Audio PH-230 horn were completely different than a similar driver on the JBL 2370 horn. :blink:

[Zilch]

Frankly I don't understand what your point is.I believe my point is well made, Rob, and being once again advised to take my two-way crap elsewhere, I'll do that now.... :thmbsup:

[edgewound]

I believe my point is well made, Rob, and being once again advised to take my two-way crap elsewhere, I'll do that now.... :thmbsup:


Who said your two-way stuff is crap? THE EVEREST II IS BASICALLY A TWO WAY WITH VLF AND UHF AUGMENTAION THAT THEY DON'T NEED TO MAKE GREAT MUSIC>>>> BUT IT WILL SELL MORE SPEAKERS!!!!

The problem lies with your explanation of virtual HF boost and the attenuation of midrange and differences between driver efficiencies and the need to CUT DOWN the output of these extremely sensitive compression drivers to balance out the speaker system through a PASSIVE network by attenuating energy.

You are having a hard time swallowing the fact that we are saying your explanation is convoluted and confusing by your spinning of your point of view.

Get over it....geez.

I'm done with this one...should have been a few post back.

[Hoerninger]

Oh boys ...
:wave: :argue: :) :bash: ;) :duel: :) :blah: :cheers:
____________________
Peter ;) Happy New Year

[Robh3606]

I believe my point is well made, Rob, and being once again advised to take my two-way crap elsewhere, I'll do that now.... :thmbsup:

Zilch what’s with you??

Now you are questioning the validity of the Voltage Drives??

Do you think LEAP is wrong?

The original drive is without the highpass. Do you know what the horns gain is from 1-2K?? Is there a bump there?? If so do you need to bring it down a bit?? That could be the reasons why the voltage drive is lower.


Rob:)

[Zilch]

Now you are questioning the validity of the Voltage Drives??No, not at all. I am merely reading them.

To the nearest whole numbers:

1) How much compensation does Guido's filter provide between 1.8 kHz and 20 kHz? 21 dB. Do you agree?

2) How much compensation does the Timbers filter provide between those same frequencies? 13 dB

3) What is the difference between the amount of compensation Guido is using between those frequencies versus what Timbers uses? +8 dB

Stay with me now:

4) How much compensation does Guido's filter provide between 10 kHz and 20 kHz? 10 dB

5) How much compensation does the Timbers filter provide between the same frequencies? 4 dB

6) What is the difference between the amount of compensation Guido is using between those frequencies versus what Timbers uses? +6 dB

So, overall, above 1.8 kHz, Guido is applying 8 dB more compensation than Timbers, for the apparent (and stated) purpose of achieving a more full range response.

Of that, 6 dB (6.5 dB, actually) more is being applied in the last octave alone.

Now, back to my original statement quoted in Post #1 of this thread:


I believe that's harder than I've ever pushed 2435s, Guido, and if my sims are correct, 6 dB harder at 20 kHz than the Timbers filter.It's 8 dB, actually, overall, and more like 6.5 dB in the last octave.

I'm not saying that Guido or anybody else shouldn't do that, nor do I contest any observation anybody may have with respect to how that might sound. I am merely noting that it comprises a significant departure from what that filter's designer considered appropriate for use with essentially the same driver/horn combinaton....

*******


The 435Be's are running with the circuit posted above (charge coupled of course) actively crossed over at ~ 750 Hz and are 6 dB down at 20 kHz. This is the current pinnacle version of the 12-inch 2-way.

[Robh3606]

I think we really need to look at them as fixed points and plot them.

Here we go

Gregs Guido Difference

2K -19 -25 -6

5K -14 -19 -5

10k -11 -15 -4

20K -7 -4 +3

Guidos curve is below the average level compared to Gregs except the last octave. There is an 11db delta from 10-20k but he starts at a lower level. These are again negative numbers and you have to look at them systematically to see exactly whats going on. Looking at the total compensation as just whole numbers is misleading. What's important is where the delta's are and what they are doing.


I am merely noting that it comprises a significant departure from what that filter's designer considered appropriate for use with essentially the same driver/horn combinaton....

It may be a departure but don't you think Greg would be one of the first to say tune it up the way you like it??

Just becasue it departs from the curve doesn't mean it's wrong. These drivers have to work in a real livingroom and they may sound just great that way depending on the acoustics.

Honestly we can stand here all day poking at each others systems looking at the graphs but what counts is what it sounds like. Unfortunately we can't just pull up a chair and have a listen in our collective livingrooms.

Rob:)

[Zilch]

From your comparison, I'd say we've come to the same conclusion via different methods, Rob.

Note the quote I added to the post immediately above: Greg's using a different woofer (1200FE, not shown,) and is actively crossed. That explains why Guido starts lower, I believe. :thmbsup:

[I think we're all actively crossed, actually.... :p ]

[4313B]

I'll throw some curves in here just for fun. The Maps tell what the curves are.

[4313B]

.

[4313B]

Greg's filter (2nd rev) for 476Be to replace the 435Be on H4338 horn (no longer applicable due to active bi-amping instead)

Note that the filter was applied to the 476Be on the H9800 horn fo these runs.

[4313B]

Modified Everest II filter (Giskard rev 1)

Plus or minus 1.7 dB from ~ 900 Hz to ~ 13 kHz on H9800

Modified Everest II filter (Giskard rev 2)

Plus or minus 1.9 dB from ~ 900 Hz to ~ 17 kHz on H9800

These curves are without any notch filters. I might be able to get to plus or minus 1.5 dB with a few notch filters. I'm not convinced yet that it would be worthwhile.

These are examples of what the Project May top end looks like.

[4313B]

The reason for implementing a HF bump was simply a result of a 2 week listening session to the GT network. FOR ME (only my opinion) the speaker didn't sound fullrange. I didn't want to add a tweeter cause I believe in 2 way designs. So I did start modifications.Understandable. And both Doug and Greg would be the first to suggest that each person tailor their system to what they personally prefer.
The 2435 in this speaker sounds SO relaxed that I can't believe it.No doubt!

I respect the listening impressions that you report and I respect that you hear "problems" of this driver above 10kHz or so. I just can't reproduce it.
Try different capacitors, try a nice amp or whatever. It will sound good....I admire your diplomacy. And you're right, it sounds really nice.

Someone asked about the original response curve of the 435Be on the H4338 in Greg's home system and I was able to find it. The date on the file is incorrect. That's merely the date is was last opened and then saved off again. I really hesitate to post it because some people freak out when they don't see graphs with flat response to 20 kHz and beyond. But here it is and they will just have to go to therapy afterwards. When Greg says it sounds really nice he isn't joking and that's pretty much the whole point of the exercise.

( For those who aren't up on the story, Greg had a 3-way system using the 1200FE-8, 435Be with H9800 horn, and the 045Be with its horn molded into the end lip of the H4338 horn. At some point he decided to redo the system as a 2-way so he unhooked the 045Be and reworked the passive filter on the 435Be to extend its response. He said that the results better suited his personal taste. I believe that this was the version Don McRitchie heard and his comment can be read here: http://audioheritage.org/vbulletin/showpost.php?p=185959&postcount=4 In photo number 5 one can see the disconnected 045Be.)

[4313B]

It may be a departure but don't you think Greg would be one of the first to say tune it up the way you like it??Absolutely.

We've gone over this behavior about a thousand times now Rob.

Just becasue it departs from the curve doesn't mean it's wrong. These drivers have to work in a real livingroom and they may sound just great that way depending on the acoustics.Yep. I think that's a real tough concept for some. Another forum member made a suggestion, perhaps some people are over obsessed with curves because they can't really hear what's going on. They figure if they can obtain a certain response curve then it must sound good.
Honestly we can stand here all day poking at each others systems looking at the graphs but what counts is what it sounds like.Yeah, the chatter gets real aggravating at times. Greg did what he saw fit, Guido did what he saw fit, and both seem pretty damn happy with the results.

[Zilch]

Yeah, the chatter gets real aggravating at times. Greg did what he saw fit, Guido did what he saw fit, and both seem pretty damn happy with the results.I'm standing up for LE14H-3s in detritus L55s the world over, and it would appear that I'm not the only member who rather likes that alignment:


I currently have four LE14H boxes, two ~ 2.0 cu ft @ ~ 32-34 Hz as well as two stock 240Ti boxes. I personally prefer the 2.0 cu ft boxes due to their increased portability but that's my personal preference. They're "bookshelf" size as opposed to "floor standing" size.


:D

[4313B]

I'm standing up for LE14H-3s in detritus L55s the world over, and it would appear that I'm not the only member who rather likes that alignment:





:D
3.5 to 4.0 cu ft tuned to 28-30 Hz for floor standing systems. The L250/250Ti box/tuning is king for floor standing systems based on the LE14H-1 or LE14H-3. The slightly smaller 240Ti isn't bad either.

The L55 box is completely unsuitable for a high performance loudspeaker system. It's an end table.

But... you know... that could be a nice project for you. Restore a pair of L55 or L65 boxes with LE14H-3's in them and the PT-F95HF / 2452H-SL combo and then start a thread on how you did it all. Half a dozen posts with photos of the finished boxes, nice blue grilles, smoked glass tops and modern JBL components inside with cc networks. Maybe a post of the voltage drive of your network and an impedance/response curve. Those boxes looked very nice when new.


I can't find my documents on the 240Ti and 250Ti right now but I think they were ~ 3.5 cu ft @ ~ 30-32 Hz and 4.0 cubic feet @ ~ 28-30 Hz respectively. The Citation 7.4 box was ~ 3.4 cu ft @ 28-30 Hz. The 1400 Array box was ~ 3.2 cu ft @ ~ 30-32 Hz.

I currently have four LE14H boxes, two ~ 2.0 cu ft @ ~ 32-34 Hz as well as two stock 240Ti boxes. I personally prefer the 2.0 cu ft boxes due to their increased portability but that's my personal preference. They're "bookshelf" size as opposed to "floor standing" size. At any rate, you should see a pattern here - 1.5 to 5.0 cu ft tuned in the 28 to 34 Hz range - nothing has really changed since the 70's in that respect. I personally feel that the 250Ti box is the largest practical volume with the lowest practical tuning - that's just my opinion.

[Ian Mackenzie]

Thanks for posting this 4313B.

When I had my 2344 horn up and going I set them up for a slight roll off at 16 kertz on axis.

When seated they were around about 30 degrees off axis and sounded just right . The difference was measurable. On axis they were on the bright side.

Same thing with the 4345.

Flat on axis in your face is not always the answer in reality.

Ian

[4313B]

Flat on axis in your face is not always the answer in reality.I distinctly remember having issues with the 4430's in certain rooms on-axis. They didn't work in every room I had them in over the years.