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Author Topic: JBL 6300+4300 monitor mayhem  (Read 6797 times)

Bill Mueller

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JBL 6300+4300 monitor mayhem
« on: May 28, 2007, 10:06:37 am »

Hello All,

I already posted this on the Whatever Works forum because it is my local hangout. However, it is probably better suited to this forum. This problem has been bugging me for a few years actually and I just got around to putting it into words. I don't know if I will make any friends with it, but I think it is something worth discussing.

Francis, I am very interested in your take on this. BTW, I am the guy who made the Clearview Monitor Lifts so many years ago.

For 30 years I have taught my students that you MUST correct the acoustics of the space BEFORE you place speakers in that space if accurate monitoring is the desired result. A good acoustic space can then accommodate multiple monitors and the differences between them are actually the differences between them, if you know what I mean. Eq'ing studio monitors results in a mix product that is a nasty inversion of the nasty room modes you are mixing in, if the monitors were fairly flat to begin with.

In the old days one of my techniques for room testing was to run long speaker cables out into a field to a to-be-tested speaker lying on its back in the grass. Then I would put a B&K omni mic 3' over the speaker and send pink noise through the speaker at about 90db. This is a decent recreation of an anechoic chamber for almost no money and will reveal the true frequency response of the speaker. (Since I grew up in a corn field, this was not too much bother to the neighbors, who thought I was insane anyway.)

I would then place a 27 band eq in line with the speaker and flatten the response out as needed. This is mostly just a good way to determine that actual deviation from linearity a real world speaker will present. After adjusting the monitor to pink noise, I then mark the faders on the eq and take the whole rig back into the control room.

Now I set the speakers up and put the mic at the listening position and turn on the juice. Next I readjust the eq to flat and mark my new positions. The differences between both settings is the ROOM.

What is the purpose of this exercise? To understand just how much of what I am hearing in the control room is the speaker response and how much is the ROOM. In any case, I NEVER leave the speaker eq'd to the room! That is disaster. Then instead of knowing how the room is affecting my mix product (the two mix tape or disc) I would in effect, cover all the room effect and hide it from my mix decision making, essentially blinding me to half or more of the causes of the character of the sound I am listening to.

I digress.
PA systems are almost completely different. In a PA, the product is what the audience is HEARING at the moment and it does not matter how whacked out the two buss is to get the room to sound right. That includes massive EQ and compression, whatever it takes. Live monitors are exactly the same. The SOUND is the product, so go for it. As long as you don't blow something up.

Now it seems that JBL (of all companies!) has lost their way and gotten the two circumstance totally mixed up. IMHO they are selling heresy in an entire series of monitors from the JBL 6300 on down and calling them a miracle (religious references intended, I'm waiting for acoustically transparent walnut volume knobs next). When you use the auto setup on these speakers, you are using them to nullify the room effect on your mix and skewing the MIX PRODUCT in the inverse amount. How could such a good company get this sooo wrong?

The other thing I find odd is that I have heard very few acoustician's and other manufacturers criticize this approach. Or did I just miss it? Is JBL too big to go against? What is up here? Ethan, what do you think about this stuff? Am I still out in left (corn) field?

Ok, I'll stop now. What I am hoping for from you guys is some feedback on how your mixes translate when you have used the auto setup on a pair of these monitors. I don't give a rats ass what they sound like or if you can hear more detail or any of that personal yada-yada about small monitors and such.

I want to know if they WORK and maybe if anyone knows...WHY?

Thanks for you help.

Best Regards,

Bill
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Ethan Winer

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Re: JBL 6300+4300 monitor mayhem
« Reply #1 on: May 28, 2007, 01:17:55 pm »

Bill,

Quote:

I have heard very few acoustician's and other manufacturers criticize this approach ... Ethan, what do you think about this stuff?


I've been a very vocal critic of EQ and DSP that claims to correct room acoustic problems, and I've written about it extensively. EQ does not work in small rooms for many reasons, though as you observed it can help in an auditorium. This article explains all the key points, and proves that even the expensive Audyssey system is a crock:

http://www.realtraps.com/art_audyssey.htm

There's also a link at the top of this article to another article that shows in great detail why EQ is doomed to fail.

--Ethan

Mark Donahue

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Re: JBL 6300+4300 monitor mayhem
« Reply #2 on: May 29, 2007, 05:44:28 pm »

Ethan,
While I agree with you about the EQ based systems, there are some DSP based systems that can make a marked improvement in performance at the listening position.
I was one of the field setup engineers for Sigtech (Cambridge Signal Technologies) for nearly 10 years and did well over 500 system calibrations in that time.  While I don't suggest that it can turn a bathroom into a mastering studio, there are significant improvements that can be realized with active room correction. The most significant of these in the bottom octaves, which we all know are the most difficult to deal with using mechanical treatment. The list of Sigtech users speaks for itself, Remote Recorders, Masterdisk, CBC studios, Philips classics... These people are not audiophool's that can be tricked by applying some phasey smear to the signal and calling it better.
As with any system of this type, the knowledge and taste of the engineer doing the calibration has the greatest effect on the final results.
We used the system to improve the monitoring environments of our location control rooms all over the world for many years. Unfortunately the lack of 96k, surround monitoring and limited budgets/time have reduced the viability of carrying the system with us to remote locations.
All the best,
Mark
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Mark Donahue
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Soundmirror, Inc.
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jetbase

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Re: JBL 6300+4300 monitor mayhem
« Reply #3 on: May 29, 2007, 09:07:02 pm »

How does the positioning of the monitors (eg. near a boundary) affect the frequency response & treatment in this case? What I mean is, if the room is ok but you need to have the monitors (assuming free standing) near a front or side wall, which I would assume would increase low frequencies, should you flatten the response by eq or by acoustic treatment?
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Bill Mueller

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Re: JBL 6300+4300 monitor mayhem
« Reply #4 on: May 30, 2007, 09:24:41 am »

jetbase wrote on Tue, 29 May 2007 21:07

How does the positioning of the monitors (eg. near a boundary) affect the frequency response & treatment in this case? What I mean is, if the room is ok but you need to have the monitors (assuming free standing) near a front or side wall, which I would assume would increase low frequencies, should you flatten the response by eq or by acoustic treatment?


Glenn,

This is a great question.

When you move a monitor away from full space loading (console bridge) to near 1/2 space loading (against the wall surface), the change in frequency response is broadband and linear. It is appropriate to electronically adjust the output of the monitor to balance the speaker output. This condition is fundamentally different than the boundary effects that happen when a speaker is placed out in the room

As we have discussed on other threads in Whatever Works, in near 1/2 space loading, the cancellation frequency (1/4 wavelength) is high enough that very little energy is coming off the back of the cabinet to negatively affect the sound coming off the front of the speaker. As a result all of the frequencies affected by near 1/2 space loading are very close to being in-phase. In fact, the resultant sound is very similar to just making the speaker baffle MUCH larger (true 1/2 space loading). The linear, in-phase, low frequency support becomes part of the cabinet response, is perceived to BE the cabinet and is all in the near field. Under these conditions, a simple contour switch, designed to adjust the low frequency response of the speaker is appropriate.

However, room boundary effect reflections that arrive at the listening position out of phase with the direct sound, create narrow response notches 20db (or more) deep, when the speaker is in fact linear at those frequencies. These reflections are actually hiding the true linearity of the speaker and giving the listener the impression that the speaker has a dip in it's response at those frequencies. In addition, because these effects are harmonically related, entire notes can be obscured with the fundamental and second harmonic masked, while other notes are unnaturally supported in the same way. The result is that certain bass notes leap out of the speakers and others disappear.

Correcting these room induced anomalies with eq, might make the speakers sound better (in one tiny sweet spot), but because the speaker's ACTUAL low frequency output is now very non linear, the operator does not have a linear reference like he/she would have with a linear speaker in a linear environment. Mixing mistakes would seem to me to be much more possible under these conditions.

However, that is why I am asking the question on this thread. For those who use the JBL speakers, do they work for you?

Best Regards,

Bill
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Ethan Winer

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Re: JBL 6300+4300 monitor mayhem
« Reply #5 on: May 30, 2007, 01:51:20 pm »

Mark,

Quote:

there are some DSP based systems that can make a marked improvement in performance at the listening position


The problem is that "listening position" IMO needs to encompass both ears at the same time, and in a small room DSP can't do even that. In a 35 by 45 foot professional control room with a high ceiling the peaks and nulls are not so highly localized. But in a typical domestic size room the response changes drastically over spans as small as a few inches. That's one of the main points of my Audyssey article. This article delves even deeper into that phenomenon:

http://www.ethanwiner.com/believe.html

Quote:

The most significant of these in the bottom octaves, which we all know are the most difficult to deal with using mechanical treatment.


Agreed, and I'm not opposed to using EQ below 50 Hz or so. My big SVS subwoofer includes a one-band cut-only parametric EQ, and I use that to reduce by a few dB the most prominent length mode in my living room home theater system. But you don't need to spend thousands of dollars for something that claims "DSP" when the main thing it does is simple EQ.

--Ethan

Ethan Winer

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Re: JBL 6300+4300 monitor mayhem
« Reply #6 on: May 30, 2007, 01:57:03 pm »

Glenn,

Quote:

should you flatten the response by eq or by acoustic treatment?


Bill explained the issues very well. There are two different effects - proximity which is a shelving boost, and comb filtering (often called SBIR) which is a series of peaks and nulls. For the comb filtering portion bass traps yield better results than EQ. But EQ is perfectly valid for countering a shelving shape boost, and most active monitors include a shelving EQ for exactly this reason. In fact, you can use the acoustic gain from boundary proximity to your advantage. Lowering the bass levels with EQ lets the speakers play louder with less input signal, and that yields lower distortion.

--Ethan

Mark Donahue

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Re: JBL 6300+4300 monitor mayhem
« Reply #7 on: May 30, 2007, 02:52:46 pm »

Ethan,
By the looks of it, the Audyssey is nothing more than an an automatic parametric EQ. I agree whole heartedly that static EQ is not a solution for room correction.
What I am talking about is active room correction like the Sigtech AEC and TacT RCS. These devices apply a time delayed correction signal that can reduce the levels of early reflections at the listening position by as much as 18 dB. Also, rather than reduce the size of the sweet spot, with proper setup, it increases the size of the sweet spot appreciably.
 
Quote:

The problem is that "listening position" IMO needs to encompass both ears at the same time, and in a small room DSP can't do even that.

In the system I spoke about there is actually individual measurements made for the left and right channels. This allows the placement of the microphone to account for a lager sweet spot with less correction or a smaller one with more. With any acoustic measurement system, measuring from a single point is space will not give any perspective on the real issues at hand. Much like a snapshot versus a motion picture.
To further the point, active time based correction is actually specifically a small room correction system . All the correction signals are within the first 50ms.
It just worries me when you make blanket statements that there is no such thing as DSP room correction, especially when you have a vested interest in promoting a product. Given that the company I contracted for has long since become defunct, I don't really have a dog in this fight. It just struck a nerve.
All the best,
Mark
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Mark Donahue
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Soundmirror, Inc.
Boston, MA
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jimmyjazz

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Re: JBL 6300+4300 monitor mayhem
« Reply #8 on: May 30, 2007, 04:10:58 pm »

Mark, how would you describe the effects of DSP correction at room locations OTHER than the one you corrected for?  Did the rest of the room get subjectively "worse"?
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Bill Mueller

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Re: JBL 6300+4300 monitor mayhem
« Reply #9 on: May 30, 2007, 04:29:26 pm »

Mark,

I think we might have met many years ago. I was with Sheffield, engineering a remote for the Boston Pops and we bought a couple of reels of Sony Dash 1/2" at Soundmirror. Nice place.

Anyway. I am not arguing that active electronics cannot improve the linearity of a speaker in ANY environment. I get that. In fact, today I would not set up a PA without active analysis, eq, limiting, compression and even time delay in a large system.

My argument is that creating linearity in a studio monitoring system by distorting the source signal, instead of correcting the actual problem of acoustics, yields a non linear mix product, when the engineer things he/she is creating a linear mix product. In addition, the engineer no longer knows WHY they are making their mix decisions, on the basis of the actual 2 buss signal or the room acoustics.

I would also add that I instigated this thread because the issue bothers me. So far, I can find no flaw in Ethan's logic, whether or not he has a product to sell. I have also asked others like yourself to weight in because if the laws of physics (or studio design) have changed lately, I would like to know about it.

Best Regards,

Bill
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Mark Donahue

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Re: JBL 6300+4300 monitor mayhem
« Reply #10 on: May 30, 2007, 04:53:52 pm »

jimmyjazz wrote on Wed, 30 May 2007 16:10

Mark, how would you describe the effects of DSP correction at room locations OTHER than the one you corrected for?  Did the rest of the room get subjectively "worse"?

Jim,
The amount of artifact in other places in the room is directly related to the amount of correction required to make the "sweet spot" better. Typically, there is a progressive decrease in the perceived correction as you move away from the sweet spot, not crazy shifts.
When you are using one of these systems, normally you are trying to make a usable listening position that allows the listener to make critical judgements. For many situations I actually made several different sets of measurements and calibrations in different listening positions, including the artist couch in the rear and side positions. This allowed the engineer to switch in the appropriate correction for the listening position in question.
The corrections made by any of these time based correction systems are by definition for a specific area or listening position, much in the same way that the RFZ is not the whole room but a specific area. We can't break the laws of physics... But I hear a new marketing slogan "Perfect sound everywhere!"
The funny thing is that normally, the most important factor in getting good results was making the physical changes in speaker placement and room treatment that allowed the correction system to have to do the least amount of correction. In an ideal world you build rooms that don't need correction.
All the best,
Mark
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Mark Donahue
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Soundmirror, Inc.
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Mark Donahue

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Re: JBL 6300+4300 monitor mayhem
« Reply #11 on: May 30, 2007, 05:33:14 pm »

Bill Mueller wrote on Wed, 30 May 2007 16:29

Mark,

I think we might have met many years ago. I was with Sheffield, engineering a remote for the Boston Pops and we bought a couple of reels of Sony Dash 1/2" at Soundmirror. Nice place.

Hey Bill,
I remember that. Wasn't that a Pops TV thing?

Quote:

My argument is that creating linearity in a studio monitoring system by distorting the source signal, instead of correcting the actual problem of acoustics, yields a non linear mix product, when the engineer things he/she is creating a linear mix product. In addition, the engineer no longer knows WHY they are making their mix decisions, on the basis of the actual 2 buss signal or the room acoustics.

I don't follow your logic. The correction systems are part of the monitoring chain. The way that I think about it is that you are trying to remove the variations in acoustics from the equation. It doesn't matter if you are using mechanical acoustic treatment or DSP.  If you boost the subwoofer by 10 db, your printed mixes will tend to be bass shy. If you have huge valleys and peaks in room response, your mixes will tend to have the corresponding opposite peaks and valleys. Back when NS-10's were all the rage, I could tell by the mixes that they were mixed on NS-10's by the sound of the master.
However, if you create a listening environment that yields consistent and even response, your mixes will translate.

Quote:

I would also add that I instigated this thread because the issue bothers me. So far, I can find no flaw in Ethan's logic, whether or not he has a product to sell. I have also asked others like yourself to weight in because if the laws of physics (or studio design) have changed lately, I would like to know about it.
Best Regards,
Bill


Funny thing is that I wrote my response above before I read your message. Like I said there,I'm in complete agreement, you can't break the laws of physics.  I am also in complete agreement with Ethan WRT the "Auto EQ" systems that people are pushing. My point was really that there are different ways to achieve active electronic room correction, not all of them are bunk.  
All the best,
Mark
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Mark Donahue
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Ethan Winer

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Re: JBL 6300+4300 monitor mayhem
« Reply #12 on: May 31, 2007, 02:48:12 pm »

Mark,

Quote:

By the looks of it, the Audyssey is nothing more than an an automatic parametric EQ. I agree whole heartedly that static EQ is not a solution for room correction. What I am talking about is active room correction like the Sigtech AEC and TacT RCS.


Audyssey claims their product is a sophisticated DSP-based room correction system. They claim it reduces modal ringing, which I proved it does not. They also claim it can reduce reflections at mid and high frequencies, which is impossible even in theory for an area larger than about one cubic centimeter.

Quote:

These devices apply a time delayed correction signal that can reduce the levels of early reflections at the listening position by as much as 18 dB. Also, rather than reduce the size of the sweet spot, with proper setup, it increases the size of the sweet spot appreciably.


I'm sorry, but I cannot accept that any DSP system can counter early reflections over a usefully large area. I'd definitely need to see a comb filter response with and without before I'll change my opinion. If you think about it, the level balance needed to counter early reflections is incredible. That is, the level of the countering signal has to be within a fraction of a dB of the reflected sound, and also be timed to arrive at precisely the same moment. As soon as you move your head even one inch the critical balance and timing are destroyed. However, I'm willing to change my opinion in a heartbeat if you or anyone else can show hard proof in the form of response graphs taken at several listening locations.
 
Quote:

With any acoustic measurement system, measuring from a single point is space will not give any perspective on the real issues at hand.


I can't see why that would be the case. The only response that matters is the one precisely at each of the listener's two ears.

Quote:

It just worries me when you make blanket statements that there is no such thing as DSP room correction, especially when you have a vested interest in promoting a product.


I sell acoustic treatment because I believe in it, not the other way around. If I believed in DSP systems I'd be in the business of selling those. What I do for a living has no bearing on the truth of these vendors' claims. Either they can prove their systems are effective or they cannot. In the case of Audyssey they make claims I have proven are false. If someone gives me the chance to measure the effectiveness of another DSP system I'll jump at the chance. I did those Audyssey tests not because I sell bass traps and first reflection panels, but because I want to understand the science and get to the truth. I assure you that's my only agenda here.

--Ethan

Ethan Winer

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Re: JBL 6300+4300 monitor mayhem
« Reply #13 on: May 31, 2007, 03:10:54 pm »

Bill,

Quote:

So far, I can find no flaw in Ethan's logic, whether or not he has a product to sell. I have also asked others like yourself to weight in because if the laws of physics (or studio design) have changed lately, I would like to know about it.


I've found that the best "logic" to use with this kind of stuff is to demand proof of efficacy in the form of measurement data. As I noted in my Audyssey article, I emailed them asking for proof, and a few other questions, and they didn't even give me the courtesy of a reply. If you think about it this makes sense. I mean, why waste time humoring Ethan when they have scores of gullible magazine writers and editors, eager to bring news to their readers of this wondrous new technology. Never mind that it's a total crock (at least in the case of the Audyssey) - this is what their readers want to see, so dammit this is what they'll tell them.

BTW, I see this every bit as much in the pro audio and home studio magazines as in the audiophoole publications. Some of the misinformation has been repeated so many times over the past 20 years that now much / most of the conventional wisdom about the science of audio is just wrong.

Sorry for the rant! Twisted Evil

--Ethan

Bill Mueller

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Re: JBL 6300+4300 monitor mayhem
« Reply #14 on: May 31, 2007, 05:45:13 pm »

Mark Donahue wrote on Wed, 30 May 2007 17:33

Bill Mueller wrote on Wed, 30 May 2007 16:29

Mark,

I think we might have met many years ago. I was with Sheffield, engineering a remote for the Boston Pops and we bought a couple of reels of Sony Dash 1/2" at Soundmirror. Nice place.

Hey Bill,
I remember that. Wasn't that a Pops TV thing?


Yes it was!

Quote:


I don't follow your logic. The correction systems are part of the monitoring chain. The way that I think about it is that you are trying to remove the variations in acoustics from the equation. It doesn't matter if you are using mechanical acoustic treatment or DSP.  If you boost the subwoofer by 10 db, your printed mixes will tend to be bass shy. If you have huge valleys and peaks in room response, your mixes will tend to have the corresponding opposite peaks and valleys. Back when NS-10's were all the rage, I could tell by the mixes that they were mixed on NS-10's by the sound of the master.
However, if you create a listening environment that yields consistent and even response, your mixes will translate.


I'm sorry that my logic was unclear to you. I will try again. There are any number of (obvious to me) problems associated with brute force equalization on the control room monitor path.

First the idea that an acoustical condition where a waveform is reflected into the listening area, out of phase and 5-30 ms delayed, causing multiple massive dips and peaks at the listening position is the SAME as a non linearity in the direct path, near-field information from the speaker is flawed. Comb filtering and harmonic resonances up into the 500hz range make the aforementioned condition extremely complex and reactive. Under those conditions, moving your listening position 24" (where the artists sit) away from dead center, will result in a completely different set of conditions and sound. Now add three or four early, or early-early reflections and the eq network needed to compensate for all the junk could run into dozens of filters, pumping +20db or more into multiple frequencies in the monitor chain.

In this day and age of "+1db on the vocal at 10K" talk, I don't know anybody who would purposely monitor through a system that they knew had so many filters in line. Just think of the phase shifting associated with each 20db multi pole filter!

Adding 20db of gain to a 1/10th octave filter at 200hz will reduce system headroom by exactly 20db resulting in the inevitable increase of distortion in the system. There is no free lunch here that I can tell.

Back in the day, we all had 27 band eq on our mains, and they generally sounded horrible to the point that everybody stopped listening to them and moved on to near field monitors that they could trust. Bob Hodas is one of the only people I know that continues to voice monitors, but he does not do this to compensate for acoustics as I understand it, but to compensate for small changes in systems as they age. I think he would agree that acoustics should always be optimized before voicing.

What bothers me about the JBL advertising is the "magic pill" approach to monitoring that I believe will get anyone but the most expert engineers in trouble.

I have still not heard from anyone who uses the JBL DSP and relies on it to corrrect their room. Is anyone out there?

Best Regards,

Bill
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“The Internet is only a means of communication,” he wrote. “It is not an amorphous extraterrestrial body with an entitlement to norms that run counter to the fundamental principles of human rights. There is nothing in the criminal or civil law which legalizes that which is otherwise illegal simply because the transaction takes place over the Internet.” Irish judge, Peter Charleton
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