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post #1 of 28 Old 08-24-2014, 02:45 PM - Thread Starter
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Compensating for speaker distance

I have some rear speakers in my 5.1 setup that are 10 feet from the listening position. My front two speakers are 7 feet and the centre speaker is 6 feet away. My subwoofer is about 7 feet away. In my receiver settings I have set the distances to 7 feet for all of the speakers. However, I am unable to set the rear speakers to 10 feet unless I set the front two speakers to 10 feet. I know my set up is less than ideal, but that is how it has to be because of the layout of my house. There is a setting in my STR DA2000ES that allows me to increase the loudness of my rear speakers. So are there any general rules of thumb to increase the decibel levels per foot? Should I just leave it at its neutral position? The rear speakers are B&W DM 600 S3s and the front two are DM 602 S3s and my woofer is an ASW 600. I just want to get the most out of my current setup given its limitations.
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post #2 of 28 Old 08-24-2014, 03:53 PM
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Originally Posted by capillariancrest View Post
...So are there any general rules of thumb to increase the decibel levels per foot? ....
No, distance is about timing and not attenuation.

I glanced at the manual and it looks like you are confusing the default setting with minimum adjustment which is 3'. Page 21 says:

FRONT X.X meter* (Front speaker distance)
Initial setting: 3.0 meter (10 feet)
Lets you set the distance from your listening position to the front speakers (A). You can adjust from 1.0 meter to 7.0 meters (3 to 23 feet) in 0.1 meter (1 foot) steps.
If both front speakers are not placed an equal distance from your listening position, set the distance to the closest speaker.
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post #3 of 28 Old 08-24-2014, 04:05 PM
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http://www.sengpielaudio.com/calculator-distance.htm

3.1dB for the difference from 7 to 10 feet

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post #4 of 28 Old 08-24-2014, 05:10 PM
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William is correct, the distance settings in your AVR have nothing to do with the volume of the speakers at the Main Listening Position (MLP), they are there to time align the speakers - adding a delay to channels that are closer so the sound arrives a the MPL at same time.

The channel level settings (or channel trim settings) are there to adjust the volume levels to balance the system - you should be using a Sound Pressure Level meter (SPL) or an SPL app on your phone or tablet - the absolute calibrated volume at the MPL isn't important, only the difference between channels and most any SPL meter or app is accurate enough for determining differences.

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post #5 of 28 Old 08-24-2014, 05:12 PM - Thread Starter
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Thank you both for the the feedback.
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post #6 of 28 Old 08-24-2014, 05:19 PM
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Quote:
Originally Posted by RayDunzl View Post
http://www.sengpielaudio.com/calculator-distance.htm

3.1dB for the difference from 7 to 10 feet
That is not the problem he is asking about. He is not having trouble setting the levels. He can set his level but he can't get his distance set. The distance setting is about speaker timing and level adjustments can't correct this.
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post #7 of 28 Old 08-24-2014, 05:45 PM
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Oh, perhaps I misread this specific question:

"So are there any general rules of thumb to increase the decibel levels per foot?"

I'll be back later...


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post #8 of 28 Old 08-24-2014, 05:55 PM
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Quote:
Originally Posted by capillariancrest View Post
I have some rear speakers in my 5.1 setup that are 10 feet from the listening position. My front two speakers are 7 feet and the centre speaker is 6 feet away. My subwoofer is about 7 feet away. In my receiver settings I have set the distances to 7 feet for all of the speakers. However, I am unable to set the rear speakers to 10 feet unless I set the front two speakers to 10 feet. I know my set up is less than ideal, but that is how it has to be because of the layout of my house. There is a setting in my STR DA2000ES that allows me to increase the loudness of my rear speakers. So are there any general rules of thumb to increase the decibel levels per foot? Should I just leave it at its neutral position? The rear speakers are B&W DM 600 S3s and the front two are DM 602 S3s and my woofer is an ASW 600. I just want to get the most out of my current setup given its limitations.
There is no "dB per foot" attenuation. Rather it is known as "inverse square law" and is the distance between the ratio of 2 distances.

Basically this states that when you double the distance-you lose 6dB in level.

It is all relative.

The difference between 1' and 2' is 6dB. The difference between 100' and 200' is 6dB.

The formula for figuring the distance between 2 distances is D1/D2 logx20=dB.
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post #9 of 28 Old 08-24-2014, 07:30 PM
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I think 6 dB is for free-space? I think I have measured a bit less in a room where reflections get added to the direct sound. And line sources a bit less attenuation on-axis. In any event the OP may have been confused about the way the AVR distance calculation works, and as others noted amplitude won't compensate phase anyway.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #10 of 28 Old 08-24-2014, 07:39 PM - Thread Starter
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I am aware of inputting the speakers distances into the receiver. I suppose what I meant to say was that there is an option to balance the speaker volume accordingly. https://docs.sony.com/release/STRDA2000ES.pdf Scroll down to page 38. I've set my speakers to "small" I've disabled the equalizer. Disabled the phase linearlizing and the cross over frequecy is set to 100hz however the only options I am allowed to select are 60hz, 100hz, and 150hz. My subwoofer low pass filter is set to "out" and according to the manual, that should hand over the processing to the receiver. http://www.bowers-wilkins.com/Downlo...650_manual.pdf
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post #11 of 28 Old 08-25-2014, 02:38 AM
 
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Quote:
Originally Posted by DonH50 View Post
I think 6 dB is for free-space? I think I have measured a bit less in a room where reflections get added to the direct sound. And line sources a bit less attenuation on-axis. In any event the OP may have been confused about the way the AVR distance calculation works, and as others noted amplitude won't compensate phase anyway.
Room correction systems that include a mic have no reason to calculate attenuation by means of estimates and approximations when they can simply measure it.
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post #12 of 28 Old 08-25-2014, 11:11 AM
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I know that, and I know you know I know that, but a good reminder. I was really double-checking the attenuation number since it's been a few decades since that class...

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #13 of 28 Old 08-26-2014, 10:06 AM
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Quote:
Originally Posted by DonH50 View Post
I think 6 dB is for free-space? I think I have measured a bit less in a room where reflections get added to the direct sound. And line sources a bit less attenuation on-axis. In any event the OP may have been confused about the way the AVR distance calculation works, and as others noted amplitude won't compensate phase anyway.
Reflections do all sorts of weird things. Depending on the freq and the distance between the reflection path and the direct sound path, you can get addition (just a few dB) or complete cancellation.

This is of course distance and freq dependent.

Line sources ONLY has less attenuation WHEN they are LONG as compared to the wavelengths involved. Short "lines" are nothing but a marketing scheme.

And when you have a short line (even 8' tall considered kinda short), the "effect" of the line attenuation will vary with freq. The lower freq will fall off at 6dB while the upper freq will fall off at 3dB-making for different tonal balance at different seats. This is mainly a problem for larger seating areas than HT, but the same theory applies and people often don't realize how line arrays "work".

But marketing depts just tell what they "wish" the cabinets would act like. Let's forget all about those nasty lobes that are shooting out all over the place-let's just draw pretty pictures----------

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post #14 of 28 Old 08-26-2014, 10:24 AM
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Quote:
Originally Posted by capillariancrest View Post
I have some rear speakers in my 5.1 setup that are 10 feet from the listening position. My front two speakers are 7 feet and the centre speaker is 6 feet away. My subwoofer is about 7 feet away. In my receiver settings I have set the distances to 7 feet for all of the speakers. However, I am unable to set the rear speakers to 10 feet unless I set the front two speakers to 10 feet. I know my set up is less than ideal, but that is how it has to be because of the layout of my house. There is a setting in my STR DA2000ES that allows me to increase the loudness of my rear speakers. So are there any general rules of thumb to increase the decibel levels per foot? Should I just leave it at its neutral position? The rear speakers are B&W DM 600 S3s and the front two are DM 602 S3s and my woofer is an ASW 600. I just want to get the most out of my current setup given its limitations.
Other than that... is there an "audible" problem/defecit with a specific aspect of your system?
If so, provide that info and perhaps someone can throw out an easy suggestion to help out. Otherwise... all you may get are suggestions to re-engineer your system and also have contractors reconstruct your room.
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post #15 of 28 Old 08-26-2014, 10:37 AM
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Quote:
Originally Posted by Ivan Beaver View Post
Reflections do all sorts of weird things. Depending on the freq and the distance between the reflection path and the direct sound path, you can get addition (just a few dB) or complete cancellation.

This is of course distance and freq dependent.

Line sources ONLY has less attenuation WHEN they are LONG as compared to the wavelengths involved. Short "lines" are nothing but a marketing scheme.

And when you have a short line (even 8' tall considered kinda short), the "effect" of the line attenuation will vary with freq. The lower freq will fall off at 6dB while the upper freq will fall off at 3dB-making for different tonal balance at different seats. This is mainly a problem for larger seating areas than HT, but the same theory applies and people often don't realize how line arrays "work".

But marketing depts just tell what they "wish" the cabinets would act like. Let's forget all about those nasty lobes that are shooting out all over the place-let's just draw pretty pictures----------
Got it, that all matches my experience and fuzzy theory memories (vs. memories of fuzzy theories), including (especially) the marketing comments...

Thanks! - Don

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post #16 of 28 Old 08-27-2014, 10:16 AM
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Quote:
Originally Posted by capillariancrest View Post
I suppose what I meant to say was that there is an option to balance the speaker volume accordingly. https://docs.sony.com/release/STRDA2000ES.pdf Scroll down to page 38. I've set my speakers to "small" I've disabled the equalizer. Disabled the phase linearlizing and the cross over frequecy is set to 100hz however the only options I am allowed to select are 60hz, 100hz, and 150hz.
Since this AVR doesn't have automatic room correction, as you say, the channel volumes must be set manually (page 28 and 38) using an SPL meter or SPL meter app (or by ear but that isn't recommended):

Quote:
Adjust the speaker level and balance using the LEVEL menu so that the level of the test tone sounds the same from each speaker.
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Originally Posted by capillariancrest View Post
My subwoofer low pass filter is set to "out" and according to the manual, that should hand over the processing to the receiver.
Switching the subwoofer low pass crossover to "out" is correct, the AVR will do the low pass filtering to the sub output.

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post #17 of 28 Old 08-27-2014, 05:55 PM
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Originally Posted by DonH50 View Post
Got it, that all matches my experience and fuzzy theory memories (vs. memories of fuzzy theories), including (especially) the marketing comments...

Thanks! - Don
I see no case in which a "line array" would offer ANY advantage (other than in the looks department and for guys that want a "lying array"-for whatever reason) in a home theatre situation.

A well behaved single source of sound will offer better quality performance-without all the interference and strange lobes bouncing all over the place.
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post #18 of 28 Old 08-27-2014, 06:28 PM
 
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Quote:
Originally Posted by RayDunzl View Post
Oh, perhaps I misread this specific question:

"So are there any general rules of thumb to increase the decibel levels per foot?"
Yes, acoustic inverse square law applies
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Quote:
Originally Posted by Ivan Beaver View Post
I see no case in which a "line array" would offer ANY advantage (other than in the looks department and for guys that want a "lying array"-for whatever reason) in a home theatre situation.

A well behaved single source of sound will offer better quality performance-without all the interference and strange lobes bouncing all over the place.
Agreed!
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post #20 of 28 Old 08-28-2014, 07:30 AM
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Well, now I'm confused. I thought a line array's pattern, while lobed differently, would exhibit less interaction with nearby walls and ceilings? Meaning first reflections are less an issue for a line array (over the frequency range it is actually a line source, natch)? The merits of their dispersion pattern can be debated, but I wasn't expecting such strong condemnation of them. I have used line arrays in the past for sound reinforcement (pro sound work) to take advantage of their pattern. I am not sure what "better quality performance" means in this context. The transition from line to "regular" radiation pattern at LF is well-known but I am not sure it is a major drawback (I mean that explicitly; I am not sure). It does mean any reasonable line source for home use (and all the ones I have used for pro work) is not a line source at lower frequencies just due to physical (size) constraints.

Anyway, the OP is not using line sources, my comment was a side-note about dispersion patterns. Did not mean to wander off, sorry. - Don

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post #21 of 28 Old 08-28-2014, 10:21 AM
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Originally Posted by DonH50 View Post
Well, now I'm confused. I thought a line array's pattern, while lobed differently, would exhibit less interaction with nearby walls and ceilings? Meaning first reflections are less an issue for a line array (over the frequency range it is actually a line source, natch)? The merits of their dispersion pattern can be debated, but I wasn't expecting such strong condemnation of them. I have used line arrays in the past for sound reinforcement (pro sound work) to take advantage of their pattern. I am not sure what "better quality performance" means in this context. The transition from line to "regular" radiation pattern at LF is well-known but I am not sure it is a major drawback (I mean that explicitly; I am not sure). It does mean any reasonable line source for home use (and all the ones I have used for pro work) is not a line source at lower frequencies just due to physical (size) constraints.

Anyway, the OP is not using line sources, my comment was a side-note about dispersion patterns. Did not mean to wander off, sorry. - Don
A "line array" has no control over the horizontal pattern-they pretty much just "spray" everywhere-so you will have lots of interaction with the walls.

The ceiling depends on the size of the array-and to the freq at which it actually has a "pattern". In most "home" arrays-this is only for the top octave or two-due to the short length. And since those freq are easily dealt with (carpet on the floor) acoustical or absorptive ceiling tiles, it is of little issue.

The thing that uses of line arrays "like to forget" of "won't talk about" is all the lobing that goes on-(sometimes the sound coming off the rear of the speaker is just as loud as the front).

There are all sorts of "spurious lobes" shooting out everywhere-but the marketing departments want you to "believe" that the radiation pattern is like a soup can cut in half so that produces a nice pattern. But if you actually look at REAL MEASURED DATA that does not have a ton of smoothing applied to it-you will see all those lobes coming off.

And those lobes will produce all sorts of different reflection patterns-causing all sorts of issues.

Now-granted-some people "like" that sound (just like the Bose 901) in which the sound is reflected all over the room and it makes them feel more "involved" in the experience.

HOWEVER that false experience you are getting IS NOT what the producer planned. The material (be it music or a movie) was done in a room WITHOUT reflections. So to hear the way it was INTENDED, you need to have a system with as few reflections as possible.

Or else the speaker system and its interaction with the room is coloring the sound.

But different strokes for different folks.

I know a number of sound "engineers" that don't like a accurate sound system. They want a system that makes you hurt-like an icepick between the eyes type of thing. They think that is what a sound system should sound like. Whatever makes you happy----------------

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post #22 of 28 Old 08-28-2014, 11:39 AM
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OK, thank you. I was thinking a line array had a front and back lobe from the source (line drivers) but little output from the sides right at speaker, but not something I have a lot of experience with. A conventional driver sends sound all around, subject to the baffle of course. Learning things...

We agree on the impact of the room. I use planer speakers which do not have a true line array pattern, but I heavily treat my room (including killing the back wave, which for planer dynamic and ESL speakers is as large as the front wave as you say) so the ambience is from the recording, not the room. Lots of people like to hear the room; I do not, at least not in reproduction. Perhaps due to my work in the studio, but I've always felt taking the room out of the equation was best if you wanted to hear the recording and not the room. And of course a lot of people want a somewhat live room and feel the sound is dead in a treated room; to each his own. A live room is a step along the Bose path but heaven help you if you actually say that...

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post #23 of 28 Old 07-14-2015, 07:39 AM
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Doesn't a proper line array lose power over distance at a reduced rate compared to a normal loudspeaker or single driver ?

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post #24 of 28 Old 07-14-2015, 07:45 AM
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Quote:
Originally Posted by RayDunzl View Post
Oh, perhaps I misread this specific question:

"So are there any general rules of thumb to increase the decibel levels per foot?"
From what I read he asked that question because he didn't know what the purpose of the distance setting was, and as pointed out it has nothing to do with levels.

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post #25 of 28 Old 07-14-2015, 12:08 PM
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Originally Posted by Mfusick View Post
Doesn't a proper line array lose power over distance at a reduced rate compared to a normal loudspeaker or single driver ?
That depends!

I built a 6 foot tall 3-way vertical line array for my garage speakers (with subs) and my ears and SPL meter found the results. Basically, at a distance of 1 to 12 feet, the output was within "/- 2dB at that distance. At around 20 to 24 feet or so, the output only fell 3dB. At 45 feet the output was down another 6dB so it became a "point source". My MLP is around 11 feet from the things. I used pink noise which varied more than 1KHz test tones because frequency changes with distance also due to line length.

Be aware the woofers are 5", the mids are 3" and the tweeters are 10mm (0.4") Every driver is packed as tight as possible and the line length is 6 feet. 12 woofers, 20 mids, 48 tweeters crossing at 350Hz and 6KHz. The subs are crossed at 100Hz.

The reason I built the things was to learn how they worked (I learned) be aware of what problems they have (I REALLY learned) get even volume from my bench and in my work area (success!) be very efficient for high volumes without damage at BBQs (success) and to have something that when placed on 20" tall subwoofers, it would no give a lot of cement floor/smooth ceiling bounce in the garage (works)

In my BIASED opinion, they work as I designed them to as long as you have the ability to EQ the final results. The things by design have issues over 10KHz and need a boost in EQ to get it smooth. I learned that 48 tweeters that push 90dB or higher to 20KHz get blown away by 20 three inch midranges rated for 85dB. However, they are garage/party speakers and meet that need very well.

Would I want line arrays in my house for home theater? No, they do have that BIG sound but surround sound has many more channels and point source accuracy works better. It would be interesting to hear what happens when mixing a tall line array with Atmos--I don't think it would work well.

My home theater speakers are point source (surrounds are dipole since my room is not optimal) I compared my HT speakers in stereo against my line arrays in a room and prefer the HT speakers for imaging. I feel the larger than life sound stage of the line arrays (not curved) would create chaos with the center channel and the extra processing required would strain an AVR. Since they act different from point sources with SPL, it would create a chaotic sound field for HT in your house. Stereo in a garage is where they shine, not recommended for HT systems in a house.

Be aware the marketing folks are created a new line array religion--it does everything, for everyone, everywhere and is the future. The advertising claims they can be scaled with one box to 24 boxes so fit every need, every venue and every requirement. I figure they are good for poor acoustical environments with highly reflective floors/ceilings but are not your only option.

So in summation, they do have lower near field SPL drop off than point source but that depends on the line length (height) The major downside for HT use is I suspect imaging problems in smaller rooms--but, I could be (and usually) can be wrong.
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post #26 of 28 Old 07-14-2015, 01:46 PM
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In my room, with my speakers, the last time I walked around with an SPL meter... 19x14x9

The whole area was essentially the same intensity with pink, and would vary with standing waves with pure tones.

So my result for loss with distance was 'don't worry about it'.

YMMV

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post #27 of 28 Old 07-14-2015, 02:22 PM
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Originally Posted by RayDunzl View Post
So my result for loss with distance was 'don't worry about it'.
Calculated loss with distance assumes an anechoic environment, which for all practical intents and purposes means outdoors. Indoors losses are reduced due to boundary reflections, and in a typical home are insignificant.

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post #28 of 28 Old Today, 08:05 AM
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Lots of people like to hear the room; I do not, at least not in reproduction. Perhaps due to my work in the studio, but I've always felt taking the room out of the equation was best if you wanted to hear the recording and not the room. And of course a lot of people want a somewhat live room and feel the sound is dead in a treated room; to each his own. A live room is a step along the Bose path but heaven help you if you actually say that...
+1 on all that. It's an ever-controversial subject, especially with those who spent a lot of $$$ for speakers with allegedly superior radiation patterns.

I even mentioned the Bose path. Unfortunately, the heavens did not intervene to help me.
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