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Optimum Low Bass for AR Classics Question


Aadams

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I know the optimum placement for Classic AR bookshelf models is flush in a sufficiently long wall or bookshelf where the wall acts as part of the baffle face but,

my question for anyone who knows the answer is:

What if the AR3a is turned toward the wall, off the floor, just inches away? Does that placement give the same optimum low bass performance as flush in the wall?

Disregard the impact on mids and highs, that is not part of this question.

Thanks for any help.

Aadams

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Interesting question. As you know, Allison made several models with top-firing woofers that were supposed to be mounted close to the ceiling. Sounds like you're looking for the same effect.

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Allison's AES paper covered many different locations.

There is also a program Best Place that should answer your question.

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/5186-allison-effect-and-bestplace-program/

Here is some discussion of Allison's AES work:

http://techtalk.parts-express.com/forum/tech-talk-forum/25007-boundary-effects-on-loudspeaker-power-and-frequency-response

Not sure if you can find them online in .pdf format, you can pay for them from the AES:

The Influence of Room Boundaries on Loudspeaker Power Output

Although it is well known that nearby boundaries affect the radiation angle (and thereby the power output) of small acoustic sources, loudspeaker systems generally have not been designed with due regard for these effects. Conventional loudspeakers oriented in typical use positions in living rooms exhibit variations of the order of 5 to 12 dB in low-frequency power output. The problem is examined quantitatively and some practical measures for improvement are suggested.

Author: Allison, Roy F.
Affiliation: Allison Acoustics Inc., Wayland, MA
AES Convention: 48 (May 1974) Paper Number: 951 Permalink 
Publication Date: May 1, 1974

You can search for all of Allison's papers at the AES site:   http://www.aes.org/e-lib/online/search.cfm

The green AES "Speaker Anthology" includes 3 of Allison's papers:  http://www.aes.org/publications/anthologies/downloads/jaes_loudspeaker-anthology-1.pdf

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Found it, see Figure 6 in this document:  http://www.troelsgravesen.dk/BOOKSHELF-1/RoyAllison.pdf

Figure 6 does not look very good unless you are using it as a subwoofer, note the much better response

in Figure 9.  Also note that infinite walls are assumed since the paper is about how the cone/box radiator

interacts with reflections from the wall boundaries - think of the walls as acoustical mirrors.   Room cavity

resonance modes are not treated and are a different subject.

Stumbled onto this interesting paper also:  http://www.mariobon.com/Articoli_storici_AES/Toole/Loudspeakers_and_Rooms_Working_Together_Toole.pdf

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1 hour ago, Pete B said:

Figure 6 does not look very good unless you are using it as a subwoofer,

Mr Pete

Thank you. I gave it a quick scan.  It seems relevant to my plan.  I will print and read.  BTW this is about a subwoofers, crossover frequencies and the floor bounce phenomenon.

Aadams

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Thank you Pete B.

12 hours ago, Pete B said:

Found it, see Figure 6 in this document

Read it and am certain to refer later.  Basically a clinic on how to use a classic AR 12" as a passive sub-woofer though that was not the original intent.  Exactly what I needed.  IMO it also sheds light on the AR quest for ever lower woofer crossovers in their premium systems.

 

Adams

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  • 2 weeks later...
On 1/9/2019 at 9:00 PM, Pete B said:

Found it, see Figure 6 in this document:  http://www.troelsgravesen.dk/BOOKSHELF-1/RoyAllison.pdf

Figure 6 does not look very good unless you are using it as a subwoofer, note the much better response

in Figure 9.  Also note that infinite walls are assumed since the paper is about how the cone/box radiator

Pete B.

This stuff works.  Allison was using a de-jumpered AR3a whereas I am using a 58s as a sub woofer crossed at 200hz with the base one foot off the floor.  Currently using Figure 7.  I tried Figure 6 but it does not seem as smooth.  I can't do figure 9 in this room.  I might invert the speaker cabinets and go back to figure 6. 

Thanks

Adams

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Back to Figure 6. The speakers have been inverted. The woofer centers  are raised 30" off the floor. Baffles are squared on the wall about 2 inches away.  The bass is a lot smoother.  This is a small room where bass resonances easily appear with standard speaker orientation. I Listened for about 3 hours after the cabinet orientation change.  So far not a hint of a problem.  I should add these AR58s are cut off at 200hz.

Adams

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I've always liked tall speaker stands.  Usually for smaller 2-way speakers.  But, because of the height, I invert the speakers, so the tweeter is at ear level.  Currently, I have my AR58S speakers inverted this way too.  They sound great in this configuration.  I guess I need to read a little more about Figure 6?

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On 1/9/2019 at 9:00 PM, Pete B said:

Found it, see Figure 6 in this document:  http://www.troelsgravesen.dk/BOOKSHELF-1/RoyAllison.pdf

Figure 6 does not look very good unless you are using it as a subwoofer, note the much better response

in Figure 9.  Also note that infinite walls are assumed since the paper is about how the cone/box radiator

interacts with reflections from the wall boundaries - think of the walls as acoustical mirrors.   Room cavity

resonance modes are not treated and are a different subject.

Stumbled onto this interesting paper also:  http://www.mariobon.com/Articoli_storici_AES/Toole/Loudspeakers_and_Rooms_Working_Together_Toole.pdf

I didn't read carefully when I referred you to Fig. 6 which is the case for only one boundary,

instead you should look at Fig. 15 that includes 3 boundaries.  Note that A and B have 

similar output below 100 Hz, but both C and D are about 3 dB lower across most of the band.

It shows the big advantage of using the corners when practical.  What the curves do not show

is the room's cavity resonances and it would be interesting to measure the room modes and

then use placement to deliberately dip the output to match the worst room mode.

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I tried Figure 7 placement with the 58s woofers at 30”. In this position the bass by comparison to figure 6 seemed to have a peak and punchiness I did not like and the low extension was a shade weaker, so I returned to Figure 6 which has no annoyances that I have perceived.  This room is only about 10 x11 x 8.

For me, in this application with the AR58, figures 6 and 7 give a nice smooth curve out to 200hz that equals the impractical Figure 9 placement at that frequency and is the point at which the 58s are low passed.  

Each of the multiple boundary placements using corners does seem to offer greater gain below 100hz with a fairly steep roll off above that point but I don’t have a corner to use and in this set up I prefer not to lower the woofer crossover point.

My goals were to get rid of dips and peaks as far a possible and gain low end extension if it was there to be had and get rid the of low resonances that have been a problem with conventional cabinet placements.

I will try this with 3a woofers in a month or two and see if there is difference.

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  • 1 month later...
On 1/22/2019 at 2:55 PM, Pete B said:

Stumbled onto this interesting paper also: 

PeteB

I finally finished the Toole paper.  No way I can absorb it in one read but his real world ,everything- is- a- compromise,  "pick your poison", approach to home sound issues is well argued and he even makes mild pitch for flat off axis response.     Thanks for pointing it out.

Adams

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Toole and Olive IIRC were both at the NRC in Canada.  The NRC is the facility that helped 

to make the Energy 22 , many PSB speakers and many others so good through the research

that they were doing there.  They were both very active publishing in the AES and Toole was a

past President of the AES.  Here is a brief bio on him:  from:  https://www.bloomberg.com/research/stocks/private/person.asp?personId=177919&privcapId=4277430&previousCapId=4277430&previousTitle=Harman-Kardon, Inc.

"Dr. Floyd E. Toole, Ph.D. serves as Acoustic Consultant of Harman-Kardon, Inc. Dr. Toole served as Vice President of Acoustics Engineering at Harman International Industries Inc. from November 1991 to 2007. In 1965, he joined the National Research Council of Canada, where he reached the position of Senior Research Officer in the Acoustics and Signal Processing Group. He worked with all Harman International companies, and directed the Harman Research and Development Group, a central resource for technology development and subjective measurements. Dr. Toole's research has focused on the acoustics and psychoacoustics of sound reproduction in small rooms. Most notably, he established methods for subjective and objective evaluations which have been used to clarify the relationships between technical measurements of audio equipment and listeners' perceptions. For papers on these subjects he has received two AES Publications Awards and the AES Silver Medal. A book, “Sound Reproduction”, for Focal Press (2008) is his most recent project. He is a Fellow and was President of the Audio Engineering Society and a Fellow of the Acoustical Society of America. He is active in teaching and course development in CEDIA and in 2008 he was awarded the CEDIA Lifetime Achievement Award. Dr. Toole studied electrical engineering at the University of New Brunswick and at the Imperial College of Science and Technology, University of London, where he received a Ph.D."

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I was going to post a video with Sean Olive but seems it was taken down at youtube.

Here is something on his blog:  http://seanolive.blogspot.com/2014/01/the-perception-and-measurement-of.html

This is the blog of what I was looking for but the video is gone:

http://seanolive.blogspot.com/2012/

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PeteB

Interesting article.   I have seen the Harman blind test info before. 

IMO and experience, linear sound is more easily achieved in a home environment with small speakers.  By that, I mean speakers that solidly extend to no lower than around 60 hz, are low distortion and inherently linear.    

There are a lot of candidates, most of which are two ways but, a three way, of which there are a few, would be better IMO but they are substantially more expensive. In the home environment, small speakers are easier to place, their restricted frequency range is inherently less colored and not nearly as problematic as the last octave of bass which will always be present in conventional full range front facing systems. If a listener really wants good flat bass, it is easier, to work out with a separate woofer system that can be optimally placed without too much concern for the speakers that create the stereo or multi-channel image. 

There are exceptions of course. I acknowledge the special case of the AR9 or AR3as mounted in a wall or a book case baffle in a sufficiently sized room.  But how many of those installations really exist in the world of home listening?

  I am beginning to realize the LST and 10pi approach were an improvement in bass control but the AR9 was the practical breakthrough for the home that was copied by ADS and perhaps others.  There have been many improvements since the 9. Good sound can now be achieved in a variety of ways but the day of the heavy, cumbersome full range speaker as the best or only full range home solution is gone.  I am happy with my ARs and content in knowing there is a way forward if they suddenly go up in smoke.

Toole, Allison and others have pointed the way using science and engineering.

Adams

 

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