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svenr

Speaker placement for optimum sidewall reflection

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Geddes views support his own designs on constant directivity (hardly surprising), but even Toole says the approach only works where a speaker's off axis response is smooth (as Peter mentions above).

 
What are your views on Geddes' approach compared with Toole's?

 

IME experimenting with the DI of speakers in the same room/position .... it is extremely important.

 

I don't feel really confident to make any bold claims .... but constant directivity (with high DI) speakers work well in EGs type of setup  (speakers in corners with reverberant room).

 

 

... and I have found that the whole LE and direct/reflected balance issues work much less well, when a speaker has a poor off axis balance.....   and get better and better as we approach more textbook constant directivity.... especially in midrange frequencies where most typical speakers to not have much pattern control at all.

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even speakers with near-constant beam width are suboptimal off-axis, and really should be angled at the listener

 

Not all.   This is a cornerstone of Geddes (and others) approach.

 

 

[3] the geometric solution is far too strict for most people to apply, given the range of real listening rooms we encounter.

 

Yes  : )

Edited by davewantsmoore

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A Geddes speaker is made to be listened to on-axis. Its design axis is 22 degrees from perpendicular to the front panel. Listening to it off-axis (including perpendicular to the front panel) will be suboptimal. 

 

And therefore using the Geddes approach with anything other than a Geddes speaker or clone is suboptimal, too.

 

The direct sound quality is the primary thing to get right in speaker setup. Sacrificing that to get reflective soundstaging right is nose, face, spite.

Edited by Newman

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That's right ..... but when you have a speaker which not compromised off axis .... then you are able to set the speaker location and angle to effect the desired direct to reflected sound ratio in the room  (and deal with the issues Svern raised in the opening post).

 

The Gedes speakers are optimised for 22 degrees yes....  but as they (attampt to) approach constant directivity, you may use EQ to optimise them on some other listening axis  (which will again, modify the direct/reflected balance - and all those important issues from the OP)

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This is brilliant stuff svenr and others. Given I'll have to read it every time I am thinking of applying it but none the less excellent stuff...

 

@@sthpaul,

 

Don't stand up while listening to music as it then sounds horrible (trebbly and tunnel like). I have nearly an identical height ceiling and the room width/depth is very close also but it'smade from lammy panel and drywall!

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Thanks for the heads up bjc, bad pun intended. Do you have any acoustic treatment, or in line with this thread any specific speaker type and/or setup?

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I have 5 bags of Bradford Soundscreen R2.5 at the back of the room in the corners stack to the roof which I bought to go in the ceiling and main wall when I get around to fully building the room so I'm using them as bass traps which was my intention anyway. I haven't modelled the room room for modes but it is excellent for low frequency (I have 4 subs though) and because of the size seating location to all speakers is close so run easy to ear bleeding levels. It's more a HT room than music but I do sit here on my days off and listen to music allot which is what I'm doing right now!

As for speaker placement I have my floorstanders (Aaron ATS-5) 300mm from the side walls and only 150mm out from the front wall as my screen is 2960mm across (120in scope screen) which leaves 500mm either side of the screen so reason why the speakers are in the corners! I use memory foam and those cheap acoustic tiles behind the speakers just because I had the foam... The room is always a work in progress and testing as it will all change in the end (atleast in my head and dreams it will)...

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