High room ceilings

[Charles Turner]

Help...I've always listened to my Cornwalls in rooms with 8' ceilings and I recently moved them into a room with a 13' ceiling and they sounded very thin. Both rooms are approximately 12' x 15', carpeted, one window, and one doorway. In both cases the Cornwalls are located in corners on the 12' wall and the listening position is centered approximately 13' away.

Has anyone had experience with Cornwalls in rooms with high ceilings?

thanks

[lynnm]

You might find that placing the Cornwalls along a sidewall will give a more satisfactory soundstage. In my case I started with a pair of KLF30's placed in the corners and the bass was astounding but I later moved them onto a side wall and found that although I sacrificed some bass response - the overall sonic balance improved and the improvement in the midrange and upper end,(a lack of midrange blare and a huge improvement in the overall naturalness in the soundstage),is such that I would not ever again place the speakers in the corners of the room.

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It is meet to recall that the Great Green Heron rarely flies upside down in the moonlight - (Foo Ling ca. 1304 BCE)

[WMcD]

I don't think that you're imagining anything.

Speaker response is very much affected by the room.

There were some eye opening graphs in the AES article on the Jubilee and K-Horn. In short, the bass response of the K-Horn has been measured as very good in a room, but it rolls off when placed in a corner, outdoors. Essentially, this is where three of the six walls of a room are missing.

Please note the outdoor corner is still acting as an extension of the bass horn, and would even "load" a direct radiator, as in the Cornwall. Room gain is a different issue.

This is probably also true of all speakers.

It is probably fair to say that all rooms have some bass gain. But where that gain is, frequency wise, depends on the dimensions of the room and is very complicated.

I suspect that a smaller room may have bass boost coming on at 70 Hz and below, where our speakers are rolling off, and everything works out well. On the other hand, a larger room may have bass boost coming on at 35 Hz and lower. Unfortunately, this fails to give a boost where it is needed.

Another suspicion of mine is that sort of thing could come into play comparing a LaScala to a K-Horn in the same room, both in a corner. The room boost could be at a relatively low frequency (say 50 Hz) where the K-Horn can exploit it because it has some output. However, the LaScala doesn't do as well because its response is way off.

On the other hand, if a room has a boost at 70 Hz, the K-Horn should sound a bit boomy, while the LaScala has picked up the gain at 70 Hz to make it sound very good.

Just some thoughts.

Gil

[Ray Garrison]

Charles,

Another point here is that your room is now 12 X 13 X 15. These dimensions are unconfortably close together, the room is almost cubelike. This is about the worst case scenario for forming standing waves in the bass range, with the attendent localized reinforcements and cancellations that happen.

Put on something with stong bass, and set your player up to continue to repeat the segment with this bass. If you have a test CD with different frequency tones in different bands, this would be ideal, otherwise if you have a recording with deep organ or synthesiser and you can set the player to repeat a particular note indefinately, start with that... anyway, get some bass playing, and WALK AROUND THE ROOM. I'm betting you'll find that there are certain places where there's bascially no bass whatsoever, and other locations where the bass is overblown and out of proportion. If this is true, then you can try moving the speakers around (which might not help all that much) or repositioning the listening chair(s) (which might help a lot) so that you're sitting in an area where you're getting the kind of bass you want.

In my room, moving the couch forward or back by less than a foot has a very significant impact on the deeper bass (I use an REL Storm sub to reinforce the bass of the my La Scalas).

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Music is art

Audio is engineering

Ray's Music System

[jdm56]

The top line is various room dimensons given by Mr. Turner. The columns below list resonant frequencies associated with those same dimensions. I only show modes up to 300hz as room resonance is not much of a factor above that.

8' 13' 12' 15'

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141hz 87hz 94hz 75hz

282hz 174hz 188hz 150hz

261hz 282hz 225hz

300hz

I don't think these dimensions are close enough together to cause problems. Modes are fairly well spaced. You should actually get more bass between 75 - 100hz with the high ceiling. I suspect you're getting some cancellation from the interaction, or combining of direct and reflected waves at the listening position.

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JDMcCall

CORRECTION: SORRY, BUT I SEEM TO HAVE LOST THE COLUMNS IN THE UPLOAD! EVERYTHING KIND OF COLLAPSED. THE "300HZ" SHOULD BE IN THE 4TH COLUMN.

This message has been edited by James D McCall on 11-20-2001 at 12:28 PM

[Ray Garrison]

JDMcCall,

The BBS software compresses spaces out when it uploads a post. If you try to put columns of numbers together, use an underscore or dot or something, force font to courior or other monospace font, and it'll line 'em up. Like this:

8'_____13'______12'_____ 15'

--------------------------------------------------

141hz___87hz_____94hz_____75hz

282hz__174hz____188hz____150hz

_______261hz____282hz____225hz

_________________________300hz

f>

(8 foot ceiling is no longer a factor - that was old room.)

Note that the first line shows nodes at frequencies of 75, 87 and 94 Hz - these correspond to wavelengths of 14.7 feet, 12.6 Ft and 11.7 feet, respectively, so within a 3 foot area (size of my couch cushion) you could have complete reinforcement, complete cancellation, or all sorts of in between possibilities within these frequencies, which are in the upper bass, right where a lot of movies and music, particularly rock, have significant content. I'd try some bass damping, see if that helps.

You can make a fairly effective, and perfectly ugly, temporary "Tube Trap®" by taking an empty cardboard box, 2 to 3 feet on a side, and stuffing it with crumpled up newspaper. Make two of these, put 'em in the corners behind the speakers, see what you think?

Ray

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Music is art

Audio is engineering

Ray's Music System

[fini]

I have cardboard boxes with crumpled newspaper in them all over the house. Also have kid's backpacks, unused speakers, dirty clothes, and misc. pets strewn about. Hmmm...I guess maybe I'll toss all that crap behind my speakers...might improve the sound. Everyones coming over for Thanksgiving, anyway. Kill two birds with one stone: clean up the house and tweek my system. Thanks, Ray!

fini

[jdm56]

Ray,

Thanks for the tip on uploading. I appreciate it.

But, I still disagree about the effect of the modal resonances in Charles' room (that's gratitude or ya').

Depending upon the reverberation time of his room, the bandwidth of those modes might range from 5-7hz to only 2hz. Supposedly, the "typical" recording studio modal bandwidth is about 5hz. I would assume the average home listening room is less well damped than the average studio, which would produce even narrower modal bandwidth; something in the 2-3hz range. BTW, the bandwidth is usually defined by the -3db points above and below peak resonance.

So, I would still argue that the weaker bass he is experiencing is due to either destructive cancellations or the lack of resonant "support" between app. 95 and 150hz, where a lot of "apparent" bass lives (actually, I guess you'd call it mid to upper bass).

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JDMcCall

[soundog]

Ray-

Neat way (maybe that's the wrong choice of words)to experiment cheaply with room treatments. Another cheap trick I learned re: room acoustics applies more to overly bright mids and highs. It creates a movable diffusion panel by stapling inverted egg cartons to a sheet of heavy cardboard or light plywood. This can be moved around the room usually starting with the point of first reflection (place on the wall that speakers are pointed at) (especially applicable to angled horns). Once these cheap experiments yield the desired results, one can purchase more aesthetic treatments or use decorative stuff such as bookcases loaded with books of different sizes (diffusion), drapes, carpeting, tapestries{sometimes covering foam panels (absorption). www.partsexpress.com has foam in cylinder, corner wedges, and other configurations that can be used as is or mounted in a frame surround covered with decorative material, etc. The listening room is a very important component that is often neglected. I think it is the reason why many will extol the virtues of speakers such as Klipschorns while others will claim they sound terrible. The only way I have found to "get it right" is to experiment with speaker placement and acoustic treatments.

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Soundog's HT Systems