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In the Forum: Audio Discussions
In the Thread: Romy The Cat's new Listening Room
Post Subject: Helmhertz, Rotunda, bass, wasted weekend.Posted by Romy the Cat on: 5/10/2010
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 jessie.dazzle wrote:
Have you tried taking a measurement with the line arrays moved to the rear of the room? (ideally, he same as the current distance from the listening point, but behind you).
As I said I moved them everywhere.
 jessie.dazzle wrote:
If the measurements still show a strong 60Hz spike, you might as well get on with the construction of two new pairs of channels crossed as you have mentioned; mid-bass horns running down to the spike and lower-bass channels running up to the spike. Once this is done, the line arrays would be redundant, and that 60Hz spike may end up being your new best friend.
Yes, it is what I hope. Still, I do not want to commission any LF enclosure or midbass horns yet. My current arrays will do the LF enclosure duty perfectly fine and some kind temp direct radiator (Altec/Vitavox) will do fine temporary upper bass. I need to model the proper room response and THEN, only then to see if I need to build anything.
 Wojtek wrote:
splitting the bass arrays on more sections(I think its possible?) trying to get rid of resonances and counter the nulls. Surely you would loose efficiency of line arrays. Maybe not such a bright idea after all but it's what Earl Geddes advocates all the time.
Yes, I did tried it yesterday. It does not work effectively for the speakers of THIS size.
 Paul S wrote:
Then, rent some serious self-powered "subs" and run the numbers.  With w/w carpet and band-specific "treatments", it could take kW.
Hm, I forgot about it! I have Sunfire cube that is in a loan to a local audio guy. This think Sunfire will be perfect devise to play with instead of moving those heavy boxes.
 Albert wrote:
If you could tune the resonence of the Helmholtz resonator, moving the middle of the resonence up or down. it looks like it is at 63hz. Moving it down to 47hz or up to 75 or even 112 would smooth things out and help to avoid high order x/o. The question is how to tune it?
Albert, yeas you are correct. If it is the Helmholtz effect then it might be tunable to a degree. Helmholtz resonator is line changing the diameter of a bottle neck to get different impact to the air blowing across. I do not know if I get the Helmholtz effect. I will post better picture of the rotunda. The rotunda has windows and I might open them up, effectively changing the volume of the bottle. I think in Helmholtz a change the diameter of neck is more affective however… I am not certain that I have Helmhertz but the 63Hz bump is too stable, with respect of the location of LF source. So, I presume that it is the pattern between the listening position and rotunda. Surely I need to experiment more to be certain and to see how wide the margin of the listening positions would it be if it the Helmhertz.
 msaudio wrote:
Also i would be very interested to see the lowend response in free air, in the back yard from your right channel?
I did not try back yard response but I walked around the house and around the basement, chasing where the LF hot spots would be. There is none of the hot spots except … in the rotunda. Probably it would walk arond the house to do the same but I would not know how to interpret if I do find anything.

Rgs, Romy the Cat

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