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Rear ported speakers and wall distance.
Soap
post Mar 24 2014, 21:15
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I've been looking for an inexpensive set of monitor speakers for use at my PC, and have (despite the lack of protective grills) been leaning towards the JBL LSR305. I do have a concern, though, about the rear port since the right speaker will be right up against (1") a plaster wall (the left speaker being 12" from the room corner.

Any advice on how I should proceed in this $300 (a pair) category is much appreciated.

Thanks

This post has been edited by Soap: Mar 24 2014, 21:23


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DVDdoug
post Mar 24 2014, 23:19
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QUOTE
, about the rear port since the right speaker will be right up against (1") a plaster wall
That seems a little too close.

The general recommendation with any monitor is to place them away from walls... For the rear port, I would think you'd need at least as much room for the air as the port area. (i.e. The surface area of an imaginary cylinder, with the same diameter as the port, between the port and the wall, should be no less than the port area.)

Scanning though the owner's manual online, they recommend speaker stands but I didn't see anything about how far from the walls they should be placed. (It does say that placing the optional subwoofer close to a wall or in a corner will boost the bass, but we already know that.)

Are these monitors for listening enjoyment, or for audio production? If you are doing production, it's more critical that you monitors are accurate.

This post has been edited by DVDdoug: Mar 24 2014, 23:22
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Soap
post Mar 24 2014, 23:30
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QUOTE (DVDdoug @ Mar 24 2014, 18:19) *
Are these monitors for listening enjoyment, or for audio production? If you are doing production, it's more critical that you monitors are accurate.


For enjoyment.

The more I read the more I suspect that anything "expecting" a close wall will be marketed as a "bookshelf" speaker.

I'm "simply" trying trying to find the flattest response I can afford, with those near walls.


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ktf
post Mar 25 2014, 08:30
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Maybe this is of any help: http://www.genelec.com/learning-center/pre...llcancellation/

Most Genelec speakers are rear-ported, so this should apply to rear-ported designs.


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Arnold B. Kruege...
post Mar 25 2014, 12:44
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QUOTE (Soap @ Mar 24 2014, 16:15) *
I've been looking for an inexpensive set of monitor speakers for use at my PC, and have (despite the lack of protective grills) been leaning towards the JBL LSR305. I do have a concern, though, about the rear port since the right speaker will be right up against (1") a plaster wall (the left speaker being 12" from the room corner.

Any advice on how I should proceed in this $300 (a pair) category is much appreciated.


The range of things that different things that happen to rear ported speakers when they are placed near a wall ranges from total blockage to no effect at all.

Total blockage turns the speaker into a sealed box in a box that is on the small side. Depending on the tuning of the box, the effects of blocking the port vary vary but they all relate to bass extension and prominence. The results of total blockage is sometimes considered to be a feature of the speaker for tuning it to its environment. Some speakers are shipped with user deployable port blocks.

An intermediate case is where the blockage of the port is not tight, and the volume that the port enters into is like an extension of the port. Again, the results vary with the tuning of the speaker and the nature of the external tightly coupled volume. If you have a speaker with a small (say 1.5") port and place it say an inch from the wall you are in one of these kinds of situations. The external volume rapidly increases in size as the sound exits from the speaker. The effect of this sort of thing is generally mild to undetectable.

The LSR305 appears to have a port that is maybe 3 inches in diameter. You are still in a situation where the effective port that is outside of the speaker is at least as large as the built-in port and rapidly increases in size. I don't expect a lot of problems.

As you move the speaker further and further away from the wall the effect of extending the port continues to decrease.
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