bass trap for outdoor rock speakers? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 08-16-2013, 08:42 PM - Thread Starter
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I hope someone will be able to help with this issue. I have installed 2 Boston Acoustics' Voyager RK8T2 Outdoor (Rock) speakers in my yard. I'm using a JBL 50W / channel amplifier. I connected a bluetooth adapter to the amp and I can play wirelessly from my phone or ipad - nice setup. The sound is awesome. I have the speakers in the corner of the backyard on either side of a gazebo pointing towards the yard. The problem I have is that in my yard the sound is great. BUT, . . . in my neighbors' yards (behind the speakers), all they hear is the booming bass (e.g. like hearing a high powered car stereo as the car passes by with the windows up - all you hear is the thud, thud, thud of the bass). I would like to keep peace in the neighborhood by somehow "trapping the bass" before it rattles my neighbor's house. The rock speaker has a 8" woofer and two 1" tweeters, with a published frequency response of 50Hz-20kHz (+/- 3 dB). Bass sounds good in my yard, but too loud in others' yards. The other houses are approximately 30-50' away from the speakers.

I have seen plans on the web for building a bass trap - 2' x 4' x 4" thick with Rockwool or Owens Corning 703 inside with cloth on the front and back. But, I don't think this would work well outside in the elements (rain, heat, wind, etc.). I have heard of some plans having mylar on the front and plywood on the back of the trap, which might help with adding some longevity to the trap's effective life - but does that hurt the efficacy of the trap? Can I put mylar on the front and back and try to seal it in? Any suggestions for builds that would make this work for outside?

Are there other designs that might work? e.g.:

1. build a short landscape (precast concrete bricks/blocks) wall behind the speaker (speaker is 18.5"W x 15"H x 13.5"D) to try to absorb some of the bass? How high/wide would I need?

2. put a piece of Lexan (1/4" plexiglass / polycarbonate) sheet behind the speaker? I could potentially bend the lexan into a 30 degree angle or connect 2 pieces to create a bend, to further block some of the sound or potentially tilt it down to reflect the bass sound into the ground. I'm concerned this would potentially ruin the sound in my yard.

3. build a short wood wall behind the rock speaker (I have extra wood from building the existing wood fence which has 5/4"x4" pickets that I could use to build a 3' x 3' or 2' x 3' (landscape) wall?

4. make some tube bass traps and place 1 or more behind the rock speaker to try to absorb some of the bass (e.g. saw plans using 10" construction cardboard tubes used for concrete forms, filled with sand)? How high/tall should they be? How many do I need?

I'm looking for something that would weather well outside. I think the treble and mids are audible but not as bothersome as the bass which is driving a particular neighbor crazy.

Thanks for any advise you can provide.

Rich
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post #2 of 5 Old 08-16-2013, 09:02 PM
 
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First off, stop cranking them up to Rock Concert levels. As for Bass traps outside, you will never find one. Really you are better to use a 70 volt Mono system, if you are using them for background music, while entertaining. If you want anything louder, suggest using headphones while you do yard work.
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post #3 of 5 Old 08-17-2013, 01:38 PM - Thread Starter
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I presume you state "As for Bass traps outside, you will never find one" because they don't work (as opposed to they can't be built).

I'll check out 70 volt mono system. The speakers are set up to utilize 70 volt operation, but I haven't researched it since it is working fine. Do you have a good web link to learn about 70 volt systems?

I guess I'll have to reduce the volume to background music levels - cheaper than moving to a remote area.

Thanks for the quick response.

Regards,
Rich
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post #4 of 5 Old 09-18-2015, 06:05 AM
 
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you can try posiiton bass traps around your rock speakers to isolate the sound or reposition your rock speakers to a corner if it really gets to boomy. For the bass traps i generally use CornerBlox Bass Traps - they are nice and cheap and easy to customize, although i'm not too sure whether they will last outdoors.

Regards
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post #5 of 5 Old 09-18-2015, 12:09 PM
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Trying to build a bass trap for an outdoor speaker might be the very definition of the phrase "an exercise in futility".
  • You might try investing in a graphic equalizer and attenuate the low frequency range. Or turn down the bass on your source device, pre-amp, or receiver. Beware, this can or will leave your music somewhat less satisfying.
  • You could move the speakers closer to you and reduce the volume.
  • You could reduce the volume.
But bass traps for out side aren't going to help. You can hear for yourself what the problem is. High frequency's are very directional. They drop off quickly and are pointed away from your neighbor; that's why he doesn't hear them. Bass frequency's are long wave length energy and omnidirectional. Containing them with a trap on the back side of the speaker does nothing for the rest of the dispersion area that radiates low frequency and this low frequency will still find its way to your neighbors ears.


I agree with one of the above posters, a mono feed for these types of speakers usually produce better results for over all sound quality outside, but a mono system will do nothing to control the bass output. Nor will a 70v system. While there are certain advantages to a 70v system, there doesn't seem to be any problem based on your question and description of your system that a 70v constant voltage system is going to improve or impact. I see no benefit in a 70v constant voltage system for you in your current configuration.


The basic advantage of a 70v constant voltage system is the ability to use multiple speakers over long distances for distributed audio. This is done by using a step-up/step-down transformer to minimize resistive power loss. The other benefit is you don't have to worry about impendence matching at the amplifier, it's more easy to provide the amplifier with a matching load; you don't have to worry about connecting multiple speakers wired series-parallel.


But back to your problem. Another possible solution for you is to install some additional speakers, distribute the sound if you will, so that when you move around you maintain a comfortable listening level at a lower overall volume. If you were to do something like this, then a 70v system might have some advantages.


If you go with a 70v system, it sounds like your current speakers already have a transformer installed. You will need a transformer for your amplifier or buy an amplifier that supports 70v systems. I would recommend a multi-zone amplifier that supports either or 70v and low-z as well as individual channel gain controls.


Here's some links to give you some background information for 70v constant voltage systems:
http://www.rane.com/note136.html
http://www.crownaudio.com/en/constant-voltage


EDIT: I took a look at the Boston Acoustics site and the speakers you reference. Looks like 70v operation is an option but you need to buy the transformer form Boston Acoustics for this to work.

Last edited by b curry; 09-18-2015 at 02:08 PM.
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