Buttkicker LFE on my small riser underwhelming - AVS Forum
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Old 01-21-2013, 12:48 PM - Thread Starter
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I posted this in the construction forum before I realized that there is a Transducer forum. Posted here as well.

I mounted a buttkicker LFE Transducer (from a Buttkicker LFE kit) beneath a 4’ x 5.5’ riser. The riser is constructed of ¾” plywood glued and screwed to a base constructed from 2”x8” lumber. Because of seat mounting requirements, there are 8 2x8s in 4 feet so the riser is very stiff. The transducer is bolted directly thru the ¾” plywood (and thru a piece of 2x8 to stiffen the floor) about 1.5 feet from the rear of the riser, beneath the 2 old style folding theater seats. I used 4 of the rubber isolaters from the kit as feet for the riser. I estimate that the risers and seats weigh around 170 pounds. Pictures:




I have a similar transducer mounted to a loveseat of about the same weight as the riser with 6 K28 isolators. At first, I wired the 2 transducers in parallel to the bk amplifier. When I played a bass heavy movie scene (beginning of Serenity), I noticed that the transducer on the riser overloaded almost immediately and continuously (started rattling – hammering noise), while the one in the couch only rattled once (as it normally does during that scene).

My first thought was to replace the LFE kit isolators with 4 of the heavier K28s that I have. This made it quite a lot better, but it still goes from no shake to overload very quickly. In order to stop the rattling, the amp must be turned down so that I can feel very little shake for most of the movie – kind of defeats the purpose. Removing the feet completely (carpet) reduces shake but not overload.

Anyone have any recommendations that might help? Is it possible that the unit is defective? My next project will be to switch the transducers between the couch and riser to see if they behave similarly, but this requires two people and some effort. Would more power help? I am powering it with a crown 1500 amp. It is rated at 1050 watts at 8 ohms (bridged) – has to be higher for 4. I can switch to a buttkicker 1000, but the amps are difficult to reach at the moment. Would going with the much more expensive large isolaters ($15 each) help? I suppose that it would be possible to cut out parts of the 2x8s to lessen the stiffness of the riser, but that would be a last resort and rather permanent...

Thanks in advance!

bill
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Old 01-21-2013, 01:34 PM
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The problem is that the platform is not "suspended." The joists are the same dimension as the frame and they rest on the floor, which dampens the response. You want joists that are shorter than the frame so they don't hit the floor. That way the platform can move without being dampened by the contact with the floor. If you are using 2x8" outside frame boards, use either 2x4" or 2x6" joists. That way they won't contact the floor and they will allow the platform to move up and down. 2x4" joists will give more flex than 2x6" joists.

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Old 01-21-2013, 01:38 PM - Thread Starter
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The whole thing actually sits on rubber isolators, so they won't hit the floor, but the platform IS very rigid. I could cut down the "joists" if more flex is needed...
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Old 01-21-2013, 02:40 PM
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Yes, I would suggest using smaller joists. I was once on a platform made with 1/2" plywood and 1x2" "joists". That thing had more spring than an All-Star Wrestling mat. It was too much, but it was pretty cool. The joists in my riser are 2x4"s with a 2x6" frame. I get all the riser shaking I need. I use Crowson transducers which sake the seating directly, but the riser shakes too. Try smaller joists. I think that will help.

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Old 01-21-2013, 02:50 PM - Thread Starter
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Thanks Craig. I wanted stiff joists so that the chairs, which mount on a single leg, would not cause the riser to deform. I think that I overshot some. I am working with Marvin at Guitammer and am a little worried that he will eventually tell me the same thing. If it comes to that, I'll take a reciprocating saw after the joists and see what happens. I'll update with any progress.
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Old 01-21-2013, 03:04 PM
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Check out these plans for a platform from Earthquake sound: http://www.earthquakesound.com/pdf_pressreleases/Q10B_platform.pdf

They use a 1.25" thick piece of MDF with NO joists. I have also experienced a platform made like this and it is excellent. The key is finding the right amount of spring for the platform.

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Old 01-21-2013, 06:28 PM
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Originally Posted by craig john View Post

Check out these plans for a platform from Earthquake sound: http://www.earthquakesound.com/pdf_pressreleases/Q10B_platform.pdf

They use a 1.25" thick piece of MDF with NO joists. I have also experienced a platform made like this and it is excellent. The key is finding the right amount of spring for the platform.

Craig

Craig that riser looks intersting - a whopping 3 - 4"s tall - something I might consider...

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Old 01-21-2013, 07:51 PM
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i've had a buttkicker in my system for a whopping 48 hrs, so i'm a little gunshy about giving advise...

that said, my riser is 4'x8' with 2x8 frame and joists, tho my joists (2) run the short length of the riser...this framing is topped with a 4x8 pc of 3/4" plywood.

i used 4 of the RDB-220 rubber mounts, one on each corner of the riser...

after some fiddling i have the buttkicker 1000 amp's volume set between 9 and 10 'oclock. in the end this is one of the most enjoyable additions i've made to my setup!

i just watched a few chapters of "rise of the planet of the apes" and gotta say i'm thrilled...

i would try different mounting feet first...then if needed reduce the stiffness of your riser
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Old 01-21-2013, 11:19 PM
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OP..............that platform just looks way to stiff. You need to somehow loosen it up so it can flex. I am using a very simple platform similar to what Craig linked above with 6 of the kinetic rubber isolators and the flex/shake is excellent. Don't make it ANY stiffer than you have to.

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Old 01-22-2013, 06:38 AM - Thread Starter
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I agree that stiffness is a big issue. I experimented some with different amps and configurations last night; there are a few other things going on.

First, I don't think that the banana plugs were fitting into the speaker binding posts properly (my daughter plugged them in and didn't mention that they weren't snug). I switched to bare wire on the binding posts.

Second, power seems important rolleyes.gif . In order to use my crown amp, I have to crank up the output on the sub-out and max out the gain on the amp due to mismatched line levels. This works fine on the more flexible couch, but I think it leaves a little to be desired on the riser. The buttkicker amp better matches line level and gives more shake before overload. We are now getting a good amount of shake, but it still overloads more often on the the riser. I'm getting closer.

I like the idea of trying the heavier (and taller) feet. The current feet compress some and sink into the carpet so there isn't much space between the riser and the carpet. - I just wish they didn't cost more than the materials in a new riser...

Thanks guys! Really appreciate the input.

bill
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Old 02-01-2013, 09:51 AM - Thread Starter
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Has anyone tried mounting a BK transducer on its side? If I were to use soft isolators and mount the transducer on its side - thru a joist - would I get the desired result? The whole point of the transducer is to move up/down, it would just move the riser sideways. Seems like this would give the seats a pretty good shake...

bill
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Old 02-01-2013, 09:57 AM - Thread Starter
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Also, I heard back from Marvin at BK and he suggested:
1) Try adding another transducer. I can try this, but it takes some work to remove from the couch and install in the riser.
2) Try the larger isolators. I will try the 220s.
3) Make the platform less stiff. Still kind of a last resort - but if all else fails I will go to town with a reciprocating saw.

bill
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Old 02-01-2013, 11:15 AM
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i think you should work on the stiff platform first, with something so heavy and stiff, you are trying to shake the whole platform, with the seats and people on top

i don't think side mounting is recommended, and i personally would not try, i have 6 relabeled buttkicker concerts so i have some experience with these.

but i think you should add a 2nd one after you fix the platform stiffness
i have one buttkicker per recliner, i can pretty much shake myself silly.

i would get a few of these
http://www.markertek.com/Audio-Equipment/Speakers/Speaker-Cabinet-Components/Penn-Elcom-Inc/PENN-ELCOM-9106.xhtml

and put these in between the plywood and the 2x8's if possible. that way you are somewhat isolating it and only shaking the plywood with the chairs on top.
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Old 02-01-2013, 12:25 PM - Thread Starter
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The top of the riser is glued and screwed to the joists, so no joy on isolating just the top. Also, I don't think that the plywood is strong enough to hold the chairs.

Knowing that there is a lot of pressure applied to the rear of the riser due to the small mounting feet, how much joist should I cut out. The entire riser is made from 2x8s. For example, can I leave the outer joists whole? Cut the inside 2x8s down to 2x4s? It will have to be thicker by the chairs; the lags are 6 inches long. If I cut the outer joists, I have to be much more precise...

Since I will need isolating feet regardless of what I do, I just ordered 4 220s. I would like to get another transducer, but they are running $200 to $240 each now... only paid $100 each for the ones that I have.

bill
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Old 02-11-2013, 07:58 AM - Thread Starter
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So, the 220 feet have been installed. I would say that they made a marginal improvement over the smaller feet, but that could just be my brain trying to justify the $60. Next comes the reciprocating saw; with luck I will get good shake before I cause the collapse of the structure.

bill
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Old 02-12-2013, 09:03 AM
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Originally Posted by agmitch View Post

So, the 220 feet have been installed. I would say that they made a marginal improvement over the smaller feet, but that could just be my brain trying to justify the $60. Next comes the reciprocating saw; with luck I will get good shake before I cause the collapse of the structure.

bill

i hate to say it, the feet improvements were probably really just marginal at best.

the buttkickers are trying to move too much weight for it to work!
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Old 02-12-2013, 09:16 AM - Thread Starter
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Last night I watched Paranormal 4 with my daughter (even she thought it was bad) and we could hear the transducers at times. The movie had a loud low frequency hum during certain parts that caused both transducers to rattle while producing almost no shake. I had never heard this before. I'm thinking that this is the noise made by older transducers that others have referred to - it wasn't an overload, just a semi-quite rattle. The rattle was very distracting from the riser (no carpet to soften sound) and less so from the couch. I hope that this is just good reason to skip Paranormal 4. I don't relish having to turn off amplifiers during certain movies.

bill
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Old 02-12-2013, 12:32 PM
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Originally Posted by agmitch View Post

Last night I watched Paranormal 4 with my daughter (even she thought it was bad) and we could hear the transducers at times. The movie had a loud low frequency hum during certain parts that caused both transducers to rattle while producing almost no shake. I had never heard this before. I'm thinking that this is the noise made by older transducers that others have referred to - it wasn't an overload, just a semi-quite rattle. The rattle was very distracting from the riser (no carpet to soften sound) and less so from the couch. I hope that this is just good reason to skip Paranormal 4. I don't relish having to turn off amplifiers during certain movies.

bill

your low cut filter should be off
and high cut filter should be on, and set to somewhere between 45 and 50hz, this setting varies based on preference

is that what you have?

usually the rattles and hums are due to the high cut not being set right, and you hearing parts of the movie through the buttkickers.
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Old 02-12-2013, 01:09 PM
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usually the rattles and hums are due to the high cut not being set right, and you hearing parts of the movie through the buttkickers.

It could also be that your subs aren't playing low/loud enough to mask the sound. If you turned you subs off and listened to just the BK's you'll hear some mechanical noise, even when properly set up. But with the subs on, it's masked and you just get the effect. But if it's playing lower than your subs can go, you can potentially hear the noise, too.
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Old 02-12-2013, 01:39 PM
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It could also be that your subs aren't playing low/loud enough to mask the sound. If you turned you subs off and listened to just the BK's you'll hear some mechanical noise, even when properly set up. But with the subs on, it's masked and you just get the effect. But if it's playing lower than your subs can go, you can potentially hear the noise, too.

the only time i heard noise was when i had the high cut set wrong and it was passing on all the sounds from 80hz and down.

with my high cut set properly, i usually only feel it, i don't hear it. the speakers should be enough to mask any sounds coming from underneath you.

in the OP's case his is mounted under plywood. if you hear mechanical noises after proper high cut settings, then something is wrong with the buttkicker

i've had 6x buttkicker mini lfes, and 8x buttkicker concert(2ohm versions of the lfe) and have never heard mechanical noises, even when i accidentally cranked up the gain to the point i nearly got tossed off my chair.
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Old 02-12-2013, 03:54 PM
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the only time i heard noise was when i had the high cut set wrong and it was passing on all the sounds from 80hz and down.

with my high cut set properly, i usually only feel it, i don't hear it. the speakers should be enough to mask any sounds coming from underneath you.

in the OP's case his is mounted under plywood. if you hear mechanical noises after proper high cut settings, then something is wrong with the buttkicker

i've had 6x buttkicker mini lfes, and 8x buttkicker concert(2ohm versions of the lfe) and have never heard mechanical noises, even when i accidentally cranked up the gain to the point i nearly got tossed off my chair.

That's weird because all 3 I've experienced have had some kind of mechanical noise....brand new out the box, using the BK amp, with HPF engaged at 40. Many reviews of them say the same thing. And why wouldn't you at hear at least some noise? It's a piston moving back and forth inside a metal enclosure. I'm sure there's rubber on the interior, but that won't make it silent. When I helped my brother install his fresh out the box, you could hear some noise even holding it my hands, not attached to any hard surface. Your seating may dampen it, but it's there. Just the nature of the beast.
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Old 02-12-2013, 06:01 PM
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It could also be that your subs aren't playing low/loud enough to mask the sound. If you turned you subs off and listened to just the BK's you'll hear some mechanical noise, even when properly set up. But with the subs on, it's masked and you just get the effect. But if it's playing lower than your subs can go, you can potentially hear the noise, too.


you nailed it...at least in my experience

i can hear the BK LFE if the main volume is too low (if it's a bass heavy scene being in question)...

once the MV is adjusted to match the BK, it just produces a visceral effect that, once experienced, you don't want to be without...
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