Auralex - Subwoofer Isolation Platform

LL21

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Dec 26, 2010
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Anyone use the Auralex Gramma? It is an isolation platform used by bands, etc, and apparently you can use it for subs. I bought one to put under my sub...carpeting, wood and acoustic foam underneath.

I guess i tuned my sub to the room pretty well...while i do find the main speakers sound cleaner...i feel like i need to find a way to reboost the bass...ugghhhh...i hope turning up the volume on the sub will be enough, and i wont have to play around with all the settings....

any advice from people who have used these before? i live in an apartment and understood this might help isolate vibration from the floor (ergo, my downstairs neighbhors ceiling)...
 

kach22i

WBF Founding Member
Apr 21, 2010
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I know nothing Auralex Gramma.

I've built my own isolation platforms, basically MDF sand boxes with a caulked MDF lid floating on the sand.

I actually had too much energy being soaked up, fine tuned it by placing the rear speaker spike on a metal plate. I tried other materials as well, composite grinding disks, Corian and so forth.
 

LL21

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Dec 26, 2010
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Thanks. I run the sub 34hz in parallel with 48db rolloff (so as not to 'bleed' into mid-bass of main speakers. Would you be surprised if i told you:
- the mains seemed tighter with Auralex...in the midbass region
- the lower bass fell off a lot
- so i need to turn up the sub volume quite a bit, and i am still not convinced it blends as well as it did before
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
Sep 6, 2010
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Thanks. I run the sub 34hz in parallel with 48db rolloff (so as not to 'bleed' into mid-bass of main speakers. Would you be surprised if i told you:
- the mains seemed tighter with Auralex...in the midbass region
- the lower bass fell off a lot
- so i need to turn up the sub volume quite a bit, and i am still not convinced it blends as well as it did before

I would absolutely not be surprised. It looks like some attempt at a de-coupler. But depending on the weight of your sub, how it is designed, and the material of the foam "feet", it will couple at some frequencies and decouple at other frequencies and hence the effect on your sub can not be easily surmised.

See here: http://www.whatsbestforum.com/showt...ing-with-particular-reference-to-loudspeakers
 

LL21

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Dec 26, 2010
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Thanks, Gary!! The sub weights 120lbs and has aluminum hockey-puck like feet. Supposedly for good coupling. The Auralex is (from top down) carpet, wood platform, 2 rows of stiff foam for legs, acoustic 'egg carton' foam inbetween the legs.

at the moment, i am frustrated...the bass is too weak...
 

LL21

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Yes! But 2 subs are also 2x the price of 1...and take up 2x the space...;) ...when i get a bigger dedicated audio room! In the meantime, i have finished recalibrating the sub after it has been on the Auralex isolation platform...and bass is back to 'normal' again...except that i have picked up probably 10%-15% mid-bass clarity that was an unexpected and pleasant surprise. The music sounds very different now, and i like it as i feel like the mid bass up through mid registers has been 'freed up'.

on the re-calibration of the sub, I moved the crossover point a hair, increased the volume 2 notches, and moved the bass spectrum around a bit on the 'equalizer'. Seems to be properly dialed in again. will listen over the next day and see.
 

LL21

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Hi Steve,

Yes, i agree with you...its not easy to dial in a sub properly. To be fair, when if first got the sub years ago, it took a few days of listening to get something i thougth was alright, and then over several wks i kept refining and then i found the setting i like after about 3 months...the Auralex has made a change to the sub...but i dont think the change is nearly as drastic as taking the sub out of the crate for the first time.
 

LL21

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Dec 26, 2010
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Well, as STeve, said...not so easy...i totally revamped the sub setup last nite...ughh. after going one direction, i reversed engines and went entirely the other way on setup. Finally got back on track...once again, listening to various cds while i work...finally, much better...for now! ;)
 

Jeff Hedback

[Industry Expert]
Feb 9, 2011
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Hello Lloyd,

Nice to read of your improvements. I co-hold the patent for the Auralex GRAMMA and am the primary designer of the product (although I have no financial connection to the product or Auralex today). I developed the device to offer consistency of tone for my bass rig on the various types of stages I was performing on at the time. It (the GRAMMA and SubDude) have proven to have a life of their own beyond my original problem. I look forward to more comments and would be glad to answer any questions I can.
 

LL21

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Dec 26, 2010
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Hi Jeff,

So people understand the effect of the Gramma (in my room anyway),

i used to run the Velodyne DD18 in parallel with my Wilson X1/Grand Slamms. The volume is set once, and then the preamp drives it from there...the sub and the main speakers.
Settings:
- Volume at 8..out of 80 or something
- 34hz cutoff at 42db rolloff
- individual boost of 6db at 19-25hz
- no rolloff or cutoff below 20hz...natural down to 16hz or so

i put the Auralex underneath...and the mids and treble improved startlingly...i was not expecting this. i began to suspect that the wood on concrete floor was vibrating more from the sub than i knew...and 'bleeding' upwards into the spectrum. That is why i probably left it on 8...

I also found that the bass disappeared! A few hours a day and a few days later, and i think i've got it nailed. Here's the new settings:

- Cut off at 41hz, 48db rolloff
- Volume at 31!
- Cut off below 18hz at 38db rolloff
- no boost of any frequency range between 20hz and 44hz...pretty flat

Overall, the mids/treble balance remain clearer, cleaner than pre-Auralex Gramma, and the bass has definitely returned, but now much punchier, with greater snap and much better punch in the 35-45hz range. In a word, far superior on electronic...and whenplaying acoustic close miked material, it never bleeds or gets bloated. Overall an improvement across the spectrum and no downside.

Rather than try to describe the differences, i thought the description of the settings would say more than i could describe. now i just hope that having bought this originally to further dampen vibration for my neighbors...i have not made it worse by turning up volume! i think not, as the bass is same as before but much tighter...and the Auralex dampens the sub from the floor so no vibration. Plus with the punchy bass, i am happy to play music as low as 3 on my preamp!!!!! Because the sound is full bodied with a nice bass wallop with very wide dynamics even at these whisper soft levels. hope that is useful to someone.
 
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LL21

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Dec 26, 2010
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Hello Lloyd,

Nice to read of your improvements. I co-hold the patent for the Auralex GRAMMA and am the primary designer of the product (although I have no financial connection to the product or Auralex today). I developed the device to offer consistency of tone for my bass rig on the various types of stages I was performing on at the time. It (the GRAMMA and SubDude) have proven to have a life of their own beyond my original problem. I look forward to more comments and would be glad to answer any questions I can.

Hi Jeff,

Thanks for making such a great product! You will see above my experience, in particular, how much your isolation changed my original bass settings...and then how much better the bass (and the mids/lower treble) became as a result of getting it dialed in well.

Are you still designing acoustic products?
 

Jeff Hedback

[Industry Expert]
Feb 9, 2011
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Hello Lloyd,

...very rewarding words to read :)

In response to if I still design products, the short answer is yes. I have developed some pretty cool tools for mid/hi control. I like the combination sonically of real wood (or sometimes MDF) and absorption in "tuned" systems. I have a product I call the HAR Slat (Helmholtz Angled Reflector) that you can see in WBF member Ted Brady's room. If there is an existing device that will solve a problem...I use it. If not, I tend to try to solve that problem.
 

LL21

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Dec 26, 2010
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Sounds interesting...what does the HAR do exactly? how does one use it/adjust it?
 

Jeff Hedback

[Industry Expert]
Feb 9, 2011
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Hello Lloyd,

My HAR slat strategically reflects energy above ~4KHz, has a route through that is designed to combine with an absorption backing to absorb the heart of the midrange in a tuned manner (center freq ~1.5K) and can have additional absorption benefits to lower mid band (~300Hz) depending on spacing and absorption used. How does one use it...really I've not offered it for general consumption, only via design agreements. There are many options in how the device is put into a pattern or cluster. If I were asked to give a one word description of the benefit: "open".

I'll send Ted a note and he can offer more feedback.

I'm very thankful for this question. It's fun to respond to.
 

LL21

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Dec 26, 2010
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Look forward to hearing from Ted. Your device reflects (ie slightly enhances) energy above 4khz and absorbs energy in certain lower frequencies. What was the original purpose for doing this? I imagine you had some observations about speaker balances in real room settings for which the HAR would 'correct' too much midrange energy and insufficient treble dispersion?
 

Jeff Hedback

[Industry Expert]
Feb 9, 2011
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Indpls, IN
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That is very observant Lloyd. It is often the case that there is excess midrange decay and excessive lower mid resonance, and at the same time it is not natural to simply absorb all that energy. Diffusion covers a wide range of designs and results...sometimes though a specific QRD or PRD diffusor just hasn't been the right solution for a given case. The HAR slat developed to scatter that upper mid/hi energy (in non-specular manner). I've attached a pic of an application in dedicated Stereo & Surround listening room that was completed earlier this year. The pic is a cell pic before all the final tweaks...but you'll see 2'x4' panels with the HAR slats in 90 degree rotated patterns. In this case, the room has a high degree of acoustical bass trapping and the HAR slats were used to retain a natural feel in the room while controlling energy from all speakers including the "to be" Aether Audio fullrange surrounds.
 

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LL21

Well-Known Member
Dec 26, 2010
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Thanks, Jeff. Very interesting...I learned something. The tweeter/upper treble dispersion principle seems similar to what Wilson did with their X1 and X2 series speakers (main tweeter facing front plus 2 tweeters in back with slightly different db response)...to help disperse treble energy and give 'air' to the upper frequencies. Other speaker manufacturers have done comparable things.

Your HAR also does this but using a speaker's existing treble energy. Hence, why i suppose you use the term 'open', or others might say 'airy' to describe the effect. Very cool.

(BTW, I spy an Oppo remote control in the photo, if i am not mistaken?)
 

ted_b

Well-Known Member
Feb 4, 2011
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LLoyd, the custom HAR "cloud" and side panels in my room made the room go away. The openess in the overall feel of the music is wonderful. Steve Hoffman, recording engineer, calls it "the breath of life", that Marshall amp sizzle, or the awareness even when there are no notes played but you feel the room breathe with the presence of the microphones being on.

Here's my room:
http://www.whatsbestforum.com/showthread.php?2717-My-room-s-acoustic-makeover
 

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