Home > HT Soup to Nuts, Podcast > AV Rant #237: Static

AV Rant #237: Static

No topics and Tom’s side of the audio is staticy. Sorry about that. Liz found a book she wants to share. Tom has a projector issue – followup coming. What is there to be excited about in new product releases? Not much (check out Audioholics.com for some of the recent things Tom’s been unimpressed by). Liz tackles some irony. Soup to Nuts this week is about calibrating your speakers (check after the break for the details). Thanks for listening and don’t forget to vote for us at Podcast Alley! To see our (mostly) complete collection of show videos, click here. To get our iPhone app, visit the iTunes store. Download Tom’s ebook Bob Moore: No Hero which is pretty much available everywhere.

Audio Calibration Part 1:

  • Auto Calibration pretty reliable for speaker levels
  • SPL Meter to do it yourself (Tom says the digital one is fine)
  • Listen in for how to properly level match 2 subs
  • Crossover setting – 10 dB higher than the specified low point of your speaker
  • Don’t be afraid to run your speakers full range or to play with crossover
  • Auto Room Correction – Run it, test it, but don’t be afraid to turn it off
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  1. darthjason
    June 18th, 2011 at 14:52 | #1

    Kudos to Cambridge including the wireless dongle with the blu-ray player. However, the Oppo BD-93 does as well, I can assume the 95 does as well, but since that not the one I own… Both Oppo’s are still priced below! Also, a call out to Rob, I bought Auralex Gramma for my sub and it has made a difference. (Subdude too small for the Axiom EP500).

  2. Rob
    June 19th, 2011 at 01:23 | #2

    Woohoo! What a great week for me! darthjason gets a GRAMMA and discovers that I’m not just a crazy person (well, I might be crazy, but not about decoupling!), AND (and, and, and) Liz becomes my new favourite person by mentioning ‘So You Think You Can Dance’ and actually saying something GOOD about it!


    I have to say though, even I might suffer from some Dance overload soon. ‘So You Think You Can Dance Canada’ is starting next week already O_o That’s going to be A LOT of overlap this summer. Normally, the Canadian version only starts to run their audition episodes just as the American version is finishing up their season. Oh well, that’s what I have my DVR for! 😀

    Finally, no Wii U or PSVita talk? I defended the Wii, but even I have to admit that the Wii U looks pretty dumb. The PSVita looks pretty an’ all, but I foresee many problems. That touchpad on the back is just taunting you to accidentally brush your finger against it at the very worst moment, and I’m pretty sure the battery life is going to be horribly short. Plus, am I the only one who’d rather just see games with those kinds of graphics on my big screen coming from my PS3 instead?

    And just to wrap up my thoughts about what was announced at E3: the less said about Kinect the better.

    I am not a fan of where gaming seems to be heading 🙁 Hopefully we can eventually get away from all the gimmicks and just get back to simple input devices! (like…buttons…remember those?)

  3. Downtowner
    June 23rd, 2011 at 06:24 | #3

    Regarding Auralex products, would it make sense to use them to decouple a pair of floorstanding speakers and if so, why?

    What are the merits of decoupling vs the traditional audiophile practice of extreme coupling (floor spikes and lead shot in the bottom of the speakers).

  4. Downtowner
    June 23rd, 2011 at 09:06 | #4

    Has this website ever been discussed on the show?


    I lost it when I got to Brilliant Pebbles:

  5. Rob
    June 23rd, 2011 at 10:39 | #5


    I definitely recommend decoupling ALL speakers, regardless of size or placement. But with tower speakers in particular, an Auralex SubDude for each is certainly something that I recommend.

    The reason is because sound will travel through any medium that it can. In professional mixing and editing studios, the sound engineers and mixers sit close to their audio monitors, have those monitors posistioned on an elevated “bridge”, have the monitors aimed towards the mixing position and have the monitors decoupled from the bridge. The idea behind all of this is to ONLY hear the sound that is coming directly from the audio monitors and ONLY sound that is travelling through the air. The sound engineer or mixer does not want to hear reflections off of the surfaces of the room (hence heavy room treatments, the bridge separating the monitors from the mixing table, and the nearfield distance to the speakers).

    Technically speaking, any sound other than the direct sound from the speakers via air-borne transmission is distortion. Now, sound engineers and mixers are well aware that people do not listen in rooms that are set up like a professional recording studio. They are very concerned at all times with how well their final recordings will “translate” when played back on a wide variety of setups. But one of those setups is also headphones, where the sound is extremely direct.

    So basically, decoupling is all about eliminating a few sources of distortion and trying to get something a little bit closer to what was heard in the recording studio or what you would hear through a good pair of headphones. As I mentioned, sound will not only travel through the air, it will also travel through wood, metal, concrete, or any other material that your house is made of. Instead of air-borne sound transmission, you get structure-borne sound transmission. It’s akin to putting your ear down on a railroad track. You might not hear the train coming if you’re just standing up and only hearing the sound that is travelling through the air. But with your ear on the track, you can hear the sound vibrations that are carried by the metal, and that allows you to hear the train coming from miles and miles away. If the train were decoupled from the track (like a magnetic levitation design, for example) it would be a lot quieter. You wouldn’t hear the levitated train coming with your ear against the track. And when the train goes by, it would make a lot less noise since there are no vibrations being caused by the wheels rubbing against the track.

    Bottom line, decoupling is all about reducing vibrations. That stops sound from travelling via the physical structure of your house into other rooms, but it also lowers the distortion within your theater. The floor, ceiling and walls are no longer shaking in sympathy with the vibrations of your speakers. So that means fewer rattles, fewer sounds coming from the walls themselves, and fewer reflections and less interference when the vibrations of the walls are not contributing to the overall SPL in the room.

    As to the “spikes” and other methods of coupling speakers and subwoofers to the floor, the notion here is two-fold, but both are actually working against the intended goal.

    With “spikes” the notion is that much less surface area at the points of contact will lead to less transmission of sound energy into the floor. This is completely backwards, however. The vibrations and sound energy do not go away, they are now merely “focused” into those four tiny “feet”! It’s the old “bed of nails” analogy. Would you want to lie down on a bed of just four sharp nails? Or would you prefer to lie down on 10,000 nails? Obviously, you’d be more comfortable with your weight spread out over as many nails (as much surface area) as possible! The downward force of your weight doesn’t change, but the reactionary “upward” force at each point of contact can change a lot depending on how many nails are touching your back! With only four nails (or four “spike” feet), all of that downward force is divided onto a tiny surface area. So the nails “dig” into your back, maybe even puncture it! Exact same thing with “spike” feet.

    The second notion is that by coupling the speaker or subwoofer to the floor, you will make the speaker or subwoofer “inert” by essentially drastically increasing its mass. If the speaker/subwoofer is “joined” to the floor, you’re no longer just shaking the speaker/subwoofer, you’re now trying to move the entire house! And with that much mass, it should be nearly inert…right?

    Well unfortunately, that notion doesn’t consider resonance at all. It’s true that more energy is neaded to move a greater mass. But resonance can allow even a huge mass to “ring”. Also, sound isn’t like picking up the whole structure and moving it to a new location. Sound is “transmitted” via the structure – the individual molecules vibrating back and forth, not just moving in one direction to a new location.

    Building structures are anything but inert. So the notion of making your speakers or subwoofers inert by coupling them to the floor is completely backwards as well. You will get MORE rattles, MORE vibrations from the walls, ceiling and floor, and MORE interference and distortion.

    So decouple your speakers! We notice the effects of decoupling with bass frequencies more easily because the energy of low bass notes played at the same volume as higher frequencies is far greater than those higher frequencies. Also, bass notes will be closer to the resonant frequencies of the structural materials. But if you’ve got bookshelf speakers on stands, or on a table, you can almost certainly hear vibrations coming from the stands or the table itself. That’s why Auralex makes their MoPads, which are way over-priced IMO, but the idea is right 🙂

  6. Downtowner
    June 23rd, 2011 at 21:48 | #6

    Thanks, Rob – excellent information. Should become an AVR “sticky”!

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