The Tactile Transducer FAQ v1.7

What is a Tactile Transducer?

What can I attach a Tactile Transducer to?
  1. Basically anything you want. It is a free country.
  2. Most people mount them to the floor, couch, chair, or the floorboard under the car seat.
  3. You could mount them to a vest that you wear like some failed product that a company tried to sell years ago. It was called the "AURA INTERACTOR" and it was advertised as "Virtual Reality Game Wear."
  4. If you mount it to a video game controller you would infringe on Nintendo's Rumble Pack patent and most likely get sued like Sony did. The story is that Nintendo purchased this patent from Atari.
  5. Or for the kinky, you could mount it to your bed.
  6. And for the truly insane you could mount it to a crash helmet you wear on your head.
  7. One company even recommends hot tubs and boats for "ultra sonic hull lubrication!"
  8. Another company suggests mounting it to a drum seat? Now why a drummer would want to feel his chair shake is unknown to me. Mixing the other musicians to headphones during a live performance makes sense, but being able to feel the vocalist sing with your butt is just plain bizarre.

I already have a fantastic subwoofer setup, why do I want tactile transducers?
  1. It gives you that big bass feeling at low SPL levels.
  2. Even at high SPL levels it adds that certain tactile sensation. It is a little something extra. You hear it and you feel it. You know, it reaches out and touches you.
  3. Play Telarc's 1812 and you will swear that the earth just moved. Now try that with your 2000W 18" servo sub by itself!

Will tactile transducers give me that ultra-low heavy pounding bass?

How do I wire up tactile transducers to the rest of my audio components?"
  1. Line level signal
  2. Amplification
  3. Physical

How much amplification do I need for powering my tactile transducers?

What is coupling and why is it important?

Do tactile transducers just buzz or do they create discernible and distinct notes?

What are the Problems with Tactile Transducers?
  1. Tactile Transducers are not very efficient. They crave power. 1W into a sub driver will create a lot more output than it will into a transducer. My tactile transducer amplifier is, without a doubt, the hardest working and hottest running amplifier in my system. It is very easy to overpower my 4 RBH transducers with a 150W amplifier.
  2. They require their own amplifier. Because of the serious mismatch in sensitivities, don't try to run them in parallel or in series with your subwoofer.
  3. The RBH and Aura/Alpines have very strong resonant peaks around 45Hz. Their frequency response is far from flat and I would NOT call this quality bass. Actually such peaky high Q bass has a certain slowness or delay effect with some music. This is unnerving. Serious EQ helps here (like a -24dB cut). This problem is at its worst with rhythmic music with heavy bass, movie special effects fare better. Parametric or graphic EQ is recommended.
  4. Transducers don't have the dynamic range of sub woofers. If max SPL is your game then transducers are not for you unless you're willing to mount 64 transducers under your seat and power them with around 3kW of juice. Yes, a little silly, and you still wouldn't get anything under 20Hz or near 150dB. This serious mismatch of dynamic range also causes problems with transients like explosions or punches. The subwoofers have no problem re-creating the impact, but the transducers will be hopelessly under powered and bottom-out creating an unpleasant sound. Solution? Turn down the volume.
  5. Low bass really isn't practical with todays tactile transducers despite manufacturers claims of a frequency response down to 5 - 15Hz. Just like subwoofers, this is a displacement limited problem and not a RMS wattage limited one. This is physics and there is no way around it. As the frequency gets lower you need to dramatically increase the Xmax excursion and/or the moving mass of the system. Think about it, all a transducer does is shake a mass. Either a bigger transducer or an array of a large number of smaller ones is needed if you want significant output at low sub sonic frequencies.
  6. I haven't done any accurate measurements of this but it seems that the RBH and Aura transducer ring a bit after a transient occurs. I believe the transducers are not critically damped or even highly damped oscillators on a spring. This most likely (by definition) is due to their high Q resonant nature. Since you feel and don't really hear the transducers this is not as serious of a problem as it would be with conventional drivers. EQ-ing, which effectively lowers the Q, helps this.
  7. I am concerned that I have noticed a spreading of energy in the frequency domain when a transducer reproduces a transient. On my spectrum analyzer it looks like a smearing of frequency. The same transient reproduced on a subwoofer looks sharper. This could be due to the springiness of the transducer and my couch are acting like a plate style reverb unit, think RT60 times, different modal resonances being excited, etc. This is one complicated set of equations. How much of a problem is this? Not much since the effect for the critical listener is impressive and pleasing. Tactile Transducers work, all I'm saying is that they might not hold up to the scrutiny of the audiophile crowd.

What are some of the misconceptions about Tactile Transducers?
  1. "That tactile transducers make no sound they just shake."
    This is not true. They make noise by shaking whatever they are attached to just like it was a speaker cone. You can measure the sound tactile transducers make with the Radio Shack SPL meter. This sounds like sound to me!
  2. "That tactile transducers can not replace a subwoofer."
    This is a common myth. Trust me, my transducers can shake the walls, the floors, the venetian blinds, pictures, even the dishes in the kitchen just like my subs can at high volumes. They might not make a great subwoofer, but properly equalized and at low volumes the effect is quite convincing. Experiments have been conducted and the conclusion of the A/B tests was listeners can be led to believe that a transducer is actually a subwoofer. One problem is once you leave the "sweet spot", I mean the couch, the effect quickly diminishes. So if pushed by space/spousal requirements, transducers can take the place of a subwoofer. But I highly recommend having both a sub and transducers.
  3. "Tactile transducers are great if you have thin walls or thin floors and you live right above your landlord."
    This again is not true. Unless you put the transducers in your couch and completely isolate it on a floating platform (like an optical table or concrete slab) then transducers are going to bother your neighbors more than subwoofers will. Why? Tactile Transducers have a direct coupling to the building's structure unlike subs which first transmit their energy to the air and then to the walls.

When I first got my transducers I cranked them up real loud, it was fun, now I am past that stage. How do I properly set the volume level of my tactile transducers?

Why is the calibration of tactile transducers important?

What is the difference between the Aura and the Clark tactile transducers?

Can I use a tactile transducer with a sub-harmonic synthesizer for even more bass?

Can I attach my tactile transducers to the surround channel output (line level) on my preamp?

I have a concrete slab floor in my listening room. Can I mount some tactile transducers to the floor?

How is the performance degraded when a couch with tactile transducers is moved from a suspended floor to a solid concrete slab?

Do tactile transducers get hot?

With tactile transducers, should I worry about the effects of vibrational damage?

The light bulbs in my house are constantly burning out. This didn't happen before I installed my tactile array. What can I do?

What is the Nintendo Rumble pack?

My tactile transducers just don't play loud enough. The clipping overload distortion sounds terrible, I need more shake. What can I do?
  1. Turn down the volume, this will increase your effective dynamic range.
  2. Buy more tactile transducers and amplifiers. Remember that doubling the number of transducers and doubling the amplifier power gives you +6dB of headroom in theory. An array is not a point source and in practice much less than +6dB gain for doubling will be realized, in some cases less than half that.
  3. Install a peak limiting device that will automatically reduce the gain to the amplifier before clipping / bottoming out occurs. A peak limiter will have to be calibrated by feeding it a test signal that clips and then setting the limiting level a little before that point. A low frequency in the 20Hz or so range is recommending as the calibrating signal because of the high excursion requirements.
  4. Install a HPF (high pass filter) or relax on the low frequency EQ boost. This concept is similar to the subsonic rumble filters some subwoofers have built in. Remember for a given SPL, low frequencies require more amplitude (excursion) than a higher frequency, so by over extending the low frequency response of your tactile transducers you are also reducing the system's headroom.

What are some tweaks I can perform with my tactile transducers?
  1. Most importantly is equalization. Either a 1/3 octave graphic or a parametric EQ and a spectrum analyzer (RTA) or SPL meter are required. The idea is to correct for peaky or non flat frequency response due to transducer design or the mechanical solid reverberation nature ("couch modes") of furniture. Think of it as a correct-the-couch transfer function!
  2. Digital delay line to correct the time alignment mismatch due to the subwoofers being several feet away and the speed of sound being close to 1 foot per millisecond. Some audio journalists feel that this is the most important tweak. I disagree. While important, time alignment on the order of 10ms manifests itself as a fattening of the sound and not an echo or delay (see Toole or Everest for the studies). I feel the audio journalists are mis-diagnosing the problem of slowness, and the problem they are hearing is really due to a fairly peaky or high Q frequency response. Room modes (standing waves) and sub woofers can cause this. This is why I feel equalization of tactile transducers is key.
  3. Compressor / Limiter has two purposes. One is to prevent clipping / bottoming out by peak limiting. The second is changing the gain curve from the ears logarithmic scale to the tactile senses linear scale. Not sure if this is experimentally valid, tests need to be done. Both of these uses reduce the dynamic range requirements that burden the tactile transducers.
  4. Sub harmonic synthesis is cool but not all that useful with tactile transducers. See previous question.
  5. Digital DSP or guitar effects boxes like chorus, flange, delay, reverb, fuzz, distortion, wah-wah, or harmony might be cool to play with, but they have little use if high fidelity sound from your transducers is the goal.

I keep hearing how good it is to equalize (EQ) tactile transducers. Now tell me why it might be a bad thing to do?

What is the hidden purpose of this FAQ?

I live on the second floor. Can I mount tactile transducers to the floor in order to modulate it?

Do the physical characteristics make a big difference in tactile transducer output level and frequency response?

What are some of the problems involved with tactile transducer arrays?

So in a tactile transducer array, is it best to wire the transducers up all in-phase or what?

How is the transient performance of tactile transducers?

Who invented or made the first tactile transducer?

Who claims to have the first tactile transducer patent?

Who makes Tactile Transducers?

What are the best tactile transducers to get?

There are some people on the net selling Aura Bass Shakers at low prices. What is up with this and are they any good?

What is the ultimate in tactile transducers?

I want to EQ my tactile transducers. How do I set the EQ?

What are the electro/mechanical specifications of some tactile transducers and how much do they cost?

What are some news groups that occasionally have tactile transducer discussions?

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Author : Erik Olson contact, copyright (c) SigBlips 2000.
Check out the Bass and its Greatness page for more data about bass and tactile transducers.