Integrating Bass Shakers into Your Home Theatre

I was given Dayton Audio TT25-8 mini bass shakers as a present. They have excellent reviews online and they are small enough to fit within the seats of my high-tech reclining couch in the home theatre so I was pretty happy I had new toys to play with!

I wasn’t expecting much from them – and they certainly won’t compete with a butt kicker – but they do pack a punch for the size they are. They convey both more tactile and more rumbly sounds really well and after a while they are just part of the experience of watching a movie without being a distraction, which is really what you want. I would say it feels as if my dual SVS PB2000s had been swapped for the PB4000s as the couch feels like it’s being shaken by the bass coming out of the subs. It’s a lot of fun.

Here are some installation tips for those that want to do the same.

Mounting

Definitely get the mounting rings (either sold together or separately dependent on the package you buy) as the mounting ring makes the installation super easy onto a flat surface. It also gives stability to the unit so it won’t rattle.

I installed mine onto the wooden frame at the base of each reclining seat and this seems to work really well in transferring the energy into the seat, but you might need to experiment on the location.

Cabling and Amp

I have tried different gauge cables and 12AWG worked best in my case for a 5m run. I used a multi-channel amp I had lying around with about 50W per channel delivery and ran each off a separate amp (as opposed to writing them in series or in parallel). I prefer to run each off a separate amp so everyone can control the strength for their seat individually.

You can wire them in series or parallel but you need to be aware of the following:

Wiring in series will increase the ohm rating (so 8ohm TT25s will become 16ohm and will receive less power). Wiring in parallel means halving of the ohm rating to 4 ohms which works fine for wiring them to an amp two at a time. You can also get them in 16ohm versions if that fits better into your installation (and wanted to wire more than one in parallel).

Applying Crossover

These do need to be crossed over under 50-60Hz. Anything higher and they can get old pretty fast. Also, they will wear your amp down faster as they keep responding to more of the signal. I found around 55hz high-pass filter (with a MiniDSP) the best setting. However, in the end I settled on 60hz with a steeper roll-off.

Crossover settings I used:

  • Filter Type: Low Pass Filter BW 48dB per octave
  • Cut-off frequency: 60Hz (if you use a less steep filter, you may want to lower this to 50-55Hz.

Applying EQ

These do need to be EQ’d so best to pair them with a parametric EQ (such as a MiniDSP). Since 40hz is the resonant frequency, this means it needs to be EQ’d out, otherwise the box will sound like it is ready to self-destruct when a high-power 40hz note hits it.

If you have a different brand bass shaker / tactile inducer, you may need to refer to the specifications with regards to its resonant frequency and do some tests on how much this frequency needs to be EQ’d out.

The best way to EQ a bass shaker is to play a frequency sweep like the below and adjust the EQ until all frequencies vibrate to the same extent (without producing noise). The only exception is around 40hz (38hz to 42hz approx.) in the case of the TT25s where you should not get any shaking once EQ’d.

Here are the PEQs I used (in a MiniDSP unit) which might need some more refining but they work pretty well for now. You may need slightly different EQ settings dependent on the mounting position on your couch and how you use them. It is best to refine the below for your use using the above method.

ID FrequencydBQ
1 1016 1.1
233-72.7
340-1613.8
440-1611.2
540-750
64563.4

Once EQ’d, increase the volume / trim or level of your bass shakers until they produce just enough rumble without producing distracting noise. My favourite movies to do this with are the Transformer movies or Tron: Legacy, which has a lot of different types of tactile feedback as soon we we enter the digital world. It is important to put your master volume at the volume you normally listen at (or alternatively the maximum volume you are likely to listen at so you don’t need two different volume settings). Ensure that the bass shakers are fun but not distracting. They should feel like part of the subwoofers and therefore part of the movie.

Applying Delay

You need to apply delay to the bass shakers separately to the subwoofers. Since they are closer to your body, you need to delay them more (I know it sounds counter-intuitive but trust me!). You can use an audio delay calculator to work out how many milliseconds you need to add as a delay to the bass shakers dependent on how far you sit from the nearest subwoofer. Hence it is much better to use a separate DSP unit (such as a MiniDSP).

To further align the delay, put on music with a repeating low bass line and adjust the delay until the bass notes hit both from the sub and the bass shaker at the same time. I found this the best way to fine-tune the delay beyond the distance calculation, which doesn’t take into account electronic delay and the delay of the shake travelling up the couch.

MiniDSP Alternative

Dayton sells a Low Frequency DSP Controller unit as well, which looks like great value. However, reviews suggest that this unit is best used with an iPhone (or iPad) as the Android app does not have great reviews. I have not had any experience with this DSP unit so buy it at your own risk: some reviewers rated it well – while others not so kindly. However, it looks like a possible option if you are short on cash – and rich in patience.

BEQ and Bass Shakers

You may have heard of the BEQ project which aims to restore ultra-low-frequency content for movies that have had these filtered out during mastering. This seems to be more and more of an issue especially with Atmos mixes.

While I would NOT recommend you do this for your subs until everything is dialled in and you take safety precautions*, it is pretty safe to do for bass shakers – in fact can result in a much better “ride”, so it is worth looking into BEQ once you have EQ’d your shakers.

Enjoy!

*Safety precautions for your subs when using BEQ: using limiter / compressor as well as a HIGH PASS FILTER if you use ported sub(s) to roll everything off below the port tuning frequency of the sub(s). This stops the driver over-exerting itself as ported subs don’t have good control of the driver below the tuning frequency, especially when playing at reference level.

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