Subwoofer shoot out series.

Designing speaker enclosures can be a tricky thing, with a ton of rules set we attempt to model 100's of different 18" speakers all in a unique enclosure.


The rules are simple, how small can we design a matching enclosure to achieve a -6dB response at 35Hz.

Sure it sounds super easy - nope it is actualy not so easy when going compact with many modern loudspeakers, if it was a large extended bass application it would 100%  be easier beyond any doubt.

Small enclosures can be a nightmare to try and get everything into layout, ports often are the nightmare factor being very long and secondly the vent velocity will plague us as we attempt to keep the port velocity under 16m/s.

Making used of high pass filtering we will attempt to keep the cone under control as we impact the overall response of the system as well as the vent velocity, something not considered by many people when designing and enclosure.


Design tips

When designing and modeling any speaker often new designers will look at the low end response as a primary choice in selecting a speaker, 100% cool way to go about things as we all love deep bass extensions regardless if we are building a subwoofer or a multi way design. Small speakers often have less con displacement vs the larger Pa or subwoofer orientated products & even though little speakers might have a great Fs to dig down deep but run short on cone displacement quickly.  This will change depending on the  box size and tuning frequency, here is an example of what we often will see when working with speakers:


8" driver

Power handling 300 watts

Xmax 5.5mm

FS 35hz


Just based on this alone we could assume a good little driver that should give us high levels of output at low frequency, right?

Well it's not uncommon the fall well short of 300 watts, maybe as low as 50 watts and our little cone is is exceeding Xmax - which means we are well into adding distortion and risk driver failure.


How do we fix this?

  • Adding a high pass filter

So when modeling any enclosure it is important Xmax can exceed the capacity of the system quickly, always consider controlling the overall extensions by limiting the response when designing an enclosure.

  • Consider how loud you really need to be when looking into specifications.

Power handling really often cant help you increase loudness, sensitivity might give you an advantage to gain back 5 or 6dB for the same level of cone displacement.

100dB is far louder than what you might realize so consider how much power you need to get to 95dB to 100dB, anything over 110dB starts to become earth bending, try get a reference to a real world level of loudness and keep in mind our pain threshold on bass is not as sensitivity as higher frequency. 110dB out at 1 to 4000hz can be run away material but at 60Hz a walk in the park. Try pop into a car audio competition and see if someone can let you listen to how loud 100dB actualy is, this could help you establish quickly how loud is loud.

  • Use a larger driver, more speaker area often means better bass.   

You might want to make a small 2 way speaker system using a 6 or an 8" woofer, consider using a 10 or a 12" as it can often be the difference between lights on vs lights off in bass response though it can present other challenges.


Anyhow enough of my babbling nonsense, here is part 1 of our multipart series.

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