[156546]

Enclosures have two purposes:

1. Isolating the front of the speaker from the back of the speaker to prevent cancellation at low frequencies
2. Modifying the suspension of the speaker to achieve some target Q

The suspension operates mostly below resonance. At resonance, nothing is very good at controlling the motion of the moving mass (that's what resonance is) and above resonance, the motor controls the motion.

So, the box affects the speaker around resonance, but that resonance is Fc rather than Fs. There is no Fs for a speaker in a box.

So, if you're going to use a high pass filter, you should cross above resonance to minimize distortion. If you're going to follow this basic rule, then the box makes sense ONLY if you need it for purpose #1 above. If you don't need it for that, then it's better NOT to have an enclosure, because Fs is always lower than Fc.

 

[156546]

So open back of a A Pillar build does sort out your Point #1? Therefore you don’t need an enclosure?

Sometimes we try to build an enclosure but because the driver actually needs a much bigger enclosure than what can be achieved the net result is that your actually limiting the drivers ability to play close to the FS therefore it’s better to build an IB install and make sure it’s sealed from the backwaves ( as per point #1)

Is this this correct?

I am gonna start my build in the next month so this is something I have been thinking about - I think if I model the Focal Utopia 3.5mm the box would end up being unreasonable so IB may be better?


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Yes. So long as the baffle is sufficient. Putting a midrange in a box that's way too small is not a great idea because it dramatically raises Fc and also Qtc. If you're going to cross REALLY high, then it doesn't matter. That's rarely the case, though, because people often think the bigger speaker is going to play lower and louder, so they cross LOWER and wind up with a lot of ****ty distortion, no low frequency and a massive peak.