Brax Midbass - Phase Plug?

JimmyDee · 2025-09-24T09:47:43-0400

I realize there is a new version of the Brax Midrange and Midbass speakers that will be released soon... but this question would apply to those new versions as well.

Assuming the midbass is mounted in the lower door of the vehicle (typical mounting location), and the tweeter is in the A-Pillar (on-axis), and the midrange is in the dash (off-axis - facing upwards toward the windshield). I am wondering which midbass would be more appropriate?

In the below Brax article, they state that:

The Dust Cap version optimizes the frequency response in the upper midrange area - which is good, because I'd be crossing it with a Brax 3.5" midrange that is located about 3 feet away (in the dash - facing upwards).
The Phase Plug version optimizes off-axis response and further reduces compression effects - which is also good, because I'd definitely be mounting these off-axis (in the typical lower door area).

And... because I know how this forum operates, and guys will throw-out answers like; "pick the phase plug because it looks cooler", I am wondering how do you technically measure or determine which one is more appropriate?

I am looking for a technical response / reason to pick one over the other.

I'm also not looking for responses like; "pick a GB60, because my buddy has them and they pound!", or: "pick and 8" because it has lower Fs".
My question is about 'phase plug vs dust cap', in general - but in this case, my speaker choice is Brax specific.

squiers007 · 2025-09-24T10:01:25-0400

The off axis response they are referring to the phase plug helping with would be in the upper mid-range frequencies where the driver is starting to beam (1.5-4khz). The phase plug helps act as a wave guide of sorts at these frequencies which can reduce comb filtering and destructive interference. Since you're using this in a 3-way setup the phase plug is offering little to no benefit since you'll likely be crossing somewhere in the 250-500hz.

PNWJohn · 2025-09-24T10:25:31-0400

I second this.

Joeyb1976 · 2025-09-24T10:10:05-0400

Your doors have sealed pods, correct? I am not fluent with Win ISD but it might be possible to model them there? That won't take into account any cabin borne reflections or gain but might point you in a general direction

JimmyDee · 2025-09-24T10:14:54-0400

This is for a future build / vehicle... the speakers would be mounted in a typical door cavity (no enclosure).

Rozay · 2025-09-24T11:24:03-0400

Jimmy Usually phase plug is for a 2 way and dust cap is for a 3 way. Call msc they should know the difference.

JimmyDee · 2025-09-24T11:34:23-0400

Rozay said:
Call msc they should know the difference.

I did... and they didn't.

JimmyDee · 2025-09-24T11:49:56-0400

Seems to be that the consensus is:

Phase plug is more beneficial in a 2-way, where the speaker is crossing at a higher frequency to match the tweeter.
Round dome is more beneficial in a 3-way, where the speaker is solely acting as a midbass driver.

LBaudio · 2025-09-24T12:11:35-0400

I would go with dust cap version for 3-way system and in case of 2-way system i would pick phase plug version.

try to ask AI, you might be surprised over answer

Rozay · 2025-09-24T12:19:36-0400

That’s exactly what I said

JimmyDee · 2025-09-24T12:23:00-0400

Gonna close this off now... I got the answer(s)

Brax Midbass - Phase Plug?

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