Protip: Using a sub? Plug your mains

It all depends on what you want. I do not recommend filling the port or reducing the volume of your enclosure unless your speakers are poorly designed in the first place (or if they are designed to be optionally plugged).

Hey @kahlenz,

I think what few enough audiophiles understand is how much bass there can be from a pair of speakers once they are actually in a room, regardless of the specifications. We think we know based on the specs what is happening, but we don’t. Based on my experience as a speaker builder, and in-room measurements the advice I’m giving is solid, and best of all, easy to try and/or reverse.

This article I wrote may help some.

@erik_squires How does plugging the port keep the amp from trying to play down low? I don’t have any high or low pass filters in my system. I want to try your suggestion but can you explain why physically plugging the port will change the amp’s output? I realize it will change the outcome, but why would it change the out put?

Hi @hilde45 - I’m sorry if I mistyped but you are 100% correct. The amplifier’s output is a function of it’s input, for the most part. If you mean, why does dynamic range get improved, it is because the speaker’s excursion below the original tuning frequency is no longer as big. That means there’s more excursion left for the music above that Hz.

As you have guessed though, the amplifier's voltage swing for those notes remains the same.

Thank you for that, @strateahed - That's pretty innovative of you, I'd not have thought to only do one or the other but it makes sense.

Glad you were able to get what you wanted out of your system now. :)

Also, therefore, lastely and soforth:

This is a tip that is easy to try and reverse too. :)  Try it and listen.  No good, no damage.

One thing worth clarifying: Not all drivers will work well ported, but all drivers will work sealed. Yes, this is no longer "as intended" by the designer, but that doesn’t mean this isn’t a better match with a sub.

You are playing with the bass response here. You raise the -3 dB and make a gentler slope.  You are not making the "ideal" sealed speaker.  There are differences.

Generally speaking, an "ideal" sealed speaker uses a smaller volume of air vs the ideal ported speaker, so if you just plug a ported speaker, without reducing the volume you end up with a speaker that is normally orveramped...  BUT!! ... in this case you are doing so specifically for a subwoofer, which means overdamped is fine.

@ditusa - Read the last paragraph of the article you quoted. It's pretty much what I'm saying, only the author of the article doesn't consider in his writing the benefits of a plug when using a sub and not a  line level filter. :)

It seems the high pass filter should be enough.  I have read that plugging ports can mess with the speaker performance intended by the designer.  Could plugging the ports affect frequencies above the intended level at which the mains cross over to the subs?  I guess the only way to know is to try it. 

@mitch - It is true that you can't just willy nilly pick to port or not, and the size of a cabinet to ensure optimal performance. In terms of the overall frequency response, you are only changing the lower part of the woofer's response.  The upper part is dominated by other factors.  The big benefit is reduction in distortion by minimizing excursion, an especially important thing in 2-way designs as it can affect the clarity of the midrange a great deal.

The other big benefit is ths woofer will distort less at higher output.

A line level crossover, when significantly higer than the port tuning frequency, should be enough. :)

Hey @testpilot - So main speakers have their own natural rolloff and that a lot of audiophiles forego the use of, or can’t, put an electronic high pass filter in line with the main amplifier. As a result, the main speakers go pretty low and the bass can get messy. By plugging the port you raise the -3 dB point, letting the sub handle more bass.

The critical thing, for me is this: By plugging the ports you prevent excessive excursion below the port frequency, hopefully reducing distortion. This benefit exists whether or not you use an electronic high pass filter.

If you are using an electronic high pass filter this becomes less of an issue.  I'm doing a project soon I hope to better document why this work.  Stay tuned.  I have lots of solder and breadboards to go through. :)