Sealed vs Ported Sub

[Deleted member 48726]

The sub is tuned to 30Hz, so when it equalizes so that the sealed sub has the same response as the ported one, it should inject more than 4dBs of power (2.5x) between 20~30Hz. The third harmonic will be at 90Hz, coloring the bass. Just a thought...

Oh! You didn't write anything about EQ in your other post. And even if you wanted to pull the now sealed response upwards akin to the ported you don't automatically get more distortion you just get decreased headroom and SPL and the distortion will set in at lower SPL than before.

 

[arichman]

I have a pair of Monolith M12 v2 subwoofers in a small room (16x13). These are ported, but come with foam plugs installed. I expected that the ported configuration might overwhelm the room, and that appears the case. There is a peak at 20 hz that I cannot tame. Using a Minidsp Flex and calibrated (Umik) microphone, EQ was ineffective, with even large cuts having little effect. Installing the plugs yielded a much more acceptable result, both objectively and subjectively. In this case a peak at about 50 hz was easily tamed using EQ, yielding a nicely flat response down to 10 hz. Unfortunately, I could now hear a noise that was easily located to both subs. It was a low rattle that I attributed to air leaking from the ports (that put in its appearance just after the WB logo in Blade Runner 2049). Do I just need to use better plugs, and if so, what have you used? And while I'm asking questions, why could I not cut my way to a flat response with the open ports?

 

[Keith_W]

And while I'm asking questions, why could I not cut my way to a flat response with the open ports?

That is what I would like to know! Maybe start another thread with your measurements and with a detailed explanation of what you did.

That rattling is going to be something loose in your sub. Or maybe your room. It can be a real pain to track down. Good luck!

 

[arichman]

Using the term "rattle" to describe the sound does invite the idea that something is loose, but I very much doubt that is the case. Both subs exhibit the noise. It is probably better described as reminiscent of the sound a balloon makes when it deflates, in other words slightly flatulent. The timing of the noise is just after a very loud, deep sound presumably when there is maximal pressure. Removing the plugs causes the sound to vanish.

 

[Keith_W]

Using the term "rattle" to describe the sound does invite the idea that something is loose, but I very much doubt that is the case. Both subs exhibit the noise. It is probably better described as reminiscent of the sound a balloon makes when it deflates, in other words slightly flatulent. The timing of the noise is just after a very loud, deep sound presumably when there is maximal pressure. Removing the plugs causes the sound to vanish.

The term you are looking for is "chuffing". Check if your foam plug completely seals the port. If it is loose in any way, air can escape around the plug and create that sound.

 

[Flaesh]

Removing the plugs causes the sound to vanish

Try plugging the ports tightly. With something. I once had a missing 1/4" screw hole that was farting in my speaker.

 

[Chrispy]

That is what I would like to know! Maybe start another thread with your measurements and with a detailed explanation of what you did.

That rattling is going to be something loose in your sub. Or maybe your room. It can be a real pain to track down. Good luck!

And include measurements of with and without port plugs....

 

[Chrispy]

And as far as plugs were preinstalled, was that a specific request to Monolith? Or just packaging?

 

[arichman]

And as far as plugs were preinstalled, was that a specific request to Monolith? Or just packaging?

Not a specific request, but the company literature makes clear they're not just for packaging, and two thorough reviews of this subwoofer (this site and Audioholics) evaluate the performance of this sub both ported and sealed.

 

[Chrispy]

Not a specific request, but the company literature makes clear they're not just for packaging, and two thorough reviews of this subwoofer (this site and Audioholics) evaluate the performance of this sub both ported and sealed.

What thorough reviews would those be? Link 'em....

 

[arichman]

What thorough reviews would those be? Link 'em....

Erin's review:

Monoprice Monolith 10, 12 and 15-inch Subwoofer Review

Info: I just wrapped up my review of the following Monoprice Monolith 10/12/15-inch subwoofers: Monolith by Monoprice 10in THX Select Certified 500-Watt Powered Subwoofer - $499 Monolith by Monoprice 12in THX Ultra Certified 500-Watt Powered Subwoofer - $799 Monolith by Monoprice 15in THX Ultra...

www.audiosciencereview.com

Audioholics:

Monoprice Monolith 10” THX Select and 12” THX Ultra Subwoofers Review

In this review, we look at two high-powered but affordable Monoprice subwoofers, the 10" THX Select and 12" THX Ultra. Continue reading to find out if your home theater room can handle these beasts.

www.audioholics.com

 

[arichman]

To show willing, here are a couple figures attempting to capture what I described in my initial post.

The first figure shows the behavior of the system including the two subwoofers before and after EQ (ports plugged). A single cut at 60 hz was applied to each sub. The effect on the overall system is shown.

The second figure shows the behavior of the system with ports open. For simplicity the behavior of one sub only is shown before and after EQ. The behavior of the system after EQ is also shown.

The ported system doesn’t look as good, and also doesn’t sound as good. As I noted previously, it was much more difficult to EQ the ported subs. Large cuts made on either side of an apparent null succeeded mostly in just lowering the overall output of the system. The subjective result after EQ was thrilling in a sort of horrifying “are things going to fly off the wall” sort of way, lots of things around the room were vibrating and buzzing.

I heard none of that with the ports plugged. So again, objectively and subjectively superior.

 

[arichman]

Having sung the praises of the sealed (ports plugged) subwoofers in my room, I would like to return the focus to the fly in the ointment, that noise that is only evident when the ports are plugged and can be heard coming from both subs. The timing of the sound coming immediately after a loud, very low sound (the intro to Bladerunner 2049) made me think it was an air leak. However, the (company supplied) plugs are very snug. I placed the plugs in ziplock bags which appeared to provide an even better seal around the circumference of the port. It made no difference. The sound does not appear to be coming from the ports but the woofer cone. The bolts are not loose. It doesn't sound like an air leak, I'm going to call it a mechanical sound, the normal working of the woofer perhaps only louder. There is only one point in the intro of Bladerunner 2049 (which is clearly designed to blow up people's systems) where the sound is evident, it affects both subs, maybe it is (sad to say) "normal"?

 

[Keith_W]

Well, that's the third different sound you have described. First you said it's a rattle. Then you said it's like flatulence. This sound you are describing sounds like the cone is hitting its excursion limits, probably at its resonant frequency Fs. It's a "flappy" kind of sound. That's not what I would expect with the ports plugged, I would have thought that you would be more likely to hear it with the ports open. We need some input from someone who knows more about subwoofers, like @sigbergaudio.

And BTW I am familiar with that Blade Runner track you are talking about, it's the first track "2049" if i'm not mistaken. It uncovers rattles in my house like nothing else. I don't hear those rattles with normal music, so I don't care too much about it.

 

[arichman]

Well, that's the third different sound you have described. First you said it's a rattle. Then you said it's like flatulence.

I prefer to call them successive approximations to the truth.

 

[sigbergaudio]

@Keith_W @arichman It sounds like the driver is bottoming out. So it's being pushed beyond its limits. Which isn't so surprising when you plug the port and force the driver to do all the work by itself.

 

[ernestcarl]

What is the sub's HPF? Try increasing it... this let me push out maybe 4-5 dB more above 40Hz or so minus any "bottoming" noises when I was experimented with my sealed 12" sub.

 

[arichman]

@Keith_W @arichman It sounds like the driver is bottoming out. So it's being pushed beyond its limits. Which isn't so surprising when you plug the port and force the driver to do all the work by itself.

Thanks for that, guess I'll have to get out my whip and chair to tackle the ported beast(s)!

 

[arichman]

What is the sub's HPF? Try increasing it... this let me push out maybe 4-5 dB more above 40Hz or so minus any "bottoming" noises when I was experimented with my sealed 12" sub.

I have tried as high as 20 hz, with no effect on the problem.

 

[ernestcarl]

I have tried as high as 20 hz, with no effect on the problem.

How about trying higher... like 25Hz or more. And if it's 12dB/oct make it 18 or 24db/oct.