Sealed versus Ported Bass, can the difference be measured?

[Paul McNeil]

They call dogs woofers for a reason.

Surely the loudspeaker's 'woofer' is named after the dog sound, not the other way around!

 

[Sokel]

I don't see display of the 'Step Response' as an obvious option in REW (V 5.31.2).

Hit the "Overlays" tab and it will open a window, it's there along with all other measurements.

 

[Paul McNeil]

Hit the "Overlays" tab and it will open a window, it's there along with all other measurements.

Thanks!

 

[Keith_W]

I don't see display of the 'Step Response' as an obvious option in REW (V 5.31.2). This seems to be crucial for me.

Under "Impulse" tab, click on "Step Response". In the drop down menu on the top left of the graph, choose "%" instead of "dBFS".

Also my display of 'Group Delay' looks very different from yours.

Click the "Overlays" button and choose the "GD" tab.

By the way, there possibly are the reflective concave surfaces you speak of in the room, largest (arrow) is in room fireplace made of tile and brick (I live in Poland) that is along the long wall of one subwoofer corner (see labeled arrow). Another closer to the sub in the corner is a record cupboard (star). Seating is about at the level of the in room fireplace,

I still have trouble visualizing it. Could you draw a diagram? When I say "concave surface", I mean a very large surface enough to concentrate long wavelengths like a lens. It has to be proportional to the wavelength.

In any case, like I pointed out earlier, we don't know if that late arriving peak is DSP related or room related. Understanding the room configuration might help, but the measurements I suggested would help more.

 

[Paul McNeil]

Under "Impulse" tab, click on "Step Response". In the drop down menu on the top left of the graph, choose "%" instead of "dBFS".



Click the "Overlays" button and choose the "GD" tab.



I still have trouble visualizing it. Could you draw a diagram? When I say "concave surface", I mean a very large surface enough to concentrate long wavelengths like a lens. It has to be proportional to the wavelength.

In any case, like I pointed out earlier, we don't know if that late arriving peak is DSP related or room related. Understanding the room configuration might help, but the measurements I suggested would help more.

Thanks again Keith_W., I'm all set with 'Overlays', the full(fool) monty of REW display now! I'll work on the diagram but this involves a physics 101 refresher course...

 

[Paul McNeil]

Under "Impulse" tab, click on "Step Response". In the drop down menu on the top left of the graph, choose "%" instead of "dBFS".



Click the "Overlays" button and choose the "GD" tab.



I still have trouble visualizing it. Could you draw a diagram? When I say "concave surface", I mean a very large surface enough to concentrate long wavelengths like a lens. It has to be proportional to the wavelength.

In any case, like I pointed out earlier, we don't know if that late arriving peak is DSP related or room related. Understanding the room configuration might help, but the measurements I suggested would help more.

Also, yes I agree measurements are the first step, just need to find a quiet time in the household. I think those two objects I pointed out are way too small to act as your hypothetical lens.

 

[Keith_W]

I'll work on the diagram but this involves a physics 101 refresher course...

Just take a piece of paper and do a rough sketch of your room. It's nothing complicated.

 

[Holmz]

Surely the loudspeaker's 'woofer' is named after the dog sound, not the other way around!

You’re p’rolly correct.
I suppose that the tweeters then might be named after birds.

 

[Paul McNeil]

Just take a piece of paper and do a rough sketch of your room. It's nothing complicated.

OK, let me know if this will do (PS Couldn't find any paper!).

 

[Paul McNeil]

You’re p’rolly correct.
I suppose that the tweeters then might be named after birds.

Yeah, I think we're onto something here!

 

[3ll3d00d]

sim won't be perfect due to room openings but it looks pretty close, even without entering the dimensions you can see that there are peaks and dips that are present and uncorrected over time and they seem to relate to your room dimensions (8m is roughly 20Hz mode so then there will be modes at 40/80 and so on)

those are also why your spectrogram looks all over the place

hard to say if that will be seriously audible, it's the sort of thing you may be able to fix with sub positioning if you have flexibility there

the ported response looks similar in those terms but with worse frequency response

rew can show you how the frequency response relates

 

[Keith_W]

OK, let me know if this will do (PS Couldn't find any paper!).

Where are the speakers? Which is the front wall? That's a pretty decent room BTW, great volume.

 

[Paul McNeil]

View attachment 462806

Where are the speakers? Which is the front wall? That's a pretty decent room BTW, great volume.

Whoops, L/R 1M Front wall (left side drawing, 1.5 M Side wall. Yeah, this is one room of a former one room German school house. I bought this house because of this room...

 

[Paul McNeil]

sim won't be perfect due to room openings but it looks pretty close, even without entering the dimensions you can see that there are peaks and dips that are present and uncorrected over time and they seem to relate to your room dimensions (8m is roughly 20Hz mode so then there will be modes at 40/80 and so on)

those are also why your spectrogram looks all over the place

hard to say if that will be seriously audible, it's the sort of thing you may be able to fix with sub positioning if you have flexibility there

the ported response looks similar in those terms but with worse frequency response

View attachment 462801 rew can show you how the frequency response relates

I can move the subs maybe a meter out from the corner location. "...your spectrogram looks all over the place...". Yet more bad news!

 

[3ll3d00d]

"...your spectrogram looks all over the place...". Yet more bad news!

tbf it's an offhand comment, your subs certainly have some issues which you can probably improve on but it's not a disaster (nor unusual)

 

[Keith_W]

I can move the subs maybe a meter out from the corner location. "...your spectrogram looks all over the place...". Yet more bad news!

Do not make any more changes to your configuration until you understand what is going on and what you need to do to fix it. What you have right now is your baseline. Take those individual measurements of speakers and subwoofers as I suggested and then decide what the appropriate intervention needs to be. If you start moving speakers, you will again be comparing apples to oranges.

 

[Paul McNeil]

Do not make any more changes to your configuration until you understand what is going on and what you need to do to fix it. What you have right now is your baseline. Take those individual measurements of speakers and subwoofers as I suggested and then decide what the appropriate intervention needs to be. If you start moving speakers, you will again be comparing apples to oranges.

Yeah, that's my plan. When I get some quiet time for those measurements. I did, feeling more confident (thanks Keith_W) with REW look at the room simulation. The result is intimidating and reminds me of the several comments above, basically 'it's the room'.

 

[Paul McNeil]

tbf it's an offhand comment, your subs certainly have some issues which you can probably improve on but it's not a disaster (nor unusual)

Yeah, no worries. tough love is what I need, or a maybe a new house! I showed my wife some of the data you guys have been serving up, hoping that she would realize I was not the only crazy out there. And it worked. But her comment was, "Do they have wives?" I thought that was unnecessarily sexist.

 

[Holmz]

… "Do they have wives?" I thought that was unnecessarily sexist.

I would call it a feminist incel’t.

 

[Hayabusa]

I recently replaced three ported Klipsch THX 120 subs, stacked in one corner of the room, with a SVS Ultra SB-17. In the other corner are two SVS Ultra 13 cylinders operating not in the sealed mode. Previously these SVS cylinders and the Klipsch operated in the ported mode. Now, with the sealed arrangement, the REW measurement is good (attached), I think, but similar to that of the previous all-ported mode. EQ is by Dirac with Bass control via a Marantz AV10.

But can I get subjective, not only does the bass have more more convincing detail but the detail is better all around, both for music and movies, and this last was a surprise, with an improvement in dialogue clarity, I think.

Here's the REW measurement for the new, sealed arrangement...

Yes..