Underdamped response = missing sound quality?

[bachatero]

I love my new KH 150s but I feel like there's a slight problem with them. They have an underdamped step/impulse response, which means that any impulse coming in will ring a nonzero amount.

This is largely due to the speaker's ported design. To make sound through the port's resonance, you first need a pump from the driver and only after a delay does the port finally resonate at peak amplitude. That's a problem because it leads to sounds "sticking around" and masking ones coming milliseconds later. I'm not exactly sure how audible this is, but it does seem to make a difference in the bass region.

Right now I'm using a Kali WS-6.5 sub with my KH 150s to get the bass down to around 31Hz. However, it's a ported design. Because of this underdamped issue, would it be worth it to upgrade to a sealed sub? Also, should I have held out for a sealed Neumann speaker with DSP, since the 310A is still stuck with analog?

 

[terryforsythe]

I wasn't completely satisfied with my Elac speakers' bass response, even when using a subwoofer. I plugged the ports on the speakers. Subjectively listening, that made the bass sound tighter to my ear and I was able to get a smoother frequency response in the crossover region between the sub and the speakers.

The downside is that the speakers' bass response does not extend as low, so I ended up crossing them over higher, around 100Hz. I used 8th order slopes to minimize the effect of the subwoofer drawing attention to itself. I'm happier with it now.

 

[terryforsythe]

Right now I'm using a Kali WS-6.5 sub with my KH 150s to get the bass down to around 31Hz. However, it's a ported design. Because of this underdamped issue, would it be worth it to upgrade to a sealed sub? Also, should I have held out for a sealed Neumann speaker with DSP, since the 310A is still stuck with analog?

I would first experiment with plugging the ports on the speakers. I used dense foam, but you probably can use a pair of socks for expermentation purposes (hopefully clean socks ). DSP certainly does help, though, with getting a smooth transition between the subwoofer and speakers and for room correction.

EDIT: Is it possible in your setup to add external DSP? Maybe a miniDSP 2x4HD?

 

[ppataki]

I love my new KH 150s but I feel like there's a slight problem with them. They have an underdamped step/impulse response, which means that any impulse coming in will ring a nonzero amount.
View attachment 435754
This is largely due to the speaker's ported design. To make sound through the port's resonance, you first need a pump from the driver and only after a delay does the port finally resonate at peak amplitude. That's a problem because it leads to sounds "sticking around" and masking ones coming milliseconds later. I'm not exactly sure how audible this is, but it does seem to make a difference in the bass region.

Right now I'm using a Kali WS-6.5 sub with my KH 150s to get the bass down to around 31Hz. However, it's a ported design. Because of this underdamped issue, would it be worth it to upgrade to a sealed sub? Also, should I have held out for a sealed Neumann speaker with DSP, since the 310A is still stuck with analog?

Have you tried some DRC like Dirac Live?

This is one of my previous systems, a Nubert nuVero 140 (also a reflex speaker) step response before correction and after correction with Dirac Live, measured in the MLP

As you can see the difference is night and day, not just on the graph but by ear too
Bass has become much tighter and precise thanks to the reduced ringing

It is also clearly visible on the wavelet diagrams

I agree with @terryforsythe that plugging the port should also have a big impact
I did the same in this project, you can see the difference on the measurements, it is huge
(just be prepared that you will probably need a low-shelf filter to compensate the lows)

 

[bachatero]

I should have been clearer, these speakers and the sub are at my desk so I have unlimited DSP access but that doesn't matter. I just want to know if the oscillation from an underdamped response means that I'm losing sound quality in the subwoofer and potentially the KH 150s.

 

[ppataki]

I should have been clearer, these speakers and the sub are at my desk so I have unlimited DSP access but that doesn't matter. I just want to know if the oscillation from an underdamped response means that I'm losing sound quality in the subwoofer and potentially the KH 150s.

Can you post your measurements?

I would still try DSP and see the measurements before/after and also listen to it - then you will be able to tell for yourself if you lose sound quality or not; and the same goes for plugging the port

But to answer your question: based on my personal experience with DIY in the last 5 years, a sealed sub will provide you with a much better impulse response, step response and wavelet graphs and bass will sound 'faster' and more precise. I personally love it, however, many people don't prefer it, they say that it sounds 'dry' and 'cold' and less 'juicy'.
If you plug the port properly, you will get pretty close to how a sealed sub would sound. Hence we are telling you to experiment in various ways before jumping into the world of sealed speakers.

 

[ppataki]

But to answer your question: based on my personal experience with DIY in the last 5 years, a sealed sub will provide you with a much better impulse response, step response and wavelet graphs

Just to give you an idea about the difference: these are the wavelet graphs of a Yamaha HS10 reflex sub vs my DIY Dayton Audio RSS315-HF4 based sealed sub in the same room, same MLP, back from 2020

The peak energy delay is less than half with the sealed sub vs the reflex sub

And group delay will show the difference very well too:

 

[voodooless]

Comparisons like this are useless if you do not first match the response of the systems. Group delay is the derivative of the frequency response in a minimum phase system, so obviously a reflex system will have higher group delay and more swing.

 

[ppataki]

Comparisons like this are useless if you do not first match the response of the systems. Group delay is the derivative of the frequency response in a minimum phase system, so obviously a reflex system will have higher group delay and more swing.

The Wavelet graph will stay largely the same in terms of the peak energy delay, even when the response is compensated

These are my subs with zero DSP vs with Dirac:

You can see that there is significant compensation below 40Hz

Still, the Wavelet Peak Energy Delay stay almost the same before/after (post-ringing gets much better though + pre-ringing gets a bit worse)

If I put any reflex speaker in my room in the past, they all had 2-3x higher peak energy delay, regardless of any DSP - as seen above with the Yamaha HS10 and the Nubert nuVero 140

Group delay did get higher as you rightly pointed that out, but nowhere close to that of a reflex speaker (like the HS10):

 

[terryforsythe]

I just want to know if the oscillation from an underdamped response means that I'm losing sound quality in the subwoofer and potentially the KH 150s.

Perhaps.

But, as far as audibility, I think it would be more of an issue for the speakers than the subwoofer. I'm not saying there is not a benefit to having a sealed subwoofer, I just think there is more of a benefit to having a sealed speaker. It just means using a higher crossover frequency and perhaps adding some DSP to fine tune the crossover region.

 

[thewas]

If you use EQ you can also close the ports of the loudspeaker or subwoofer and equalise to the desired response at the listening position, you loose in max SPL and distortion. Equalisation in the bass region anyway makes more sense to do for the combined loudspeaker plus room response. Since there usually room modes dominate and decay slower my experience is that, if done well, both equalised to the same response won't have significant audible differences so I usually prefer taking the advantage of max SPL and lower distortion but feel free to try both and make your own listening judgement.

 

[bachatero]

I just tried stuffing the Kali's port and all I heard at first was more distortion and lower volume. But, with my favorite music, the bass parts seemed like they had a little less reverb? So I got a recording of stuffed versus open while playing a 250ms 40Hz tone on repeat and here's what I found:

At the red circles, you can clearly see how the stuffing makes it so the first two peaks of the 10 are closer to the ideal, and the 11th peak decays faster. With open, it's slower to get to maximum amplitude from zero and to zero from maximum. However, the remaining decay after the 11th peak remains a wash with no clear winner, so that might just be the room.
Here's the impulse response of my room too with the port open:

 

[terryforsythe]

Can you do the same experiment with a 150Hz tone?

 

[bachatero]

Stuffed top open bottom

Looks like the open one has a little bit more overshoot on the initial peak and a little extra reverb?

 

[thewas]

By just closing the port and not doing any EQ you are changing also the frequency response so obviously the time response also changes but such is not good view for humans to analyse nor to correlate with audibility, see more about from Toole:

An Enticing Marketing Story, Theory Without Measurement?

Other way around will do the most to improve your sound. EQ can be used of course with beneficial results but taking care of issues that DSP and EQ cannot compensate for is even better - then the process you intend to use for room EQ/correction/convolusion will have an easier time of it and the...

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[Holmz]

I love my new KH 150s but I feel like there's a slight problem with them. They have an underdamped step/impulse response, which means that any impulse coming in will ring a nonzero amount.
View attachment 435754
This is largely due to the speaker's ported design. To make sound through the port's resonance, you first need a pump from the driver and only after a delay does the port finally resonate at peak amplitude. That's a problem because it leads to sounds "sticking around" and masking ones coming milliseconds later. I'm not exactly sure how audible this is, but it does seem to make a difference in the bass region.

And some of the initial attack might affect timber etc.
So sounds “hanging on” does seem to lessen the SQ.

Right now I'm using a Kali WS-6.5 sub with my KH 150s to get the bass down to around 31Hz. However, it's a ported design. Because of this underdamped issue, would it be worth it to upgrade to a sealed sub? Also, should I have held out for a sealed Neumann speaker with DSP, since the 310A is still stuck with analog?

I dunno - but I am in the process of integrating subs in… I have the subs and amps, but no box yet, etc…

 

[bachatero]

By just closing the port and not doing any EQ you are changing also the frequency response

You'd think this, but I normalized the amplitudes of the recordings to account for this.

 

[thewas]

You'd think this, but I normalized the amplitudes of the recordings to account for this.

That is something different though.

 

[bachatero]

That is something different though.

What is it?

 

[thewas]

What is it?

You are not equalising the loudspeaker to the same frequency response with closed port as it was with open port by normalising the amplitudes of the recordings, you need to frequency response measurements and use EQ for that.