Sealed versus Ported Bass, can the difference be measured?

[Keith_W]

Thanks for the instructions, but I will not be stacking up those three klipsch subs, after moving the SVS 17 (72 kg) out of the way. If only I was younger and more technically adept...

I don't know the subs you are talking about. But if your current subs are ported, it's a fairly simple matter of measuring only one sub with the port open and the port closed. Stuff the port with an old t-shirt, that should do the trick.

 

[Paul McNeil]

I don't know the subs you are talking about. But if your current subs are ported, it's a fairly simple matter of measuring only one sub with the port open and the port closed. Stuff the port with an old t-shirt, that should do the trick.

I'm not interested in the difference in sound of my ported (Klipsch THX) subs when sealed with anything, including a t-shirt. The F3 will be way down, for sure. And I'm sure the drivers were NOT designed for sealed operation.

 

[dasdoing]

For a minimum phase system, though, frequency response and group delay are two sides of the same coin.

the port creates a resonance.

 

[dasdoing]

Yes, it is but I don't think I can measure it with REW. REW does offer a group delay measurement, and I posted this for my ported versus sealed arrangement. I couldn't see/interpret any differences. No on else has offered help. One poster indicated that GD could not be measured accurately in room with REW.

And SVS, a manufacturer of both, says, more or less that well designed sealed and ported subs (like theirs) are difficult to distinguish.

I wonder, are those of us who hear a difference between sealed and ported in the same class of fools as those who hear cable differences?!

It depends on how deep the port is tuned. Group delay below 35 Hz-ish can probably be ignored. I mean, where does a kick's low energy lie? 50-80 Hz?
Only synth bass will play below that. and these are not percussive tones.
try some fast percussive kicks to hear the difference. the intro of Wanna be starting something for example.

 

[levimax]

It depends on how deep the port is tuned. Group delay below 35 Hz-ish can probably be ignored. I mean, where does a kick's low energy lie? 50-80 Hz?
Only synth bass will play below that. and these are not percussive tones.
try some fast percussive kicks to hear the difference. the intro of Wanna be starting something for example.

Kick drums extends to 20 Hz or even lower....

 

[ryanosaur]

Kick drums extends to 20 Hz or even lower....

This goes against everything I had ever learned. Please substantiate for the class.

 

[dasdoing]

Kick drums extends to 20 Hz or even lower....

could happen in some rooms, but notice I mentioned energy aka the peak. you wont hear a delayed 20Hz rumble when there is a peak at 50Hz 20dB higher

 

[levimax]

This goes against everything I had ever learned. Please substantiate for the class.

Most references talk about mixing kick drums and most recommend the lower range be rolled off so I don't think most recordings have a lot of Kick Drum LF information but that does not mean that it is not there on all recording. I did read somewhere that an actual kick drum approaches "zero" Hz but I can't find anything on it now. See below a link, there are many like this that talk about the 20 Hz to 50 Hz range.

Unraveling the Kick Drum: A Guide to Frequency Ranges

www.pauseplayrepeat.com

 

[dasdoing]

you can always download some at freesound and import them to REW as audio data.
this one for example, which says it is beefy: https://freesound.org/people/Ja.nefield1337/sounds/681776/

looks like this:

not much there below 55, in terms of energy that could fall into your eye (ear)


but yea, it doesn't sound beefy at all anyways.
let's look at another one: https://freesound.org/people/Sound_Bar_KK/sounds/685865/

that sounds deep. how does it look like?

just as I said before. typicly you will have the main energy above 50Hz.


so a big ported SVS wont have audible group delay with a typical kick.
but not everybody has a sub like this

 

[gnarly]

This is a great analysis and measurements of what I have observed as I moved from very small sealed commercial subs to very large DIY Ported / Sealed subs. Did you run this test with the "protective high pass" on the ported sub? I assume this would make ported sub look worse but I would be very interested to see it.

Glad my tests made sense. It's clear we both enjoy trying to tighten up bass and bass transients
I did run bursts with both IIR and FIR high-pass filters...I just looked for them but haven't found the right drive yet. Will post if I do.
The IIR high-pass, as you would expect, increased group delay quite a bit.
Personally, I think most everyone has group delay all wrong...all I hear is people talking about it in terms of ms.
I see group delay as envelope-distortion that warps any audio waveforms within the range of frequencies it spans. Nothing to do with timing, one frequency vs another.

My take away so far is that trying to get the "timing right" across the audible spectrum is a good goal even if it is only audible in limited circumstances (like a kick drum) but these limited circumstances can be very entertaining. The biggest obstacle to getting the "timing right" is group delay caused mostly by physical and electrical filters used in speakers and subs to try to get around "Hoffman's Iron Law" and make them "too small". Integrating large sealed mains with large sealed subs is very easy compared to trying to integrate ported mains and ported subs. With ported mains and subs the timing will never be "right" except at one frequency (hopefully the crossover). At what level does all of this become audible is unfortunately not researched. Without research my observations say a 20 ms timing mismatch (below Schroeder) is OK, 100 ms isn't, in between I don't know.

Yep. That's the type research we have to do. My take so far in rooms, is that time alignment subs-to-mains, is more important than phase alignment. Simply because rooms are so effed up with reflections to begin with, it makes phase alignment mainly BS. Outdoors, both time alignment and phase alignment rank closer together....lord knows it's the number one topic of live sound system techs, cause it's proven to matter.

 

[gnarly]

you can always download some at freesound and import them to REW as audio data.
this one for example, which says it is beefy: https://freesound.org/people/Ja.nefield1337/sounds/681776/

looks like this:

View attachment 462335

not much there below 55, in terms of energy that could fall into your eye (ear)


but yea, it doesn't sound beefy at all anyways.
let's look at another one: https://freesound.org/people/Sound_Bar_KK/sounds/685865/

that sounds deep. how does it look like?

View attachment 462336

just as I said before. typicly you will have the main energy above 50Hz.


so a big ported SVS wont have audible group delay with a typical kick.
but not everybody has a sub like this

The problem I've found with this type of analysis for transients, is to get that degree of frequency resolution you have to use a FFT sample size that essentially thows out time domain information............the very time domain signal/content/ information we are tying to analyze !!!

Imo/ime, we have to analyze time domain transients like a kick drum or electronic bass drops in the time domain, via impulse or scope bursts, etc.
Frequency domain just leads us to misdirected conclusions.

 

[levimax]

wont have audible group delay

What do you think the limits of group delay audibility are? I am not trying to be sarcastic but as far as I can tell there is not much study that has been done, just some "rules of thumb" i.e. 1.5 cycles or 2 cycles which make some sense at high frequency but not so much at 20 Hz.

Same thing for audibility of LF distortion. I think most would agree LF distortion is less audible than distortion at higher frequencies but how much? The CEA-2010 standard for subwoofer testing allows 100% distortion for a "pass" at 20 Hz which seems high to me. I tried to research where this "standard" came from but could not find anything, it appears they just made it up. Unfortunately the sub manufacturers use this standard and the lack of knowledge of the average sub buyer to make them think they are buying something they are not.

 

[levimax]

I see group delay as envelope-distortion that warps any audio waveforms within the range of frequencies it spans. Nothing to do with timing, one frequency vs another.

Can you explain this a little more? I am having a hard time wrapping my head around it.

 

[ryanosaur]

Most references talk about mixing kick drums and most recommend the lower range be rolled off so I don't think most recordings have a lot of Kick Drum LF information but that does not mean that it is not there on all recording. I did read somewhere that an actual kick drum approaches "zero" Hz but I can't find anything on it now. See below a link, there are many like this that talk about the 20 Hz to 50 Hz range.

Unraveling the Kick Drum: A Guide to Frequency Ranges

www.pauseplayrepeat.com

I saw an interesting spectro of John Wick and most of the gunfire was in the 30-50 range. Similar to Kick Drum. I had worked with a percussionist that said most Floor Toms are tuned lower than the Kick. And a Kick Drum is a very different and much smaller animal than many Bass Drums I've been around. The funny thing is that the myth thrives that Percussion is almost always lower freq. than it actually is, with none I am aware of having a true infrasonic fundamental the way the 32' stop on a Pipe Organ has.

That link was cool, but didn't actually address the tune and freq range of a Kick Drum. FWIW, Most Kicks are 40-60... some few lower, and I've seen mention of tuning as high as 114-120Hz. That link's advice to not boost infrasonic freq. is accurate. But even as low as 20Hz is pointless unless that is simply the range the mixing board allows as that author specifies 20-60Hz.

Of course, most of this is strictly academic as these type of drums, though tuned in the sense of head tension, do not really convey a specific pitch as that is all lost in the harmonics produced as well. Contrast with a Tympani which is tuned quite specifically and does convey pitch.

On the other hand, as was also mentioned, is the room and ambience effect. This can't be looked beyond, however is a separate topic than the actual recorded event of a Kick Drum being hit.

To that end, some drummers use triggered Mics so as to minimize the pollution of their kits by the room. I think the first time I saw this was in book about Pink Floyd I read back in the 80's that had a spec list of everything the site needed to supply for a performance and among them were the Mics for Nick's kit.

Been a long while since I was in a studio... almost a different life now.

Anyway, not meaning to further derail this thread.

 

[levimax]

I saw an interesting spectro of John Wick and most of the gunfire was in the 30-50 range. Similar to Kick Drum. I had worked with a percussionist that said most Floor Toms are tuned lower than the Kick. And a Kick Drum is a very different and much smaller animal than many Bass Drums I've been around. The funny thing is that the myth thrives that Percussion is almost always lower freq. than it actually is, with none I am aware of having a true infrasonic fundamental the way the 32' stop on a Pipe Organ has.

That link was cool, but didn't actually address the tune and freq range of a Kick Drum. FWIW, Most Kicks are 40-60... some few lower, and I've seen mention of tuning as high as 114-120Hz. That link's advice to not boost infrasonic freq. is accurate. But even as low as 20Hz is pointless unless that is simply the range the mixing board allows as that author specifies 20-60Hz.

Of course, most of this is strictly academic as these type of drums, though tuned in the sense of head tension, do not really convey a specific pitch as that is all lost in the harmonics produced as well. Contrast with a Tympani which is tuned quite specifically and does convey pitch.

On the other hand, as was also mentioned, is the room and ambience effect. This can't be looked beyond, however is a separate topic than the actual recorded event of a Kick Drum being hit.

To that end, some drummers use triggered Mics so as to minimize the pollution of their kits by the room. I think the first time I saw this was in book about Pink Floyd I read back in the 80's that had a spec list of everything the site needed to supply for a performance and among them were the Mics for Nick's kit.

Been a long while since I was in a studio... almost a different life now.

Anyway, not meaning to further derail this thread.

Rather than ultimate LF extension I find kick drums a good test of the alignment of mains and subs because they have both HF and LF content played simultainiously. If the timing is off it is relatively easy to hear.

 

[Holmz]

The problem I've found with this type of analysis for transients, is to get that degree of frequency resolution you have to use a FFT sample size that essentially thows out time domain information............the very time domain signal/content/ information we are tying to analyze !!!

Imo/ime, we have to analyze time domain transients like a kick drum or electronic bass drops in the time domain, via impulse or scope bursts, etc.
Frequency domain just leads us to misdirected conclusions.

100%

People talk about group delay being something at one frequency and something else at another frequency.
What one sees in the time domain is a stretched out lumpy mess.

Rather than ultimate LF extension I find kick drums a good test of the alignment of mains and subs because they have both HF and LF content played simultainiously. If the timing is off it is relatively easy to hear.

100%

 

[Cbdb2]

Of course, most of this is strictly academic as these type of drums, though tuned in the sense of head tension, do not really convey a specific pitch as that is all lost in the harmonics produced as well. Contrast with a Tympani which is tuned quite specifically and does convey pitch.

Proper drum tunning involves pitch.

How to Tune Drums: Expert Tips for the Perfect Sound | Keep Drumming

Tuning a drum set is a critical skill for drummers of all levels, directly impacting the quality of sound produced by your instrument. Proper tuning aligns the pitch and tone of your drums, creating a cohesive and pleasant sound whether you're practicing at home or performing live. Unlike other...

www.keepdrumming.com

And sometimes there even tuned to the key of the song. From: https://www.redpackdrums.com/post/tune-drums-to-song-key

"Percussion instruments don't have a well-defined overtone series, so our brains don't really interpret any one pitch as a "fundamental." We don't really perceive a particular note, so it doesn't need to be in tune with everything else. However, tuning your drums to the key of your song can enhance the overall harmony, making your track sound more cohesive."

 

[Cbdb2]

On the other hand, as was also mentioned, is the room and ambience effect. This can't be looked beyond, however is a separate topic than the actual recorded event of a Kick Drum being hit.

The contribution of the room when real drums are recorded is huge. Many rock/pop studios in the 70s, 80s became famous (among recording engineers) for the way drums recorded in there room.

 

[sigbergaudio]

This might be relevant too:

EDIT; oops, just remembered I had to explain the video.

He goes through in some detail which frequencies from both music and movie effects that create that chest impact feeling reside, concluding that they are lower than people think.

 

[sigbergaudio]

My experience is that many of the really impactful sounds (like percussion) are quite wideband, so you need both the low-end and the range all the way up to 500hz in order.

I also swear to sealed subs, but recently ended up designing our full range loudspeaker to be ported to get enough capacity in the bottom end. And tuned to 28hz I'm hard pressed to say that it sounds any less tight and punchy than the sealed subs if I'm honest (which I try to be).