"Fast", "Punchy" and other such subjective terms used to describe bass

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AcousticScience
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"Fast", "Punchy" and other such subjective terms used to describe bass

#1 Post by AcousticScience » Sun Mar 29, 2020 10:41 am

When used according to their direct definitions, there is no such thing as a "fast" subwoofer, it is simply meaning extended frequency response and having midrange that matches well to your subwoofer. The effect I'm talking about here has very little to do with the "speed" or acceleration of the cone within a single cycle as it is correct that the cone acceleration is dependant only on frequency and amplitude and applying more power to a heavy cone woofer will move it the same acceleration as a lighter woofer, therefore it is inaccurate to say that "8s are faster than 15s" or other such expression. Apart from anything else, size and cone mass don't directly correlate. There are some 8" and 10" car audio woofers with heavier cones than a Kappalite 3015lf which has a very light cone for its size.

Often when these terms are used, they are referring to something else in rough terms but the effect is still frequency dependent and heavily variable according to enclosure design:
Group delay: How long it takes the speaker to reach its maximum working amplitude according to the signal entering it.
Waterfall response: How long it takes for the speaker and enclosure to stop making a noise after you have stopped sending a signal to it.

Different woofer designs use tricks to improve their efficiency through combinations of resonance and impedance matching.

A sealed enclosure amplifies bass by resonance of the combined driver and airspace on speaker spring effect. It will resonate at the combined result of the speaker's surface area vs enclosed air and cone mass, and also the suspension compliance according to Hooke's law and the cone mass. A low resonance helps the speaker "get its swing on" and gives more efficient low bass though takes a couple of cycles to build up to maximum amplitude. A high resonance does this with upper bass but doesn't offer aid at lower bass.
If you play bass at a speaker's resonant frequency it will sound inherently "slow" because it will take a few cycles to build up to its stable amplitude (the bass will grow gradually louder when this is happening) and a few cycles to swing to nothing (the bass will grow gradually quieter rather than immediately shutting off).

A ported enclosure will have a similar resonance to the sealed at a higher frequency somewhere in the pass band (where the speaker is moving the most), and a lower resonance of the port air (where the speaker is moving the least). At both frequencies, the speaker will have a tendency to ring. There is also below pass band resonance but usually below your mandatory high pass filters so of little concern with appropriate protection device.

A horn will have a resonance at about its quarter wave and multiples thereof (and possibly some to do with the sealed chamber size hopefully well chosen to flatten out response a bit). Someone saying "My Titan 39 sounds 'faster' than my Tuba 60" is sometimes getting into the misnomer above, but also it takes a larger amount of mouth area to damp the lower resonance of a Tuba 60 as in a fully sized horn. The longer horn might reduce efficiency in the upper bass compared to a Titan giving less subjective "punch". The longer horn might be less well time aligned to midbass chest hits from your mid/high speakers. The lower notes being prominent distract you from the tightness of the upper bass.

Sound waves will reverberate around a loudspeaker enclosure for a while.

The room: A car will have quite a short reverberation time so your bass will sound better here than in a gymnasium with several seconds of reverberation time. This will dwarf any talk of differences between horn, tapped horn, 6th order bandpass and sealed and ported. Outdoors will be good as there is usually no immediate reverberation and the echo there is is usually much quieter than the music in a wide open space. A pair of headphones or earphones is the Holy grail of tight accurate bass response due to this and the fact that the drivers are very light compared to their suspension resistance and any damping of the amplifier.

Speakers and enclosures will have braking forces:
Mechanical suspension resistance: They are not a perfect spring and will dissipate the cone's energy as heat.
Electrical damping factor: A speaker feeds back electromotive force back into the amplifier which is "shorted out" through the output transistor and speaker voice coil loop.
Acoustic brake: The expanding path of a horn will radiate away the cone's kinetic energy converting it into sound - one of the reasons why horns seem to retain the staccato bass hits quite well. A horn that is too small will not do this quite as well as there isn't enough surface area of air at the end of the horn to damp the quarter wave resonance.

Aperiodic enclosures use a foam stuffed tunnel behind the driver to deliberately create air friction to brake resonant behaviour. It creates the same effect to the speaker as does breathing through a cloth. It should offer an accurate reproduction but aren't very efficient as they waste the energy rather than converting it to sound as a horn does. Too much stuffing and the speaker will have trouble moving. A transmission line enclosure is a cross between this and also quarter wave pipe at very low frequencies. You can have a stuffed long port or labyrinth that boosts lower bass and damps upper bass and above which is absorbed in the stuffing.

Also low cone mass and electrical Q allow there to be both less mass swinging back and forth and easier to electrically damp.
I will add this. The larges effect on the subjective quality of the accuracy of the bass is by far THE ROOM. In a car, your bass will sound quite tight and accurate. In a gymnasium it will not.

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Seth
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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#2 Post by Seth » Sun Mar 29, 2020 12:49 pm

Thanks for the read. It's obvious you're quite a bit more passionate about this than the average enthusiast.

What's your name man? I'm Seth.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#3 Post by AcousticScience » Wed Apr 01, 2020 1:36 am

I'm Tim, long time internet forum browser, but only a few builds as it is easy to end up filling a studio flat. From designs on here: A pair of Omnitop 12 and an Autotuba. However I have been interested in horns for quite some time (since hearing a load of the Funktion One bass cabs and liking the clean bass pressure you could feel in your ears. It was very clean like the bass of powerful headphones that you could feel and the harmonic distortion of hard driven vented subwoofers often sound like a bass guitar in comparison. I did want to hear them in a group of 8 though instead of spaced around in stacks of 2. I do think with horns this keeps the lowest notes from dissipating.

And had a 32 cubic foot box that was poorly designed, mdf and hardboard, flexed and probably leaked (before I discovered well designed horns) although played surprisingly well. A labsub, Inlow horn, 12pi or pair of Tuba 45 would probably work better in the same volume.

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#4 Post by Bryan Cox » Wed Apr 01, 2020 9:07 am

AcousticScience wrote:
Sun Mar 29, 2020 10:41 am
..."bass"...
That's where I got lost...😆
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#5 Post by Seth » Sat Apr 04, 2020 2:06 am

AcousticScience wrote:
Wed Apr 01, 2020 1:36 am
I'm Tim...
Hey Tim, nice to meet ya buddy. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#6 Post by Seth » Tue Apr 07, 2020 3:20 am

SethRocksYou wrote:
Sat Apr 04, 2020 2:06 am
AcousticScience wrote:
Wed Apr 01, 2020 1:36 am
I'm Tim...
Hey Tim, nice to meet ya buddy. :thumbsup:
Tim... Tim... Timmmmmm... Something is starting to tickle and tingle upstairs. A tinge of familiarity, like my mind putting loose clues of a puzzle together. Not Tim Lewis, is it?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

AcousticScience
Posts: 137
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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#7 Post by AcousticScience » Tue Apr 07, 2020 4:18 am

SethRocksYou wrote: Tim... Tim... Timmmmmm... Something is starting to tickle and tingle upstairs.
Well that's better than tickling and tingling downstairs..

Must be a common as mud name round here....

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#8 Post by Seth » Tue Apr 07, 2020 4:32 am

Yes... I remember now. I really like the audio quality of your YouTube vids. Well done sir. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

AcousticScience
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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#9 Post by AcousticScience » Tue Apr 07, 2020 5:12 am

Why thank you! I wanted to capture the sound instead of people trying to guess the power of a system by how wet and raspy the fart sounds. Also there's no point in a video where the Bill Fitzmaurice stuff sounds no better than a horizontal array of unprocessed Skytec cabs driven to 5 x their rated power. You know those endless car audio videos with 8 18 inch subwoofers moving 3 inches peak to peak (that must make you feel like you have swimmer's ear). I wish I had a more portable way of doing it for recording live concerts. I don't really want to carry my laptop with an old battery that runs out in 90 minutes, audio interface, condenser mic, cables AND a separate camera to a live show.

I recorded a few Darkness concert clips on a £10 Alcatel Phone when all my smart phones were out of order. The audio was practically unlistenable. Another Clubland which plays Happy Hardcore and Pop Trance event outdoors, the subwoofers sounded like fart as usual. Most cameras are setup with pre-amp gains for recording the human voice. I hear those Zoom recorders are quite good but not looking to spend extra money. The microphone is not usually the weak link. It's quite hard to bottom out a mic capsule (ribbon mics are most vulnerable to large blasts of air on a kick drum hole).

So as not to music torture my neighbours during the Covid-19 outbreak stay at home, that sort of level testing is out for a while. I put on Three Pound Chicken Wing by Deadmau5 and the landlord said he could feel it in his house over the road - didn't turn it up all the way either!

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#10 Post by shrub0 » Tue Dec 08, 2020 5:47 pm

I'm sure if it's the lower cone excursion per spl or the flatter phase response but my david towers (basically an autotuba) do drums like nothing else. I'm watching the cartoon avatar with my daughter and there is alot of drums in the soundtrack. Taiko drums I believe, and it sounds great.

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#11 Post by camp10 » Mon Apr 12, 2021 9:22 pm

Good read! Group delay is definitely the culprit and your design is the conduit...I once said that any vented design with the resonate note placed within the passband is "sloppy"....the group delay suffering, due to the conditions around the tuning note (woofer diapragm slow to move but once moving loves to keep doing so) shows in the measurements as high group delay and long decay....Resonant notes are bad for a person seeking critical monitoring. I've always operated by that philosophy but I am now learning that the room is much "sloppier" and we only hear the decay flaws if the room is very clean acoustically... I design large nearfield monitors and I think that this situation and its high direct energy experience may expose these (decay and group delay) flaws more so than mid and far field. For the average person, decay seems to be trivial due to the room having the final say so. Group delay.... is perceivable when it is much higher than the rest of the bandwidth...they say it is forgiving in the bass region but a bad design (>15ms within desired passband) has group delay pushed out far enough to an issue for the most critical...the problem is that music is so unique...the attack envelope on a bass sound in any song is going to be different on every song....and we can get away with bad amounts of group delay a lot of times because you would only know it was off if you heard it without group delay (headphones)....A/Bing between a nice pair of headphones or a system with very low group delay in the bass, it becomes more obvious, the difference between 10ms and 20ms....will you care? Maybe lol

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Re: "Fast", "Punchy" and other such subjective terms used to describe bass

#12 Post by Bill Fitzmaurice » Mon Apr 12, 2021 9:52 pm

Actually group delay is blown way out of proportion. For group delay to be a factor the design would have to be so flawed that the group delay would be the least of it's problems. Audiophiles tend to be concerned about group delay because the value looks like it should be serious. If that was the case then a 47ms maximum and average of 20ms throughout the pass band should give a very bad result. Owners of a speaker with that spec, the Tuba HT, would disagree.

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