I Stuffed My Ported Speakers: The Results Pleasantly Surprised Me

[dfuller]

Indeed, my question was more about whether that EQ introduces more group delay than a bass reflex or not.

Probably less.

 

[RickS]

Indeed, my question was more about whether that EQ introduces more group delay than a bass reflex or not.

I modeled this for the Dayton RSS315 subwoofer. I did not post but recall that when the bass roll off was matched, you ended up with comparable group delay between vented and sealed with eq.

 

[mhardy6647]

For those who might not be comfortable with speaker design software, here is a comparison of the effect of various port plugs here...

What really happens when you plug a speaker port/vent?

As an extension of my comparison test of speaker damping materials, thought I would see how plugging the vent affects its output. In this case, for the Dayton C-Note speaker. As you will see, the result depends a lot on what material you use... So, the red trace is the baseline speaker as...

www.audiosciencereview.com

Hmmm... I wonder if that 'shiny', kind of "firm", open-cell(?) foam material sometimes used for packing material (and now popular for kitchen sponges*) might have interesting properties vis-a-vis stuffing a port?

(I am not, FWIW, being facetious -- for a change!)
_______________
* "Scrub Daddy". I bought one of these (recommended by NYT "Wirecutter" ) for kitchen use and I rather like it so far. Not sure Mrs. H has formed an opinion of it yet for its intended use case, though.

Scrub Daddy - Wikipedia

en.wikipedia.org

N.B. Of course, the geometry of the face probably won't permit using a Scrub Daddy as-is as an efficacious port modification plug.

 

[dualazmak]

....
....
I do actually prefer to use sealed speakers, but only because I think it makes good integration with a subwoofer easier since you don't have the phase issues around the port tuning.
....

Nice point! I too have the same preference.

My woofer YAMAHA 30-cm JA-3058 (ref. #497) is in heavy-rigid-sealed NS-1000 (not NS-1000M) cabinet (39 kg), and it is now directly driven (LCR passive network has been eliminated/bypassed) by dedicated powerful amplifier YAMAHA A-S3000.

In my DSP-based multichannel audio rig, I also integrated large-heavy (48 kg) ported L&R subwoofer YAMAHA YST-SW1000 (ref. #497) which can go down to around 16 Hz. I rather intensively, objectively and subjectively, measured and tuned crossover (XO) between the sealed woofer and the ported active subwoofer; I mean tuning towards optimization of crossover Fq, slopes, relative gains, time alignment, phase/polarity, etc.

I found it would be important first to objectively know/observe (measured by microphone) transient behavior (kick-up as well as fade-out), of woofer and subwoofer by stimulating them using 8-wave and 3-wave sine tone burst of various Fq around the possible XO zone of 30 Hz - 65 Hz (post #495, #503, #507 on my project thread).

As @kyuu pointed, I was impressed that my 30-cm woofer JA-0358 in sealed cabinet, and also thanks to dedicated direct driving by amplifier of nice damping factor, showed/shows unexpectedly nice transient behavior especially fade-out pattern in 50 Hz - 1 kHz Fq zone.

If you would be interested in the latest system setup of my multichannel audio rig, please visit #931 and #1,009 on my project thread.

 

[nqikz]

Yes, that is largely correct for the dominant group delay component. The major difference is that a port will have a longer decay. If you design a port well, this isn’t really an issue.

I’m totally open minded to that. Genelec makes amazing stuff but they are ported do they make the ports in a different way or something?

 

[voodooless]

Genelec makes amazing stuff but they are ported do they make the ports in a different way or something?

Well, they just do a better job, making them large enough and designing them so that very little midrange sound comes out of them. And they are tuned for relatively low group delay.

 

[voodooless]

Fun fact: once you add a high-pass filter to a closed box (which you usually do to prevent overexcursion), you will also increase the group delay. If the frequency responses are about the same vs a reflex config, the group delay will also be the same. Obviously, the ported enclosure will ring slightly more, but when designed well, this can be inaudible.

 

[Tell]

Fun fact: once you add a high-pass filter to a closed box (which you usually do to prevent overexcursion), you will also increase the group delay. If the frequency responses are about the same vs a reflex config, the group delay will also be the same. Obviously, the ported enclosure will ring slightly more, but when designed well, this can be inaudible.

Yeah so arguing that a sealed is better than a (properly designed) ported speaker doesn't really work. The ported speaker is more efficient close to it's tuning frequency by several decibels, while a sealed one have the potential to reach much lower than that ported speakers tuning frequency. It's all about priorities.

 

[574stereo]

Fun fact: once you add a high-pass filter to a closed box (which you usually do to prevent overexcursion), you will also increase the group delay. If the frequency responses are about the same vs a reflex config, the group delay will also be the same. Obviously, the ported enclosure will ring slightly more, but when designed well, this can be inaudible.

Electronic HPF filters are only used when you’re also using EQ though surely… I don’t know of any sealed speaker design which achieves it’s LF response ‘acoustically’ which also has an electronic high pass filter.

 

[voodooless]

I don’t know of any sealed speaker design which achieves it’s LF response ‘acoustically’ which also has an electronic high pass filter.

Basically, every closed subwoofer has this, as well as most closed active speakers. It is simply necessary to prevent overexcursion below FS.

 

[Tell]

Tbh every speaker should have a HPF. Listening to something like Infected Mushroom - Spaniard on a system without one will make the woofer flop around like crazy even at relatively low volume because of that kick that goes down below 20Hz.

 

[dualazmak]

Well, I believe you need large, heavy and rigid excellent L&R subwoofers, and suitable treatments on room/furniture acoustic modes...

Just for your reference...
- Reproduction and listening/hearing/feeling sensations to 16 Hz (organ) sound with my DSP-based multichannel multi-SP-driver multi-amplifier fully active stereo audio system having big-heavy active L&R sub-woofers: #782

- Excellent Recording Quality Music Albums/Tracks for Subjective (and Possibly Objective) Test/Check/Tuning of Multichannel Multi-Driver Multi-Way Multi-Amplifier Time-Aligned Active Stereo Audio System and Room Acoustics; at least a Portion and/or One Track being Analyzed by Color Spectrum of Adobe Audition in Common Parameters:
____[Part-01] Full Orchestral Music: #588
____[Part-08] (Smooth?) Jazz Trio: #640
____[Part-09] Organ Music: #641
____[Part-14] Piano Concertos: #650

 

[Adis]

Tbh every speaker should have a HPF. Listening to something like Infected Mushroom - Spaniard on a system without one will make the woofer flop around like crazy even at relatively low volume because of that kick that goes down below 20Hz.

It's a question of x-max, if you don't have enough add another woofer. Or more...

 

[Tell]

It's a question of x-max, if you don't have enough add another woofer. Or more...

It's always a question of xmax. Well and money, space and WAF

 

[audio2920]

I've never been particularly in to speaker design, beyond a casual interest to better my understanding as an end user (mixer). I do feel some things beyond FR are audible, even at LF, IMHO. I just don't know what... ringing / transient response, phase, GD, all of the above!?

I did some basic testing many years ago on set of Dynaudio BM15s; ran them ports opened and ports stuffed, and made two EQ profiles on my monitoring chain such that either way, the FR measured as close as possible at the mix position.

I briefly looked at phase at LF and either way, on a phase vs freq plot, there was no obvious linearity at all. But, ya know, this was back in the day when BM15s were standard and they were certainly good in their day, but by today's standards, lacked finesse in any metric, so I wasn't surprised.

After EQ they sounded extremely similar in either config, but somehow the ports OPEN sounded better to me. Maybe it felt better, more than sounded better. Could just be sighted bias, but I went into it with the opposite expectation, so I dunno.

If I was looking to identify this sort feeling of difference in one of my mixes (e.g. where one day it felt better than the next, and was demonstrably so when A/Bing mixdowns) I'd be looking at time alignments, phase and/or GD adjustment brought in through my own filters/EQ/other processing. I don't really know how that translates to ported or sealed speaker design.

I suppose my conclusion from this rough and ready test was that sealed does not necessarily mean better behaviour. My sample size for this conclusion was one set of speakers, in one room... And they were ported speakers with [manufacturer supplied] plugs in, not a sealed design.

I'd also note that I wondered if the differences in (in room) phase response just meant that the ports open version pushed phase irregularities away from the kick drum and thus made the bass more solid, whereas the sealed version just fell unfortunately in this particular setup. Dumb luck, in other words. I have no idea; clearly

 

[terryforsythe]

After EQ they sounded extremely similar in either config, but somehow the ports OPEN sounded better to me.

With the port open the woofer does not have a lot of excursion around the port tuning frequency. Equalizing the speakers, with the port stuffed, to have the same frequency response as when the port is open results in much higher excursion, and everything that goes along with that, e.g., higher distortion, higher compression, etc.

 

[audio2920]

With the port open the woofer does not have a lot of excursion around the port tuning frequency. Equalizing the speakers, with the port stuffed, to have the same frequency response as when the port is open results in much higher excursion, and everything that goes along with that, e.g., higher distortion, higher compression, etc.

Yes of course; tons of things change when you plug the port. But they sounded extremely similar, none the less. The BM15 was quite capable with SPL / dynamics, probably it's greatest strength, in fact; I wasn't hearing compression. But for sure, reduced distortion could have played a part in my preference.

Anyway, the purpose of me doing, at the time, was not a general "do I like ports or not" test but just to establish the best config to run my (then new) monitors in while having sufficient headroom for room EQ and the required SPL. And it turned out there was little to choose, in practice, on this particular occasion.

 

[Tell]

Yes of course; tons of things change when you plug the port. But they sounded extremely similar, none the less. The BM15 was quite capable with SPL / dynamics, probably it's greatest strength, in fact; I wasn't hearing compression. But for sure, reduced distortion could have played a part in my preference.

Anyway, the purpose of me doing, at the time, was not a general "do I like ports or not" test but just to establish the best config to run my (then new) monitors in while having sufficient headroom for room EQ and the required SPL. And it turned out there was little to choose, in practice, on this particular occasion.

I did kind of the same thing when I built my two subwoofers during the autumn, I 3D-printed the ports but I also at the same time printed a flat thing that I could mount instead of the port so I could try them both. EQd they sounded more or less the same, except below the tuning frequency of the port where it quickly turned into chuffing and not much bass at all, but with the flat panel I could make them dig much deeper but instead with much higher excursion and therefore less total output volume. I do use the ports now since I gain around 6dB more output at and above the tuning per woofer which is much more fun, especially since they sound just as good. They are of course high pass filtered so they don't have to even try to play below ~30Hz.

 

[levimax]

Basically, every closed subwoofer has this, as well as most closed active speakers. It is simply necessary to prevent overexcursion below FS.

The only reason a "sealed sub" needs a high pass to prevent over excursion below FS is if it "boosts" LF to get better marketing LF specs. If there is no extra LF boost the pressure inside the sealed box will protect from over excursion. Unfortunately in the world of "smaller is better" we live in most commercial sealed subs do require a protective high pass and they do indeed have very high group delay. You can get a feel for how poor many popular subs actually perform here https://www.audiosciencereview.com/forum/index.php?threads/i-measured-10-subwoofers.49042/

 

[mhardy6647]

One thing that seems to be (may be) missing in the discussion in this thread: the optimal Thiele/Small parameters for a woofer in a bass reflex alignment are not identical to those for a sealed box alignment of the same internal volume. Indeed, a woofer designed for bass reflex (Helmholtz resonator) loading will not be ideal for an acoustic suspension alignment -- although it might be appropriate to an infinite baffle.