In the following video, several waterfall graphs are shown, comparing sealed and vented studio monitors. The first graph comparison begins at 0:16.
"Pro Audio Monitors" are all crap. Use these instead:
As stated in the video, there is significant distortion, particularly below 100 Hz, in all of the vented designs, including the passive radiator system. He repeatedly says "small ported speaker" and "if they're small with a port". Well, what about the very large low tuned subwoofer (LLT) designs that became popular on AVS Forum 20 years ago? I suspect that, in a sense, these problems become much more severe due to the huge port area, lowering the first port resonance down in frequency and close to the low pass frequency. Are these time domain distortions not as severe with large vented enclosures?
After watching the short video above, I suppose that if the utmost accurate bass response is desired, sealed systems (including subwoofers) are really the only way to go? However, I would then expect THD to rise significantly for the sealed systems for the same output around Fb. So, more cone area and power would likely be the best choice?
Another thread here from a year ago didn't really show any major solutions to these issues:
So, I guess the best solution in most domestic situations is to go sealed and double up on cone area and power, etc. Thoughts and opinions?
"Pro Audio Monitors" are all crap. Use these instead:
As stated in the video, there is significant distortion, particularly below 100 Hz, in all of the vented designs, including the passive radiator system. He repeatedly says "small ported speaker" and "if they're small with a port". Well, what about the very large low tuned subwoofer (LLT) designs that became popular on AVS Forum 20 years ago? I suspect that, in a sense, these problems become much more severe due to the huge port area, lowering the first port resonance down in frequency and close to the low pass frequency. Are these time domain distortions not as severe with large vented enclosures?
After watching the short video above, I suppose that if the utmost accurate bass response is desired, sealed systems (including subwoofers) are really the only way to go? However, I would then expect THD to rise significantly for the sealed systems for the same output around Fb. So, more cone area and power would likely be the best choice?
Another thread here from a year ago didn't really show any major solutions to these issues:
So, I guess the best solution in most domestic situations is to go sealed and double up on cone area and power, etc. Thoughts and opinions?
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Well, yet another vid we (at least I) won’t bother watching from the beginning to the end. Lots of us know vented systems are a (very often turned out quite well) bag of compromises. So what’s new here? And think of this: LF reproduction is more often than not a product of the loudspeaker-room interface. And: human hearing is astoundingly insensitive to harmonic distortion of low frequencies.
In short: optimize to your needs. A family van won’t win on the race track. But it’s perfect for the groceries and the odd day out in the weekend. Does that make a good or bad car?
This is well known fact that ported speakers store energy on port resonance frequency, this mean also that sound radiation have some delay on port resonance.
Closed box have also resonance, but with less stored energy. OB have even less stored energy than closed box.
Closed box have also resonance, but with less stored energy. OB have even less stored energy than closed box.
We need to go to the details of each design, rather than disregard the ported option.
I agree that most of vented small speakers used in studios don't respond well in low frequencies.
When the port gain is right on the musical bass spectrum, you get more influence of the negative aspects of a ported speaker such as noise, distortion and group delay problems. This happens with small speakers tuned on frequencies at 40Hz and up. So, when you are listening to music you make full use of port gain. If you don't have a choice for bigger box / bigger woofer, maybe a sealed version with strong eq below 50, 40Hz is a better choice.
I did that for my PC speakers - I use a pair of JBL Control One, originally ported (very high tuning). I sealed them and made a huge bass equalization.
On the other hand, if you allow for a bit bigger box (>40 liters) and larger speaker diameter (8" and up), you can tune between 20 and 30Hz and you get a very good low frequency extension. The effect of the port above 30Hz will be a kind of "side" effect and the box will act more like a sealed with all the benefits of it and at the same time you minimize the negative effects of the port. You control the "dose" of the port gain.
This way, you can have a speaker that responds flat down to 30Hz and sounds really good - no need of subwoofer.
In addition, tuning very low let's us be more relaxed with maximum air speed in the port, cause the maximum air speed will be far way from the music normal bass spectrum. You need to worry only about the air speed above 30Hz, for example.
See an example of a 3-way speaker I recently built.
40 liters, 10" woofer and small 2" port diameter - tuning frequency at 23.5Hz.
I installed a pair of them in a studio and people are using them.
They sound much better than the ported KRK (shown in the video as a bad choice) which was previously being used.
30Hz @ -3dB.
I agree that most of vented small speakers used in studios don't respond well in low frequencies.
When the port gain is right on the musical bass spectrum, you get more influence of the negative aspects of a ported speaker such as noise, distortion and group delay problems. This happens with small speakers tuned on frequencies at 40Hz and up. So, when you are listening to music you make full use of port gain. If you don't have a choice for bigger box / bigger woofer, maybe a sealed version with strong eq below 50, 40Hz is a better choice.
I did that for my PC speakers - I use a pair of JBL Control One, originally ported (very high tuning). I sealed them and made a huge bass equalization.
On the other hand, if you allow for a bit bigger box (>40 liters) and larger speaker diameter (8" and up), you can tune between 20 and 30Hz and you get a very good low frequency extension. The effect of the port above 30Hz will be a kind of "side" effect and the box will act more like a sealed with all the benefits of it and at the same time you minimize the negative effects of the port. You control the "dose" of the port gain.
This way, you can have a speaker that responds flat down to 30Hz and sounds really good - no need of subwoofer.
In addition, tuning very low let's us be more relaxed with maximum air speed in the port, cause the maximum air speed will be far way from the music normal bass spectrum. You need to worry only about the air speed above 30Hz, for example.
See an example of a 3-way speaker I recently built.
40 liters, 10" woofer and small 2" port diameter - tuning frequency at 23.5Hz.
I installed a pair of them in a studio and people are using them.
They sound much better than the ported KRK (shown in the video as a bad choice) which was previously being used.
30Hz @ -3dB.
The sealed monitors are not equalized to the same low frequency response of the vented monitors, so the increased decay time due to the lower frequency response gives an inflated "crap" impression.
The wave period of 120Hz, where the sealed NS10 starts it's -12dB per octave rolloff is only 8.3ms, while the wave period of 45Hz is 22.ms.
The lower the frequency, the longer the decay time.
The upper pipe resonance due to the long length of port required for a low tuning is not much of a problem in a subwoofer, since they are typically band-passed an octave or more below.
Yes, by nature the ported system will introduce more delay, as the port output lags one cycle behind the cone output, and will still ring a bit after the input signal has stopped.
THD rises significantly for any design once Xmax (maximum linear excursion,~10% THD) is exceeded.
To match the ~+6dB increase in level the port provides over a sealed system, double the displacement is required.
Two sealed drivers may require more cabinet volume than one ported driver, and may add crossover complexity.
In most domestic situations, the room decay time is so much greater than that of a ported woofer that the problem is equivalent to worrying about a squirt gun in a rainstorm.
If you can hear the difference, and can afford to go sealed for the output desired, go for it.
If you can't, don't.
There's a simple solution to making 'port resonances' inaudible. Just put the port at the back of the speaker 😲
[deleted : 12 pages of obfuscating and incorrect theory on why ports cannot be on the back bla bla ]
Just try it for yourself. Works for wind noise & chuffing from small, crude ports too.
[deleted : 12 pages of obfuscating and incorrect theory on why ports cannot be on the back bla bla ]
Just try it for yourself. Works for wind noise & chuffing from small, crude ports too.
There should be no delay with a non-modal ported enclosure. Phase shift, yes. Excess delay, no.
A 360 degree phase shift between the front radiation and the port output is a delay, whether you consider it excessive is a subjective opinion 😉
The Helmholtz resonator air spring is not instantaneous, were that the case it’s response would be out of phase with the driver, as it inverts the phase of the inverted polarity of the driver’s rear wave.
The cone and port radiate (oscillate) simultaneously, as in phase, but the port lags by 360 degrees.
At Fb, (box tuning frequency) the port output lags the driver by 270 degrees, 90 degrees short of 360 degrees, hence the usual -3dB at Fb for "classic" tuning.
At Fb, the port output lags the driver by 270 degrees, 90 degrees short of 360 degrees.
This can clearly seen in STV's "hard burst" charts, and both his ported and sealed tests show the negative phase "blip" caused by the driver's response to what amounts to a square wave when the sine wave starts:
The driver's response is similar to that of a moving-coil (dynamic) microphone...
Delay is specified over a range of frequencies. Where it applies to a single frequency it is called phase.
I'm using the technical meaning of excess.
This criteria doesn't account for the box compliance or the port mass.
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You had me laughing and yes, of course. One even could use the room as a horn extension to a port.
Most of the Jurassic Corner Horn designs did this. IIRC, one of the seminal Horn Design articles(s) in Wireless World showed this formally and said you should always do this. Alas, the 'box' needs to be very large to take advantage of this.
But I see others are already re-instating my 12 pages of obfuscating and incorrect theory ..... 😊
"Use the room as a horn extension to a port"
"Jurassic Corner Horn"
Any information/photos of this? A quick Google search for "Jurassic Corner Horn" without quotes only brought up references to the Jurassic Park movie franchise. With quotations didn't bring up any results.
"Jurassic Corner Horn"
Any information/photos of this? A quick Google search for "Jurassic Corner Horn" without quotes only brought up references to the Jurassic Park movie franchise. With quotations didn't bring up any results.
Jurassic in audio world relates to pre- electronics so at the beginning...Edison, gramophones
I meant Jurassic as in "very old".
A room corner has a particular 'flare rate'. Classic Exponential horn design has the flare rate tied to the LF design cutoff. The classic corner horns tie this to the room corner flare so the corner acts as an extension to the horn. IIRC the original Klipschorn does this. But the box needs to occupy a lot of space in the corner so the flare rate is correct where it leaves the box and enters the corner.
This might be the WW article(s) but my memory is hazy.
Today, there are many more articles on horn design but I can't seem to find any that explains this simply. Also programs that purport to do da hard sums for you. I don't have any experience wid dis 21st century juju but I'm sure there are horn gurus here who can advise. 😊
A room corner has a particular 'flare rate'. Classic Exponential horn design has the flare rate tied to the LF design cutoff. The classic corner horns tie this to the room corner flare so the corner acts as an extension to the horn. IIRC the original Klipschorn does this. But the box needs to occupy a lot of space in the corner so the flare rate is correct where it leaves the box and enters the corner.
This might be the WW article(s) but my memory is hazy.
Today, there are many more articles on horn design but I can't seem to find any that explains this simply. Also programs that purport to do da hard sums for you. I don't have any experience wid dis 21st century juju but I'm sure there are horn gurus here who can advise. 😊
Look up Klipshorn and JBL Hartsfield. These are folded horns designed to be placed in corners. The walls act as extensions to the bass horn.
I am not too worried about group delay below 100Hz. What do you think the room does to the bass response of a sealed box? I wouldn't use any of these systems without a sub anyway.
Rob 🙂
Without reading any of the posts, just as much of the video as i could stomach.
First: He is using the wrong kind of decay plot to use when talking about resonances. The time axis should be in periods,
Second: He is making inaccurate conclusions from too little information. For instance, his small box/resonance thing… a reflex enclosure uses helmholtz resonance to extend the bass, so more LF ringing is expected, the nature of the alignment having much to do with the resonant behaviour at LF.
dave
First: He is using the wrong kind of decay plot to use when talking about resonances. The time axis should be in periods,
Second: He is making inaccurate conclusions from too little information. For instance, his small box/resonance thing… a reflex enclosure uses helmholtz resonance to extend the bass, so more LF ringing is expected, the nature of the alignment having much to do with the resonant behaviour at LF.
dave
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