what was that called that Augsperger suggested where an active lowpass filter's corner is set at the vented box fb? (~20Hz)
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The speakers of our youth (in my case anyway!) were sealed, and I have recently bought a few vintage pairs of sealed speakers which I think do seem to do something correctly that modern ported speakers are messing up. I have also built my own rather large sealed woofers (90 litre) that go very deep - but we're not allowed to say our own speakers are any good! I would characterise the difference as being that the sealed speakers give 'dry' bass, whereas the ported ones may superficially sound more interesting(?) but lead to listener fatigue. Maybe.
If people can hear the differences between cables etc. then surely the rather large differences between sealed and ported speakers should be of some significance..? If size is no object, shouldn't the enthusiast just build big sealed boxes, rather than adding yet more dimensions to the problem that can't so easily be 'tweaked'?
If people can hear the differences between cables etc. then surely the rather large differences between sealed and ported speakers should be of some significance..? If size is no object, shouldn't the enthusiast just build big sealed boxes, rather than adding yet more dimensions to the problem that can't so easily be 'tweaked'?
Our youth
Just got a pair of EV Royal 400s which are a polystyrene cone 18 in a closed box, an 8" whizzer mid and the familiar horn tweeter. Bass driver measures 15hz free air, 42 in the box. Haven't listened to it yet but it could be pretty good in a bigger box. This enclosure is one of the worst I've seen from an established company; the midrange mounting is laughable and the buzzing from low power tests with the signal generator calls for some mods right away.
It was cheap, so like expensive cables it won't sound good until I dump some money into it. It's 50 years old!
Just got a pair of EV Royal 400s which are a polystyrene cone 18 in a closed box, an 8" whizzer mid and the familiar horn tweeter. Bass driver measures 15hz free air, 42 in the box. Haven't listened to it yet but it could be pretty good in a bigger box. This enclosure is one of the worst I've seen from an established company; the midrange mounting is laughable and the buzzing from low power tests with the signal generator calls for some mods right away.
It was cheap, so like expensive cables it won't sound good until I dump some money into it. It's 50 years old!
Correct, though done right one normally needs multiple drivers plus frequency shaping EQ to keep various distortions vanishingly low and still have sufficient dynamic headroom.
GM
A sealed box may sound better, but the B6 is 7dB more efficient.
For a vented box the SBB4 does sound the best.
For a vented box the SBB4 does sound the best.
Have a google for the term "group delay" because if you can wrap your head around that, it very nicely encapsulates the difference in outcomes between the two approaches. It's a description of the time delay between multiple frequencies, and it is the "extra parameter" you were looking for in trying to quantify subwoofer performance. It's not enough to have a flat frequency response, the phase response should also be as linear as possible, i.e. we should minimise group delay for good transient response.
Consider a kick drum - you stand in front of it and you feel the kick in your sternum; that is a transient. It's basically a square wave of signal which contains a very broad range of frequencies from sub-20Hz to well up past 100Hz and if you know your maths, you know that a square wave is composed of a bunch of odd (1, 3, 5, 7, 9 etc) harmonics. If there is little or no group delay between the drum and you, the sharp edge (wall of air) arrives nicely coordinated and you still feel the punch in the chest.
With significant group-delay, the different frequencies are differently delayed and the edge no longer arrives in a coordinated fashion. The 5th harmonic will arrive, then the 3rd, then the fundamental, with the result that the pulse of air is smeared out into a rumble. There's a loud sound with the right spectral content (the right frequencies are present in the right quantities) but the phase (timing) errors mean that it's smeared out and loses its impact.
Play that kick-drum through a sealed sub system and it's still going to kick you. Put it through a ported system and though the sound level might be greater, there isn't the solidity of a single coordinated slap in the chest.
If you're playing organ music or something, the only thing you'll hear is that the ported box is louder lower, but if your music contains a lot of drums, the ported box will lack impact. The low/loud aspect means that ported boxes are well suited to home theatre and making explosion noises though.
I would recommend going into a home theatre showroom, tell the salesdroid you've got $1000 to spend on a sub and you want to hear both ported and sealed options. Ask to hear both an action-movie soundtrack and some drumming music.
hope that helps clear up the subjective terms a bit...
edit: for an even more-extreme approach, there are things like 4th-order bandpass. They can produce extremely low frequencies extremely loudly, but have horrific transient response. I built a pair when I was a little more clueless and while it was flat within about 1dB from 10Hz to 70Hz, it had zero punch. You could get tones out of it and that was it. OK for movies, OK for some forms of electronic music but pretty sad otherwise. They gather dust now.
edit 2: here's a reasonable group delay search
Consider a kick drum - you stand in front of it and you feel the kick in your sternum; that is a transient. It's basically a square wave of signal which contains a very broad range of frequencies from sub-20Hz to well up past 100Hz and if you know your maths, you know that a square wave is composed of a bunch of odd (1, 3, 5, 7, 9 etc) harmonics. If there is little or no group delay between the drum and you, the sharp edge (wall of air) arrives nicely coordinated and you still feel the punch in the chest.
With significant group-delay, the different frequencies are differently delayed and the edge no longer arrives in a coordinated fashion. The 5th harmonic will arrive, then the 3rd, then the fundamental, with the result that the pulse of air is smeared out into a rumble. There's a loud sound with the right spectral content (the right frequencies are present in the right quantities) but the phase (timing) errors mean that it's smeared out and loses its impact.
Play that kick-drum through a sealed sub system and it's still going to kick you. Put it through a ported system and though the sound level might be greater, there isn't the solidity of a single coordinated slap in the chest.
If you're playing organ music or something, the only thing you'll hear is that the ported box is louder lower, but if your music contains a lot of drums, the ported box will lack impact. The low/loud aspect means that ported boxes are well suited to home theatre and making explosion noises though.
I would recommend going into a home theatre showroom, tell the salesdroid you've got $1000 to spend on a sub and you want to hear both ported and sealed options. Ask to hear both an action-movie soundtrack and some drumming music.
hope that helps clear up the subjective terms a bit...
edit: for an even more-extreme approach, there are things like 4th-order bandpass. They can produce extremely low frequencies extremely loudly, but have horrific transient response. I built a pair when I was a little more clueless and while it was flat within about 1dB from 10Hz to 70Hz, it had zero punch. You could get tones out of it and that was it. OK for movies, OK for some forms of electronic music but pretty sad otherwise. They gather dust now.
edit 2: here's a reasonable group delay search
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Some great posts in this thread to help us newbies understand things, thank you all! 🙂
Would I be correct in thinking that, going from the above, one would need to minimise cone mass and maximise (and linearise as far as possible) magnet motor force (BL?) to ensure that the cone responds (moves) as quickly and as accurately as possible to the signal being input, and hence give good transient response and 'articulation'?
Is this why drivers with smaller diameter (and, one presumes, lighter) cones have traditionally been seen as 'fast', whereas bigger drivers have been seen as 'slow' (an argument which ignores the larger motor that will be on the back of the larger driver in most cases)?
Why/How is it that the higher frequency harmonics 'arrive' before the fundamental?
If the speed of sound is constant in a given atmosphere, is it just the fact that the higher frequency waves hit their first peak quicker (because the wavelengths are shorter and the peak, therefore, does not take so long to be reached) and the lower, fundamental frequency therefore sounds 'slower'?
Or is that the talk of a foolish layman?! 😕
Would I be correct in thinking that, going from the above, one would need to minimise cone mass and maximise (and linearise as far as possible) magnet motor force (BL?) to ensure that the cone responds (moves) as quickly and as accurately as possible to the signal being input, and hence give good transient response and 'articulation'?
Is this why drivers with smaller diameter (and, one presumes, lighter) cones have traditionally been seen as 'fast', whereas bigger drivers have been seen as 'slow' (an argument which ignores the larger motor that will be on the back of the larger driver in most cases)?
Thanks for a great explanation of Group Delay - I kind of had it clear in my head but this has helped a lot 🙂
Why/How is it that the higher frequency harmonics 'arrive' before the fundamental?
If the speed of sound is constant in a given atmosphere, is it just the fact that the higher frequency waves hit their first peak quicker (because the wavelengths are shorter and the peak, therefore, does not take so long to be reached) and the lower, fundamental frequency therefore sounds 'slower'?
Or is that the talk of a foolish layman?! 😕
I think of bass reflex as a poor mans woofer. The optimal box is significantly larger than for a closed box design. If the port is tuned properly and the resonant frequency of the driver doesn't shift much over time, you get another maybe octave of bass, which is delayed by both the crossover network phase shift, and the mechanics of the port. Damping is good at the tuned port frequency, but mechanically weak on either side of that frequency, so ringing is more likely, which may mean more effective delay of the signal and muddy bass.
The way I like to make bass is with a closed box with an active EQ circuit (and active crossover - 4th order) ahead of the poweramp. Then you get tight flat bass down to whatever the cone area and desired SPL level can produce. In my living room, two 12 inch Peerless XXLS woofers in small cube shaped closed boxes give me plenty of juicy bass, flat down to 20HZ. Each woofer has 120watts rms driving it. The system as a whole is triamp'd with X = 100HZ/1.4kHZ. In a bigger room I might add 2 more of these 12 inch woofer cubes (just parallel them onto the first pair), but I don't do super loud music anymore. It goes louder than I ever want as is.
Having said all of this, I have heard some bass reflex systems that sounded very nice. We're not as sensitive to bass distortion as we are distortion in the upper frequencies. Bass extension though, makes drums sound much better, and overall system warmth really comes to life.
The way I like to make bass is with a closed box with an active EQ circuit (and active crossover - 4th order) ahead of the poweramp. Then you get tight flat bass down to whatever the cone area and desired SPL level can produce. In my living room, two 12 inch Peerless XXLS woofers in small cube shaped closed boxes give me plenty of juicy bass, flat down to 20HZ. Each woofer has 120watts rms driving it. The system as a whole is triamp'd with X = 100HZ/1.4kHZ. In a bigger room I might add 2 more of these 12 inch woofer cubes (just parallel them onto the first pair), but I don't do super loud music anymore. It goes louder than I ever want as is.
Having said all of this, I have heard some bass reflex systems that sounded very nice. We're not as sensitive to bass distortion as we are distortion in the upper frequencies. Bass extension though, makes drums sound much better, and overall system warmth really comes to life.
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Bob, not only are we in total agreement about woofer design, but we're not all that far apart geographically...
My living room system includes 4 10" Dayton woofers, with 4th order crossover and eq to 30Hz...
Yes, it goes louder than I ever had a need to play it.
My living room system includes 4 10" Dayton woofers, with 4th order crossover and eq to 30Hz...
Yes, it goes louder than I ever had a need to play it.
1.In the real world, thin light (non exotic material) cones are a problem for high SPL LF reproduction as they flex, causing distortion.
2.Given the same magnet structure and voice coil (a common occurrence) a larger, heavier cone driver will not have as good transient response as the lighter driver, and maybe perceived as "slow".
3.All crossover and equalization filters impart phase shift (delay) to any signal passing through them.
All loudspeakers are acoustic filters that also create signal delay.
Since the rolloff of high frequency of a low frequency transducer is inevitable, it requires the acoustic position of the woofer to lie behind the physical location at an inverse function of the high frequency cut off.
Even a sealed front loaded woofer will exhibit phase lag at low frequencies, the only way around it is with FIR filters, which require long delay times for the LF to "catch up" to the HF.
Tom Danley (long ago )wrote:
"In the 15 1/2 years I have been measuring drivers with a TEF machine I
have never seen a driver alone that had more than -80 degrees of phase
shift, most are more like + - 30 to 60 deg. Point sources (if they have
a flat response) are constant acceleration devices.
The acceleration force is NOT the voltage input to the system but rather
the current and so the acoustic phase mirrors the phase of the current.
The moving mass of the system appears as capacitive reactance and hence
the 1 pole filter (of the velocity) is realised that is needed to offset
the changing radiation resistance vs frequency. In theory this would
yield a 90 deg phase shift but it is never that much in practice.
What makes real world things more complicated is the effect of
additional reactances in the system, for example in a sealed box the
driver has a leading phase below resonance, at resonance it is at zero
degrees and above resonance it is lagging (capacitive reactance). As the
frequency is increased, one reaches a point where the series inductance
and the motional reactance form a conjugate and the phase is again zero
degrees (this is the R-min point in the impedance curve). Above this
frequency the phase leads (inductive reactance). The actual acoustic
phase is typically no more than 40-60 deg either way due to the additional
effects and as you can see is at times leading, lagging and resistive
depending where one is in frequency.
Any input signal you can think of can be broken it its equivalent
frequency components, when fed into a driver those frequency components
are reproduced at an amplitude and phase according to the drivers
amplitude and phase response at those frequencies.
In other words, for example a simple step function, the instantanious
change in input signal when reproduced is limited in rise time by the
drivers high frequency response and the low frequency response governs
how long (along with x-max) it can remain a straight line.
How well it can reproduce the wave shape is both a function of its
amplitude and phase response."
Simple as that 🙂.
Art
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Hi,
A sealed alignment can be far more boomy than a tight vented alignment
though for ultimate "tightness" (and no bass) you can't beat sealed and
for ultimate amounts of bass (and no tightness) you can't beat vented.
In the end most drivers suit sealed or vented. for those that suit both
your usually looking at vented being twice the internal volume of sealed.
Eq'd sealed is superior in all respects except for SPL capabilities and it
is the latter that makes vented difficult to ignore. e.g. a single 10"
vented to 30Hz will do 30Hz at the same level as 4x10" sealed.
Hence PA systems and the like always go vented. At home I
have lot of sympathy for two opposed sealed drivers in the
same volume as a single driver vented, for overall performance.
rgds, sreten.
A sealed alignment can be far more boomy than a tight vented alignment
though for ultimate "tightness" (and no bass) you can't beat sealed and
for ultimate amounts of bass (and no tightness) you can't beat vented.
In the end most drivers suit sealed or vented. for those that suit both
your usually looking at vented being twice the internal volume of sealed.
Eq'd sealed is superior in all respects except for SPL capabilities and it
is the latter that makes vented difficult to ignore. e.g. a single 10"
vented to 30Hz will do 30Hz at the same level as 4x10" sealed.
Hence PA systems and the like always go vented. At home I
have lot of sympathy for two opposed sealed drivers in the
same volume as a single driver vented, for overall performance.
rgds, sreten.
In large scale situations like PA systems for rock bands or anything outdoors it is arguable that ported boxes may be better. You get a little bit more SPL at the low end per watt, at the expense of tightness and accuracy. Boominess (usually caused by cancellations in the 70HZ - 300HZ region) is almost certainly a function of room acoustics rather than whether it's a ported or sealed enclosure type. If you experienced a difference in boominess, there were probably other variables at play.
I think I've heard your name somewhere. Do you know Matt Kamna? I bet you know about the Oregon Triode Society. Next meeting is also a swap meet, in case you have a bunch of old stuff to trade or sell.
Speed of sound is constant, but the different frequencies take paths of different lengths to reach you. The higher frequencies directly radiate from the cone but the lower frequencies are the constructive sum of radiation from both the cone and the port.
When a square wave arrives, the high frequencies head straight for you but you'll have to wait a cycle or so for the lower frequencies to travel through the box and port and begin reinforcing with the wave from the cone. That's grossly oversimplifying it because the air in the box causes frequency-dependent phase shifts (delays) too, but just thinking about path-length differences gets you most of the way to visualizing the smearing.
Practically speaking, the 'punch' from a kick drum comes from the midrange.
If you take a Klipschorn and play some music at a level where the kick drum is hitting you in the chest, and then pull the fuse for the midrange driver, the bass cabinet (which runs up to 400hz) by itself has no 'punch'.
It should also be pointed out that there is a large amount of delay in the Klipschorn that varies wildly with frequency.
If you take a Klipschorn and play some music at a level where the kick drum is hitting you in the chest, and then pull the fuse for the midrange driver, the bass cabinet (which runs up to 400hz) by itself has no 'punch'.
It should also be pointed out that there is a large amount of delay in the Klipschorn that varies wildly with frequency.
When I listened to my first PP-sub it was a dipole but with AE IB15 so silly excursion capability I went "huh? so that's what 30 hz really sounds like?".
All the other subs and speakers I've listened to has had way much distortion in the bass, since as can be realized in an Equal-loudness contour even 10% 2nd order distortion at 30 hz will be heard as 100 %. The PP IB15 made me realize that there was actually very little musical content down below 40 hz and thus my IB15 had much more output capability than I needed so I sold them and stepped down to 10" drivers instead =)
Re - driver with a Qts=3.12
Sorry for the delay in replying, but i only logged back in today !
I thought so 😉 Regards
Sorry for the delay in replying, but i only logged back in today !
I thought so 😉 Regards
Perhaps estranged car audio speak 😉
Have an experiment going on with an MLTL and the best descript would be tight punch from my old school speak. Am limiting bandwidth of this diver to 189Hz LR4 atm tho it does extend flat to 2.5k (6.5") and with not so bad breakup 4-5k. If allowed to be run higher (hair over 2k) rimshots are articulate. High passed @27 LR8 to limit excursion. Nearfield the design rolls off nicely at 6dB/oct below 40 with a knee @ ~21Hz where it drops to 12dB/oct.
Good bite down low, into the mid 30's, albeit a peak @48Hz (boom) and a complete suckout at ~23/27Hz due to the shape and a hallway. Not a thing can be done to fix this room null issue, which blows. Hard to get good distortion readings when the room goes nuts at elevated levels, which happens to be about anything above 90dB. 🙁
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