Many of you have listened to both vented boxes and tapped horns. Would you care to list the reasons you like the sound of one versus the other? And would you speculate on why this is?
Here's the reason I bring this up:
I've built subs for about 20 years. Over that span, the one sub that I'm really happy with is my TH-Mini 'clone.' I've built a LOT of bandpass boxes, but I've never managed to build one that didn't sound sluggish, at least to a degree. Probably the most successful bandpass box I've built was one that was part of a multi-sub Geddes type setup, where the BP boxes deep extension complemented the Mini's lack thereof.
But by itself, I've never built a bandpass that was satisfying.
I've built a handful of vented subs. Not entirely sure why I've shied away from them, perhaps they're too simple? Can't say I was completely unhappy with them, but horn subs seem more 'fun' for DIY.
I've built a few sealed subs, but shied away from them because the Mini's output seems 'effortless' compared to the sealed subs. Perhaps lower distortion?
Now the obvious solution would be to stick with tapped horns. But my main gripe with those is SIZE. The Geddes multi-sub approach really sounds great, but I can't afford the space for three huge tapped horns. So I'm considering a vented box instead.
I've studied all the literature exhaustively, and I'm really struggling to understand why the tapped horns sound good. Here's a list of ideas I've had; would be curious if some of you who've built both types would chime in.
1) Personally, I prefer the sound of my TH-Mini to the sound of *all* the bandpass boxes I've built. Every time I've tried to integrate a bandpass box with one of my systems, it's felt like the bass is 'out of sync' with everything else.
Theoretically, a horn should have superior phase response to a vent, because the output of the vent is 180 degrees out of phase, while the output of a horn is just 90.
Unfortunately, I don't this this tells the whole story. It's not as simple as "horns are superior to ports."
For instance, in the measurements of the Rhythmik vented box and the Danley DTS-10 tapped horn, we see that the tapped horn has huge spikes in the group delay curve at 55hz and 102hz.
Here are some ideas I'm kicking around, on why tapped horns sound so good. These are only hypotheses, and I'd love to get some opinions on what you think of YOUR tapped horns.
Idea 1 : Tapped Horns sound good because the phase distortions are harmonic.
If you would, take a moment and think about a drum beat. The beat will have a fundamental at a specific frequency, along with harmonics. For instance, a 40hz drum beat will have harmonics at 80hz, 120hz, 160hz, etc.
My 'hunch' is that tapped horns may sound good because their problems are harmonic. For instance, the Danley DTS-10 has a big spike in the group delay curve at 55hz, but it's mirrored by a spike about one octave higher. So if there's a drum 'whack' at 55hz, it's harmonics will *also* be delayed.
This is different than the vented or bandpass boxes, where the phase shift is centered on one frequency. For instance, in a bandpass box tuned to 40hz the group delay at 40hz will be *significantly* higher than the group delay at 80hz. Perhaps this explains why bp boxes sound 'slow' to me?
Also, note that the amount of harmonic correlation between the peaks is related to the asymmetry of the woofers distance from the throat and the mouth. In other words, if the woofer in your tapped horn is very far from the mouth, but very close to the throat, the peaks will be *less* harmonic. And if you're going to have these distortion, it's probably better that they're harmonic rather than NOT harmonic. (IE, it's better to have a peak in the group delay at 40 and 80hz than at 33hz and 80hz, because music itself is harmonic. Unless you don't listen to music on your subs
)
Idea 2 : Tapped Horns sound good because they have low harmonic distortion.
I'd love it if it were this simple. That tapped horns sound good because they have low distortion. I'm not 100% convinced that this is why they sound good however.
For instance, I once built a tapped horn with multiple woofers, then converted the same sub to push-pull. The push pull sub sounded cleaner. But the problems that I hear with bandpass subs don't have to do with them sounding grungey; it has to do with them sounding sluggish.
(Note that the distortion that I reference in idea 1 is distortion in the group delay curve; the distortion that I reference in idea 2 is the type of distortion we're most accustomed to discussing, which is distortion in the frequency response curve of the sub.
Idea 3 - I've just been using crummy ports
This is an idea I'm really excited about. The idea that my bandpass boxes sounded bad not because of a fundamental problem with the box type, but due to the use of crummy ports.
There's a JBL paper which gets into the details on this. It's a very good read. We find that:
1) As you increase the power on a ported speaker the port frequency changes. Which means that the frequency response of ported speaker changes with volume. And this affects *all* speakers with ports, including the bandpass types.
2) I was surprised to see that ports generate harmonic distortion. I didn't know this, in my mind I imagined that the port output was basically the frequency it's tuned to, and that's it.
3) Possibly the most frustrating aspect of the paper is that there isn't one 'perfect' port design; you really have to optimize the port for the application. (IE, a high power port behaves differently than a low-distortion port.)
4) I was really surprised to see how little power it took to make the port start misbehaving. Particularly since I routinely used 500-1000 watts in my car subs. If I'm reading the literature right, a ported box with a port that's too small basically works WORSE than a sealed box at high power.
5) The bigger the port, the better. And flares generally help.
6) One of the odder findings was that you could reduce distortion by baffling the port *inside* the box. I've never seen this done. It might explain why some prefer the sound of slot ported subs.
Long story short - perhaps tapped horns sound good because they're a lot like a vented box where the port is so big, the woofer is literally sitting in the port.
Here's the reason I bring this up:
I've built subs for about 20 years. Over that span, the one sub that I'm really happy with is my TH-Mini 'clone.' I've built a LOT of bandpass boxes, but I've never managed to build one that didn't sound sluggish, at least to a degree. Probably the most successful bandpass box I've built was one that was part of a multi-sub Geddes type setup, where the BP boxes deep extension complemented the Mini's lack thereof.
But by itself, I've never built a bandpass that was satisfying.
I've built a handful of vented subs. Not entirely sure why I've shied away from them, perhaps they're too simple? Can't say I was completely unhappy with them, but horn subs seem more 'fun' for DIY.
I've built a few sealed subs, but shied away from them because the Mini's output seems 'effortless' compared to the sealed subs. Perhaps lower distortion?
Now the obvious solution would be to stick with tapped horns. But my main gripe with those is SIZE. The Geddes multi-sub approach really sounds great, but I can't afford the space for three huge tapped horns. So I'm considering a vented box instead.
I've studied all the literature exhaustively, and I'm really struggling to understand why the tapped horns sound good. Here's a list of ideas I've had; would be curious if some of you who've built both types would chime in.
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1) Personally, I prefer the sound of my TH-Mini to the sound of *all* the bandpass boxes I've built. Every time I've tried to integrate a bandpass box with one of my systems, it's felt like the bass is 'out of sync' with everything else.
Theoretically, a horn should have superior phase response to a vent, because the output of the vent is 180 degrees out of phase, while the output of a horn is just 90.
Unfortunately, I don't this this tells the whole story. It's not as simple as "horns are superior to ports."
For instance, in the measurements of the Rhythmik vented box and the Danley DTS-10 tapped horn, we see that the tapped horn has huge spikes in the group delay curve at 55hz and 102hz.
Here are some ideas I'm kicking around, on why tapped horns sound so good. These are only hypotheses, and I'd love to get some opinions on what you think of YOUR tapped horns.
Idea 1 : Tapped Horns sound good because the phase distortions are harmonic.
If you would, take a moment and think about a drum beat. The beat will have a fundamental at a specific frequency, along with harmonics. For instance, a 40hz drum beat will have harmonics at 80hz, 120hz, 160hz, etc.
My 'hunch' is that tapped horns may sound good because their problems are harmonic. For instance, the Danley DTS-10 has a big spike in the group delay curve at 55hz, but it's mirrored by a spike about one octave higher. So if there's a drum 'whack' at 55hz, it's harmonics will *also* be delayed.
This is different than the vented or bandpass boxes, where the phase shift is centered on one frequency. For instance, in a bandpass box tuned to 40hz the group delay at 40hz will be *significantly* higher than the group delay at 80hz. Perhaps this explains why bp boxes sound 'slow' to me?
Also, note that the amount of harmonic correlation between the peaks is related to the asymmetry of the woofers distance from the throat and the mouth. In other words, if the woofer in your tapped horn is very far from the mouth, but very close to the throat, the peaks will be *less* harmonic. And if you're going to have these distortion, it's probably better that they're harmonic rather than NOT harmonic. (IE, it's better to have a peak in the group delay at 40 and 80hz than at 33hz and 80hz, because music itself is harmonic. Unless you don't listen to music on your subs
)Idea 2 : Tapped Horns sound good because they have low harmonic distortion.
I'd love it if it were this simple. That tapped horns sound good because they have low distortion. I'm not 100% convinced that this is why they sound good however.
For instance, I once built a tapped horn with multiple woofers, then converted the same sub to push-pull. The push pull sub sounded cleaner. But the problems that I hear with bandpass subs don't have to do with them sounding grungey; it has to do with them sounding sluggish.
(Note that the distortion that I reference in idea 1 is distortion in the group delay curve; the distortion that I reference in idea 2 is the type of distortion we're most accustomed to discussing, which is distortion in the frequency response curve of the sub.
Idea 3 - I've just been using crummy ports
This is an idea I'm really excited about. The idea that my bandpass boxes sounded bad not because of a fundamental problem with the box type, but due to the use of crummy ports.
There's a JBL paper which gets into the details on this. It's a very good read. We find that:
1) As you increase the power on a ported speaker the port frequency changes. Which means that the frequency response of ported speaker changes with volume. And this affects *all* speakers with ports, including the bandpass types.
2) I was surprised to see that ports generate harmonic distortion. I didn't know this, in my mind I imagined that the port output was basically the frequency it's tuned to, and that's it.
3) Possibly the most frustrating aspect of the paper is that there isn't one 'perfect' port design; you really have to optimize the port for the application. (IE, a high power port behaves differently than a low-distortion port.)
4) I was really surprised to see how little power it took to make the port start misbehaving. Particularly since I routinely used 500-1000 watts in my car subs. If I'm reading the literature right, a ported box with a port that's too small basically works WORSE than a sealed box at high power.
5) The bigger the port, the better. And flares generally help.
6) One of the odder findings was that you could reduce distortion by baffling the port *inside* the box. I've never seen this done. It might explain why some prefer the sound of slot ported subs.
Long story short - perhaps tapped horns sound good because they're a lot like a vented box where the port is so big, the woofer is literally sitting in the port.
Here's some info from Geddes on bandpass subs:
Bandpass subwoofers and Geddes' design
"The response given above was basically correct, a bandpass does put a resonance chamber on the front of a closed box loudspeaker and this does increase the efficiency. It is a fairly narrow band design, which is fine for a sub, but I don't give any importance to group delay at LFs in small rooms.
They are hard to get working correctly, I will agree with that, but I have had a lot of experience with them so I can seem to make them work.
They are "passive" in that the amps are external. I have not found plate amps to be reliable and they are too limited in the controls. I recommend a DCX2496 and some rack amps for the LF subs.
I also don't worry too much about "frequency response" of a sub because the room changes it completely anyways. How the subs work in the room at the choosen location is what matters and this is far more determined by the room and placement than by any free field measurement of the subs. In the end the sub gets EQ'd all over the place anyways. What IS required is a great deal of linear output capability and bandpass does this when a robust driver is used. I measure this as a near field measurement of the output, but not anything free field.
I used multiple ports because there was no place to put one. Large areas require long lengths, but a small area has too much turbulence, noise and distortion. So I needed to devide the poart into smaller pieces that would fit.
The sub is about 18 x 16 x 14 inches and weighs about 45 lbs.
Bandpass subwoofers and Geddes' design
"The response given above was basically correct, a bandpass does put a resonance chamber on the front of a closed box loudspeaker and this does increase the efficiency. It is a fairly narrow band design, which is fine for a sub, but I don't give any importance to group delay at LFs in small rooms.
They are hard to get working correctly, I will agree with that, but I have had a lot of experience with them so I can seem to make them work.
They are "passive" in that the amps are external. I have not found plate amps to be reliable and they are too limited in the controls. I recommend a DCX2496 and some rack amps for the LF subs.
I also don't worry too much about "frequency response" of a sub because the room changes it completely anyways. How the subs work in the room at the choosen location is what matters and this is far more determined by the room and placement than by any free field measurement of the subs. In the end the sub gets EQ'd all over the place anyways. What IS required is a great deal of linear output capability and bandpass does this when a robust driver is used. I measure this as a near field measurement of the output, but not anything free field.
I used multiple ports because there was no place to put one. Large areas require long lengths, but a small area has too much turbulence, noise and distortion. So I needed to devide the poart into smaller pieces that would fit.
The sub is about 18 x 16 x 14 inches and weighs about 45 lbs.
Phase, Time and Distortion in Loudspeakers
Some good info on group delay from a great site.
"Group delay refers to the delay experienced by one group of frequencies with respect to another. All filters, including loudspeaker enclosures, introduce group delay in the audio signal. To gain a basic understanding, imagine a system where the treble is delayed by (say) 30 seconds after the midrange. That this would be very audible and highly disconcerting is obvious. That is the essence of group delay, and fortunately no audio product will be as bad as the example.
It would be very nice to know the threshold of audibility of group delay with respect to frequency, but this remains an area where not a great deal seems to have been done. No extensive data is available and so far, the best table is from Blauert and Laws ...
Frequency Threshold
500Hz 3.2 ms
1kHz 2 ms
2kHz 1 ms
4kHz 1.5 ms
8kHz 2 ms
Table 5 - Group Delay Audibility Thresholds
Given that the minimum audible group delay is claimed to be 1ms at 2kHz, that amounts to a physical driver displacement of 345mm - assuming the velocity of sound to be 345m/s (22°C at sea level). No (sensible) speaker system will ever have that much delay, so for the most part group delay should not cause any audible problems.
One area that is of some concern is bass. The table doesn't show anything below 500Hz, but comments about "slow bass" can be found all over the Net and in magazines etc. It seems probable that some bass alignments do indeed exceed the threshold of audibility, and this would account for the comments. Bandpass enclosures in particular seem to suffer from the slow bass syndrome, with people commenting that the bass is "a day late" . I think we can safely assume that this is a slight exaggeration, but these enclosures do seem to exhibit characteristics that would explain the idea of slow bass. Since bass in isolation cannot be fast, the only answer is that it is delayed compared to the rest of the system.
It is not unusual for even a vented box to have a group delay of perhaps 20-30ms, and while a tad shy of a day, it's still quite a long time in audio reproduction. By comparison, a 24dB/octave Linkwitz Riley crossover network has a group delay of 480us (see table).
Some good info on group delay from a great site.
"Group delay refers to the delay experienced by one group of frequencies with respect to another. All filters, including loudspeaker enclosures, introduce group delay in the audio signal. To gain a basic understanding, imagine a system where the treble is delayed by (say) 30 seconds after the midrange. That this would be very audible and highly disconcerting is obvious. That is the essence of group delay, and fortunately no audio product will be as bad as the example.
It would be very nice to know the threshold of audibility of group delay with respect to frequency, but this remains an area where not a great deal seems to have been done. No extensive data is available and so far, the best table is from Blauert and Laws ...
Frequency Threshold
500Hz 3.2 ms
1kHz 2 ms
2kHz 1 ms
4kHz 1.5 ms
8kHz 2 ms
Table 5 - Group Delay Audibility Thresholds
Given that the minimum audible group delay is claimed to be 1ms at 2kHz, that amounts to a physical driver displacement of 345mm - assuming the velocity of sound to be 345m/s (22°C at sea level). No (sensible) speaker system will ever have that much delay, so for the most part group delay should not cause any audible problems.
One area that is of some concern is bass. The table doesn't show anything below 500Hz, but comments about "slow bass" can be found all over the Net and in magazines etc. It seems probable that some bass alignments do indeed exceed the threshold of audibility, and this would account for the comments. Bandpass enclosures in particular seem to suffer from the slow bass syndrome, with people commenting that the bass is "a day late" . I think we can safely assume that this is a slight exaggeration, but these enclosures do seem to exhibit characteristics that would explain the idea of slow bass. Since bass in isolation cannot be fast, the only answer is that it is delayed compared to the rest of the system.
It is not unusual for even a vented box to have a group delay of perhaps 20-30ms, and while a tad shy of a day, it's still quite a long time in audio reproduction. By comparison, a 24dB/octave Linkwitz Riley crossover network has a group delay of 480us (see table).
I wanted to throw in a piece of information that I haven't seen discussed in the debate about the audibility of group delay.
What if we discussed the delay in terms of music?
Here's what I mean by this. Let's say you are listening to a band that's playing a drum beat at a rate of 120 beats per minute. I would argue that nearly anyone could perceive if the beat varied by ten percent. IE, if the beat went from 120 beats per minute to 132 beats per minute, I'll bet you could perceive it. In fact, I wouldn't be surprised if you could perceive a difference of five beats per minute.
So how does that work out in milliseconds?
At 120 beats per minute, that is one beat every 8.3333 milliseconds. If you're listening to that band and you can perceive them shift from 120 to 132 beats per minute, than you're perceiving a change in beats from one beat every 8.3333 milliseconds to one beat every 7.5758 milliseconds.
That works out to a difference of just 0.758 milliseconds.(!!!)
That's quite short.
So...
Can we perceive a difference of 0.758 milliseconds? I'd argue that if you can hear a band shift from 120 to 132 beats per minute, then the answer is YES
Of course, the big "X Factor" here is harmonics. For instance, I've noticed that the harmonics of bass notes are far more apparent over headphones, where we're removing a huge number of variables out of this equation. (IE headphones eliminate the room, eliminate a crossover point, eliminate phase shift at xover, eliminate reflections, eliminates diffraction.)
What if we discussed the delay in terms of music?
Here's what I mean by this. Let's say you are listening to a band that's playing a drum beat at a rate of 120 beats per minute. I would argue that nearly anyone could perceive if the beat varied by ten percent. IE, if the beat went from 120 beats per minute to 132 beats per minute, I'll bet you could perceive it. In fact, I wouldn't be surprised if you could perceive a difference of five beats per minute.
So how does that work out in milliseconds?
At 120 beats per minute, that is one beat every 8.3333 milliseconds. If you're listening to that band and you can perceive them shift from 120 to 132 beats per minute, than you're perceiving a change in beats from one beat every 8.3333 milliseconds to one beat every 7.5758 milliseconds.
That works out to a difference of just 0.758 milliseconds.(!!!)
That's quite short.
So...
Can we perceive a difference of 0.758 milliseconds? I'd argue that if you can hear a band shift from 120 to 132 beats per minute, then the answer is YES
Of course, the big "X Factor" here is harmonics. For instance, I've noticed that the harmonics of bass notes are far more apparent over headphones, where we're removing a huge number of variables out of this equation. (IE headphones eliminate the room, eliminate a crossover point, eliminate phase shift at xover, eliminate reflections, eliminates diffraction.)
Patrick,
An adequate sized port will not change Fb enough to notice over the linear range of a speaker.
Tapped horns can have more output for a given excursion than BR, but also have more distortion for a given excursion.
Distortion sounds louder, and louder LF is becoming more and more usual, a 10-20 dB LF "haystack" below 100 Hz is not unusual any more.
You have seen baffling the port inside the box before in post #7 of this thread, and drew it yourself in #9:
http://www.diyaudio.com/forums/subwoofers/226235-featherweight-title-fight.html
Art
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You are getting the problem that Earl can ignore since he does not seem to listen to 120 BPM music, that woofer LF transient response can actually lag by several beats due to group delay.
Looking at the phase response of the Keystone TH using a BC18SW115-4 and a BR cabinet using the same speaker tuned to the same FB, we see they are 30 degrees apart at 125 Hz, but at 40 Hz, the BR is 180 degrees "behind" (210-30=180).
Assuming both are time aligned at a crossover point of 125 Hz, that lag of 1000 ms /40Hz =25 ms per cycle, one half cycle (180 degrees) is 12.5 ms, one beat at 80 B.P.M.
So the 40 Hz BR LF response is more than a beat slow compared to the TH LF at 120 BPM (8.33ms).
Since bandpass cabinets typically have around 180 degree phase shift near the upper bandpass, usually very close to the intended crossover frequency, the lag is even worse, and alignment is more of a compromise.
They "seem to work", but don't sound coherent.
Art
Attachments
Interesting choice of words, describing a speaker cabinet that requires as much as 10 times the power to achieve the same LF output as a tapped horn as "effortless"
Ronnie Coleman "effortlessly" lifts his weights.Interesting choice of words, describing a speaker cabinet that requires as much as 10 times the power to achieve the same LF output as a tapped horn as "effortless"
You've pretty much summed it up right here.
Pound for pound, a well designed and well built bass-reflex design will have the best balance of very good sound quality and extension, while having reasonable sensitivity. Horn (tapped, BPH, etc, etc) and bandpass designs will have higher sensitivity at the expense of sound quality and reduced bandwidth. Sealed and open baffle will have excellent quality at the expense of everything else.
Also, non-horn designs don't require electronic delay to time align with your main speakers.
Perhaps you have never heard a good and properly sized bass reflex sub? They are lots of bad ones around....
Pound for pound, a well designed and well built bass-reflex design will have the best balance of very good sound quality and extension, while having reasonable sensitivity. Horn (tapped, BPH, etc, etc) and bandpass designs will have higher sensitivity at the expense of sound quality and reduced bandwidth. Sealed and open baffle will have excellent quality at the expense of everything else.
Also, non-horn designs don't require electronic delay to time align with your main speakers.
Perhaps you have never heard a good and properly sized bass reflex sub? They are lots of bad ones around....
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Sorry, shouldn't one beat at 80 BPM be [(60 sec/min)*(1000 ms/sec)/ (80/min)] = 750 ms?
There's no way in heck that 80 bpm is 12.5 ms per beat - I've been to enough clubs and studied enough stopwatches.
In adjusting time alignment in a full active car audio setup, I found that changes of .1ms were audible in the sound stage when tweaking the tweeter vs. mid. For the sub vs. mid, .1ms increments are VERY noticeable on how natural and integrated the bass sounds.
In running stereo subs, I have found that if they are too far ahead of the mains, even by an inch or so, the bass will sound unnaturally quick and ahead of the music.
I personally think low order crossovers and time alignment are the most important factors in getting natural sounding bass, assuming there is nothing else massively wrong.
Do acoustical filters and electrical filters have the same effect on phase?
IE, I know that a passive or electronic filter will affect the phase of a loudspeaker.
And I understand that the phase shift that's present in single reflex bandpass is tied to the frequency response.
But what if you improved the frequency response? Do you improve the phase at the same time?
For instance, let's say I have a single reflex bandpass with a resonance of 60hz. It rolls off at 4th order, so there's 100dB of output at 60hz, 76db of output at 30hz, and 76db of output at 120hz.
If I EQ'd is so that the rolloff was 2nd order instead of 4th order, would the group delay go down as well?
With passive filters this is a bit impractical, but with mini DSP seems like you might be able to just 'dial it in.'
IE, I know that a passive or electronic filter will affect the phase of a loudspeaker.
And I understand that the phase shift that's present in single reflex bandpass is tied to the frequency response.
But what if you improved the frequency response? Do you improve the phase at the same time?
For instance, let's say I have a single reflex bandpass with a resonance of 60hz. It rolls off at 4th order, so there's 100dB of output at 60hz, 76db of output at 30hz, and 76db of output at 120hz.
If I EQ'd is so that the rolloff was 2nd order instead of 4th order, would the group delay go down as well?
With passive filters this is a bit impractical, but with mini DSP seems like you might be able to just 'dial it in.'
I would call any sub tuned to 60 hz a poor design, and adding the eq would only increase delay. The key is to move the tuning to below 40hz or preferably far lower, into the 20hz's. Which keeps the group delay really down where it is fully masked by room gain/resonance.
Then crossover as high as is reasonable. If you are time aligned and use low phase crossovers, you can cross well above 100hz, where there is minimal group delay from the sub, and you are above the onset of group delay from the main's mid-woofer. Last thing you want to do is put a crossover point where there is major group delay on one of the drivers.
This also takes a huge bass load off your mains, resulting in cleaner midrange.
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A couple of things that I have picked up generally over the years.
Bass wavelengths are huge and take sometime to propagate and produce a note to the ear but we can pick up the initial pressure quickly. We are much more sensitive to time related issues the higher in frequency they are though. Below 30Hz you can get away with a lot without much consequence. At 120Hz 2 octaves higher much much less. There can be delay, ringing, phase mismatch around the crossover region etc. delay can be compensated for and matched near the xover. Ringing on the other hand cannot be as easily fixed. However it takes a bit to be noticeable to me. The other big fly in the ointment is usually the room or space that the bass system ends up in will utterly dominate the resulting response and will play havoc in the time domain. Abrupt spikes in distortion around certain frequencies are more easily noticed to me than but still it takes quite a large amount of bass distortion to be audibly bad. Having very large amounts of headroom always sounds better to me. Also systems with smooth extended bandwidth on both ends usually sound better to me even after filtering is applied that rolls off the extra bandwidth.
Bass reflex sounds better the lower it is tuned. I'm talking at least 30hz or lower. Pushing the port ringing, high pass induced phase changes, etc. lower helps a lot. Below 30Hz the wavelengths are so long that any delay or ringing is doubtful to be audible unless truly bad. Again the higher in frequency the more sensitive we are to these issues. Also large ports that can prevent compression, tune shifting and air noise as much as possible are key. Watch out for the port resonances from a long pipe though. The worst bass reflex cabs I have heard were tuned 50Hz or higher.
Band pass typically is tuned higher in the 40-70 Hz range which puts the energy storage issues where it is more audible. BP usually has longer energy decay than BR also plus it is trickier to design well with many designs being cheap " thumper" units with limited bandwidth. Also the ports produce all of the output so they typically seem to have higher average airspeeds. On a positive note the natural acoustic filtering of harmonics can keep the distortion down.
Sealed or IB sound amazing and avoid many issues IF you can afford the required headroom needed for your app. Still the acoustic space largely dominates the result in the time domain.
Tapped horns in some ways are the opposite of bass reflex. The design results in large high q spikes in response which also have significant ringing associated with them. For example in the dts10 measurement posted the 54 Hz and 102hz ringing are clearly audible and give a boomy droning sound. There is tons of content in this region and if a kick drum fundamental is near the 54 Hz spike it is very noticeable. Also these spikes acoustically boost the harmonic distortion of lower frequencies that fall into the range of these spikes in response. This is not as noticeable to me as the ringing though which is clearly audible. Judging from a few other TH designs that I have seen measurements of it is a good guess that the lower the cabinet is tuned and the more undersized for the corner the worse these effects get. However the self damping in the design and driver play a role as well. So the dts10 which is tuned very low drags these issues down into the 50-100hz octave. IMHO it is best to keep TH's with an effective corner of 25Hz or higher to keep these issues above 100Hz and the xover for this reason. On the positive the efficiency, sensitivity and leveraging of the driver output are great. The distortion below the 5th horn harmonic (54Hz in the case of the dts10) is exceptionally low and coupled with the large amounts of deep bass headroom provide an effortless low bass presentation that is hard to match.
FLH's also have some ringing issues from the measurements I have seen especially when undersized as almost all are, but less than TH's. distortion performance is good but will also have some spikes if there are peaks in the response due to the horn loading. However the positives from a TH apply as well as the additional one of having a more extended and smoother useful bandwidth if designed well. A larger cabinet is required though.
I did do a comparison of the same TC sounds driver in a small sealed, small very low tuned bass reflex with passive radiators and the dts10 tapped horn and compared sensitivity, max output, impedance, etc. then I EQ'd each into the same base response as the sealed and compared output compression, distortion, etc...This was done to get a look at what the cab alignment is doing to the driver performance. I find it very interesting. The article is at my Data-Bass site.
Bass wavelengths are huge and take sometime to propagate and produce a note to the ear but we can pick up the initial pressure quickly. We are much more sensitive to time related issues the higher in frequency they are though. Below 30Hz you can get away with a lot without much consequence. At 120Hz 2 octaves higher much much less. There can be delay, ringing, phase mismatch around the crossover region etc. delay can be compensated for and matched near the xover. Ringing on the other hand cannot be as easily fixed. However it takes a bit to be noticeable to me. The other big fly in the ointment is usually the room or space that the bass system ends up in will utterly dominate the resulting response and will play havoc in the time domain. Abrupt spikes in distortion around certain frequencies are more easily noticed to me than but still it takes quite a large amount of bass distortion to be audibly bad. Having very large amounts of headroom always sounds better to me. Also systems with smooth extended bandwidth on both ends usually sound better to me even after filtering is applied that rolls off the extra bandwidth.
Bass reflex sounds better the lower it is tuned. I'm talking at least 30hz or lower. Pushing the port ringing, high pass induced phase changes, etc. lower helps a lot. Below 30Hz the wavelengths are so long that any delay or ringing is doubtful to be audible unless truly bad. Again the higher in frequency the more sensitive we are to these issues. Also large ports that can prevent compression, tune shifting and air noise as much as possible are key. Watch out for the port resonances from a long pipe though. The worst bass reflex cabs I have heard were tuned 50Hz or higher.
Band pass typically is tuned higher in the 40-70 Hz range which puts the energy storage issues where it is more audible. BP usually has longer energy decay than BR also plus it is trickier to design well with many designs being cheap " thumper" units with limited bandwidth. Also the ports produce all of the output so they typically seem to have higher average airspeeds. On a positive note the natural acoustic filtering of harmonics can keep the distortion down.
Sealed or IB sound amazing and avoid many issues IF you can afford the required headroom needed for your app. Still the acoustic space largely dominates the result in the time domain.
Tapped horns in some ways are the opposite of bass reflex. The design results in large high q spikes in response which also have significant ringing associated with them. For example in the dts10 measurement posted the 54 Hz and 102hz ringing are clearly audible and give a boomy droning sound. There is tons of content in this region and if a kick drum fundamental is near the 54 Hz spike it is very noticeable. Also these spikes acoustically boost the harmonic distortion of lower frequencies that fall into the range of these spikes in response. This is not as noticeable to me as the ringing though which is clearly audible. Judging from a few other TH designs that I have seen measurements of it is a good guess that the lower the cabinet is tuned and the more undersized for the corner the worse these effects get. However the self damping in the design and driver play a role as well. So the dts10 which is tuned very low drags these issues down into the 50-100hz octave. IMHO it is best to keep TH's with an effective corner of 25Hz or higher to keep these issues above 100Hz and the xover for this reason. On the positive the efficiency, sensitivity and leveraging of the driver output are great. The distortion below the 5th horn harmonic (54Hz in the case of the dts10) is exceptionally low and coupled with the large amounts of deep bass headroom provide an effortless low bass presentation that is hard to match.
FLH's also have some ringing issues from the measurements I have seen especially when undersized as almost all are, but less than TH's. distortion performance is good but will also have some spikes if there are peaks in the response due to the horn loading. However the positives from a TH apply as well as the additional one of having a more extended and smoother useful bandwidth if designed well. A larger cabinet is required though.
I did do a comparison of the same TC sounds driver in a small sealed, small very low tuned bass reflex with passive radiators and the dts10 tapped horn and compared sensitivity, max output, impedance, etc. then I EQ'd each into the same base response as the sealed and compared output compression, distortion, etc...This was done to get a look at what the cab alignment is doing to the driver performance. I find it very interesting. The article is at my Data-Bass site.
Originally Posted by weltersys
Assuming both are time aligned at a crossover point of 125 Hz, that lag of 1000 ms /40Hz =25 ms per cycle, one half cycle (180 degrees) is 12.5 ms, one beat at 80 B.P.M.
Art
Assuming both are time aligned at a crossover point of 125 Hz, that lag of 1000 ms /40Hz =25 ms per cycle, one half cycle (180 degrees) is 12.5 ms, one beat at 80 B.P.M.
You are correct, I followed Patrick's math error, though it is not the first time I made that error- a 25ms beat would be 2400 BPM, even faster than speed metalSorry, shouldn't one beat at 80 BPM be [(60 sec/min)*(1000 ms/sec)/ (80/min)] = 750 ms?
There's no way in heck that 80 bpm is 12.5 ms per beat - I've been to enough clubs and studied enough stopwatches.
Art
My eclipse CD8053 adjusts in .1ms increments, which provide clearly audible changes to soundstage and bass timing. Yes, with music.
I just built and setup a pair of stereo subs, they are very audibly sensitive to alignment with the mains, moving an inch makes a difference between wrong and right sounding bass integration.
I'd say that cold (no A-B comparison, with music) I could probably detect a mis-timing between a sub and midbass of greater than +.2ms or -.5ms on the sub, given a 100 hz crossover and no weird distortion issues. Advancing the sub is much more audible for obvious reasons.
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josh and turbo,
excellent posts. 27hz tuned sounded way better than 40hz. Sealing it off was not audibly faster, just less bass (like -6db on a 30hz slider on a 10 band eq).
Ported's less cone motion arounding tuning sounded better than 4 drivers sealed with eq (elf). Makes sence. The more cones move, the louder the harmonic distortion and higher junk too.
Danley uses 1/4 wave stubs is some of his tapped horns to lower the 1st 10db spike and lowering the ringing. Even then it probably is a bit audible.
I saw a post but can't remember where, thay said a push pull sounded better than a tapped horn.
454,
you'd be suprised what you can hear, like fractions of an inch using 24db LR crossover slopes. We can perceive a change due to the difference of integration with the highs, especially on transient percussive stuff. But an inch ? I'd say bs if i hadn't been moving around an 8" 2 way on the floor near a wall. inch made a decent difference.
Fast bass?
Slow bass?
Run a sub by itself, sealed vs ported. It all sounds like mud. if i remember, 18db 80hz low pass crossover had around 15ms of delay around 75hz and decreasing back to zero as you went lower towards dc. Nasty when you think about it, but the room will “ring down” slower than your sub at medium levels anyway.
Norman
excellent posts. 27hz tuned sounded way better than 40hz. Sealing it off was not audibly faster, just less bass (like -6db on a 30hz slider on a 10 band eq).
Ported's less cone motion arounding tuning sounded better than 4 drivers sealed with eq (elf). Makes sence. The more cones move, the louder the harmonic distortion and higher junk too.
Danley uses 1/4 wave stubs is some of his tapped horns to lower the 1st 10db spike and lowering the ringing. Even then it probably is a bit audible.
I saw a post but can't remember where, thay said a push pull sounded better than a tapped horn.
454,
you'd be suprised what you can hear, like fractions of an inch using 24db LR crossover slopes. We can perceive a change due to the difference of integration with the highs, especially on transient percussive stuff. But an inch ? I'd say bs if i hadn't been moving around an 8" 2 way on the floor near a wall. inch made a decent difference.
Fast bass?
Slow bass?
Run a sub by itself, sealed vs ported. It all sounds like mud. if i remember, 18db 80hz low pass crossover had around 15ms of delay around 75hz and decreasing back to zero as you went lower towards dc. Nasty when you think about it, but the room will “ring down” slower than your sub at medium levels anyway.
Norman
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