paulspencer said:
Here's another vote for room modes. I came across an interesting website the other day while searching for a way to reduce room problems.
rigid fiblerglass tests
I suspect the first two modes don't change much because they don't have any fiberglass in the middle of the room. It also may be because the absorbtion at these really low freqs is pretty low. I'll be dabbling in this a bit myself in the next month or so.
-Robert
That's the same conclusion as I get to so far, the more sense it makes to apply quite large delays.
Why?
Me too, just wright it the European way from now one. And when will you guys finally come using the metric system as well? Stop delaying the inevitable, YOU KNOW it's the most logical decision 😀
Mvg Johan
here is a nice article about slow/fast bass:
http://www.soundstage.com/maxdb/maxdb061999.htm
here is my opinion taken from my web page:
And one more thing. There is no such thing as slow or fast subwoofer. All subwoofers are inherently slow. Its the upper harmonics reproduced by midrange which makes bass sound fast or slow. Two subwoofers sound different for they have different frequency responses. If two subwoofers have the same frequency responses, horn loaded or not, they sound the same. If you appropriately cut off upper frequencies of "fast" subwoofer, it becomes "slow" subwoofer. Its the integration between woofer and midrange which determines how the bass will sound.The secret to match the sound of Lowthers with the sub is to cut off upper frequencies of subwoofer as steeply as possible. Some say it is not possible to match Lowthers with sub. I disagree. It takes highly efficient woofers and lots of patience, but it can be done. Do experiment with subs placement too, it makes a world of difference. If placed correctly with matching volume, sub will disappear. Sub should not be heard, noticed only, if you turn it off.
adason said:
What He Said. The integration happens *much* higher up than you might expect, too. I recall designing a set of stage monitors with a 15" and a horn driven by a JBL 2445 (you heard right, this was intended to compete with full-tilt Marshall stacks). In any event, something just didn't jive - kick drums and floor toms were there but not present, rather undifferentiated. Another guy surreptitiously threw in a slot tweeter crossed in at 8 or 10 kHz, and lo & behold the whole thing came together! The missing drums suddenly showed up in the mix.
Even though the supertweeter crossed in very high, they produced enough energy within an octave of the crossover that 6 kHz on up was flat instead of rolling off a few dB at 12 k. That was enough to make the drums come alive. I learned that response issues can have repercussions at completely different places in the spectrum.
Francois.
adason said:
I have two subs here that refute this. They are both 10 inch drivers in sealed cabinets, both flat to 25 Hz. Both fed from a Marchand XM-44, crossed over at 80 Hz, 4th-order L-R. Either is fine for HT. With music, the Mirage ES10 sounds slow, the Rocket UFW-10 sounds fast.
The obvious difference between the two is the cabinet. The Mirage is larger and lighter walled, and resonates too much (you can feel the bass working the cabinet.) Woofer quality also differs, and that may be a factor. Bypassing the Mirage's internal crossover helps make it sound better, but I think the cabinet is the big issue.
Note that this is with both subs optimally set up. As I stated previously, I can ruin the sound of either by twiddling any of the knobs (phase, XO frequency, amplitude, or eq).
Dan
i agree with you that you can have the same sub either fast or slow, but that is not inherently the sub causing it
obviosly by making all the adjustments you are changing the integration between the bass and midrange therefore the bass can be percieved as slow or fast based on this integration
please read this article again carefuly
http://www.soundstage.com/maxdb/maxdb061999.htm
For me "Fast" bass mean accurate well defined bass where if the recording is good you can hear the different instruments and "slow" bass is the opposite.
I don't think it has anything to do with extension. If I sit in a church with good acoustics and a great organ, when those lowest notes are played it doesn't seem slow to me, just low.
I agree the 3 primary causes of "slow" bass are:
Room Modes
Driver Alignment
Drivers
Room Modes is definitely a big cause, but I don't agree with equalizing out the peak to fix it. All that does is get rid of the peak in response. The mode is still there and is a big part of the response, so the time smear of the reflections mingled with the direct radiation leads to a lack of definition and clarity.
Ported and PR alignments are simply unable to provide the level of clarity in the bass region that I want. I'm not saying that they can't sound very good, but bass loses definition when you turn the cab into a resonating chamber via a port or PR whether it is for a subwoofer or not.
Most subwoofer drivers simply can't play well enough above 50-60hz to avoid messing up the sound of the bass. Crossing steeply and low can help a lot, but seamless integration is the hard part.
I used to think like many here do, get that flat response and extreme extension and "man this sounds good, feel that bass!". Then I started experimenting with dipole, mainly because my wife would complain about the volume when I'd listen to music or watch a late night action movie. Dipole was a real eye opener for what bass should sound like (at least to me). At first I thought it was the room effects, because how could 8 cheap, but musical, 12's sound better than my EBS Maelstrom with the ports stuffed? So I hauled everything outside, the dipole and my collection of 5 boxed subs. The lack of a room made a big difference, but the dipole still had more bass detail and a more natural sound. Since then I've been a boxless convert although I still want to try my hand at horns.
Then I start converting stuff to OB, but how am I going to get some good extension with reasonable SPL? Well I've got this pair of tempests waiting to be used, maybe I can use them up to 80 or 100hz without a box, so I give them a try on a temporary baffle....not no, but H3LL NO, the driver just can't do it. A pair of shivas was a little better, but not by much, so I tried everything I could get my hands on. That's when I realized that the only woofers that provided the bass detail I was looking for below 100hz were the ones that still sounded good up to 500hz or more.
To get back around to the topic, at the same time I started playing around with OB arrays. The first one sounded so good a friend asked me to build one for him. He didn't want to spend much on drivers so we used $1.50/ea 4" drivers that I used before. 12 per side plus 1 high efficiency tweeter, but what about the bass? We tried 16 more per side filtered for bass duty only and it just wasn't enough to keep up with the arrays in dipole, so we sealed them up and it worked great. The bass is every bit as good as my Maelstrom sealed and much better than my other boxed subs. He's quite happy and while it's no low end SPL champion he's got great full range sound for less than the cost of a single Maelstrom. I figure that it would take 300+ of those little drivers to get what I want in dipole. I doubt that I'll go that route, but I know it's doable. Cheap 5-8" drivers with a much lower Fs would be more efficient.
Sorry about being so long winded, but I felt I needed to explain the basis of my point of view that small drivers can be used to make better bass than typical subwoofers.
I don't think it has anything to do with extension. If I sit in a church with good acoustics and a great organ, when those lowest notes are played it doesn't seem slow to me, just low.
I agree the 3 primary causes of "slow" bass are:
Room Modes
Driver Alignment
Drivers
Room Modes is definitely a big cause, but I don't agree with equalizing out the peak to fix it. All that does is get rid of the peak in response. The mode is still there and is a big part of the response, so the time smear of the reflections mingled with the direct radiation leads to a lack of definition and clarity.
Ported and PR alignments are simply unable to provide the level of clarity in the bass region that I want. I'm not saying that they can't sound very good, but bass loses definition when you turn the cab into a resonating chamber via a port or PR whether it is for a subwoofer or not.
Most subwoofer drivers simply can't play well enough above 50-60hz to avoid messing up the sound of the bass. Crossing steeply and low can help a lot, but seamless integration is the hard part.
I used to think like many here do, get that flat response and extreme extension and "man this sounds good, feel that bass!". Then I started experimenting with dipole, mainly because my wife would complain about the volume when I'd listen to music or watch a late night action movie. Dipole was a real eye opener for what bass should sound like (at least to me). At first I thought it was the room effects, because how could 8 cheap, but musical, 12's sound better than my EBS Maelstrom with the ports stuffed? So I hauled everything outside, the dipole and my collection of 5 boxed subs. The lack of a room made a big difference, but the dipole still had more bass detail and a more natural sound. Since then I've been a boxless convert although I still want to try my hand at horns.
Then I start converting stuff to OB, but how am I going to get some good extension with reasonable SPL? Well I've got this pair of tempests waiting to be used, maybe I can use them up to 80 or 100hz without a box, so I give them a try on a temporary baffle....not no, but H3LL NO, the driver just can't do it. A pair of shivas was a little better, but not by much, so I tried everything I could get my hands on. That's when I realized that the only woofers that provided the bass detail I was looking for below 100hz were the ones that still sounded good up to 500hz or more.
To get back around to the topic, at the same time I started playing around with OB arrays. The first one sounded so good a friend asked me to build one for him. He didn't want to spend much on drivers so we used $1.50/ea 4" drivers that I used before. 12 per side plus 1 high efficiency tweeter, but what about the bass? We tried 16 more per side filtered for bass duty only and it just wasn't enough to keep up with the arrays in dipole, so we sealed them up and it worked great. The bass is every bit as good as my Maelstrom sealed and much better than my other boxed subs. He's quite happy and while it's no low end SPL champion he's got great full range sound for less than the cost of a single Maelstrom. I figure that it would take 300+ of those little drivers to get what I want in dipole. I doubt that I'll go that route, but I know it's doable. Cheap 5-8" drivers with a much lower Fs would be more efficient.
Sorry about being so long winded, but I felt I needed to explain the basis of my point of view that small drivers can be used to make better bass than typical subwoofers.
adason said:
Reading Doug Blackburn articles is not my idea of fun. I consider him a flake.
Nothing in the article addresses the differences in bass quality (bass speed) between the Mirage and the Rocket subs.
Dan
What if the ported response was tuned to be very close to a sealed alignment with the same woofer,could anyone tell it apart/ Theres a name for this phenomenon
The mere fact that people use hemholtz resonators to reach deeper induces worse quality...Pi aligning is the opposite to this.
An EQd sealed box could have the same quality problems as similar response ported box? I really dont see how people can hear the port itself - how can you be sure from unscientific in room listening tests.
Cheers!
Tuning a ported box in the infrasonic spectrum can yeild great results in my opinion. Group delay is dramatically lowered at audible frequencys, while port gain also becomes dramatically lower at audible frequencys.
A ported enclosure acts no different than a sealed one an octave above the tuning frequency. port gain is less than -15db, and group delay will be less than 1ms different. If you tune below 13hz then I gurantee there wont be any noticeable difference in the sound except lower extension on the ported box, and possibly port chuffing with a non-optimal port. Chuffing can easily be avoided using a large cross section, but this requires an insanely long port for infrasonic tuning so typically a passive radiator will take up less speace(but is more expensive) and perform the same function.
Port tuning above 20hz, dont do it!
A ported enclosure acts no different than a sealed one an octave above the tuning frequency. port gain is less than -15db, and group delay will be less than 1ms different. If you tune below 13hz then I gurantee there wont be any noticeable difference in the sound except lower extension on the ported box, and possibly port chuffing with a non-optimal port. Chuffing can easily be avoided using a large cross section, but this requires an insanely long port for infrasonic tuning so typically a passive radiator will take up less speace(but is more expensive) and perform the same function.
Port tuning above 20hz, dont do it!
Mike.e ,
I thought you had given up on BR after you built your first bass horn. Just think about it, with a BR you're taking an out of phase response and trying to turn it into something it's not. Just stuff the port of even the best implementation of a BR. Sure they give you more bass, but there's a price.
My big question with all of this is with dipole bass, why doesn't that rear wave mess up the sound?
I thought you had given up on BR after you built your first bass horn. Just think about it, with a BR you're taking an out of phase response and trying to turn it into something it's not. Just stuff the port of even the best implementation of a BR. Sure they give you more bass, but there's a price.
My big question with all of this is with dipole bass, why doesn't that rear wave mess up the sound?
It does mess up the sound at very low frequencies, that's why you need to use huge baffles with big drivers...
If you're aiming for flat response in room, you can use an EQ to bump the low end on a sealed box that will make the GD worse than a ported box.
Why not doing a ported box in the first place?
The best would be huge sealed box or infinite baffle that need no EQ...
If you're aiming for flat response in room, you can use an EQ to bump the low end on a sealed box that will make the GD worse than a ported box.
Why not doing a ported box in the first place?
The best would be huge sealed box or infinite baffle that need no EQ...
Very interesting links. I had a look at those comparisons with the traps and at first glance didn't see much change, until I saved them so I could flick from emty room to improved response. Then I notice they have reduced the "ringing" as well as the severity of the modes - they are now wider bandwidth which is easier to eq out with something like BFD or Ultracurve.
Another factor not normally considered is the impact of the room on transient response. We usually ignore this, but it may be that a discussion of transient response is meaningless without looking at the room itself. It *may* be that the impact of the room is such that small differences resulting from inductance are not audible.
I was entertaining a group of people in home home theatre last night, and so set the speakers wider apart, closer into the corners. Last time I did that it sounded bad - boomy and imaging was poor. However, this time I had subwoofers (2) and I had the system calibrated with Ultracurve, and the difference was not small. I was able to eq the modes out to the degree that the bass doesn't draw any attention and the sound is natural and neutral. Far better than before.
Another factor not normally considered is the impact of the room on transient response. We usually ignore this, but it may be that a discussion of transient response is meaningless without looking at the room itself. It *may* be that the impact of the room is such that small differences resulting from inductance are not audible.
I was entertaining a group of people in home home theatre last night, and so set the speakers wider apart, closer into the corners. Last time I did that it sounded bad - boomy and imaging was poor. However, this time I had subwoofers (2) and I had the system calibrated with Ultracurve, and the difference was not small. I was able to eq the modes out to the degree that the bass doesn't draw any attention and the sound is natural and neutral. Far better than before.
There's a lot more Ethan Winer stuff out there. Link to Ethan's long-winded acoustics paper thing There's also his company at http://www.realtraps.com/
I noticed that the first two modes don't change much. I suspect that's because the nodes of the first two modes are at the walls, and the peaks are at the center of the room. Its probably a bit impractical to put traps at the center of the room.
My room is 20' x 20' with a tapered ceiling from 8' to 14'. Because its square the first two modes are both 28 Hz -- a double whammy. I'm considering making a foot stool / coffee table trap, and also some contraption that will hang from the ceiling. This should test my girlfriend's love a bit.
I've been dabbling in NASTRAN finite element acoustics simulation at work in my spare time. nastran acoustics link I work with structural FEA, but the acoustics was new to me. I've still got a bit more to sort out, but it's very interesting so far. There's not readily available data for the acoustic absorber elements though. Ideally I'd need coefficients of absorbtion (ideally acoustic impedance) for rigid fiberglass at very low frequencies (most published data ends around 100 Hz). I've been tempted to try to simulate Ethan's test results, and then adjust absorber properties to match his test results. That would be a significant effort though and I'm not sure if I've got patience for that.
- Robert
I noticed that the first two modes don't change much. I suspect that's because the nodes of the first two modes are at the walls, and the peaks are at the center of the room. Its probably a bit impractical to put traps at the center of the room.
My room is 20' x 20' with a tapered ceiling from 8' to 14'. Because its square the first two modes are both 28 Hz -- a double whammy. I'm considering making a foot stool / coffee table trap, and also some contraption that will hang from the ceiling. This should test my girlfriend's love a bit.
I've been dabbling in NASTRAN finite element acoustics simulation at work in my spare time. nastran acoustics link I work with structural FEA, but the acoustics was new to me. I've still got a bit more to sort out, but it's very interesting so far. There's not readily available data for the acoustic absorber elements though. Ideally I'd need coefficients of absorbtion (ideally acoustic impedance) for rigid fiberglass at very low frequencies (most published data ends around 100 Hz). I've been tempted to try to simulate Ethan's test results, and then adjust absorber properties to match his test results. That would be a significant effort though and I'm not sure if I've got patience for that.
- Robert
Rademakers said:That's the same conclusion as I get to so far, the more sense it makes to apply quite large delays.
Why?
Me too, just wright it the European way from now one. And when will you guys finally come using the metric system as well? Stop delaying the inevitable, YOU KNOW it's the most logical decision 😀
Mvg Johan
Johan,
Talking to the WRONG person, I'm an Aussie and we are metric >>> talk to the yanks on that one!
It sounds to me like what you are trying to do is modify the source. If the source has something wrong with the bass, there isn't much you can do. We are talking about reproduction, not re-engineering the original.
Adason, the article you linked described what I tried to describe earlier, not very well though. It makes sense, although I don't think it's the whole story but a piece of the puzzle.
I've heard a system which is calibrated digitally. It uses Behringer Ultradrive to deal with phase for 5 different subwoofers, one of them a vented 15" focal, one a Tumult vented and 3 M&K subwoofers (sealed). Then it uses Ultracurve to tame room resonances. The bass is exceptional, very deep and powerful, but fast as well, it draws no attention unless it is exaggerated in the source.
Not enough evidence here. It's not a complete comparison, you may be comparing apples to oranges here. We can't really tell if your example refutes points made in the article or not, since how do you really know if they are properly integrated and everything is the same?
I've found it to make a big difference; while it is not a cure all, if you want to reach a certain output on a budget with compact subwoofers, it's definately something to consider. If I had the budget and space (and owned the room I use), then I'd look at something better, but I'd still use eq, even with a dipole, since they do not remove room interaction totally.
John,
your comments (some of them) seem to agree with the article, especially
Did you try your maelstrom in OB? I'd expect it to have some extended range.
Here's a concept to achieve "fast bass":
1. start with the Adire HE10 kit where it's in a sealed box
2. dipole woofers cover 40 - 200 Hz
3. IB subs cover the bottom octave
4. digital speaker management to serve as an active crossover, including phase correction, time alignment as well as room eq
5. room treatment including bass traps, diffusers and helmholz resonators designed to take the energy out of specific modes
You get extension and output down to HT levels with the OB subs, but they aren't allowed to localise (they could be built in walls close to the mains as well). You get reduced modal problems with the dipoles, which also has probably the best transient response you can get with the right drivers, in the region it counts. The digital crossover gives you the best chance of getting the mid/dipole interaction correct.
I've asked the same question, it's the reason why I haven't decided on sealed vs vented for my subs, which remain in test boxes. I'll have to set up a proper test to compare where they are calibrated to the same response.
I can't find any info on this with a quick search, what is this pi alignment?
This could be an interesting test. Calibrate a sub flat to 20 Hz, then experiment with changing the rolloff characteristics. You could do this with a sealed sub and with a vented sub designed with low tuning, and also with one tuned higher. Now if this were done outdoors with a blind test and a group, it could yield very interesting results!
Using the same driver in a ported box and a sealed with LT, I find you can get an identical GD, although with less output for the sealed box.
I've asked the same q, but one answer is size.
Robert, I think it's perhaps more that they aren't effective down that low as absorbers, it probably relates to the characteristics of the sound waves themselves. Down that low I suspect a better approach is to treat the entire enclosure of the room as a bass trap, by using a flexible mounting system for the plasterboard (or sheetrock).
Sounds to me like this is too high a price to pay for what you will get - not much IMO. As I understand, bass traps are located where surfaces junctions as this is where they are most effective. IIUC bass traps in the middle would not only be less effective but also more intrusive.
Unless of course you want something ugly and unliveable so you can then tell your gf that the alternative is ......... (insert whatever less intrusive method you care to use here) and to make it appear more attractive!
paulspencer wrote: Not enough evidence here. It's not a complete comparison, you may be comparing apples to oranges here. We can't really tell if your example refutes points made in the article or not, since how do you really know if they are properly integrated and everything is the same?
There is no big trick to integration. Level is the only variable, set with a RS digital SPL meter. The rest of the equipment remains the same, the XO point and slope is set by the Marchand. What apples and oranges could there be?
The subs don't sound the same, and one is clearly better than the other. Do you really doubt that? The Mirage has a more resonant sound when you rap the cabinet. IME that alone is enough to cause a little boom and affect the perceived speed of the bass. It doesn't stop when the signal stops, ergo slower bass.
Dan
There is no big trick to integration. Level is the only variable, set with a RS digital SPL meter. The rest of the equipment remains the same, the XO point and slope is set by the Marchand. What apples and oranges could there be?
The subs don't sound the same, and one is clearly better than the other. Do you really doubt that? The Mirage has a more resonant sound when you rap the cabinet. IME that alone is enough to cause a little boom and affect the perceived speed of the bass. It doesn't stop when the signal stops, ergo slower bass.
Dan
Paul,paulspencer said:
The only reason the Maelstrom is in a box is that I only have 1 and for now the last thing I need to buy is another woofer. Your fast bass outline isn't bad, but I'd go with the HE12's and with the higher Q leave them out of the box too. Unfortunately IB isn't possible, so I my best option for now is the Maelstrom and stuff the ports for music, at least until I build my 8-12 woofers per side dipoles. The digital management is my next step now that I have a few different amps so I can go active.
johninCR said:
I have 2 Maelstrom Sonosubs with built-in port valves that allows them to be sealed easily and I can tell a difference in the response and integration, it does sound a little faster. That being said, nothing I've heard compares to IB or OB for perceived "fast" bass or musical integration. I'm replacing my 2 Maelstrom Sonosubs that took nearly a year to complete with 2 avalanche 18" subs in a attic IB manifold and I expect a much faster perceived bass. I'll know for sure in about a week.
Wayne parham does a different alignment,it doesnt seek really low frequencies,instaed a less boomy response.[pispeakers]
ah well im selling my jbl 2226 EBS BR to build some more basshorns,as I half blew the $19 8" its all quiet [used 240w into 20w rms rated woofer]
Unfortunately I live in a flat so theres no ceiling handy to cut holes into. open baffle isnt possible due to high driver costs here in NZ...Even shipping adire tempests would cost abit.So im biting the bullet and going for basshorns that take up enormous volumes
It does,it cancels the lower bass! which is why people have to boost heaps see linkwitzlab.com 😀
ah well im selling my jbl 2226 EBS BR to build some more basshorns,as I half blew the $19 8" its all quiet [used 240w into 20w rms rated woofer]
Exactly!
Unfortunately I live in a flat so theres no ceiling handy to cut holes into. open baffle isnt possible due to high driver costs here in NZ...Even shipping adire tempests would cost abit.So im biting the bullet and going for basshorns that take up enormous volumes
Without measurements you can't really say. Your assumption that the response of both is the same may not be correct.
My point is that your example does not necessarily refute the article. If you suggest there are other factors and that integration is a part of it, then I agree.
Have you compared where the response of the two is exactly the same?
Depends what you mean by "mess up" ... the rear wave causes cancellation, and this is both the strength and weakness of the dipole. It is a strength because it creates a null to the sides which reduces the impact of the room on the bass. It is also a weakness since this means much less output. It doesn't "mess up" the sound in a SQ sense.
- Status
- Not open for further replies.