Philip, a second driver in double the box volume will increase the overall efficiency, but it will not change the roll off characterisitics of the system. A PR will resonate with the driver and produce extra output at it's resonant frequency.
To change the rolloff with two drivers, you have to mount them so that their rear waves cancel each other. This can be done with a dipole arrangement, or by using a 1/2 wave delay line. Of course at bass frequencies, you are talking several metres of line.
To change the rolloff with two drivers, you have to mount them so that their rear waves cancel each other. This can be done with a dipole arrangement, or by using a 1/2 wave delay line. Of course at bass frequencies, you are talking several metres of line.
A PR is used to play different frequencies to the active driver and thus extend the overall bandwidth the same as a port would. A second driver will add over the same bandwidth and give increased SPL over that range, but not extend it (i.e. go deeper with the same power).
Best thing to do is model it and see the difference in Unibox.
Thanks for the information guys. I get how the rolloff of the system would stay the same, but if efficiency goes up, wouldn't output go up as well as more electrical power is converted into mechanical energy vs. heat?
And the other thing is power handling: with two drivers your bass power handling should go up, so if you use some sort of a bass boost, you will not run out of excursion as quickly as you would with one driver as described at:
http://www.d-s-t.com/main/tech/appxls2.htm
... in their sealed system and as discussed on this thread
And the other thing is power handling: with two drivers your bass power handling should go up, so if you use some sort of a bass boost, you will not run out of excursion as quickly as you would with one driver as described at:
http://www.d-s-t.com/main/tech/appxls2.htm
... in their sealed system and as discussed on this thread
OK here goes.
If you have two sealed subs independant of one another then you will get more SPL then if you had one but not more bass extension.
See the pic below, look at the bass reponse. Now if there were two drivers playing the level would increase, you could say the sensativity has increased. But you would not say the system plays any lower.
BUT if you add a passive radiator or a port to the system, the port uses the drivers rear output and the box to boost the output around a certain frequency so thus boosts the bass. This is not a sensativity hike, it simply adds extra extension to the system, making it play lower.
Due to the nature of the XLS, if you use them sealed they sound very weedy and thin not outputting much bass at all. This is because they roll off at about 100hz give or take. Whereas if you use them ported or PR'd they dont at all, infact they play "flat" to about 20hz. This is all with 1 watt of power. The sealed version starts to roll off at 100hz, the PR'd at 20hz.
It sounds to me like you are using the XLS as bass drivers in your speakers in which case you will have two. Two sealed XLS will go loud and lowish, f3 (this is where the bass has rolled of by three decibels) of 35hz. This is if you apply active equalisation!!! In a sense this is harder to do then ported if you are not confident will loudspeaker deisgn or dont have access to design software that can simulate what circuit you need to add to give a desired bass response.
PR'd however would be much more simple, you dont need EQ at all. There are loads of deisngs out there that use PR'd XLS so copying one of them for your bass box would make life easy.
Do you intend to make an active or passive speaker system?? or a combination of both??
If you are a novice to loudspeaker deisgn I would take a step back for the moment and embark on a much simpler two way design. Either build a kit or work with easy to use drivers. And if you want to add bass simply just use the XLS as a sub for the time being. Then as time goes on and you learn more you can build a proper three way.
If you have two sealed subs independant of one another then you will get more SPL then if you had one but not more bass extension.
See the pic below, look at the bass reponse. Now if there were two drivers playing the level would increase, you could say the sensativity has increased. But you would not say the system plays any lower.
BUT if you add a passive radiator or a port to the system, the port uses the drivers rear output and the box to boost the output around a certain frequency so thus boosts the bass. This is not a sensativity hike, it simply adds extra extension to the system, making it play lower.
Due to the nature of the XLS, if you use them sealed they sound very weedy and thin not outputting much bass at all. This is because they roll off at about 100hz give or take. Whereas if you use them ported or PR'd they dont at all, infact they play "flat" to about 20hz. This is all with 1 watt of power. The sealed version starts to roll off at 100hz, the PR'd at 20hz.
It sounds to me like you are using the XLS as bass drivers in your speakers in which case you will have two. Two sealed XLS will go loud and lowish, f3 (this is where the bass has rolled of by three decibels) of 35hz. This is if you apply active equalisation!!! In a sense this is harder to do then ported if you are not confident will loudspeaker deisgn or dont have access to design software that can simulate what circuit you need to add to give a desired bass response.
PR'd however would be much more simple, you dont need EQ at all. There are loads of deisngs out there that use PR'd XLS so copying one of them for your bass box would make life easy.
Do you intend to make an active or passive speaker system?? or a combination of both??
If you are a novice to loudspeaker deisgn I would take a step back for the moment and embark on a much simpler two way design. Either build a kit or work with easy to use drivers. And if you want to add bass simply just use the XLS as a sub for the time being. Then as time goes on and you learn more you can build a proper three way.
Attachments
Hey 5th Element, thanks for the detailed post. I am now understanding what you are saying about bass level. If you had two separately powered xls 10's then the levels put out from each would sum in room and the overall level would be higher. However, all frequencies put out by the sub would increase, thus necessitating equalization, which is what you were talking about...
I better say why I want to go sealed. Two or three years ago I bought a 12" Eclipse subwoofer for which I built a vented box tuned to roughly 30Hz, using a design made by a speaker designer. However, despite the fact that I was wowed by the depth of the bass, it lagged in tight sections: for instance, in fast rap or dance music the bass would ebb more than hit. In fact, over the next few years, I built two different boxes, exactly to the specifications of their plans, but all to the same effects. This was driving me crazy!!! All I wanted was tight, deep bass! Until recently I have been pulling my hair out about why this occurred, but after a lot of people told me that port size is directly linked to enclosure volume, I had a thought. I was putting a lot of stuffing in my enclosures, which were small to begin with. Therefore the effective volume is much greater than recommended and the box would be improperly tuned. You must realize that when this occurred to me it was an epiphany. I could never figure out why other people never complained of bad tranient response from their ported boxes, or why speakers in clubs (which need great transient response) are also ported. After reading a few threads, I don't think I don't think I am going to be stuffing my subwoofer boxes any more.
Why did I want to go sealed with these bass drivers? Bad experience, port size, and turbulence. The first problem I think I've covered (opinion?), the second I think I can accomplish with multiple ports, and the third... I don't want to have any turbulence because I think that would really negatively affect the sound. What tips do you have about turbulence in ports? I would be using 3" diameter circular pvc tubing with 90-180 degree turns. One option would be to run the ports straight up and down and have them exit at the top. Using passive radiators would be too expensive and the box would look cluttered with 2 more 12" PR's.
JBL, in their subwoofer tutorials, describes good transient response as being able to reproduce the hit of a drumstick or someone quickly plucking a string on a bass guitar. In your opinion, do you think that a ported and properly tuned xls would be able to correctly reproduce these sounds?
As for me designing the system, I won't be, really. I'm going to try my hand at enclosure design for the two enclosures, but ultimately have zalytron or solen check them over, and also have them design the crossover. I don't want to make mistakes on this project (or as few as possible)! Talk to you soon,
Philip
I better say why I want to go sealed. Two or three years ago I bought a 12" Eclipse subwoofer for which I built a vented box tuned to roughly 30Hz, using a design made by a speaker designer. However, despite the fact that I was wowed by the depth of the bass, it lagged in tight sections: for instance, in fast rap or dance music the bass would ebb more than hit. In fact, over the next few years, I built two different boxes, exactly to the specifications of their plans, but all to the same effects. This was driving me crazy!!! All I wanted was tight, deep bass! Until recently I have been pulling my hair out about why this occurred, but after a lot of people told me that port size is directly linked to enclosure volume, I had a thought. I was putting a lot of stuffing in my enclosures, which were small to begin with. Therefore the effective volume is much greater than recommended and the box would be improperly tuned. You must realize that when this occurred to me it was an epiphany. I could never figure out why other people never complained of bad tranient response from their ported boxes, or why speakers in clubs (which need great transient response) are also ported. After reading a few threads, I don't think I don't think I am going to be stuffing my subwoofer boxes any more.
Why did I want to go sealed with these bass drivers? Bad experience, port size, and turbulence. The first problem I think I've covered (opinion?), the second I think I can accomplish with multiple ports, and the third... I don't want to have any turbulence because I think that would really negatively affect the sound. What tips do you have about turbulence in ports? I would be using 3" diameter circular pvc tubing with 90-180 degree turns. One option would be to run the ports straight up and down and have them exit at the top. Using passive radiators would be too expensive and the box would look cluttered with 2 more 12" PR's.
JBL, in their subwoofer tutorials, describes good transient response as being able to reproduce the hit of a drumstick or someone quickly plucking a string on a bass guitar. In your opinion, do you think that a ported and properly tuned xls would be able to correctly reproduce these sounds?
As for me designing the system, I won't be, really. I'm going to try my hand at enclosure design for the two enclosures, but ultimately have zalytron or solen check them over, and also have them design the crossover. I don't want to make mistakes on this project (or as few as possible)! Talk to you soon,
Philip
OK well I cant really contribute to the sound of a PR'd XLS or ported (is a ported really possible with the huge port lengths?) as i have not done this. The XLS however do move copious quatities of air so will need a big port for this not to be a problem. In a sealed box you get nice tight bass that starts and stops quickly. You do need active EQ to get good bass respose though as I have stated bofore which could make life more difficult.
Having said that you could probably apply the EQ to the total loudspeaker and it wouldnt affect the mid and tweet enough to cause any problems.
Having said that you could probably apply the EQ to the total loudspeaker and it wouldnt affect the mid and tweet enough to cause any problems.
Ported enclosures should not be stuffed a lot. Perhaps just line the walls.
I don't think the difference will be much greater as long as you didn't cram the stuffing in.
Make them as large as possible. I would go bigger than 3" if possible. As port dia. is increased, so does its length for a given tuning freq. Make sure you give enough breathing space at the end of the port in the enclosure, but apart from that a longer port will allow you a bigger dia., thus reduced port noise potential. A PR doesn't have port noise/turbulence problem. But as you say it comes with a hefty price relatively speaking.
With the XLS, porting is not an easy tuning exercise in any reasonable sized enclosure.
Also don't get too hung up on transient response in subs. Sealed does of course have the air spring to help it out, and higher power handling, but at the cost of increased distortion at the lower freqs and less bass extension. If you make enough models of the XLS, you will come to same conclusion that I did, that a PR is the only way with the XLS (unless you're confident with EQing like Matt, and don't want as much exntension.)
EQ
What's the story with active EQ, or EQ for that matter? Do I have to put it in before the amplifier, after the amplifier, or can I work it into the crossover somehow?
And no offense to 5th E, but if anyone wants to comment on the predicted transient response of the system, please do because this is my biggest area of concern. For me it is useless going deep unless the transient response is good.
Thanks,
Philip
What's the story with active EQ, or EQ for that matter? Do I have to put it in before the amplifier, after the amplifier, or can I work it into the crossover somehow?
And no offense to 5th E, but if anyone wants to comment on the predicted transient response of the system, please do because this is my biggest area of concern. For me it is useless going deep unless the transient response is good.
Thanks,
Philip
Active EQ should be done at line level between the pre and power stages of the amplification.
You could do it passively, but it would incredibly wasteful of power. Active EQ can also be incredibly wasteful of amplifier power, you need 16x the power to reproduce the F12 tone. Of course if you've got enough sensitivity and/or enough power it's not a problem. IIRC the 10" XLS is about 3dBW less sensitive than the 12", and the 12" will play lower for a given sealed alignment (.707, 0.6 etc) than the 10".
You could do it passively, but it would incredibly wasteful of power. Active EQ can also be incredibly wasteful of amplifier power, you need 16x the power to reproduce the F12 tone. Of course if you've got enough sensitivity and/or enough power it's not a problem. IIRC the 10" XLS is about 3dBW less sensitive than the 12", and the 12" will play lower for a given sealed alignment (.707, 0.6 etc) than the 10".
No offense taken
How the heck do you predict transient response anyway? I'd like to know this too.
Surely it is subjective and involves amplifier, source and the room oh and the speakers ofcourse.
I dont know how to quantify this but the XLS are very tight in the bass if thats what your after. Im sure its not and you want a scientific number or graph to explain this, I cant help there but it do sound dang good.
Im no expert in physics or design but surely one driver in a Q=0.5 box and another completely different driver in a Q=0.5 box will start and stop moving just as quickly. I have read somewhere that voice coil inductance inhibits T response, is this correct or am I thinking of something else?
There was a post a bit back on this regarding "is a 15" to big for music" this post is long but has it in it somewhere, with impulse tests on drivers, altering certain parameters to show how T response was altered.
How the heck do you predict transient response anyway? I'd like to know this too.
Surely it is subjective and involves amplifier, source and the room oh and the speakers ofcourse.
I dont know how to quantify this but the XLS are very tight in the bass if thats what your after. Im sure its not and you want a scientific number or graph to explain this, I cant help there but it do sound dang good.
Im no expert in physics or design but surely one driver in a Q=0.5 box and another completely different driver in a Q=0.5 box will start and stop moving just as quickly. I have read somewhere that voice coil inductance inhibits T response, is this correct or am I thinking of something else?
There was a post a bit back on this regarding "is a 15" to big for music" this post is long but has it in it somewhere, with impulse tests on drivers, altering certain parameters to show how T response was altered.
I think it was Adire who did the testing. A high BL/Mass ratio was the desirable outcome IIRC, but BL seemed more important than Mass, although the moving mass of the driver will determine how much kinetic energy it accumulates. In effect a lighter cone will stop faster, but a more powerful magnet structure will start it moving quicker.
Mudge: Thanks for the info about the EQ. It makes sense.
As for transient response, there is a good explanation of what it means on the jlaudio.com site at:
http://www.jlaudio.com/tutorials/magic/performance.html
Explanations of transient response are subjective, but there's no doubt it's there; there is an obvious problem in systems with bad TR. As for whether it can be seen on a graph I don't know. What I do know is you can tune a box to any frequency, but I would rely on other indicators to predict the TR. Everyone keeps talking about this "Q." What is this? Is this the same as Qtc of the speaker? I don't think so because it is influenced by box size. What effect do you have with Q > .5, and Q < .5? .5 seems to be the magic number.
As for 15", Radio Shack (North America) has this book by Joe D'Appolito, in which he discusses how effective cone diameter affects the ability of speakers to reproduce certain wavelengths, and I don't think this is related to the speaker's ability to move. In other words, 15's can be used to make musical sounds, and often are in the cases of the high-end focal speakers and other manufacturers.
Based on the numbers for the 10" XLS in a sealed box, I have kind of resigned myself to go ported. The only thing is I am having trouble figuring out port length. Here's the thing: Peerless suggests using the XLS in a 26L box tuned to 25Hz, using a circular port of 70mm x 930mm. However, I want to use two XLS 10's. I know to do this you would double the box size, but how is port length affected. From the equation of tuning frequency,
http://www.jlaudio.com/tutorials/ports/index.html
Vb (volume of box) and Lp(length of port) are in the denominator, so it seems Lv would decrease if Vb goes up. I've got to fit the port inside the box, so by how much would it go down by in this scenario? Next question, what effect is there on port length if you use multiple drivers? By how much would length go up here if I used two drivers? If Lv went up for each of the two ports as compared to one, could you use smaller port diameter and thus a shorter port because you are using two ports to move air? I've tried calculating myself in excel but keep getting wierd numbers. Thanks for your help,
Philip
As for transient response, there is a good explanation of what it means on the jlaudio.com site at:
http://www.jlaudio.com/tutorials/magic/performance.html
Explanations of transient response are subjective, but there's no doubt it's there; there is an obvious problem in systems with bad TR. As for whether it can be seen on a graph I don't know. What I do know is you can tune a box to any frequency, but I would rely on other indicators to predict the TR. Everyone keeps talking about this "Q." What is this? Is this the same as Qtc of the speaker? I don't think so because it is influenced by box size. What effect do you have with Q > .5, and Q < .5? .5 seems to be the magic number.
As for 15", Radio Shack (North America) has this book by Joe D'Appolito, in which he discusses how effective cone diameter affects the ability of speakers to reproduce certain wavelengths, and I don't think this is related to the speaker's ability to move. In other words, 15's can be used to make musical sounds, and often are in the cases of the high-end focal speakers and other manufacturers.
Based on the numbers for the 10" XLS in a sealed box, I have kind of resigned myself to go ported. The only thing is I am having trouble figuring out port length. Here's the thing: Peerless suggests using the XLS in a 26L box tuned to 25Hz, using a circular port of 70mm x 930mm. However, I want to use two XLS 10's. I know to do this you would double the box size, but how is port length affected. From the equation of tuning frequency,
http://www.jlaudio.com/tutorials/ports/index.html
Vb (volume of box) and Lp(length of port) are in the denominator, so it seems Lv would decrease if Vb goes up. I've got to fit the port inside the box, so by how much would it go down by in this scenario? Next question, what effect is there on port length if you use multiple drivers? By how much would length go up here if I used two drivers? If Lv went up for each of the two ports as compared to one, could you use smaller port diameter and thus a shorter port because you are using two ports to move air? I've tried calculating myself in excel but keep getting wierd numbers. Thanks for your help,
Philip
Transient response of 10"xls and PR
Hey 5th E, thanks so much for running that - that's a big help. It's great to hear that the port will be shorter; I want to run a perfectly straight port if possible.
And as for transient response, I just talked to this one guy by email who was part of a loudspeaker design company who helped work on a 10" xls with PR and he said the bass was tight, maybe even too tight - I'm not worried though. He said it totally keeps up in fast techno and is smooth(?). He said that using box volumes between 27 and 35 L doesn't affect the frequency response at all. The only thing was that bass fell off below 30Hz and so didn't have the boominess you might expect in HT.
And remember how you were asking how to predict TR from graphs? I found a post at diysubwoofers.org where one guy asked the same question - he was directed to the adireaudio.com tech site and they have a brilliant article describing how "group delay" is a major predictor of transient response. You should check it out as it answered a lot of my questions. You need some program called LpsCAD to find out. I'm sure you've heard of this program but I haven't.
But as for Q, I still don't know what this means. What is it?
Hey 5th E, thanks so much for running that - that's a big help. It's great to hear that the port will be shorter; I want to run a perfectly straight port if possible.
And as for transient response, I just talked to this one guy by email who was part of a loudspeaker design company who helped work on a 10" xls with PR and he said the bass was tight, maybe even too tight - I'm not worried though. He said it totally keeps up in fast techno and is smooth(?). He said that using box volumes between 27 and 35 L doesn't affect the frequency response at all. The only thing was that bass fell off below 30Hz and so didn't have the boominess you might expect in HT.
And remember how you were asking how to predict TR from graphs? I found a post at diysubwoofers.org where one guy asked the same question - he was directed to the adireaudio.com tech site and they have a brilliant article describing how "group delay" is a major predictor of transient response. You should check it out as it answered a lot of my questions. You need some program called LpsCAD to find out. I'm sure you've heard of this program but I haven't.
But as for Q, I still don't know what this means. What is it?
Well then I should be rite on it I have LSPcad Professional
Thats what i simulated that box with
Ive only had it for a short time and am still gettin to grips with all the functionality.
I have up to now built a two way from the ground up making measurements of everything and using the xover simulator to listen to the reults before buying the xover.
These drivers are a vifa c20wj and a 25mm plastic dome for which I dont recal the part number. They sound simply sensational. Lspcad surely works a treat i recommend it to anyone out there.
Thats what i simulated that box with
Ive only had it for a short time and am still gettin to grips with all the functionality.
I have up to now built a two way from the ground up making measurements of everything and using the xover simulator to listen to the reults before buying the xover.
These drivers are a vifa c20wj and a 25mm plastic dome for which I dont recal the part number. They sound simply sensational. Lspcad surely works a treat i recommend it to anyone out there.
The general rule of thumb is that a Passive Radiator system increased the rate of cutoff by 6 dB, or one order. As transient response in the bass region is affected by cutoff rate, this means slightly worse transient response.
However, the Passive Radiator is a way to get the benefits of the bass reflex system, (yes, it is a form of bass reflex, although it is never referred to that way), in a box where a port is impractical.
There is some further discussion on this on this thread here:
http://www.diyaudio.com/forums/showthread.php?threadid=4142&highlight=
I also include this side-by-side chart of a Peerless woofer-not an XLS-in similar ported and Passive Radiator systems. I found this chart on the net somewhere, I did not make it. It is also included in that thread, on post #6. So you can see a difference, which is evidence on the last small pulse.
However, you should understand that our ability to hear these differences in transient response decreases the lower the frequency, and that the "overshoot" decreases the farther away from the resonance frequency you get.
However, the Passive Radiator is a way to get the benefits of the bass reflex system, (yes, it is a form of bass reflex, although it is never referred to that way), in a box where a port is impractical.
There is some further discussion on this on this thread here:
http://www.diyaudio.com/forums/showthread.php?threadid=4142&highlight=
I also include this side-by-side chart of a Peerless woofer-not an XLS-in similar ported and Passive Radiator systems. I found this chart on the net somewhere, I did not make it. It is also included in that thread, on post #6. So you can see a difference, which is evidence on the last small pulse.
However, you should understand that our ability to hear these differences in transient response decreases the lower the frequency, and that the "overshoot" decreases the farther away from the resonance frequency you get.
Attachments
As regards the tutorial from JL audio, a word on the tuning.
http://www.jlaudio.com/tutorials/ports/index.html
"But the first method is incorrect because it neglects the fricitional losses encountered by using many smaller ports--there is a higher port wall surface area to cross-sectional area ratio which raises the total amount of frictional losses in the ports and thus shifts the tuning! "
What they don't tell you is that even if Method 1 is wrong, it will be wrong by only 1 Hz! If you make the four ports 18.8 inches long, you will be tuning to 26 Hz instead of 25 Hz.
So relax. It's nice ot get things right on, but there are so many factors that it will make very little difference if you get it slightly off.
http://www.jlaudio.com/tutorials/ports/index.html
"But the first method is incorrect because it neglects the fricitional losses encountered by using many smaller ports--there is a higher port wall surface area to cross-sectional area ratio which raises the total amount of frictional losses in the ports and thus shifts the tuning! "
What they don't tell you is that even if Method 1 is wrong, it will be wrong by only 1 Hz! If you make the four ports 18.8 inches long, you will be tuning to 26 Hz instead of 25 Hz.
So relax. It's nice ot get things right on, but there are so many factors that it will make very little difference if you get it slightly off.
Hey guys, thanks to everyone who has been so patient and has provided all the information they have. In the best interest of diyaudio.com and those searching for information, I have decided to continue my train of thought on "Subwoofer Qtc and tightness" at:
http://www.diyaudio.com/forums/showthread.php?s=&postid=365871#post365871
because my questions are revolving around that subject. Anyone should feel free to continue posting along the lines of this thread. God Bless, and hope to hear from you guys soon on the other thread,
Philip
http://www.diyaudio.com/forums/showthread.php?s=&postid=365871#post365871
because my questions are revolving around that subject. Anyone should feel free to continue posting along the lines of this thread. God Bless, and hope to hear from you guys soon on the other thread,
Philip
Im hoping to add the XLS 10 to use in a FAST system with a mark audio alpair 7.3 on top, in a configuration shown in the sketchup model below.
Can anyone recommend any design changes?
Active with miniDSP
Can anyone recommend any design changes?
Active with miniDSP
An externally hosted image should be here but it was not working when we last tested it.
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