I am mostly constructing vented boxes, but I will tra a closed design now.
What are your experinces with the system Q and the driver Q values.
I have head many closed systems that sounded to compressed, because of the air traped behind the woofer. How do you get a natural sounding bas, nor compressed but stil with control?
What are your experinces with the system Q and the driver Q values.
I have head many closed systems that sounded to compressed, because of the air traped behind the woofer. How do you get a natural sounding bas, nor compressed but stil with control?
I believe it's just your mind playing games with you if you think there is air trapped behind the woofer and that is making the sound compressed.
Maybe it's just the vented boxes you heard generally went lower, so you think that sounds more natural to you?
A closed box will always have more 'control' over the sound than a vented box.
Maybe it's just the vented boxes you heard generally went lower, so you think that sounds more natural to you?
A closed box will always have more 'control' over the sound than a vented box.
In my experiences, drivers with Qts values of roughly around .3 to .5 or so generally help lend to making a good sealed subwoofer. However, more often than not, these same woofers will usually work very well in proper vented alignments too. And of course, subwoofer drivers with a low free-air resonance tend to provide lower frequency response. And as with other designs, a good amount of linear xmax always helps.Hyldal said:
As far as the total system Q, transient response tends to somewhat decrease with higher values, but the power handling of the system can increase a bit. A Qtc of 0.7 will usually give good results.
If I'm understanding you correctly, I think I can definitely relate to this statement and what you mean by this. Before I became so familiar with the different types of subwoofer systems and how they work, as well as all of the individual characteristics and Thiele-Small parameters of different subwoofer drivers used in these systems, I pretty much had the same feelings towards sealed air suspension subwoofer systems. I bought my first powered subwoofer (8" driver in a small sealed enclosure) for $150 when I was 10 years old to go with my $600 mini system. After hearing several of some of the cheapest vented subwoofer systems around that same time shortly after I bought mine, and not much higher in cost, I became very dissatisfied with the performance of my cheap subwoofer. Of course, some 14 years later now, I know quite a bit more than I did back then, and have listened to and toyed around with all kinds of subwoofers. And even now, those same thoughts I had toward sealed subwoofers 14 years ago are still somewhat the same in some aspects, but not exactly..
Basically, pretty much any subwoofer driver in a sealed enclosure isn't going to give as low of a frequency response as it would in a vented box, at least without some sort of EQing. So, does that mean that vented subwoofers are always going to perform far better than sealed enclosures? Absolutely not! It really all depends on the overall characteristics of the particular driver being dealt with, the rest of the system that the subwoofer will be used with, the room that it'll be used in, etc etc.
For example, I've listened to a couple of large custom-built subwoofers in the last year or so, specifically the ever so popular 'sonotube' designs that seem to be floating around everywhere these days. The main idea of this design is to tune the enclosure extremely low by making everything BIG. While this obviously raises group delay to the extreme, it also shoves this massive rise way down in frequency response, to where we're not so sensitive to it. As a result, the rise in group delay doesn't usually start to skyrocket until around 30Hz or so, while group delay above that is actually significantly lower than having that same subwoofer driver in a sealed box. As a major side benefit of all this, low frequency response is also extended as far as possible for the driver being used..
Anyway, having liked what I heard when I listened to these designs, I decided to gather some equipment, with plans of hopefully building one or two of these massive beasts in the future. A year or so ago, I ended up with an almost new Ascendant Audio Avalanche 15 (T/S listed below. Once I got it, I listened to that woofer in a small sealed enclosure for a good length of time, powered by a Dayton 1000 watt plate amplifier. If set up properly, it actually sounded REALLY good! Since then, I've obtained 3 more of these subwoofer drivers, and will most likely scratch my sonosub plans. Instead, I'm selling my current speakers, and going for open baffle...hopefully OB coaxials. I want to try using the open baffle L&R mains down to 35-40Hz or so, and using the 4 Avalanche 15 woofers from there down, in sealed enclosures with EQ. So yeah, basically augmenting the augmentors! With these particular drivers and this much cone area and excursion, I should be able to obtain around the same extension as I would using a large low tuned enclosure. So far, I think it should turn out pretty well.
While the Avalanche 15 would perform VERY well in a sonosub design, it's just too big for me (about 11 cubic feet EACH before displacement for a 14.6 Hz tuning!) But mainly, since I've decided to go OB with some major augmentation all the way down low, such a large vented enclosure isn't necessary anyway with all these woofers at the same time. And since I'd strictly be using them at the very lowest frequencies only, large low tuned boxes would probably do more harm than good.
If you haven't done so before already, I recommend you download WinISD (even the lesser beta version if you want, because it's much simpler)...and simulate a few good subwoofer drivers. Play around with box sizes for sealed enclosures, mess with all the configurations, and observe the outcomes of the phase plots and group delay as a result of your changes. At the same time, simulate these same drivers in their recommended vented alignments as well, observing and taking note of the system's characteristics simultaneously. After doing this, it'll become much more clear how everything works, as well as the reasons why sealed subwoofers often sound much more neutral and 'tighter' than ported enclosures.
Here are just a few of my personal recommendations of woofers to try...
Ascendant Audio Avalanche 15:
Qts- .31
Qms- 3.5
Qes- .33
Fs- 15.7 Hz
Vas- 300.6 l
Re- 3.20 ohm
Le- 2.40 mH
Xmax- 27 mm
SPL- 87.50 dB
Pe- 800 W
dia- 15 in.
Sd- 750 cm^2
CSS Subduction SDX15:
Qts- .39
Qms- 3.65
Qes- .44
Fs- 19.20 Hz
Vas- 218.4 l
Re- 3.60 ohm
Le- 1.80 mH
Xmax- 30 mm
SPL- 87.30 dB
Pe- 1000 W
BL: 16.50
dia- 15 in.
Sd- 660 cm^2
TC Sounds 18" LMS-5400 DVC:
Qts- .37
Qms- 13.01
Qes- .39
Fs- 18 Hz
Vas- 216 l
Re- 3.47 ohm
Le- 3.10 mH
Xmax- 38 mm
SPL- 88.10 dB
Pe- 2500 W
BL: 26.50
dia- 18 in.
TC Sounds 15" TC-2000:
Qts- 0.321
Qes- 0.347
Qms- 4.264
Fs- 18hz
Re- 3.19Ω
Ls- 2.45mH
Lp- 5.87mH
Rp- 4.30Ω
Dia- 320mm
Vas- 267l
mms- 296g
cms- 260um/N
bl- 17.2T*m
Spl- 88.5dB
SoundSplinter RL-p 18 D2:
Qts- .44
Qms- 4.54
Qes- .48
Fs- 20.71 Hz
Vas- 314.2 l
Re- 3.74 ohm
Le- 3.32 mH
Xmax- 27.4 mm
SPL- 89.45 dB
Pe- 1000 W
BL: 19.50
dia- 18 in.
Sd- 1188 cm^2
Mach 5 Audio IXL-18.4:
Qts- .37
Qms- 5.59
Qes- .39
Fs- 17.70 Hz
Vas- 274.1 l
Re- 3.40 ohm
Xmax- 22 mm
SPL- 89 dB
Pe- 800 W
dia- 18 in.
Sd- 1029.2 cm^2
Dayton Titanic 15:
Qts- .38
Qms- 5.89
Qes- .41
Fs- 19.93 Hz
Vas- 220.6 l
Re- 3.68 ohm
Le- 3.84 mH
Xmax- 20.5 mm
SPL- 91.70 dB
Pe- 800 W
BL: 15.79
dia- 15 in.
Sd- 735 cm^2
Adire Tempest Classic:
Qts- .39
Qms- 6.70
Qes- .40
Fs- 18.80 Hz
Vas- 317 l
Re- 3.50 ohm
Le- 2.90 mH
Xmax- 16.4 mm
SPL- 89.10 dB
Pe- 750 W
BL: 14.20
dia- 15 in.
Sd- 779 cm^2
Well, the previous post shows I'm full of baloney, but I've always been under the impression that there aren't that many drivers out there suited to sealed boxes. The Fs is usually too high, though Q is less of a problem. The sealed boxes I've built were generally unsatisfying unless I went for a finished Q higher than the usual 0.7- a value up to 0.9 or so was much better. For many years I valued flat response above all things, knowing that anybody who liked a little thump in their bass just wasn't a purist. I've gotten over that and stopped being so attached to Butterworth. Definitely run the simulations on various drivers. Though it kills efficiency, I've also had some good results adding a bit of mass to drivers to alter their parameters.
I feel many closed boxes sounds like they are not allowed to open up and sound free. The sounds "over controlled" but if the right system Q is chosen i guess, it should be no problem, I would just like to here if someone have some experinces to take this "over controlled" sound away, without loosing control and the sound gets muddy
I probably need to invetigate this when I find the time. I think I will use a drive with dual voice coils, and put a potentiometer on the one coil and drive it on the other, then i can vary the Q, with the potentiometer, and se how the Q influence the sound.
IMO, more often than not..
Infinite baffle, then large low tuned, then sealed with lots of needed EQ, then a vented with flat response
..In that order, from best to nastiest...different drivers used for each alignment that are optimized for that particular type of system, of course. And, depending on specific needs/wants..OB or dipole bass is always nice, with the main factor being whether or not the roll off will be an issue for you in your particular situation.
Once again, this is all just my personal opinion...and one that greatly depends on many different variables, at that. I'm really not biased towards any enclosure type, and have heard all kinds that performed very well and sounded great.
Infinite baffle, then large low tuned, then sealed with lots of needed EQ, then a vented with flat response
..In that order, from best to nastiest...different drivers used for each alignment that are optimized for that particular type of system, of course. And, depending on specific needs/wants..OB or dipole bass is always nice, with the main factor being whether or not the roll off will be an issue for you in your particular situation.
Once again, this is all just my personal opinion...and one that greatly depends on many different variables, at that. I'm really not biased towards any enclosure type, and have heard all kinds that performed very well and sounded great.
I never used to like sealed enclosures for bass until I tried a Linkwitz transform circuit. You need a beefy speaker and plenty of power, but once you try one I think it will change your impression of sealed enclosures as well.
What system and driver Q do you have before and after applying the Linkwitz transformer.
concerning the Dipole woofer, I probably prefere them overall, the transparens and detail is the best, but maybe my systems have been to small, because It lack a bit of physic, and attack. The sounf kind of stays there around the speaker ,but does not come out in the room, I think that count for all panel speakers.
concerning the Dipole woofer, I probably prefere them overall, the transparens and detail is the best, but maybe my systems have been to small, because It lack a bit of physic, and attack. The sounf kind of stays there around the speaker ,but does not come out in the room, I think that count for all panel speakers.
Q.......
Sounds like you have really only heard some over-damped (Q, appx. .5) systems. My MTM towers at .933 of Q really are "open" sounding....try a system at .7 to .9 , I think you will not be disappointed. Pay attention to SPL ratings...perhaps you are confusing lack of effiency with 'openness'?
_______________________________________Rick.........
Sounds like you have really only heard some over-damped (Q, appx. .5) systems. My MTM towers at .933 of Q really are "open" sounding....try a system at .7 to .9 , I think you will not be disappointed. Pay attention to SPL ratings...perhaps you are confusing lack of effiency with 'openness'?
_______________________________________Rick.........
It is not so much open ness I have been missing, but I lack the lively natural bas reproduction, but talking to several people now, I think It is a matter of going higher than the Q of 0,6 - 0,7.
I would love to her some more of the Linkwitz transformer solution.
If you have a 0,5Q box can you turn it to a 0,9Q box then? And does It relly sound like that, and can you go the other way around also, change a high Q box to a lowQ box?
I would love to her some more of the Linkwitz transformer solution.
If you have a 0,5Q box can you turn it to a 0,9Q box then? And does It relly sound like that, and can you go the other way around also, change a high Q box to a lowQ box?
The Linkwitz transform circuit does work well, although I have only used it to reduce the Q of speakers. (I'm one of those people who think a Q of 0.5 to 0.6 is ideal. I cannot see how anyone used to listening to live music could ever tolerate a Q of 0.9!)
There's simple spreadsheet to design the Linkwitz transform circuit on the 'Trueaudio' website if you've not got one already. It does assume that you have got accurate figures for the resonant frequency and Q of the un-compensated speaker though.
There's simple spreadsheet to design the Linkwitz transform circuit on the 'Trueaudio' website if you've not got one already. It does assume that you have got accurate figures for the resonant frequency and Q of the un-compensated speaker though.
If you built and enjoyed vented box speakers before, a speaker with a closed box Qtc of 1.0 will not bother you a bit. That is because even the best practical vented speakers have a tightness roughly equivalent to a vented box of Qtc = 1.3.
There is an entire discussion of this on this forum here.
However just to give you an idea, here is the step response for certain vented alignments, taken from Richard Small's, (of Thiele-Small fame) article.
Please note that a=Vas/Vb. So a speaker with a Vas of 2.0 cu ft, when put into a box of 0.5 cu ft, will have an a=4. Generally, you will see the larger the a facotr, (that is, the smaller the box compared to Vas), the tighter the bass.
There is an entire discussion of this on this forum here.
However just to give you an idea, here is the step response for certain vented alignments, taken from Richard Small's, (of Thiele-Small fame) article.
Please note that a=Vas/Vb. So a speaker with a Vas of 2.0 cu ft, when put into a box of 0.5 cu ft, will have an a=4. Generally, you will see the larger the a facotr, (that is, the smaller the box compared to Vas), the tighter the bass.
Attachments
And now here is the step response for closed boxes with various Qtc's. As you can see, the difference between a Qtc of 0.5 and a Qtc of 1.0 is much less than the difference between Qtc = 1.0 and just about any vented boxes, even the smoother ones.
So if you enjoy vented boxes, as I do, you will hve no trouble with a closed box of Qtc=1.0.
There is one aspect of this which needs to be brought out, though. The vented box puts out more bass, but the cone moves less than the closed box-that is the benefit of the ported output. So if your woofer is going to carry any midrange frequencies, they will be played with less distortion in the vented box than in the closed box.
However, for simple subwoofer applications, crossing over at 300 Hz or lower, this is not a consideration.
So if you enjoy vented boxes, as I do, you will hve no trouble with a closed box of Qtc=1.0.
There is one aspect of this which needs to be brought out, though. The vented box puts out more bass, but the cone moves less than the closed box-that is the benefit of the ported output. So if your woofer is going to carry any midrange frequencies, they will be played with less distortion in the vented box than in the closed box.
However, for simple subwoofer applications, crossing over at 300 Hz or lower, this is not a consideration.
Attachments
you have another solution, try this soft, phase audibility : you can listen while you vary the Q of a sealed or vented box without changing other parameters
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