Thanks for clearing that up, I think I finally understand 'slow bass'...I never understood what people meant by this term. I always just called that the sound of a badly designed enclosure, or a badly constructed one... anyway, it's called transient response.
I understand the bass rolloff resulting from dipole. It is only 6db per octave though and is a sacrifice I'm very willing to make to get the natural sound and virtually eliminate the room, especially with everything made out of concrete down here.
What I don't understand is why the rear wave being in play doesn't do more harm SQ wise.
Mike,
Here in Costa Rica shipping and duties more than doubles the cost of drivers. I have found some cheap 12's (under $15ea) that sound good (my test for that is giving them a full range signal and see what they sound like. Compare a lot of woofers that way and it's easy to separate the junk). They have a highish Qts and a 7-8mm one way excursion and an Fs of 28hz, making them a great candidate for dipole. Check around locally, dipole drivers can end up much cheaper than good horn candidates if you shop for bargains.
What I don't understand is why the rear wave being in play doesn't do more harm SQ wise.
Mike,
Here in Costa Rica shipping and duties more than doubles the cost of drivers. I have found some cheap 12's (under $15ea) that sound good (my test for that is giving them a full range signal and see what they sound like. Compare a lot of woofers that way and it's easy to separate the junk). They have a highish Qts and a 7-8mm one way excursion and an Fs of 28hz, making them a great candidate for dipole. Check around locally, dipole drivers can end up much cheaper than good horn candidates if you shop for bargains.
paulspencer said:
The subs have the same LF extension and are fed the same signal out of the Marchand crossover. For the comparison, the signal was not processed in any way by the sub.
Good, then we agree. I didn't mean to imply that integration wasn't a major factor. But it's not the whole story, which is what the first poster I replied to, and Blackburns article, are saying.
Illusus said:
"Slow bass" is a subjective term. Transient response is an objective term. But transient response is not the only explanation for slow bass. I don't believe driver size is a useful measure either, which I believe is what started this thread.
dont want to confuse the discussion even more, but some times it seems to me like we are all talking about two different things
when talking about slow bass, one person can understand the feeling he has while listening, the lag of bass after a midrange, caused by time delay, the other can percieve more distorted bass as muddy, slow
in both cases it can be percieved as slow, but it is a totaly different issue
what I meant by the statement "there is no such thing as fast or slow subwoofer, all subwoofer are inherently slow" was that if you apply 30 Hz tone to various subwoofers, you get 30 Hz tone back, they have the same speed....slow...however, the integration of the sub with the rest of the system will detemine if it sounds slow or fast
I believe there is more issues, the main is quality of the woofer, especialy woofers efficiency, as is my personal experience, the more efficient the woofer, the better bass, perhaps has something to do with transient response, which is usualy better with increasing efficiency, then offcourse the enclosure construction...but that is irelevant here, I though we all assumed we are talking about well constructed subwoofers and only comparing one big woofer bass vs many small woofers bass
when talking about slow bass, one person can understand the feeling he has while listening, the lag of bass after a midrange, caused by time delay, the other can percieve more distorted bass as muddy, slow
in both cases it can be percieved as slow, but it is a totaly different issue
what I meant by the statement "there is no such thing as fast or slow subwoofer, all subwoofer are inherently slow" was that if you apply 30 Hz tone to various subwoofers, you get 30 Hz tone back, they have the same speed....slow...however, the integration of the sub with the rest of the system will detemine if it sounds slow or fast
I believe there is more issues, the main is quality of the woofer, especialy woofers efficiency, as is my personal experience, the more efficient the woofer, the better bass, perhaps has something to do with transient response, which is usualy better with increasing efficiency, then offcourse the enclosure construction...but that is irelevant here, I though we all assumed we are talking about well constructed subwoofers and only comparing one big woofer bass vs many small woofers bass
audiobomber said:
I think I was the one who stirred the pot when I defended some of the points made by the manufacturer of the 4 driver sub. My point was that TYPICAL subwoofer drivers aren't capable of making really great quality bass and almost any small driver can with enough of them. Of course there are large drivers that make great bass, so I totally agree that driver size itself is not useful. Maybe transient response is the limiting factor before you can start talking about alignment and room effects.
It's good to see these new drivers coming out that appear to be an significant improvement. Maybe we can get back to putting all the drivers in our mains and forget the separate subs but still enjoy the extension and bottom end output that we demand, at least for music.
Adason,
I don't think what's happening at 30hz is the issue, that is barely in our audible range and I doubt if I could make a distinction between subs playing a 30hz tone of the same SPL. However, certainly at 70-80hz, tonality, transient response and everything else that defines a driver's sound come into play and even when you cross the sub very low there's still output in the range that matters. That's why Lowther owners have such trouble integrating a sub. Trying to integrate true speed with a driver incapable of it even in the lowest frequencies just isn't going to work.
I don't think what's happening at 30hz is the issue, that is barely in our audible range and I doubt if I could make a distinction between subs playing a 30hz tone of the same SPL. However, certainly at 70-80hz, tonality, transient response and everything else that defines a driver's sound come into play and even when you cross the sub very low there's still output in the range that matters. That's why Lowther owners have such trouble integrating a sub. Trying to integrate true speed with a driver incapable of it even in the lowest frequencies just isn't going to work.
i know one manufacturer (bose) which managed to make pretty bad sounding subwoofers by puting four small pseudowoofers into crapy box....sound terrible, no low fr extension, high distortion, we dont want this
true, if there were proper bass drivers used in properly constructed mains, no one needs subwoofer
however, there is a use for subwoofers, especialy for us listening to full range speakers, where there is no way no matter how hard you try, to get all the way down
johninCR said:
Would there be agreement in this discussion then, that:
- bass speed (fast or slow) is a useful concept
- transient response, integration and room effects are the objective determinants that affect the subjective concept of "bass speed".
?
agreed
hmmm...it takes highly efficient woofers, but it can be done...i arrived at two subwoofers, right under my mains, quasi basszila like system, except I have very different crossover, works for me
i can hardly imagine four small woofers as sub, there is no low fr extension to start with
The Avalanche 18" has a Le of 2.4 mH which I believe is considered high and obviously a large driver, yet those who are using these in an IB are reporting that the sound is subjectively "very fast" and extremely musical. Also many other drivers used in a IB configuration are all reporting so-called "fast" sound, so maybe there is more to the alignment then we think. I've never heard of anyone claiming that any IB is in any way "slow".
Group-delay and transient response must have a good deal to do with it, it seems only logical that if you send a signal to a driver and it takes several milliseconds for the cone to move then your bass notes could be lagging relative to your mains that are reproducing the fundamentals of these notes. If group-delay and transient response is a good deal of the equation, then the box alignment is in fact the main culprit for this since the same driver in different alignments can have higher or lower group-delay or transient response.
However, having said that, if you add the right amount of delay to your mains anyone’s sub should be just as "fast" as any, as long as the GD and TR are linear, right?
Group-delay and transient response must have a good deal to do with it, it seems only logical that if you send a signal to a driver and it takes several milliseconds for the cone to move then your bass notes could be lagging relative to your mains that are reproducing the fundamentals of these notes. If group-delay and transient response is a good deal of the equation, then the box alignment is in fact the main culprit for this since the same driver in different alignments can have higher or lower group-delay or transient response.
However, having said that, if you add the right amount of delay to your mains anyone’s sub should be just as "fast" as any, as long as the GD and TR are linear, right?
How does bringing up Bose make a point? Go into any chain store, Best Buy, Walmart, etc. , and every single sub for sale is unacceptable in my book. If you are going to use small drivers you'll need a lot of them. Also, I forgot about the small drivers used in many small subs, and there are small drivers incapable of making quality bass. Anything large or small that can't play several hundred hz reasonably can't make great bass even in the 60-80hz range.
did not mean to make a point by mentioning bose, sorry about that
what i wanted to say was that if you take (from one great speaker maker, let say tad) a line of their woofers and compare 18" or 15" with 8" or 6" woofers, no matter how many 6" you take, you will not have low fr extension of one single big woofer
four 6" woofer in one box will have the same fr response as one 6" woofer, thus limiting in low fr
weather it is going to sound fast or slow is irelevant of the woofer size since it depends on integration and other things we covered
coming up with theory that many small woofers is better than one proper big woofer is scating on thin ice and can lead to missuse and missinterpretation
what i wanted to say was that if you take (from one great speaker maker, let say tad) a line of their woofers and compare 18" or 15" with 8" or 6" woofers, no matter how many 6" you take, you will not have low fr extension of one single big woofer
four 6" woofer in one box will have the same fr response as one 6" woofer, thus limiting in low fr
weather it is going to sound fast or slow is irelevant of the woofer size since it depends on integration and other things we covered
coming up with theory that many small woofers is better than one proper big woofer is scating on thin ice and can lead to missuse and missinterpretation
You can easily get down to 40 Hz and with 4 x 6" have more efficiency than a single 12" with an fs of 20 Hz. Given equivalent excursion, the smaller drivers will have more output. With enough drivers (VD) you can get down lower with an EBS. You could probably end up with the same result in terms of output and efficiency and extension with active filters, sacrificing midbass output.
Frequency extension was something I was going to bring up, what good is a sub that will only play to 40Hz or even 25Hz. For HT, I wouldn’t touch a sub that isn't flat to 15Hz in room with good output of say 115db. How can any group of small drivers get low enough for real HT use?
It's not that difficult, but it does take a lot of the smaller drivers. You just caculate how much air you need to move at the lowest frequency you want, then decide what your maximum excursion limit on the small drivers. That will tell you how many you need to get the output you want. Your LP filter needs to start at the lowest point you want to play and match the slope of the little drivers' rolloff below Fs. Don't forget to include some gain due to it being a line source, although I don't think it will be the full gain due to the relatively small room volume. It will also eliminate 1 of the room modes.
Except for all those driver holes and wiring, it's a fun little project and using corners it can be virtually invisible in room compared to a nice big boxed sub.
Except for all those driver holes and wiring, it's a fun little project and using corners it can be virtually invisible in room compared to a nice big boxed sub.
I still don't understand how a driver with a Fs of 40Hz will play down to 20Hz, how can it go that far below the drivers natural resonance?
I think the reason that many small drivers <> the bass extension of a single large one is that there aren't any small drivers with very low Fs. Such an animal would have next-to-no output when used by itself because of its tiny Sd... it would exceed Xmax with miniscule input power, and would only be beneficial in a large array.kingdaddy said:
Maybe someone (with limitless funding and time to experiment) would like to try mass-loading the cones of a couple dozen WR125's and making a sub with them.
We could call it the Very Large Small Driver Array Sub.
The driver still moves below Fs and is why we have to be careful with over excursion any time we apply a signal below Fs in any speaker. The spl drops off so sharply below Fs with small drivers because individually they don't move much air. Practically speaking you probably want to limit them to 1mm of excursion, so for you 115db at 15hz would take an impractical number of drivers.
There are small low Fs drivers out there and they are commonly used in computer subwoofers. However, they suffer from the same sonic qualities of typical larger subs. If you used the extreme mass loading to turn a WR125 into a subwoofer, then you're likely to create just another slow sounding sub. I understand that as a practical matter it's a better idea to use a more musical woofer/subwoofer like the kingdaddy is planning.
This all started because I was just trying to make a point that there are plenty of subwoofer drivers out there that aren't able to make anything other than slow bass and it's possible with a bunch of little drivers to do a better job that many sub drivers. Sure they've got the low end output and with much difficulty you can get away with crossing them steeply at 35-40hz and integrate them. Much of that integration problem is due to the sub driver itself because it sounds bad at 80 or 100hz regardless of the room or alignment.
This all started because I was just trying to make a point that there are plenty of subwoofer drivers out there that aren't able to make anything other than slow bass and it's possible with a bunch of little drivers to do a better job that many sub drivers. Sure they've got the low end output and with much difficulty you can get away with crossing them steeply at 35-40hz and integrate them. Much of that integration problem is due to the sub driver itself because it sounds bad at 80 or 100hz regardless of the room or alignment.
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