I've been looking at various TL and open baffle concepts, and well, I'm baffled!
Are dipole subs really as easy as they appear to be? I'm considering a very inexpensive pair to mate with my Castle Durham 900s. At 91 dB efficiency. Unfortunately I do not have the resources to buy another amp and would have to build a passive crossover and use a single McCormack DNA .5 DeLuxe to drive it all. Crossover =50 Hz or so.
I did find some inexpensive shielded Dayton DVC 10" subs that I think might work. Mainly music system, but 2 channel "home theater" as well . Specs as follows
Qms=3.2
Qes+.43
Qts=.38
Xmax=6mm
Any ideas would be appreciated
Are dipole subs really as easy as they appear to be? I'm considering a very inexpensive pair to mate with my Castle Durham 900s. At 91 dB efficiency. Unfortunately I do not have the resources to buy another amp and would have to build a passive crossover and use a single McCormack DNA .5 DeLuxe to drive it all. Crossover =50 Hz or so.
I did find some inexpensive shielded Dayton DVC 10" subs that I think might work. Mainly music system, but 2 channel "home theater" as well . Specs as follows
Qms=3.2
Qes+.43
Qts=.38
Xmax=6mm
Any ideas would be appreciated
dipoles probably arent what you're looking for. You need alot of driver cone area(typically achieved by using many drivers) and alot of Xmax. A transmission line would probably work well, but they are more complicated to design than standard box alignments. What are your project goals and budget? How much room do you have for the sub etc...
budget, etc
low budget (neccessarily).
I was thinking something like a dipole similar to the style shown here:
http://www.mfk-projects.com/index.htm
I agree that Isobarics are a good idea. The real concern is mainly being able to drive everything from the single amp that I am using.
thanx
low budget (neccessarily).
I was thinking something like a dipole similar to the style shown here:
http://www.mfk-projects.com/index.htm
I agree that Isobarics are a good idea. The real concern is mainly being able to drive everything from the single amp that I am using.
thanx
Honestly, I think you might want to re-evaluate the choice to do a passive crossover to the subs. At 50 hz and 8 ohms, it looks like a 25+ mH inductor for the lowpass.. and that's really quite large. The largest inductor I saw at partsexpress was a 20 mH iron core, at $20. So, two of those adds up to $40, and that's just a first-order crossover, higher than 50 hz! A higher order crossover will take more than one inductor per speaker, and I think they're larger value components, too.
You can probably get a plate amp with speaker level in/out, and its own internal crossover... apexjr has one for about $90. Then you can get a single Dayton DVC shielded 12" driver, and run it ported.
To sum it up, if you go passive you have to buy a lot of expensive crossover componets, running at $50+, then you need to buy two woofers and build two boxes. Unless you already have big coils of wire and all the wood (or a cheap source for crossover componets...), it really might be cheaper to get the Apex Jr amp and a single 12.
Just my two cents.
You can probably get a plate amp with speaker level in/out, and its own internal crossover... apexjr has one for about $90. Then you can get a single Dayton DVC shielded 12" driver, and run it ported.
To sum it up, if you go passive you have to buy a lot of expensive crossover componets, running at $50+, then you need to buy two woofers and build two boxes. Unless you already have big coils of wire and all the wood (or a cheap source for crossover componets...), it really might be cheaper to get the Apex Jr amp and a single 12.
Just my two cents.
Also, it will be very difficult to obtain the correct level for the sub and because the impedance will be all over the place the performance will be rubbish unless you resort to a fairly complex network of impedance compensation. Not to mention the (unavoidable) noticeable lack of damping through the crossover frequency.
Subwoofers are best done active. A passive crossover at that frequency will have lots of series resistance, and never give you the performance you desire. Joe is correct. By the time you purchase decent parts for a passive crossover, you will spend more than the cost of a plate amp from Parts Express.
Nanook Hi theres no such thing as a fast subwoofer,especially once you filter it at 70hz 🙄
What matteres infact,is the DAMPING supplied by the enclosure type.
For critical,high quality musical reproduction Id look at IB,dipole,horns and sealed boxes[or overdamped BR with high quality driver],and chose the right woofer for the right enclosure that you can fit.
Yes mikee Subwoofers are not really fast, but I believe group delay plays an important role in this "fastness" perception.
mike.e said:
Nanook Hi theres no such thing as a fast subwoofer,especially once you filter it at 70hz 🙄
I don't know what you're talking about, the subwoofer in my car can break 100mph, no problem! Thats pretty damn fast!
The idea that a subwoofer need not be 'fast' because higher frequencies are filtered out is not true, or at least it's an incomplete analysis. The proof is simple:
Imagine that you're listening at low volume. A drum hit comes along. The cone moves .01"
Now turn the volume up. Listen to the same cut. Same drum thwack. Now the cone has to move .5"
By definition, the signal itself has the same waveform. But the high volume playback scenario requires a much faster risetime in order to reproduce that waveform. Do a little math. Convince yourself that achieving a greater cone transit in the same amount of time requires much faster motion--or higher acceleration, if you prefer. This, in turn, relates to cone mass, motor strength, damping, etc., but the upshot is that subwoofers require much more juice than many people realize. And they still only do a poor job of reproducing the signal. Distortion specs for speakers are typically on the order of 1 to 5% even at average listening volumes. Matters deteriorate quickly at higher volumes. I've seen distortion figures of 20%. Now, that's nasty. Is it any wonder that speaker distortion specifications are rare? Big panel speakers (ESLs, planars) reduce this considerably, but are, well, big. So we're left considering dynamic drivers as a practical solution for those who don't have room for something like the big Sound Labs ESLs, which can go as deep as you like and do it damned fast...but they're the size of a barn door and expensive. Bummer, but there it is.
The same concept recently came up in another thread but looked as though it was going to degenerate into semantic squabble. We've had more than enough of those, and I don't care to participate.
Grey
Imagine that you're listening at low volume. A drum hit comes along. The cone moves .01"
Now turn the volume up. Listen to the same cut. Same drum thwack. Now the cone has to move .5"
By definition, the signal itself has the same waveform. But the high volume playback scenario requires a much faster risetime in order to reproduce that waveform. Do a little math. Convince yourself that achieving a greater cone transit in the same amount of time requires much faster motion--or higher acceleration, if you prefer. This, in turn, relates to cone mass, motor strength, damping, etc., but the upshot is that subwoofers require much more juice than many people realize. And they still only do a poor job of reproducing the signal. Distortion specs for speakers are typically on the order of 1 to 5% even at average listening volumes. Matters deteriorate quickly at higher volumes. I've seen distortion figures of 20%. Now, that's nasty. Is it any wonder that speaker distortion specifications are rare? Big panel speakers (ESLs, planars) reduce this considerably, but are, well, big. So we're left considering dynamic drivers as a practical solution for those who don't have room for something like the big Sound Labs ESLs, which can go as deep as you like and do it damned fast...but they're the size of a barn door and expensive. Bummer, but there it is.
The same concept recently came up in another thread but looked as though it was going to degenerate into semantic squabble. We've had more than enough of those, and I don't care to participate.
Grey
Due to the lack of [enter]s I only skim read that.
I have no intention of having a 'squable'-its a waste of minutes of my
life.
I can imagine a higher rise time on a larger amplitude signal.
My point being, debating about 'fast' cones with high bandwidth is essentially meaningless-because what people mean,is that the bass is overdamped or underdamped and this determines the quality even at low SPL
You wont find any subwoofer that is 'too slow' or 'late' or 'doesnt have the required acceleration'
What you will find are subwoofers with high Qt values which ring for several cycles on a sealed box,and misaligned ported boxes with high Qt drivers causing horrible underdamped resonance.
http://www.diyaudio.com/forums/showthread.php?postid=366547#post366547
I have no intention of having a 'squable'-its a waste of minutes of my
life.
I can imagine a higher rise time on a larger amplitude signal.
My point being, debating about 'fast' cones with high bandwidth is essentially meaningless-because what people mean,is that the bass is overdamped or underdamped and this determines the quality even at low SPL
You wont find any subwoofer that is 'too slow' or 'late' or 'doesnt have the required acceleration'
What you will find are subwoofers with high Qt values which ring for several cycles on a sealed box,and misaligned ported boxes with high Qt drivers causing horrible underdamped resonance.
http://www.diyaudio.com/forums/showthread.php?postid=366547#post366547
Stick them in a poorly designed enclosure where you end up with high group delay and you will indeed end up with something that is 'late' ....mike.e said:
Group Delay is another topic altogether,and has been discussed already ad nauseum im sure.
I shouldve said "any well designed subwoofer"
I shouldve said "any well designed subwoofer"
fast subwoofers
Hi Nanook,
I do not know what is your budget for this project but if you want clean sound from a subwoofer you must go for an active one. Instead of reinventing the wheel you can get a nice active direct servo sub from www.rythmikaudio.com
THe DS350 kit (amp and 12" servo subwoofer) will cost you about US$400. You will either have to build your own enclosure or order one from rythmik audio. They have a smaller and cheper sub DS250 kit as well but for my tastes it's too small. Check the site. It is probably the best sub on the market for that money.
Cheers,
Janusz
Hi Nanook,
I do not know what is your budget for this project but if you want clean sound from a subwoofer you must go for an active one. Instead of reinventing the wheel you can get a nice active direct servo sub from www.rythmikaudio.com
THe DS350 kit (amp and 12" servo subwoofer) will cost you about US$400. You will either have to build your own enclosure or order one from rythmik audio. They have a smaller and cheper sub DS250 kit as well but for my tastes it's too small. Check the site. It is probably the best sub on the market for that money.
Cheers,
Janusz
If you want to get technical...😉
Speed is velocity. Drivers operating in their passband above resonance are acceleration devices (power in is directly proportional to acceleration; F=ma becomes BLi = ma). SPL is in fact a function of acceleration; double the acceleration, you double the SPL output.
Speed is the integral of acceleration over time. Double the time of the acceleration, you double the velocity.
As you drop an octave, you double the time of the frequency, hence doubling the speed (assuming equal power throughout the waveform).
Note this is why excursion quadruples as you drop down an octave - distance is the integral of velocity over time, meaning that halving the frequency requires 4X the excursion.
So to be technical, the "fastest" subwoofer is the one that plays the deepest the loudest. Speaking strictly in terms of cone velocity...
Dan Wiggins
Adire Audio
Speed is velocity. Drivers operating in their passband above resonance are acceleration devices (power in is directly proportional to acceleration; F=ma becomes BLi = ma). SPL is in fact a function of acceleration; double the acceleration, you double the SPL output.
Speed is the integral of acceleration over time. Double the time of the acceleration, you double the velocity.
As you drop an octave, you double the time of the frequency, hence doubling the speed (assuming equal power throughout the waveform).
Note this is why excursion quadruples as you drop down an octave - distance is the integral of velocity over time, meaning that halving the frequency requires 4X the excursion.
So to be technical, the "fastest" subwoofer is the one that plays the deepest the loudest. Speaking strictly in terms of cone velocity...
Dan Wiggins
Adire Audio
Technically your right Dan, technically, but you know and I know technical means very little in a double blind listing test,
as fast is a quality that means different things to different people.
A subwoofer we know can not be fast or slow, no matter how powerful or weak the motor so in order to get the fast sound is more to do with bass alignment;
The enclosure is what most people miss out on.
I don’t think bass units are bad or rubbish in the sense most people use this term.
Psychoacoustic principles is how to make speakers IMHO, every time I try and do the maths and get reports back from wigged professors and companies, I get baffled, what there telling me is how to be linear and uniform, like everybody else.
When I go back to what I know and feel and experiment with, I get something that is alive and effervescent with character and soul.
Trapping that feeling is the magical part and is very difficult.
What I try to do is make a speaker that sounds as close to the microphone as possible, the only way to do this is to have the microphones and understand the pick up patterns that come close to sounding like the human ear, or my ear at the very least, but all woofers add there own characteristic, now some say this is not the electronic truth and should be engineered out without exception, the same people would argue there is no God and we have no soul.
The fastest subwoofer was the question, is that the important question really?
I think people should ask what characteristic of sound quality they like and never make camps in the loudest or deepest or most expensive brand, it takes us away from the music and into something much less enjoyable.
I don’t believe we need to have uniform hi-fi systems with designed perfection, we need diversity and character and with this comes many different technical make ups, the only way to find out what we like is to listen, nobody can tell anybody else what they like is bad or wrong, we can only do that to ourselves
😀
as fast is a quality that means different things to different people.
A subwoofer we know can not be fast or slow, no matter how powerful or weak the motor so in order to get the fast sound is more to do with bass alignment;
The enclosure is what most people miss out on.
I don’t think bass units are bad or rubbish in the sense most people use this term.
Psychoacoustic principles is how to make speakers IMHO, every time I try and do the maths and get reports back from wigged professors and companies, I get baffled, what there telling me is how to be linear and uniform, like everybody else.
When I go back to what I know and feel and experiment with, I get something that is alive and effervescent with character and soul.
Trapping that feeling is the magical part and is very difficult.
What I try to do is make a speaker that sounds as close to the microphone as possible, the only way to do this is to have the microphones and understand the pick up patterns that come close to sounding like the human ear, or my ear at the very least, but all woofers add there own characteristic, now some say this is not the electronic truth and should be engineered out without exception, the same people would argue there is no God and we have no soul.
The fastest subwoofer was the question, is that the important question really?
I think people should ask what characteristic of sound quality they like and never make camps in the loudest or deepest or most expensive brand, it takes us away from the music and into something much less enjoyable.
I don’t believe we need to have uniform hi-fi systems with designed perfection, we need diversity and character and with this comes many different technical make ups, the only way to find out what we like is to listen, nobody can tell anybody else what they like is bad or wrong, we can only do that to ourselves
😀
- Status
- Not open for further replies.