Prevailing opinion on this forum seems that dipole bass below 40 Hz isn´t the best way to go. IMHO.
The lowest negotiable frequency of a H baffle subwoofer depends overwhelmingly on the driver specs and its equalisation. Even a H baffle of 1m depth wouldn´t add much on your way to reach 20 Hz.
Simply get a driver (or some drivers) with as much displacement and excursion as you need for your intended max. SPL. Then make the H baffle as deep as it needs to be wide to accommodate the drivers. That should be a reasonable starting point.
Rudolf
Re: baffel help
H baffles aren't an efficient use of material and space. The common misconception is that the important distance is how far the waves have to travel before they can meet at the sides. What is important is how much additional distance the rear wave has to travel to get to your ears. The added extra distance resulting from the baffle that the rear wave travels, makes the waveforms less directly out of phase. The less out of phase the 2 sets of waves are and the more low bass you get. Ignoring all other things, they still net to 0 at the sides because they've travelled the same distance and are still directly out of phase no matter how big the baffle.
An H baffle just wastes a lot of wood. Let's take the 100Hx60Wx60D baffle recommended above and assume it's symetrical (baffle centered in the depth and driver in the middle since that is typically what's done). The important dimension is from the baffle to back edge. The added distance for the rear wave is to the rear edge then back to the front of the baffle.
You could cut off everything in front of the driver baffle since it adds no distance. Then cut off the everthing from the driver down which adds no distance because the floor is infinite. Now let's turn it on it's side since having the long dimension on the floor helps because there is only 1 direction to go the shortest path. Then cut off the extra distance to the floor. Now you end up with a backless box 70Wx50Hx30Dcm. Mount the driver at the bottom and you have essentially the same added distance for the rear wave to travel, plus you gain a little since you've increased the effect of the floor boundary.
You've taken the H frame above which needs over 25,000 sq cm to build and turned it into a backless box that needs a little more than 10,700 sq cm of wood. Plus you get a little more bass extension, all in a much more compact speaker.
For each cm of added depth you pick about 2cm of added distance for the rear wave vs 1cm for the symetrical H baffle. Too much added distance introduces cavity resonances and starts to change dispersion like JohnK's NAO woofer, but you get the idea.
wingman said:
H baffles aren't an efficient use of material and space. The common misconception is that the important distance is how far the waves have to travel before they can meet at the sides. What is important is how much additional distance the rear wave has to travel to get to your ears. The added extra distance resulting from the baffle that the rear wave travels, makes the waveforms less directly out of phase. The less out of phase the 2 sets of waves are and the more low bass you get. Ignoring all other things, they still net to 0 at the sides because they've travelled the same distance and are still directly out of phase no matter how big the baffle.
An H baffle just wastes a lot of wood. Let's take the 100Hx60Wx60D baffle recommended above and assume it's symetrical (baffle centered in the depth and driver in the middle since that is typically what's done). The important dimension is from the baffle to back edge. The added distance for the rear wave is to the rear edge then back to the front of the baffle.
You could cut off everything in front of the driver baffle since it adds no distance. Then cut off the everthing from the driver down which adds no distance because the floor is infinite. Now let's turn it on it's side since having the long dimension on the floor helps because there is only 1 direction to go the shortest path. Then cut off the extra distance to the floor. Now you end up with a backless box 70Wx50Hx30Dcm. Mount the driver at the bottom and you have essentially the same added distance for the rear wave to travel, plus you gain a little since you've increased the effect of the floor boundary.
You've taken the H frame above which needs over 25,000 sq cm to build and turned it into a backless box that needs a little more than 10,700 sq cm of wood. Plus you get a little more bass extension, all in a much more compact speaker.
For each cm of added depth you pick about 2cm of added distance for the rear wave vs 1cm for the symetrical H baffle. Too much added distance introduces cavity resonances and starts to change dispersion like JohnK's NAO woofer, but you get the idea.
Fascinating thread, which I've been curiously watching for a while.
Just wondering, could I use small drivers, such as 6" cone diameter types, if I have plenty of them? As I see it, to achieve good dipole bass one needs displacement and appropriate qts, and not much else. (ok, no interior design requirements!!)
I just won an Ebay auction for a fair number, so I have VERY cheap (look like coated paper) drivers to play with. Problem for me will be space in my room!
Just wondering, could I use small drivers, such as 6" cone diameter types, if I have plenty of them? As I see it, to achieve good dipole bass one needs displacement and appropriate qts, and not much else. (ok, no interior design requirements!!)
I just won an Ebay auction for a fair number, so I have VERY cheap (look like coated paper) drivers to play with. Problem for me will be space in my room!
Re: Re: baffel help
there is some validity in your arguments, but:
The more symmetry you rip off your design, the less will it behave as a true dipole. What you are heading for is essentially an u frame with its somehow cardioid dispersion.
If you want a cardioid - that´s perfect. But if you want a real dipole, your baffles better should look the same from the back as from the front.
John,johninCR said:
there is some validity in your arguments, but:
The more symmetry you rip off your design, the less will it behave as a true dipole. What you are heading for is essentially an u frame with its somehow cardioid dispersion.
If you want a cardioid - that´s perfect. But if you want a real dipole, your baffles better should look the same from the back as from the front.
Re: Re: Re: baffel help
Simon, yes you can do that. I know someone who uses 64 4" drivers for high dipole sub. Even that many isn't high output, just nice bass fill for his dipole line arrays. Below Fs, output drops quickly, so you need a fairly steep low pass filter to start at the bottom end to flatten the response and lots of drivers.
With relatively small depths of the U baffle like in the example shown, there may be some effect on dispersion but they are unlikely to result in any audible sonic difference at the seating position other than a little better bass output. If it sounds the same, who cares if you call it pure dipole or not? Same results, less than half the wood, and a much smaller cab.....
You might as well call SL's W baffle dipole sub a cardioid too, since the side panels extend a few inches past the end of the center chamber. Sit on top of one while it's playing and the bass disappears just like if it was "pure dipole".
I just think that people should be made more aware that there's alot of flexibility once you get your speakers out of the box and there are ways to make baffles much smaller with little, if any, sacrifice.
SimontY said:Fascinating thread, which I've been curiously watching for a while.
Just wondering, could I use small drivers, such as 6" cone diameter types, if I have plenty of them? As I see it, to achieve good dipole bass one needs displacement and appropriate qts, and not much else. (ok, no interior design requirements!!)
I just won an Ebay auction for a fair number, so I have VERY cheap (look like coated paper) drivers to play with. Problem for me will be space in my room!
Simon, yes you can do that. I know someone who uses 64 4" drivers for high dipole sub. Even that many isn't high output, just nice bass fill for his dipole line arrays. Below Fs, output drops quickly, so you need a fairly steep low pass filter to start at the bottom end to flatten the response and lots of drivers.
Rudolf said:
With relatively small depths of the U baffle like in the example shown, there may be some effect on dispersion but they are unlikely to result in any audible sonic difference at the seating position other than a little better bass output. If it sounds the same, who cares if you call it pure dipole or not? Same results, less than half the wood, and a much smaller cab.....
You might as well call SL's W baffle dipole sub a cardioid too, since the side panels extend a few inches past the end of the center chamber. Sit on top of one while it's playing and the bass disappears just like if it was "pure dipole".
I just think that people should be made more aware that there's alot of flexibility once you get your speakers out of the box and there are ways to make baffles much smaller with little, if any, sacrifice.
Re: Re: Re: Re: baffel help
Basically, I want to reduce the laziness of my bass
I have 140 6" bass drivers, but in my 1000ft3 listening room, I wouldn't be able to use quite that many! ;o)
I think I've seen the guy's website, can't remember the URL though. If I do end up with some dipole bass, I'd be happy to cover maybe 45-150hz with it, leave my MTM speakers with the mids, and my Tempest sub doing <45hz. (looks like I'll need to have some active x-over here)johninCR said:
Basically, I want to reduce the laziness of my bass
I have 140 6" bass drivers, but in my 1000ft3 listening room, I wouldn't be able to use quite that many! ;o)
Simon,
Are your MTM's dipole ? I just not sure about dipole bass mixed with box mids, but I've had good luck the other way around. Only sealed on the bass matched up well, not ported.
You need to measure those 6's. They may well have an Fs down in the 40's. If so then 45-150hz would be easy and not take an inordinate amount of drivers and 2 compact W baffles would fit easily. If you have adjustable active xovers it would simplify things and you can get away with a much more minimal baffle, since overcoming a 6db rolloff above Fs is much different than an 18db rolloff below Fs.
You might even think about a horn array with them. 45-150hz is easy and doesn't require a lengthy horn. I modeled one up using 16 NSB's and it's really small but tall and fits nicely in a corner. It does 100db/1w/1m 40hz-200hz. You'd need a total Sd of 600-800 to get what you want. If your speakers are in boxed the horn bass might be what you want due to similar room interaction but give you the dynamics you're missing. No one has been able to say that horn bass or dipole bass is better, other than dipole doesn't carry to the neighbors nearly as much. Everyone seems to agree that they're both better than everything else.
If you give me the T/S specs (Sd, Vas, Re, Fs, Qes, & Qms) at a minimum, then I can model it pretty quickly and tell you what gross cabinet volume you need, how many drivers, etc. You'd just have to figure out how to fold it yourself, but that's not too difficult if you don't restrict yourself to a rectangular shape.
Are your MTM's dipole ? I just not sure about dipole bass mixed with box mids, but I've had good luck the other way around. Only sealed on the bass matched up well, not ported.
You need to measure those 6's. They may well have an Fs down in the 40's. If so then 45-150hz would be easy and not take an inordinate amount of drivers and 2 compact W baffles would fit easily. If you have adjustable active xovers it would simplify things and you can get away with a much more minimal baffle, since overcoming a 6db rolloff above Fs is much different than an 18db rolloff below Fs.
You might even think about a horn array with them. 45-150hz is easy and doesn't require a lengthy horn. I modeled one up using 16 NSB's and it's really small but tall and fits nicely in a corner. It does 100db/1w/1m 40hz-200hz. You'd need a total Sd of 600-800 to get what you want. If your speakers are in boxed the horn bass might be what you want due to similar room interaction but give you the dynamics you're missing. No one has been able to say that horn bass or dipole bass is better, other than dipole doesn't carry to the neighbors nearly as much. Everyone seems to agree that they're both better than everything else.
If you give me the T/S specs (Sd, Vas, Re, Fs, Qes, & Qms) at a minimum, then I can model it pretty quickly and tell you what gross cabinet volume you need, how many drivers, etc. You'd just have to figure out how to fold it yourself, but that's not too difficult if you don't restrict yourself to a rectangular shape.
johninCR,
Thanks for the advice. I'd not really ever considered horns, but I'd love to hear what they can do.
My MTMs are just normal ported jobs.
I appreciate your offer to model some horns, as that's something I'm not sure about really.
I should say tho, I only just won the Ebay auction, and probably won't collect the drivers for a week. And even then when I've got them, I could do with building a chip amp or two (project on the way) to power this third leg of the frequency response :-/
Thanks for the advice. I'd not really ever considered horns, but I'd love to hear what they can do.
My MTMs are just normal ported jobs.
I appreciate your offer to model some horns, as that's something I'm not sure about really.
I should say tho, I only just won the Ebay auction, and probably won't collect the drivers for a week. And even then when I've got them, I could do with building a chip amp or two (project on the way) to power this third leg of the frequency response :-/
The reason I initially jumped into this thread was because there is something lacking in my bass response.
It is full range, and capable of fairly impressive SPL, but as you guessed well, it is somewhat limp, and the sound is distant in my poor current listening room.
I sort of hoped dipole bass may negate the small room problems with its different radiation pattern, and bring nimbleness to my bass... stop me if I'm wrong, but this is the whole point of dipole right?
It is full range, and capable of fairly impressive SPL, but as you guessed well, it is somewhat limp, and the sound is distant in my poor current listening room.
I sort of hoped dipole bass may negate the small room problems with its different radiation pattern, and bring nimbleness to my bass... stop me if I'm wrong, but this is the whole point of dipole right?
When you said 1000ft3 , I wasn't thinking. Your room nodes are all up in the middle of the range you want to fill. That combined with ported response on the low end of your mains is probably what is mucking things up.
Did you get that bolting problem resolved on your Tempest? If so, just take it out of the cab and stick some books under the magnet to prop it up. Then cut a hole in a piece of cardboard for a makeshift baffle and set your sub xover to 150hz and give it a listen after plugging the ports on your mains. That will tell you what dipole bass sounds like. In fact I was thinking of using a pair of tempests as dipole subs, by just connecting 1 voice coil to raise the Qts. It shoud work well. Nothing like the spl of vented at 20hz, but good sound.
I have 2 that are still in the boxes.
Did you get that bolting problem resolved on your Tempest? If so, just take it out of the cab and stick some books under the magnet to prop it up. Then cut a hole in a piece of cardboard for a makeshift baffle and set your sub xover to 150hz and give it a listen after plugging the ports on your mains. That will tell you what dipole bass sounds like. In fact I was thinking of using a pair of tempests as dipole subs, by just connecting 1 voice coil to raise the Qts. It shoud work well. Nothing like the spl of vented at 20hz, but good sound.
I have 2 that are still in the boxes.
Hmm, interesting idea. But (yes, excuses!) my sub is downward-firing and in a corner wedged between a sofa and piano, it's all really crammed in!! 
I will try some cardboard baffles with some of these 6" drivers when I get them home (300kg and 140 boxes in my mate's little car will be.... interesting)
Ideally I'd love to have my vented Tempest only doing 30-45hz and below, then a better loading technique for the mid-bass, then what I have currently up top, because I do generally like it, and have nice cabinets. It would be nice to avoid losing them, just add something inbetween the mains and sub. More amps and active will give me many options soon...
Do you remember my sub from another thread?
edit: I seem to require 2db BSC even in this small room, to avoid a reticent lower-mid and generally thin sound. Of course using 2db BSC makes the bass imperfections obvious. Tricky game this hi-fi!
I will try some cardboard baffles with some of these 6" drivers when I get them home
(300kg and 140 boxes in my mate's little car will be.... interesting)Ideally I'd love to have my vented Tempest only doing 30-45hz and below, then a better loading technique for the mid-bass, then what I have currently up top, because I do generally like it, and have nice cabinets. It would be nice to avoid losing them, just add something inbetween the mains and sub. More amps and active will give me many options soon...
Do you remember my sub from another thread?
edit: I seem to require 2db BSC even in this small room, to avoid a reticent lower-mid and generally thin sound. Of course using 2db BSC makes the bass imperfections obvious. Tricky game this hi-fi!
Ahhh! Of course... Yes, that's my main speakers though, the 4 drivers, each with 8 holes, so 32 pieces of wood to attach.johninCR said:
Don't you have the camfered edges on the inside of your driver cutout and were worried the mdf was getting too weak? Did you glue some extra pieces of wood in there to strengthen it?
The things some people remember......
One driver is finished (after reglueing several pieces, several times). It's the most demoralising task I've ever undertaken in this hobby. The pieces of wood break or the glue messes up, or the hole isn't straight enough... Another is nearly done (it's on and off, it's that bad) and at least it sound better with two bolted on firmly (cleaner).
Apologies to those checking on this thread for dipole sub information, I don't mean to hijack it!!!
I am worried about cone excursion,because at open baffle is cone 4 times more active.I have xmax about 8mm.That is little, definitively at resonance when cone gets crazy .So how can be "power deliver" calculated,because I drove my speaker with more than 50wtwo dqys ago, and something started to smell nastily(cone braking)-I forgot that,at the open baffle cone "dances a lot".
1.)If you have some advice,calculation to prevent cone damage,I`ll be happy
2.)I read linkwitz`s and diysubwooers`s articles about dipole, but I dont understand some things:
a)What is of effective diameter(D) U,H,W baffle defined?I know that for flat baffle its just D of sqaure,no matter how its designed(rectangle with deph).
b)what means "out of phase" or "180deg of out phase"?
c)What is d1 lenght at the spaker and 2d2 leght betwen spakers(dipoles),or what effect does it?(from linkwitz page)
thanks for answers and understandig
Dean
.So how can be "power deliver" calculated,because I drove my speaker with more than 50wtwo dqys ago, and something started to smell nastily(cone braking)-I forgot that,at the open baffle cone "dances a lot".1.)If you have some advice,calculation to prevent cone damage,I`ll be happy
2.)I read linkwitz`s and diysubwooers`s articles about dipole, but I dont understand some things:
a)What is of effective diameter(D) U,H,W baffle defined?I know that for flat baffle its just D of sqaure,no matter how its designed(rectangle with deph).
b)what means "out of phase" or "180deg of out phase"?
c)What is d1 lenght at the spaker and 2d2 leght betwen spakers(dipoles),or what effect does it?(from linkwitz page)
thanks for answers and understandig
Dean
to get back to the question at hand, 
I'd like to build a pair of subs with those Pyle 15"s, but it would be really tough to squeeze that H baffle in. I was thinking of making a W baffle (or M baffle) for them. Then, I'd mount my Maggie MMG's on top. Would that work?
How would a person go about figuring out dimensions for the W baffle?
I'd like to build a pair of subs with those Pyle 15"s, but it would be really tough to squeeze that H baffle in. I was thinking of making a W baffle (or M baffle) for them. Then, I'd mount my Maggie MMG's on top. Would that work?How would a person go about figuring out dimensions for the W baffle?
You want to keep the depth of the W baffle as short as the driver dimensions allow. That way you move the "box" resonance of the W baffle as high as possible. If you construct the W baffle in Linkwitz´fashion and use it as a subwoofer (x-over @80-100 Hz), you might succeed without a notchfilter for that resonance.
In Germany many people favor a special version of the W baffle called RIPOL. The opening area of the W is just 1/3 of the membrane area, so Ripoles could be built extremely narrow.
If you split the W baffle in the middle, you get two N baffles (each with one driver) which you can stack. That way dipoles will be as small as they can get.
Rudolf
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