| Phergus_25 |
I recently made a pair of Austin A126s, and I have yet to do measurments, but in thinking about adding a sub of some sort. I would like to use the speakers natural roll off and only crossover the sub. And suggestions as to what works best with fullranges?
-greg |
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| zobsky |
| quote: | Originally posted by Phergus_25
I recently made a pair of Austin A126s, and I have yet to do measurments, but in thinking about adding a sub of some sort. I would like to use the speakers natural roll off and only crossover the sub. And suggestions as to what works best with fullranges?
-greg |
a horn sub works well for back loaded full-ranges. |
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| Phergus_25 |
Any good ones around. Im having a hard time getting through the threads to find waht is decided upon to be good.
-greg |
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| Phergus_25 |
I was directed to the Autohorn, but im afraid that it might not go low enough. Any othr suggeestions or experiance with the auto horn?
-greg |
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| Ray Collins |
Zobsky,
Which Horn Subs are you using and which do you recommend?
Thanks
Ray |
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| zobsky |
For what its worth, I use an autotuba currently with a set of line arrays. Good to around 30 Hz. I used to use (and still have) a 12" ported adire shiva tuned to 17Hz but that simply isn't efficient enough for an efficient set of speakers. It also doesn't seem to match "tonally" . I tried the same shiva in a sealed enclosuree but just didn't like the sound.
YMMV |
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| RobWells |
The 'usual suspects' for horn subs are the labhorns or the Bill Fitzmaurice stuff (tubas).
You need to work out if you have enough space for horn subs as they're not small.
If space is an issue maybe try the punishers down to 40hz and use something more conventional for the bottom octaves.
Rob. |
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| planet10 |
We have been building push-push Extremis subs... 1 per side is nicest. The extended range makes them easier to integrate... with room gain, the vented enclosure (pushing aperiodic) gets them into the mid 20s. 2 fit in a 16-17" cube (but we use lots of shapes)
dave |
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| Ray Collins |
Dave,
I considered the apex Jr. push-push sub several weeks ago but it was too small for my application because they needed to do double duty as sofa end tables in my small HT (13'x14' room). I had all but decided to build a pair of single driver 12" or 15" sealed subs probably using the Dayton RS series drivers when I saw your new Extremis based design. Tell me about your new design and its suitability for my application.
Ray |
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| Ray Collins |
Dave,
As I understand it the benefit of this configuration is that the cone excursion is cut in half and vibrations are reduced along the lateral line of the box. Is there anything else?
I noticed that you set the drivers high to get as close to the satellites as possible. Will placing the subs on each side of my couch, which is across the room from my front speakers, undermine the sub's performance?
I think that I may be enamored with the bipole push-push configuration and therefore considerating an inappropriate application. What say you?
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
the cone excursion is cut in half |
That happens any time you use 2 drivers
| quote: | | vibrations are reduced along the lateral line of the box. |
This is the big one... most of a driver's newtonian force is along the central axis of the cone/voice coil. This energy is usually transmitted to the box (and in some cases becomes so large that subs have been known to "walk". In a push-push arrangement we are attempting to actively cancel this force. How successful we are depends on how ridigly we can couple the drivers.
An extreme example is this coupling arrangement:
using these drivers which have a built-in provision for bolting thru the pole-piece to the cabinet
In practise we usually just align one of the internal (plywood) braces so that the magnets are tight up against the brace. Most of the lower frequency vibrations are coupled to the other driver where they cancel, and higher frequencies are dissipated in the brace and anything that does get to the outside walls has so little energy that it doesn't do anything untoward.
Besides a small potential improvement in fidelity because the driver is not allowed to rock the box, a dramatic reduction in the energy mechanically coupled to the box occurs. This means that almost all box wall resonances have to be excited by internal air pressure and that energy is significantly less. The net is a bif reduction in box coloration. A side effect is that because less mass is needed to counter driver movement, we can use thinner box material further pushing up the panel resonances (where there is even less energy to excite them), lower cost (less wood), fewer strained backs (less weight), and marginally smaller box size.
With a push-push woofer we have no hesitation of building with 12 or 15 mm plywood.
| quote: | | I noticed that you set the drivers high to get as close to the satellites as possible. |
This was specific to the application, where the sealed FE167s are being actively XOed to the stereo woofers at 106 Hz (using SY's gyrator based tube XO -- i can hardly wait for him to publish that article). In this specific application i expect room gain to get these things to reach into the high teens and that they will need to be throttled back by using aperiodic damping in the port (system just being installed so i don't know how it will work out in the end)
| quote: | | Will placing the subs on each side of my couch, which is across the room from my front speakers, undermine the sub's performance? |
You just need to make sure that you adjust the box so that the drivers aren't firing into the couch (ie one forward, one back, or some arrangement where the exit for the drivers is actually in the middle of the box (figure 8 or torus topology)
| quote: | | I think that I may be enamored with the bipole push-push configuration and therefore considerating an inappropriate application. |
At the frequencies a sub operates at, it is acoustically omni-polar and this is the case no matter how many drivers we use -- 1, 2, 20...
dave |
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| Ray Collins |
Dave,
Thanks for the comprehensive reply. I apologize for the delayed response but my wife priortized my agenda and.....
Is the push-push configuration suitable for a sealed enclosure?
When calculating the box volume for the push-push dual driver do I simply double the volume for a single driver subwoofer? (Accounting for braces also)
I am an advocate of the build it light and build it strong school so I really favor the push-push configuration. I suppose it derives from having built an airplane.
My need to employ the subs as end tables puts dimension restrictions on them. They must be about 24" tall and about 14" wide with the length/depth up to 30". This will provede enough top surface for remotes, drinks etc. Can your new dual Extremis 6.8 design be adjusted to work?
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
Is the push-push configuration suitable for a sealed enclosure? |
yes
| quote: | | When calculating the box volume for the push-push dual driver do I simply double the volume for a single driver subwoofer? (Accounting for braces also) |
yes
| quote: | | I am an advocate of the build it light and build it strong school so I really favor the push-push configuration. I suppose it derives from having built an airplane. |
My use derives from having -- over the last 35 years -- figured out that that is what sounds best (and a big side benefit that you don't strain your back as often)
| quote: | | My need to employ the subs as end tables puts dimension restrictions on them. They must be about 24" tall and about 14" wide with the length/depth up to 30". This will provede enough top surface for remotes, drinks etc. Can your new dual Extremis 6.8 design be adjusted to work? |
You just need to keep the net internal volume to 42 litres + the port (i prefer the long, high aspect ratio slot ports -- that is if you go with the reference ported design). I have at least 4 configurations drawn up, and i'm sure more will follow (the idea of having the drivers facing openings in the middle of the box (figure of 8 topology) is one i'd like to have a look at.
Given that the volume you need to fill is quite a bit larger than the skinny dual extremis (~10x20x22") that might be a way of helping to fill up the space.
I'll do a quick and nasty sketch in sketchup to give you an idea of what i'm talking about.
dave |
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| planet10 |
| quote: | Originally posted by planet10 the idea of having the drivers facing openings in the middle of the box (figure of 8 topology) is one i'd like to have a look at.
Given that the volume you need to fill is quite a bit larger than the skinny dual extremis (~10x20x22") that might be a way of helping to fill up the space.
I'll do a quick and nasty sketch in sketchup to give you an idea of what i'm talking about.
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Driver pair is the cylinder in the middle. Top could be glass or wood or stone or what-have-you.
dave |
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| planet10 |
Looking at my sketch, you would have to work out the logistics of actually installing the driver (ie making sure that you could get your screwdriver in to tighten the bolts (i'd use hex bolts & insert fittings for ease of install & safety)
dave |
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| Ray Collins |
Thanks....now I have something to chew-on for the next few days.
Am I correct in assuming that you prefer ported/BR
encosures over sealed enclosures when using the push-push configuration?
I agree concerning the high aspect ratio slots; it just looks apropos.
In your sketch the drivers are not positioned so that the magnets are coupled;
does this still provide the same vibration control? |
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| planet10 |
| quote: | Originally posted by Ray Collins
Am I correct in assuming that you prefer ported/BR
encosures over sealed enclosures when using the push-push configuration?
I agree concerning the high aspect ratio slots; it just looks apropos. |
I am actually not a big BR fan. This particular config for the extremis works well. The long high aspect ratio port pushes the box towards aperiodic and if necessary a bit of foam in the port pushes it to completely aperiodic -- this allows for tuning once the box is in the room (there is a specific blue foam i use that comes as part of the packing in Apple parts boxes). With room gain low 20s is possible.
| quote: | In your sketch the drivers are not positioned so that the magnets are coupled;
does this still provide the same vibration control? |
If you dimension the cross part of the 8 appropriately, you can actually get the magnets to touch. Imagine the cyclinder as the extent of a pair of woofers stacked magnet-to-magnet.
dave |
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| Ray Collins |
Dave,
I have studdied this and I think this is a little too complicated for the "yield" or as my Dad would say "too much sugar for a dime." Also, I think I need a little more air moving ability.
What do you think about Lynn Olson's dual Scan-Speak driver design? http://www.nutshellhifi.com/ME2txt.html#swlocate
Ray |
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| RobWells |
Hi Ray,
My old 3 ways used 2 x s-speak 8565-01's per side. Each cab was ~120L sealed. The sound quality was excellent, but for me they were not subwoofers. They do get deep enough for music (not home cinema), but do not go particularly loud. For home cinema I ended up using 3 x tempest 15" drivers below 40Hz, crossed to the scans at 24dB/oct.
Eventually the SQ of the tempests got on my nerves and I moved onto labhorns. Much happier now.
For a music only system, if you don't want 'live' levels then 4 x the scans could well be the ticket.
Hth,
Rob.
My old scanspeaks
Thinking out loud, maybe use 4 8565-01's per side crossed to a pair of 15's (maybe servo driven ?) at around 25Hz may well sound nice, and do dynamics. |
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| Ray Collins |
Thanks Rob, that is the kind of input I need!
Ray |
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| RobWells |
I guess the question is how loud / low you want to listen ? and of course your budget....
100% agree with Dave on the BR stuff..
Rob. |
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| Ray Collins |
Well it is for a small room(13'x14') HT and a little music; however, my wife and I do not like it really loud. I do like it accurate and low. I have a generous budget but I don't think $800 to $900 per driver makes much sense in this situation...or does it?
Ray |
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| RobWells |
I should have also asked how much space you have. Driver cost depends on the app. I use 2 labhorns, the driver cost to you would be about $500 as a rough guess. They are huge though.
A 'decent' sealed system would probably cost more but take up less space. (would also lack the output of the horns, but have more bass extension)
I've always fancied making a sub with the peerless xls series of drivers. They model well in tiny cabinets and that means you can multiple them up in small spaces. 4 xls 12's per side, push push should be pretty interesting.
Rob. |
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| Ray Collins |
| I am limited to a 14" wide and 24" tall front on the cabinets; the depth is 30" or less. This allows them to serve as sofa end tables. I don't think that the 12" drivers will conform to this dimension restriction or will it; if so are the Vifa's preferable to the 12" Scan-Speaks? |
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| planet10 |
| quote: | Originally posted by Ray Collins
I am limited to a 14" wide and 24" tall front on the cabinets; the depth is 30" or less. This allows them to serve as sofa end tables. I don't think that the 12" drivers will conform to this dimension restriction or will it |
You should be able to -- just -- make a 12 fit into a 14" wide cabinet (i assume you need to put the driver on a 14" face?) I am hot on the new 12" from CSS. It would be easy enuff to rejig the aspect ratio of the sealed sub to meet your dimensional requirements -- i think you'd even have room to do a push-push per side -- with sufficient power 4x12" should move enuff air to make your smallish room bulge if needed -- 4 even fit into your budget.
SubDuction Data
16" cube plans
dave
disclosure... i will be selling these -- a 2nd woofer to add to the Extremis in my limited line-up |
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| Ray Collins |
Thanks Dave. How important is it to use the Golden Ratio in the re-configuration of the box?
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
How important is it to use the Golden Ratio in the re-configuration of the box?
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In a sub -- not very important at all. Everything happening inside is much higher in frequency than the sub will produce (excite), and from the outside the box the driver does not see the box.
The biggest concern is detailing the mounting so that it fits in 14". If i was doing push-push i might even consider 15mm sides.
dave |
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| Ray Collins |
I don't understand the use of 15mm sides. Please explain.
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
I don't understand the use of 15mm sides. Please explain.
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It would give an extra 6 mm room inside breathing space.
dave |
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| Ray Collins |
Dave,
I understand; I suppose that an additional 1/2" to make it 14.5" wouldn't matter.
I could mount the drivers on the wide sides of the enclosure which would also solve the breathing problem. In this orientation would it matter that one of the drivers would be firing into the arm of the sofa?
Ray |
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| planet10 |
You might find yourself exciting the sofa... is there any clearance at all?
And you wouldn't be able to do push push (you need probably 20" to do that)... i'd just fit it into 14".
dave |
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| Ray Collins |
Would it work if the drivers were offset but still magnet-to-magnet? The centerline thrust of the drivers would not be in the same plane but it would still be push-push.
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
Would it work if the drivers were offset but still magnet-to-magnet? The centerline thrust of the drivers would not be in the same plane but it would still be push-push.
Ray |
Usually you have to couple the magnets with a brace, so if that brace is quite rigid you should get most of the effect.
dave |
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| Ray Collins |
That is what I thought Dave. They will be offset but snugly integrated with a rigid brace which should preserve the desired physics.
I started a new thread on recycling Bozak drivers which I thought would garner your interest. Do you have any T/S parameters on them? They are getting plentyful on Ebay.
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
I started a new thread on recycling Bozak drivers which I thought would garner your interest. Do you have any T/S parameters on them? They are getting plentyful on Ebay. |
The last set of Bozaks i've seen were in the late 70s...
dave |
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| germpod |
Are there paticular types of drivers that prefer a Push-Push system, like highly effeciant or low QTS for example? What is the sound advantage of a Push-Push system over standard single driver in a ported box.
I am asking because I am looking into building a sub to with my pair of Harveys and subs seem much more complicated to me for some reason. I saw the Harveys and instantly knew that is what I wanted, and I do not understand all the subwoofer stuff well eneough to have that moment. |
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| planet10 |
| quote: | Originally posted by germpod
Are there paticular types of drivers that prefer a Push-Push system, like highly effeciant or low QTS for example? What is the sound advantage of a Push-Push system over standard single driver in a ported box. |
No... push-push is a mechanical arrangement that cancels the newtonian motion of the drivers so that it is not passed onto the box.
| quote: | | What is the sound advantage of a Push-Push system over standard single driver in a ported box. |
Quite a bit more downward dynamic range, less box sound.
dave |
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| germpod |
Thanks Dave.
I am going to look into it a bit more to gain better understanding of subs as a whole. They seem to have different properties than mid range drivers so you have to design differently. |
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| planet10 |
It isn't that the properties are different... just the scales. A loudspeaker needs to be considered in the light of the frequencies it reproduces. Unique to a sub is that the wavelengths tend to be much larger than the box or the driver.
dave |
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| Ray Collins |
Dave,
How does the SQ/performance of the push-push sub compare to a servo controlled sub like the Rythmik?
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
Dave,
How does the SQ/performance of the push-push sub compare to a servo controlled sub like the Rythmik?
Ray |
Never heard a servo sub... but they are attempting different goals. I have little doubt that a push-push servo-sub would be better than a single driver one... besides the basic benefits of push-push i suspect that the amount of correction required by the servo would decrease cleaning that aspect up as well.
dave |
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| Ray Collins |
So a push-push servo sub and the point of diminishing returns begin to clash?!
Ray |
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| planet10 |
| quote: | Originally posted by Ray Collins
So a push-push servo sub and the point of diminishing returns begin to clash?!
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I wouldn't say that... as with any feedback system, the right way to do it is get as good a piece of kit as possible before looping the feedback since the less feedback/correction you actually have to use the better -- you get a system that has greater stability and fewer artifacts.
dave |
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| germpod |
| When you do a push-push system you just double the box size, do you double the port also, either a single port that is twice the size recomended for a single driver or two ports the same as recomended for single driver? |
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| planet10 |
| quote: | Originally posted by germpod
When you do a push-push system you just double the box size, do you double the port also, either a single port that is twice the size recomended for a single driver or two ports the same as recomended for single driver? |
Yes... that is pretty much it. Port area doubles, length stays the same.
dave |
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| paulspencer |
I have tried push pull with my previous subs - AE speakers AV12. I put drivers on opposite sides of the box, one with magnet facing out and polarity reversed. What I noticed:
1. Less cabinet vibration compared to just one driver
2. Slightly tighter sound
Push pull gives a subtle improvement and back to back allows a box that isn't as thick and heavy.
Then I got Rythmik Direct Servo. Comparing just one to my previous sub was a big improvement, much bigger than what you get from merely using back to back and/or push pull. If you want the best of both then go with Rythmik dual kit, which has two 12" drivers and you can then go push pull as well. I suggest a prototype so you can decide if you think the improvement is worth having the magnet pointing out in one sub.
If you really want the best that you can possibly get, then this is what I'd do. Get the Rythmik dual kit and horn load it! I would be doing that myself, except that I found out the horn I had in mind is just too big and will kill the room. :smash: |
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| Ray Collins |
What about a Rythmik dual kit mounted back to back in a push-push configuration like Dave favors?
Ray |
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| RobWells |
Martin Logan use 3 drivers 'push push push ?' in their Descent sub. My friend has one of these in a fairly small room and the sound quality is excellent.
Maybe try 3 x Rythmik audio servo 12's to make a bigger version?
http://ultimateavmag.com/subwoofers/107/
Rob. |
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| planet10 |
| quote: | Originally posted by RobWells
Martin Logan use 3 drivers 'push push push ?' |
They don't take it as far as they could, relying on the baffles to tie the drivers together.
dave |
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| RobWells |
Thats a shame - I kind of assumed there was some serious bracing inside to lock the 3 magnets together.
Oh well, once more a point to team DIY :D
Still one of the best subs I've heard though.( for music at least )
Rob. |
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| paulspencer |
| How do they compare to your labs? |
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| RobWells |
Thats a hard question to answer Paul.:D
My friends system is dipole - Martin logan ESL's, All driven by Krell stuff. It's a wonderful sounding system. I'd have to hear the sub in my system to do a fair comparison. I however feel no need to get rid of my labs. And of course if you want to watch a film at reference...
Obviously my system lacks the very low stuff now(It's only flat to 20hz atm) But I'm working on a soution for that bit. Space gets to be a problem with horns and living room sized listening rooms:bawling:
Rob. |
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| paulspencer |
ONLY 20 Hz? That's a bit wimpy isn't it?!
I wonder if a tapped horn could be a good way to get down lower. I hope to get around to doing one soon with the aim of getting a little lower than 20 Hz, say 15 Hz. |
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| RobWells |
You do notice some lack of bass on dvd stuff, but music is fine.
All good for now. This post by GM piqued my interest, but it's definitely in the dedicated room category.
Rob.
Post #338 |
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