Open baffle 4-ways under construction

[Kensai]

Well, if you can actually get what you're looking for from dipole subs in your space, that would be really fantastic, but if you're only looking for that octave from sub(s) then its not likely going to make a perceivable difference in sound quality to go with an enclosure (unless its poorly designed or placed, of course).

Personally, I've never appreciated boxed subs of any flavor (though you don't see alot of sealed subs, which generally sound better to me; I have issues with port noise and whatnot).

One interesting thing occurs to me. Dual sonotube style subs, placed behind the OBs to give adjustible difraction/difusion of the backwave using the curved face of the cabinet side.

Cut in this low, you shouldn't need to actually be in stereo, but given the way the rest of this project goes, I would want to stay in stereo as far into the extremes as possible. At 40Hz, I can say that I can't place the source in farfield listening (though in nearfield you can usually tell because there's usually some mechanical failure of enclosure or baffle support that gives it away), but as you start edging up past 60Hz, I find that I can place the source more and more reliably (this is dependent on room; a lively room can screw with my perception to a degree). So the lower your main panels are cut, the less case there is for stereo subs (though dual subs can still be useful, either as I mentioned above or simply to find more than one good placement for your bass reproduction).

So, these things coming together now? Got pics?

Kensai

 

[Paul W]

Jussi,
I don't know your room, but suspect dual subs on the sidewalls will work better than the front wall option. If I understand your layout correctly, the front wall subwoofer location would be 5' further from the listening position than your mains. Best is no delay at all but, depending on how you do signal processing, it may be better to delay subwoofer signal for arrival coincident with the mains than to delay mains signal to arrive coincident with the sub.

Maybe you can finish your main panels first and then experiment with placement of borrowed subs before you build your subs.

Huge dipole will be tough to beat but, for smaller size/more open room plan, system might be okay with stiff-box sealed subs along the sidewalls.
Paul

 

[AJinFLA]

What do you think, is there any point to even consider anything else than dipole(sub)woofers to go along with this project? Is single or stereo monopole subwoofers inferior in this case?

My room is 2,6m (8,5ft) high, 5,2m (17ft) long and 3,7m (12ft) wide. I'll try Linkwitz recommended "ideal" dipole positioning first. Listening spot center against room width, 1,5m (5ft) from rear wall. Speakers in symmetrical 2,5m (8ft) listening triangle toed towards the listener. Another 1,5m (5ft) from panels to frontwall. 0,6m (2ft) from center of the panel to sidewalls.

Therefore placing dipole subwoofers along the sidewalls make the setup pretty tight. Woofers are just along the wall and along the panels on other side.

Other solution is single or stereo monopole subwoofers. Most monopole subwoofer preferences are along the front wall. There might be enough space for single heavy duty cabinet. That would mean a monosub setup. This solution leaves the room a bit more open. Just a single box along front wall, not two along sidewalls.

Recommendations, thoughts, ideas?

Jussi

Jussi,

I'm building somewhat similar, full range main dipole panels. The pressure sources below 50hz will be 4 sealed subs (2 bipole, 2 monopole driver arrangements) spread around the room (Geddes 3 subs with one up by the ceiling was not quite feasible at my current location) per Toole http://www.harman.com/wp/pdf/multsubs.pdf
The nice thing is that each sub does not have to be unduly large, but their summed acoustic output will be sufficiently low in distortion and high enough in level.

cheers,

AJ

 

[Jussi]

At 40Hz, I can say that I can't place the source in farfield listening (though in nearfield you can usually tell because there's usually some mechanical failure of enclosure or baffle support that gives it away), but as you start edging up past 60Hz, I find that I can place the source more and more reliably (this is dependent on room; a lively room can screw with my perception to a degree).

I think the cross should be around 60-80Hz. Perhaps 4th order.

In big W-baffle dipole woofer comes few problems. Or at least potential problems. They are pretty large. That is inevitable for adequate output to match the mains. This causes some decorational problems while mains are kept as elegant and slim as possible.

Then the deep W-baffle has some sonical problems. Squeezing it as small as possible leaves W-baffle openings smaller than moving conearea. This causes pressure in the slots and more or less vibrations and other problems in the structure. A lot less than in vented cabinet since the "vent" is still very large compared to vented cabinets vent.

Then there are some potential resonance problems. Beethoven seems to have (at least according to Stereophile measurements) some resonances at and above 150Hz. So even that 80-100Hz 2nd order cross with 550mm deep W-baffle is a bit compromissed. Those resonances aren't that much down with such slope. Not even with a notch filter.

So, these things coming together now? Got pics?

Still waiting for the woodpanels. They should have been ready this tuesday but so far nothing.

I'll weld those frames and bottomplates together this weekend and put some paint on them. I'll try to take a few pictures. Pictures are always nice. 🙂

I don't know your room, but suspect dual subs on the sidewalls will work better than the front wall option. If I understand your layout correctly, the front wall subwoofer location would be 5' further from the listening position than your mains. Best is no delay at all but, depending on how you do signal processing, it may be better to delay subwoofer signal for arrival coincident with the mains than to delay mains signal to arrive coincident with the sub.

I agree. Althought I don't know how audible such delay is at those wavelenghts.

Huge dipole will be tough to beat but, for smaller size/more open room plan, system might be okay with stiff-box sealed subs along the sidewalls.

At least LspCAD room simulation suggested pretty good behavior with stereosubs along the sidewalls just straight left and right from listener. This might require a bit delay for the subs (6ft from listener to each sub, a bit over 8ft from listener to mains).

I'm building somewhat similar, full range main dipole panels. The pressure sources below 50hz will be 4 sealed subs (2 bipole, 2 monopole driver arrangements) spread around the room (Geddes 3 subs with one up by the ceiling was not quite feasible at my current location) per Toole http://www.harman.com/wp/pdf/multsubs.pdf
The nice thing is that each sub does not have to be unduly large, but their summed acoustic output will be sufficiently low in distortion and high enough in level.

I remember I've read that article but from some reason didn't take that much attension to it. It just make sense. There are some suggestions of subwoofers in each corner or a four subwoofer supplement at the center of each wall lenght. One suggestion is also a single sub at the front and another at the rear but this doesn't match delayvice or the subs need individual crossover channels with digital delay. And while I don't intend to use Behringer or such for my mains the subs would have to be at the same or shorter distance from the listener.

Stereosubs along the sidewalls just at listening spots sides. Or perhaps the single sub on each wall setup. I have my Behringer Ultracurve for prototyping the mains but I'll attend to change it for analogic active filter when the topology and component values are known. After that I could use it in somewhere else. Subwoofer configurations perhaps..

Even two monopoles have quite an advantage in size issues. Compared to both dipolesubs and a single monopole. Four subs can be even smaller. Propably a decent 10-12" closed would do just nicely.

Room acoustically high output dipoles would propably be the best overall solution. Sidewalls are from concrete as well as ceiling and floor. Frontwall is almost 50% window and a door to balcony. Rear wall is 2/3rds thin wall to bathroom and 1/3rd of doorway. So there would be plenty of space for the dipolewoofer to operate and still give pretty much the advantages of its directivity against those hard surfaces.

But how to squeeze it compact enough? I'm considering to use four 12" Peerless SLS woofers on each side but they can't be stuffed in minor cabinet. And I'd need some "D" as well. Prefering 80-100Hz 2nd order cross to mains.

Jussi

 

[Paul W]

I agree. Althought I don't know how audible such delay is at those wavelenghts.

My IB subs are on sidewalls between listening postion and mains, but overall distance to subs is a little further because of on-wall location. Just matching phase gives good results but, compared with delay to match signal "timing", delay sounds a little more "coherent" or "together" (hate terms like that😉. Difference is small, but noticeable in A-B comparision. I must delay mains but, if you can delay sub instead, it should be a better solution.

Dipole may be better to fight concrete walls, but small sealed subs may be stronger below 40Hz...and less intrusive size...too bad we must always deal with compromises!

 

[Jussi]

My IB subs are on sidewalls between listening postion and mains, but overall distance to subs is a little further because of on-wall location. Just matching phase gives good results but, compared with delay to match signal "timing", delay sounds a little more "coherent" or "together" (hate terms like that😉. Difference is small, but noticeable in A-B comparision. I must delay mains but, if you can delay sub instead, it should be a better solution.

Intresting. What kind of IB subs are you using? Pictures?

Dipole may be better to fight concrete walls, but small sealed subs may be stronger below 40Hz...and less intrusive size...too bad we must always deal with compromises! [/B]

Yep. That's too bad. At least the monopoles are more flexible when it comes to overall decoration and positioning. There really isn't much more places than along mains, between main and the sidewall, for dipolewoofers. We have your tv setup in 90 degree angle against the listening direction. Placing a 32" tv 5m (17ft) from the sofa isn't convinient and this would also move the sofa too middle to room center. So there is a sofa at the left flank between listener and main (and potential dipolewoofer), along the sidewall. And at opposite wall is the tv setup. Nasty compromise but can't do better. Turning mains towards the listener there shouldn't be much 1st reflections coming from sidewalls, sofa or the tv setup. But naturally it could be better.

And with that setup I can't place woofers between mains and listener. They have to be along the mains or flanking the listener. And that makes later positioning impossible for dipolewoofers since listener would be in 90 degree off axis angle.

Perhaps monopole has more versatile positioning and configuring possibilities. Mains can be highpassed lower or higher depending on woofers, integrate subs at 40-50Hz 2nd or 60-80Hz 4th order for example. Naturally extending mains lower decrease their output. With Behringer (and adjustable analog highpass for mains) experimenting is pretty easy. Different levels, eq settings, delays and so on. But I don't think I can place four subs in the room. But two should be possible. And at least HT and multichannel music reproduction should have some advantage from monopole woofers since dipoles aren't that strong below 30Hz.

Jussi

 

[Paul W]

Intresting. What kind of IB subs are you using? Pictures?

Two 9x15", one on each side of the listening area.

An externally hosted image should be here but it was not working when we last tested it.

Here is construction page.

IB construction

Your concrete walls seem scary but, if positioning can be worked out, two sealed boxes could be the best overall compromise. Very stiff bipoles like AJ is building might work quite well. I think low distortion content below 40 Hz is extremely important for overall enjoyment. People can really appreciate clean deep bass, not just with movies, but also with music.

 

[Jussi]

Two 9x15", one on each side of the listening area.

Wow. That's what I call a subwoofer. 🙂 Unfortunately I don't have a chance for such solution. It would require holes in the outer wall in the building which isn't that nice figure. 😉

Your concrete walls seem scary but, if positioning can be worked out, two sealed boxes could be the best overall compromise. Very stiff bipoles like AJ is building might work quite well.

Do you have something against vented boxes? 🙂

Ok. At least size is more compact using closed boxes and adequate capacity is achieved with plenty of conearea. 15-18" PA woofer on each side should do the trick.

I think low distortion content below 40 Hz is extremely important for overall enjoyment. People can really appreciate clean deep bass, not just with movies, but also with music.

I agree. It's like a foundation to everything. Not that I'd consider 20-40Hz octave any more important than any other. Actually quite the opposite but in a configuration like this I expect to have full range response.

Jussi

 

[Kensai]

Can't believe IB escaped me. Probably just because I have no way of implimenting such a thing myself, but yeah, I've heard a system with stereo lines of 4x15" IB in the wall behind and to the outside of a set of Maggie mains, and really liked it. Very clean and authoritative, though I would certainly hope so with 8 heavyduty 15" drivers and probably 1000watts/channel the guy was running into them. Really put the air back into the LFE of good DVD sound track, and didn't even break a sweat with acoustic bass while making the instrument sound full size.

Unfortunately, with concrete walls, you're limited to ceiling installations like the monsters Paul is using (nice pics, Paul; I'm envious), floor installations, in a basement if possible or more difficult, built into a seating riser arrangement. I've seen at least a couple of home theater builds with subs built into the cavity formed by their new seating risers, though I'm guessing you're not building a theater here, eh?

Kensai

 

[Jussi]

Unfortunately, with concrete walls, you're limited to ceiling installations like the monsters Paul is using (nice pics, Paul; I'm envious), floor installations, in a basement if possible or more difficult, built into a seating riser arrangement. I've seen at least a couple of home theater builds with subs built into the cavity formed by their new seating risers, though I'm guessing you're not building a theater here, eh?

Yep. IB systems are out of my league. Or at least out of this apartments league. This is just a apartment and I don't attend to invest neighbour apartments just to build a subwoofer. 🙂

Therefore I'll have to settle for something more visible but also movable. These normal solutions.

Italian PA manufacturer RCF has few very potential drivers in their lineup. 15" and 18" models. Both suit in very compact closed and decently compact vented cabinets. High efficiency, solid build, enough excursion (+-8,5mm linear). I tried two different commercial monopoles in our previous livingroom. Both used longthrow 10" closed drivers (REL Q200 and B&W something). I didn't quite got them working without some music material compromisse. So they worked with certain music and just didn't work with something else. But I didn't have highpass filters for mains and the setup was pretty stoneage all together. Behringer with the subs and variable highpass for mains should give plenty of playground to set things up.

But the point.. I didn't got those 10" closed woofers moving that much in that livingroom. It was a bit smaller than our present place but I don't think the size difference is that much. Perhaps +-5mm was enough for low to medium level listening. I used commercial small 2-ways for mains so they run out of breat in the room as well so there weren't loud levels. And I consider myself pretty constraint with the bass. Toneful, fast and dynamic. I don't want the bass to draw any attension and I used the same setup for movie tracks as well. Well blended subwoofers, good uniform soundstage.

Therefore I think two 15-18" PA woofers in closed cabinet should give plenty of performance. I should propably concentrate on something else than the output with such solution. For example compact size and high WAF outlooks. There is no use for extra output if I can't get them placed and setup properly.

Jussi

 

[Paul W]

I knew IB wasn't going to work for you, otherwise I would suggest it. Nothing against ported boxes, but low-Q sealed rolloff seems a better match for most rooms and they can be EQd to any reasonable response.

Haven't tried it yet but if/when my next "boxes" are built, they may be short bipoles with very stiff (curved) walls. Maybe a short cylinder with woofer on each end, braces running from woofer frame to woofer frame...an attempt to eliminate "box sound".

 

[Jussi]

I knew IB wasn't going to work for you, otherwise I would suggest it. Nothing against ported boxes, but low-Q sealed rolloff seems a better match for most rooms and they can be EQd to any reasonable response.

That's propably one reason why vented boxes tend to get those "loose and slow" reviews. Flat extension runs room response rising towards low bass. Naturally extra boom of vented box can also be eq:d out.

Haven't tried it yet but if/when my next "boxes" are built, they may be short bipoles with very stiff (curved) walls. Maybe a short cylinder with woofer on each end, braces running from woofer frame to woofer frame...an attempt to eliminate "box sound".

That bipole sounds funny in subwoofers. The term mainly. They still behave as full monopole since their cabinet size isn't big enough to cause any directivity at those wavelenghts.

But I know what you mean. German Audio Physic has their Minos done in such a manner: http://www.audiophysic.de/minos/index_e.html

It uses two 12" XLS woofers in bipolar setup. So moving masses cancel each other and with relatively flat (12,6" deep) it looks very good along walls. Naturally adequate cabinet space is obtained by adding width and height. But I don't think that's a big problem since there are plenty of walls to place them. Depth is more critical if it gets too large and extends into the room.

Minos is also a closed system with low Q very extended response. Extension is 10Hz and I remember it has some credit behind it. Basically the same idea as in Orion. Low Q response with deep extension. Very low group delay in audible range even while there isn't that much to reproduce below 20Hz.

Jussi

 

[Jussi]

Here is one dipolewoofer concept I scetched some time ago. It's drawn to four 12" Peerless SLS woofers that should give plenty of output down to 30Hz or so. Structures outer walls are missing so the inner configuration is visible. Woofers are stacked on their back where lowest woofers magnet is sunked into to bottomplate. Naturally such system could use separated bottomplate with proper spikes and stuff. This is just the operational part.

Box is shrunk as small as possible to obtain good looks and high WAF. Operational part is 725mm (28,5") tall, 470mm (18,5") deep (resulting 470mm/18,5" "D") and 340mm (13,4") wide at the widest. So it's pretty much as narrow as possible. Drivers are connected in Linkwitz recommended push-pull configuration with force cancellation advantages. And with this configuration the only direction drivers even can move the cabinet is up and down.

But the openings are pretty small. Just 200mm x 125mm (8" x 5") slots. There are two 540cm2 cones pushing air from each vent creating under 1:4 ratio to opening size vs conearea. This causes some pressure in the cabinet. I don't know how relavant that issue is. At least the openings are very open compared to some vented cabinet vents so there shouldn't be any air turbulance noise with that ratio.

Downside is the configuration itself. It's very compact so it has to be build with the drivers already installed. No space to replace them without tearing whole thing apart. And the drivers are on their backs causing hang effect to the cones (which increases 2nd harmonic distorsion).

At least the physical appearance is pretty different to normal box like W-baffles. Would it suit together with my mains, I don't know. At least they would be in sizescale that I could consider placing between mains and sidewalls without closing all the gap between them. But then again they are about 80-90 litre cabinets from the outside. Plenty of output thought so I don't know could similar size monopole sources do that much better and these should allow a bit higher cross with gentler slope than the monopoles. But there is no space to manouver with them. Success or bust basically. And those SLS woofers don't suit that well to any other solution (than dipole).

What do you think?

Jussi

 

[Matt_Tillard]

I really like the look of the ellipsoid style! Using the theoretical SPL worksheet that SL has on his website, I came up with a possible extension of 20 Hz. This is of course with the woofers at their spec'd max excursion of 8mm. For comparison, SL eq's his sealed 12" XLS down to 25 Hz, I think. 20 Hz is pretty good considering. I highly doubt that you would ever want anything more.

If so, I would definately go to sealed box. I hate even turning on my subwoofer, it is so incredibly boomy as it is a vented box. I plan on making a new sealed box and installing a biquad before the plate amplifier soon.

In any case, the design is awesome looking. I'd love to make it just to see it!

 

[Paul W]

Jussi,
Yes, the Minos is the same concept I described. A little different implementation, but basic idea is the same.

I like the styling of the 4 SLS dipole. With small exit area, Fs may be lowered, but that might not be a bad thing. Don't remember who, but someone found a way to model ripoles and this seems like a close relative.

Cavities always seem to present problems with higher xo, so why do you say this dipole would allow higher xo than monopole? Still, monopole should excel below 30Hz. Another way to help reduce vibration would be single downfiring woofers in heavy cabinets.
Paul

 

[Jussi]

Using the theoretical SPL worksheet that SL has on his website, I came up with a possible extension of 20 Hz. This is of course with the woofers at their spec'd max excursion of 8mm.

You mean Linkwitz spl_max1.xls sheet? 20Hz extension is possible but with some output limitations. Or that depends on listening levels and room behavior.

If so, I would definately go to sealed box. I hate even turning on my subwoofer, it is so incredibly boomy as it is a vented box. I plan on making a new sealed box and installing a biquad before the plate amplifier soon.

Do you know why your vented subwoofer sounds boomy? Is it because it's vented or maybe because it runs flat too low causing boosted boomy low bass in the room?

Cavities always seem to present problems with higher xo, so why do you say this dipole would allow higher xo than monopole? Still, monopole should excel below 30Hz. Another way to help reduce vibration would be single downfiring woofers in heavy cabinets.

Measured in octaves they are at least in the same line. Same radiation pattern should allow dipole a bit higher and gentler crossover than monopole. For example 100Hz 2nd order like the one in Beethoven. However Stereophiles measurements on Beethovens woofercolumns weren't that great. Those cavityresonances run pretty close to usable range and the crossover (even with notchfilter) can't kill them to very low levels.

Naturally monopole has its advantages below 30Hz giving it half to one octave more usable range. Designing, simulating and building a closed cabinet is also much more straightforward and less risky than dipoles. Basically most variables are known and there are plenty of software to help designing.

I have done some diagnosis what kind of frequences different music materials have and I'd say most known "bass material" is around 40-120Hz. Below 40Hz levels start dropping (compared to upper areas) and there isn't that much below 30Hz stuff.

Those 20Hz humming sounds are an easy way to get most systems overload but if the system is in balance (as it should be) there is significantly high levels at mid-upperbass and midrange regions so levels that overdrive bass system at 20Hz should also create very loud levels with actual music material.

System adjustments are one advantage for monopole woofers. Just extend mains to say 30Hz or so (as I thought to do without the woofers) and then just highpass them depending on woofersetup. Monopole placement has more variations than dipoles and monopole has more brutal grunt below 30Hz.

Any experiments from XLS woofers? I didn't find that much material from them with forums search. Funny. I thought they used to be very popular drivers.

Stereosetup with Minos style 2x12" XLS woofers grow pretty much just as large as those crankshaft dipoles I've scetched. Perhaps less than 2x12" would be adequate in this environment. And personally I'd invest for quality over quantity. There is plenty of noise in this world as it is...

Some people prefer PA woofers over everything else. Once you try one, you're hooked or something. At least RCF L18P300 has excellent performance in technical terms. I don't think newer models should be any worse. Single 18" fits into relatively flat cabinet if that Minos style is targeted. Nice and slim along the wall compared to normal boxes. Plenty of output, good possibilities to extend response well below 20Hz if needed. Personally I like the idea of large cone moving small amount instead of running 10" woofers with +-1" excursion. I've noticed some correlation to sound quality as well which shouldn't be that big wonder ...

Jussi

 

[catapult]

However Stereophiles measurements on Beethovens woofercolumns weren't that great.

Stereophile's dipole measurements are pretty worthless. They don't have an anechoic chamber so they close-mic everything below 300 Hz or so and splice it into the graph. Obviously that's no good for a dipole. As well, they did some of their measurements of the Beethoven without the active crossover which also applies some EQ.

 

[Jussi]

Stereophile's dipole measurements are pretty worthless. They don't have an anechoic chamber so they close-mic everything below 300 Hz or so and splice it into the graph. Obviously that's no good for a dipole. As well, they did some of their measurements of the Beethoven without the active crossover which also applies some EQ.

With some aspects I agree. But the cavity resonances that I was referring to are very visible there and it doesn't need a anechoic chamber to measure them. How audible are they is another mather. At least they aren't that much down as most resonances require. But the frequencyrange is also different. I guess resonance artifacts from say cone breakup at upper midrange sound a lot worse than these. But still those resonances don't make things better. Naturally radiation patterns need far field measurements from different angles.

Jussi

 

[Jussi]

Intresting. Local distributor offers RCF LF15G401 PA woofers €500;- a pair. That's pretty much the same that eight 12" SLS woofers cost.

Roll a dice? Don't think so. 🙂

Those RCF woofers fit into very small cabinets thought. For a 15" model. Nice Bessel 0,577 Qtc in under 40 litres cabinet. Would make very compact stereopair. They also fit into compact vented cabinets but I don't see that much point in that. Few dB more output but much more complicated construction, limited extension and so on. I guess twin closed 15" woofers deliver plenty in this room...

Here is some information and specs for the RCF woofs:

http://www.rcf.it/vediMacro.phtml/l...LowFrequencyWoofer/WooferLF15G401/product.htm

Good efficiency, low(ish) mms (single 12" XLS has 16g more), enough linear xmax, plenty of mechanical excursion space so they shouldnt bottom with any sane amplifier power...

Jussi

 

[Paul W]

Jussi,
Yes, 2 sealed 15" should be enough. Here is something to consider if you think you might ever use 15" higher in frequency...even the RCF drivers with shorting ring (LFX) have fairly high Le compared to models from BMS and 18 Sound.

Maybe you remember, you were the one who originally pointed me to BMS 🙂. I have been working with the 18N850 on and off for the past few months and like it...my only issue with the 18N is the high MMS which needs a heavy baffle for vibration control.

Many of the pro woofers will work in small boxes, so you have several options if that is the direction you go. If you eventually want to try dipole, you could stack multiples vertically in about the same floor space as the high WAF baffles.
Paul