Which drivers for highly custom, small enclosure?

[suttondesign]

Hi All. I'm re-doing my main setup and need to build a new pair of decorative subs with more oomph for a new, larger living room, about 2500 cu. ft. The subs have to sit on a thick walnut bottom shelf, 12-1/2" deep by max. 18"h. The room opens up broadly to another living area, and standing waves are a minimal problem.

Smaller is better because, if possible, I conceal the enclosures within oversized books, hollowed out with a saw. Alternatively, the enclosures will be walnut-veneered ply to match surrounding bookcases. I am building the enclosures using a wide assortment of woodworking and cabinet tools. I can just fit 12" drivers if I do some trickery with the router to make them fit a smaller enclosure.

Price not an issue.

The subs cross over very low to Linkwitz LX521.4, which aren't designed to cover below 30hz. The subs will use separately-housed (and hidden) MiniDSP (icepower) plate amps with DSP.

So, my question: A single, 12" downfiring sealed sub (Rythmik or Morel or CSS) or the Seas L26ROY 10" downfiring with two passive matching Seas 10" radiators on the sides? Both would give me the performance I can reasonably hope to get. BTW, the various Peerless drivers seem impossible to get now, so please don't suggest them.

Please, no criticism of my question or comment that I have to build something bigger or that I'm wasting my time or that it all depends so no generalizations are possible etc. My space parameters are fixed, so I have to make the best of an enclosure no larger than about 1.5 cu. ft. internal volume.

Patrick

 

[MAB]

Hi All. I'm re-doing my main setup and need to build a new pair of decorative subs with more oomph for a new, larger living room, about 2500 cu. ft. The subs have to sit on a thick walnut bottom shelf, 12-1/2" deep by max. 18"h. The room opens up broadly to another living area, and standing waves are a minimal problem.

Smaller is better because, if possible, I conceal the enclosures within oversized books, hollowed out with a saw. Alternatively, the enclosures will be walnut-veneered ply to match surrounding bookcases. I am building the enclosures using a wide assortment of woodworking and cabinet tools. I can just fit 12" drivers if I do some trickery with the router to make them fit a smaller enclosure.

Price not an issue.

The subs cross over very low to Linkwitz LX521.4, which aren't designed to cover below 30hz. The subs will use separately-housed (and hidden) MiniDSP (icepower) plate amps with DSP.

So, my question: A single, 12" downfiring sealed sub (Rythmik or Morel or CSS) or the Seas L26ROY 10" downfiring with two passive matching Seas 10" radiators on the sides? Both would give me the performance I can reasonably hope to get. BTW, the various Peerless drivers seem impossible to get now, so please don't suggest them.

Please, no criticism of my question or comment that I have to build something bigger or that I'm wasting my time or that it all depends so no generalizations are possible etc. My space parameters are fixed, so I have to make the best of an enclosure no larger than about 1.5 cu. ft. internal volume.

Patrick

I wouldn't do the Seas L26ROY with the passives in a small cabinet. You will end up with some odd peaking, no matter how you mass-load the passives. For subs in small boxes , I would go sealed. The L26ROY would work well by itself sealed with DSP to augment the bass. Two of them in small cabinets will likely keep up with the LX521.4

I think you would be better off with 2x L26ROY's in per sealed box than the small-box passive radiator alignment. I have these subs with dual passives, but my box is bigger and allows the passives to operate in a better alignment. That being said, with DSP I am thinking of leaving passives (and ported) designs behind. While ports and radiators do reduce the cone motion of the actives drivers at resonance, I find that is a minor improvement compared to the flexibility of sealed subs with DSP. And those two passives cost a bunch. And do take more effort to construct the boxes. Of course, there are other great 10" subs. And if you can fit a long-stroke 12" in a sealed cabinet, that would work great too.

If you use dual-passives, you are right to put them on opposing sides of the cabinet, since two of them will rock the cabinet all over the place. And a single-passive will limit the output (the passive cone has huge excursion at resonance!!!), so two is really what is needed, or a single passive with ~twice the cone area as the active.

 

[suttondesign]

I wouldn't do the Seas L26ROY with the passives in a small cabinet. You will end up with some odd peaking, no matter how you mass-load the passives. For subs in small boxes , I would go sealed. The L26ROY would work well by itself sealed with DSP to augment the bass. Two of them in small cabinets will likely keep up with the LX521.4

I think you would be better off with 2x L26ROY's in per sealed box than the small-box passive radiator alignment. I have these subs with dual passives, but my box is bigger and allows the passives to operate in a better alignment. That being said, with DSP I am thinking of leaving passives (and ported) designs behind. While ports and radiators do reduce the cone motion of the actives drivers at resonance, I find that is a minor improvement compared to the flexibility of sealed subs with DSP. And those two passives cost a bunch. And do take more effort to construct the boxes. Of course, there are other great 10" subs. And if you can fit a long-stroke 12" in a sealed cabinet, that would work great too.

If you use dual-passives, you are right to put them on opposing sides of the cabinet, since two of them will rock the cabinet all over the place. And a single-passive will limit the output (the passive cone has huge excursion at resonance!!!), so two is really what is needed, or a single passive with ~twice the cone area as the active.

Did you mean to suggest 2 L26roy in each box (ie, 4 total)?

 

[moonlight rainbow dream]

Have you spent any time in WinISD? I think that would answer all of your questions in much better detail than any of us can off the top of the head.

I recently did a bunch of modeling and will just toss out the suggestion to take a look at Wavecor subwoofers + passive radiators (ports are just impossible to fit if you want to tune low in very small boxes). If you go to their site, they have PDFs with a bunch of potential tunings for each driver. In general, they go super deep in tiny boxes unassisted by DSP, and the distortion performance data I've seen from audioxpress is crazy good. Downside is they probably will not go as loud as options like the CSS.

 

[DVDdoug]

I agree with the above.... WinISD or similar to predict and optimize performance. You probably will do better with a sealed design, but that also depends on the driver characteristics and WinISD can help you with that.

Two 10-inch drivers have more piston area than one 12-inch but that's also a trade-off and usually a smaller driver (or less piston area) goes deeper in a small box (with less maximum output as a tradeoff).

With a small sealed box you'll probably need DSP/EQ to get the best performance, but with EQ and more power you can overcome the air resistance/compression in the box, whereas a ported box drops-off faster below resonance/tuning and it's harder to compensate with EQ and amplifier power.

 

[MAB]

Did you mean to suggest 2 L26roy in each box (ie, 4 total)?

Yes. 2 drivers in each box, or even better 4 drivers each in their own 0.75 cubic foot cabinet. With DSP of course! The advantage of four is you can adjust positions, etc. You might even find you only need two or three, and you will have a spare or two to integrate with other systems if you want. Subs are great. Multiple subs are even greater!

 

[suttondesign]

Have you spent any time in WinISD? I think that would answer all of your questions in much better detail than any of us can off the top of the head.

I recently did a bunch of modeling and will just toss out the suggestion to take a look at Wavecor subwoofers + passive radiators (ports are just impossible to fit if you want to tune low in very small boxes). If you go to their site, they have PDFs with a bunch of potential tunings for each driver. In general, they go super deep in tiny boxes unassisted by DSP, and the distortion performance data I've seen from audioxpress is crazy good. Downside is they probably will not go as loud as options like the CSS.

winisd isnt working too well for me. i have bassbox coming tomorrow. i did see the new wavecor 10” in voicecoil mag. i will definitely check it out. i do not need high spl, just real, enjoyable sub bass.

 

[suttondesign]

thank you everyone for being so nice!

 

[jhaider]

So, my question: A single, 12" downfiring sealed sub (Rythmik or Morel or CSS) or the Seas L26ROY 10" downfiring with two passive matching Seas 10" radiators on the sides? Both would give me the performance I can reasonably hope to get. BTW, the various Peerless drivers seem impossible to get now, so please don't suggest them.

I would not use a downfiring driver, because why introduce gravity as an extra force pulling in one direction of travel?


In your shoes I would likely use two ScanSpeak Discovery 10s, which is an evolution of, and the closest thing to, the OG Peerless XLS/XXLS 10 currently available, or the SB Acoustics sw26 8 Ohm in a dual-opposed configuration. L26ROY is, IMO overpriced today. Either SB or Disco should be a higher output solution than your 9" Revelators.

I use the SB SW26 in teeny tiny cabinets (like 0.25 ft^3 each) in the front corners of our living room, and they can gracefully handle plenty of boost and power. A PWR-ICE250 would be very nice with those. (Parts Express now carries the 250ASX2 as well - 125 and 250 use the same hardness so it's not too expensive to hot-rod a PWR-ICE125 now...)

I also wouldn't bother much with modeling. It matters a lot for vented alignments, but closed boxes are easy. Get good drivers, build a solid cabinet, and EQ based on measurements.

 

[mcdn]

As a fellow Linkwitz owner, I am keen to see what you settle on! I did look into low-bass-specific subs myself for a while (see https://www.audiosciencereview.com/...er-design-to-operate-_below_-40hz-only.43836/)

I modelled some options in VituixCAD (which is well worth the learning curve by the way). In principle, to keep up with the LXSub4 SPL capability you do need a ported enclosure or PRs. But @ctrl did some analysis which shows what is not intuitively obvious, that room gain below the first room mode is so much better for sealed enclosures that it almost completely removes the ported advantage.

So go sealed, at which point all that matters is xMax and power handling. You said budget isn't an issue. A pair of L26RO4Y drivers will fit back-to-back in a 12" box, and each driver is rated at 500W peak power. With 1kW of power you will get 100dB @ 20Hz from each box, so about 106dB total before room gain. There will be distortions due to the nonlinearity of air compression at these extreme pressures, and the box will need to be very strong.

Here's a screenshot of a basic simulation of that in a 20L enclosure.

 

[sigbergaudio]

@mcdn That sounds like a very small enclosure for dual ROYs.

 

[voodooless]

Don’t forget Dayton UM10 or AE IB10AU-4 (if you can get one), or even Dayton Reference.

You may also be able to use a passive radiator setup: one 10” + 2 PRs. It will give more output down low, but probably costs almost as much as two full woofers.

 

[mcdn]

@mcdn That sounds like a very small enclosure for dual ROYs.

It is very small, but it meets the design criteria. I imagine there would be problems with the linearity of the air in the box. And probably with heat dissipation if used at high power for long periods. Siegfried Linkwitz estimated the air compression nonlinearity to bring about 2% 2nd order harmonic in a 40L enclosure at 20Hz for his Thor subwoofer, which is very reasonable. Even 10% distortion at 20Hz is inaudible. And using opposed drivers cancels a lot of other distortion, not to mention vibration.

So yes, on the face of it it seems extreme, but is it wrong?

 

[sigbergaudio]

OP says he can have up to 40ish liters, so I think I'd do that if I had the space. 40l is still a pretty small enclosure for two ROYs, but I think more realistic. If smallest possible cabinet is a goal, one may ask if he really needs 4 drivers. An alternative could be just a single driver per cabinet and do ~20l each.

 

[mcdn]

It’s a very specific design goal of filling in from 10Hz-35Hz. The dipole bass from the LXsub4 only goes down to 30Hz.

Obviously going to a 30 or 40 litre enclosure helps with distortion and with power requirements, and if there is space it should be done! But it doesn’t fundamentally change the SPL, given the drivers are operating near xMax.

Halving the number of drivers would reduce the SPL by 6dB though. And opposed drivers have lots of other advantages so long as cost isn’t an issue.

 

[MAB]

So yes, on the face of it it seems extreme, but is it wrong?

It is not wrong. Not sure why the concern over small sealed boxes. Pretty small is the wrong term, high Qtc is more useful. Unless you won't or can't use EQ to transform to flat response.

Your approach is awesome. And you correctly state the tradeoffs. I bet they sound great.

 

[fineMen]

... downfiring with two passive matching Seas 10" radiators ...

The speakers' spiders tend to creep. The lower the resonace frequency (is: interaction weight/strength) the more. Over time they'll develop a sag which first will significantly degrade performance and eventually make them fail.

 

[suttondesign]

With the group's comments, I am leaning towards capable 10" drivers, opposed, in a somewhat longer (that is, on the bookshelf, wider) enclosure, allowing me to do, say, 1.6-1.7 cu ft. So I'm coming down to the shallow SB or the Seas L26ROY. Or that 10” Wavecor also looks great. With EQ and room gain, I should be fine in this room for the volume levels I'm after.

Here's the room, and you can see the existing subs inside books. The one behind the right speaker is hard to spot. We've added more drapes and soft furnishings since this picture was taken.

 

[jaakkopetteri]

The L26RO4Y requires way less volume than the L26ROY, for what it's worth. The Dayton RSS265HE is also a great option when it comes to T/S for small enclosures but the Seas has proven linear excursion. You could also fit two of the notch larger Daytons (RSS315HO-4) in 40 liters with a Q of 0.6 . The SB has a great track record but the excursion is pretty nonlinear...

 

[fineMen]

The L26RO4Y requires way less volume than the L26ROY, for what it's worth. The Dayton RSS265HE is also a great option when it comes to T/S for small enclosures but the Seas has proven linear excursion. You could also fit two of the notch larger Daytons (RSS315HO-4) in 40 liters with a Q of 0.6 . The SB has a great track record but the excursion is pretty nonlinear...

As the board insists on having a downfire (sagging) config, let me say that some p/a speakers may have more or less the same excursion to offer, a stiffer suspesion with less of a sag, and with necessary (room) equalization it may go as deep as one could wish for in a closed box when used doubled up, because the magnet systems are usually exceptionally strong and will take the amps/ current without counter induction / demagintization.

Times the solution doesn't come from in the obvious ;-) Cost of no concern? Go for BMS neo drivers or JBL's XBL^2 p/a woofers.