Ricci

Time for me to start clearing out gear that has accumulated and is no longer needed. Funds from equipment sold is used to buy new sub's or gear or otherwise fund Data-Bass All gear is slightly used but in good working order unless otherwise noted. I will only ship to the 48 lower US states. I am willing to meet up for local sales in the Louisville KY area. I accept PayPal or cash for local sales.

There may be a tiny difference between the outer vents and the center ones due to oroximity to the side wall, but I'd have to measure it. Go with whatever works for you. It shouldn't made a difference.

What band around what time?

Might break the cabinet joints on em if pushed too much further. LOTS of pressure developing. 4 K20's is theoretically only 6dB more and that's not factoring in compression of which there surely would be a large amount. So maybe another 3-4dB? Not worth it. If one of the biggest touring amps isn't enough it's time to add more cabinet/subs.

Exactly...There's good development and practices in each field but the number of companies putting it all together are limited. Good drivers work regardless. I like the Funk drivers. Some of them are very good but the prices are so far beyond other competitive products it makes it hard to consider them for systems that may end up requiring 8, 16 or more drivers.

A bit more motor is an understatement! It's a looooong way from 0.44 down to 0.20. I'd take even lower if I could get it. Alpine makes good woofers and I've used a bunch but like most they haven't discovered the importance of sub efficiency yet. The reason I would like a 12" is for a number of reasons. It could be cheaper and easier to make a very efficient woofer with less cone area and use multiples than to do a single super woofer. Plus they can fit in geometries and shapes that the larger drivers can't. Keeping cost down would be the main thing.

Skram has 4 vents. Each is equivalent to a 6" round port. With 1 vent blocked and 3 open you have the equivalent of three 6" vents still operating. Tuning drops to about 24.5Hz. There should still be a lot of headroom down to 20Hz in room. 2 vents open is 20Hz tuning, etc... 21DS115 is a good match if it is the cheapest option. I can't really answer about the MW comparison. I've never heard one or modeled them so I'd rather not speculate.

Good paper Kipman. Hadn't seen that one that I recall. Ironless motors aren't a new idea, but they often turn out to be very expensive and have a lot of stray field. Stray field is wasted field. There are many good ideas out there for improving moving coil speakers linearity and efficiency. A lot of the time there are easy ways to improve drivers that don't involve exotic new technologies, or materials. Very good, relatively inexpensive devices could be made with standard materials and construction, but usually they aren't or have what I would consider to be an Achilles heel. A big part of it seems to be that driver designers simply do not design woofers with their priorities in the same places that I would. I think a lot of that stems from fixation on certain goals or ideas rather than looking at the whole picture from a birds eye view. Some of it is due to thinking that is to some extent crystalized around old school design philosophy. In a nutshell what I want to see is a driver with linear xmax well beyond what's needed for the app, which reduces distortion related to suspension and BL variation greatly. This is technically possible quite easily, but it increases Mms and suspension stiffness, which has to be countered with more motor strength. There are limitations on how much power can be absorbed by a driver or put out by an amp, or pulled from a outlet, so efficiency needs to improve too, which requires more powerful motors also. Doing both of those opposing things, cost effectively is the big issue. Examples of a couple of drivers I would like to see... A 12" sub with a legit 25mm xmax, 3" voice coil, neo motor, shorting rings, Fs around 25Hz and a Qts in the neighborhood of 0.200. Weight <30lbs. No one makes this type of 12" woofer that I'm aware of. It wouldn't be a cheap $150 woofer but there's no reason it would be an $800 woofer either. The closest thing I've found from any of the major brands is one of the old Peerless XLS 12's and it has half the xmax and not much in the way of power handling. It's also overpriced for what it is. I have designs for these non existent drivers. As far as a big pro woofer goes...Something like the RF-19 concept is a good start. Basically the in between of it and the 21NTLW5000 would be a good start. For pro audio the RF-19 needs a serious diet. The 1000g mms and super tight suspension squelch the efficiency. We don't need the 34mm coil overhang and 80mm long coil winds. That's twice as much overhang as the highest xmax pro woofers currently on the market. For tunings at 25Hz and above that much excursion just isn't needed. Cut the coil length back to something more appropriate for the app like 60mm long winds which would still leave something like a 24mm overhang with A 12mm gap, which is still quite a bit beyond any of the pro woofers on the market and would remove 40mm of the total coil length and 25% of it's mass. The former would be shortened by 40mm too. The huge, heavy surround could be switched out for a lighter cloth style one. Due to the big reductions in moving mass and less excursion potential the huge 12.5" spiders could be downsized to 10 or 11" spiders with higher compliance and less weight. There are probably some weight savings in the aluminum dust-cap and cone to be had as well. Even the leads are way overkill and probably add a few grams extra. I'm pretty sure you could drop 300 or even 400g off of that driver fairly easily which would do worlds of good for its efficiency. A much lighter and shallower frame and 60mm shorter motor would greatly reduce weight and depth.

In a home sized space they should do well to 25Hz with all vents open. Should only be roughly 6dB down outdoors at 25Hz. In room will probably boost it back up a little. Double Skram should have a little bit extra on a single Skhorn at the limit, assuming both are using the same drivers.

Facing the corner should be a little bit smoother through the crossover region >80Hz. Other than that experimentation and measurements would give the best answers.

That escalated quickly! Which Danleys are those?

This gets back to the issues with the amount of power available though. The horns might still be more sensitive than a pile of DR's and they will probably be lighter and cheaper to build. 30 lab12's weigh a ton by themselves. Wiring complexity as well. A pile of double 18's would be a good comparison say 8 to 10 of em. I'm jealous Paul got to hear those Danley's. Those are some outrageously big and powerful subs no doubt about that. More powerful drivers could potentially get even more out of em if they really got pushed hard enough.

Large aggressive thread screws. I like 1/4 x 20 lag screws for back mounting these 21" pro drivers.

The Behringer specs are optimistic. However you still cannot find amplifiers with more power for less $$$. The built in dsp is worth the extra $50 too. Most other amps with comparable DSP quality are 2 or 3x the price. If you have a receiver with XT32 and the processing is only needed for the sub by all means skip the minidsp and get the DSP equipped Behringer amp. The fans are loud on these. A lot of guys have done fan mods on them to use quieter fans. There are plenty of threads covering it at AVS forum. I've not personally fan swapped one. The dsp section in the amplifier has a limiter section that would be set in the amp if needed.

2 problems with that approach as well. Power handling. There's a practical limit to how much power you can supply to a single cab and how much power a single coil can absorb. Efficiency. There is room to make transducers more efficient but even if we get the reference efficiency way up we still run into practical limitations on the amount of output that can be achieved from the amplifier limitations that will exist. The MAUL is a pretty good study of this even though it isn't sealed. It was amp limited with a whole K20 bridged into it at 4 ohms nominal. As a practical matter supplying more power to the cab isn't an option. Even using the 40" M-force unit, which is the most efficient driver I'm aware of and assuming unlimited xmax and power handling, which it most definitely is not, cannot get there in a sealed design the same size as the MAUL. There isn't enough power available even with a large cab and incredible efficiency. This type of avenue should be explored further and pursued but there will always be room for vented and other bandwidth limited cab designs due to the need for more output over a limited range with less power.

It seemed ok in FEM but I did notice that this type of neo design does start to generate those stray fields below the gap. I assume they are not of sufficient strength to cause issue. 7 component motor though. Machining of the top aluminum cap would've been expensive and the quote I got on the T-pole / backplate and outer case were $$$! Looked good on paper but I worried about alignment issues, motor assembly and cost. How to assemble with charged neo is a whole other deal too.

Nice! Here's something I was fooling around with back in 2013/2014.

Good points made SME. Vented subs are tough. They are arguably the most common type of sub because they can be reasonably compact, easy to construct and design, can have good response and offer large output advantages around the vent tuning. With a vented design we usually want to maximize vent area. This involves either a higher tuning, larger cabinet, or longer vents with worse pipe resonances. The pipe resonances are a major issue IMHO as is trying to stuff extremely long vents into a cab with limited dimensions. Back in the day with lower capability drivers this wasn't as much of an issue but the physics of port operation hasn't changed while the drivers and amps keep getting more powerful. Basically modern designs are pushing the ports further into compression than ever before. At the same time the demand is for everything to get smaller. Designing a high output vented sub is an exercise in knowing there are major compromises with the vent and making peace with it. Compression and noise doesn't just affect bass reflex subs either. Horns and TL variants are not immune if they have small areas in the path length. It doesn't matter what type of alignment it is if there is a lot of air movement being forced through a relatively small area. Even if it is buried in the cabinet so that you don't hear chuffing it can still compress and shift the output. Akabak and ABEC3 are capable of looking at the air speeds at various points in the system. It’s a good exercise for those who think that because it isn’t technically a “port” or bass reflex it isn’t a consideration. In general horns and TL's do fair better due to much larger areas though. These types of designs can also have ringing and group delay issues just as bad or worse than vented designs. There is a trend in the vented sub measurements that shows that compression sets in earlier than many think. It gets progressively worse from there. Another takeaway is that they do not seem to brick wall absolutely but the compression keeps growing. Also the driver starts to unload as the vent compresses and the driver will start to exhibit higher excursion near tuning which somewhat offsets the vent compression. So if the driver is already able to overload the port badly what good is an even more powerful driver, more excursion, more power handling, more amp power? In theory more maximum output potential, less compression, less response shifting, lower distortion. In effect the envelope of acceptably linear operation is pushed a little higher. This has measurable effects even when the system is not being pushed beyond where the lesser driver is comfortable. At some point it is debatable whether these improvements are audible or worth it. Despite the fact that the vent might severely limit the extra performance near the tuning there should still be some performance gains even if they are miniscule at the vent tune itself. There is a lot going on above vent tuning which includes the area of maximum driver excursion and most of the audible bass bandwidth. The improvement may not be as large as what would be seen in a sealed system but it can still show an improvement overall. You may see little improvement near vent tune though if the vent cannot cope with the demands. The Skhorn has what I would consider as enough vent area at the 30Hz tuning to keep compression and noise minimal. Enough meaning barely adequate LOL. Blocking vents for a 25Hz tuning isn't too bad of an impact but it does worsen the vent compression and noise a bit. Blocking for the 17Hz tune puts it into a state of being under-ported like most subs. Vents can work great but keeping airspeed and compression low is always difficult. Almost every sub tuned below 25Hz is under-ported. All of the home audio style subs are. Some of them woefully so once you look at the specifics of the design. The rare exceptions are some of the higher tuned pro subs and car audio subs but it's a lot easier to get massive area when the tuning is >30Hz and the cab is big. Using drivers with higher capability and lower tunings only makes it worse if you want to use the extra capability. The MAUL has a 730cm 12” pipe that’s 41” long for a port and HR sims a max airspeed of 120m/s when bursted with a bridged K20. It should be at about 30m/s with 70 volts. There really wasn’t a “win” to be had there. I wanted a 10Hz tune but the vent area would be severely compromised to an extent I was uncomfortable with. A 41” vent length is already far longer than I wanted it to be and the vent resonance is lower and more severe than I wanted. About 15Hz was as high as I wanted the tune to be to make it worthwhile. So at the end of the day I am not happy with the vent area, length, tune, or resonance. I still love those subs though and vent compression is the last thing I notice when I hear them. Maybe that’s because other systems are even worse or maybe it’s because a 12” pipe will handle quite a bit before it gets out of sorts. With the Skram most of the extra size over half of a Skhorn is extra vent area and a little bit more air volume. When designing a vented sub you'll often see that with a smaller vent it leaves more air space in the cab which helps with a lower tuning or more vent area and also helps boost the efficiency at the vent tuning. A lot of BR subs are designed that way. I go the other way and go for the largest vents I can get away with in the cab that will still hit the tuning required. This will not result in the most sensitive or efficient small or medium signal response but it gains it back and then some at high output. The big tradeoff is longer vent lengths and the associated pipe resonance.

I apologize for nothing! You're the one that said more pics at higher resolution and MOAR graphs!

Hello Joselo. Welcome. If you buy the 3000DSP you won't need to buy the minidsp. Personally I'd probably go that route. The less boxes, wiring and complication the better. I played around with a 3000dsp and it did pretty well, very well even considering the cost. DSP works well too. It does not sound good when it clips but a limiter set a bit below the clip limit will help with that.

I know how it is. Need a few more hours in the day. It's a shame we have to sleep.

Looks like this Ora company is doing a lot of work with graphene for cones and domes. I think we are far more likely to see small multimedia transducers using this before we start seeing 18" graphene composite cones. The name of the game with this stuff is a very thin layer to beef up a thicker carrier material or perhaps a multi layer foam core sandwich. I do own a fishing pole with some graphene in the blank.

Kyle is right. Xmax is based off of either physical measurements of the coil and gap geometry, a distortion percentage (with a certain signal, at a certain frequency in a certain loading), or measurements of things such as BL, suspension compliance or inductance shifting at various positions of the coil in the gap. There are ways to measure the amount of driver excursion but you need one of these other methods to determine if it is within the limits set for xmax. It's a complicated subject. The "Myths" section on xmax covers some of it. When I make note of excursion behaviors for driver tests. I am not rating the drivers xmax and I'm not measuring the distortion, or BL loss, etc. I am simply making a note of how the driver behaves in free-air, at what point it becomes obviously distorted or loses it's composure, where it stops responding to power increases with more excursion, how loud the mechanical operational noise becomes, etc. It's a set of general observations about how the driver seems to respond to high excursion in a very basic sense. What all of this means for your drivers and app is this. Don't worry about the xmax rating of the drivers. What matters to you is at what point the drivers start to sound bad or become in danger of damage. With some careful probing of their limits with measurements and test signals you can determine where they start to lose it and at what voltage that occurs.

Hey Ti did you ever get a chance to put some voltage to these yet? Just wondering. Looked like you were about done a few weeks back.

Thanks for giving us some feedback on the results. I think you may be the first to hear these. I'd say I'm surprised by your impression of them but I'm not. Ha! Some close measurements would be great if you get a chance. If you do try a few inches away in between the 2 sets of vents and a very close response in the middle of one of each set of vents.