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The PaleHorn

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Figured I might as well post a little bit about this sub. I've had the design basically finalized for a year and a half or so, if not longer, but I have not had a chance to get the amplifiers done, the drivers in, the cabs built, testing etc...Things are on the move now though.

 

The goals for this design are similar to the Othorn.  The bandwidth of interest is 25-90Hz primarily. The application would be for music or live sound in very large spaces or outdoors,with huge headroom from a cab that is reasonably handled by one guy with some wheels, or man handled by 2 men. Had to be small enough to fit one in a small SUV or a pair in a larger SUV or van. It isn't a typical professional bass bin because of the extra extension. I've found that with subs that do not really get down below 35Hz with power, which is most "pro" subs honestly. I start to miss some of the lowest bass fundamentals in music, which in the last 10 years, has really started to dip into the 25-35Hz range more often. The tradeoff for 25Hz extension is reduced sensitivity and output in the middle and upper part of the bass bandwidth, but by using an extremely powerful and expensive driver, this can be overcome a bit. The goal is not to blow away other high power pro subs on the market with sheer loudness, but to offer comparable headroom in the 40-100hz bass range as a more typical bass system of similar external cab volume, while extending 1/3 to 2/3 octave lower with real power. I also expect low distortion, good sensitivity, and controlled LF decay to go with lofty dynamic headroom.  

 

Basically the idea behind this design is to take the performance of the Othorn, which I was very happy with the result of and push the ball a bit further, while also fixing a few minor things I felt I could have done a bit better in the Othorn in retrospect. To that end the cabinet form factor will still be the same 36x36x24" and it will still employ a single 21" driver. However the driver will now be the B&C 21 IPAL instead of the 21sw152. Due to the beefed up nature of the IPAL driver, which offers: Roughly 40% excursion, even better efficiency, a heavier voice coil with higher power handling and a reinforced cone; the result should be a system of comparable sensitivity, slightly better maximum output 40-100Hz, slightly better long term thermal behavior at high power and just a hair more extension with notably more output at 20-30Hz. The Othorn tune is right about 28Hz while the Palehorn will come in slightly lower at about 26.5Hz. Also the cabinet design is entirely different. There isn't a single piece that is shared between the two. Everything internally is different. The cabinet for the Palehorn should be significantly stiffer especially around the driver and should be more immune to cabinet vibration.

 

Additionally the system will be powered with PS IPAL amplifier modules which offer extremely advanced DSP processing and real time monitoring of behavior of the driver and amplifier as well as active feedback of the system both electrically and acoustically with real time correction of the driver behavior. The feedback system has shown to provide some improvements in distortion, ringing, overshoot and overall tracking of the input signal. I am very excited to see some results on a higher order system. How PS has managed to apply tracking and correction to resonant or 1/4 wave systems is very interesting since previously the consensus has been that it could only be applied effectively to sealed or infinite baffle systems. There are a number of questions that have yet to be answered such as how the system will behave with a complex driver loading, how it will behave with ULF frequencies below 16Hz, whether the 21IPAL driver will survive the forces and pressures that will be on the cone in this cabinet, as things are really being pushed very far out in left field (BAD things are a very real possibility with the internal forces involved), how bad of an effect air compression will be on the system at near maximum outputs, etc...LOTS of questions to still be answered. 

 

Note I will NOT be sharing DIY plans for this system at this time. I may not even show the cab internals. It is possible that I may at some point after I've gotten all of the testing done on a finished pair and know for sure what the good, the bad and the ugly of it are, but that will be some time off. I will show all of the measurements and other data I collect on them though.

 

 

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Very cool, Josh. I've been waiting to see the Palehorn come about for some time now.

 

It's unfortunate that this will not be a shared plan but after reading about the system and the integration with the IPAL amp/dsp system I totally get it.

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Really Scott the reason has to do with the fact that this cab is very sensitive to the driver and even more than most subs you can't just throw any old driver in there. The drivers out there with enough motor are very few even moving down in cone size to 18's or 15's. All of them are expensive. I can't tell you how many emails and pm's I got asking what $200 driver works good in the GH or OT. I even had a guy who build an OT cab which may or may not have even been braced all the way or built well and used a driver completely unsuited for it and then said it wasn't very good. DUH!

 

Plus I can't have anybody building my new cabs before I thoroughly wring them out first! Plus I won't know whether further tweaks are needed or whether it is a total fail until I do.

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Wow! Sounds like awesome project Josh, can't wait to see you put this thing through the ringer.

 

Also,

 

It's funny I recognize Austin, Scott and Luke immediately by their Avatar, and Dave for his lack of.... Lol.

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Anything with the possibility of topping the OT is worth keeping an eye on... Will be following along Josh.  Looking forward to it. 

 

Welcome aboard. I think it will be worth checking out...I mean we are talking about an active, feedback loop controlled tapped horn that should be even more powerful than the OT after all.

 

I guess that means I need an avatar here too?

 

All of the cool kids have one so yes.

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cool.

 

it will be interesting to see how the amp/software deals with multiple resonance points.  seems like it would need some sort of training and/or translation to know what to expect.  have you experimented with it on a ported cab yet?

 

i've read about the ipal system quite a few times and I'm still at a loss for what the practical benefit is of creating a synthetic t/s parameter set.  the only thing that I can think of is that one could get the benefit of really good damping (massive bl/re) while offering a little more sensitivity* from an increased vas.  but is that benefit really worth all the cost/complexity?

 

i doubt you want to answer, but have you decided on a lower compression ratio on this one?  ;-)

 

* just above tuning in a ported cab.

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Hey John,

I’ve done a lot of thinking on it, but I still have many unanswered questions myself. For one thing observance of polarity at the driver connection and placement of the DPC sensor are both critical. Otherwise system stability issues can result. Polarity must be reversed in the software if needed. This gives a clue. The system tracks the input signal, the output voltage, the output current, back EMF from the driver and the pressure from the front of the driver cone at the baffle. A great many things can be calculated from this information when combined with some user input data such as driver parameters, SD, RE, MMS, etc... Impedance, peak and average power applied, driver excursion behavior, probably impulse response, etc…Can be gathered.  All of this information is gathered and electrical feedback plus the DPC sensors acoustic feedback can be compared back to the input signal in nearly real time. Let’s say that you have a tapped horn with all of the crazy impedance spikes and resonances inherent to that type of design. How could the IPAL feedback possibly work with that type of system and know what the system is supposed to behave like? Let’s say that the input signal for a kick drum comes in and the fundamental is near a resonance in the TH pass band at say 70Hz that would typically ring. The IPAL system can sense that there is significant difference in the buildup of pressure near the driver and ringing after a “perfect” reproduction of the input signal would have stopped and can adjust the driver cone movement to better match the actual signal and dampen the ringing somewhat. This is how I think it would also damp ringing of ports a bit. It isn’t perfect obviously but their measurements do show that it makes significant improvement. I’m still trying to piece together other parts of what is going on that allow it to work with vented and horn systems.

 

As far as the TSP modeling aspect. I will probably not use this aspect much. It is interesting but not what drew me to the technology. Sure you can modify the driver behavior but like anything else it is still subject to the physical limitations imposed by the amplifier and the driver and cabinet it is working with. Basically you cannot force a $200 18” pro woofer to perform like an IPAL driver. You would come at it from the other direction with a really strong driver and dumb the parameters down a bit to make it have response like a more traditional woofer design and cabinet. You can make the IPAL drivers respond like an Eminence Omega pro in a 7ft vented cab, but you would not want to do the reverse. Basically you wouldn’t want to force a driver to act like it has a more powerful motor, or lower qts than it naturally does.

 

Compression ratio I am still going back and forth on...Yes it is even more aggressive than the Othorn however the driver could potentially have 3dB greater excursion limited output and higher power handling. All of which pushes things even further. Folded up cones or massive compression could be a real issue. However increasing the throat volume loses a lot of sensitivity and makes the response much rougher. 6 of one half dozen of the other. I've been doing a lot of second guessing. I will have to make a move and go for it in the next couple weeks if I want the cabs done in time for spring.

 

BTW if you can guess what is going on in the cab I will give you a cookie. :P 

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I don't know.  you are pretty creative so there are many things your latest could be designed for on the inside.

 

at high pressure, symmetry of output around the driver itself for balanced loading would seem to be among the next evolutions to minimize stress on the moving assembly and the cone itself.  so perhaps some sort of cone shaped "plug" in front of the driver with exits on opposite sides of the 'loading chamber' that then combine into the throat of the horn?  or maybe just a hole though which the air would be forced into the throat of the horn.  that might actually be the simplest solution that provides balanced loading around the driver. 

 

seems like one of those powersoft magnetic linear accelerators attached at the throat of the horn could be something wicked.  do they have a t&e unit that they could send you?  that should be worth a cookie.  ;-)

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Only curious as I have played with the 21 IPAL in many simulations but Ricci what do you think this driver can take as far as compression?e

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Only curious as I have played with the 21 IPAL in many simulations but Ricci what do you think this driver can take as far as compression?e

 

I'm not sure. The cone does have a reinforcing ring about 1.5" wide around the cone edge which the 21sw152 did not have. That should help strengthen the cone edge where flex would be worst. We will see. If it survives the PH cab testing with a BIG amp strapped to it I suspect the cone is good for pretty much any loading. We will see though. It might grenade at high power too.

 

John,

You give me too much credit. I like to keep things simple where I can. I could not fit a true throat chamber into the design because it complicates the fold and takes up extra space. I may try the cone correction plate but last time I did that is when I did crack a cone so I'm a bit leery of that. The improvements where there but they weren't game changing. Ultimately I left them out of the Othorn for that reason.

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I had a few simulations of the Othorn and changing a few things got the response with the IPAL  smoother with a touch more extension than in the original Othorn, That said its a very high compression ratio of about 5. Looks great in the simulation but was curious what your thoughts were. That being said I will wait to hear your drivers results after testing.

 

I also thought you had discs to aid ib even compression but just had one to many and the cone made contact with that? Not sure

 

Either way I hope to throw some sun your way to see you get this tested in the next month or so.

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Wow! how exciting. I've been eyeing that IPAL driver for awhile, its cool to see a diy design that will use it, especially a TH!! My pair of Othorns is still going strong as ever.down here :-) . The palehorn seems like a nice option for people who want to go a bit lower/louder than the othorn, but don't need the super low extension of the gjallarhorn or couldn't deal with the size/weight of it. My guess is there is one fold on the driver side, then 2-3 more on the other,....I wonder where the entry to the mouth is? Keep up the good work josh, thanks for everything!!

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Close guess. I sort of mentioned what was going on in this cab already. May as well post the fold pics.

 

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Yep. Dual hatches are a must in order to easily get at all of the bolts for the driver. It just fits through the hatches with a bit to spare. I usually like to leave room for potentially bigger drivers in the future but on this one rated xmax isn't even reached unless you have a LOT of amplifier. The Othorn would already handle a big amp and this takes quite a bit more to push the driver to xmax so this one will likely be thermal buildup limited more than anything. I don't see any drivers handling more than this one thermally and extra xmax beyond what the ipal driver has simply won't be used because you won't be able to get enough amp on it.

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K20? :D

 

Is it the suspension and motor that make this thing so hard to power to hit Xmax or is it mainly impedance in this new horn?

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Its just the fact its a 21" driver with 20mm xmax in a horn tuned near 25Hz. Takes a lot of juice to get the cone to move that far at the excursion max near 38Hz.

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Yes it is a similar fold style to the GH2. Actually the PH fold was done first and gave me the idea to try it on the GH. I'm hoping to start on my cabs soon. So far the PH's are vaporware. That will be remedied this summer.

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