Ricci

Got the Ipals pulled from the enclosure they were in and the DS115's unboxed last night. I just need to put a bit of lining in the cabs behind the drivers, drill my hole for running wiring to the second driver, and load them up. I plan to be getting some impedance measurements and close mics by this weekend.

Access hatches are huge. Plenty of room.

Weather looks beautiful next week too, measurements!!!

Haha!

 I have a couple of days worth of crap to do to them in the garage first! Need to break in the 21DS115's more. Load the Ipals, wiring, impedance measurements, pull parameters from the DS115's, maybe mess with some close mic measurements while I'm at it. Might see what a bit of 2.5" thick mattress foam around the driver does. Also mess with the vent tunings and figure out what the HPF's need to be for the wide open testing, Etc...Don't worry I'll get there.

Yep. Got a call this morning. Not bad at all. I'm glad they are here before this weekend.

Kyle makes a good point. We often simulate airspeeds under a worst case scenario with a full power sine wave at the airspeed maximum, but that's very rare. most of the time we aren't running the speaker wide open for all it's got and the content is almost always much more transient, wide bandwidth and complex. In a way it's sort of similar to the reason that I now prefer very low qts drivers for their higher efficiency. With complex, wide bandwidth material the power requirements are lower and it leaves more effective headroom in the amplifier on those types of signals. Also less thermal demands on the voice coils.

Looks like my cabs are getting delivered tomorrow.

Calculating this kind of thing is a job for a FEA program.  

 

One thing I noticed in the comments above by SME.  You are applying fluid flow calculations to air flow calculations.  There are some similarities between the two mediums.  Where the differences begin is that a fluid is pretty much non-compressible.  Whereas a gas is.  And that is where we run into problems when we want to do some useful calculations in the junctions of the interior of a container with a port and the the end of the port.  Much has to be taken into account in order to make any useful calculations.  And that makes the calculations a real pain in the but.

 

From lurking around on some of the threads I see that some of you guys are pretty handy with Hornresp.  A few years back I asked David McBean to include particle velocity measurements in Hornresp to use in some very high SPL type of cabinets.  It is not a full around every corner, nook and so on calculation.  But it does get you somewhere in a hurry.

 

The keeping it below 10 meters/second rule of thumb goes a long way into making a serviceable port.  

Hey Mark,

 Welcome.

I'd agree with your last sentence but the caveat is that it is basically impossible with any type of serviceable design using modern high power drivers. By the time the vents are made that large, the overall size is completely out of control, or the pipe resonances are bad, or you are faced with a large system with little useable output compared with the size of the device, or a combination of all of the above.

In other news it looks like my cabs are about to ship from dsl1's shop. Now I just need the weather to hurry up and warm up.

deeper is always better obviously it sounds like I'm being deliberately obtuse but I'm not, honest!

 

Basically my approach here is model some stuff, see what can be achieved, compare to what can physically fit in my room, compare to what I have already and see whether that is something that makes sense as part of the system, repeat until I find one or more interesting things to build. This means that, atm, I'm asking "what can be built using this approach with 10-12" drivers?" rather than "I want something that can do 110dB at 25Hz" (or whatever).

I didn't forget about this I just haven't had a lot of time to look at the options yet. There are some 10 and 12" drivers that look workable in this type of cab but I haven't gotten to the point of getting into details or comparing against other cab types the same size.

Hey Ricci

 

 

Huge fan of your work and wondered if you could drop me an email  as we are from bonny  Scotland and would love to build 8 of these. 

 

http://www.facebook.com/electrikalsoundsystem

 

Hey Richard...Welcome to the forum. I've sent you my email in a PM so we can discuss. I also edited your email out of your post. You don't want that floating around THAT publicly.   

That's quite the setup you've got there. Looks fun. 16 18" scoops, kick bins and 3 way horn loaded mains? What is going on in the kick bins? Double 15's? I kind of like the blue offset against the wood finish by the way.

Almost.....it was horrible...just redbox it and see for yourself if you are that curious.  But most horrible movies know they are bad and play off of it (Flash Gordon and Black Dynamite come to mind), but this tries to still be serious in spite.

 

JSS

Exactly the kind of movies I meant. absolutely wretched but they kind of play off of it so it's more like an absurd comedy. I'm into that. Just plain bad on the other hand no thanks.

On a semi related note, has anyone seen the Great Wall previews with Matt Damon? Almost seems like a missing spoof trailer from the beginning of Tropic Thunder or he lost a bet with some friends and has to do a terrible movie as a dare. IDK maybe it'll be great but the previews left me scratching my head like WTF is that?

Bandwidth is really important. How low do you need it to go?

Wow.  Jack Reacher 2 was even worse than I could have ever expected.  Didn't even get to appreciate any sound/bass due to the constant cringing at the writing/acting.  Sometimes when a film gets deadpan reviews, my expectations are so low that even a mediocre movie can seem OK.  Not the case here.

 

JSS

Wow. That bad huh? Are we talking bad enough that it is viewable as a comedy? I enjoy watching extremely bad horror/sci-fi movies.

Depends on what your goals are as far as output size and bandwidth? Budget also.

I really have to know what those drivers are made of, cause I can get them at a hell of a good price but there has to be somewhere it doesn't perform as well as the 152. I can't wait to see what this sub is capable of also.

I don't know yet but we will by this summer. I'm going to guess that the DS driver has slightly worse distortion and a bit more thermal compression. I'm also going to guess that it has just a bit more useful displacement. Once those start showing up at all the major B&C vendors I wouldn't be surprised to see street prices below $500. Perhaps well below.

I've got a pair of B&C 21DS115 drivers on hand for general testing purposes so I'll try them out in this cab in comparison to the 21ipal's. On paper they look really good.

How Tarzan as a movie?

Inductance may be a factor on the 16 drivers even with shorting rings in the motor. An 8" coil is a large amount of wire even if it is only a 2 layer or a shallow wind height. The Tymphany driver Kyle linked is the platform they are based on that seems clear, but I'm sure SVS 's version are modified for their specific apps. They do say one is an overhung and the other is underhung for example. It's probable that SVS developed that driver with them as the build house and now Tymphany is offering their own version.  A few things pop out off of the Tymphany spec sheet though. The frame OD is 15" even on the spec sheet so I wonder why list it as a 16"? Also the former ID is listed at 7.4" so it seems like a 7.5" coil not 8". Still huge for sure. MMS is listed at 538g on the T driver which is heavy but honestly lighter than I would've imagined with such a large diameter former and coil. Motor efficiency is about 160. 1w/1m sens is rated at 83dB. That's pretty low. The gap height is very large at 36mm and xmax is only listed at 10.5mm. I'd assume that's a very basic coil overhang figure with no adder. That would be very conservative with such a large gap height and 57mm overhung coil wind. Using a calculation that adds 1/3rd gap height to the overhang would put Xmax 22.5mm and assuming I'm correct the coil wouldn't leave the gap completely until 46.5mm one way. I'd expect that driver to exhibit a very broad BL curve with shallow reduction in force as the coil moves away from centered in the gap so it should certainly be capable of a ton of excursion with distortion increasing relatively slowly as excursion increases. Again SVS's units could be substantially different so I'm just speculating most of this off of the T driver data sheet.

Found a cutaway...Looks like they are using a bucking mag up top to get a bit more flux through the gap. Also 2 big aluminum sleeves.

Tarzan looks typical to me of current action movies from a major studio.

It sure does seem like the current trend is towards most of the bass being centered at 25-40Hz with 15-20dB of roll off down below 15Hz.

They tend to use drivers with lowish sensitivity so they have a flatter more extended natural response. The tradeoff is the upper bass headroom is lower than with a more efficient driver.

As it turns out Ricci, the fact that the joint point of the driver is too small and the long term pressures and acceleration are to high for the diaphragm materials, they keep braking in use because the producers are not developing their own specific membrane to suit their application.

I have this information from a sure source now so this is not only a speculation anymore.

Hmmmm. Thanks for sharing that. It's not surprising really. The attachment point is different from what you would see on a normal driver and is a relatively small area. The acceleration forces these can produce is very high. The cones are very large diameter with a ton of mass and to top it off they are being placed into high pressure, horn, BP, slot type loadings.

Well...2017 season is shaping up to be interesting already. This is just a few of the things that will be on the agenda this year.

Alpine Type R 15" sealed. Had this driver ready to go all last year and just didn't get to it.

Skhorn cab with dual 21-Ipal. Nuff said.

RF T3S2-19 vented in the 21" variable tune cab. Have to make a baffle to downsize the cut-out.

B&C 21DS115 testing.

Jeff from JTR Speakers will be having a few things tested.

I'm trying to get some more pro oriented bass cabinets submitted. I have some leads but we'll see. Fingers crossed.

Might try to revisit the M.A.U.L. cab after a year of break in on the drivers and use the SP-12000 amp. The first test was the first time the drivers had seen power. They went straight from the boxes into the cab and out into the field. Would be interesting to see how the suspension softening on the drivers affects the system behavior.

There's more...

I tend to agree with much of the above. I tried a ruler flat on axis response outdoors and at the LP in smaller rooms a few times and neither sounds good to me. The top end is subjectively too much for my tastes. Sounds unnatural and the low end sounds anemic. This was especially true for the LF outdoors. I assume it is from the lack of direct vibrational queues, or other types of coupling with the body directly, that are much more prevalent in a vehicle or small room, that might help fill in the LF experience. Overall I prefer a bit of a downward tilt from the bass to the treble range, with the bass becoming a bit more aggressively boosted below 100hz. Most of my friends who are not very technically savvy when it comes to acoustics or speakers seem to agree with that type of general shape as well. Maybe it's technically a coloration preference but whatever. At the end of the day it is all about enjoying your music or movies isn't it?

I definitely like the IPAL drivers specs better than the 18 Sound drivers. If I could buy a M drive module I would try it but I will have to stick with the lesser expensive SP plate amps. AND for my build I will make two hatch covers. One with the plate amp and one without. Most likely I would never use the hatches without the plate amp  but if I feel like pushing the limits with the higher tune I can use a bigger amp with just speakons on the other hatch.

 

If moving these cabinets around a lot does anyone use corner protectors?

 

I know Duratex is great but was curious for those that move large cabinets around a LOT. Just want to be able to beat on the exterior for a while. My cabinet probably wont move very much if any at all but I like to plan for roadies handling or UPS handling. lol

 

Thanks

The 18 sound drivers look good but their gap geometry appears to be nearly the same as the 9600 or 9000 series. The B&C stuff has a taller top plate (18mm on the 21) and a longer coil wind from what I can tell. The result is quite a bit more xmax. The 21Ipal coil has a 15mm overhang and doesn't leave the gap completely until 33mm. The 18 sound ID drivers are likely closer to a 10mm overhang and leaving the gap at 22mm.

You can install corner protectors, skid plates, wheels, pole mount, etc. Whatever you want to do.

And also if you have the will and money , a M-Drive module used for this sub if one is using the Ipal drivers

M-drive module is HUGE...If I recall the plate and control panel is around 26" tall. It wouldn't fit.

Correct. I must've been thinking of the 4kw instead of the 6kw. Too many numbers in my head.

For most amps they will start getting into voltage limitations rather than current limitations somewhere around or above 8 ohms with long term signals. As you say it's a moving target depending on the varying impedance vs frequency and a lot of other factors. Content is rarely a pure sine wave for one and it depends on the duration as well. Also the drivers will start to become non linear at high excursions even if technically still within xmax and that will result in a bit more voltage or power being needed than a sim suggests. Although prior testing shows that most systems behave in a more linear fashion at the impedance maximums/high efficiency zones.

The data on the SP site shows long term and medium term output but no very short term burst type output? I wonder how close the amps can get to the voltage limits into the low impedances with a short term burst? It's possible that the 6k could technically have a rating of something like 7500w into 2 ohm if tested at the optimum frequency with a short burp like other amp mfg's do these days. Might further explain why those amps seem to over perform compared to others carrying the same power specs, beyond just having longer term sustained power. If the SP 6K is actually 6K sustained for 3 or 4 secs into 2ohms with a signal below 100Hz and is capable of bursting say 7500w that's way different than something like an Inuke 6K that is spec'd at 6Kw bursted at 1khz and might only be 2kw sustained in the bass range.

Long story short Chrapladm I think the 4k SP amp is a great match for one of these with dual 21sw152's