Horizontally opposed JBLs + 1 rear facing PR/SLAPS - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 28 Old 02-14-2020, 10:04 AM - Thread Starter
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Horizontally opposed JBLs + 1 rear facing PR/SLAPS

The enclosure is a 20” cube or about 3 cu.ft. net. 2 JBLs are going on the L & R sides of the cube and the sub will be placed at a 45 angle wrt the corner to “load” the JBLs equally. I’m leaning towards the PR/SLAPS firing into the corner for somewhat similar loading between the active and passive drivers, all facing the wall/boundary/ies. However the SLAPS facing into the room would look cool too with those massive surrounds. Plus I think I would get better performance SPL/FR with the SLAPS facing the corner. Pros/cons of doing this? Comments please.

It’s sort of a stealth sub from furniture, not sure how 3 of these stacked in a corner will still be stealth 😊, it has a nicer real wood framed front so I have to decide where I’m going to cut a hole for the PR/SLAPS and just can’t turn it 180 later on because if I cut the hole on the nice side and it turns out the FR is better with the PR facing the corner then I’d have the uglier looking back side for the furniture facing into the room. I have 5 of these, so 3 will be stacked in the front corner and 2 will be along the side walls as stands for the side surrounds directly to the sides of the MLP. The matching dresser 72x20x20 with 6 JBLs + 3 SLAPS will be a VNF right behind the MLP.

Has anyone played around firing a port/PR or even the active driver into a corner and taken measurements? I know there’s been a lot of discussion about this through the years but I didn’t really see any comparisons with graphs (pls. point me to them if I missed em).

Thanks!
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post #2 of 28 Old 02-14-2020, 10:44 AM
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I have been pondering building a quad-JBL w/ 2 opposed SLAPSM-12s for a balanced cabinet. One thing that has been ignored in most of the posts here: the low mass of the PR. Last year ryanmh1 posted his build on data-bass and (I THOUGHT!) on this board... except I can find no evidence of it! Anyway, over on data-bass he talked of how much mass is needed to drop the tune down to 16-18hz. That is part of what I want to play with if I build one out of the JBLs. Modeling PRs seems to be as much "art" as science, however. If interested, have a look at his thread over here: http://data-bass.ipbhost.com/topic/7...in-a-tiny-box/
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post #3 of 28 Old 02-14-2020, 10:49 AM - Thread Starter
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Quote:
Originally Posted by MTBDOC View Post
I have been pondering building a quad-JBL w/ 2 opposed SLAPSM-12s for a balanced cabinet. One thing that has been ignored in most of the posts here: the low mass of the PR. Last year ryanmh1 posted his build on data-bass and (I THOUGHT!) on this board... except I can find no evidence of it! Anyway, over on data-bass he talked of how much mass is needed to drop the tune down to 16-18hz. That is part of what I want to play with if I build one out of the JBLs. Modeling PRs seems to be as much "art" as science, however. If interested, have a look at his thread over here: http://data-bass.ipbhost.com/topic/7...in-a-tiny-box/

His post was on @Nalleh 's Franken thread. Yup read that post, but there's not a lot of info on these SLAPS out there. The box is 3 cu.ft. and when I used their calculator it didn't take much additional mass to tune down to 18hz. I'll get back to you about the details.
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post #4 of 28 Old 02-14-2020, 10:55 AM - Thread Starter
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With a 3 cu.ft. box
Looks like only 40 grams more at 18 Hz on top of the 400g (383.67 to be exact).
@17Hz, it needs 100g
@16 = 173
@15 = 264 but still under the 1000g max total
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post #5 of 28 Old 02-14-2020, 11:06 AM
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Originally Posted by Arv View Post
Looks like only 40 grams more at 18 Hz on top of the 400g (383.67 to be exact).
@17Hz, it needs 100g
@16 = 173
@15 = 264 but still under the 1000g max total

Where did you get the calculator? These numbers are very different from what you will find in the data-bass thread I linked. Ryan noted that the numbers listed from Earthquake are completely wrong, and that he actually talked with them to try to get to the real specs. Obviously that is a different implementation ... anyway, let me know about the calculator.
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post #6 of 28 Old 02-14-2020, 11:06 AM - Thread Starter
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Originally Posted by MTBDOC View Post
I have been pondering building a quad-JBL w/ 2 opposed SLAPSM-12s for a balanced cabinet.

In a 3cu.ft box tuned at 18Hz, dual SLAPS will require 470g each, still below the 1000g limit but pushing it. At this mass you'll have some loss.
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post #7 of 28 Old 02-14-2020, 11:14 AM
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Again, please let me know where you came across that SLAPS calculator
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post #8 of 28 Old 02-14-2020, 11:16 AM - Thread Starter
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Where did you get the calculator? These numbers are very different from what you will find in the data-bass thread I linked. Ryan noted that the numbers listed from Earthquake are completely wrong, and that he actually talked with them to try to get to the real specs. Obviously that is a different implementation ... anyway, let me know about the calculator.

I actually talked to the guy who designed the SLAPS, what a character! We went really off track and ended up talking about the pioneers in sub DIY inc. Vance Dickenson (I still have his book from the 90's as reference, LOL). I actually got the calculator from them, PM me with your email and I will forward you the .xls files, I'm sure they won't mind. I didn't bother to check the parameters and I did recall ryan mentioning that they were wrong but I really didn't pay attention to this calculator since I'm winging my design for this one. I figured with the size of the box I will definitely get a Fb of 20Hz or lower. I'm definitely going to put t-nuts on the SLAPS since I intend to tune it. I have 7 at home so I can use the washers from the others and might just drive down to Grainger and get some of those washers that ryan mentioned if needed.
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post #9 of 28 Old 02-14-2020, 11:23 AM - Thread Starter
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I know Micheal @LastButNotLeast got sub 20Hz tuning without adding any weight with a box around 3cu.ft.
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post #10 of 28 Old 02-14-2020, 11:28 AM
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Originally Posted by Arv View Post
I actually talked to the guy who designed the SLAPS, what a character! We went really off track and ended up talking about the pioneers in sub DIY inc. Vance Dickenson (I still have his book from the 90's as reference, LOL). I actually got the calculator from them, PM me with your email and I will forward you the .xls files, I'm sure they won't mind. I didn't bother to check the parameters and I did recall ryan mentioning that they were wrong but I really didn't pay attention to this calculator since I'm winging my design for this one. I figured with the size of the box I will definitely get a Fb of 20Hz or lower. I'm definitely going to put t-nuts on the SLAPS since I intend to tune it. I have 7 at home so I can use the washers from the others and might just drive down to Grainger and get some of those washers that ryan mentioned if needed.

AWESOME, thanks! I will send email. As I have said elsewhere, I have some JBLs to play with, but ALSO 2 old HE-15s. This was from a group buy over 15 yrs ago, and the design called for a 22" cube with PRs. It really didn't sound so good, and there was a rather heated debate about that sub. After building one, ThomasW then built a ported sub that sounded much better. I think that the issue was the PRs, and until these SLAPS came along, I don't know that there have been any truly LONG throw PRs. So I am pondering trying another HE-15 sub using two SLAPS, something like what Ryan built last year.


Of course now the QuadJBL devastator is building momentum, and so I am thinking of trying one of those. I don't have issues of space, just cost & complexity. These JBL drivers are obviously the budget champ, and I think a PROPER PR implementation might really work well, hence my interest in tuning.
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post #11 of 28 Old 02-14-2020, 11:29 AM
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I know Micheal @LastButNotLeast got sub 20Hz tuning without adding any weight with a box around 3cu.ft.

Was that tuning, or merely in-room response?
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post #12 of 28 Old 02-14-2020, 11:42 AM - Thread Starter
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^^^ The quad devastator sure is sweet but HUGE. One of my main subs is an old Shiva-X (ripped the Shiva it replaced due to hitting Xmax to often, lol) ported tuned to 15Hz. Its enclosure (20" sonotube) is only slightly shorter than what the triple 20" cubes will take. I'm done with big enclosures, nowadays amps are cheap and JBLs are dirt cheap. As for SLAPS being truly LONG throw, they say to put it at least 10cm from the wall "as the SLAPS can move up to 9cm" I don't think the 4in Xmax is one way but it sure sounds like it.



Send me those HE-15s if they need a home! I'm also using some vintage 15" Cerwin Vegas as MBMs, they are definitely efficient, doesn't take much to drive them and so much output!
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post #13 of 28 Old 02-14-2020, 12:00 PM - Thread Starter
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Originally Posted by MTBDOC View Post
Was that tuning, or merely in-room response?

I believe it was 1M ground plane close mike. And even if it was in room response the "dip" hence the tuning is still sub 20. Nalleh didn't add any weight either and his total volume was smaller AFAIK.


Whatever we build just make sure the SLAPS are vertical so one does have to worry about sag specially when adding mass. For my VNF, the front baffle will have a 13" vertical face for the SLAPS, then on top of it a 33 degree slanted face (matches the max. incline for my recliners) for the JBLs. this baffle shape will allow me to push the VNF as close to the back of my HT recliners. Still don't know if I'm going to do a BOSS on top of a bigger platform on which the VNF would sit on, the VNF +BOSS on the same platform might be too heavy.
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post #14 of 28 Old 02-14-2020, 02:32 PM
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PR's are easy. Essentially the same as a port with a couple bonuses and a couple drawbacks. The bonuses include a smaller enclosure due to no port volume subtracting from the box (just driver displacement), no port resonances. The drawbacks include a steeper rolloff below tuning (sometimes), some more losses vs. a well designed port, and of course cost. For the time & effort many put into builds, I'm not sure why PR's aren't used more often.
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post #15 of 28 Old 02-14-2020, 02:42 PM
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PR's are easy. Essentially the same as a port with a couple bonuses and a couple drawbacks. The bonuses include a smaller enclosure due to no port volume subtracting from the box (just driver displacement), no port resonances. The drawbacks include a steeper rolloff below tuning (sometimes), some more losses vs. a well designed port, and of course cost. For the time & effort many put into builds, I'm not sure why PR's aren't used more often.

Yes, I know you have said this before. The thing is, after reading Ryan's build thread over on data-bass it is clear that PRs have "variably odd behavior" in some ways. His finding that the PRs dug deeper (hz) when driven harder is quite interesting. The PRs that JohnJ (Stryke, etc) had to go along with the HE-15 drivers weren't good in my opinion. The surround material wasn't up to the task, that is what is so impressive about the SLAPS. I got a package of 100 washers from Grainger (5/16 x 3") which weigh 52 grams each. Adding a longer bolt and 20+ washers, observing it while swinging it around, moving the diaphragm, etc => this surround is REALLY stout! So it can handle lots of weight as Ryan noted, which is what he needed for his sub.



I am curious as to how the HE-15 would perform in different arrangements. The original 'cube' was likely due to PRs not being up to the task. How it would perform in something like the Devastator would be interesting to see modeled. Perhaps I ought to post a different thread ...
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post #16 of 28 Old 02-14-2020, 02:48 PM - Thread Starter
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PR's are easy. Essentially the same as a port with a couple bonuses and a couple drawbacks..., I'm not sure why PR's aren't used more often.
I haven't confirmed this a 100% yet(and I haven't seen this published anywhere) - that a PR doesn't turn into a "hole" in the box like a port below tuning causing the driver to unload. I think people just didn't look/care much about FR below tuning in the past since you're not supposed to be operating below the passband/tuning but now we're so into the teens and single digit performance that THIS is one big advantage of a PR vs a port!

It took me a while to realize this.
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post #17 of 28 Old 02-14-2020, 02:51 PM - Thread Starter
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Now back the the original question 😁, PR in the back or front?
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post #18 of 28 Old 02-14-2020, 03:36 PM
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I haven't confirmed this a 100% yet(and I haven't seen this published anywhere) - that a PR doesn't turn into a "hole" in the box like a port below tuning causing the driver to unload. I think people just didn't look/care much about FR below tuning in the past since you're not supposed to be operating below the passband/tuning but now we're so into the teens and single digit performance that THIS is one big advantage of a PR vs a port!

It took me a while to realize this.
I agree. My first PR design was an Adire Tumult with a couple Stryke 18" PR's & 2500g. They were tuned to about 14hz and had a lot available under, but at the time my measurement capability was limited.

To me, the big pluses are no port resonances (I keep repeating myself but IMO this is a problem with low tuned subs) and the box actually is notably smaller vs. a reasonable sized port. I'll gladly pay the extra bucks for a PR.

As an aside to the asides, I am sniffing into the slaps M15. muhahahhaa.
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post #19 of 28 Old 02-14-2020, 05:50 PM
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PRs are too expensive. If they were the same price as a plastic port tube they would be more common.

Don’t aim the PRs at the wall. They are producing the least directional wavelengths. The driver facing the corner will lift its spl.
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post #20 of 28 Old 02-14-2020, 11:40 PM - Thread Starter
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Don’️t aim the PRs at the wall. They are producing the least directional wavelengths. The driver facing the corner will lift its spl.
Samps,
Just checking that you know that there are 2 actives and a PR. Not the other way around. The drivers are facing the wall, the question is whether to face the PR to corner or to the room.
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post #21 of 28 Old 02-15-2020, 07:57 AM
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Probably won’t be a big difference which way the PR faces. Facing into the corner will likely get a tiny bump in spl.

You could test with one box and if it doesn’t work out then put that one behind the couch out of sight.
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post #22 of 28 Old 02-15-2020, 02:20 PM
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The beaty of a PR, and even more so with the massive SLAPS is its tunability!

So instead of pondering for weeks with a pc program, just build the 3cf box, put in the JBL’s and SLAPS, and start measuring !!

My guess is no matter how much and what you try in the program, it will not be quite correct, so just build it

Do some measurements as is, remove SLAPS, add mass, measure again, rince repeat You can go from zero mass up to about a Kg! So there should be possible to find something that works

It should all be done in a afternoon.

Dual AVR 13.1.8 SWAtmos - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 6xSI18" - 12xJBL 12" w/6xSLAPS M12 downfiring VNF - 3x2 stacked Crowson MA - 4xBK-LFE Dual TR Sleds- 6xNU6K(fan&trig mod) - Minidsp 10x10HD - Oppo UDP203 - XB1X - ATV4K - Vertex2 - JVC RS600 Dreamscreen V2 120"- Philips 65OLED873.
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post #23 of 28 Old 02-15-2020, 04:13 PM - Thread Starter
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So instead of pondering for weeks with a pc program, just build the 3cf box, put in the JBL&#226;€&#x2122;&#xfe0f;s and SLAPS, and start measuring !.

Hahaha! That's what I told @MTBDOC ! I didn't really pay much attention to the calculator specially with the messed up TS parameters.

Luckily my side table cubes are going to be about 3cu.ft!
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post #24 of 28 Old 02-15-2020, 04:26 PM
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Hahaha! That's what I told @MTBDOC ! I didn't really pay much attention to the calculator specially with the messed up TS parameters.

Luckily my side table cubes are going to be about 3cu.ft!

Yeah, that is one huge advantage, that's why I bought 5kg of 3" washers & some 2.5" bolts! I simply want to get an idea of performance before building, to see if it's worth the time & effort. The work Chris has put in for the QuadDev shows that it is certainly worthwhile to build that box. Also, modeling would help with a better idea of box size; where is the point of diminishing returns?


Basically RyanMH1 found that out, simply adding washers on his build until he got a tune he liked. A bit easier than cutting port length! Or stuffing ports, but that does seem popular. For the life of me, I cannot understand why people build some boxes with the intent to stuff a port. Just shrink your ports! Anyway ....
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post #25 of 28 Old 02-15-2020, 04:34 PM - Thread Starter
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Yeah, that is one huge advantage, that's why I bought 5kg of 3" washers & some 2.5" bolts!
BTW what's the part number for those washers and size of the bolt?
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post #26 of 28 Old 02-15-2020, 05:07 PM
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BTW what's the part number for those washers and sizeof the bolt?
Here is a link... and they are on sale under $20. I had them shipped to the local Grainger, couldn't be easier (or cheaper!) -

https://www.grainger.com/product/FAB...-x3-O-D-22UF47


Then I went to Lowes and picked up 2.5" x 5/16 stainless bolts & lock nuts. My plan is to use doubled regular nuts while testing these things, then once I have dialed it in remove the PR to exactly balance the weight on each side, and then install with the lock nut. Obviously the nylock will require a wrench on the backside to remove, so this would be for a permanent but NEVER vibrating loose arrangement!



Thanks for the spreadsheet. I was going WHAAAA until I realized that it had both the M12 and 12, different specs. Still, the numbers look different from what Ryan quoted in his write-up. It was interesting as he said the guy at EQ cut up a SLAPS just to get some better numbers. Very helpful, just like your experience in talking with them.

Back in the dark ages (mid 80s) I built a ported box for 2 8" MTX drivers to stuff in the back under the hatch in my VW Scirocco. I ended up calling MTX and spent 30+ min on the phone with a geek engineer (takes one to know one!) as we discussed options. Back in those days NOBODY knew much of anything about cars. I ended up building a box based on his numbers. The thing is, you couldn't buy ports. I built two of them out of paper mache, just like in elementary school. Worked great! I had a KILLER Denon cassette head unit, great amps, and I think Boston Acoustics car separates which had good Xovers. People thought I was weird going to so much trouble! Then again, I installed a turbo with the car on blocks in the driveway over the winter. Young and unstoppable!
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post #27 of 28 Old 02-15-2020, 06:57 PM - Thread Starter
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Thanks @MTBDOC just purchased the washers will pick up next week!

The shipping wt. shows 13 lbs. Hopefully 6kg. Will be enough for 8 SLAPS.

Good idea on the nylocks, I was just going to use locktite blue. Yeah I was also going to temporarily load up the front then balance frt to back later on. Don't forget the t-nuts for mounting.

Your 80s project just reminded me of the time (also in the 80s,lol) when I butchered my grandfather's hifi system and mounted the 12" woofers on a board and placed it on the deck of my hatchback, of course I didn't really know what I was doing and a decade later i find out that it was technically an IB, leaky IB to be exact ,lol.
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post #28 of 28 Old 02-15-2020, 07:32 PM
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Thanks @MTBDOC just purchased the washers will pick up next week!

The shipping wt. shows 13 lbs. Hopefully 6kg. Will be enough for 8 SLAPS.

Good idea on the nylocks, I was just going to use locktite blue. Yeah I was also going to temporarily load up the front then balance frt to back later on. Don't forget the t-nuts for mounting.

Your 80s project just reminded me of the time (also in the 80s,lol) when I butchered my grandfather's hifi system and mounted the 12" woofers on a board and placed it on the deck of my hatchback, of course I didn't really know what I was doing and a decade later i find out that it was technically an IB, leaky IB to be exact ,lol.

They weigh 52 grams each ... and yes, I put stacks of 10 on my scale more than once. They are quite consistent. So you have 5.2kg of additional weight, plus the slight add'l weight from longer bolts.



I am a fan of nylocks although I loctite LOTS of stuff I do mechanically. They won't come loose, and although I have confidence in loctite, this is a WEIRD application and I figured a few extra cents for the nylocks would be better once it is dialed in.
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