The ultimate enclosure for the box 18-500 8a
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=93837
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Topic: The ultimate enclosure for the box 18-500 8a
Posted By: app
Subject: The ultimate enclosure for the box 18-500 8a
Date Posted: 09 November 2015 at 8:07pm
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Greetings! There are several plans for the box 18-500 8a driver http://images.static-thomann.de/pics/atg/atgdata/document/manual/193265_bda_185008a_uk_screen.pdf" rel="nofollow - https://images.static-thomann.de/pics/atg/atgdata/document/manual/193265_bda_185008a_uk_screen.pdf Some plans can be found here http://www.lautsprecherforum.eu/viewtopic.php?t=4561" rel="nofollow - http://www.lautsprecherforum.eu/viewtopic.php?t=4561 At the moment I have 2 of these http://www.jobst-audio.de/archiv/97-jb-sub118" rel="nofollow - http://www.jobst-audio.de/archiv/97-jb-sub118 Since Im quite broke at the moment but I might be interested to maybe build something it would be cool to get "the ultimate" design for the drivers I have. I like the sound of the reflex and the fact that I dont need a separate kick bin with them. Would this cheap driver work well in bandpass or PPSL or a scoop maybe? Would be interesting to get some thoughts and ideas since I already have the drivers... Thanks! ------------- "what!?" |
Replies:
Posted By: bass*en*mass
Date Posted: 09 November 2015 at 9:52pm
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they do work in supers, to a certain extent obviously but not bad considering the price.. get in touch with miles on here to get more detailed info ;) |
Posted By: pfly
Date Posted: 09 November 2015 at 10:08pm
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PPSL is pretty much "just" a reflex box so they should work just as well as in normal reflex. |
Posted By: _djk_
Date Posted: 10 November 2015 at 1:33am
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"PPSL is pretty much "just" a reflex box so they should work just as well as in normal reflex." Basically true, except for the distortion reduction action, and the plenum adds a tiny bit of boost (around 3dB or so) from 100hz or so up into the 'kick' region (160hz~180hz with 15's). ------------- djk |
Posted By: app
Date Posted: 10 November 2015 at 1:54am
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Any good links on how to sim a ppsl enclosure in winisd? The ppsl seems interesting at the moment. I need to read some more about ppsl... ------------- "what!?" |
Posted By: pfly
Date Posted: 10 November 2015 at 2:23am
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You model it just like double 18" reflex box. If you want to estimate the effect of slot in upper bass range, you need to model it in Hornresp. Personally I wouldn't worry too much about it, tho this would be nice little project to learn Hornresp on if you haven't touched it yet... _djk_ have you ever experiented with any other loadings with push & pull pair of drivers? edit: of course while simulating normally you'd substract displacement of drivers from the enclosure. With push & pull pair the reversed driver will pretty much compensate normally mounted driver, so one thing less to think about. 18" driver with cone, magnet and basket will displace 10-11 litres. |
Posted By: _djk_
Date Posted: 10 November 2015 at 9:15am
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"_djk_ have you ever experiented with any other loadings with push & pull pair of drivers?" I've done some 4th order designs, but 6th order is the best. A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB). A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB). A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB). http://s56.photobucket.com/user/dkleitsch/media/2_zpsqlogiixd.png.html" rel="nofollow">  A 40hz 2' cube 4th order dual 12 PPSL, one 4x8 sheet, 100dB. Ports above and below the woofer plenum. The drivers are about half the price of an 18 with similar output. ------------- djk |
Posted By: bob4
Date Posted: 10 November 2015 at 12:16pm
I've been doing that as well recently  I've done some simulating with different drivers of all kinds of sizes and price points...... |
app wrote:Posted By: app
Date Posted: 10 November 2015 at 12:55pm
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So is the biggest benefits of ppsl getting low and high and have little distortion? Am I right that ppsl arent that efficient,or is it totally depending on the enclosure type? ------------- "what!?" |
Posted By: app
Date Posted: 10 November 2015 at 1:10pm
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Ive also been checking this http://hornplans.free.fr/mtl-46.pdf" rel="nofollow - http://hornplans.free.fr/mtl-46.pdf Its quite efficient but dont go that low in singles/pair. ------------- "what!?" |
Posted By: app
Date Posted: 10 November 2015 at 1:15pm
I wouldnt mind if you simmed a ppsl for the box 18-500 8a  ------------- "what!?" |
Posted By: bob4
Date Posted: 10 November 2015 at 2:05pm
I actually have already  I'm quite busy now and don't have the time to discuss details, but I would like to do so soon. My simulations suggest you should be able to cram two 18-500s in a PPSL box only slightly larger than your current JB118, and get a similar response. Of course you will get + 6dB since it will take twice the power, and hopefully have the little kick boost from the slot loading in the plenum. It will of course need a little EQ, but you could get the -3dB point at 34 Hz, and 125 SPL within xmax with 400 W input. I'd be interested to get into hornresp too......  |
Posted By: bass*en*mass
Date Posted: 10 November 2015 at 2:22pm
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app what exactly are you looking for? more spl or more sub? reduced distortion and reggea dont mix up in my books.. :) |
Posted By: app
Date Posted: 10 November 2015 at 2:48pm
Im not quite sure yet  "the ultimate enclosure" something which has it all with the driver mentioned. The reflex I use now sounds smooth and goes low but is not as loud as could be. Horn would be louder but wouldnt go as low. PPSL and bandpass boxes are something I dont know much about (yet). But Id like to have it all, efficient,loud and low and something which could be used without separate kickbins. Or a really good compromise Well see what our brains will possibly come up with ------------- "what!?" |
Posted By: app
Date Posted: 10 November 2015 at 3:00pm
Ive just seen a youtube video about this enclosure loaded with the box 18-500. The recommended driver is different. What I "like" about this design is the fact that I could build it since the design is quite simple. Its size is also good. If it only would go to about 40hz in singles...Looks like it would work without a kickbin too. ------------- "what!?" |
Posted By: bob4
Date Posted: 10 November 2015 at 3:08pm
for louder, you will need a beefier driver I'm afraid - or simply more of the same units. So in a way, PPSL helps a little bit, but you have double the cost for drivers. Once you consider the amount of cabinets you need with a "wimpier" transducer to get even SPL wise with a single box loaded with a more powerful driver, the price difference might shrink... if you factor in the cost of wood, probably even more. And you'd have less boxes to carry for same output.... Anyway, would be an interesting exercise to compare two single 18" vs 18" PPSL output and sizewise.
I have a hunch it might do that
 that's definitely a caveat |
Posted By: app
Date Posted: 10 November 2015 at 4:07pm
Thats true! Wouldnt mind having two ppsl boxes which take about the same space as two single 18" BR. ------------- "what!?" |
Posted By: app
Date Posted: 10 November 2015 at 5:39pm
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I simmed a 6th order bandpass. Can take about 800W before going out of xmax. 129db at 1000w,xmax just a little bit over. 99db@1W Rear chamber is 170l tuned to 38hz and front chamber is 76l tuned to 85hz. Port air velocity under 18m/s with 1000w and group delay peaking at 27ms @ 25hz... Ideas how to get the bottom to go to about 40hz and maybe a bit higher too in the other end? This is the first 6th order bp Ive simmed ever. Does it look shitty? Thanks!  ------------- "what!?" |
Posted By: app
Date Posted: 10 November 2015 at 5:50pm
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Infact compared to the jbsub118 theres only 2db difference in theoretical spl and the jbsub118 goes deeper AND higher ------------- "what!?" |
Posted By: app
Date Posted: 12 November 2015 at 11:41pm
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Please link 18" ppsl plans here if you have them. Would like to see some plans to get a better understanding of the ppsl designs. At the moment Im really interested in building a 18" ppsl enclosure for the box 18-500 8a drivers. I wonder when people who have heard a ppsl sub say that the bass is different,different in what way? Less distortion yes but does it still shake the room and feel heavy or does it feel like something is lacking in the bass? Some say its the best sounding sub... ------------- "what!?" |
Posted By: app
Date Posted: 13 November 2015 at 12:23am
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I start to believe that these plans here are about as good as it gets for this driver... http://www.lautsprecherforum.eu/viewtopic.php?t=4561" rel="nofollow - http://www.lautsprecherforum.eu/viewtopic.php?t=4561 ------------- "what!?" |
Posted By: _djk_
Date Posted: 13 November 2015 at 7:21am
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The Qts is high enough on those woofers that the box will be a bit large. I generally try and use drivers with a Qts around 0.312, this gives the smallest box, most efficient, and deepest bass. ------------- djk |
Posted By: app
Date Posted: 13 November 2015 at 1:48pm
Yeah I read that you suggest building the enclosure 4 x the Vas of the drivers...That would make the enclosure really big. ------------- "what!?" |
Posted By: _djk_
Date Posted: 13 November 2015 at 10:02pm
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"Yeah I read that you suggest building the http://www.macmall.com/p/7024452?dpno=8997870&source=zwb12166" rel="nofollow - That's not correct. For a Qts=0.312 it is Qts^2 * Vas * 4.1 If the Qts is .3 vs .4 the cabinet will end up being about twice the size for the driver with the weaker motor (higher Qts). ------------- djk |
Posted By: app
Date Posted: 14 November 2015 at 2:35am
So if the qts of the box 18-500 8a is 0.425 and Vas 208l the calculation looks like this: 0.425^2 x 208 x 4.1 = 154 approx So the enclosure size should be twice that 308l ? ------------- "what!?" |
Posted By: _djk_
Date Posted: 14 November 2015 at 6:26am
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The constant for a Qts=0.425 is more like 6 (rather than 4.1), so .425^2 * 208 * 6 = 225L (per driver). I would need to get out the LDC to check the exact value for the constant for that Qts, but I think 6 will be close. It may be possible to do a C6 alignment (like my B6 PPSL designs), with a small amount of ripple in the response. I will have to check that on a different computer at home (posting from work at the moment). ------------- djk |
Posted By: _djk_
Date Posted: 16 November 2015 at 7:04am
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I ran some designs on this driver. BB v6.0 suggested about 14.5 cu ft for a pair, and could be made to be 3dB down around 42.5hz. An alternate design would be a C6 of 8 cu ft net tuned to 40hz with a Q=2 filter at 40hz. This would be 3dB down at 40hz. Two ports of about 50 sq in each by 12.5" long will be enough. A pair of these drivers will handle about 2KW before getting into excursion problems with this design. ------------- djk |
Posted By: mini-mad
Date Posted: 16 November 2015 at 7:23am
i wouldnt mond seeing the plan for that DJK.... iv always wanted a double 18" reflex and it sounds like you may have come up with a nice "little" box there. If you wouldnt mind sharing of course. ------------- If it sounds like a gorilla is trying to escape, turn it down. |
Posted By: app
Date Posted: 16 November 2015 at 8:34am
Id like to see the plans too if possible! PM me if you want!  ------------- "what!?" |
Posted By: cravings
Date Posted: 16 November 2015 at 10:34am
| he's given you the info to start working on a plan.. |
Posted By: bob4
Date Posted: 16 November 2015 at 3:43pm
thank you for your hints, and pardon my ignorance: what is C6 ?(I gather it's a specific alignment?) Can you point me to a good source of information? best regards, Bob |
Posted By: _djk_
Date Posted: 16 November 2015 at 11:00pm
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" Can you point me to a good source of information?" The LDC by Dickason Loudspeaker Design Cookbook 7th Edition Book ------------- djk |
Posted By: AndyWave
Date Posted: 17 November 2015 at 6:14pm
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thank you for your hints, and pardon my ignorance: what is C6 ?(I gather it's a specific alignment?) Can you point me to a good source of information? best regards, Bob quote end Hi Bob It is electrically corrected reflex alignment. So generally in smaller enclosure one can have same low freq output with aid of eq (and low cut filtering to keep Xmax in control below box tuning). one way of executing this By Mr Don Keele http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20%281975-07%20AES%20Published%29%20-%20New%20Set%20of%20VB%20Alignments.pdf ------------- torturing electrons since ...... |
_djk_ wrote:Posted By: bob4
Date Posted: 17 November 2015 at 10:04pm
much obliged! |
Posted By: app
Date Posted: 17 November 2015 at 10:37pm
Thanks for the link! ------------- "what!?" |
Posted By: _djk_
Date Posted: 18 November 2015 at 2:38am
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Don worked for EV, Klipsch, and JBL, he knows his stuff. A PPSL cabinet for these would be about 24"H x 36"W x 30"D, with a plenum opening of about 9"W, and a shelf port on each side of the box about 2.375W X 12.5"D (I will see if I can make the ports bigger, this is the minimum suggested size). ------------- djk |