I recently picked up a bunch of those cheap JBL GX1200 drivers for $29 and started doing little projects with them and have scrap. I've wanted to play around with the idea of tactile response and impact with near field subs and also wanted to tinker with open baffle to learn from it and measure it and see what that's all about, satisfying a lot of curiosity for a few coins. I don't know how to model open baffle or free air driver response and behavior, so I just had to build it and see what it did.
Keeping it simple, I started with a wedge that is about 22 degrees with a 30 inch tall back so that both the 12 inch drivers would fire into my chest and guts in my seating in my audio room. I ended up doing 30 inches (back) x 12 inches (base) x 0.63 inches (top) with a 31 inch face at a 22 degree slope. I gave it some braces between the drivers and in the bottom back. I wasn't sure how this would effect things but I know it needed at least some kind of bracing. All glue, no screws.
I rounded the edges and sanded it and then said, well, what the heck, and went ahead and pre-stain, stained (Early American) and then did a top coat of satin poly over this birch veneer ply scrap I have. I'm not going to see it behind a seat, but figured, if I do anything else with it it won't be bare timber.
The drivers are ugly, the red JBL 1000w logo on the dust cap is hideous. I need to find a way to replace those inexpensively. They're $29 drivers so I cannot really complain.
I did some listening first, some music and a few movie scenes. Then I did some measurements, near field on the drivers and at the listening position with room influence. Pretty interesting results.
I wired them in series so they're around 8ohm. I am powering them with a 75 watt RMS at 8ohm Dayton sub plate amp in an outboard box of its own to keep it simple. No DSP. No EQ. At least not for testing at first. It has a built in 18hz high pass filter, and I just let it keep a low pass filter of 120hz or so. Later I tested it on my NX3000 channel to give it more output and was able to max it without ever seeing clipping or signal issues at the amp, so these 250w RMS drivers together can definitely soak up 500 watts no problem. They're both 12mm xmax so together they can move quite a lot.
Overall I like them for their effect for impact and tactile response. I did a crossover in my miniDSP to test them limiting them to 45hz~100hz basically with sharp drop offs so that they're basically mid-bass modules and then maxed the volume on them. It was interesting to have the impact in gunfire scenes in John Wick, Heat, Equilibrium, etc. Lots of thump in my chest from those with this behind the seat. It made me want to re-do this with 4 drivers to get even more.
For just general music listening it surprisingly sounds great. It takes a lot of amp to get them to be loud, but at around 35 watts per driver at 1 meter it was plenty loud for me for music and was capable of digging quite deep. Deeper than I expected. I would need a lot more amp to use them in a larger room and listen at greater distance for sure, but to off set that I would rather use more drivers. That's a future project.
Here's some measurements. The top two are near field. The upper driver is in red. Really nice response from 30hz to 180hz. The drop at 34hz or so is due to the narrow wings at the top of the baffle. The bottom driver in blue. Same response, however, it has much longer wings next to its baffle and so I get the low end response from 30~34hz back. Learned a lot with just that simple bit on the sides with the baffle. For mid bass this didn't matter. For sub-bass it would matter a lot. When measuring these I referenced at 99db.
The green line is at the listening position with the room involved. Surpringly not bad, it kept bass pretty decent to 30hz. A little EQ and this could be flat. I referenced this at 90db. Ultimately this wasn't meant to do anything at 30hz or over 100hz. I just wanted to see what it would look like with the open baffle. This graph doesn't show it, but I later used a crossover in the miniDSP to set it to basically focus on 45hz to 100hz as a mid-bass slammer module.
Fires into our guts and chest behind the seats.
It's really back heavy with those magnets. It actually leans on carpet. I think I will put some small feet in the back to keep it straight to counter the weight.
Learned a bunch about open baffle with this. Will explore more. Also learned a lot about tactile response and impact. Going to focus more on this now.
Very best,
Keeping it simple, I started with a wedge that is about 22 degrees with a 30 inch tall back so that both the 12 inch drivers would fire into my chest and guts in my seating in my audio room. I ended up doing 30 inches (back) x 12 inches (base) x 0.63 inches (top) with a 31 inch face at a 22 degree slope. I gave it some braces between the drivers and in the bottom back. I wasn't sure how this would effect things but I know it needed at least some kind of bracing. All glue, no screws.
I rounded the edges and sanded it and then said, well, what the heck, and went ahead and pre-stain, stained (Early American) and then did a top coat of satin poly over this birch veneer ply scrap I have. I'm not going to see it behind a seat, but figured, if I do anything else with it it won't be bare timber.
The drivers are ugly, the red JBL 1000w logo on the dust cap is hideous. I need to find a way to replace those inexpensively. They're $29 drivers so I cannot really complain.
I did some listening first, some music and a few movie scenes. Then I did some measurements, near field on the drivers and at the listening position with room influence. Pretty interesting results.
I wired them in series so they're around 8ohm. I am powering them with a 75 watt RMS at 8ohm Dayton sub plate amp in an outboard box of its own to keep it simple. No DSP. No EQ. At least not for testing at first. It has a built in 18hz high pass filter, and I just let it keep a low pass filter of 120hz or so. Later I tested it on my NX3000 channel to give it more output and was able to max it without ever seeing clipping or signal issues at the amp, so these 250w RMS drivers together can definitely soak up 500 watts no problem. They're both 12mm xmax so together they can move quite a lot.
Overall I like them for their effect for impact and tactile response. I did a crossover in my miniDSP to test them limiting them to 45hz~100hz basically with sharp drop offs so that they're basically mid-bass modules and then maxed the volume on them. It was interesting to have the impact in gunfire scenes in John Wick, Heat, Equilibrium, etc. Lots of thump in my chest from those with this behind the seat. It made me want to re-do this with 4 drivers to get even more.
For just general music listening it surprisingly sounds great. It takes a lot of amp to get them to be loud, but at around 35 watts per driver at 1 meter it was plenty loud for me for music and was capable of digging quite deep. Deeper than I expected. I would need a lot more amp to use them in a larger room and listen at greater distance for sure, but to off set that I would rather use more drivers. That's a future project.
Here's some measurements. The top two are near field. The upper driver is in red. Really nice response from 30hz to 180hz. The drop at 34hz or so is due to the narrow wings at the top of the baffle. The bottom driver in blue. Same response, however, it has much longer wings next to its baffle and so I get the low end response from 30~34hz back. Learned a lot with just that simple bit on the sides with the baffle. For mid bass this didn't matter. For sub-bass it would matter a lot. When measuring these I referenced at 99db.
The green line is at the listening position with the room involved. Surpringly not bad, it kept bass pretty decent to 30hz. A little EQ and this could be flat. I referenced this at 90db. Ultimately this wasn't meant to do anything at 30hz or over 100hz. I just wanted to see what it would look like with the open baffle. This graph doesn't show it, but I later used a crossover in the miniDSP to set it to basically focus on 45hz to 100hz as a mid-bass slammer module.
Fires into our guts and chest behind the seats.
It's really back heavy with those magnets. It actually leans on carpet. I think I will put some small feet in the back to keep it straight to counter the weight.
Learned a bunch about open baffle with this. Will explore more. Also learned a lot about tactile response and impact. Going to focus more on this now.
Very best,
Great build. I love that little HF trim router, have the same one and same yellow bits. Ever had the chance to try out the bass-shakers you bolt on to furniture? I added some for my kids and they are indeed fun. I would love to know how the effect compares between them and your setup.
$29 router from Harbor Freight! I forget which bits, bought them separate. I usually don't recommend cheap tools, but this thing has been doing a good job. It cuts circles and rounds edges without a fuss. My first bit lots its bearing and gouged into my timber. I was so pissed. These days there's no telling what's good and what's not good, I don't trust any brand from 2019 to 2023, they all were "made poorly" during this time it seems.
I've not used bass shakers. I was thinking about them, but opted for woofers instead. I know shakers are fun for vibrating things, but they don't put the thump feeling in your chest. I really wanted that more than anything. After doing this, it definitely takes more surface area. These work, but I wanted even more. I've seen folk using 18"~21" drivers behind seats for this purpose with no enclosure at all. I figured two cheap 12's is similar enough to almost an 18's surface area. But now I'm thinking 4 drivers will be even better. 113 inches^2 per 12" driver, so four will get me to 452 inches^2, at just $29 a driver since I already bought a bunch of these to play with. That's more than two 15's. It would take two 18's to surpass the 12's in surface area and cost loads more. So for a fun experiment, these fit the bill.
My next integration is going to be 4 drivers, so the baffle will be about 36 inches wide, 30 inches tall, and I will extend the footer/base more, so maybe 16 inches down there and keep a little bit more wing length on the sides of the open baffle and will mount the 4 drivers in a "::" fashion. Wired series and parallel for 4ohm load. Power handling will go up tremendously and reduce each one getting near xmax even more while getting even more impact.
I konw some folk combine woofers and bass shakers. For pure cost and simplicity, bass shakers seem to be the way to go for just tactile response and they seem to simulate infrasonic bass in many ways. The only thing missing is the chest thump from a sound wave.
Very best,
I've got my setup delivering a very satisfying chest thump right now. I have an 18" open baffle 3-way, working with a dayton rss10-hf sealed sub, with the 2 bass shakers on the couch cross boards. Everything is active/dsp.
The bass shakers can hit pretty hard if they can be directed into the body through a large surface area. I ended up applying low-shelf of +6db at 20hz to really be present for the 20-40hz range, then tapering off slowly with a 60hz cutoff.
For the cost and ease of install they deliver a lot of fun. If I see any cheap 12" im going to give your route a try too.
I need to try some bass shakers too. I have plenty of low end rumble in my room, 20hz is no problem. My main thing I wanted more of was a shocking clack and thump/thud with gun fire type stuff. Impact stuff. It's one thing to crank SPL but wanted to try other methods to get some feeling without necessarily using dangerously loud SPL.
Which shakes are you using?
Very best,
Thanks, do you have a thread with your OB subs? I'm interested to see more. I'm already wanting to re-build with 4x drivers and already shopping for large 15~18 inch woofers for the next-next iteration potentially. Not for theater, but strictly for stereo music listening. I expected a low bass anemic experience based on how I've seen others respond to open baffle, but these two 12's in this open baffle get down to 30hz no problem. And it wasn't my imagination, when I measured it, I was shocked. I didn't expect them to do this well in an open baffle; especially one that wasn't even ideally designed for bass output (I never tested the wing lengths). But it definitely wet my appetite for larger drivers with some more power behind them and more attention to the baffle width and wing length, maybe in an H configuration, maybe 4 subs. Ultimately I'm envisioning two sub towers of open baffle 15's or 18's (two 18's would be neat maybe, like those Stereo Integrity HT-18 V3's).
Very best,
It’s just a personal preference. Here are some (probably controversial) reasons:
1) For longevity; I hear about people “replacing caps” a lot more often than I hear about people “replacing inductors”
2) Sound quality… I’ve built serial first-order crossovers both with-and-without capacitors and found I like the capacitor-free “Acoustic Reality” crossover the most. The difference is subtle but it sounds a touch more transparent and vivid to my ears.
3) There’s something strangely cool about Inductors to me. I have this weird fantasy of building an entire crossover just from a continuous long stretch of wire with inductance and resistance coming just from the wire. (I guess it would need to branch at points).
4) I’m weird so don’t listen to me ;-)
That said I’m not entirely against caps and plan to use them in an upcoming build.
Yup, that clasifies as weird for sure. But its perfectly fine with me.
I remember Gizmo (Harvey Rosenberg) admired tube amplifiers with no caps in signal pass, all transformer coupled.
Just do not cramp those inductors so close to speakers or any other metals.
http://www.troelsgravesen.dk/coils.htm
I remember Gizmo (Harvey Rosenberg) admired tube amplifiers with no caps in signal pass, all transformer coupled.
Just do not cramp those inductors so close to speakers or any other metals.
http://www.troelsgravesen.dk/coils.htm
Attachments
I’m thinking of doing a group buy of some Misco Ventuno 21” subwoofers. Look like great specs for OB. I have a pair coming for evaluation. If there’s enough interest maybe we can get them to do an edge-wound version with slightly higher sensitivity. https://store.miscospeakers.com/21-inch-subwoofer-93064
Some of the SB Audience drivers also look real nice.
Nice,
I can't seem to find SB Audience drivers where I am. Not even on Ebay or anything. I went looking for one for a full range build, but can't. I guess it's a EU/UK location brand?
Very best,
Malveaux, Madisound has them.
Greg, those Zisters really should be mounted on a heatsink for full 25W capabilities, and your Rp resistors are likely going to need one. 4 ohms across the load before xover will shunt full bandwidth and get hotter.
I have no problem with the ARSXO, but the capless version sucked a LOT of sensitivity from the system. In your case, the large loss is welcomed by using an OB arrangement.
Greg, those Zisters really should be mounted on a heatsink for full 25W capabilities, and your Rp resistors are likely going to need one. 4 ohms across the load before xover will shunt full bandwidth and get hotter.
I have no problem with the ARSXO, but the capless version sucked a LOT of sensitivity from the system. In your case, the large loss is welcomed by using an OB arrangement.
Great thanks, looks like Fostex, Mark Audio, SB, etc, all there. Sweet. I was wondering where I could get this stuff, couldn't find it on my normal outlets.
Very best,
I prefer the solid carbide spiral up-cut bits. The clear the chips/dust and cut cleanly, if you have dust collection, that helps a lot. The bits with bearings are fine for following a template but the spiral bit has cut the cleanest holes for me, even in baltic birch which likes to chip.
J
Thanks; just found the drivers there. Appreciate it.
I was struggling to find some various 8" full range drivers that were not expensive so I could play with a few builds.
Very best,
It has a lot of builds in the Full Range forum and gets used a lot and is cheap at $60/driver. I'm curious about them in open baffle application too.
Very best,