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That new-fangled GRS 12" subwoofer

edited July 24 in DIY

So I ordered a pair the other night (Founder's 7.5% Centennial IPA may have been a part of that decision) of the new GRS 12SW-4HE 12" subwoofers. Notwithstanding the bullshit Xmax claims, the driver looks like it has good bones. Deep draw basket with plenty of venting for a stamped design, bumped back plate, 2" coil, double magnet. The advertised Xmax is 12.5mm - but realistically it is likely around 10mm. I will measure the top plate and deduct from the advertised Xmax the dubious addition of "+1/3 top plate".

Anyways, the driver as advertised has really, really nice T/S parameters. It isn't optimized for small bass reflex like a lot of modern subwoofers - but what we lose in small size we gain in extension (Hoffman in the house).

I've been running through models this morning waiting for mama to wake up so we can do our normal Saturday thing, and I am generally impressed. For example, in 1 cubic foot sealed it will have an F3 of a little less than 40Hz and Q of 0.8. This indicates phenomenal performance in a typical automotive environment without eating up space.

Bumping the sealed to 1.5 cubic feet (still a manageable size for automotive) yields F3 of 37Hz. This would also make a compact, wide-range, high output monitor possible. Throw a coaxial in the cabinet with it, and I think it would be a remarkably satisfying small form factor 3-way. It kind of sucks that Dayton no longer sells the 5" coaxial, but the 4" would probably work almost as well. I have a pair of the 4", I am sorely tempted to build this version. Set them on some stands and go bonkers with the volume control...

...skip the stands and build some ported monkey coffins at 3 cubic feet tuned to 20Hz. For maximum output it would require a 4" diameter port 25" long, but in a 3 cubic foot cabinet it should be easy enough to fold on in there. So here are some WinISD charts on this possible design:

Transfer Function Magnitude:

SPL@ 250W:

Vent Velocity@ 250W:

Cone Excursion@ 250W:

Couple of observations based on these models...

Even if port chuffing becomes an issue at maximum output, it would occur infrasonically so it is debatable if it would be an issue. The amount of signal present to excite things at 17Hz will be pretty minimal. Even for action movies it is unlikely to be a concern. Combined with the F3 approaching infrasonic, this alignment would make an excellent home theater subwoofer if you have 3 cubic to spare.

It exceeds what is likely real Xmax briefly in the passband, centered at 30Hz. Above that, no sweat. It should play the majority of music at a very high volume without approaching real Xmax, much less the dubious advertised Xmax. This alignment should also make for a serious party speaker capable of playing pretty much any genre at a very high volume without mechanical concerns. I predict many monkey coffins being built using this driver.

The above are modeled as if they were fully active - what happens with some series resistance? I added 1 ohm to simulate a large, laminate core coil around the 6mH range (as if I were using a 250Hz low pass).

The 1 cubic foot sealed pushes Q to nearly 1, with F3 of 35Hz and a ripple of 1.1db centered at 64Hz. This starts making a very small monitor more and more attractive.

Pushing the sealed to 1.5 cubes yields F3 of 35Hz with a .5db ripple at 65Hz. At a full rated 250W input, it does not exceed advertised Xmax. At 150W, it does not exceed 10MM of xmax.

Adding the series resistance to the 3 cubes ported model, we have a 1.5db peak at 35Hz but F3 is pushed just below 20Hz.

So, for $40 I really doubt you will find a more flexible 12" woofer that performs this well in sealed and vented applications. If you are looking for an affordable subwoofer capable of near infrasonic performance (and I'll be honest, infrasonic for my 46 year old ears is 30Hz these days, not 20) or want to build a really cool monitor that does not take up your entire home studio but will also play to 35Hz this is the driver.

Plus, with the pulpy paper cone it has a classic look. The inverted dustcap is ass ugly and I will replace with convex style, but otherwise it is a very nice looking driver. Fat surround, pulp cone, big magnet - this is a serious throwback design from my car audio days in the 90's. Love the look. Love the flexibility (based on advertised parameters anyways), and love the fricken' $40 price-tag.

If using the Dayton 4" coaxial as the TM portion, you could potentially have a monkey coffin with a 20Hz to 20000Hz response curve and capable of 105+ db output across the entire bandwidth using $150 in drivers. With the coaxial TM portion you have some nice options to control directivity, as well. With the large coil placed in series with the woofer, it even has the advantage of raising impedance to a nominal 5ohm (or higher). I have not run into a single issue over the last 15 years testing 4 ohm drivers and building 4 ohm designs running cheap AV receivers, but the slightly increased impedance will at least put some peoples mind at rest.

In my minds eye, I am seeing this as a legitimate contender in the world of 3-way monkey coffins. I used 250hz as the upper limit based on inductance, that may be the deal breaker on this driver though - I am neither optimistic or pessimistic, I chose 250Hz just because. Crossing lower than that would probably warrant going active or semi-active so value starts declining. I would imagine, though, that hitting 200-300 hz is feasible.

TL;DR The new GRS 12" paper cone subwoofer is, while not quite a game changer, is a legitimate beast-mode(r) driver. Build a bigass 3-way using it. Throw it in the trunk of your car. Impress your musician friends with how badass a 12" monitor can be that does not take up an entire wall of their studio.

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  • Wow - that is pretty amazing for only $40. I don't mind the inverted dustcap. It's better than having some stupid painted/stamped logo to deal with. I'm surprised the sensitivity isn't higher but something's got to give at that price point. It seems like the right compromise for most applications. Fingers crossed they measure close to specs.

  • Interested in seeing your measurements of this driver.

  • Showed up today, they are pretty impressive for the money. However, shit packaging - one has cone sag out of the box. They come two to a box, and they are heavy and have minimal protection against one pressing on the other.

    I'll get pictures and see what PE says.

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  • @Tom_S said:
    Wow - that is pretty amazing for only $40. I don't mind the inverted dustcap. It's better than having some stupid painted/stamped logo to deal with. I'm surprised the sensitivity isn't higher but something's got to give at that price point. It seems like the right compromise for most applications. Fingers crossed they measure close to specs.

    The sensitivity is just Hoffman reminding us he existed. A 12" driver hitting 40Hz in a very small cabinet necessarily gives up sensitivity. Lucky for us it generally is more about displacement than voltage sensitivity with subwoofers. If they measure as advertised, these will be quite popular in both the car audio and home audio world.

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  • So despite the moderately high compliance of ~75L, they have a pretty stiff suspension. Breaking in by hand is pretty futile, so I may have to hook them up out of phase and run some 22Hz sinewaves through them at full excursion.

    OK, quick rundown of my impressions of them. Other than the ~2MM offset on one, they are not bad from a build quality standpoint. The frames are rolled in the right spots - the cutouts, for example, did not cause me to experience lacerations. On Daytons Designer and DA series, I swear you have to wear kevlar cut gloves handling those - worst frames in the business IMNSHO. These are better. Thicker, and as I pointed out, rolled in the right spots for some added rigidity. The under-spider venting is a nice touch, but they are about 1/4" in diameter - I wonder if they whistle at high excursion. It has a very nice bumped and vented back plate - with a nifty screen way up in there to keep the mice out if you use these in a ported enclosure.

    The gasket is the same one-piece foam I see on most GRS drivers - I am certain it isn't to maintain family resemblance. I believe if we were to pop on Aliexpress and look at driver parts, these foam gaskets are probably the cheapest possible alternative short of not putting anything on. The surround is very thick, and in my manual exercising of this driver it exhibited one solid positive and one potential negative. When I manually push the cone to either extreme of its travel, there is no distortion on the surround. The same cannot be said for all drivers with rubber surrounds. I am sure many of you have noticed that wrinkling over the years as you have manually exercised woofers. If not, start eyeballing that. It may surprise you how soon some drivers exhibit deformation of the surround when the cone is moving. I am reasonably convinced this effect helps compound distortion. The potential negative (and keep in mind these are still not broken in as I mentioned above), is the surround seems to have a bit more memory than we want to see in a driver soft part. When pressing the cone all the way in either direction and then letting go of it, it does not (currently - post break in may very well be different) "pop" back into position. The last few mm you can watch it slowly approach center. Kind of weird. But it is a pretty thick surround, on a brand new driver - break-in may soften things up.

    The dual magnet has cheap speaker dual magnet issues - not perfectly aligned. The cone is absolutely beautiful to me - paint 'em semi-gloss gray and these would look a lot like the old Rockford Fosgate Series I 12" woofers I rocked for a while in the early 90's - remember those with the weird half-inverted dustcap? Initially, I thought I would dislike the inverted dustcap on these, but to be honest they look fine. Overall, from the outside they look pretty damn impressive.

    So after my futile attempts at breaking them in, I did do a sweep on both units. Results below.

    (No break-in worth mentioning)

    I am going to go out on a limb and suggest a good break-in will likely yield final results very close to advertised, and that, my friends, makes these one helluva driver for $40.

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  • Oh, the top plate appears to actually be machines but looks to only be about 5 or 6mm thick. So bonus on machined motor parts (very important for unit to unit consistency) boo on the thickness. On the other hand, it means the driver has over 10mm of overhang Xmax. I was scared it would have an 8mm top plate or something drastic given how PE is tinkering with Xmax ratings on their new lines.

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  • These are going to sell like fucking hot cakes covered in warm maple syrup on a January Sunday morning.

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  • These would have been pretty elite 30 years ago - a true acoustic suspension design capable of sub-40Hz performance in a small enclosure with a lot of mechanical throw to compensate for the low sensitivity. Edgar Villchur would be proud.

    I dicked around with modeling software a little more last night - and in 2 cubic feet tuned reasonably low it is still getting into the mid-20's. If you can figure out a port, that is. 3" will chuff at even moderate listening levels, and a 4" would be over 3' long. There are no passives out there capable of doing the job without costing 5x what the woofer costs, either.

    A sealed, boosted alignment is also an attractive option with these.

    It begs the question of why more of the lower priced drivers do not have similar performance - that is why I think these will put the infamous Dayton DVC out of the running. The 12" DVC is currently almost 2x the price of this with a similarly bread-and-butter motor and much less output capability. I guess I wouldn't be surprised if PE releases 8" and 10" models in the GRS line and the DVC are retired. Won't happen, I just wouldn't be surprised if it did.

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  • I hope not, the SD series are wonderful!

  • @Wolf said:
    I hope not, the SD series are wonderful!

    Agreed. I really like the new GRS 12" paper cone as a sub. The SD series (8", 10", and 12") are really dual voice coil woofers - much less voice coil inductance than the GRS subs and smooth response out past 1 kHz.

    This sub really makes me question why someone would choose the DCS305 at $110...

    Keep an open mind, but don't let your brain fall out.

    Sehlin Sound Solutions
  • And now PE has the 15 and 18 listed. Incredibly low prices, and good specs.

    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • @rjj45 said:
    And now PE has the 15 and 18 listed. Incredibly low prices, and good specs.

    I don't see them?

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  • Me either.

  • @rjj45 said:
    And now PE has the 15 and 18 listed. Incredibly low prices, and good specs.

    All I see are the professional series.

  • Um, you all are right of course. "PRO" GRS woofers.

    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • "It's Friday night, Clipper Dark Light, what a combination!" =) Some of you young'n wouldn't remember those lame TV ads.

  • If that 18" meets it specs & can hold up to some moderate thrashing, it would make a decent budget sub for small bands. 93dB Sensitivity isn't nearly as good as it's pricier competition, but for $'s worth a gamble. In pro-sound, it's all about displacement. ;)

    I used Peavey Low Rider 18's (a budget fav around here) in my big old 14 cu/ft dual sub boxes and these GRS seemingly go just as low and the displacement is within a mm of the Peaveys. Back then I think I paid $350 for the birch ply & $850 for the drivers and another $200 or so to finish them off. You could build 4 dual 18 boxes with these and only spend a few hundred more!

  • Are you still running live sound Tom?

  • Nope - sold off most everything last year. Just a few things left in the garage. Those subs paid for a really nice lens for my camera!

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