Stereo Integrity HS-24 - Home Theater Forum and Systems -

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post #1 of 44 Old 09-17-14, 01:33 AM Thread Starter
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Stereo Integrity HS-24

Hello all,

This build thread is long past due. I’ve been promising myself and others for nearly a year now that I would finally do it and, for once, life seems to have given me the time to sit down and finally get it done or, rather, to get something, anything posted in time for this year’s MS fund drive. For, you see, I’ve a bit of a confession to make…

I was the winner of last year’s raffle. I won the magnificent beast that is the Stereo Integrity HS-24, Serial Number 0001.

Until early last year, I had been on a several years long audio hiatus (boo recession!), and upon my return spent a fair amount of time catching up on the forums to see what I missed. Adire, an old favorite, was gone with its Tumults and Parthenon. Exodus had brought out an impressive 21” driver and away it went just before my return to the hobby; the Sicko never beat the hangups of manufacture. Pretty depressing, really, it almost seemed as though sub design for the home audio market had regressed ten years and advanced only in higher pricing. That is until I found one of the rare high quality, high value outfits still out there, Stereo Integrity, and posts showing the arrival of parts for a new prototype driver of no ordinary size.

Admit it, no one who clicked into this thread escaped the feeling of awe that monster inspired from those first moments. As more information trickled out, my interest only grew; images of that massive frame and cone, a hefty motor mounted beneath and respectable drivers off to the side dwarfed in contrast…I watched for progress updates often as I could. Once the excursion video came out, I was obsessed with that beast.

I didn’t think I could ever own one, though. Last year was an unusually difficult one; audio for me was a respite, a sanctuary for my sanity, as much as it was a money sink as it is for any of us. Still, the 24” was beyond me at its ridiculously low (far as I was and still am concerned) introductory price. So I thought, that was, until the generous folks at SI put one, the first one for resale, forward as a reward to someone for doing their part to help a good cause. Put forward money to help good people with the prospect of winning the driver I’d been wanting for months? No brainer.

What I didn’t expect was rare fortune and winning the drawing. It took a while before I could convince myself that a friend wasn’t pulling a prank, but when it sank in…well, the language I used can’t be repeated here , but fair enough to assume that I wasn’t merely ecstatic.

I had won one of these beauties!

Oh yes, that was a good day indeed. Funny, ultimately, it’s just a subwoofer driver, but at that moment, it was precisely what I needed and wanted. My house, though, may never forgive me.
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post #2 of 44 Old 09-17-14, 01:43 AM Thread Starter
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Re: Stereo Integrity HS-24

The wait for the HS-24 to travel all the way across the country wasn’t long as far as the calendar was concerned, but it was a mighty long wait for me. I couldn’t quite shake the fear that something would happen and that it wouldn’t make it for some reason or other. When the day of arrival, well, arrived, I made certain I’d be home to greet the sub to guard against rain or theft, but mostly because I didn’t want to leave the FedEx driver to wrangle a box of that size and weight alone. That proved to be an issue: the box for an HS-24 is nearly the size and weight of a dishwasher.

The delivery person thought it was indeed an appliance and tried to find the back entry of my somewhat overgrown corner lot rather than schlep it to the front door, which resulted in an odd foot chase as I ran around front, then back and then front again chasing a delivery truck that couldn’t make up its mind where to stop. I caught up just in time to watch the substitute driver shove the box out and fall into a storm drain. (Grumble. The driver’s too tough to care about a small drop, fortunately.) Frustrating, yes, but it let me guilt the driver into helping me get the dripping box up my front steps saving me the hassle of wrestling something a bit bigger around than my arms can reach.

So, there it was at last, the first HS-24, the sub driver I’ve most wanted in a long time, filling my living room with furniture pushed aside to make room for it. Let me say this: no matter how large you think this driver is, it’s bigger. I paced out floor tiles visualizing what it must look like in person, countless times. I tried to hold my arms out in a hoop about right to visualize it. I pulled a tape measure out and laid out a rough diagram. All that effort was wasted. The HS-24 is larger. It is the most visually imposing driver I’ve ever seen. Nothing else comes remotely close.

(If you look real closely, a CD may be visible.)

(JL 12W0 pulled out of my truck.)

Now, in a past audio life, I had dabbled with vintage audio and as such came into the presence of attempts from decades past in large diameter drivers. I’ve spent some time around Hartley 24” woofers and seen an EV 30” in passing. At the time, they appeared huge, but, in retrospect, they seem frail and underwhelming. The HS-24 is superbly, powerfully proportioned; the frame, the gasket, the surround, the cone, the motor, even the dust cap, all looks right. Nothing’s out of scale; it’s just that that scale is huge. It looks like a very well built, powerful, high excursion 12” driver, but one that’s just a wee bit larger. Seeing this woofer in person takes some time to adjust. When it was first out of the box and sitting on the floor, my brain had trouble accepting its size, perceiving it as a 12” driver up close, but when I reached towards it and my hand kept going past where my brain was interpreting its position, feeling that little tick like being hit with an optical illusion. Once that stage passes, and it does take a while to pass, there’s only an overwhelming urge to have a little laugh when seeing it. Almost a year later, it’s still there, that urge to laugh in joy at this huge, powerful driver and its imposing presence.

Yes, I still do quietly laugh sometimes when I see it. You would, too. This driver changes one’s perception of just what exactly a “big” driver is. Ever since the first day, 15” woofers look like midranges, 8” almost as tweeters. My sense of scale is off; I know an 18” driver should look huge, but I can’t make myself see one that way anymore.

(Left to Right, Top-Down: 10" Peerless, 15" Adire Tempest, 8" B&Ws, 12" JL, SI HS-24 [set back from other drivers and so looking smaller], 15" Adire Tumult)

I never could get past the size, but eventually I did take to looking at more details. The driver is very well put together with a rare attention to the major elements and detail I appreciate. Off and on, I’ve seen the occasional woofers of a professional audio heritage that feature bolt on gaskets and spiders. Frankly, it’s a great idea for strength and serviceability, but as it costs more, a lot more than a bottle of glue, you just don’t see it very often. Maybe it’ll be found here and there with the real expensive drivers and, as one exception in the home market, with Tannoy dual concentrics, but not in subwoofers where it would really make sense. (Bolt on motors hardly qualify when a new basket assembly costs hundreds on its own.) Stereo Integrity didn’t skimp here, they went all out. The gasket, a hefty presence on the rim of the basket, bolts on and the spider is bolted on, all using more expensive stainless socket cap bolts (even on the spider where they’ll almost never be seen) rather than settle for something cheap. That made me happier than it should’ve, but, far as I was concerned, someone finally did it right. (No risk of a spider coming loose from the landing from glue failure as has happened to me before.) Even the where the voice coil met the cone was epoxied/glued tidily, not a glopped on mess with runs everywhere like one tends to see, even on expensive TC Sounds drivers (surprised me). These little details tell of pride in the product.

Oh, and yes, she’s a looker. This driver is not only impressive looking, it’s an attractive design for a driver. Before the 24 arrived at my door, I had some doubts about the gasket, dust cap and cone treatment. Small doubts, granted, but it was difficult to tell how well the overall effect might be in person from photos posted on the forums. I was wrong. In person, the HS-24 is one of the better looking drivers out there. It just plain looks good. Everything works and I wouldn’t change a thing; I wouldn’t even recess it much so the gasket can still be a design element. This is not a driver to be hidden under a downfiring box or behind a screen. If you see it in person, you’ll feel the same and want it up front and center staring you in the face.

I could never content myself just looking at a speaker or subwoofer without hearing it. Even without a box, I just had to see what this electromotive gorilla could do and, again, it exceeded my every expectation. Free air, sitting on a piece of foam, the HS-24 was producing better bass than many higher end floorstanding speakers I heard back in my more audiophile oriented days. The cone is just so large, it’s a dipole radiator in its own respect. A baffle would almost not be necessary if using this driver in an open baffle configuration. Massive swept volume, a good Qts for the purpose, high excursion potential and powerful motor, it has great potential. Had I two for a stereo pair, I’d seriously be considering trying them as open baffle woofers; I was so impressed by this performance and sound quality.

The motor was fairly quiet even when pushing the cone a fair bit and to that, there was no doubt. This motor is capable of massive excursion. (The motor only looks small because everything else is so large. It’s a big one in its own right and the voice coil is no slouch either; it can take the power. Design experience in car audio pays off here.) Playing a low frequency signal, the cone would move a scary amount with no trouble and with a cone that large it is intimidating (a friend of mine seeing it was afraid to look too closely because of that). No doubt about the power, at one point, I hit what must’ve been the mass resonance of the driver and the driver, the whole thing jumped (jumped!) up into the air off the foam block it was on forcing me to react quickly to mute the amp lest it be damaged somehow. That was…wow. I love this driver.
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post #3 of 44 Old 09-17-14, 01:47 AM Thread Starter
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Re: Stereo Integrity HS-24

A driver does not a subwoofer make. I had the most powerful driver in manufacture, now I needed something to put it in. Trouble was, I have no table saw nor friends with one. My trials with my old, iffy circular saw proved that was not an option. So began months, yes months, worth of frustration as I attempted to figure out someway, anyway to have wood cut so I could glue up a box of some sort. That was no mean task, unfortunately.

When the recession struck this region, many of the small cabinet shops within reasonable driving distance had to flip the closed sign one last time and find a new way of making a living. With things starting to improve, there’s an influx of people out here from the cities looking to build their McMansions with custom cabinetry and those cabinet shops/carpenters who survived the hard times are too busy to worry about a small one off job that they feel is beneath them, to build a sub box or even spend a few minutes to simply cut the wood for one. One was mighty arrogant about that, not all money is equal apparently. That was more than a little frustrating as I had to sell my kayak to afford to get this done right.

Well, other options I tried didn’t pan out, though I put way too much effort into finding help for a couple of months. At one point, I even considered building something log cabin style with 2x4s (surprisingly, that would be cheaper to do than build a box with hardwood ply and be scary strong), but weight considerations nixed that. Finally, I was down to a few last days when I’d have the time to devote to building something and fell back on the years old option of the desperate: Home Depot handy panels. Ordinarily, this isn’t the greatest option, but the local store received an unusually good quality shipment (it does happen) of “birch” ply; only a couple of tiny voids, no delamination and a harder than usual hardwood dark center ply, it was a good option. Though not what I wanted to build, it was something and off I went. Not the finest box, but a better outcome than I expected.

(My, what a handsome fellow.)

As I said, the HS-24 is larger than one thinks. I may not be basketball player tall, but I am not a small man. That cutout is huge. Ninety some percent of subwoofers on the market could fit through that hole, box and all, I’d bet. Sitting mostly comfortably in that box, I’ll admit that I did consider mounting the driver like a hatch and sit inside while playing it. That could’ve proved to be…interesting, but is too intimidating a thought to go through with it now that I know just what the beast is capable of.

Once I had my fun sitting in the box, it was time to get some bracing in it. ¾” hardwood ply isn’t enough on its own, especially with a box that’s two feet square and four high. Lacking a table saw and sufficient panels of the right size (that box used up all the good stuff of the dimensions I needed) to make braces inside, I opted for the option many here use of ribs and boards set crosswise. The cutout for the woofer was certainly large enough to let me work through it without any trouble; it was as though I’d left half the box open.

I’ve seen a lot of builds using dowels, 1x2s and 2x2s and looked into that, but the wood we had here was terrible. A goodly portion of the lumber for the country and others comes from this region (I drove past a shipload of logs headed to China to get to Home Depot), but it seems we ship the best away and leave the dregs. The dowels were terrible, the 1x2s couldn’t support their own weight and the 2x2s I could snap in one hand without trying. They weren’t options. I couldn’t see them adding any stiffness as they’d surely only flex and vibrate. Fortunately, there was a batch of rather nice, straight and clear 2x3s. With the scale of everything else, I figured, why not? Around 80’ of 2x3 later and stuffed to about 1.25lbs per ft^3 as per Tom Noussaine’s findings, I felt the box was sufficiently rigid to give it a try.

This is how you do a 2.1 system:

A bit of whimsy caught me, 3" TangBand W3-871S seemed just the thing to pair with a 24" sub for the first run.

Last edited by Erasmus; 09-17-14 at 02:00 AM.
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post #4 of 44 Old 09-17-14, 01:55 AM Thread Starter
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Re: Stereo Integrity HS-24

What of the sound? Beyond words.

Truly, superlatives are not wasted on this driver. The HS-24 is simply another level beyond other subwoofers. I’ve heard excellent drivers before and excellent bass setups and this one driver in a subpar box with a mediocre amp powering it will either stomp them or go round after round with them. Any driver you name, you will require multiples to come up against a single 24” and even then, I don’t know. There’s something special about a single source with this much surface area and displacement that multiple units seem to lack. I’ve tried to think of how to describe it, but my vocabulary stems from other subwoofers and I think drivers of this scale require a new set; my attempts end up straying to terms like acoustic impedance matching, scalar vs. vector values (sound pressure vs. particle velocity) and the like. This sub has a more palpable, tactile feel to it, than any other sub I’ve encountered. It reminds me of horn loaded bass or of the massive Magnepan Tympani dipole bass panels I ran a few years back, not a simple piston in a box.

To get back to something more grounded, the driver sounds clean. There aren’t any obnoxious artifacts on the top end that would require someone to watch where they roll it off. I’ve even run the 24 letting its inductance be the crossover and was happy with the performance. Where it operated, I never heard anything to indicate the driver was giving out before the amp cried uncle; no harshness, no crushing of dynamics with increased volume (except for amp clipping when I got carried away), just good, clean bass of rare quality and levels heard even less. I wish I could say how high those levels are, but I’ve relied on a borrowed Radio Shack digital SPL meter and it only goes to 126dB. Room gain is awesome.

(Nearfield: Manly Magenta, Listening position: Macho Mauve )

Down low, though, down low is when you realize something only those with big bass arrays appreciate. Often, some poster or other on the various audio forums will repeat the widely held belief that low bass is not audible with the audible cutoff being somewhere between 40 and 20Hz, that below that audio is a tactile experience. I kind of also used to think the same. Well, after running so many test tones through this driver that 20Hz now sounds high pitched, let me say that audibility extends quite a bit further down. Try about 12Hz for tonality with “hearing” in some manner a few hertz below that. This driver on its own can provide audible single digit output at high levels with room gain even in a large room.

(Preliminary results, temporary listening position, I need to revisit this with a better mic.)

I am not kidding. This is a big room, but it did it. I couldn’t believe my eyes with these sweeps and kept running one right after the other, but the results kept showing plenty down low. My body was feeling it and my ears were hearing it. My mind didn’t want to believe it until one last run I turned to glance out my window at the approaching twilight and watched the reflection on the glass move as the large picture window bowed in and out slowly on a 2.4Hz signal. Crazy.

The driver doesn’t care what you throw at it; it will handle the signal with aplomb. Your amp will clip before the 24 will give out; your room will “clip”. One test track I tried at high level I had to stop quickly as I wasn’t hearing just walls, furniture, windows and the floor rattling, I was hearing the screech of framing nails moving in decades old wood. I’ve seen standing waves form in my wooden floor moving up and down far enough to trip me when walking. It’s insane when cutting loose with the 24 at particular resonance frequencies of the containing structure.

I’ve sat a meter away from the driver running sweeps and watched my hair sway back and forth a fraction of an inch before my eyes (I’m shaggy) on a 10Hz signal like seaweed beneath the waves. That’s not uncommon with a powerful ported sub near the port when run below tuning (as any of those cheap bag/blanket trick videos show), but that far away with a sealed unit? It’s moving serious air. Sitting six feet away from the driver when it cuts loose is a more visceral experience than sticking one’s head inside the cone of a more conventional driver.

The low end…nothing short of a rotary sub or many multiples of the best other drivers out there can touch it. Single digit sound is audible with this sub and it isn’t a product of distortion (10Hz definitely does not sound like 20Hz, but it does sound an octave down). I’ve a track with a strong 9Hz signal that I never really experienced before and understood the point. Alone, the music does nothing, but with the 24, the low frequency signal creates an intense feeling of anxiety and disorientation that I was not aware of before fulfilling the intent of the track. By the time it was over, seven minutes later, my heart was pounding and breathing was difficult, like an anxiety attack. So much for the blasé mood I tend to adopt (when not talking about something I’m excited about.) ) I did wonder if it was just me, some sort of expectation biasing my reactions, so I’ve adopted the habit of mixing that track in with my sub demo playlist for the HS-24. Thus far, not one person has gone without noting with surprise a dizzy, anxious feeling right off. Interesting. No wonder there’s the myth of infrasonic weaponry around, this real low stuff when at high volume has interesting effects. Vibrators on a chair don’t have that effect, not at all. The inner ear needs to be jiggled, not the butt, apparently. When I put an amp on with a HPF set at 10Hz, I notice the difference right away. When a 10Hz filter noticeably takes part of the sound away, you know you’re dealing with something special.

Simply put: I love this driver.

Sorry to sound overly exuberant, but it’s true. It is the best out there.

Put a HS-24 in a box big enough for it to be happy and a single driver will make for excellent, high output, deep digging bass in most any sized room for most enthusiasts. ~15ft^3 should be just about right. Bigger is better and will allow more excursion, though. (Mine in its smaller box has no problem clipping a Behringer EP2500 and Mackie M2600; I’ve not bottomed it.) Put a pair in an infinite baffle arrangement and you better invite me over to hear it as that’ll be top tier subbage right there. (I suggest two drivers opposed in a manifold as a single driver could work the framing it’s attached to loose or at least rattle the wall containing it to a destructive degree. It is a powerful driver.)

Anyone considering this driver should really consider picking up two. One will provide the output desired in a .1, but it sounds so good that two will be desired to try stereo bass and/or to even out room response.

Last edited by Erasmus; 09-17-14 at 02:29 AM.
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post #5 of 44 Old 09-17-14, 02:06 AM Thread Starter
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Re: Stereo Integrity HS-24

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post #6 of 44 Old 09-17-14, 08:03 AM
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Re: Stereo Integrity HS-24

Wow look forward to this project.

"Music is the space between the notes"
“[T]o talk well and eloquently is a very great art, but that an equally great one is to know the right moment to stop.”
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post #7 of 44 Old 09-17-14, 09:26 AM
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Re: Stereo Integrity HS-24

Excellent write up! It is such a great looking driver, I wish I could afford one and find the space for it. Do you have any plans to finish the cabinet somehow?
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post #8 of 44 Old 09-17-14, 08:02 PM
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Re: Stereo Integrity HS-24

Oh wow, it sounds dreamy. Great review! How will you finish that monster of beauty? Is this the one he gave away for the MS150 donation?
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post #9 of 44 Old 09-17-14, 08:31 PM
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Re: Stereo Integrity HS-24

That was a lot of fun to read!


If you take yourself too seriously, expect me to do the exact opposite
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post #10 of 44 Old 09-17-14, 09:45 PM
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And now I know what I want for Christmas! Now imagine loading 4 of these in every room corner? At this point it would probably tore down a bunker.
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