Originally Posted by arnyk
Originally Posted by DS-21
Originally Posted by arnyk
Originally Posted by DS-21
I would guess that the HB5000 driver has a little more throw than the Sub1500's 18mm geometric xmax, because the basket (shared with their W15GTi car sub) has greater clearance than the Sub1500's old-style basket.
While there are current 15" drivers that have more xmax...personally, I'd take a JBL driver with "only" ~18mm rated xmax but a 4" voicecoil, well-implemented shorting rings, and obvious attention to heat management over pretty much any of them.
I hate speculation, especially when reliable facts are at hand.
But assuming we're talking about drivers for use above the first-mode region (i.e. above 40-50Hz), there's more to it than just displacement.
If you could illustrate that by means other than hand waving, rumor, questionable claims, and speculation, I would be happy to agree.
Actual performance measurements would suffice. ;-)
Seeing nothing reliable, my opinion remains unchanged.
Arny, your response puzzles me, especially since I provided data in the form of pictures showing conclusively that the only thing about the JBL W1500h in the sub discussed above that would legitimately "remind" anyone of their old 2235 is the logo on the back! The basket, soft parts, and motor are beyond-any-reasonable-doubt very different.
Also, I provided a link to measured data of a system with a driver that has the same basic configuration as the Fi unit. with a very long overhung coil and no shorting rings in the motor. (The eD driver has a stamped basket, and less throw. The former, I think you'll agree, is a distinction without a difference in this context, and the latter, if anything, only casts further doubt on the Fi driver's real world performance, given that its longer coil makes an even bigger inductor, with larger inductance variation over its stroke.)
Perhaps I should've offered a contrast with data from subwoofer system based on a woofer designed for high-fidelity reproduction measured by the same source. Here's a correction to that oversight.
Here are Klippel measurements for a variant of that driver:
Yes, that particular sub is a 12 with a lot less displacement. I went to it because I wanted to show measurements from something reasonably affordable. (As opposed to, say, the LMS Ultra driver on that page.) Also, it's worth noting that a decade-ish ago Keith Yates measured four of an earlier variant of that Peerless woofer in a large vented box with 250W each, and found that Genelec system sufficient to generate "cinema reference" bass levels levels down to 20Hz.
So greater volume displacement won't necessarily provide any performance differences for people who listen at or below "cinema reference" levels.
Also, here's some "data" about Fi's build quality and attention to detail, from my old Ava18, that I posted to AVS a few years ago
But more generally, which of these statements do you find objectionable:
1) A low-efficiency woofer with a basket that provides lots of mechanical clearance, a wide surround, and multiple gap venting (JBL W1500h) is very different from a high-efficiency woofer with a basket that provides a lot less mechanical clearance, a narrow surround, and a central pole vent (JBL 2235H).
2) Considering the observed similarities in the soft parts of the W1500h and the old JBL/Revel Sub1500,
, but that the W1500h has more motor (double-stack of magnets) and a basket with visibly more clearance (shared with, inter alia, Harman's W15GTi car sub
), it's not really "speculation" but more "inference" that it's probably going to have a little more throw than the earlier driver (but not much more, because the soft parts seem the same).
3) For a given stroke, a woofer with low normalized inductance (Le/Re) will have a flatter native frequency response in the upper bass than one with high normalized inductance.
4) A driver with a long voicecoil and no shorting rings has both high normalized inductance and large inductance variation over its stroke or Le(x) in Klippel terms. The higher inductance and Le(x) creates audible distortion (for lack of a less-stupid word, a "sluggish" or "plodding" sound, like the fundamental shakes the room just slightly after one has already heard its overtones) compared to a driver with well-controlled Le(x) in the top half of a typical subwoofer's passband.
I expect #4 is the only one you might reasonably find controversial. Fair enough. It does depend on how one uses the driver, and the cheap/crude ones are great in terms of price-performance for use as dedicated air pumps where human hearing is relatively insensitive. But when asked to play the whole bandwidth expected of a typical subwoofer (LF cutoff up to 80-120Hz), they just don't do the job well in my experience.
While I can't offer hard data - I don't have any example of what I'd consider an inferior bass unit on hand, and haven't bought such a thing in years - here is my most recent experience. Many years ago so I bought the above-pictured Ava18 (made by Fi). It did not have shorting rings in the motor, and the claimed normalized Le was under 1mh/Ω. I had previous experience that high-inductance drivers were bad news. Specifically, the old Stryke Audio HE15, which was a TC Sounds driver based on an earlier variant of the motor used in this driver.
It sounded horrible compared to a much smaller Peerless XLS-based sub that had similar capabilities down to 25Hz (passive radiator 12 compared to closed box 15). But at the same time I bought the Ava18 I had also purchased bass EQ capabilities I didn't have during that comparison, in the form of a Velodyne SMS-1 and two Crown XTi2000 amps. So I convinced myself that the Ava18, considering its stroke (dual-gap motor with a more-or-less evenhung coil, not a very long overhung coil), would make it a basically different experience from that old Stryke-marketed TC Sounds woofer with smart use of parametric EQ.
Oops. While the Ava18 provided more pressurization on movie special effects such as the helicopter drone in Black Hawk Down than anything I had previously experienced, when playing music with lots of upper-bass content it just sounded bad. There was that same "plodding" (for lack of a better word) quality to the bass like the old HE15, regardless of how much EQ I threw at the top end of its passband. (I later measured my driver, and found that the published value of Le was less than half of what I measured on my unit.) That was after
EQ, not before it. I ended up getting good bass at the primary listening position (but nowhere else) by adding a big and ugly pro audio sub
behind the listening position, and only playing the Ava18 very low. The big pro box behind my couch was ugly, but it worked, and a twentysomething grad student can get away with "ugly."
That was good in a way, because it led me down the path of reading about how to get good-sounding bass over a wider listening area in a real room, and ultimately to Dr. Geddes' setup methods for multiple subwoofers. (Ironically, my two "broadband" subs in Geddes-speak at the time used the aforementioned JBL 2235. It was fine for that use, though a little light on throw compared to modern drivers.)
Later, I was able to eliminate the giant ugly sub behind the seat (while keeping the other "Broadband" subs) when I replaced the Ava18 with a driver of better design, Exodus Audio's Maelstrom-X. The Mael-X was very similar to the Ava18 in most ways: both were long-throw 18's with foam suspensions and dual-gap motors, and they were drop-in replacements for each other. But low inductance and Le(x) variation were design goals for the Mael-X.
FWIW, here's how the models compare for both drivers, in 120L cabinets with 2kW of power:
As a postscript, I subsequently replaced the Mael-X with an Aurasound NS18-992-4a.
It did so for the sole reason that the other subs in my room used Aurasound drivers, and I wanted all my bass drivers to look the same. I also hoped for slightly better performance, as the Aurasound NS drivers basically define the current state-of-the-art (underhung motors with wide but relatively short voicecoils, copper-sleeved poles for very low inductance and very linear Le(x), neo magnets, etc.). The NS18 has much lower inductance than anything of its displacement. After actually doing the swap...I doubt I could distinguish the Mael-X from the NS18 in a blind test, even though the NS18 technically has a fair bit less throw. Still I sold the Mael-X fairly recently, simply because I like knowing that all of my subwoofer drivers have the same design. Prior to buying the NS18, I briefly owned a TC Sounds LMS Ultra, which is the immediate predecessor to this driver.
Despite the longer stroke, it did not appear to be an upgrade for my uses, so I took advantage of one of TC Sounds' periodic bouts of insolvency to unload it at a profit. So there is a threshold level of where "better" is "no different." I've found that for most uses, very-long-coil overhung drivers with no shorting rings do not meet that threshold, though.