The Arx Subwoofer thread

[Jon Lane]

Arx forum readers will recall that an Arx subwoofer had been raised as a likely new Arx product (click). A few of you have spoken directly with us about it. Since then we've gained the insights I think we need to fulfill one of the Arx community's preferred categories for a subwoofer design and we're ready to start talking about it.

(Before we say more, a disclaimer is in order: This conversation is not a commitment to either produce the design we're about to describe, nor is it a commitment to schedule the rollout of such a product. The purpose of this conversation is to lay out a strategy for a type of powered bass speaker that we at TAI and some of our readers and customers feel is a smart design with a potentially smart placement in the marketplace. Should this strategy prove sound, at that point we'll start talking about a detailed product description, the firm price, the introduction, and the arrival schedule.)

This said, the parameters are approximately these (again, subject to too many variables to allow us to commit to any one of these parameters or a set of them). This is really our shared wish list:

• A 10" single-SplitGap powered subwoofer
• Approximately 20Hz bass performance (-3 to -6 dB) at at least 100dB
• Sub-$500 price class
• Under 18" on a side - a simple cube
• Typical minimal Arx cosmetics, but heavy construction and very good performance
• Perhaps most importantly, a kind of audio performance that lends itself to Arx. This is not to be just another box that goes boom in the room.
• Modularity. A construction style and an economy that when used in multiple units we hope can allow this one product to scale its particular response and sound quality to nearly any level.

TAI feels that this set of basic parameters should guide the development and the success of a new Arx "ASub 10" product that, like the other Arx models, represents a similar product category as the predecessor Acculine products but at a much higher performance level.

So far this design demonstrates an unusually high degree of accurate and musical performance for the projected price category, but it does not compromise excellent performance with the mandate that this one product fills all needs for loudness. This is an important point: This design we think has the basics to really sound good, but at under 18" on a side and under $500 (or even under $400 if I dare to suggest that) just not to be our #1 contender for the loud-at-any-cost engineering that dominates the market.

100dB (and probably more) is a substantial level for an economy high-performance woofer with a genuinely full-band, linear, good-sounding response, but for users who need more, a pair of these affordable subwoofers, probably for under $1000 (and positioned to interrupt standing waves), could reach some 110dB in the twenties in-room and do so musically. A quad of them would power all but the largest residential systems - with real sound quality - and for under $2000.

This would be a modular product in the economy + performance class, meaning that it'd be both competent enough and inexpensive enough to make all kinds of sense to use in multiples in order to build just about any level of really good sounding bass you'd want.

But the really cool thing about this product would be the level of enjoyment just one unit would bring to thousands of typical mixed-use music and home theater systems. Cost would be kept very low yet performance would be genuinely superior.

Such an Arx product we expect to provide the style of Arx, the value of Arx, but a sound quality that we think could be fairly unique in the market at this price level. Naturally we'll do everything we can to lower the price to really suit the Arx family it would be part of. And in a modular format like we're thinking, low = more = happy.

We'd like to continue work on the concept and should it prove productive, offer some graphical representations in the next few posts below this one of what this design can do.

Please remember that I'm sharing our thinking here, reporting on about half of the development project, and that the risks of doing so without a final model in at least prototype stage are still written on this project. Don't hold us to any of this yet.

But...TAI would like your opinions. How does a uniquely-engineered subwoofer, priced perhaps well under $500, and making the full spectrum of very good-sounding bass strike you? How do you feel about being able to take this building block - which gives anyone an entry level to great performance - and expanding your system with it?

[Jon Lane]

The 10" subwoofer design we're working on for Arx is showing us ground plane sound pressure levels in this range. Note that the scale is 20Hz to 200Hz and that this response is near the design's maximum power input.

woofer spl.JPG

It's important to note a few things:

• Typical corner placement of this design in a room will boost the entire response curve and flatten it as well. What you see here is not what we'd get in our homes; it's more conservative;
• The lowpass knee's profile above 80Hz indicates that we've dialed in a classic 2nd order per octave attenuation to show the speaker's typical lowpass point of 80Hz. This could be converted to the usual 4th order crossover at 80Hz in any common AVR with configurable subwoofer crossover settings. A subwoofer we'd produce from this design would include this variable on-board;
• The highpass function above 20Hz, which defines the specification we all look for when doing a cursury evaluation of a subwoofer, shows us not only a 20Hz extension, but actually shows us an amazing -3dB attenuation below roughly 60Hz, which roughly compliments 3dB of room gain with each octave below that point.

The latter is a remarkable specification because it demonstrates that should we be able to pull it off, a compact, affordable subwoofer made from this design will spec close to flat in-room to below audibility.

There's more: The highpass knee shape also defines a speaker's transient characteristics - its time delay and phase - and in the case of this design that delay is both low and very linear. This design behaves like a sealed system below its bass cutoff and so avoids the overhang and delay of boosted ported systems.

In fact, this design is even complimentary to the Arx A5 at the usual 80Hz crossover point too, meaning that a pairing of the two should offer really "transparent" system setup. The main speakers and the subwoofer would sound like one speaker instead of sounding like there's a sub in the room.

I've used similar designs before and one of the most remarkable systems I've ever head consisted of this style of woofer - also a 10" design but used in a pair for left and right - coupled with an 8' electrostatic tower (click). If you've ever heard a large panel speaker from Acoustat or another comparable brand you know they sound very "fast", which owes to their lack of phase and time corruption in the audible bandwidth.

With the dual 10" subs installed and run through a simple setup routine to match their crossover responses and levels to the electrostatic towers, we found we could not detect the bass systems whatsoever. The system sound was as if the big Acoustats themselves had bass to below audibility, which with as fast as the Acoustats sounded, was a rather astounding thing to hear. The bass was lightening "quick" and the overall effect of hearing only one big fullrange system was entirely convincing.

It's this kind of performance we want to bring to Arx.

This performance is also quite unlike the convention in subwoofers (I'll talk about this later) which is to dial in large amounts of bass boost to reach 20Hz, meaning in effect to dial in a lot of time error and phase shift.

Here's the design's delay response. Note the linearity all the way through the woofer's bandwidth.

woofer delay.JPG

Response like this is not common from either small conventional woofers or from inexpensive products. Most "cheap" subs sound like cheap subs because of the emphasis on loudness and boosting the lowest register(s) to make a numerical specification.

This design is truly musical and I think we'll find it quite unusual in that way.

More to come...

[Jon Lane]

[reserved for more content]

[D'Argo]

Sounds good, Jon. Will this sub have an external amp or a plate amp? Not sure if that's what you meant by having a modular design. Also, how does this design compare to the Asub? Did the Asub have the same size driver as well? I'm interested to hear more.

[Jon Lane]

Sounds good, Jon. Will this sub have an external amp or a plate amp? Not sure if that's what you meant by having a modular design. Also, how does this design compare to the Asub? Did the Asub have the same size driver as well? I'm interested to hear more.

It's self-powered with an internal plate amplifier.

By "modular" I mean in the systems sense: The single sub is compact enough, goes deep enough, and is affordable enough to form a strong case for using multiples for larger and larger systems. I don't think I've seen a design in this design, output, and price class that can do what it can do.

The Acculine ASub was a great little sub but this model, like Arx in general, goes well beyond. At least double the excursion and all that linear output down low are attributes the original didn't have.

[Bandg]

I am saving up for a pair of A5's and a sub. Can't wait!! Sounds (pun intended) like it will be worth my patience. Best, Bradley

[D'Argo]

Although my current sub integrates well with my A1s and A2 (it sounds like one integrated system to me), I noticed lately that for some music tracks, the sub seems out-of-sync with the A1s and A2. There seems to be a small delay with regards to the "peak" bass coming from the sub. Not sure if this is "overhang" or "my sub can't keep up with the Arx SplitGap midwoofers." I have my A1s and A2 on full range and my sub integrated at 80 Hz. Sorry for the noob question. Can this be corrected or do I need to purchase a new sub (such as the one Jon is developing above)? Thank you for your help.

[gtpsuper24]

I would not run the Arx full range. I keep mine at 60hrz with the subwoofer at 60hrz. Works great, blends really well, no boomyness or overhang. The Arx woofers are great drivers but they can only do so much below 50-60hrz, running them full range isn't getting you much if any output below their tuning freq. I've found that running mains with a really low crossover plus running the subwoofer gives it a bloated sound.

Overhang isn't from a crossover setting or from the subwoofer its self its usually a room problem. Usually called decay, fixed with something like the Anti Mode 8033 and/or acoustic treatments. The wall right behind the listening postion can cause decay especially if theres a window behind the LP.

Try 60hrz on the Arx and 60hrz on the subwoofer. That lets the Arx handle the midbass, which is were the impact is like drum kicks in the 60-100hrz range and have the sub do the deep stuff 60hrz and lower. Play around with subwoofer placement and look into getting a SPL meter, pc sound card and free REW software, it will show you whats going on at the LP. Nulls, peaks, decay ect... A new subwoofer isn't going to overcome bad placement, bad LP location, or bad room acoustics.

[D'Argo]

Thank you, gtpsuper24. I tried the suggested crossover setting and the sound improved. I will do more listening to see if I experience the same problem. Note that the sub I'm currently using is still from my HTIB (that's why I initially thought that the SplitGaps were faster than the sub driver).

[marksman]

Hello. Ordering my A5's today to replace JBL 830 mains. But, need some education on subs. I currently have 2 Yamaha YST 515s which I acquired at a complete steal for $225 apiece. I'm quite happy with what I paid. I do know what sizzle and boom can be though. One crazy ex ago back in the 1990s I had a Sunfire sub and some bright Boston Acoustics. The YSTs definitely don't boom like the Sunfire did but I'm not looking to recreate that system's sound.

So back to the YST's - I've debated replacing them with everything from SVS to Outlaw to Rythmik, and finally settled on Rythmik for musicality/tonality (until finding Arx). So, here is the YST 515 - the 4th page of this review has response curves:

http://www.scribd.com/doc/68631996/Y...-Review-Lo-Res

I understand this at a rudimentary level, but I don't know how the YST stacks up in terms of quality for music or HT. It seems to me that the YST starts to roll off around 37hz and really stall at 26hz. From what I'm reading most modern subs will go much lower, but I don't think much music goes lower than 50hz. (am I wrong? What's a string bass go to?) So with this all in mind:

1. How would the Arx Asub10 compare to this YST?
2. Are the differences musically useful, or mainly HT?
3. How would the Asub10 compare to this:

http://www.rythmikaudio.com/F15HP.html

I have trouble telling the difference to the YST aside from power since the response graphs look like they use a different x-axis. Though I can clearly hear a difference.

Feel free to simply post more links to info I can read & learn. Using the YST as my known baseline I've tried googling around but can't find any comparative info. It's been 12 years or more since I had that Sunfire cube, so I don't really remember how musical it was. Not to mention I was younger and tended to listen to some noisier, less musical types of music than today.

Any input appreciated,