Bose PA

Here is the current situation as of 3/23 on the Bose PA system I've been using.

Context
When I was playing multiple shows weekly on keyboard and sax with full-spectrum backing tracks, the main complaint I would always receive was that my overall volume was too high. In an effort to produce well-distributed sound at as low a volume as possible, I tried a number of different PA solutions for the small-to-medium rooms I typically play.

One option was the QSC K12, but I felt this speaker optimized more for very loud volume than overall sound quality and dispersion. I had very suboptimal results with a pair of Fishman SA220's due to the noisy amps and electrical failures combined with mediocre tuning. I decided it was time to bite the bullet and go Bose. I purchased a Bose L1 Model I and 2 B1 Bass Modules.



The L1 System
The L1 System garnered some compliments in larger rooms. However, the L1 is bulky, vastly overpowered for all of the gigs I play and it represents a somewhat significant capital investment which goes largely unutilized. The main concern about the L1, though, is the age. These units are made with low-quality components and are prone to many types of electrical failures within the Power Stand, the large and heavy base for the line array that houses all of the electronics for the system. When I have my reputation riding on my gear, I don't want to question whether it will die when I need it most, or worse, emit erratic sounds at high volume that could hurt people's hearing.

One solution to this problem would be to purchase the new Bose L1 systems, which I know are better both at dispersion and overall sound quality. However, those are even more expensive than my current system and equally as overpowered.

The Bose S1
Over the years, I've accumulated 2 Bose S1's. These are solidly built, pleasingly-tuned and extremely portable speakers. Even a single one of these speakers provides more than enough volume than is typically required for the type of gig I play. Having 2 allows for use of stereo keyboard sounds, even though the Nord does a better job than other keyboards at folding down its sounds to mono.

I decided to unload the L1 system, reclaim that capital and instead depend upon the new S1's for my gigs, which are much rarer now than when I first purchased the L1. However, there are a few trade-offs that need to be addressed.



The two main issues with this plan are dispersion and bass.

Dispersion
The Bose S1 has a coaxial design with a somewhat articulated array of tweeters mounted in front of a larger woofer. The articulation of the array assists in dispersion, however, I feel having 2 S1's is really what will cover the room. Plus, having two smaller more directional speakers will perhaps not be as good as a single highly-articulated line array for reducing overall system volume but is definitely better than 1 speaker.

Frequency Response
Due to extremely aggressive tuning from the factory, the S1's deliver the "pretty good on everything" sound Bose is known for. A large component of this sonic signature is an extreme boost to the bass. Not only is a bass boost part of the Bose sound signature, but the S1's bass response is clearly being aggressively tuned from the factory to compensate for the small size of the speaker.

I play music that benefits from natural low-end reproduction rather than boosted or loud performance of these frequencies. Despite this tuning, I feel the S1's will still lack behind the L1 system when it comes to deep, if not loud, bass reproduction.

Supplementing the S1's Bass Response
Bose sells a Sub1 which is "designed" to provide additional low-end for the S1's. I put quotes around "designed" because while the Sub1 includes an S1 mode, I've heard reports it delivers a sound that isn't quite as organically blended and crossed over as one would expect from a dedicated S1 mode. My guess is that it's just a crossover at 100 or something. Considering that the Sub1 is also $899, I don't think this is a good use of funds.

Third-Party Subs
After looking into currently-available options from reputable, reliable vendors, I didn't find any small subs that were compelling for my use case. I recall having these same frustrations when I was a QSC CP8 user - the only sub the vendor offered was far more expensive than the CP8 itself and was extreme overkill for the small CP8.

The Bose B1 Modules
When selling my L1 system, I realized that the B1 modules did not add much value to the selling price. I had an idea: what if I retained the 2 B1 modules for use with the S1's? That could solve the bass problem and perhaps take some of the low-frequency signal off of the hands of the S1's.

However, it's not as though one can just connect line-level audio to the B1 modules. For one thing, they're passive. And for another, they're proprietarily customized to work with the L1.



Optimization and Protection of the B1 Bass Modules
Based on my research, the L1 Power Stand not only powers the B1 modules but it also "optimizes" them. Per Bose's wiki, these optimizations are threefold.


 * 1) Protect B1's from frequencies they're not designed to handle
 * 2) Optimize the frequency response of the B1's
 * 3) Tone-balance the L1 system as a whole by detecting how many Bass Modules are connected and adjusting the bass output level and crossing over the line array accordingly.

It occurred to me that given the age of the L1 system, they likely wouldn't have been doing particularly advanced or dynamic processing on the B1's. I surmised it would boil down to level control, the application of a static EQ curve and perhaps some overall level limiting, though I think this would more happen on a system level.

If in fact this signal processing was as basic as I speculated, it could be easily measured and modeled for use without the L1 Power Stand.

Let's take each of the 3 items above in order.

B1 Protection
I was concerned when I read that the L1 Power Stand provides "protection" for the B1 modules. I don't want to use, much less depend on an "unprotected" speaker.

However, I looked closer at the Bose engineer's wording. They stated that the Power Stand "protects the B1 from frequencies it wasn't designed to handle." It's commonly known that Bose's products use copious amounts of signal processing to get satisfactory performance from otherwise unsuitable components. I also know that applying static but specific EQ curves is well within the scope of what the L1 can do.

And regarding limiting, it seemed most likely to me that the L1 system would be providing system-level limiting upstream of the B1 modules which would reduce the amount of computation required and apply to both the line array and bass output. This feels right up their alley, a way to capitalize on the highly "integrated" and "optimized" nature of the L1 system.

So what if the "protection" here was just:


 * 1) Rolling off the highs and lows that were out of optimal reach of the sub
 * 2) Using an impedance- and power-matched amp?

Perhaps the first can be measured. And against all odds, Bose sells the second as a discrete module. More on this later.

B1 Optimization
It doesn't at all strain credulity that Bose would apply a specific EQ curve to the B1 speaker. It's a relatively unique speaker design, with 2 small drivers each and presumably some sort of complex waveguide behind them. We also know that it isn't beyond the technical abilities of the L1 Power Stand to apply specific static EQ curves to signals given the ToneMatch presets on the inputs. Plus Bose admitted it on their wiki.

If this were a modern product released today, I'd assume some sort of multiband dynamic eq may be in use here. But not for the L1. My money's on a static EQ curve for optimal performance combined with standard system-level limiting.

If we can find a way to measure the EQ curve being applied to the B1's by the Power Stand, we'll have measured the EQ optimization as well as the EQ protections all at once. Absent dynamic EQ or multiband compression, it's just a static curve.

Tone Balancing
We know the L1 system has awareness of how many B1 or B2 models are connected and adjusts their output level as well as the output level of the line array accordingly. Their goal was to simply enable more headroom by connecting bass modules, not to add bass. Preserve the tonal balance. Very cool.

This means we'd need to make efforts ourselves to make the tone balanced between the S1's and the B1's. Doable.

Next Steps
So, we need to find a suitable amp for these speakers, one that is power-and impedance-matched to the drivers and know where the limits are that will hurt the B1's. We also need to find a way to measure the EQ curve the Power Stand is applying to the B1's. And assuming we can do that, we need to tonally balance the system.

Amplifying the B1's
I didn't want to lug a big QSC 2RU amp around just to power the B1's. That would add a lot of heft to the system overall. And I needed an amp that matched the power and impedance specs of the B1.

Against all odds, Bose actually sold a discrete amplifier for the B1's. I couldn't believe it. Known as the Packlite A1, it was intended for adding larger numbers of Bass Modules to the L1 than its internal amplification could handle. While Bose states that the A1 does NOT provide the B1 optimization EQ curve (as this would still have been provided by the Power Stand) it does provide protection functionality and is impedance- and power-matched to the B1 modules.

It's tiny, it's efficient, it's user-friendly and it matches the B1 in output and protection. What a boon.

All that's left is the EQ curve.

Measuring the Power Stand's B1 EQ Curve
In order to capture the curve, we need:
 * a known full-spectrum input (white noise or sweep)
 * the ability to grab the B1-adjusted signal from the L1
 * the ability to isolate the B1-adjusted signal from other nonlinearities

This was going to be complex. Getting a known input into the Power Stand was easy enough, but we needed a way to activate and isolate the B1's adjustment curve. I thought about using hardware to reduce the output of the L1's speaker output to measurable line-level and building a custom connector that contains the right resistor to tell the L1 to apply the curve. But the connector wasn't available and I was concerned this wasn't the cleanest way to measure the output.

I tried measuring the B1 with a mic, thinking that I could amplify the speaker with another amp, level match it, measure the B1's raw output and compare the two curves. However, this introduces non-neglible room factors like nodes. Not great.

Then it dawned on me: in addition to the amplified B1 output, the L1 features a line-level bass output, intended specifically for the A1. And since the A1 doesn't provide the B1's frequency adjustment, the L1 must apply that EQ curve to the A1's output as well. We could trigger the B1's frequency curve by connecting an actual B1 to the amplified out, measure the frequency response, then remove the B1 and measure the un-adjusted frequency response. I couldn't believe the luck -- an isolated adjusted and non-adjusted output to measure, at line level no less, without hacky workarounds.

I used Room EQ Wizard through a MOTU M4, and here's what the B1's curve looks like. (The uncorrected output was unremarkable.)



Basically, it’s getting rid of super low stuff, providing a boost in the "solid" bass region and sloping off anything mid or high.

Not sure where "zero" is on this. The "boost" may not actually be a boost -- everything else could be just cut more. The curve is what matters.

But this curve can easily be replicated using any parametric eq on a digital mixer. And while applying this curve, we could tonally balance and "tune" the crossover point and tonal balance of the system. Awesome.

Suitable Digital Mixers
The main requirements here are:
 * ability to apply different arbitrary parametric EQ's to an aux send as well as mains
 * dependable build quality and reliability
 * ability to control volume and mix while playing
 * not expensive

Nice-to haves would be:
 * 3 XLR outs (would rather run all speaker signals via XLR)
 * some sub-specific functionality, like mix linking from master to sub aux or easy crossover functionality
 * hardware controls I can use while playing
 * single volume control I can use for subs and tops at once

The two digital mixers I found for this are the Soundcraft Ui12 ($275 open box ProAudioStar) or the Behringer Flow 8 ($300 new Sweetwater). They each have their tradeoffs.

The Soundcraft Ui12
The Ui12 has solid build quality and USB stick stereo recording but has terrible built-in networking and virtually no local controls. It also is known to have some broader system quality issues like noisy preamps etc, though it does come highly recommended from a professional contact, and frankly I doubt it will have any significant issues, particularly if I use an external access point. Beseda.us/uimixer also offers a midi control app.

The Behringer Flow 8
The Flow 8 has local controls which are very reassuring and easy to adjust as a performer and includes multitracking over USB, giving it a ton more potential usability when I’m not playing shows. This reduces the stagnant resources I have tied up in live-only gear.

However, it has much worse build quality, an incredibly flimsy micro-usb for power and no usb stick compatibility. The micro-usb would likely have to be replicated via a back-mounted pigtail or something to reduce wear. And not wildly promising for a mixer being amplified many times over by hearing-damage-capable mains to be powered from a single USB power wall wart.

That said, it appears to have all relevant features as long as mon send 1 can either receive the mains mix or something. Stereo mains and mono aux send to sub is something we’d still need to work out.

Next Steps
I don't love either of these options. The Soundcraft lacks hardware controls and the sub-specific feature and the reliability of it's larger cousins. And it's kind of big. And I'm already worried about reliability of the Flow 8.

Either way, $300 isn’t a negligible sum and I’m planning to purchase one of these two options when I have an actual gig that requires it.

I will retain the B1’s and A1 which don’t command much resale value and don’t represent a massive liquidity limitation for me. For every other gig I’ll use either 1 or 2 S1’s and I will be totally fine with them, though I may need to purchase stands for the S1's. I don't think the B1's are stable enough to elevate the S1's through some sort of modded sub pole.

Crossovers
I did get a chance to play around with tonal and volume balance of the B1 and S1's. I was able to separately process the mains and sub outputs through my DAW and the MOTU M4. Here's what my experimenting has shown.

The B1’s, when optimized and protected, can produce substantial amounts of bass. Deeper than the S1's by an octave or so, though more "natural" or "musical" than "thundering". The thing is, I was also quite surprised at how little the B1's enhanced the existing performance of the S1's. In other words, in a setting where I could independently balance in and out the B1's, I found the (calibrated) B1's brought surprisingly little benefit given how good the S1's were. There's definitely a noticeable increase in the depth of the bass response when the B1's are in the picture, but the S1's are really quite good on their own. The woofer in EACH S1 is actually larger than the drivers in the B1's. Sure, the B1's have two each, plus waveguides and powerful independent amplification, but driver area is roughly equivalent.

Integrating the B1's with the S1's
The S1's were actually good enough on their own to convince me that for most gigs, the subs won't be necessary. But in the event they are, there are a few different integration paradigms we could use.

One option would be to treat the system like the L1 system -- remove all bass from the S1 and roll off everything below 100 to the subs. This doesn’t feel necessary to me. Frankly it feels a bit disjointed, reminding me of the criticism of the Sub1. But this would only be used for larger rooms if those ever became part of my work, and in those settings differing points of origin for low and high sound is much less critical.

Another approach would be to apply the measured curve to the B1 aux send and then use a low-end shelving EQ on the mains to reduce the bass output by roughly however much the subs are adding in order to keep the tonal balance roughly correct. This could require some future calibration with an RTA and measurement mic. I think some frequency overlap is OK in this case because a discrete “top/bottom” approach doesn’t really sound right. And the S1 sounds quite good on its own. So the goal is to add low end extension below the S1’s sweet spot.