Bass Management System Development

**Sonnie** · **02-13-07, 02:09 PM**

I just don't think Firewire from the unit to the sub or sub amp is gonna fly. 100% of the subwoofers on the market today have analog inputs, 0% have digital inputs that I know of... you are going to introduce a product that in order to be functional, will immediately require a D/A converter and I don't see that being cheap if it's done right.

I don't see it working like you want it to. I don't know, maybe I'm missing something... maybe some others can chime in again with their thoughts.

**bvwj** · **02-13-07, 02:36 PM**

Thanks for hanging in there with me and not just giving up. I appreciate it.

Here is my point on A/D - D/A. All digital parametric equalizer systems all require an A/D and a D/A. My proposal is no different. For a given quality level my A/Ds and D/As cost about the same as other solutions. The only difference is where the D/A is located. I propose locating it near the speaker to gain the quality and cost advantages of digital signal transmission over analog signal transmission.

I don't think it would cost much more. It would cost less than analog Monster Cable and would be higher quality. (I know many solutions are better and less expensive than Monster Cable.

)

If you liked this system but really wanted to run analog to the speakers, you could locate the D/A modules near your rack and run analog signals. No skin off my back. Nothing says the digital interconnect needs to be long, it just can be if you want.

I'm guessing you still might have other issues regarding this type system. Or I could still be missing your point. Please help me out. Understanding these issues can either improve my proposal or help me avoid a huge mistake.

**Otto** · **02-13-07, 02:48 PM**

Would the D/A be included as part of your device? i.e., a separate box, but still a complete solution? If we have to buy a separate D/A it's more confusing. If you sell a complete solution, including the "main" box, a cable of whatever length, and the D/A box, that might be more appealing. We can then make or buy a longer/shorter cable as desired.

**Sonnie** · **02-13-07, 02:57 PM**

I'm not up for more boxes... I have enough now. I prefer a one box solution. I could be wrong, but I think most people will want a one box solution... that was our initial goal. I'm still not sold on Firewire from the unit to the sub and I don't think it will sell very well... sorry....

**bvwj** · **02-13-07, 02:57 PM**

Yes the intention is to supply a complete solution to integrate into todays analog world.

Sorry I wasn't clear on that.

I got off track discussing optional D/As or A/Ds that could be attached to the system if the standard I/O wasn't up to the requirements of the highest end customers.

I am considering a prototype that would rely on a separate, currently available D/A A/D box. It would be faster to get the platform going for software development without worrying about the analog bits up front. I doubt that prototype system would be available commercially.

**bvwj** · **02-13-07, 03:03 PM**

Sonnie,

I appreciate fewer boxes. My concept for the D/A is a mouse sized box that could literally hang of the RCA or XLR connector to the sub amp, not another rack sized piece of equipment.

Can you expand on your concerns about firewire to the sub?

**Otto** · **02-13-07, 03:12 PM**

Quote:

bvwj wrote:

I got off track discussing optional D/As or A/Ds that could be attached to the system if the standard I/O wasn't up to the requirements of the highest end customers.

So would the "main" box have an analog output (preferably balanced). And then also a firewire output for those that wish to use an external DAC?

**Sonnie** · **02-13-07, 03:26 PM**

Quote:

bvwj wrote:

Sonnie,

I appreciate fewer boxes. My concept for the D/A is a mouse sized box that could literally hang of the RCA or XLR connector to the sub amp, not another rack sized piece of equipment.

Can you expand on your concerns about firewire to the sub?

The extra box is my concern... if it's small enough, then maybe it will work okay, but I didn't think DAC done right was cheap... is this not a concern? I've always heard of DACs costing at least a few hundred dollars... has it gotten that inexpensive now?

It's got to convert back to analog anyway, what is the benefit of it going an extra meter to the sub in the digital domain? Seems like to me the easiest solution is to put the DAC in the unit/box and let us use our analog cables out to the sub.

**bvwj** · **02-13-07, 05:59 PM**

I agree, the DAC box at the speaker must be small to be a workable solution.

DAC's run from cheap to very expensive. The currently available $125 equalizers have 2 ADCs and 2 DACs inside, so they don't necessarily have to be expensive. The ones on the available equalizer also have to respond up to 20kHz. A dedicated sub DAC could focus on higher quality at lower frequency and possibly end up even less expensive.

It does all go back to analog. For 1 meter the benefit is small. In my theater, the run is closer to 10 meters and goes past or runs along with power lines, video cables, and other analog speaker cables. That's a lot to expect from an unbalanced line level signal. I would much prefer a digital interconnect.

Ground loops of which I'm sure you have experienced are another analog issue that is quickly forgotten after moving to DC isolated digital interconnects.

I'm working on a modular approach for the main system unit. It is possible that an analog output could be added to the main unit. (You're wearing me down

)

Is anyone but me attracted to the benefits of "digital to the speaker"?

**oyo** · **02-13-07, 08:49 PM**

I thought I would jump in here...

I like the idea of digital to the speaker. If I sit on the side of the room with the my current analog sub cable, my Blackberry phone induces a loud digital sounding buzz.

The new processor sounds like a great idea to me. Adding basic RTA/Mic preamp functionality if it doesn't add to the cost would give non REW folks a chance to get their systems tuned fairly well with just the puchase of a mic and cable.

Several studio monitor companies use a built-in RTA/filter bank (Genelec and JBL come to mind) to flatten the response of their speakers. Your proposed system could put flat sub response in the reach of non-tech types if it had an automatic self-adusting mode.

Take this for what it is worth- I'm just throwing out ideas here.

Thanks for looking at bass management!

**blekenbleu** · **02-18-07, 12:41 PM**

Quote:

bvwj wrote:

In my theater, the run is closer to 10 meters and goes past or runs along with power lines, video cables, and other analog speaker cables. That's a lot to expect from an unbalanced line level signal. I would much prefer a digital interconnect.

Ground loops of which I'm sure you have experienced are another analog issue that is quickly forgotten after moving to DC isolated digital interconnects.

I'm working on a modular approach for the main system unit. It is possible that an analog output could be added to the main unit. (You're wearing me down

)

Is anyone but me attracted to the benefits of "digital to the speaker"?

I'm interested, but prefer optical; don't need any more stinkin' RFI.
DC isolation is huge for me, but then presumably need batteries or wall warts for DAC dongles..
It would be neat to automagically adjust phases, delays, levels and frequency responses based on PC software
that sorts out which of daisy-chained dongle-attached subs are best positioned to accommodate various room modes.

**DrWho** · **02-20-07, 06:12 PM**

I'm vote adamently against putting a dac at the subwoofer end of the wire. It's completely pointless and prone to all sorts of other issues. You do realize that you're going to need to send a DC voltage down the line to power the output stage of the DAC right?

**bvwj** · **02-20-07, 07:13 PM**

Optical interconnect is a possibility, there exist optical solutions for 1394. It would be more expensive thus probably an option if sufficient demand develops.

The 1394 signal is differential, kind of balanced, so it doesn't emit much EMI. It's also scrambled to avoid harmonic re-enforcement, and doesn't allow long runs of highs or lows. The signaling frequency is 62.5, 125, 250, or 500 Mhz. Well above anything in the audio bands.

The point of putting the DAC at the end of the wire is eliminating analog interconnect issues. Perhaps you have seen vendors trying to solve this issue with $500+ cables, spent a day killing a ground loop hum, or picked up noise from a halogen lamp dimmer.

I don't think I would run DC across the digital interface. You can run AC across cat5, but its complicated (expensive). I'm proposing an AC to DC converter at the DAC. The sub amp needs AC, so I would expect it to exist in the vicinity.

I don't get the analog devotion, perhaps you can help me understand. If you're a vinyl or tape lover more power to you, but most of us in home theater are left with audio entering our systems from DVDs, MPEG2, or MPEG4 digital streams.

So there you are. For my purposes it all starts digital. On the other end, it's becoming more and more digital all the time. Class D amplifiers may not be audiophile yet, but they are getting better and they require a digital input. The BASH amplifier in my Sub woofer is already half digital.

A signal can't be improved with a D/A or an A/D so the fewer the better. An analog signal can only get worse running down a long cable, it can't be improved. The shorter the analog cables the better. A proper digital signal is the same at the end of a 1' cable as it is at the end of a 300' cable.

If a D/A is necessary, and today it is, it can provide the highest quality closest to the destination.

There are frequently holes in my reasoning, feel free to point them out. I'm starting to think that because current parametric equalizers have analog ins and outs, it's been easy to ignore the fact that they contain 2 ADCs and 2 DACs. Since the current system costs <$150 it becomes obvious that they probably aren't audiophile ADCs and DACs. Now that I'm proposing separating them from the main unit, there is a little more daylight shed on the issue and people are demanding higher quality DACs. That could definitely be a perceptual problem with my concept. (Or an opportunity.)

Thanks again for all the input.

Barry

**Sonnie** · **02-20-07, 07:35 PM**

I don't really understand DACs, but it sounds like you are saying that we will have to power up the DAC at the end of the cable run to the sub... meaning this unit will require two AC outlets? I think this is going to be a drawback.

In situations like mine, I use a split output to my two subs from the 1124P. One is about 4' in length and the other is about 9'. Do they make a Firewire that will Y-split into two? Then I have to have 3 available AC outlets, actually 4 because I'm about to add a third sub.

**DrWho** · **02-20-07, 10:49 PM**

Quote:

The point of putting the DAC at the end of the wire is eliminating analog interconnect issues.

What specifically are these interconnect issues? You first have to identify the problem before offering a solution...especially a "solution" that is going to introduce other problems.

For what it's worth, you're not going to revolutionize the entire audio industry with this product. If you want to make money, then perhaps you should operate within the existing framework and tailor to the target market? Everyone here is already running an analog connection between their receiver and subwoofer without issue. There is absolutely no need to "fix" a problem that doesn't exist.

For what it's worth, it has absolutely nothing to do with a devotion to analog - quite the contrary actually.

Quote:

Since the current system costs <$150 it becomes obvious that they probably aren't audiophile ADCs and DACs.

Audiophile? If our source material is going through the same devices in the studio, then surely it must be good enough for playback at home. Semi-conductor based chips have also dramatically gone down in price as the manufacturing process has improved. A $50 transistor 15 years ago is now only costing $0.50...price really shouldn't be a determination of quality.

What ever happened to the notion of objective data? You know, actually measuring the performance of the various stages? The overall quality of a device certainly isn't going to be determined by the DACs alone..., isn't the reason we're all here because we realize the benefits of objective data as it pertains to tweaking the sound of our systems?

**LightwaveDude** · **02-21-07, 11:01 PM**

My $.02:

The issue over firewire vs. USB isn't a big deal to me. If you want firewire for your product, go with it. While USB would be nice, I can see where you don't want to develop it for your product. , for my 1124P, I'm going to need to buy a USB to midi or a midi controller card to hook it up to my computer, so I don't see why a firewire card would be so bad (especially considering how much more useful firewire is than a midi card). So go with the firewire.

On the issue of the digital signal to the subs: I think it's a good goal and it sounds great in theory, but I don't see it working in the near future. I see the advantages, but I also have to look at my system, and I just see it being easier to use what I have which is analog RCA. If you really want to add your digital output to a D/A box by the sub, here's my suggestion:

Make the D/A box much like an iPod with a bay station. Make it small and give it a port or a cavity to plug into on the back of the unit which gives people like me, who want to keep everything in a stereo cabinet or rack, the ability to leave it all there and just run the signal a foot to an amplifier nearby. (I have a passive sub and so the distance to the sub is run by the actual power conducting speaker wire). Then, if you want to run a digital signal to your powered sub digitally as you suggest, unplug the D/A box from the back of the unit and run a signal wire to the sub.

The biggest problem I see with this is it requires custom chassis with a cavity for the D/A unit to slide into, which I can foresee increasing the price slightly (to what degree, I don't know).

This I see as a compromise between those of us who want the analog RCA outputs on the unit itself (without extra boxes in a sense) and the people who want the D/A located close to the subwoofer.

Edit: spelling and grammar

**bvwj** · **02-22-07, 12:28 PM**

Sonnie,

It sounds like your system is my target market. If I can't convince you I might not have a market!

Yes, requiring more AC outlets is a downside. If the other upsides can't overcome that downside then I have a problem. In my system it would be simple to add a "power splitter" at the power input to my sub to provide the extra outlet. I understand everyone's implementation is different.

You can't normally split a FireWire (or USB, or Ethernet) signal. You can use a hub to offer more outlets. You can "daisy chain" firewire, that means running a single cable from one point to the next. Each FireWire device can also be a hub.

On the upside, I think independent three channel time delay, phase adjustment, and crossover would be ideal for a 3 sub system. Just splitting the same signal to three subs doesn't seem to maximize the potential of a 3 sub woofer system. A single firewire cable can carry dozens of audio streams. The DAC at the speaker just has to be smart enough to pick out the correct one.

I know it would be crazy for an unknown company to try to move the home theater audio market to digital interconnect. Fortunately, that's not what I'm trying to do. I expect that transition to take place by itself. I think digital to the speaker is inevitable. It took decades for sources to become digital. It took years for it to happen between the source player and the receiver. It will take less time for it to spread to the speaker.

I just want the transition to use my technology. I'm not alone. HANA (the High Definition Audio Video Network Alliance) demonstrated a FireWire sub woofer at the last CES. HANA is led by Samsung, JVC, Mitsubishi, Texas Instruments and others.

I'd like to develop and market a product that fits into today's systems that demonstrates and paves the technology path to future systems.

That's what I'm up to. But I still might be crazy.

Barry

**Sonnie** · **02-22-07, 12:34 PM**

Well, you see what myself and others are saying. Personally I think we are after something different than what you can offer, unless you are willing to reconsider your design. If you can get away from this digital to sub idea and just stick with Firewire for computer connectivity, then your product will be much more appealing. I just don't know what else to tell ya.

**bvwj** · **02-26-07, 11:48 PM**

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