Bass Management System Development

Last week I posted my responses to a list of requirements for a dedicated home theater bass management system. My company has some interest in developing this sort of system.

There was some interest, so it seems like the next step is to start a thread to discuss it in more depth. Here we go.

These are the requirements I listed last week:

~ Two independent channels.
Fine. Two independent inputs. How many independent outputs (in your wildest dreams)
~ A minimum of twelve parametric filters per channel (20 per channel is good too).
Fine. Only practicale limitation is processing artifacts and delays of multiple filters. Modern DSP's can handle this easily.
~ Channel coupling and series looping.
Probably not. All digital filtering can be accomplished in one pass at higher quality than two passes.
~ Three-way IN/OUT bypass.
Probably no analog bypass because we don't have analog outputs from the controller. Digital filters can certainly be cut in and out.
~ Input/output LED level indicators.
Definitely indicators on PC interface, possibly on front panel.
~ LED filter indicators for both channels.
Probably not.
~ Front panel display.
Very limited
~ Retain normal required buttons and jog dial.
Probably not, possible IR remote capability
~ 24-bit/96 kHz A/D and D/A converter powered by a 32-bit DSP.
Surely possible, although there needs to be a discussion on the recommended sampling rate for <250Hz signals.
~ Internal switch-mode power supply (100 - 240 V~ / 50-60hz).
Probably wall wart power supply with internal regulation.
~ Low power consumption.
Sure.
~ Adjustable input level (-10dBV / +4dBu) on rear.
Consumer line-level unbalanced input. Is more really required for a home theater box?
~ Hard bypass relay.
No.
~ Noise-free.
No fan.
~ 107db dynamic range.~ 0.007% THD.
On inputs and outputs.
~ High-quality components.~ High-quality construction.
Given
~ Balanced XLR inputs/outputs.
Required for home theater?
~ Soft power ON/OFF with selectable Auto-On detect via sub signal.
Probably
~ Eliminate turn-on thump and ground hum.
Sure, the digital interface will eliminate ground hum potential. The DSP can be responsible for pops.
~ Double insulated chassis with a two prong plug or a ground lift switch if needed to eliminate hum.
The external power supply will provide isolated 2 terminal power
~ Pure flat frequency response from 10hz to 20khz* (FBQ2496 is -3db @ 20hz).
Yes
~ Filter adjustment capabilities from 10hz to 20khz*.
Yes to below 20Hz (probably not to 20kHz as the system concept is for sub woofers).
~ Adjustable gain range from -24db to +16db for each filter.
Yes
~ Minimum of 4 to 6 memory presets.
Yes
~ Replace ¼ inch inputs/outputs with RCA inputs/outputs.
Yes
~ Simple shelf filter… (i.e. selectable linear boost between two selectable frequencies).
Yes
~ Selectable and/or variable 6db-48db/octave subsonic roll-off filter from 35hz to 10hz (minimum 5hz increments).
Yes
~ Time delay from 0 to 30msec or 1 foot increments w/ 0.1 foot fine up to 30 feet.
Yes, independent for each output, is 30 feet enough?
~ Variable phase correction/adjustment from 0-180.
Yes
~ Front panel USB and/or RS-232 interface for MIDI port (place under small flip cover like on computers).
1394
~ Dimmable front panel LED's / lights with OFF option.
Off option for free.
~ Soft blue and/or green LED's on front panel vs. red.
few LEDs
~ Offer unit in black or silver… if not optional, offer only in black.
black
~ Revamp chassis for home theater consumer appearance vs. pro-audio style.
~ Allow mounting brackets to be optional (include unattached).
~ Enclose/fill gaps on sides if mounting brackets are removed.
~ Add rubber feet to allow placement on top of other equipment.
~ Remove graphic design from top of unit.
home theater friendly
~ One year warranty.
certainly
~ Anti-clipping mechanism with higher dynamic peak input before clipping.
24 bit dynamic range may have to do. Clipping indication available.
~ Frequency readout in hertz instead of base + fine… (1hz increments w/ 0.1hz fine increments).
Yes, on PC application.
~ Bandwidth readout in octaves (1/3,1/6,1/24,1/1, etc.) or hertz (2hz,5hz,12hz,etc.) instead of 1/60, 10/60, 60/60, etc.
Yes, on PC application, ideally notation will agree with REW.
~ Front panel volume/gain to control output level to sub.
Probably not, possibly available over IR control.
~ Ability to slave multiple units together.
Unlikely, hopefully it wouldn't be necessary. Can you describe the need?
~ Linkwitz transform circuit.
Can't this be done with a digital filter? Looks like a shelf filter.
~ Detachable power cord.
Yes, wall wart.
~ Individual crossover filters (Butterworth, Bessel, Linkwitz-Riley) per channel w/ selectable roll-off 6db-48db/octave.
Digital crossover filters?
~ Adjustable/variable crossover range (low pass and high pass from 20hz to 200hz and w/ bypass).
Yes, if digital filters are acceptable
~ Built-in RTA mic/line input w/ phantom power and w/ GAIN control.
Yes, this would be XLR?
~ Built-in SPL meter with selectable dBA/dBC/OFF weighting.
Digital
~ Built-in test tones (sine waves - individual 1hz increments and sweep from 5hz to 400hz or 5hz to 20khz).
Yes
~ Separate RCA mic monitoring and test tone output to allow for computer program monitoring.
Don't quite understand, certainly computer program monitoring is a priority.
~ Locate RTA mic/line inputs and RCA monitoring outputs on the front face plate under a small flip cover.
possibly
~ Video output for monitoring the display would be nice, but the cost factor may prohibit this.
Display on computer connected via 1394.
~ Video display instead of LED's… (dimmable and selectable OFF).
no, but graphically rich PC interface available
~ Small and simple 6 button wireless IR remote with discrete ON/OFF buttons and Preset 1,2,3,4 buttons.
IR control could replace many front panel buttons, and interface with home theater control systems.
~ Rear IR jack for remote control… to use with repeaters.
Yes
~ Add volume/gain control button to remote if feature is made available.
More likely on remote than on front panel
~ Add other control buttons to remote if cost feasible.
Given IR control, more buttons is not a cost issue. We probably wouldn't include a remote, more likely to offer a configurations for Harmony and other programmable remotes. I know my theater doesn't need another remote!


I can't commit to this product yet, but feedback would definatly help define a possible product and validate the potential market, both useful in our business case development.

Barry

I was unaware of using professional amplifiers for DIY subwoofers. That makes sense. I would expect to provide a different output module with XLR connections if there was a demand. Keeping the unbalanced output module inexpensive is a priority.

Is there a similar situation for source signals on XLR? I assumed most dolby decoder type boxes would be unbalanced.

Barry

In the interest of full disclosure I work with Quantum Parametrics.
To date we have exclusivly produced 1394 test equipment. As I mentioned previously, we are introducing a new 1394 protocol standard and are looking for demonstration product applications.

Initially the bass management system seems a good fit both in technology, complexity, and market size.

It's much too soon to say how or if or who might produce this product. I'm just saying I'm interested in discussing it.

[Sonnie]

Hopefully we can get some worthy discussion for you... I know we all have the desire to see a unit produced that will fit our needs better than what is being offered at this time.

[brucek]

I would expect to provide a different output module with XLR connections if there was a demand. Keeping the unbalanced output module inexpensive is a priority.

Is there a similar situation for source signals on XLR? I assumed most dolby decoder type boxes would be unbalanced.

I don't know what you mean by dolby decoder type boxes.

The unit has to be able to accept both unbalanced and balanced inputs to the two channels. The input to the device will be fed line level signals from home theater processors, receivers, preamps that have low output impedance (usually less than 100 ohms). The device has to have high input impedance that accepts a switchable range of levels since there are two quasi standards in the industry (-10dBV and +4dBu).

The balanced connections can be TRS or XLR and the unbalanced RCA type.

The output of the device (low output impedance) will be feeding subwoofers with their own amplifiers, or DIY subwoofers with external amplifiers (high input impedance devices). Some of these devices accept balanced and some unbalanced. Again the levels usually conform to one of the two standards.

Here's an FBQ2496 from Behringer.
You can download its PDF and look at the specs etc.

Here's the type of specs we would be looking for. (except most people would want the unbalanced connection as an RCA rather than an auto detect TS jack..



brucek

Thanks for the input. I'm warming to your position, but I'm not quite there yet .

The cost goal is going to be difficult to meet. XLR connectors alone can cost $5 each. My estimate is 95% of the customers for this device wouldn't use any XLR inputs (feel free to make a better estimate). That means the system would cost at least an extra $25 for something that wouldn't add any value to 95% of the customers. On the other hand, an XLR for a calibration mic could possibly add value to 95% of the customers.

On the bright side is the flexibility of the Firewire architecture of this proposed system. I consider it the true professional audio interface. If a high end customer saw value in implementing a balanced input to the system he could attach another device like a M-Audio Solo or Miglia HA02 ($120 or less). These devices could digitize the balanced signals in a very high quality manner and pass them to the bass management device. I think the Miglia even does the soft clipping you were interested in. If this really turned out to be a popular option for the system, we could develop simple lower cost devices to perform this same function. The Miglia and M-Audio devices include many other functions.

A customer could presumably gang as many of these devices as necessary to satisfy all his input requirements. The memory in the main system would select the appropriate input for each setup. In my future dream world, all the source devices are providing digital streams over Firewire and no converters are necessary until the amplifier.

All this flexibility comes nearly free with this system architecture. The main unit stays as low cost as possible with 2 unbalanced inputs that add value for 99% of the customers. Even most of the XLR users will likely have an unbalanced device they want to hook up.

I'm still open to the probability I'm missing something. Please feel free to correct any of my assumptions. I appreciate you sharing your experience and I'm willing to adjust to compelling arguments.

Is this really the only issue you find on the list of requirements? I can't imagine it's so close to ideal on the first pass! Would you like to discuss DSP options?

Barry

[Sonnie]

Personally I would not be offended it it did not have XLR inputs/outputs. There is quite a lot of fine equipment out there that doesn't have XLR and generally they will all have RCA... plus we are talking sub frequencies, so I don't see it being a make or break issue myself, but I could be missing something.

Thus far let's consider the features on the list you object or somewhat object to:

~ Channel coupling and series looping.
Probably not. All digital filtering can be accomplished in one pass at higher quality than two passes.

~ Three-way IN/OUT bypass.
Probably no analog bypass because we don't have analog outputs from the controller. Digital filters can certainly be cut in and out.

~ LED filter indicators for both channels.
Probably not.

~ Retain normal required buttons and jog dial.
Probably not, possible IR remote capability

~ Front panel display.
Very limited

~ Hard bypass relay.
No.

~ Front panel volume/gain to control output level to sub.
Probably not, possibly available over IR control.

~ Linkwitz transform circuit.
Can't this be done with a digital filter? Looks like a shelf filter.

~ Separate RCA mic monitoring and test tone output to allow for computer program monitoring.
Don't quite understand, certainly computer program monitoring is a priority.


These are really all we need to discuss.

[Sonnie]

~ Channel coupling and series looping.
Probably not. All digital filtering can be accomplished in one pass at higher quality than two passes.

This probably isn't a big deal. I don't really understand the digital limitations of looping one channel to the next for double the filters, but with a dozen filters per channel, I think most everyone would be satisfied.

If I'm remembering correctly, coupling simply allows both sets of channel filters to be input simultaneously. With REW automatically loading the filters into either channel, I don't see this as a major loss.


~ Three-way IN/OUT bypass.
Probably no analog bypass because we don't have analog outputs from the controller. Digital filters can certainly be cut in and out.

~ Hard bypass relay.
No.

I think these go together. I can't remember what the issue was with needing a hard bypass relay.

How would we set the input levels without bypass... again, I'm sure I down understand the process completely, but for the average guy like me, I'm seeing this is something we need to do (set input levels).

So when the unit is OUT, does the signal still get passed on to the sub?



~ LED filter indicators for both channels.
Probably not.

~ Front panel display.
Very limited

These tie in together. I assume by some of your other remarks that there will be some sort of monitor output and/or computer connection for monitoring/viewing the settings. So having a computer nearby is now a necessity and the manual method of doing things is out the door.




~ Retain normal required buttons and jog dial.
Probably not, possible IR remote capability

~ Front panel volume/gain to control output level to sub.
Probably not, possibly available over IR control.

We will either have to have these on the front panel or on the remote. Somehow we have to be able to make the adjustments, input filters, etc. OR, are you suggesting this will all be done via computer program that you will furnish?

I'm confused about these.



~ Linkwitz transform circuit.
Can't this be done with a digital filter? Looks like a shelf filter.

Not a major loss IMO. This was suggested because it is supposedly a relatively inexpensive add-on, but I don't understand how it all works... others can chime in on it.




~ Separate RCA mic monitoring and test tone output to allow for computer program monitoring.
Don't quite understand, certainly computer program monitoring is a priority.


If we have a mic input and SPL meter built in to the unit... that information has to get to a source that can read and display the information it measures. I guess maybe it's a given that this would be included.

Thanks for breaking it down.

I'm still no fan of series looping. If channel coupling means running the same filters on both channels, that seems very easy to accomplish.

The two bypass issues do go together. A wired bypass breaks the architecture.

Input level setup is a good point. I would expect this to be the first step of calibration. I envision a process step where a signal is applied to the system and the system reports any signs of clipping. Then the input must be lowered or raised until maximum dynamic range is achieved without clipping. I'll bet someone can find holes in this strategy. Hopefully you can also recommend a fix!

I don't see why one of the presets couldn't be OUT. In this mode no signal would be sent to the sub. Does this serve the OUT request? I thought OUT meant no change to the signal (even though it's being A/D'd and D/A'd.) Certainly another preset could implement this "no processing" option.

Let me expand on the computer interface. My concept is that all setup would be controlled from a computer connected via Firewire. It seems to me that calibration with REW already requires a computer. Additionally requiring a Firewire interface wouldn't be a show stopper if it adds the value I expect it to. In the simplest case the computer application could just be knobs and buttons like a physical interface (the manual method), but I imagine there is great opportunity to automate tasks and integrate with other applications like REW. The goal is to reduce user interface cost on the hardware, and enable user interface development on PC's where it is easier, less expensive, and more flexible. I'm sure attracted to the Java multi-platform approach of REW.

So yes, setup would be done on a computer running a provided application.

After setup, the computer would not be required for operation. Hopefully there will be a small list of required actions during operation. Currently I can only think of one "change preset". I'll bet we find at least a few others that will be needed during operation. These actions must be supported by front panel buttons or IR control. I also need a list of feedback (LEDs) required during operation. That list needs to be as short a possible to keep costs down and focused on operation, not setup.

SPL information from the microphone would also be sent to the computer for display and use in the setup application.


Does all that make the system more attractive or less?

[brucek]

My concept is that all setup would be controlled from a computer connected via Firewire.

A lot of people don't have Firewire interfaces on their PC's that they use for REW. I would much rather see USB for the PC connection.

I don't see why one of the presets couldn't be OUT

You're a bit confused on the meaning.
The BFD has a button on the front panel that is labelled IN/OUT.
The LED on this switch indicates its present functionality.
LED on = Filters engaged, VU meters showing output signal levels.
LED off = Filters disengaged, VU meters showing output signal levels.
LED flashing = Filters disengaged, VU meters showing input signal levels..
We use the switch to test filters in or out and also to set the input level.
We do this by playing a bass heavy movie at the loudest volume we would ever have the sound system, and then we adjust the receiver/processors subwoofer trim up or down to have the signal level just showing a yellow LED and the RED LED flashing. We hope for the best S/N and dynamic range once that's set.
Yes, it's a crude way to set the input level, but you have to understand that this isn't a fixed line level as would come from a CD player. This level is at the mercy of the receivers volume control. We need to have monitoring on input and output for clipping.

My estimate is 95% of the customers for this device wouldn't use any XLR inputs

Anyone with a DIY IB or subwoofer would likely have a pro amp. These use XLR connectors, balanced inputs. Some allow the use of unbalanced inputs by using a TS plug, but adding the likelihood of hum. Subwoofer are very prone to hum since they amplify that frequency range so well.

In addition there are those that have processors with XLR balanced outputs. There's a certain pride and admitted insanity about audiophiles that you may not be aware of. Most wouldn't be interested in using a "converter" to switch to unbalanced..... Just my opinion though.

brucek

[Otto]

Hi Barry,

Interesting that you're considering taking on this project... There's a lot to go through in the list of desired features. I'd like to come back to some of those later, but I'll offer a few comments now.

brucek is right about firewire -- few have it. I see that your company is into it, and I would still purchase a device that has firewire, but I think there should be other control inputs as well. USB is, of course, a very popular interface. I'm also tired of dealing with RS-232. I'm trying to implement PC control of my Outlaw 990 via RS-232, and it's been nothing but a headache to get that working. My Dell, and another I just ordered have no option for RS-232 (USB to RS-232 sometimes works...). If you will only do firewire, I would still be interested.

I'm also a fan of balanced I/O, and favor XLR for its positive fit, locking mechanism and cool look. Subwoofer cable runs can sometimes go for quite a distance, and I like the improved SNR with balanced signalling. My preamp has balanced outs, and I use a pro amp for my IB, so I'm balanced all the way around.

I think you already said "OK", but I would think it's got to go to at least 10 Hz.

It sounds like you're already considering it, but IR remote control is an absolute must, IMO.

A general output level control would be very important to me as well. brucek described the current method for setting input level accurately as to avoid clipping and maintain dynamic range. Giving us a sub level control on the back end will allow us to not modify our input level by tweaking our preamp's sub out level. For me, it would be OK if this were only controllable through IR remote.

I know you want to keep the front display simple. I would like it to indicate at least a few things -- output level, filters on/off, current program. I dont' think I care too much about it representing how many filters I'm using for a particular program, but it wouldn't hurt, either.

That's it for now. Thanks for considering this project.

[brucek]

~ Built-in RTA mic/line input w/ phantom power and w/ GAIN control.

~ Built-in SPL meter with selectable dBA/dBC/OFF weighting.

~ Built-in test tones (sine waves - individual 1hz increments and sweep from 5hz to 400hz or 5hz to 20khz).

Personally, I see no need for this feature (expensive or otherwise). What would it be good for.

We already use REW for setting up the EQ filters. It's an amazing program for free. It does everything you would ever want (and if it doesn't - it will).

REW uses the receivers/processors bass management and crossover when setting up the subwoofer portion and the mains portion. It allows you to add the mains and adjust phase placement etc, to get the nicest transition at the crossover. It's a true in-situation signal from the bass management for redirected bass.

I see very little justification for a built in RTA. Once you're finished, would you not then have to light up REW anyway.

I'd take the funds spent on that feature to get balanced connections and a USB port to load my filters from REW. The 1124P is $129.... I would think for $250-$300 we would at least have the same functionality.

brucek

[Sonnie]

I like the idea of having both Firewire and USB.... and I further like the idea of eliminating the mic input, SPL meter and test tones. I also see the point where XLR are probably going to be needed, although not by me, but by more than I originally was thinking.

Surely we could get Firewire, USB and XLR by eliminating the mic input with mic amp and phantom power supply, SPL meter and built-in test tones.


I also agree that we must be able to filter down to 10Hz and I second the remote being a must.

Once again, thanks for the feedback. I'll get to the points.

Firewire. Sorry, but this is the one issue I'm not flexible on. It's quick and straight forward for us to develop a firewire device and it supports our strategic goals. USB and RS-232 are not on my path. PCI and PCMCIA firewire cards are less than $20. Apple computers all come with Firewire installed. If this becomes a show stopper, I'll have to look for another application.

XLR (balanced inputs) I can be conviced here, but I'm not quite yet. Perhaps I should have described the add-on boxes I mentioned previously. They are not adaptors. They are professional quality D/As and A/Ds from professional audio equipment manufacturers. They can take in a balanced signal over XLR's and digitize it in a high quality fashion, then hand the stream to the bass managment system over the Firewire interface (skipping the bass management system's unbalanced A/D's). That is how we could satisfy the most quality concious users. (BYO A/D) The adaptor route is also valid, but I understand it would not satisfy the balanced type of customer.

XLR (balanced outputs) You've won, I'm on the team ! The architecture I'm proposing is Firewire digital audio to the sub woofer, with a small converter at the speaker. Supplying seperate balanced and unbalanced speaker (amplifier) modules is not difficult. The customer could choose.

Mic input -- I'm also flexible here. Here is my thought process. No one seems fully satisfied with the RS meters and thier calibration file requirements. Better meters are very expensive. I'm also suprised that the XLR crowd is satsfied taking their measurements from a RS mic over an unbalanced input into a PC sound card of questionable quality. I thought that providing a powered, balanced, xlr input would pave the path to using a higher quality mic over a higher quality connection, for about the same cost as the RS meter. If I'm wrong and this isn't a compelling advantage, I'd rather save the money. If I'm correct, adding this feature could add $100 in value to many customers (who don't already own meters) at a much lower cost when integrated into the system.

Test tones are free. Can't trade them for anything.

SPL meter is free. (Mic input is not) I don't care if the bass management system generates the SPL information, or just forwards the waveform to REW and REW calculates it. Wherever the job can be done best. My point was that the bass management system combined with a mic, combined with REW would not require another SPL meter.

RTA -- frankly I passed over that acronym when I read your requirements list and I focused on the mic input. I'm not interested in repeating or replacing REW functionality. Everyone seems very happy with REW. I have no desire to reinvent it. My goal is to provide a hardware platform that provides REW better data, and makes it easier for the user to apply the data generated by REW. As I understand it REW can already use a Firewire "sound card". The bass management unit could just provide REW the functionality of a high quality sound card in the simplest implementation. I've read several comments from laptop users without line-in. This enables a laptop (with firewire) to use REW.

I have to agree, if you don't have IR control, you don't have a home theater product. I'd like to skip it, but that seems irrational.

Calibration, sounds like I'm on the right track. Your description of the current process sounds familiar. I'm just saying I think we could make that same process a little more accurate and repeatable than watching for yellow lights.

Current front panel indicator requirements.

• signal level (2 led bars)
• current mode / preset (3 seven segment leds)

Current front panel control requirements

• Mode change button

There is another option I should mention. The system could be a PCI card that fits into a home theater PC. This would greatly reduce cost! It's my impression that HTPC's are not popular enough yet to support this. There are other issues also. Comments?

[DrWho]

What is the intended purpose of this device? I'm just seeing a lot of random features thrown together??? What exactly do you want it to do? What price point is being aimed for?

Right now I get the impression that you're trying to cram all of the hardware involved with REW/BFD into a single package? So basically a device for taking measurements and then applying the filters to the signal path?

I would propose making a firewire shell with drop-in modules, allowing the end-user to fully customize their purchase. For example, I already have the ability to take measurements so I don't need to purchase a module for connecting a mic to the computer. Each module would contain its own DSP, analog input/output stage and then connect to a digital bus inside the shell. Basically, the shell is just handling communication with the computer and providing any necessary signal routing. The only additional costs involved would be the mounting configuration and then matrixing the digital signals. Hmmm...sounds like a good lab project. Just throwing ideas out there.

One other advantage is the ability to sell at different performance points. There is the user that wants the bare bones approach (which you seem to be targetting), and then there are the users that want the absolute in sound quality.

-------------------

As far as maximum input/output capability...I think the most extreme case would be a stereo sub + LFE application. The L/R preouts from the receiver would be sent to the device and output band-limited signals to the LR mains and the LR subwoofers (basically taking an (N)-Way speaker and converting it into an (N+1)-Way speaker). The LFE output would be sent to the device and then output to the dedicated LFE subwoofer.

Going one step further, you might want the device to be capable of bi-amping the mains (or tri- or quad-...). This would take the 3in-5out configuration above and turn it into 3in-7out for bi-amped mains, or 3in-9out for tri-amped mains.

And then even one step further - you might want the device to be capable of handling all of the bass management for a 7.1 system, which would require a minimum 8in-8out. With the triple subwoofer configuration, it would require 8in-10out. If you biamp every speaker, then you're looking at 8in-17out...

Crazy? Perhaps. At some point it will become more cost-effective to implement all these features inside a dedicated pre/pro that way there's less conversions between analog and digital, not to mention less redundancy of circuits (since most of these features are built into the dsp's in pre/pros).

A more feasible alternative would be a subwoofer system using two subs...the user can choose to run each off the mono LFE send, or perhaps try to mix the LR with the LFE for music listening, etc etc...

[DrWho]

Two quick questions:

1) What is the purpose of having a remote?

2) Since this device is intended for home audio, couldn't there be a video output for on-screen display? It would probably be cheaper and then the front-panel could be left entirely blank.

[Sonnie]

bvwj wrote:

Firewire. Sorry, but this is the one issue I'm not flexible on. It's quick and straight forward for us to develop a firewire device and it supports our strategic goals. USB and RS-232 are not on my path. PCI and PCMCIA firewire cards are less than $20. Apple computers all come with Firewire installed. If this becomes a show stopper, I'll have to look for another application.

Well my laptop has Firewire and I think most newer PCs and Laptops have Firewire, but the older ones would have to buy the adaptor unless you could include USB in addition to Firewire.

bvwj wrote:

There is another option I should mention. The system could be a PCI card that fits into a home theater PC. This would greatly reduce cost!

You lost me on that one. If it's what I'm thinking, that would make absolutely no sense whatsoever. I don't want to have to keep a computer in my HT room.

bvwj wrote:

Mic input -- I'm also flexible here. Here is my thought process. No one seems fully satisfied with the RS meters and thier calibration file requirements. Better meters are very expensive. I'm also suprised that the XLR crowd is satsfied taking their measurements from a RS mic over an unbalanced input into a PC sound card of questionable quality. I thought that providing a powered, balanced, xlr input would pave the path to using a higher quality mic over a higher quality connection, for about the same cost as the RS meter. If I'm wrong and this isn't a compelling advantage, I'd rather save the money. If I'm correct, adding this feature could add $100 in value to many customers (who don't already own meters) at a much lower cost when integrated into the system.

Since you say the SPL meter is free, unless you throw in a microphone, then the mic input, provided it has phantom power, is only worth 50 bucks, because that is what is cost us. We can buy the ECM8000 mic and a mic amp with phantom power for 100 bucks. We can buy the Galaxy 140 SPL meter for 100 bucks and it needs no mic amp. Both of the latter are good enough and much better than the RS meter.

IOW, if you include the mic input and provided it has phantom power, you save us 50 bucks... we still gotta spend at least 50 bucks more on a mic.

DrWho wrote:

What is the intended purpose of this device? I'm just seeing a lot of random features thrown together??? What exactly do you want it to do? What price point is being aimed for?

It would replace the BFD as a parametric EQ... allowing filtering down to 10Hz and adding a few of the features (x-over, phase adj, SPL meter, etc.) we have proposed previously to Behringer for a new unit. $250 seems to be the price point we are looking at here.

It may look like a list of random features, but I think that's because we share so many common goals, that we just started in quibbling over details of the extended feature set. Thanks for slowing us down. Maybe this will help get everyone on the same page.

Goal
Affordable, high quality system to enable tuning low frequency signals for non-ideal home theater environments. (Affordable and high quality just have to duke it out until we agree on the mix.)

Core Benefits (in order) I think we pretty much agree on these
1. Parametric EQ -- Enhanced for low frequencies down to 10Hz. If this was all we did, it wouldn't add much benefit over existing solutions.

2. Time Delay -- Multiple sub systems need time delay. I'm unaware of a current affordable integrated solution.

3. Additional filtering -- crossover, phase adjust. Also valuable for multi sub systems.

4. Compatible with REW -- leveraging existing work in this market.

Architecture benefits-- This is the value I can add to the core benefits, this separates our product from other potential solutions.
1. Firewire backbone
2. Digital to the sub woofer.
3. Firewire PC interface for setup and control
4. Firewire expansion potential (multiple I/O capability)
5. Daisy chain signal routing to speakers
6. Firewire audio data transfer to PC for calibration.

Market requirements
1. Common I/O (we're discussing what common is)
2. Home Theater friendly (case appearance, IR control)
3. Simplified setup (REW integration, input/clipping calibration)
4. Price (discussed below)

Value Added Features
1. SPL mic input (under consideration)
2. Configuration Display (LED's or other, some display necessary)
3. Real Time Analysis (Not under consideration)

It appears to me that parametric eq and time delay currently cost about $250 and come in separate units not specifically designed for the home theater environment. That's why I think the price ceiling is about $250. I believe if we can match that price and include the other features above, we can be competitive. As an unknown company, it's not enough to just match what's available.

I'm also trying to understand exactly who the market is. My guess is that people who would spend the cash for this solution have already invested over $1000 in a sub-woofer, or in multiple sub-woofers. There seems to be a significant market for sub-woofers in this price range. I expect people in this range would consider paying another $250 to make their investment sound as good as possible.

Of course, the farther below $250 we can reach, the farther down the sub-woofer price curve we can reach.

I'm sure at the very top of the range a people who would never want their audio signals digitized. I can't help them.

That's what I think we are discussing. Your comments so far have helped me sharpen this vision. Thanks.

IR appears required. The only other reasonable input is front panel buttons and that doesn't seem home theater frendly to me.

Of course Firewire control is available, but that doesn't help without a computer connected.

I just imagine people will at least want to change the preset without leaving their chair.

On screen display doesn't solve the command input problem. A remote would still be required to navigate the OSD.

I think OSD would be more trouble that its worth. Discussing 2 different audio input standards is tmoohy enough. I can't imagine convering the 3 or 4 video standards my theater would need just for OSD from an equalizer.

If anyone has better control options than IR I'm definately interested.

I mis-spoke in previous posts. The Miglia HA-02 and the M-Audio Solo don't have balanced inputs. The M-Audio solo does have a balanced, phantom power mic input.

To get balanced input to firewire appears to be about a $300 box.

I'm investigating the recommended modular input approach. I may be able to accomplish that without adding too much cost.

I only offered up the idea of a PC card to check on the state of home theatre PC's. If you were all using them it might be a solution.

I suspected that they aren't widely used yet, but you have surprised me on other issues.

I'm moving forward with an independent self contained unit.

[Otto]

bvwj wrote:

Digital to the sub woofer.

I'm not sure what that means...

It appears to me that parametric eq and time delay currently cost about $250 and come in separate units

Time delay is a feature of most receivers and pre/pros. Phase control is also offered on some stand-alone subs. Allowing time delay for multiple sub outputs would be kinda neat. I'd imagine this is pretty easy to implement, so go for it. That said, I don't think it will get all that much use (I could be wrong here...).

Of course, the farther below $250 we can reach, the farther down the sub-woofer price curve we can reach.

Agreed. Shoot for $199. I'm thinking that if your initial goal is $250, it'll be real easy to creep up to $299. Also, everyone who posted in this thread should be offered one for free for their input to the development of this versatile product!

I'm OK with the firewire interface to implement PC control. It looks like there are USB-to-firewire adapters readily available on eBay (well under $20 shipped). Would your product work with that type of device? I'm assuming "yes" because the device takes care of the signalling changes and presents a valid firewire protocol to your interface. I'm asking because I just had a problem with another device NOT working with a USB to RS-232 adapter. I'm not sure why this did not work, but they said "yeah, sometimes those things don't work with our product." I think it may be because the original RS-232 protocol used 12V switching, and the adapter uses 5V. IMHO, they should have accounted for that and implemented it to work with the 5V device. I'm out of PCI slots, so I can't put another card in (well, I have a PCI-express x1, but that's it). Anyway, if you can get it to work with the USB-to-firewire adapter, I'm sold on the interface.

Good to hear about the IR. I think that would be a real showstopper for many.

You're also correct about the OSD. Too much trouble and cost for you with minimal payback. We can control the BFD with MIDI, and I rarely touch the thing -- everything is done from the PC.

To get balanced input to firewire appears to be about a $300 box.

I'm not sure what that means. Are you saying you want to convert analog balanced input to digital firewire audio? Why? I think I've misunderstood... Actually, let me ask a question: are you intending to use the firewire interface for anything other than PC/device control interface? Are you intending to run audio over firewire?

I'm moving forward with an independent self contained unit.

Yep, that's the right direction. Not too many have dedicated HTPCs.

So, what's your background with HT? Do you have any interest in seeing a system like that (esp the BFD part) in action?

Thanks again for all your effort toward this device.

I understand my concept is very different from the current approach. I'll take another stab at explaining. Yes, I am talking about audio over Firewire in addition to the PC interface. This enables many things.

1. Flexible inputs -- Adding another or a different type of input is a simple as adding a Firewire A/D. A/D fanatics could spend as much as they want on the A/D of their dreams.

2. Digital to the speaker (sub woofer). In my concept the system controller collects and processes the bit streams. Then the bit streams are sent (over firewire) to a small D/A located at the speaker. This eliminates expensive interconnect cables and any potential for signal modification over a long analog cable run. In my dreams this interface becomes popular enough that sub woofer manufacturers build in a firewire input and no adapter is required.

3. Multiple output streams. I sense multiple sub woofer systems growing in popularity. This system can support several sub woofers. That's also where time delay capability comes in. Each sub may need a different delay. Current audio processors only offer one delay for the LFE output. I saw a HSU Research demo with one mid bass module near field and two sub woofers in the corners that really pointed to a need for this capability.

Unfortunately I would not expect a USB to Firewire adapter to work. I'm unfamiliar with these devices, but I understand both protocols enough to know that would be very difficult. I expect a PCMCIA, expressCard, PCI, or PCIX card would be required for computers without a built in port.

[Sonnie]

I think the audio over Firewire is going to lose the interest of most... unless you plan to include Firewire cables and Firewire to XLR / Firewire to RCA adapters and/or the D/A unit. It's already enough that I suspect quite a few will have to buy some sort of adapter for Firewire use... which adds another $25 to the price... now for several we are at $275, which I think for the product to be successful, $199 is going the be the breaking point. And I can almost assure you, sub manufacturers are not going to implement Firewire into their subs as a result of this product and I would suspect it would be years before they would even consider it. It seems like it's getting way more complicated than it needs to be IMO. My suggestion would be to stick with XLR and RCA outputs to the sub... leave the Firewire for communicating with the computer.

This is the heart of what I need to know from this community.

It's not strategically valid for my company to develop this system unless it utilizes the full capabilities of firewire. Sorry, that's just the fact. To me, firewire to the PC is just a free benefit of the Firewire audio system backbone.

I don't think that is as bad as you imagine. I'd like to keep explaining till I'm sure you have a clear picture of my proposal.

I'm still talking about a controller with analog inputs. No new cables there. We just have to decide what exactly the analog inputs are. Expansion to other more expensive inputs is purely optional.

The cables from the controller to the speaker can be Cat5 or possibly coax. Nothing expensive there.

The D/A at the speaker might not even need a cable. If it did it would be very short.

One other advantage is that the speaker cables can be "chained'. Only one cable need come from the controller. The second speaker can be connected to the controller or the first speaker, whichever is easier. The third speaker the same. One firewire link can carry many audio streams. Each speaker adapter can figure out which stream to play.

I'm trying not to stray in to too many firewire details unless your interested. But there are many advantages to audio over firewire.

Here's the root question. If the cost were the same, would you prefer digital signal runs to the speakers or would you prefer analog runs? Personally digital runs make sense to me, but if that's not the current market feeling perhaps I'm ahead of my time.

I'd like to send digital signals to all the speakers. The sub woofer is the best place to start, because they almost always have built in amplifiers.

It seems to me you've crossed a bridge when you digitize a signal and filter it. Once you've digitized it you might as well take full advantage of the digital domain.

It looks to me the video guys are ahead on this issue. HDMI seems much preferred in the market to analog component video interconnects.

I'm happy to dig into this further if you have additional questions or worries. As I say, this is the most important issue to me in this discussion. Clearly I'm on a mission, but I've no desire to build a system no one wants.

Barry