Bass Management System Development - Page 8 - Home Theater Forum and Systems -

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post #71 of 86 Old 03-08-07, 05:35 PM
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Re: Bass Management System Development

The business case:

The impetus for this discussion was a request for a bass management system that improved on the currently available and affordable 90% solution. It's clear who would be the best manufacturer to produce that device. It appears they are not interested in this market.

In my view it would be foolish for another company to develop this improved BFD. If the product were successful it would be too easy for B to upgrade their device and thank you for the free market research while they undercut your price.

To be successful a new product has to have a new hook that offers some protection from this type of competition. I also think you have to "shoot ahead of the duck" and look for features that will be important in the near future.

My hook is the FireWire backbone. My emerging feature is digital to the speaker. I understand you can't sell a product in the present that's designed for the future, so I'm trying to understand the legacy requirements I need to support for a product that's attractive today and paves a path toward the future.

The other issue is that this development requires capital. So far this effort has no external funding. If someone wants or believes in this type of product enough to help fund development I would be far more willing to implement their suggestions.

The way it stands now it's my funding so the features need to make sense to me. I appreciate your efforts to convince me of your viewpoints. Many of your ideas have impacted my plans and challenged me to look for better solutions.

I should have a firmer product specification proposal to share shortly.
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post #72 of 86 Old 03-09-07, 09:29 AM
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Re: Bass Management System Development


Your business reasoning is spot on and you are thinking correctly. Yes, if you do an improved version of B's product, they would likley copy it and maybe tweak a feature in order to claim better than you. B is know for copying products.

Hang in there and come up with something with some IP content or a product for a niche market that wouldn't be of interest to a big B company today, but that could be expanded into that future market. The home infrastructure and active crossover implementations look interesting.
post #73 of 86 Old 03-09-07, 07:28 PM
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Re: Bass Management System Development


I'm really not interested in analog processing. My only analog focus is impedance, level, and low pass to the A/D then the inverse for the D/A. I expect there is a contingent that loves the "op amp sound", but I don't think I can help them.

It seems to me if any part of your process is digital you've already lost the pure analog benefits, so you might as well take full advantage of the digital domain.

The good new is that all the analog filters that have been mentioned have digital counterparts. They can all be reproduced with 2nd order IIR filters. Here is an excellent introduction on how.

I believe the digital filters offer the tweaker much more tuning and testing flexibility to try different filters without soldering down new components. My goal is to offer a digital processing platform that is simple to setup, but offers options friendly to advanced filter tweakers.

That's a fundamental advantage to the PC setup architecture. Filter software is relatively easy to setup and run on a PC. The results of this process can then be downloaded to the processing system and the DSP can do what it does best, run filters not design them. This allows upgradeable filter development via PC software updates rather than configuring a few preset algorithms to a standalone unit.

Implementing a leading edge general purpose DSP system was my initial concept for system processing. That provides ultimate flexibility, but also requires a lot of software development to make the system work at all.

Recently I stumbled on to a leading edge limited purpose DSP. It still has state of the art capabilities, but only requires register based setup to operate. The processing software is built in (and fully tested). This limits its capability, but I think its existing capabilities are very much what is required. I believe it can achieve 99% of what we need and can reduce development and time to market by half. It also cost less.

Please evaluate these capabilities.

3 independent processing channels -- Connected inputs can be unlimited (FireWire). Each of the three channels can be a mix of up to 6 inputs (8 physical inputs total). Each of the three outputs can be sent to unlimited destinations (FireWire). Each of the three channels has it's own independent processing capabilities (plus some interconnected capabilities).

16+ filters per channel -- Each filter is a 2nd order IIR biquad cascaded to the next (48 bit data, 28 bit coefficients). Each of these filters can be used for a parametric band filtering. They can also be used for crossover filters, phase adjustment, or any other IIR filter. There are a few more filters available for parallel summing, but they don't seem very flexible.

Delay buffer -- Each channel has adjustable delay before its output. There is also reverb delay summing but I doubt that adds much benefit for us.

VU meter -- Each channel can be processed through a VU meter and the results reported back to the system.

Soft mute / volume -- ability to avoid popping across setup changes.

Shelf filter -- I'm not sure how valuable this actually is, it's not completely parametric. There is a small selection of fixed frequencies and a large selection of gain / cut levels.

Dynamic range compression/expansion-- Again I doubt this adds value, but it's available. It allows pushing soft signals up or loud signals down a programmable amount. It's very parametric with dual range adjustable slopes and levels.

8kHz-96kHz sample rates. 24 and 32 bit samples.

The big thing that this DSP doesn't offer is FIR filtering. Possibly a future device could implement a general purpose DSP for FIR filters. The current system concept does include an FPGA which could offer some FIR capability, possibly an FIR sample rate converter for higher quality bass processing.

Without including input, output, or user interface specific issues, does this processing capability sound adequate? I sure hope so, it looks like a sweet solution to me.
post #74 of 86 Old 03-30-07, 12:35 PM
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Re: Bass Management System Development

I think firewire is a great idea, but in describing it this way it seems to me that you are eliminating the s oundcard's DAC, or are passing a digital signal on to an outboard DAC.

This is a terrific idea because it eliminates the noise and interference (and general poor quality of many PC sound sources)

I love the idea of balanced input with phantom power to use with my ECM 8000 that's great, as is the inbuilt SPL to calibrate the mic to a reference level.

The way you are describing this now, it sounds to me like a high quality outboard DAC/Preamp with parametric capabilities - It is almost a Zhalou DAC / Yulong Crystal DAC & Feedback Destroyer in one box - a killer combo?

Is this the approach - I'd encourage a search / read on the Zhalou / Yulong - they've had terrific reviews.

That said the Zhalou/Yulong devices are high quality DACs, but they alone run in the $200 range to have a high quality audio path. They also include things like socketed opamps so that you can replace them with some of the newer chips that come out - I like the LM4562 and would encourage it's use, or at the least socketed op-amps to make it easier to mod. The LM4562's can be spendy and maybe only enthusiasts will want to take that approach.

So - is this a combo DAC / Parametric EQ? or would you use this as a pre stage going to an outboard DAC? Is it optimized for 2 channel or multi channel calibration? would you include a sub woofer pre-out on it?

Last edited by dsiroky; 03-30-07 at 12:43 PM.
post #75 of 86 Old 04-02-07, 03:40 PM
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Re: Bass Management System Development

I have to admit I'm surprised no one posted much enthusiasm for the capabilities of the audio processor I described.

It seems to me a near ideal way to get the functionality we've been discussing at a very reasonable cost.

One thought I have is that the description is a little abstract and a better description of the actual configuration might be more interesting.

To that end, I mocked up a configuration form prototype. Please click the link to have a look. The form doesn't actually do anything, it just illustrates the potential flexibility and ease of setup.

I'll quickly describe the blocks.

Across the top are selections to configure up to 10 seperate setups, plus the default (bypass) setup.

Up to 8 inputs can be selected from a very large number of potentially connected ADCs or digital streams.

Next these selected inputs can be mixed onto the 3 processing channels. Or a single input can be used 100% for the channel(s).

Each of the three channels can then be directed to a specific analog (or digital) output.

The center block configures the parametric filters for each of the three channels. Up to 10 filters can be configured for each channel. The center frequency as well as the bandwidth and gain are fully selectable. The PC will calculate the proper coefficients for the DSP. I didn't add all the configuration boxes for all the band filters, assume the table would expand as additional filters are activated.

On the right side are crossover configurations for each channel. 12 and 24 dB slope filters are selectable or bypass-able. Please note the phase at each crossover frequency is also configurable.

Delay is pretty self explanatory, I guess it could accept feet or meters instead of milliseconds.

I didn't put in shelf filtering capabilities, I'll have to think a little more on how to implement their interface.

Of course there can be options for more advanced users to enter their own coefficients, but I wanted to display here just how easy and powerful a simple configuration system could be.

Again, this type of interface would appear on a FireWire connected PC during system setup. After setup, the user would just select one of the configured presets (without needing a PC).

Does that help describe the concept and capabilities?
post #76 of 86 Old 04-02-07, 03:57 PM
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Re: Bass Management System Development

Um, "easy" is not the word that comes to mind...

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post #77 of 86 Old 04-02-07, 04:13 PM
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Re: Bass Management System Development

The main hang up I think most everyone has is Firewire to the sub amp and having to have some sort of powered DAC at each sub. I have three subs, two in each front corner and one in the rear of the room.

I don't really have that big of a problem with Firewire from the computer to the unit itself, although I'll have to buy some sort of Firewire adapter for my laptop.

The interface appears simplistic enough. The unit itself needs to have simple and current connectivity, not something we have to jump through 10 hoops to make work.

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post #78 of 86 Old 04-08-07, 09:53 AM
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Re: Bass Management System Development

I like much about your approach of digital to the speaker as well as the ability to drive each speaker/driver locally.
While this may be a bit out of the topic - are you considering a unit that would do full range DRC and Speaker/driver correction?
Basically I am thinking of a systems that would use digital in and drive potentially each driver with a seperate amp and would function as the crossover in the digital realm doing phase/amplitude correction. This would be similar to Audyssey system but operate in digital to the speaker/driver.
post #79 of 86 Old 04-08-07, 05:48 PM
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Re: Bass Management System Development

I keep wondering why anyone would want to reinvent the wheel and give it a fragile Firewire axle?

brucek said it all. The AV/HT world is now aching for a BFD without the trimmings and tidied up in detail. This is a real worldwide AV/HT need that nobody is listening to. Nobody!

Rightly or wrongly we sell the idea of electronic subwoofer equalisation to everybody who will listen on the AV forums worldwide.

We simply want a BFD that can filter right down to 10Hz, has silent on off, doesn't hum and doesn't look like a cheap 70s scifi spaceship prop.

Behringer's shortsightedness in removing the 1124P from the market without offering a real replacement is so stupid they should crash and burn!

They were given a heads up by Sonnie but chose to ignore it because it probably wasn't in their "normal" pro-gear marketplace. They obviously haven't a clue about their customer base! Or couldn't care less about the hundreds of thousands of potential customers now looking at SMS1 and turning their noses up at the dumb price tag.

Thousands and thousands of 1124Ps were purchased by sub owners worldwide from any music store that had them. Sub owners loved them or hated them but they still learned to use them to make their subs listenable in perfectly ordinary domestic rooms. John M is a saint for producing REW! brucek and Sonnie should be honourably knighted for their work in making REW work for idiots like me.

Most sub owners don't want a computer in their AV room/HT except to set the sub up with REW + BFD and then forget it.

Most sub owners don't want to spend more than a couple of hundred dollars making their sub's work as nature intended. That probably includes the SPL meter too!

They want to use cables they recognise as cables. Balanced XLR and USB.

Offer us a tidied up BFD1124P and you will have to fight us off. Provided you make a 230 Volt 50Hz version for Europe etc.

I wouldn't buy your Firewire box with all the dangly bits if it cost pocket change and fitted in a matchbox. It doesn't interest me. It has no relevance in my AV world. A BFDi (improved) does interest me and I would pay twice what my trusty 1124P cost me without batting an eyelid.
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post #80 of 86 Old 04-08-07, 06:43 PM
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Re: Bass Management System Development

I'd love to see someone develop this to handle up to 5-6 subs and independently measure and control them.

I will end up at some point with a projection system and CIH and have room to do

3 x Definitive BP7006 for the front L/C/R and each tower has a 300w RMS 8in sub, plus room for two more LFE subs

EDIT:I hope and plan on doing Denon AVR3808 + Emotiva BPA-1 (3 for the 7006s) and would love to set the towers to small and use the "X" device to be a go between for LFE to the amps then to the towers LFE RCA input. Along with this two subs in rear or two small IB...


Last edited by khellandros66; 04-08-07 at 06:50 PM.
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