[neekomax]

http://www.hifizine.com/2013/06/pure-music-fabfilter-proq-active-speaker/

I saw this idea referenced in the comment section of a CNET article about Andrew Jones designs. Seems like it would be a really cool experiment. Assuming one has a Mac already, one would need:

- A pair of passive speakers with cabinets & drivers of reasonable quality, with separate binding posts for woofers and tweeters.

- an active subwoofer (or two or six )

- A pro audio USB or Firewire interface (article recommends a MOTU Microbook II) to be used as a multichannel DAC

- Two stereo amps (perhaps one class D for woofers and something else for the tweets?)   

- PureMusic, the FabFilter Pro-Q plugin software for PureMusic, and some sort of measurement software.

Starts to seem like a lot of stuff. But could active speakers EQ'd and optimized for the room be a worthy goal?

I think it would be cool to compare the original passive speakers with the active configuration. Also, might be interesting to see how inexpensively you could do it in terms of hardware, and still get crazy good sound (bang for the buck approach).

[JLM]

Why not just shop for active speakers?  Would be much cheaper, simpler, smaller, elegant, and the manufacturer would have optimized all the bits and setup any software.  Just beware that most actives are designed for studio work and intended to find the nits with a dry presentation versus home audio speakers that are designed to be emotionally satisfying (which explains all the variety of designs).  Good actives for "civilian" use include Adam, ATC, AVi, Focal, Meridian, PMC, and Quad.  Notice that they're all European and mostly British?

Years ago I auditioned Paradigm Studio 20's ($800/pair stand-mount 2-ways) versus Paradigm Active 20's ($1600/pair with the same cabinet/drivers, just active).  It was no contest.  The Actives had startling dynamics, flat frequency response (a revelation, due to more sophisticated crossover that is possible), and unbelievably deep/full bass.  Bystanders were gobsmacked when they realized we were playing the Actives and not Paradigm 100's ($2000 floor-standers), which on all but scale of presentation were surpassed by the Actives.  This was one of a handful of epiphanies I've had in 40+ years at this.  Search TNT audio for a good read on active versus passive and focuses in on your proposal.

BTW don't believe that EQ solves room issues below 120 Hz.

[neekomax]

Thanks for your thoughts, JLM.

Why not just shop for active speakers?  Would be much cheaper, simpler, smaller, elegant, and the manufacturer would have optimized all the bits and setup any software.

Because this concept leverages the processing power of a modern computer running dedicated software as DSP for the in-room response of each driver involved. I don't know of any off-the-shelf solutions that offer this. If there are, I imagine you can scratch the 'cheaper' from that list in regards to them.

Just beware that most actives are designed for studio work and intended to find the nits with a dry presentation versus home audio speakers that are designed to be emotionally satisfying (which explains all the variety of designs).  Good actives for "civilian" use include Adam, ATC, AVi, Focal, Meridian, PMC, and Quad.  Notice that they're all European and mostly British?

In this scenario, if the presentation were too dry, one would have the option of tweaking to moisten the sound.  Which one doesn't have with the typical audiophile passive setup, at least not with much precision. Even studio monitor actives don't really give you this type of control in the all important midrange, but do let you boost or attenuate shelved frequencies up top and down low.

I'm a fan of those brands for sure, except Quad, which I haven't heard. Looking at a used pair of Focal CMS-65s for my personal studio use (if I can score them cheap enough). Not sure what the provenance of those monitor brands has to do with anything, though. 

I'm also a musician (solo artist), and just moved to LA a few months ago to record an album. The studio I'm working in uses 5 Adam S2X monitors. Boy do they sound great. But we don't have full digital in-room analysis and control over every individual driver. 

Years ago I auditioned Paradigm Studio 20's ($800/pair stand-mount 2-ways) versus Paradigm Active 20's ($1600/pair with the same cabinet/drivers, just active).  It was no contest.  The Actives had startling dynamics, flat frequency response (a revelation, due to more sophisticated crossover that is possible), and unbelievably deep/full bass.  Bystanders were gobsmacked when they realized we were playing the Actives and not Paradigm 100's ($2000 floor-standers), which on all but scale of presentation were surpassed by the Actives.  This was one of a handful of epiphanies I've had in 40+ years at this. 

That anecdote would seem to be a vote in favor of trying this kind of thing, seems to me. Again though, no precise DSP involved. Imagine if there had been a third setup, the passives driven actively using software, as in this proposal. Which do you think would have sounded best in that room?

Search TNT audio for a good read on active versus passive and focuses in on your proposal.

Thanks! Will do.

BTW don't believe that EQ solves room issues below 120 Hz.

Well, it can solve some problems, at the listening position. As you know, difficult room modes below the Schroeder frequency need a distributed sub array for best results, which is why I referenced that in the 'parts list'.

But since the vast majority of program material lives above this range, seems to me a worthwhile cause to dial in the sound up there, too. No one solution skins all the cats, obviously. 

[Vincent Kars]

The weak spot of this article is that the author don't mention you have to remove the passive cross-over from the speakers.
He even recommends to leave the cap at the tweeter in place.
Now this cap is the high pass filter
You can of course do the active crossover with a PC but if you leave the passive in place you have 2 totally different filters, a nice disaster scenario.

[Vincent Kars]

BTW don't believe that EQ solves room issues below 120 Hz.

This surprises me.
In the HiFi world they talk DRC (Digital Room Correction) and pretend DRC can correct the entire 20-20k range.
In the pro-world they call it bass management because that's the part you can control using DRC
This as far as I know because you cannot correct indirect sound (the reflections from the wall).

What are the reasons one cannot correct below 120 ?

[macrojack]

I have been considering selling my big rig horn hybrid speakers and downsizing significantly. For my bedroom/office, I bought myself a pair of KRK Rokit 8 powered studio monitors. They are great. So ......... I'm thinking that I will sell my horn system and replace with powered monitors. Then this topic comes up and I realize I have most of what this topic requires. But I'm going to resist the temptation to delve even further into the expansion and continue to pursue contraction. Much as I would like to, I'm not going to get younger. It's time to recognize the facts about my situation and follow whatever shred of wisdom has guided me to shrinking the system.

With that in mind, I want to ask you guys if anyone here has experience with Event Opals? For that matter would anyone like to know about my horns? The Opals, on paper, appear to answer all my prayers but there is no way I'm going to hear them within a couple of hundred miles of home -- and even then, they will probably be in a guitar store. Sure hope somebody here can fill in the blanks about their sound and practicality.

[neekomax]

The weak spot of this article is that the author don't mention you have to remove the passive cross-over from the speakers.
He even recommends to leave the cap at the tweeter in place.
Now this cap is the high pass filter
You can of course do the active crossover with a PC but if you leave the passive in place you have 2 totally different filters, a nice disaster scenario.

 

Of course. Yeah, I guess that means you have to open up the speakers and solder connections from the drivers directly to the binding posts, bypassing the crossover network, right?

Does a single capacitor between an amp and a tweeter make a difference to the sound besides eliminating on/off thumps?

[neekomax]

This surprises me.
In the HiFi world they talk DRC (Digital Room Correction) and pretend DRC can correct the entire 20-20k range.
In the pro-world they call it bass management because that's the part you can control using DRC
This as far as I know because you cannot correct indirect sound (the reflections from the wall).

What are the reasons one cannot correct below 120 ?

Above the Schroeder frequency (that 120 Hz that JLM referred to; actually varies according to the room dimensions), the room acts like a sound reflector and/or diffuser. So while the indirect sound (reflections) will play a part in what you hear at the LP, you can use EQ (and/or good speaker design) to achieve a flat in-room response; what you hear coming straight from the speakers will essentially be mirrored properly in the reflected sound. 

Below the Schroeder frequency, the room acts as a resonator. In that resonator model, the big ole' bass waves sum (amplify) each other in some spots and at some frequencies as they slosh around, and also cancel each other out at still other spots and frequencies. So you end up with room modes. At the listening position you'll hear a bass line get crazy loud at some moments, and get thin and wan at others. You'll also perceive an overall boomy or 'sucked-out' character to the low end in general.  But go to a different spot in the room, and the frequencies at which these peaks and nulls occur will be different. So you can't really eq out the problem areas, as they vary depending on listening position.

I do have my bass eq'd for my LP in my room, but I also have multiple bass sources (three subs, one in each speaker and a third in a different location), so that 1. the need for the eq is less, and 2. the eq I do apply is closer to helpful at other positions. This is because the multiple bass sources 'fill in' the room modes (actually, create 'more' modes, but all of them have lesser effects).

For more on this, see Duke's replies here. He makes a multi-subwoofer system with a specific crossover network. Here he explains the physics better than I can:

http://www.audiocircle.com/index.php?topic=132434.msg1407877#new

[JLM]

neekomax:

Near-field setup takes care of most of the higher frequency room interactions.

Tinking with DSP can be undone easy enough, but would probably drive you crazy and end up making a mess of things.  Besides we're conditioned to listen in "normal" residential settings, so I don't obsess about higher frequency room interactions.

macrojack:

Any Guitar Center around me would never stock Opal's (I've only seen cheaper monitors there).  Again most studio monitors have a dry, fatiguing sound versus home audio that provide a more colorful, satisfying experience, so auditions would be in order.

Vincent:

The best explanation for in-room bass behavior I've read is to think of the room as a bath tub with a few inches of water in it.  As you move your hand the length of the tub (to produce low frequency waves) the resulting waves can be seen to travel to the end of the tub and then rebound.  As the returning waves meet the next wave it will add to, cancel, or otherwise affect the other wave.  Where that would occur will depend on the wave size (frequency) and location.  Adjusting the size of your hand (volume) does not change the concept, so DSP can't help.

[Tyson]

Above the Schroeder frequency (that 120 Hz that JLM referred to; actually varies according to the room dimensions), the room acts like a sound reflector and/or diffuser. So while the indirect sound (reflections) will play a part in what you hear at the LP, you can use EQ (and/or good speaker design) to achieve a flat in-room response; what you hear coming straight from the speakers will essentially be mirrored properly in the reflected sound. 

Below the Schroeder frequency, the room acts as a resonator. In that resonator model, the big ole' bass waves sum (amplify) each other in some spots and at some frequencies as they slosh around, and also cancel each other out at still other spots and frequencies. So you end up with room modes. At the listening position you'll hear a bass line get crazy loud at some moments, and get thin and wan at others. You'll also perceive an overall boomy or 'sucked-out' character to the low end in general.  But go to a different spot in the room, and the frequencies at which these peaks and nulls occur will be different. So you can't really eq out the problem areas, as they vary depending on listening position.

I do have my bass eq'd for my LP in my room, but I also have multiple bass sources (three subs, one in each speaker and a third in a different location), so that 1. the need for the eq is less, and 2. the eq I do apply is closer to helpful at other positions. This is because the multiple bass sources 'fill in' the room modes (actually, create 'more' modes, but all of them have lesser effects).

For more on this, see Duke's replies here. He makes a multi-subwoofer system with a specific crossover network. Here he explains the physics better than I can:

http://www.audiocircle.com/index.php?topic=132434.msg1407877#new

The swarm approach is an excellent method to achieve good bass response in a typical listening room.  Another option is open baffle bass, which takes the opposite approach - exciting fewer, not more, room modes. 

[neekomax]

neekomax:

Near-field setup takes care of most of the higher frequency room interactions.

Tinking with DSP can be undone easy enough, but would probably drive you crazy and end up making a mess of things.  Besides we're conditioned to listen in "normal" residential settings, so I don't obsess about higher frequency room interactions.

macrojack:

Any Guitar Center around me would never stock Opal's (I've only seen cheaper monitors there).  Again most studio monitors have a dry, fatiguing sound versus home audio that provide a more colorful, satisfying experience, so auditions would be in order.

Vincent:

The best explanation for in-room bass behavior I've read is to think of the room as a bath tub with a few inches of water in it.  As you move your hand the length of the tub (to produce low frequency waves) the resulting waves can be seen to travel to the end of the tub and then rebound.  As the returning waves meet the next wave it will add to, cancel, or otherwise affect the other wave.  Where that would occur will depend on the wave size (frequency) and location.  Adjusting the size of your hand (volume) does not change the concept, so DSP can't help.

Hmmm. I don't listen near-field, unless I'm in the studio. Don't think that's a solution I'm too excited about.

I obsess about high frequency in-room response. And that of the mids, mid bass, and bass. Because it's what I hear. 

As far as whether f'ing with DSP in an active config would drive me crazy... with my level of obsession over all things speaker/sound related being what it is, it ain't a far drive. 

By the way, the Guitar Center that's near me in West LA has all kinds of quality monitors. Not sure where macrojack is, but I wouldn't count it out.   

[macrojack]

Macrojack is 4 hours west of Denver and 4.5-5 hours east of SLC. The big city in my area is Grand Junction. I can check out Hart Music but the chances are very slim. When I'm ready, I'll explore. Meantime, I was hoping someone here had something to say about the Opals.

[neekomax]

So, just for fun, I did a sweep for likely candidates that might fit the bill for the experiment. Again, the criteria being 1. reasonable cabinet and driver quality 2. good price/quality ratio, and 3. two sets of existing of binding posts so that no woodworking or cab mods would be needed, besides opening them to bypass the existing passive crossovers and connect the binding posts to the respective drivers directly.

Please let me know if I'm not understanding something or if there are good reasons why any of these would or wouldn't be appropriate choices for this application.

Here's a set of Spendor monitors on AC for $450:

http://www.audiocircle.com/index.php?topic=131548.0



A pair of Monitor Audio RS1s for $450 shipped.

http://ebay.to/1DBEcxW



A pair of Focal JM Labs Chorus 706s, with nice stands included, only $450. Owner will throw in a SVS 12" sub for $350!

http://bit.ly/1ADhgOX



Some B&W 685s for $500

http://bit.ly/1LTyPw1



Getting fancy... $1,200 would get us this set of PMC TB2i monitors. Me likey. 

http://ebay.to/1wucKgc






 

[Odal3]

Thanks for sharing. I have been starting to look into something similar but using Richard Taylor's open source solution. See here http://rtaylor.sites.tru.ca/2013/06/25/digital-crossovereq-with-open-source-software-howto/

This is the same solution that mirrored the performance of Linkwitz LX521 speakers. http://www.linkwitzlab.com/LX521/DSP_challenge.htm
So this solution is an alternative option that may be cheaper to implement but requires some Linux knowledge. I will use it on some diy speakers.

Btw:are there any good multichannel USB Dacs out there that won't cost a fortune?

[neekomax]

Thanks for sharing. I have been starting to look into something similar but using Richard Taylor's open source solution. See here http://rtaylor.sites.tru.ca/2013/06/25/digital-crossovereq-with-open-source-software-howto/

This is the same solution that mirrored the performance of Linkwitz LX521 speakers. http://www.linkwitzlab.com/LX521/DSP_challenge.htm
So this solution is an alternative option that may be cheaper to implement but requires some Linux knowledge. I will use it on some diy speakers.

Btw:are there any good multichannel USB Dacs out there that won't cost a fortune?

Cool!

Re: Multichannel DACS: How many channels of output will you need for your project? I would say that a used pro audio USB or FireWire audio interface like something from MOTU (those pieces usually have an extensive I/O array) will be your best bet. Good conversion, too. I bet you won't even need to spend $500 on that part, given eBay.

[neekomax]

For instance: How about 10 channels of analog output with 24/192 conversion capability over either USB or FireWire?

Oh, and if that's not enough, there's always the 20 additional channels of digital output 

$500. You can get similar (but less recent and/or less well regarded) tech for even less, I'm sure.

http://m.ebay.com/itm/221703049417?cmd=VIDESC&gxo=true

[Vincent Kars]

JLM/Neekomax

Thanks for the explanations

Vincent

[Odal3]

neekomax - probably 6 to 8 channels would be enough. Thanks for posting the link, but that is probably more than I need for some simple experimenting before I'm ready to commit to something more serious. Will look around a bit - there seems to be a few different solutions out there.