Sparky W

Thanks for the clarification, Rob. The only issue I see with the agg device workaround is that it doesn't work with DACs or other interfaces that aren't CoreAudio compliant (e.g., those that have their own drivers). In those cases, multiple device selection within the app would seem the best option. Given the surge in async USB implementations -- many of which use custom drivers -- it's likely that that issue is going to grow in significance. (Though, frankly, as an end user the custom driver thing is annoying.) Bob, yes, if someone is going to build a system around a pro DAC setup, they should certainly consider the available multi-channel DACs along with those that have wordsync capability. Maybe somebody needs to make a USB or Firewire interface that splits four output channels into two two-channel SPDIF outs. That'd be the perfect complement to PM.

"This seems to have already started." To what are you referring? Have you seen signs of them discouraging its use? That would surprise me since two of Apple's major products, Logic Studio and Soundtrack Pro, can both use aggregate devices, and Apple provides How-Tos on using aggregate devices up through and including Snow Leopard. Not to mention thousands of pro audio users who would probably explode if the capability went away.

renkinj, Mac OSX has a few plugins that come by default but, as Bob said, they're not the best quality. You can use them when you pull up the menus in PM's plugin window. I tried a few, but the sound quality was not great. I have the Blue Cat Audio Parametr'EQ package, which sounds very good and has a nice interface. The FabFilter plugins are also very nice, but a bit more expensive. There are many other options for plugins. I'm reluctant to spend a lot of money, though, until I see what PM will provide, and until I'm sure that PM will stay in my system longer-term. I don't know how you are doing your room EQ right now, but I've found that Room EQ Wizard can be hijacked by Audio Hijack Pro, and I can use the EQ plugin within AHP to do my EQ, then transfer the settings to a copy of the same plugin in PM. It's not exactly an elegant approach, but it works very well. As for the aggregate device approach, if it's working for you, great! But I have some concerns: 1. It doesn't work for all DACs. In particular, those with their own drivers seem to not work. There may be other gotcha's, as well, so it will definitely be a trial-and-error thing for each DAC you try. 2. It may not work with all combinations of DACs. 3. Because Channel D doesn't support or endorse the usage of aggregate devices, it could stop working in a future release of PM (e.g., as a side effect of some other change). So, while it does appear to work in many cases, I would be cautious about building a system around that functionality. On the other hand, we're blazing trails here, so that may just be the cost of doing business.

Thanks, Bob. To the extent that my response seemed harsh, I apologize, too. FWIW, aside from my mystification over the crossover issues discussed here, and a few other minor issues, I'm generally happy with PM. I think the program is quite well implemented and, as you've pointed out, the feature set is nice.

Bob, I am perfectly content for us to disagree on the issues we've discussed here, and I bear no grudge with you over your view of audiophiles as too technically limited to make use of a simple crossover (despite plenty of evidence to the contrary). But for you to suggest that it is "untoward" to ask about the status of a promised feature is nothing short of bizarre. When I (and I presume many other people) bought PM, there was a claim on the web site that there would be EQ in an upcoming release. The feature is overdue, and that claim now seems to have disappeared from the site. Why is it wrong for me to ask about it? Your answer seems to be: "Because I'm a fan of Channel D." Sorry, I bought a product from a company, I didn't join a cult.

"Perhaps if you spent less time complaining and more time educating yourself, your posts would appear more impressive than they do now." Re education, see #2 in my previous post. You are invited to participate. "Just because it doesn't do what YOU want it to do, doesn't invalidate the program for the rest of us." Let me get this straight: Because you're happy with PM, I'm not allowed to discuss the features I'd like to see in the product, or the way the features are represented in the marketing material? And you speak for everyone? Interesting. That sort of zealotry is usually reserved for the fanbois on Apple forums. BTW, what happened to the EQ that was supposed to be coming in 4Q2010? I guess I should shut up about that, too.

1. What's not to get? It's an advertised "feature" that seems to be a selling point, but upon closer examination is not useful to the overwhelming majority of the potential market. 2. I invite you to do a poll of audiophiles and look at the ratio of those using two-channel DACs to those using multi-channel DACs. Or have a look at the DACs for sale on Audiogon. Or leaf through the pages of Stereophile or TAS and compare the number of ads for two-channel vs. multi-channel DACs. 3. Why don't you envy him? He's running a business in a competitive industry and he has customers telling him about the features they'd like to see in his product. To the extent that he provides the features people want, he'll succeed. To the extent that someone else provides those features, they'll succeed at his expense. If I were him, I'd want the information, even if I couldn't always act on it.

I agree that aggregate devices are non-ideal, and a multi-channel DAC would be easier. But I think it is unrealistic for Channel D to think that a significant number of audiophiles are going to switch from their favorite audiophile DAC to a multi-channel pro DAC. It's much more likely that they'll just switch to another playback program that offers the performance and feature set they want. The crossovers in PM are a great idea (it puts the crossover where it should be in the system) and well implemented, but the fact that 99% of their potential customer base can't use the feature seems to be almost the opposite of a selling point -- it's a frustration. They advertise crossovers as a feature of the product, but unless you already have a multi-channel DAC, or can figure out the magic aggregate device incantations (which Channel D recommends against), then it's unusable. Driver: "This car seems underpowered. I thought it had a V6." Salesman: "Well, yes, it has six cylinders, but only four of them actually work unless you live in Portland..."

I didn't have any clock problems, but that doesn't mean they can't happen in some situations. Mr. Robinson is somewhat incorrect about the clock issue, however. When configuring an aggregate device, you can choose one of the devices to provide a master clock, and allow the aggregate device to resample for the other device(s) as necessary to maintain sync. Given the usefulness of the PM crossover features, I'm a little surprised that the developers don't give the program the option to connect to two (or more) devices, and allow routing the various channels to those devices. This functionality exists in other software (Audio Hijack Pro, for example), so it's not technically impossible. Seriously, what do they consider the market for this feature? Why did they go to all the trouble to include the crossovers and then limit their usage to the tiny percentage of audiophiles who have four-channel (or more) pro DACs?

Hi J, I'm glad you found the thread helpful. As to your questions: 1. Yes, I used two USB DACs, and just plugged them both into the USB bus on my Mac Mini. I was a little worried that this would overwork the USB bus, but I experienced no problems or dropouts. I will note, however, that this won't work with all USB DACs. If the DAC requires its own driver (like the Wyred 4 Sound DAC-2, for example), it will not work in an aggregate device. The solution in that case is to get a USB-to-SPDIF converter (that doesn't require a driver) and set up your aggregate device to use the converter. 2. The two devices must have the same max bit rate configured in Audio Midi Setup and/or Pure Music. I tried devices with two different bit rates, and it did not work. So you are limited to the maximum bit rate of your device with the lowest bit rate. The HRT Music Streamer can get you to 24/96 pretty cheaply, but I don't know how to get to 24/192 cheaply. Maybe someone else can suggest some options.

And thanks for your help. A couple of new developments: I forgot to mention last time that once I installed the EQ onto the LPF side of the processing chain, I needed to revise the delay of the mains to account for the processing lag of the EQ. It slows that leg of the processing by a few milliseconds. Upon further listening, the Apple built-in DAC turned out to be unsatisfactory, leaving me with somewhat muddy bass. So I bought an HRT MusicStreamer II ($149 -- a bargain!) to handle the LPF side of things. I was somewhat concerned about having two USB DACs on the same bus (especially two async DACs), but everything seems to be working just fine. And my bass sounds better. Once it was connected, I had to reset the sub level and the delay. My earlier concerns about the LPF side being considerably lower in level appear unfounded. I'm pleased with the quality of the HPF in PM. Aside from changing the frequency response, it is essentially inaudible. This is definitely the way to go for people who want to use a crossover in their system. I think it's a big selling point for PM -- PM should include a "How-To" on their site.

So I managed to make this work. It's actually relatively straightforward: First one needs to create an aggregate device in the Audio Midi Setup. For the time being, I ran a stereo cable from my Mac's headphone out jack and ran the left and right wires out separately to my L and R subs. I'll probably get an outboard DAC soon, but this works for now. I made the aggregate device using Apple Built-in Audio (the headphone jack) as the first device, and my Ayre DAC as the second. The Ayre is the clock source, and the built-in is set to resample as necessary. The important thing when configuring this way is that both devices must have the same sample rate -- I set both to 96K and 2 chan/24 bit. I then selected this device as the default system output (note: I also turned the volume for the internal sound effects (alerts) down to zero). (The other option here is to select the Aggregate device from within PM.) Once I fired up PM, I sent the LPF channels to 1R,2L and the HPF channels to 3R,4L. I confirmed that everything was working (at low volume) and sample rate changes were handled correctly. I got the subs and the mains running at about the same volume, then used the delay setting on the mains to get them into phase with the subs at the crossover frequency (80 Hz). To do the room correction, I used Room EQ Wizard (REW). (Eric, ARC actually looks pretty good -- I'm going to do some more research on it. Thanks!) This was non-trivial because there are currently some problems with REW and Macs, the biggest of which is that you have to downgrade your version of Java to get it to work. This is not for the faint of heart, so I can't currently recommend REW for Mac users. Nevertheless, I had a working version, so I used it. It sends horrifying loud noises to my DAC, however, so I only ran it on the subs in isolation. I used Audio Hijack Pro (AHP) to catch the REW output before it got to the audio device. Within AHP, I used the Blue Cat Parametr'EQ to filter the output to get the response I wanted. When that was done, I installed the Blue Cat EQ onto the LPF bus within PM, and copied the settings that I'd used to get my desired response within REW and AHP. Kind of clunky, but it worked. I did some listening today, and everything sounds pretty good. Once I've relaxed and listened for a bit, I'm going to try FabFilters and see if there are any audible differences relative to the PM and Blue Cat filters. And, as I said, I'll probably get another DAC (though I'm a little concerned about having two DACs on the same USB bus). But this is pretty cool -- I now have my crossover and room correction all happening in the digital world, and my analog path has a minimum of components: DAC to amp to speakers. The resolution is pretty amazing, and the bass is tight and controlled and pitch-specific. My only complaint is that there is sometimes a little pop or click when jumping from one track to another. This may be an artifact of the EQ, but I'm not sure yet.

Thanks for the input. I've found the sample rate changes to work well with my DAC, too (it's one of the things I really like about PM), but this aggregate device thing may be a bit more tricky. There are some settings to play with -- I'll let you know what I find. Thanks for your input on the xover. It's good to know that the gain is correct. Now I can focus my efforts on getting the other bits to work right. In you experience, is there any degradation in the sound quality from using the high-pass filter at around 80 Hz? The xover/EQ combo would be fantastic if I can get all these parts to play together -- I like to do room correction and it would be awesome to do it so far upstream while everything is still digital. About the buses on the plugins: I see "1, 2, 3, 4, All". Are 1, 2, 3, and 4 the individual channels? Thus if I want to EQ my low-pass channels, would I put a separate EQ plugin on each of #1 and #2, or can I combine channels 1 and 2 on a single bus and use a single EQ plugin? Sparky

Okay, I gave it a brief try yesterday, and it seems to work. The Mac's Audio Midi Setup program makes it easy to create aggregated devices, and Pure Music recognizes them and the channels line up in order of the inputs on the collected devices. I was able to engage the crossover and send the low-pass output to one device and the high-pass to the other. Two issues I ran into: 1) There seems to be some weirdness when Pure Music changes sample rates on the fly. This didn't always work, but I didn't have time to fully scope out the problem or try many solutions. Obviously, when you treat two devices as one, there is the potential for miscommunication with one or the other. 2) The low-pass filter output of Pure Music seems to be *many* dBs lower than either the high-pass output or the unfiltered output. There is a trim setting on the filter, but even with it cranked up all the way (+12 dB) I could barely get sound out of either of the connected devices (routed to my subs). Again, more experimentation is in order, but this feels like a bug in Pure Music. Hopefully I'll more time to play with it this weekend. But if anyone else takes a crack at this, I'd like to hear about your experience. Sparky

Hi Bob, I had a look at Jackrouter, and the manual directed me to Audio Midi Setup where you can create an "aggregate device" (i.e., a single virtual device that combines two or more physical devices). I haven't had time to experiment with it yet, but it looks promising. Have you tried this? By crossoverless, I just mean that I'm currently running the full-range signal to both my mains and my subs. The subs have low-pass filters built in, so what I really need is a high-pass filter for the mains. But, as I said, my experience with line-level filters has been less than satisfying, so I was hoping to do it in the digital domain. Sparky