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Audio interface, 4 or 6 channels?

Connecting Hauptwerk to MIDI organs, sequencers, ...
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Clavecin

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Audio interface, 4 or 6 channels?

PostMon Apr 11, 2022 10:58 am

I've played 2 different Hauptwerk organs recently, both set up with for surround sound with 4 speakers and a sub.
One system used a 4 channel audio interface with 2 of the channels running into the sub, then out again to one of the pairs of speakers. The other system used a 6 channel audio interface with an independent (or possibly stereo) feed to the sub.
Both organs had been a professional installation, so neither owner was able to tell me anything about why the system was set up as it was.
Which is the best way to go?
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mnailor

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Re: Audio interface, 4 or 6 channels?

PostMon Apr 11, 2022 1:36 pm

Independent sub channels allow you to send bass ranks to both (all) pairs of main speakers and mix down everything to the sub. The high pass setup only applies the sub to one pair of main speakers, so your bass ranks can't be distributed over 2 or more pairs.
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Romanos

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Re: Audio interface, 4 or 6 channels?

PostTue Apr 12, 2022 8:41 am

It just depends on how you want to set it up and what you want to spend. Sometimes the jump from 4-6 channels can be a few hundred more because that's encroaching on mid-grade interface territory. It is also possible to fake it when it comes to just the subs. If you have the whole organ going to a front pair, depending on the type of connection, you can use splitter cables so that the signal from outs 1&2 can go to the speakers and to the sub. Also, some subs allow you to send signal to them, then they send the upper frequencies on to the other speakers (ie- interface > sub > speakers) which allows the sub to control the crossover frequencies and filter out the low stuff so it isn't sent to the smaller speakers.

So it's a bit difficult to advise on what is "best" as each way of setting things up could be perfectly valid and sound equally good, depending on how you configure it. I also had one interface for a while that had two headphone outs and the headphones didn't mute the speakers, so I just used a 1/4" splitter to send RCA cables to my sub, using the whole-organ mix down from the headphone jack. (All this to say, you can fudge it just fine with four channels if desired.)
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LukasT

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Re: Audio interface, 4 or 6 channels?

PostWed Apr 13, 2022 1:41 am

In most situations, you will want all ranks sent to the subwoofer. 80Hz is a common subwoofer crossover frequency, so the subwoofer will - depending on the slope - receive signals up to 100Hz or so. Even with just 8" pipes, the low C is at 64Hz. So you will need to send all ranks to the subwoofer to get good sound, and thus sending just one stereo pair to the sub is not a good option.

(An exception might be if one stereo pair is receiving a more quiet reverb signal, in that case it might be OK to not include this in the subwoofer mix)

So the subwoofer should receive a full mix - or a lowpassed full mix - through a separate channel.

When you have a separate subwoofer output you will not route any signals through the subwoofer, so the highpassed stereo outputs on the subwoofer will be unused. That means, you will need a separate highpass for the signal going to the stereo pairs. This highpass can be an external device, or you could simply use Reaper. Reaper will add a tiny amount of delay, and 1% of extra CPU usage, and give you lots of flexibility.

Reaper is very cheap, and the Behringer UMC1820 is one of the most affordable audio interfaces, and it has more than 6 channels. So it is very affordable to get enough channels to do separate subwoofer output, and then you still have channels left in case you want to add more stereo pairs later. In my mind, there's no reason to choose an audio interface with less channels than the UMC1820.
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Romanos

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Re: Audio interface, 4 or 6 channels?

PostWed Apr 13, 2022 5:38 am

Lukas is making it more complicated than it has to be. As I said above, you can literally send the same signal to the sub and use the sub's own inbuilt filters, without any funny business in HW or 3rd party hardware or software, if desired. (This is assuming those channels are full-organ channels, as indicated in your OP.) But there is no reason you need dedicated sub channels unless you're doing complex multi-speaker setups where each stereo pair is only getting a portion of the organ's ranks. It is then that you need to create a stereo mix down channel (and HW7 is ready for this out of the box) to send to the sub.
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neptune

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Re: Audio interface, 4 or 6 channels?

PostThu Apr 14, 2022 9:00 am

Romanos wrote:Lukas is making it more complicated than it has to be. As I said above, you can literally send the same signal to the sub and use the sub's own inbuilt filters, without any funny business in HW or 3rd party hardware or software, if desired. (This is assuming those channels are full-organ channels, as indicated in your OP.) But there is no reason you need dedicated sub channels unless you're doing complex multi-speaker setups where each stereo pair is only getting a portion of the organ's ranks. It is then that you need to create a stereo mix down channel (and HW7 is ready for this out of the box) to send to the sub.


The way I read it, the original question refers to "surround sound" with 4 channels. So yes at that point a stereo mix down channel for separate sub output is required if you want the sub to play the lowest frequency of all 4 channels. Using the sub itself only works for a 2 channel setup, or if you use two channels for 32 to 8' and two channels for 4' and above etc.
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larason2

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Re: Audio interface, 4 or 6 channels?

PostThu Apr 14, 2022 1:20 pm

Lots of good answers here. There are lots of ways to do it. First question to ask is how many channels you want/can play at once. The more channels and the bigger the biggest organ you want to play, the more powerful a computer you will need. So what you need to do is decide what sample set you have/will buy will be the most taxing, then decide on the number of channels you can play, or want to play. Second, you have to decide if you have extra channels, will you use this for more than one perspective, or will you split up the pipes in a given tank across more than one speaker. There’s pros and cons either way, having multiple channels gives a bigger more immersive sound field, and having multiple monitors per channel adds clarity. Once you have decided what sample set and computer works with your desires and budget, then you buy an audio interface and monitors to match. If your decision is to play 4 channels plus sub, fist make sure your computer can play the desired sample set at an acceptable quality. If it can, you need a minimum of 4 outputs on your interface. You actually can have 2 channels going to the sub, then to your monitors, and the other 2 channels a different perspective, but my opinion is that it’s a bit more immersive if all 4 channels are mixed down to the 5th and 6th outputs, which go to a sub, but that may sacrifice a bit of clarity, depending on the set. My advice is buy more outputs than you need if you can afford them, and you can always experiment or tweak later!
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JulianMoney-Kyrle

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Re: Audio interface, 4 or 6 channels?

PostSun Apr 17, 2022 8:37 pm

You might want to consider whether you are likely to want to expand your Hauptwerk set-up in the future. If you have too few channels on your audio interface then you will have to replace it at some point, though another way of adding channels (depending on which interface you have) is to take the optical output and run it through a digital-to-analogue decoder.

Another thing to consider are which sample sets you are likely to want to use - some of the more recent ones are recorded in six-channel surround sound (or even eight channel) and you may want to have enough channels to make the most of those (though they are playable in stereo as well).

If you do intend to run multi-channel surround samplesets then you will need a powerful computer, particularly if there are a lot of stops, if the organ has a long reverb time or if you are intending to advantage of the improved signal processing features of Hauptwerk 7, as all of these are very demanding of the CPU. Large, multichannel samplesets also require a lot of RAM (64 GB or more).

I have twelve channel (six stereo pairs). I run my sub-woofer from the headphone socket of the audio interface so that it has a mix-down of all twelve, and set the cut-off frequency on the sub-woofer's own crossover. I have a 14-core i9 and 128 GB RAM. I have quite a large room and I am very pleased with how my system sounds, though the biggest improvements came from upgrading to the latest version of Hauptwerk.
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Romanos

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Re: Audio interface, 4 or 6 channels?

PostWed Apr 20, 2022 8:57 am

One other note about multi-channel setups, from someone who started with 2 channels, 'upgraded' to 6, and is seeking to scale back to 2 (or perhaps 4) again:

If you are going to go the multi-channel route, make sure that you can afford speakers that you will be happy with on all channels. When I upgraded to 6 channels, I got presonus eris e5's, and while I thought they were fine at the time, as I lived with them longer, and then spent more time with my [excellent] beyerdynamic headphones, I realized that the presonus monitors utterly lacked clarity. They are so muddy (imho) that I literally never use them now and will either sell them or reappropriate them for other things. They were all that I could afford, and it seemed like a major upgrade at the time. I convinced myself that the sound had to be better since it was all mixing in the air! Certainly dispersion around the room improved. But the quality of the actual sound being dispersed wasn't all that great, if I'm honest.

In reality, I've come to the conclusion, after having lived with these monitors for a few years, that it is better to have one really fine pair of speakers that have the clarity and vivacity that I want for close critical listening, than a plethora of medium-to-mediocre speakers that ultimately fail to satisfy. So if you can afford 4 or 6 good speakers that all cost $800+ a piece, more power to you. But don't presume that 6 $200 speakers will be better than one $1200 pair that have drastically superior components and design.

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