Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 388 - AVS Forum
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post #11611 of 11632 Old 09-12-2014, 01:21 PM
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Originally Posted by HDgaming42 View Post
Yes the null is there when I just use L or R. I found the best location (flattest response) for my mains over the whole frequency range, but unfortunately I end up with a null around 80Hz at that spot--worsened by the raising in height of my MLP.

I used to be able to get away with a cross at 120Hz, but now have to move to 200Hz to even out the mix of mains and sub(s).

To invert the phase I was using the miniDSP's invert function. The second sub doesn't even have a phase knob.

I'll post some graphs like you've asked. Probably late Saturday. Thanks!
I'm guessing that the sub up front has the same dip around 80hz. Have you measured it alone?

The one sub in back is not enough to cancel the null created by your mains. You may want to try both subs in back, maybe stacked...?

Unless your mains are nailed to the floor, you should be able to get rid of the null produced by them. I understands aesthetics and all, but better response is better response.

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post #11612 of 11632 Old 09-12-2014, 01:24 PM
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Originally Posted by tommaazz View Post
HI. I was just playing the other day with rew and my laptop built in mic (i know i know ) ...i first calibrated again with audyssey xt32 and then i have done a rew measurement 10-200 hz and i saw a pretty big dip at about 30 hz...i have a sb12 nsd and a sb 13 ultra...so i played with sb13 ultra PEQ1 and set it at 31 hz Q 2,9 and level at -8 and then replayed the measurement....the dip was almost gone but...does that even make any sense? setting level at31 hz at -8 and getting a flatter response? It certanly is more impactful (have replayed some scenes) than with just audyssey setting but is that even possible? i am just curious (measurement was taken with FL FR and SW1 and SW2)
Does your AVR have SubEQ (will calibrate dual subs independently)? If so, and Audyssey got the distance for each sub right (rarely happens), they would be in phase. You sound like a good candidate for the sub distance tweak.
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post #11613 of 11632 Old 09-12-2014, 01:26 PM
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Originally Posted by HDgaming42 View Post
I am convinced I can localize the sub when set to a 200Hz crossover, but perhaps it's in my head.
IIRC, 200Hz is well above what ppl consider to be the cutoff for localizable subs. I read somewhere that the true non-localizable frequencies start somewhere between 50-80Hz, depending.

I felt that I could localize mine which were set to 110Hz. I moved them up front and have them as flanking subs to my mains (which are bookshelves). I'm loving them that way.

For multiple placement of subs, I use Gedde's method which is described here. Basically, place the first sub where you get the flattest response. Then place the second sub and adjust its level et al to fill in the nulls. My summary is probably wrong but you get the idea, I hope.

The really nice thing about the multiple subs placed according to Geddes is that you get a very flat response, bass decay is handled nicely and the subs end up with a geat deal of headroom. I was watching Cabin in the Woods and the explosions and landslides were incredible! The explosions in The Family actually scared me.

My focus is 2ch music but since I have these subs I feel compelled to get good boom out of them

Last edited by artur9; 09-12-2014 at 01:29 PM.
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post #11614 of 11632 Old 09-12-2014, 03:13 PM
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Originally Posted by artur9 View Post
For multiple placement of subs, I use Gedde's method which is described here. Basically, place the first sub where you get the flattest response. Then place the second sub and adjust its level et al to fill in the nulls. My summary is probably wrong but you get the idea, I hope.
Cool. Checking out your links now. Sadly the flattest response is with the sub placed well behind the MLP.

I have one good sub (17-200 +/- 3dB) and one cheapo sub (maybe 30-200 +/- 3db?). I'd like the good sub to be in the region where it's flattest (behind MLP), but that means easier localization (bass coming from behind you is really weird!). Perhaps the two papers will address this...
@Alan P : I'll try your suggestion to revisit moving the mains (and MLP now that its height is messing things up where I had it).
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post #11615 of 11632 Old 09-12-2014, 05:04 PM
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I didn't see in the guide what all the HDMI outs do under the preference screen. It says HDMI 1 is left, and HDMI 2 is right, but what are the rest? I know they are for other speakers, but without me having to go through all of them can someone list what they are?

Also.....how would I play more then one at a time? Like if I wanted to have both fronts and my subs on the same sweep?

If my AVR has true dual sub outs, will the sweep go through both at the same time?

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post #11616 of 11632 Old 09-12-2014, 05:20 PM
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Originally Posted by SeekingNirvana View Post
I didn't see in the guide what all the HDMI outs do under the preference screen. It says HDMI 1 is left, and HDMI 2 is right, but what are the rest? I know they are for other speakers, but without me having to go through all of them can someone list what they are?
Channel 1: Front Left
Channel 2: Front Right
Channel 3: Center
Channel 4: Subwoofer
Channel 5: Surround Left
Channel 6: Surround Right
Channel 7: Surround Back Left
Channel 8: Surround Back Right


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Also.....how would I play more then one at a time? Like if I wanted to have both fronts and my subs on the same sweep?
You can select two channels by setting the second channel as the timing reference. I don't think you can do more than 2 channels at once. Depending on how you have your speakers crossed over, if you play a full frequency signal, it'll engage the subs along with the other speakers for the low frequencies. I found that I almost never use Channel 4 to test the sub. Instead, I play the sweep on one of the other channels, and just turn off the amp going to my main speakers.

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If my AVR has true dual sub outs, will the sweep go through both at the same time?
Depends. Are they set up as stereo subs, or are they set up for a mono signal? The LFE channel should play out of both of them, but if you have them set up as stereo subs, redirected bass will play out of the left sub for the left channels, and the right sub for the right channels.
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post #11617 of 11632 Old 09-12-2014, 08:22 PM
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Originally Posted by AustinJerry View Post
If you do an internet search on bass resonance, bass ringing, etc., you will find a wealth of information that describes what it is, what causes it, and how it can be addressed. There are white papers on acoustics at the web sites of companies that deal in acoustics treatments (RealTraps, GIK Acoustics) that provide good information. Do some research--you will learn a lot.

As for whether you can actually hear the issues in the 40-50Hz range, only you can tell. My point was that the lower you go in the frequency range, the less frequent you will hear actual content there.

Using a mattress as a bass trap is certainly creative. I guess WAF is not an issue for you. Whether this improves the sound can only be determined by trying it. I suppose ringing would be somewhat lower in a padded cell.
Thanks - I'll do some more reading.

Regarding the 40-50 Hz question, I worded that badly. I really wanting to ask if those two dips should be noticeable?

Regarding the mattress, I was just trying to think of something that I already had at home that I could experiment with.

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Originally Posted by markus767 View Post
If the foam is open cell then it would be effective when placed in a corner. Most mattresses are closed cell foam though.
If you can blow through it easily with your mouth directly at the mattress then it's open cell foam.
If I can't think of anything better, I'll try it out.

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I guess I shouldn't try that with my waterbed, then.
I suppose it depends on how adventurous you want to get. Perhaps you are on the verge of discovering a whole new class of bass treatments

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Originally Posted by Alan P View Post
Notice that where Audyssey is boosting the dips is where the ringing gets substantially worse? You need to try (with placement, phase, distance) to get a flatter response pre-Audyssey. IME, the more EQ applied, the worse the ringing.

If you want to see something really disturbing check out your distortion graph, particularly those areas where Audyssey is over-boosting.
Being a beginner at this I'll probably first stick to trying to get a flatter response with less ringing
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post #11618 of 11632 Old 09-12-2014, 09:14 PM
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Originally Posted by Alan P View Post
Notice that where Audyssey is boosting the dips is where the ringing gets substantially worse? You need to try (with placement, phase, distance) to get a flatter response pre-Audyssey. IME, the more EQ applied, the worse the ringing.

If you want to see something really disturbing check out your distortion graph, particularly those areas where Audyssey is over-boosting.
Alan, it is true that applying Audyssey correction can affect both the distortion levels and the bass ringing. But it is not always significant, nor is it always a detrimental effect. Here are some measurements from my system. First, the distortion measurements:





Note the dip at 77Hz that Audyssey corrects results in a modest increase in distortion, from .6% to 1.1%. And Audyssey lowers the peak at 55Hz with negligible effect on distortion.

Next, the bass ringing (Decay) measurements:





If anything, Audyssey improved the bass ringing.

Not every installation is the same, so everyone should look at these measurements as part of the REW analysis. We should not, however, get in the habit of saying that Audyssey (or room correction in general) always makes distortion and bass ringing worse.
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post #11619 of 11632 Old 09-12-2014, 11:09 PM
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Originally Posted by Alan P View Post
Does your AVR have SubEQ (will calibrate dual subs independently)? If so, and Audyssey got the distance for each sub right (rarely happens), they would be in phase. You sound like a good candidate for the sub distance tweak.
Thanks for response...yes i have subeq ht..i saw this distance tweak and it seemed complicated when reading a guide. What it seems odd is that i put -8 level at 31hz and it shakes more? I dont know should i just leave at audyssey setting because i only have laptop mic and stop playing with rew because i dont know how accurate is this metod with built in mic which is not omnidirectional
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post #11620 of 11632 Old 09-12-2014, 11:17 PM
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Originally Posted by Alan P View Post
Makes sense if your sub is out of phase with your mains and you were measuring with your mains. Just the one sub, right?

That being said, any measurements you make with the internal mic can't be trusted in the least.


Ooops....just notice you have 2 subs. They are out of phase with each other!
Well.that makes sense as the svs said that sb12 and sb13ultra have different phase response and if they are far appart (mine are around 3.5m) the cacellation of the frequencies is less evident...so what should you do in my case? Should i just sell sb12 and have an ultra only? My room is around 1600 cubic feet and ultra is more than enough...but i can feel the difference with both subs playing.
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post #11621 of 11632 Old 09-13-2014, 04:14 AM
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Regarding the mattress, I was just trying to think of something that I already had at home that I could experiment with.
The Acoustic Treatment master thread might have some suggestions.

IIRC, garbage bags filled with material might be sufficient to experiment with. Just be careful not to place them where the shiny bags can affect the higher frequencies.
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post #11622 of 11632 Old 09-13-2014, 02:00 PM
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This is awesome, but what version of Soundflower are you using?

1.5.2 does not appear to play nice with Mavericks. I'm trying the 1.6.6 beta but so far it doesnt recognize an hdmi dongle on the displayport of my 2011 mac air.


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Sorry if this has been addressed before, but I couldn't find it after a few days of searching. I've worked out a way to individually select each of the 8 channels individually on a Mac, when outputting over HDMI. This is similar to the workaround in the sticky as it uses Soundflower (download here). I used the latest version, which actually has support for 64 channel input and output.

This is pretty straightforward once you have Soundflower installed and running. You need to go to System Preferences ->Sound -> Output, and set this to Soundflower (64 ch).



Go to the MIDI controller via Applications -> Utilities ->Audio MIDI Setup, and select Soundflower (64 ch) as the output. In the image I’ve set the volume for channels 7 through 64 to zero, but it’s not necessary.



Next, open REW, and go to preferences. Set your output device as Default Device.



Now go to Applications -> Soundflower ->Soundflowerbed. This should load the application. It looks like an asterisk in your menu bar. When you click on that, you get a drop down. Mouse down and select HDMI under the Soundflower 64(ch) section. Now, click the asterisk again, and mouse down to the SoundFlower (64ch) and you get another set of options under routing. This is where the magic happens. Mouse over and set channels 2 through 64 to None. This deactivates each of those outputs. We only need one active at a time.



To begin with, I just ran a test tone from the REW generator to experiment. Go back to the Soundflowerbed icon and hover over Soundflower(64ch), mouse over to Channel 1, and you can select which output channel you want to route the sound to. For example, HDMI (1) corresponds to my L channel, HDMI (2) corresponds to my Center, and so on. I tried it with all 6 speakers in my living room setup.



The key here is to have only 1 channel activated at a time. The OS wants to send the sound to all 6 channels (or 8) at once, but Soundflower will let you turn all of them off (or on) individually.

Hope this is useful! This worked for me on a MacBook Pro running OS X 10.7.5. I'll be interested to know if it works for others.

input Configuration Update

I've noticed an intermittent issue where my UMM-6 is not recognized by REW. My Mac will immediately recognize it, and typically swaps the input in the system preferences to the UMM-6, but for some reason, REW does not see it despite all the other settings being correct. For now, the work-around has been to select the "Built-in Input" in REW. I'm not familiar with the other mics/sound cards, but this is how it's setup on my Mac.

Go to System Preferences -> Sound and make sure you click on the Input tab



Make sure your mic is selected (e.g. highlighted). You can also go to the MIDI controller via Applications -> Utilities ->Audio MIDI Setup and double check that your particular input device is active. Look for the microphone beside it.



Now open REW and go to the preferences. Select the Soundcard tab and under "Input Device and Input" you can select "Built-in input"



What's interesting about this is sometimes REW will recognize my mic when "Default Device" is selected in REW, and sometimes it won't. I haven't figured out why this is yet, but you have to make sure REW is not defaulting to your laptop/computer's built-in mic.

Last edited by nathan_h; 09-13-2014 at 03:36 PM.
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post #11623 of 11632 Old 09-13-2014, 03:57 PM
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Originally Posted by nathan_h View Post
This is awesome, but what version of Soundflower are you using?

1.5.2 does not appear to play nice with Mavericks. I'm trying the 1.6.6 beta but so far it doesnt recognize an hdmi dongle on the displayport of my 2011 mac air.
AIUI soundflower etc is no longer required with REW 5.01 beta 21 and higher. Details in the thread on HTS.
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post #11624 of 11632 Old 09-13-2014, 04:09 PM
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AIUI soundflower etc is no longer required with REW 5.01 beta 21 and higher. Details in the thread on HTS.
Good to know. Ill try it without then. Thanks!

I was following AustinJerry's doc as precisely as possible and the latest edition, from last month, says it is required.
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Originally Posted by nathan_h View Post
Good to know. Ill try it without then. Thanks!

I was following AustinJerry's doc as precisely as possible and the latest edition, from last month, says it is required.
The Guide does not support using REW on a Mac. It only has a courtesy link to J_P_A's tips. As mentioned previously, if you want guidelines on how to use a Mac, check out the threads on HTS.

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post #11626 of 11632 Old 09-13-2014, 05:26 PM
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Quote:
Originally Posted by tommaazz View Post
Thanks for response...yes i have subeq ht..i saw this distance tweak and it seemed complicated when reading a guide. What it seems odd is that i put -8 level at 31hz and it shakes more? I dont know should i just leave at audyssey setting because i only have laptop mic and stop playing with rew because i dont know how accurate is this metod with built in mic which is not omnidirectional
Hello, I am very new to this REW myself and I tried to use the laptop's mic and it was not reliable at all, the UMIK is a very inexpensive tool to help with measurements. HDMI also is very convenient. I haven't taken a measurement yet as I procrastinate a lot and I'm taking my time as well and using Jerry's guide and so far all is working as planned, I just need to implement the tools I have and get moving along.
Cheers Jeff

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post #11627 of 11632 Old 09-13-2014, 05:36 PM
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Originally Posted by AustinJerry View Post
The Guide does not support using REW on a Mac. It only has a courtesy link to J_P_A's tips. As mentioned previously, if you want guidelines on how to use a Mac, check out the threads on HTS.
Fair enough.

According to the folks there, Soundflower is still required.

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post #11628 of 11632 Old 09-13-2014, 06:41 PM
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Originally Posted by artur9 View Post
The Acoustic Treatment master thread might have some suggestions.

IIRC, garbage bags filled with material might be sufficient to experiment with. Just be careful not to place them where the shiny bags can affect the higher frequencies.
Thanks - that does sound like a good suggestion. I was also thinking about using lots of pillows and a beanbag. Also thanks for the link - didn't realize the thread existed.
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post #11629 of 11632 Old Yesterday, 01:01 AM
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Fair enough.

According to the folks there, Soundflower is still required.
JohnM clearly states work arounds are no longer required but also says this is down to a new JRE so there is a working JavaSound setup on the Mac. This may mean 2 channel output only if it has the same capability as the PC version. It sounds like you're the pioneer here
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post #11630 of 11632 Old Yesterday, 07:34 AM
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Originally Posted by artur9 View Post
The really nice thing about the multiple subs placed according to Geddes is that you get a very flat response, bass decay is handled nicely and the subs end up with a geat deal of headroom. I was watching Cabin in the Woods and the explosions and landslides were incredible! The explosions in The Family actually scared me.
I think I've resigned myself to buying multiple subs. Reading Geddes papers it seems you only need one sub that goes low into the first mode region -- that I have, an SVS PB2000.

The more subs the better, assuming placement that maximizes their independence from one another. It seem in the front of my room I have a problem with nodes around 80Hz and 120Hz.

Can I get away with buying cheapo "garbage" subs if I'm getting 3 of them and placing them around the room? Using REWs room sim this would seem to pan out with my good sub at the rear, center of the room, and the other subs a) front corner b) alongside mains c) middle wall.

I can get a Polk Audio PSW108 for $100--perhaps $75 with a price match. I'm reading complaints about port noise starting at 45Hz. Could I use the miniDSP to create a crossover for these subs to roll off before it reaches this point, thereby taking their greatest weakness out of the equation?

Would this be a good way to fill those 80 and 120Hz nulls while leaving the "heavy lifting" to the SVS? Buying three of these at $75 each really seems attractive to me as I had not budgeted for a second sub at all...

My time is limited nowadays, and I'm not sure when I'll ever get back to making more traps, which I know would help as well...

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I'm guessing that the sub up front has the same dip around 80hz. Have you measured it alone?

The one sub in back is not enough to cancel the null created by your mains. You may want to try both subs in back, maybe stacked...?

Unless your mains are nailed to the floor, you should be able to get rid of the null produced by them. I understands aesthetics and all, but better response is better response.
I'm re-arranging my room based on a room sim and your suggestions. Just have to wait until I can blast the house with pink noise...
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post #11631 of 11632 Old Yesterday, 08:04 AM
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I'm no expert so please bear in mind that these are just off the cuff opinions. You know what they say about opinions being like ... ?

I'm hoping Markus will offer some input as he seems to know this sort of thing very well.
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The more subs the better, assuming placement that maximizes their independence from one another.
Exactly, assuming you have the space for them. I always get a kick out of the simulation that Harman did with 5000 subs. I wonder where the MLP was in that?

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It seem in the front of my room I have a problem with nodes around 80Hz and 120Hz.

Can I get away with buying cheapo "garbage" subs if I'm getting 3 of them and placing them around the room?
You can certainly get away with smaller subs but I'm not so sure about "garbage". At a guess, I would think that the cheaper subs would have significant distortions in key regions.

I don't know what your price is but I have a Mordaunt Short that I got from accessories 4 less and an Outlaw Audio M8 that are both pretty clean at the frequencies I'm using them. Reaction Audio has some bigger subs at attractive prices.

I'd be concerned that you'd end up with subs that you'd have to toss rather than resell.
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Originally Posted by HDgaming42 View Post

I can get a Polk Audio PSW108 for $100--perhaps $75 with a price match. I'm reading complaints about port noise starting at 45Hz. Could I use the miniDSP to create a crossover for these subs to roll off before it reaches this point, thereby taking their greatest weakness out of the equation?
I wouldn't think you're want to roll off that high. Some piano notes go down to 25Hz, more or less. My M8 goes down to about 35Hz easily and that works well enough.

Quote:
Originally Posted by HDgaming42 View Post

Would this be a good way to fill those 80 and 120Hz nulls while leaving the "heavy lifting" to the SVS? Buying three of these at $75 each really seems attractive to me as I had not budgeted for a second sub at all...
I think you do want subs that can handle the whole 25-120Hz range if you can. While you do tune them to different crossovers and levels I would think that a sub that can't reach <50Hz isn't going to help much.

You have 1 sub now? When I was in your position I waited and got good subs one at a time.

I started with the Outlaw Audio M8. That one by itself interacted so badly with the room that I didn't need REW to hear the problems. There were zero placement options that would work for the 2 money seats simultaneously.

Then I got a good deal on a pair of TBIs about a year/18months later.

In your position, I would spend the approx $250 on an Outlaw Audio or something similar.
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Quote:
Originally Posted by 3ll3d00d View Post
JohnM clearly states work arounds are no longer required but also says this is down to a new JRE so there is a working JavaSound setup on the Mac. This may mean 2 channel output only if it has the same capability as the PC version. It sounds like you're the pioneer here
Yeah it's interesting. No more workarounds required.... but everyone still uses the workaround.

Right now, I'm finding that the method for choosing a single channel via software is perhaps one of the main things to pay attention to.

Mike has as much confirmed that. Without the workaround, you can get a stereo signal. Period. The workaround can generate a complete signal on each channel. And the way one can get a single channel is......use the control settings for the system itself to mute all but one channel. Wish I was smart enough to automate that. It is going to take a very long time to iterate through EQ changes to each channel this way.

In any event, now that I've read the threads and posted the questions, and done the experiments, and we'll see what happens next. I'd really like to fix my response. I've got a lot of bass trapping (roughly ten OC bass traps) but still a wild waterfall in the bass region.

It is a bit tedious to have two separate forums, both owned by the same company (verticalscope), to work through, but I guess that's just historically how they have grown up.
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Last edited by nathan_h; Yesterday at 11:08 AM.
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