# M-Audio Transit and REW... a success!



## jagman (Jul 8, 2006)

So, I finally got sick and tired of SoundBlaster and ordered the M-Audio Transit. Although cheap, it was easy to implement, and I had REW plots in less than an hour. I spent probably 15 or so hours battling SoundBlaster... what a pain. Anyways... on to the good stuff.


This plot has 5 filters:









This plot has 9 filters:









That was just a quick attempt. I'll try and refine it this weekend!


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## JohnM (Apr 11, 2006)

The target level is too low on those plots, should be at least 80dB and possibly higher. Is the measurement of the sub alone? If so, is there any crossover active? The Target Settings should be set to correspond to the measurement, so if you were making a measurement of both the sub and a main speaker together (for example) the target should be set for a full range speaker as that is what the combination of sub+main should ideally achieve, if it is just the sub then the target crossover should correspond to the crossover being applied to the sub - if you are connected through an AV receiver it should be the receivers sub crossover setting, if directly to the sub or to the sub through a BFD it should be the sub's own crossover setting.


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## jagman (Jul 8, 2006)

It was set to subs but I hadn't pulled the wires from the mains. I realized that last night but it was late and I just wanted to get a couple readings before going to bed. The crossover within the AVR and REW are set to 80Hz. As you can see I have a massive null at 44Hz. I have the gain all the way up on the Samson S700. This way I don't have to boost frequencies with the BFD (except for the small amount in the mid 40's). I specifically chose to have the output calibrated to a little above the Target curve (that's my house curve). I like to have the lower bass around 5-10dB hot. I didn't get a chance to listen last night as it was a bit late, but I'll fine tune it to taste over the weekend. REW is a marvelous tool.


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## jagman (Jul 8, 2006)

I played around with the filters and came up with this (with the wires pulled from the mains):










I added a 6th filter for the low end. It sounds pretty good. Not sure about the trough at 132Hz. I'll at some point do a Hz by Hz measurement with the Rat Shack meter to see if I pick it up with the mains attached, but I don't feel like doing it now. I think I'll watch a movie instead .


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## jagman (Jul 8, 2006)

Guys... I've come across an epiphany. 

I tried "refining" my plot. I added 3 more filters that kept the same basic shape but made it considerably smoother. It looked much better. I saved it to a second set of filters in the BFD and switched back and forth. One would think the smoother curve would have also sounded better... not even close! Dynamics in the sub were shot. It sounded lifeless. I was shocked. The only thing I can attribute this to is excessive filtering. I am now a firm beleiver in limited use of EQ. Use what you can to give your basic shape you want, but _do not over use your BFD!_. Limited use is phenomenal... it makes the lower frequencies sound much better. But excessive use sucks the life out of your sub. I didn't realise it until now... too bad it took about a year to figure that out. Don't make the same mistake I made!


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## JohnM (Apr 11, 2006)

You need to get the target level set correctly, otherwise you are overcorrecting with your filters - they end up being a poor attempt at a level control instead of addressing the resonances they are aimed at. Try raising the target level to 85dB and generating some filters based on that. You are right about the filtering though, it shouldn't be overdone. Address the biggest few peaks and reassess.


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## jagman (Jul 8, 2006)

John.... 

Here's a plot with Wayne's house curve aimed at 81Hz:










Not bad for 5 filters... I'd like to get down to less but it's just not possible.


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## jagman (Jul 8, 2006)

Here's another with the house curve extended to 83dB:










I'm not sure this point whether I'll go with the 5 filter 81dB house curve or the 6 filter 83 dB house curve. The second may be a little risky with the low end boost. We'll see.


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## JohnM (Apr 11, 2006)

Using a house curve offset is not really the right way to go yet. Raise the target level using the control in the Target Settings, or use the "Set Target Level" action to let REW adjust it for you, then you will have a better picture of where the response lies compared to its nominal level before starting to apply filters. When applying filters it is best to align them with peaks on your plot, that way you are directly countering the room resonance that is lifting the response at that frequency. Have you tried letting REW find the peaks and optimise the filters?


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## jagman (Jul 8, 2006)

I haven't done it the way you suggested. I take you at your word because you obviously know what you're doing. I don't really get why raising the target level is better when REW is calibrated to pink noise at 75 dB. I would have thought it was best to set the target level to 75Hz since that would aim to make the full spectrum response flat, and from there, raise the low end with a house curve if desired. I don't understand how raising the target level changes the response within the room. Oh, and I have not allowed REW to set the curves. I'll try your suggestions and see what happens... I just don't understand why it is better.


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## JohnM (Apr 11, 2006)

The level at which REW was calibrated doesn't really matter, that process just allows REW to relate the size of the signal on its input to a corresponding dB SPL level so that it can draw the measurements at the right level on the graph.

The target level adjustment is used to set a reference where the response would lie if there were no resonance contribution from the room. It is something of a best guess, as it is very difficult to separate the contrubutions of the resonances from the underlying output of the speaker being measured. The target level can be set manually, looking at the response and estimating where it should lie, or by letting REW make its best estimate using the "Set Target Level..." option in the Target Settings - REW does it by generating a test signal and measuring its level, which may or may not be more accurate than using your own judgement.

The target level is important because the gains and bandwidths of the correction filters are adjusted to bring the measurement on to the target line. The filters should be countering the effects of the room's resonances, if the target level is too high the filters would be taking out too little of the resonance, if it is too low they take out too much. 

This process is a bit too manual at present, I'll be looking at providing further automation and more accurate determination of the contributions of the room's resonances and the best filter settings to counter them in a forthcoming release. That will also include features to automatically determine the settings for filters that shape the response to bring it to a preferred characteristic, such as a desired house curve.


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## m-fine (Aug 4, 2007)

I think you are missing the point.

You raise or lower the target level to select the best filters to get the subwoofer SHAPE the way you want it with minimal EQ. Once the sub shape is as desired it is a simple matter to adjust the output level on the receiver, EQ, or the sub's amp to set the output level relative to the mains.


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## jagman (Jul 8, 2006)

m-fine said:


> I think you are missing the point.
> 
> You raise or lower the target level to select the best filters to get the subwoofer SHAPE the way you want it with minimal EQ. Once the sub shape is as desired it is a simple matter to adjust the output level on the receiver, EQ, or the sub's amp to set the output level relative to the mains.


How is that different than creating a house curve manually. In my case, I had the target curve set to 75dB, but added a house curve that deviated from the original. There is a linear 8dB increase (on the log chart) from 60Hz to 30Hz. It then stays flat at 30Hz below that. I've created the shape that I wanted while only using 5 filters. Isn't that the point?

Edit: I forgot to put in a new graph I did last night. It's a little different than the one above. I also moved the seating position back to try and alter the low end and trough at 44 Hz. It did a pretty good job at both:


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## m-fine (Aug 4, 2007)

I think what Jonh was trying to tell you was to make one house curve and then adjust the level up and down with the target level adjustment. Yes you can change the house curve to achieve the same thing but that is a lot of work. The 75 db target starting point is completely arbitrary at this stage of calibration. 

Once you have your filters set, you can put the target level back at 75 (and not have to adjust your house curve) and then adjust the subwoofer level on your electronics until the sweep best matches your target.


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## brucek (Apr 11, 2006)

Others have tried to make this point, but you haven't really taken the advice to heart, but the fact is, you're using the BFD as a level control for your sub. 

A big clue is that your target (even with an exaggerated house curve) doesn't touch the uncorrected response, and at its worst you require -30dB filtering.









brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hi Krister,

It looks to me like there’s been something of a "breakdown in communication" here.

From what I can see, based on your posts above: (a) you’re trying to avoid any boosting filters, and (b) you have a highly-capable IB system with two 18" drivers, (which you mentioned in your PM to me, but I don’t think here, so this is news to John, brucek et. al.). 

From what I understand this is a fairly typical response for an IB, being "weak" on the low end, coupled with excessive upper-bass energy (at least I think that’s correct – the guys at our DIY Subwoofer forum could qualify that).

So - no two ways about it, the levels below 30 Hz needs to be boosted, and the levels above 30 Hz need to be reduced. 

Taking to heart all the stuff you’ve no doubt seen about "boosting is bad," you’ve cut everything _above_ 30 Hz to avoid boosting _below_ 30 Hz. But notice in your graph what the others have pointed out, the difference in _overall level_ between your baseline vs. equalized response. Equalized response is nearly 15 dB lower at 35 Hz. 

So, what’s going to happen when you fire your full system back up? You’ll find that the subs now sound really weak compared to the mains (you’ve noted that you like the subs 5-10 dB hot). So, you naturally raise the sub level up to compensate. 

To get what I’m talking about, mentally move your equalized Target Curve line up to 95 dB, where the unequalized peak at 35 Hz is. That's about where your sub level will end up once you turn them back up to reclaim the lost volume. Of course, you can see that _you’ve succeeded in boosting down low,_ even though you used only cutting filters.

So you see, in the end boosting or cutting is often academic: If you had sagging response below 30 Hz before, and now you don’t, then you’ve boosted up the sagging area. It’s as simple as that. It doesn’t matter which way you accomplished it, by boosting it outright, or by cutting everything else and then raising the sub volume, the end result is the same. Does that make sense?

Now, with that in mind, let’s take a look at REW and its role in equalization. As we’ve established, you’re going to have to re-adjust your sub level after you equalize to get the correct blend with the mains. So all the levels and stuff you set up in REW before generating the sweep tone, that’s merely for the program’s sake. Once you’re done equalizing, your system levels (including the subs) are going to be adjusted up or down depending on whether you want things quiet or blasting. 

Therefore, the purpose of the Target Curve is merely _for the sake of properly equalizing_. That’s why John, brucek and the others have been encouraging you to re-align it up in range of your base response curve. By keeping it low, yes you’ve successfully flattened response, but you’ve also accomplished wholesale gain reduction. 

_Normally_ this isn’t a good thing (as I noted under the “Compelled to Excess” heading of the Hard Knee article, near the bottom of the first post). But in your case things may be different (I’ll get to that shortly). The reason brucek and John et. al. have been encouraging you not to cut gain so much with the equalizer is that we’ve seen cases where people cut so much that they didn’t have enough signal left to drive their sub amp! No kidding, they couldn’t even get a reading on the amp’s meters!

So – back to your graph: If flat response all the way down to 15 Hz is what you’re after, you’ve accomplished it, as long as you have enough of a signal left to drive your amps to max (or at least get the volume levels you need). It’s unfortunate that it took cutting 30 dB at 100 Hz to accomplish it, but if that’s the before-EQ response you have to work with _with your crossover engaged_ (it is, right?), then so be it. 

As noted, I think the significantly high levels of upper frequency energy you have is not uncommon for an IB. Raising the Target Curve (as would normally be done) will require some boosting below 35 Hz, but the lowest filter setting on the BFD is 20 Hz. So, equalizing “correctly” with a re-adjusted Target Curve may well result in response sagging below 20 Hz, instead of being flat down to 15 like it is now. It’s up to you to decide if that’s acceptable or not.

So, don’t worry about boosting, if you feel you need to raise the Target Curve and try again. It’s only an issue if your sub drivers and amplifiers don’t have enough headroom to handle it. You’ll find out soon enough if that’s the case. Anyway you cut it (no pun intended), when you’re done equalizing, the depressed areas _will be raised,_ so _any_ equalization will place additional demands on your system. Therefore, you have to have enough headroom going in.

Regards,
Wayne


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## jagman (Jul 8, 2006)

Thank you for the very thorough reply. What you are saying makes sense. I am surprised how much upper bass the IB puts out. I'll try raising the target level and work with the amp gain to find a nice compromise. One of the issues I have is my integrated amp has a non-adjustable crossover at 80Hz. I plan on getting the Sherwood/Newcastle R-972 receiver after it's release, so I will be able to adjust the crossover down a bit. I think I'll end up crossing it over around 60Hz or so... that should help tame the upper bass a bit without the use of EQ. We'll see.


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## m-fine (Aug 4, 2007)

You could also benefit from a step up in EQ that allows a low shelf filter such as the DCX2496 or a QSC DSP30. If you put a 6-8 db low shelf boost at 20 hz it will level out the region from 30 on down. You can't do much with positioning the IB to solve the 44hz dip but you did say moving the seats helped, and maybe a small boost in that region paired will smaller cuts on either side will flatten that area. You could also setup a low pass at 80-100 on the DCX until you get a receiver with a 60hz crossover option.

That should give you good results with just 3 PEQ's a low shelf and crossover. You may even be able to do it with just 2 PEQ's.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Another option would be to get an analog pro-audio electronic crossover and install it in front of the Behringer EQ. I think this would work better than shelving. A shelving filter will only drop and then flatten the level by the amount you cut it, not infinitely like a low pass filter will. The crossover will also have level controls to maintain a good signal for the EQ and amps downstream. An ouboard crossover would also allow you to keep an 80-90 Hz setting on your receiver for your main speakers, which you probably want.

The Behringer CX 2310 is probably ideal for you. It has a dedicated subwoofer output that you can set as low as 10 Hz. So you can set in anywhere you need to tame those upper frequencies. You could even cascade the mains low pass on top of it, if needed, for additional upper bass signal reduction. You can find the 2310 for pocket change on eBay.

Regards,
Wayne


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## jagman (Jul 8, 2006)

Thanks guys... that may do the trick. Some major networking issues came up at work today so this will have to go on the back burner until next week. I'll think about it and keep all of the recommended equipment in mind. All of you have been very helpful.


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## m-fine (Aug 4, 2007)

Wayne A. Pflughaupt said:


> Another option would be to get an analog pro-audio electronic crossover and install it in front of the Behringer EQ. I think this would work better than shelving.


I think you misunderstood what I was saying. I get the impression the OP wants to boost the sub 30 hz output well below where the BFD can help with a PEQ because his IB should be able to offer more extension than he is seeing now. This is where the low shelf with a boost can help him. This is independent of his issues in the 60 hz plus range.

The second issue is he may benefit from a low pass crossover set higher up because the receiver does not seem to be doing it's job or his IB is way too sensitive in that range. I guess he could use the cx 2310 upstream of the BFD to solve that problem, but the DCX is a very good crossover (DCX = Digital Crossover) with PEQ and shelf filters all in one box. 

If his receiver's low pass on the sub out is faulty, he can correct for that on the DCX assuming the high pass for the mains still works. Obviously the receiver is redirecting bass content to the sub or he would not have been able to get the graph he did. If the receiver is really toast and is sending full range signals to both the mains and the sub, he could also make use of all three inputs on the DCX and run the pre-outs for left and right into 2 channels and the LFE into the third. The bass from all 3 can be sent to the sub and the upper frequencies can be sent to the amp inputs for the mains (if his unit has amp inputs or he uses and outboard amp). Even though it could be done, and that is the type of thing the DCX is designed for (in pro use) I would still replace a receiver that is that faulty as soon as budget allows.


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## Wayne A. Pflughaupt (Apr 13, 2006)

m-fine said:


> I think you misunderstood what I was saying. I get the impression the OP wants to boost the sub 30 hz output well below where the BFD can help with a PEQ.


You’re right, somehow the fact that you suggested _boosting_ below 30 Hz with the shelving filter got past me. Sorry. :duh:

Regards,
Wayne


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## jagman (Jul 8, 2006)

The issue I'm fighting is the natural roll off of a sealed enclosure. The IB is a LARGE sealed enclosure, and due to the large displacement, it is fully capable of reproducing 10Hz and up. The problem is the lower bass is not nearly as loud as the upper bass.


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## m-fine (Aug 4, 2007)

jagman said:


> The issue I'm fighting is the natural roll off of a sealed enclosure.


I think that is one of your issues, but if you have an 80hz crossover in effect, the graph shows something is wrong in the 80-140 hz range and that is going to be WAY more audible than your 10-30hz levels. It could be that receiver is not filtering properly, the IB is too sensitive, or the room is adding a lot of gain at that spot, but no matter the cause you do need to correct it 

BTW, I have a sealed sub with dual 15's in a 3800 cuft room that is fully capable down to 10 hz and below so I know what you are looking to do should definitely be achievable with the IB, you just need to get the signal levels adjusted properly without boosting or cutting to the point where you clip the amp input or have too weak of a signal to amplify. 

One other point of caution. If you do low shelf the stuff below 30, it will be boosting all the way down to the 3-5 hz range where the response of your electronics will likely roll off very quickly. I am not an IB expert by any means but with such a large enclosure, I think you may have to be worried about supper low content in the 5-10hz rang bottoming out the drivers even if you are not getting much usefull output. You may want to put a steep 10 hz high pass in the loop somewhere to help protect them. Unfortunately I don't know of any DSP product that can do that for you that low so you may want to look into building a simple passive circuit. Better yet, ask the IB experts what they do.


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## jagman (Jul 8, 2006)

Your point about what's going on in the 80-140 Hz range concerns me, too. The unalterred output in the most recent graph has peaks and dips that coincide with what is predicted given the room's dimensions (20' x 16' x 9'). The problem is it is behaving as if it is getting a full bandwidth signal. What I don't get is why it doesn't trail off above 80Hz. The response behaves as if the integrated amp is not applying low pass filter at 80 Hz.


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## jagman (Jul 8, 2006)

BTW, I don't want to artificially boost below 20Hz. The sub is plenty capable of output down low and I'm already worried about bottoming the subs out. My concern is getting more lower bass output than upper bass output without having to do extensive EQ. Having a lower low pass filter (e.g. 60 Hz instead of 80Hz) would probably help.


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## jagman (Jul 8, 2006)

I tried adding 5 Ohm 113 watt resistors to the positive lead as per another thread. I know it is contraversial, but it dropped ULF output considerably (mostly below 15Hz and especially below 10Hz). It also dropped output some above Fs. I definitely believe it will protect the subs from overexcursion, but I don't know if I like the sound better. It's always about trade offs. Since they were cheap, I figured I'd give them a shot. At this point I don't know if I want to keep them in the system or not. 

Anyways here are the plots. Sorry the first has extra lines in it.

75dB Target with 8dB Hard Knee House Curve:











81dB Target with 8dB Hard Knee House Curve:










Obviously with the second the gain on the amp needs to be reset. I haven't had a chance to listen yet but I'll play with it and see how it goes. The level going to the sub amp should be higher. 

John and Bruce... is the second plot more at what you guys want me to do?


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## brucek (Apr 11, 2006)

> is the second plot more at what you guys want me to do?


Yep..........


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## brucek (Apr 11, 2006)

jagman, 

one of the plots above was the only time you included a soundcard cal line. This card looks interesting to me as a future purchase (I want a laptop in the near future). How does the soundcard response look down to 10Hz and up to 20K - pretty good?

I also wondered about the dual purpose analog/digital input port that accepts both analog line-in and digital S/PDIF in, and is switched and accomplished by a 'mini-optical adapter'. When it's plugged in it allows the connection of optical S/PDIF digital input. Does this seem like it's well done? Is the adapter positive when it plugs in?

brucek


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## imbeaujp (Oct 20, 2007)

Hello, 

M-Audio seems to have great sound cards. I just bought the FastTrackPro (with midi and phantom mic input) and did some test with the unit. You can read the thread HERE.

JP


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## jagman (Jul 8, 2006)

Bruce,

I've only used the analog line in and line out (for REW) so I cannot comment on the S/PDIF digital input. I read several reviews before purchasing it and generally speaking the reviews were positive, but also mixed. People have reported pops in their speakers during playback, but have also said those noises are typical of USB external soundcards. I heard them this morning for the first time. I can tell you it is much easier to use for REW than SoundBlaster. The driver that comes with it is outdated... you have to download the current on from their website, but other than that it's a piece of cake. I'm using my PC right now but I'll post a full bandwidth plot of the soundcard cal line when I'm on the laptop. For the money, I'd say it's pretty hard to beat.

Hope this helps,

Krister


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## jagman (Jul 8, 2006)

Here's the plot of the soundcard:


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## brucek (Apr 11, 2006)

Thanks Jagman, looks good....

brucek


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## m-fine (Aug 4, 2007)

That looks sufficiently flat from 7-20K!


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## edwinauer (Dec 27, 2007)

Hi Jagman,

Are you using the Transit with a SPL meter connected? 
Im asking because it seems my Transit gives a 5V power signal (Line-in doubles as Mic-line) to the SPL meter which makes it impossible to make good measurements with it. It's a RS analog btw.

Anyone has any ideas if its a setting or other problem?

Thanks!

Edwin


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## brucek (Apr 11, 2006)

> Im asking because it seems my Transit gives a 5V power signal (Line-in doubles as Mic-line) to the SPL meter which makes it impossible to make good measurements with it. It's a RS analog btw.


I doubt that's the problem. The RS meter would be AC coupled and as such the capacitor would block any DC from affecting the output.
Were you able to get a good soundcard cal file?

brucek


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## JohnM (Apr 11, 2006)

The bias output on a mic input will cause the RS analog meter to be driven to its end stop. On a mic/line input there would normally be auto-sensing of the impedance of the connected source though, so shouldn't end up with that problem. Also the bias is usually on just one of the inputs, so could try the other but if the soundcard is treating the input as mic there will be too much gain anyway.


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## mojogoes (Feb 11, 2008)

Quote....



Here's the plot of the soundcard:




--------------------------------------------------------------------------------





Well done it looks just fine.....i was going to going with this same unit but at the time couldn't Wait for someone to do what you have done........but i think this 3 in 1 unit is very good.....it sells for £60/£70 new on british ebay at the moment.


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## brucek (Apr 11, 2006)

> The bias output on a mic input will cause the RS analog meter to be driven to its end stop. On a mic/line input there would normally be auto-sensing of the impedance of the connected source though, so shouldn't end up with that problem. Also the bias is usually on just one of the inputs, so could try the other but if the soundcard is treating the input as mic there will be too much gain anyway.


Huh, that surprises me John. I thought the RS meter would block the bias (assuming it's even present when a low impedance line level device is plugged in).

The M-Audio Transit is quite a nice USB device (I consider buying one myself). 

It has a single 1/8" (3.5mm) input jack that is a triple purpose jack for (S/PDIF 1/8” mini digital Optical In or 1/8” mini Analog Mic/Line In) depending on what it senses at the port. The Optical widget switches the port to digital, but when it is unplugged, I assume the low impedance analog RS meter would then shut down the +5v bias. But if it didn't, why would it cause the meter to be driven to it's extreme? Would the coupling capacitor (that I've witnessed in schematics) not block this?.

brucek


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## JohnM (Apr 11, 2006)

I don't have the schematics to hand but I have seen what happens to the analog meter when plugged into a PC mic input. The bias shouldn't be there when a line source is connected though.


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## edwinauer (Dec 27, 2007)

Hi,
Well what I can see is that the moment I connect the Transit to the SPL, the SPL meter gives some, rather high, reading and continues doing that (without any real sound at that moment). I have two SPL's so I checked them both, same thing. After disconnecting the Transit ... reading is gone too.

Is this normal, or is it a problem with the Transit?

Thanks!
Edwin


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## brucek (Apr 11, 2006)

> what I can see is that the moment I connect the Transit to the SPL, the SPL meter gives some, rather high, reading and continues doing that (without any real sound at that moment). I have two SPL's so I checked them both, same thing. After disconnecting the Transit ... reading is gone too.
> 
> Is this normal, or is it a problem with the Transit?


It would indicate consistency with our discussion that the M-Audio device continues to output the DC even when a line-level device is plugged in and that the RS meter does not block the DC bias. Kinda weird. I don't know what to think. I wish someone with this device would comment on their experience.

brucek


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## JohnM (Apr 11, 2006)

Does the same happen on both left and right inputs?


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## brucek (Apr 11, 2006)

I assume you used a *stereo* connector plug at the mic/line in jack?

This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........

The RS meter would connect to the right channel and hopefully the Transit device would see this low impedance line device and shut down the DC bias.......

brucek


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## jagman (Jul 8, 2006)

brucek said:


> I assume you used a *stereo* connector plug at the mic/line in jack?
> 
> This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........
> 
> ...


That's what I did with very usable results.


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## edwinauer (Dec 27, 2007)

brucek said:


> I assume you used a *stereo* connector plug at the mic/line in jack?
> 
> This would be the same situation as at the line-out connector where you need to use a stereo 1/8" connector that breaks out to left and right channels........
> 
> ...


Yes, i'm using a stereo 1/8" connector which splits in 2 rca type connectors. I've been trying to get a new soundcard calibration and for some reason, when the 1KHz is playing, the detected signal is alternating between left and right channel. Few seconds left channel and then a few seconds right channel, very odd. I'm going back to testing and will let you all know how the results are. I'll test both left and right channel if I come that far.

Edwin


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## edwinauer (Dec 27, 2007)

After disconnecting and resetting everything ... im getting a good soundcard calibration again. 

So i've connected the SPL and checked both channels. On both channels there is DC present and the Transit doesnt adjust itselve on any of the channels onder: Not sure what to try next ... any ideas?

Jagman, what type SPL did you use? I've tried 2 analog RS types, did you use a digital one?

Edwin


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## brucek (Apr 11, 2006)

> So i've connected the SPL and checked both channels. On both channels there is DC present and the Transit doesnt adjust itselve on any of the channels Not sure what to try next ... any ideas?


Well, I contacted M-Audio and they got back to me on this issue. They indicated that the USB Transit card provides 3.3 volts DC on the line-in jack to power electret mics. There is no way to remove this DC voltage and is always present irregardless of the connected device. They indicate that this normally isn't a problem, but can be on some devices and so check with the manufacturer.

Well, that sure doesn't work for me. I was going to purchase one of these for my new laptop, but not anymore. I would normally just take the device apart and disconnect the voltage, but some units today are quite difficult to seperate without damage.

I tested the Radio Shack meter with 3 volts DC on the output (as a test) and indeed the meter pegs, so it's probably not a good idea to use this card with the Radio Shack meter.

Then again, with the problems I've read from other posters with regard to Vista and the Soundblaster Live card, I don't know if I want to go down that road either.....

Mmmm, which card to buy.......

brucek


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## jagman (Jul 8, 2006)

I have the new(er) RS digital SPL meter. I had all sorts of problems with another soundcard on a different computer, but the M-Audio Transit has been remarkably easy and repeatable to use. Good luck getting your setup to work properly.


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## edwinauer (Dec 27, 2007)

OK, nice. I was hoping you were using a different type SPL meter 
I'll check for a digital RS type. Can you post which type you have? 

The soundcard itselve seems to be high quality, so I rather use a new spl meter.

Thanks,
Edwin


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## kjgarrison (Nov 17, 2007)

I have just read through this thread, and as a builder of an IB myself I am very interested in the problems encountered and solutions offered here.

I have taken a few preliminary REW measurements of my IB alone and noticed that it does have what I didn't previously realize to be a feature of IBs, namely higher frequencies with basically minimal fall off up to 200, even 250.

I'll be posting my own thread and asking for help when I get all the "settings" figured out, or maybe even *to* get the settings figured out.

But for this particular thread, I have a dumb question. Why is anything the IB does above the crossover selected in the AVR an issue? I'll risk a dumb answer and take a stab at answering my own question, too (just came to me as I was typing.) Is the reason that the AVR assumes a "typical" (and steeper) rolloff as would be expected with ordinary subwoofers, but instead gets full performance from the IB all the way up to ... who knows 250hz, resulting in an excess summation of IB and mains? If this is correct then are crossovers with IB subwoofers only half effective and half way like having LFE+Mains selected?


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## jagman (Jul 8, 2006)

I can't answer your question because I just don't know. You're answer seems reasonable.


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## brucek (Apr 11, 2006)

> Why is anything the IB does above the crossover selected in the AVR an issue?


I don't understand the question. An IB is no different than any other sub. The object is for the sub to track a target level that corresponds to the output of the receivers crossover setting. The room causes the sub to misbehave in that regard, so EQ is added. Why do you feel an IB is any different?

brucek


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## kjgarrison (Nov 17, 2007)

brucek said:


> I don't understand the question. An IB is no different than any other sub. The object is for the sub to track a target level that corresponds to the output of the receivers crossover setting. The room causes the sub to misbehave in that regard, so EQ is added. Why do you feel an IB is any different?
> 
> brucek


Wayne said it .. maybe in post 16 ?


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## brucek (Apr 11, 2006)

> Wayne said it .. maybe in post 16 ?


You've mis-understood what his point was, along with all the other people who were trying to tell the OP that an IB, like a sealed sub may require low end EQ gain. This isn't gain thrown at a modal dip, but EQ for the bottom end. The OP decided that the answer was to drive the overall gain 30dB high, and then cut everything but the bottom end. A poor decision.

IB's, like any sub should track the crossover that the bass management crossover provides.

brucek


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## kjgarrison (Nov 17, 2007)

I surely did misunderstand. Thanks for the clarification. Of course it makes sense that the IB basically has to follow the -24dB/octave rolloff of the AVR's bass management system. (I'm assuming 24, since that is what my AVR does.)

You can tell I'm a noob. :sad:

But I'm working on it. :reading:

Thank you.


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