# How do I measure, and then remeasure?



## lovingdvd (Jan 23, 2007)

Here's a scenario. I take a measurement, tell REW to Find Peaks and optimize them. Then I add a few filters to tighten things up a bit. So far so good.

Now at this point I want to run a measurement and see how the actual results are compared to REW's estimated results.

So I copy all the filters into my BFD. At this point I click on the Measurement button again, and now I get a new graph showing the results from my filters.

Now here is where I am getting lost... At this point assume I need to make some further tweaks. But this new Measurement does not have any knowledge about the filters from the last Measurement. I can add a few new filters but they are independant of what I'd done previously. 

So at this point it cannot optimize the filters any longer (since it has no knowledge of the first set of filters). I repeat this process until I have things correct, remeasruing as necessary. But now I have say 5 different Measurements each with their own set of filters, together which makes the complete set of filters.

I guess what I am looking for is a way to Remeasure but within the same graph. In other words, instead of Measure creating results in a new graph, I'd like it to retain the previous filters and "Re-measure" within the same mdat. Is this possible? Seems like there should be a Remeasure button. What am I missing?

Thanks.


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## cyberbri (Apr 27, 2006)

When I do it, I switch between the Left, Right and Sub tabs on the bottom right. So I'll maybe do a no-BFD reading on the sub tab and try out filters. Then switch to Left or Right and take a reading with the filters and compare it to the Sub tab's original measurements and predicted results for the filters. 

I think there's a way to save data and recall it, but I haven't done any of that yet.


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## lovingdvd (Jan 23, 2007)

cyberbri said:


> When I do it, I switch between the Left, Right and Sub tabs on the bottom right. So I'll maybe do a no-BFD reading on the sub tab and try out filters. Then switch to Left or Right and take a reading with the filters and compare it to the Sub tab's original measurements and predicted results for the filters.
> 
> I think there's a way to save data and recall it, but I haven't done any of that yet.


Thanks I didn't know those tabs were there. I'll have a look. However does this give you multiple tries within the same "document" or is it just an easier way to flip between mdats?

Yes I see the option to export the filter data, but there is no way to Import it that I can find into another mdat so it needs to be retyped every time I take a new measure....


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## cyberbri (Apr 27, 2006)

It just lets you view different graphs while keeping the original with the filter suggestions in place. I found that the filter predictions weren't very good in my case, so it let me keep the original and the filter suggestions, plus take 2 more separate graphs and compare them all.


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## brucek (Apr 11, 2006)

> Thanks I didn't know those tabs were there.


They're not - that was in old versions. They have been replaced completely in Version 4 with a better method....



> Yes I see the option to export the filter data, but there is no way to Import it that I can find into another mdat


Load and Save filters....... easy. Export is only to get a text format.

brucek


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## adogand6kids (Jul 29, 2006)

So I'm looking around the new REW v4 and I can't figure out how to measure and then re-measure if there are not separate channel tabs? Did I misunderstand what BruceK was saying about there being a better way? Am I missing a help file that explains how to set a filter then check the effect of that filter... what lovingdvd posted initially?


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## brucek (Apr 11, 2006)

> I can't figure out how to measure and then re-measure if there are not separate channel tabs?


The best thing would be to read the REW HELP  files. They're quite well written.

Each time you hit measure it creates a new set of measurements and keeps the last set too. You can keep 9 sets at once.



> Am I missing a help file that explains how to set a filter then check the effect of that filter...


It's all in the help file..

brucek


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## cyberbri (Apr 27, 2006)

I'll have to see what version I'm using, then. I only downloaded it just a few weeks ago...


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## brucek (Apr 11, 2006)

> I only downloaded it just a few weeks ago...


REW V4 just became available on Monday... You're in for a surprise...... it's quite nice.

brucek


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## cyberbri (Apr 27, 2006)

Let me ask a question of my own, since my own thread died without any answers.

Besides measuring frequency response, what else can REW be used for? I know there are the waterfall charts, etc., but how can they be used to analyze and evaluate room acoustics, ringing, etc.? Ie., if I want to see what adding bass traps has done for my room/response besides just changes in frequency response, what can I do and how do I do it?

Is there an advanced REW guide?


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## lovingdvd (Jan 23, 2007)

brucek said:


> The best thing would be to read the REW HELP  files. They're quite well written.
> 
> Each time you hit measure it creates a new set of measurements and keeps the last set too. You can keep 9 sets at once.
> 
> ...


I have read the help files from start to finish and they are excellent. However in practice there are many questions that come up that are not addressed.

You mentioned that each time you hit measure it crease a new set of measurements and keeps the last set too. But in the new Measurement there are no filters? So are you supposed to save the filters and then reload them in the next measurement? Why not just have them carry forward?

Better yet, it would be great if there was a REmeasure command where it just overwrote your last measurement but kept all your filters and settings and so forth.


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## cyberbri (Apr 27, 2006)

lovingdvd said:


> Better yet, it would be great if there was a REmeasure command where it just overwrote your last measurement but kept all your filters and settings and so forth.


There isn't that option? I haven't upgardet to V4, but in the previous version I could take a measurement, apply filters in REW, and if I took another measurement it would overwrite the previous one but keep the filters and apply them to the new graph.


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## lovingdvd (Jan 23, 2007)

cyberbri said:


> There isn't that option? I haven't upgardet to V4, but in the previous version I could take a measurement, apply filters in REW, and if I took another measurement it would overwrite the previous one but keep the filters and apply them to the new graph.


I'm very new to REW (just started working with it a few days ago) so I'm hesitant to say definitively 'No' - however I can't find a way to do what you say and that's the whole purpose of this thread - I want to do just that but don't see how.


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## cyberbri (Apr 27, 2006)

That'll suck if it's been taken out...

I'll have to install V4 in a different location, just in case. 
I can possibly post the previous version's install files. 
I should still have them on my computer.


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## brucek (Apr 11, 2006)

> You mentioned that each time you hit measure it crease a new set of measurements and keeps the last set too. But in the new Measurement there are no filters? So are you supposed to save the filters and then reload them in the next measurement? Why not just have them carry forward?





> I want to do just that but don't see how.


Seriously, how long does it take you to click two selections?

Click - Save Filters
Click - Load Filters.

It took me longer to type that, than it would for you to click it...... I suppose it could have been incorporated into a single button, but it wasn't. 

It's two clicks.............

brucek


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## Otto (May 18, 2006)

lovingdvd said:


> You mentioned that each time you hit measure it crease a new set of measurements and keeps the last set too.


Well, I've only played with 4.0 a couple times, but I think that's correct. There are a total of nine measurements -- they're along the left side of the GUI. So, if you measured once, your measurements are in window #1; measure again, in window #2, etc. If, on your second measurement, in window #2, you determine some filters and apply them to the BFD, that information is saved in window #2 (at least temporarily -- you have the option to store it more permanently by selecting the File->SaveFilters option (or similar)). 

OK. So you did measurement #2, downloaded them to the BFD and you're ready to do measurement #3. So you do that, and you get the result of whatever filters you had applied previously. The filters from #2 are not there. And you're right -- they don't really "carry forward". 

However! They are still preserved in #2, and it's easy to go back there to continue to tweak those filters. Now, you can also go to the "All measured" tab and select which measurements to view. That way you can see #2 and #3 at the same time.



> Why not just have them carry forward?


I agree that there should be an option.


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## lovingdvd (Jan 23, 2007)

Otto said:


> I agree that there should be an option.


Yes, that seems logical. After all the second measurement is based on filters from the first, and so forth. Having the filters automatically "stick" between measurements would really help streamline the experimentation.


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## Dent (May 6, 2006)

But if you save the filters from the first measurement and then load the filters into the second measurement (or if the first measurement filters were automatically carried forward) then you would be then *applying* these first set of filters on to the new measurement. Since the new measurement already has the first set of filters applied (because you entered them into the BFD) that would be the same as doubling up all of your filters which would throw everything out of whack.


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## lovingdvd (Jan 23, 2007)

Dent said:


> But if you save the filters from the first measurement and then load the filters into the second measurement (or if the first measurement filters were automatically carried forward) then you would be then *applying* these first set of filters on to the new measurement. Since the new measurement already has the first set of filters applied (because you entered them into the BFD) that would be the same as doubling up all of your filters which would throw everything out of whack.


Yes, of course. Doh!


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## Otto (May 18, 2006)

Dent said:


> But if you save the filters from the first measurement and then load the filters into the second measurement (or if the first measurement filters were automatically carried forward) then you would be then *applying* these first set of filters on to the new measurement. Since the new measurement already has the first set of filters applied (because you entered them into the BFD) that would be the same as doubling up all of your filters which would throw everything out of whack.


Well, not quite. If I measure with filters assigned from measurement #1, I now have measurement #2. If filters carried forward from #1 to #2, they are just there for me to download again, or not. If I download the same filters, I will get the same result as I did in #2, because they are the same filters.

Now, if the filters carry forward, and you tweak them a bit, you will get a different result than you did in #2. Still, you should only get a delta in the areas you tweaked, and there won't be a doubling up because you only made small changes. This is how I do it, and I've tweaked quite a bit when trying to boost below 20 Hz without getting unwanted peaks _above _20 Hz.

I think what we may really want is for REW to "know" which filters are in the BFD and then calculate new filters "on top of" the current filters. REW would then be doing the tweaking for you. The problem is that REW doesn't really have a way of knowing what filters you are using. In these cases, we could assume that it's the filters from the previous measurement, but that wouldn't always be true. Suppose I have already set up filters in banks 1 and 2 of the BFD. Now I just want to see the difference between the two and I do a couple measurements using REW. As far as I know, without loading saved filters or somehow reading them from the BFD, REW has no way to know what filters are in banks 1 and 2. Even if REW could determine the filters being used, I think I'm over-complicating things at this point.

All in all, I do think it's easy enough to just bounce back to the previous measurement in REW 4. I think it will lose it after nine measurements, but you can save it and then it's there forever. And actually, there may already be some option to not advance the measurement. I haven't played around with version 4 enough yet. Overall, it's an improvement over the previous releases. And just to be clear to JohnM and everyone else -- I don't think anyone's complaining about the tool. It's tops! I don't know what I'd do without out it. Have shabby bass, I guess. Or shell out $$$ for an SMS-1.


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## brucek (Apr 11, 2006)

> Dent wrote:
> But if you save the filters from the first measurement and then load the filters into the second measurement (or if the first measurement filters were automatically carried forward) then you would be then applying these first set of filters on to the new measurement. Since the new measurement already has the first set of filters applied (because you entered them into the BFD) that would be the same as doubling up all of your filters which would throw everything out of whack.


Yep...... that's correct. 

That's why you don't want the previous measurements filters to automatically move to the next measurement. If you do, simply click Load Filters that you saved. This would be the case where you perhaps disable the BFD filters and take a new raw measurement, but want the filters from the last. Simply Load Filters............

brucek


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## Otto (May 18, 2006)

Not sure. I'm thinking that I just want to be able to repeatedly measure, tweak filter values _manually_, send them to the BFD and remeasure. After the remeasure, I may want to slightly tweak and download filters to the BFD. In that case, there is no doubling.


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## lovingdvd (Jan 23, 2007)

Otto said:


> Not sure. I'm thinking that I just want to be able to repeatedly measure, tweak filter values _manually_, send them to the BFD and remeasure. After the remeasure, I may want to slightly tweak and download filters to the BFD. In that case, there is no doubling.


Yes, exactly. I think that would be much easier.


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## ianfromnotts (Jun 9, 2007)

Otto said:


> Not sure. I'm thinking that I just want to be able to repeatedly measure, tweak filter values _manually_, send them to the BFD and remeasure. After the remeasure, I may want to slightly tweak and download filters to the BFD. In that case, there is no doubling.


Any progress on this suggestion yet? I was looking for the same solution.


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## toecheese (May 3, 2006)

As the others have posted, for my initial setup, this 'measure', save filters, measure again, load filters, chose overlay tab, select the last-two measurements, don't obscure filters, rinse-repeat is not ideal. 

I was hoping I was doing something wrong, but it doesn't appear that way. In the old version I was pretty sure I didn't have to keep loading from disk.

Since that's the way it is, then I'll deal with it, it is certainly more than two clicks though because it wants file names and descriptions each time I save.


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

Yup – REW isn’t real time. That’s what it’d have to be to get the feature you guys are talking about. There are real-time programs out there, like TrueRTA and ETF, but they aren’t free. Any non-real-time program is going to require “trial and error” adjustment.

I don’t see any need to save and re-load, etc. I just re-measure and compare the EQ’d response with the original _predicted_ response, by clicking between them. I tweak the filter(s) in the first window with an eye on making up the difference between predicted and actual response. Typically the amplitude or bandwidth is all that needs to be re-adjusted.

Regards,
Wayne


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## ianfromnotts (Jun 9, 2007)

That was best solution I had come up with too - but was getting quite different graphs after sending filters to the BFD to graphs predicted, I will try sweeping with more passes.


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## toecheese (May 3, 2006)

Wayne A. Pflughaupt said:


> Yup – REW isn’t real time. That’s what it’d have to be to get the feature you guys are talking about.


Hmm, all I want is that when I've set filters and done a new sweep that the filters are automatically reloaded, or the current sweep is overwritten. No RTOS needed for that, just a little HMI study.


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