# First Run with REW... Please be gentle :)



## Digital_Chris (Apr 7, 2011)

Hello users! It's been a while since I've posted anything but I've finally got around to taking some measurements with my new ECM8000 mic and ART dual pre. I started off with the LF measurements first (10-200hz) so I could see how the room acts with and without the superchunk bass traps. I will try to be as thorough as possible. Gear is listed below...

Marantz SR5005 AVR
Behringer DSP1124P
Behringer EP4000
(4) FiCar 128" IB Drivers
LCR Econowave Speakers
Behringer ECM8000 mic with generic cal file from this site
ART Dual Pre sound card

AVR Settings:

Bass Settings: SW Mode - LFE (also have a choice for LFE+Main)
LPF for LFE - 120hz

Speaker Config : All speakers set to small

Crossover Freq : Front/Center - 60hz
Surround/Surround Back - 80hz

Room Dimensions are 18 x 10.5 x 7

Front eyes - roughly 9.5' from screen

Rear eyes - roughly 12.5' from screen

Subs in Line Array on lower portion of front wall

I took a measurement at front center seat and rear center seat to get a baseline of the rooms response. As figured, they both sound different, the LFE at the rear seats is stronger and more tactile while the front seats are not as much. I was hoping the superchunk bass traps would help with this... to a point I guess it did, not NEARLY as much as hoped..

Front Center Seat before Superchunks










Front Center Seat after Superchunks










Overlayed










Rear Center Seat before Superchunks










Rear Center Seat after Superchunks










Overlayed










After all graphs were taken, the db levels seem to be off, I'm guessing that the sound card level or avr was a little off? If you recommend new measurements, I can do that.

The biggest let down is the difference from no bass traps to both superchunks. Unfortunately I don't have the room for superchunks up front but I was hoping the two in the rear would make a noticeable difference, I was let down 

The superchunks are about 5.5' tall, a few inches off the floor (to match my wall panels), to about a foot from the ceiling. I can take pictures if you would like. They are 36" faced and filled with pink fluffy insulation.

The only big difference was in the rear seat at about 66hz, it took about 15db out of the humongous dip, other than that, no big change 

Below is the link to my REW files so you can take a look for yourself. If you want pictures of the room, I can do that as well. Thanks guys  

http://www.sendspace.com/filegroup/gbdlElQ7+qzRUdI5m0b4biRvHXdjkKhF


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

Hey Chris,

It would be much easier for us if you’d just upload your graphs to a post.

Posting A Graph

Getting Graphs Ready to Post


Regards, 
Wayne


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## Digital_Chris (Apr 7, 2011)

Thanks wayne, I have done that in the past but users always mention to upload the actual file, so I started with that. I will go ahead and post the graphs in the first post now


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

I only know of one regular here who asks for the original file; the rest of us prefer graphs. 

I’d agree with your assessment that it appears the traps didn’t make much difference – at least in frequency response. However, traps can make a difference in low frequency decay times (aka “ringing”). For that, it’s best to compare “before and after” waterfall graphs. REW can generate those from the measurements you’ve already taken. I’d suggest extending the upper frequency limit of the graph to 300 Hz or so, if your measurements went up that high, and graph floor down to 30 Hz.

Regards, 
Wayne


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## SAC (Dec 3, 2009)

The fact is that most here start and end with a smoothed frequency response with a world view that ends at ~200 Hz and EQ. And as such they have no use for the file which allows one to delve into the specular realm above ~250 Hz that determines imaging, localization, intelligibility, coloration, timber spatial and temporal characteristics of the soundfield and all that other 'inconsequential stuff' at a much deeper level.

A shame.


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## Digital_Chris (Apr 7, 2011)

Here are a few waterfall graphs for before and after the superchunks. I couldn't figure out how to overlay the waterfalls so I'm not sure how easy these will be to read, but worth posting anyway...

Before Superchunks front center seat...










After Superchunks front center seat...










Before Superchunks rear center seat...










After Superchunks rear center seat...










Any thoughts?


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

Assuming all “before” and “after” readings were taken at the same SPL level, it looks like the traps reduced ringing above 50 Hz. :T

Regards, 
Wayne


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## Digital_Chris (Apr 7, 2011)

That's the thing, I'm not sure the SPL is correct by looking at my rear seat graphs, I might have to re-measure :-/

Here are a couple of ETC plots from tonight though. They are 10-20k sweeps from the left and then the right main speaker at front center LP. I'm not sure how to run tones through my center channel, any tricks I'm missing?

Here are the graphs...

Right channel...










Left channel...










I'm still not too sure how to read these though, maybe I'll have some time tonight at work to read up on this.

Let me know what you think


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## Digital_Chris (Apr 7, 2011)

Looks like I may have generated the wrong graphs, these don't look like other users ETC graphs. To generate these, I went to "overlays" and then "ETC", I didn't see an "ETC" tab in the main graph window.

EDIT: Sorry sorry sorry sorry, I think my problem is the time range I used. I have it set all the way from 0-2.00 seconds while other users have it set from about 0-40ms, is that the usual range? I'll reset those in the morning and repost


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## Digital_Chris (Apr 7, 2011)

There, those look better, now you may let me know what you think


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## Digital_Chris (Apr 7, 2011)

So, I was getting sick of how slow my mini laptop was for running programs including REW so I decided to setup my macbook pro. All went well after a bit of fooling around 

My graphs are a bit different now, all are posted below...

Left Channel: (FULL - SMOOTH - ETC - WATERFALL 10-300hz - WATERFALL 10-20khz)














































Center Channel: (FULL - SMOOTH - ETC - WATERFALL 10-300hz - WATERFALL 10-20khz)














































Right Channel: (FULL - SMOOTH - ETC - WATERFALL 10-300hz - WATERFALL 10-20khz)














































I hope you like graphs! 

I'm not completely sure how to read the waterfalls or the ETC's yet, any help or guidance would be great


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## localhost127 (Jan 2, 2011)

Wayne A. Pflughaupt said:


> I only know of one regular here who asks for the original file; the rest of us prefer graphs.


no, the "rest of us" prefer the file itself as we become tired of waiting for the user to learn how to scale the graphs correctly. it's much easier if they post the file then those that wish to assist have ALL of the information regarding the measurement and don't have to wait for the user to waste time uploading screen shots which may or may not (usually NOT) have the correct scale/window settings/etc.


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## Digital_Chris (Apr 7, 2011)

localhost127 said:


> no, the "rest of us" prefer the file itself as we become tired of waiting for the user to learn how to scale the graphs correctly. it's much easier if they post the file then those that wish to assist have ALL of the information regarding the measurement and don't have to wait for the user to waste time uploading screen shots which may or may not (usually NOT) have the correct scale/window settings/etc.


Are my graphs scaled correctly Local? I can post my files, that's no problem, would you like to see them? I'll post them anyway, if you care to look at them, I appreciate it. If you recommend more sweeps before I post the files, let me know.

Right now I'm working on a jig to hold my mic and after that's finished, I will take measurements at the rest of the seats.

If someone could help me understand how to read the ETC and waterfall graps, that would be great! I have an idea of how to read the ETC's, but the waterfalls, I'm still a bit in the dark :dontknow:

Just at a glance though, I think my ETC's look pretty good as is, I don't see any huge spikes


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

Hey Chris,

The waterfall shows the rate of the signal decay. This post and this post offer a perhaps simplistic but hopefully effective explanation about signal decay.

Translating that to the graphs you showed us in Post #6...



Digital_Chris said:


> Before Superchunks rear center seat...
> 
> 
> 
> ...


... notice that the decay slope above 50 Hz is steeper in the “after” graph. This denotes a faster rate of decay compared to the “before” graph. The same thing is evident in your other pair of graphs, too. So you are getting reduced ringing above 50 Hz with the traps. Whether or not it’s enough to be audible, you have to determine for yourself.

Re ETC graphs, see  this post.

Regards, 
Wayne


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## Sonnie (Apr 11, 2006)

SAC said:


> The fact is that most here start and end with a smoothed frequency response with a world view that ends at ~200 Hz and EQ. And as such they have no use for the file which allows one to delve into the specular realm above ~250 Hz that determines imaging, localization, intelligibility, coloration, timber spatial and temporal characteristics of the soundfield and all that other 'inconsequential stuff' at a much deeper level.
> 
> A shame.


What is a shame is that you had to be banned because of your snide and condescending attitude (that you have been warned about numerous times) and ignorance to what our purpose here is. It is absolutely amazing that you learned so much about audio acoustics/equalization, yet never learned the first iota about public communications. Indeed it is truly a shame.

This is a perfect example of your ignorance to what the OP requested help with. At this point he is not looking for help with frequencies above 200Hz. READ his post: _I started off with the LF measurements first (10-200hz) so I could see how the room acts with and without the superchunk bass traps._ 

If after he receives help with his initial request and later decides he wants help with _the specular realm above ~250 Hz that determines imaging, localization, intelligibility, coloration, timber spatial and temporal characteristics of the soundfield and all that other 'inconsequential stuff' at a much deeper level_... he may very well requests such help.



localhost127 said:


> no, the "rest of us" prefer the file itself as we become tired of waiting for the user to learn how to scale the graphs correctly. it's much easier if they post the file then those that wish to assist have ALL of the information regarding the measurement and don't have to wait for the user to waste time uploading screen shots which may or may not (usually NOT) have the correct scale/window settings/etc.


Wayne has been around here since we started this place and is well aware of our purpose here and what is generally the norm. You should learn a bit of respect... and if you insist on continuing this condescending attitude you will join the ranks of SAC. If you want to help, read our Zero Tolerance Forum Rules and kindly abide in them... otherwise hit the road jack, as we have no use for it here.

Sorry for the interruption... you all (with one obvious exception) may continue on topic... as no response to this post is needed or expected... actually best left with no response.


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## localhost127 (Jan 2, 2011)

Sonnie said:


> This is a perfect example of your ignorance to what the OP requested help with. At this point he is not looking for help with frequencies above 200Hz. READ his post: _I started off with the LF measurements first (10-200hz) so I could see how the room acts with and without the superchunk bass traps._


you realize the OP posted the ETC's, right? the ETC's are not relevant to the modal region, so help above 200hz is relevant to the discussion.



Sonnie said:


> Wayne has been around here since we started this place and is well aware of our purpose here and what is generally the norm. You should learn a bit of respect... and if you insist on continuing this condescending attitude you will join the ranks of SAC. If you want to help, read our Zero Tolerance Forum Rules and kindly abide in them... otherwise hit the road jack, as we have no use for it here.


i did not see any reference to Wayne within the rules when i signed this board, so pardon the ignorance with respect to whomever that is.

i really don't see why there should be ANY objection to a request that the OP (who is here looking for help) - post the .mdat files vs merely posting screenshots that DO NOT provide data for me to help him assist.

posting the file should be the default behavior. it's obvious.


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## Digital_Chris (Apr 7, 2011)

Wayne A. Pflughaupt said:


> Hey Chris,
> 
> The waterfall shows the rate of the signal decay. This post and this post offer a perhaps simplistic but hopefully effective explanation about signal decay.
> 
> ...


Perfect, thanks for that, appreciate it


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## Digital_Chris (Apr 7, 2011)

Also, here is a link to the actual files.


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## localhost127 (Jan 2, 2011)

Wayne A. Pflughaupt said:


> Re ETC graphs, see  this post.
> 
> Regards,
> Wayne


FYI that is not the correct way to measure with ETC -


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## Sonnie (Apr 11, 2006)

localhost127 said:


> you realize the OP posted the ETC's, right? the ETC's are not relevant to the modal region, so help above 200hz is relevant to the discussion.
> 
> 
> 
> ...


You just couldn't resist could you... :rolleyesno:

I am fully aware of what he posted... as well as what he requested specific help with, but obviously you are not comprehending it too well.

There does not have to be a reference to someone in the rules for you to have respect for them. You can look at his join date of April 2006 and his post count and realize he has been around long enough to understand what the norm is here at HTS better than someone who can't even comprehend a post very well.

There is no issue with anyone requesting a file, if it is done in a polite manner and without a snide and condescending tone. Wayne was simply stating the preference of most of those that provide help... and you spouted off disrespectfully... but you solved our issue with that happening again by being disrespectful yet again.


I apologize to the OP for the particular dipwits who cannot resist derailing a thread with their nonsense. They get away with it at other forums and think they can cause the same riot here. Hopefully it is now resolved and will no longer be a problem.


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## Digital_Chris (Apr 7, 2011)

Wayne A. Pflughaupt said:


> Re ETC graphs, see  this post.
> 
> Regards,
> Wayne


That isn't how my graphs look and I'm not sure how to use that measurement tool it shows. I understand that I need to look at the "peaks" and note their millisecond times and then I can find out where in the room they are after converting time to distance but I'm not sure what "peaks" are bad in my graphs, even after I zoom in. Any more insight?


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## Digital_Chris (Apr 7, 2011)

Also, thank you Sonnie for your replies


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## fotto (Jan 17, 2010)

Chris, you may want to review my thread on ETC as it should help you out:
http://www.hometheatershack.com/forums/rew-forum/52211-help-etc-interpretion.html

What I believe Local was referring to on proper way to measure was using loopback as timing reference. This takes out system delay and give you the actual time of flight of your reflections.

Once you do that, you should scale your graph to get a bigger picture of the response (say out to about 40ms) similar to following:


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## Digital_Chris (Apr 7, 2011)

After your link I still don't completely understand but let me set the loopback and re-run a few sweeps, hopefully I will see these peaks. Is there a way to smooth out the graphs for ETC? I have seen some graphs that seem much smoother than mine, and how do I measure the length? I can't find the measuring tool.


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## fotto (Jan 17, 2010)

I'm not sure what you're asking about "smoothing out the ETC graph". If you meant to scale it to size properly, you can do that with the "Limits" button in upper right side of REW.

To measure distance, place cursor at 0 on the graph, then press Ctrl key and R mouse button simultaneously and drag to the ETC peak you want to measure. Distance will be displayed.


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## JohnM (Apr 11, 2006)

Digital_Chris said:


> Is there a way to smooth out the graphs for ETC? I have seen some graphs that seem much smoother than mine


If you click the gear icon at the top right of the graph the controls will be displayed, ETC smoothing is one of the controls. Make sure you are comparing the same timescales when looking at other graphs though.


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## Digital_Chris (Apr 7, 2011)

Ok great, thanks John


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## Digital_Chris (Apr 7, 2011)

Here are a couple graphs I took tonight, the only change was the mic position from front center seat to rear center seat, what a difference!! What do you guys do when you are trying to EQ for multiple rows? Since I'm sure that EQ can't make my response flatter for both rows, what are my next options, some other form of bass trapping?

*Front Center Seat*










*Rear Center Seat*










*Overlayed*


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## ALMFamily (Oct 19, 2011)

Chris,

I could be wrong (and I am sure someone will correct me if I am), but you will more than likely only be able to dial in a "primary seating" location. As I understand it, as you move around the room, you deal with varying sound fields by which I mean peaks and nulls.


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## Digital_Chris (Apr 7, 2011)

Yeah, I figured as much... Just need to figure out how to tame the bass overall :/

Suggestions are welcome!!

If you need more info of my room and gear, let me know


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

Digital_Chris said:


> Yeah, I figured as much... Just need to figure out how to tame the bass overall :/


That’s going to be pretty tough as you appear to have peaks and depressions in the same area. I’ve heard that multiple subs is a good way to get more consistent bass response in multiple locations – might look into that.

Regards, 
Wayne


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## Digital_Chris (Apr 7, 2011)

I haven't dived into that too much yet because I'm running an IB setup and heard box subs don't work well with IB. I wouldn't even know where to start with that thought anyway, do I only need filler subs for the rear? I "could" run more speaker wire back there for more subs but again, not sure where to start playing with that idea..


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## DeuceTrinal (May 7, 2012)

This white paper by Dr. Toole (acoustical genius) might provide some insight: google "Loudspeakers and Rooms for Multichannel Audio Reproduction" (I can't post links yet, too new).

I think you could probably fix some of the worst modes with a second sub, especially big nulls. Then you could EQ out the worst peaks at the primary position.


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## Digital_Chris (Apr 7, 2011)

Thanks Deuce, I'm waiting for a buddy to arrive so he can help me bring my living room sub downstairs to add that to the mix. I will post later on how that affect the room response, wish me luck!


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## Digital_Chris (Apr 7, 2011)

Well, as many of you could have predicted, it worked!!! :clap:

I disconnected two of my 18's, wired the outer two to one channel on my amp and hooked up my table tuba from upstairs to the other channel on the amp, set my gains so that both "subs" separately put out the same spl and voila! Out came more even response across both rows!!

Again, most of you are like, yeah, uhh, Duhh! 

But, I had to see for myself and see what it could actually do. So, what does this mean? It means that I'm wiring in one or two subs in the back of the room!!! Haha, some light finally peeped it's way through the crack 

Here are few graphs to show what happened...

*Front Center no TT...*










*Front Center w/TT...*










*Overlayed...*










*Rear Center no TT...*










*Rear Center w/TT...*










*Overlayed...*










:woohoo:

Now, I still have some funkiness going on above 80hz, any ideas?

I did try a few different crossovers, 60hz/80hz, 80hz80hz, 100hz/100hz, 120hz/120hz. Out of all the above, 120hz/120hz worked best, is this odd?


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## Digital_Chris (Apr 7, 2011)

Ok, so I just learned something new. A null isn't what I thought it was, I was thinking any semi large/broad "dip" was a null. I now learned that would be more of a trough than a null. A null is sharp and very deep, I now see how EQ cannot fix these.

Wayne, you posted in another thread, a graph of yours that was smoothed out quite well via EQ, can you repost that and explain what it took to achieve those results?

I was under the impression that no boosting was allowed via EQ, was I just misled?

EDIT: Just for terminology sake, is a peak then the same as a null, just the opposite, sharp and tall?


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## JohnM (Apr 11, 2006)

Digital_Chris said:


> EDIT: Just for terminology sake, is a peak then the same as a null, just the opposite, sharp and tall?


Not really. Signals that are at the same level but 180 degrees out of phase at some frequency can combine to produce an infinitely deep null (zero level, which when converted to dB is minus infinity). The same signals added at a frequency where they have the same phase only increase the level by 6dB. Peaks and troughs are more akin to what you can produce using parametric EQ, nulls are more like notch filters and don't really have a boost equivalent.


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

Hey Chris,

Sorry, not sure which thread you’re talking about. 

I’ve been explaining to folks for quite a while now – years in fact - that not every depression in response is a null, and those that aren’t nulls (which are characteristically sharp and deep, as you noted) can usually be equalized with a boosted filter.




Digital_Chris said:


> I was under the impression that no boosting was allowed via EQ, was I just misled?


Yup. That’s another myth I’ve been trying to dispute for years – it’s an uphill battle.

Here are a few relevant posts you can peruse.

EQ boosting vs.cutting A 
EQ boosting vs.cutting B
Equalizing Nulls

Regards, 
Wayne


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## fitzwaddle (Aug 25, 2010)

Digital_Chris said:


> I was under the impression that no boosting was allowed via EQ, was I just misled?


I threw some pretty heavy boost on dips on my THTs, so far so good (has been many months that way) - caveat, I don't listen at reference, I do -12 most of the time, maybe -10 to show off - so I figured I have that headroom to put to use:










If you do boost, watch peak voltage (voltmeter) being sent to the sub during a sweep to make sure you don't toast the driver.


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## Digital_Chris (Apr 7, 2011)

Wayne A. Pflughaupt said:


> Hey Chris,
> 
> Sorry, not sure which thread you&#146;re talking about.
> 
> ...


Thanks for the links Wayne, the one titled "Equalizing Nulls" is the one I was referring to. Now, what about the whole, double the power for every 3db boost, this is where I have to be careful?


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## Digital_Chris (Apr 7, 2011)

fitzwaddle said:


> I threw some pretty heavy boost on dips on my THTs, so far so good (has been many months that way) - caveat, I don't listen at reference, I do -12 most of the time, maybe -10 to show off - so I figured I have that headroom to put to use:
> 
> If you do boost, watch peak voltage (voltmeter) being sent to the sub during a sweep to make sure you don't toast the driver.


Thanks for sharing your graph 

That new response looks great! I need to rescale my graph apparently so others can get a better vision 

How many filters were applied to get that final graph very flat? Also, when you say EQ, is that just with a BFD or Audyssey as well?


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## fitzwaddle (Aug 25, 2010)

8 filters - went a little crazy :heehee: - just BFD (FBQ2496)


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## Digital_Chris (Apr 7, 2011)

I thought it would take many more than that! Good job :T

Any advice for setting filters with a BFD?


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

Digital_Chris said:


> Now, what about the whole, double the power for every 3db boost, this is where I have to be careful?


As noted in the linked posts, it’s all about headroom. Any equalization taxes headroom, so you have to have plenty to spare going in. After equalization, as long as your driver’s not bottoming out, and your amp’s not clipping, you’re fine. If one or the other is happening, obviously you’ll then have to make some adjustments, either with less equalization or upgraded equipment.

Regards, 
Wayne


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## JohnM (Apr 11, 2006)

I would be very cautious of heavy boosting due to the variation of response with position, a hefty dip at one spot may disappear a short distance away, so the boost that makes the response flat at the original measuring position creates a big peak somewhere else - that tends to sound worse than cuts creating dips in locations where the peaks they were aimed at don't exist. Best to make a few measurements within the listening area(s) to check that the corrections applied give the best overall result.


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## Digital_Chris (Apr 7, 2011)

Very true, thanks for adding that in John. I will measure all seats before making final decisions


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