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Ken Pachkowsky
08-11-2006, 11:12 PM
I have been lucky enough to pick up a second Deqx 2.6P. This one is the dual chassis version with a full compliment of digital in's and out's as well as the balanced outputs.

Now I can daisy chain the 2 units together and use it as a full stereo 5 way utilizing the Deqx crossover system. Should be a very interesting journey. Of course I will only use 8 of the 12 available channels for driving the stereo 4 way system while 2 of the channels will be used to sync or daisy chain the Deqx's. That leaves an extra pair of outputs for future use. This should be one powerfull processing system with incredible control over the crossover points and slopes. So far I have been quite impressed with the overall performance of the system but have only used the preamp section and parametric eq functions.

Widget.........I will probably be calling on you for some assistance.:D

Ken

Mr. Widget
08-11-2006, 11:16 PM
Widget.........I will probably be calling on you for some assistance.:D


I'll be contacting AT&T in the morning to change my number. :banghead:


...er, um, I mean congratulations!


Widget

Titanium Dome
08-12-2006, 09:15 AM
widget, you can be such a bad bay! :rotfl:

Congratulations, Ken. :thmbsup:

scott fitlin
08-12-2006, 02:36 PM
Call me as soon as you can Ken, I`d love to help, my new number is 1-800 Got-Bose. :thmbsup:


WidgetWay to go Widget, your such a sport, and all around good guy!

Way cool, Ken, congrats.

:D

Ken Pachkowsky
08-12-2006, 03:07 PM
Way to go Widget, your such a sport, and all around good guy!

Way cool, Ken, congrats.

:D

Thanks Scott. We shall see if I have the smarts to set it up properly. The instructions are somewhat straight forward but the software is not the most intuative. I have never really learned how to "properly" interpret graphs and will definately have to get a better handle on that to use it properly.

If I like the results I will part with my Westlake HRX although I am not sure if anyone other than an HR1 owner would be interested.

Ken

scott fitlin
08-12-2006, 03:19 PM
Its exactly this that made my go with the BSS over the Lake Contour, I just didnt want to have to use laptop to set it up, or make minor adjustments, couldnt give up my front panel controls.

Of course, if you take the time to get the best the DEQX can provide, you should get really excellent results.

:)

Ken Pachkowsky
08-12-2006, 03:27 PM
Its exactly this that made my go with the BSS

:)

Do you have the BSS 960 or 966?

Ken

scott fitlin
08-12-2006, 03:31 PM
Im talking about xover, the 366T, and your DEQX also is a comprehensive loudspeaker crossover, that also has EQ, and time alignment, etc.

With DEQX, and Lake Contour, in order to make adjustments, and set up, you need to connect a lap top to the unit. Unlike the traditional way of front panel knobs, or menu screen.

Of course, its pretty well known that the Lake and DEQX have the best sounding DSP available presently, just a bit more work to set up.

Ken Pachkowsky
08-12-2006, 03:37 PM
Im talking about xover, the 366T the best sounding DSP available presently, just a bit more work to set up.

Oh sorry, yes I did some reading on the BSS system several months ago and it sounded very interesting as well. How do you like it?

Ken

scott fitlin
08-12-2006, 05:07 PM
Its good, its easy to set up and use. It allows me to do whatever I want, gain, slopes, filter types, time align, EQ, limiting, etc. Once I got it going to full potential it sounds quite good.

Ken Pachkowsky
08-13-2006, 12:21 PM
Here is a plot after running speaker analysis and creating correction filters with the Deqx. My initial curves were bogus as I did not follow the instructions properly by dragging the stop line to the first reflection point on the curve (before creating the filters).

Widget, that's why the initial plots looked so bad.

I shot this this morning after reading the manual thoroughly and re-shooting. I took your advice and placed puffy pillows on the floor from the base of the speakers to below the mic. These were shot at 5 feet 2 inches pointed directly between the 2 horns.

This plot shows the system after the newly created correction filters were applied. Not to bad considering this room is far from ideal.

Ken

Ken Pachkowsky
08-13-2006, 12:28 PM
I Hope

boputnam
08-13-2006, 01:35 PM
Curves...

So, what's the red and what's the green curve...?
What is that sharp notch at ~160 Hz (a crossover point?)?

And, ferchrissake - tell us how it sounds!!

Ken Pachkowsky
08-13-2006, 01:56 PM
Curves...

So, what's the red and what's the green curve...?
What is that sharp notch at ~160 Hz (a crossover point?)?

And, ferchrissake - tell us how it sounds!!

The red is the right channel and green is dah left.

The notch is a crossover, room , driver anomaly or? Seriously I have no idea whats causing it but the nearest crossover point is 250hz

How does it sound? Well, it sounds damned good but a bit hollow IMHO. The sound stage is wider, less defined and slightly muddy. I think tweaking this and more importantly "learning how to use it" will take some time. Having never used Parametric Eq's they are definitely interesting in terms of flexibility.

Ken

johnaec
08-13-2006, 02:31 PM
I'm sure you've probably seen this review - it really illuminated a bunch of stuff for me: http://www.6moons.com/audioreviews/deqx/deqx.html

I do have a question, though. The Deqx site mentions speaker correction, room correction, and media correction. For room correction, it mentions up to 10 bands of graphic or parametric EQ, and apparently less for media correction, but I couldn't see where speaker correction might also have a specific filter selection. Do you know how many bands of graphic/parametric selection that speaker correction has, or is it lumped in with the 10 band room correction?

John

Mr. Widget
08-13-2006, 03:05 PM
I do have a question, though. The Deqx site mentions speaker correction, room correction, and media correction. For room correction, it mentions up to 10 bands of graphic or parametric EQ, and apparently less for media correction, but I couldn't see where speaker correction might also have a specific filter selection. There are only ten bands available for room and CD/media "correction". These ten bands can be used as a simple graphic equalizer (I can't imagine why anyone would ever do that... unless they simply can't get their head around the use of a parametric.) As an example of how powerful the DEQX parametric filters are, only two of the parametric bands are all that are required to duplicate the RIAA phono curve with an accuracy that is higher than most phono stages.

Anyway, you can access three of these bands and modify and store them for tweaking the sound of up to 99 different "room curves" or "CD curves"... these are all accessible via the remote control... or you can access all ten bands and use them to "correct" your room.

In addition to these parametric filters there are additional FIR filters that are used to "correct" your speakers. These filters are separate and are automatically generated based on your speaker measurements. Here are the correction filters that DEQX created for Project May. It is easy to see the mid band correction is roughly the mirror image of the curve supplied us from JBL (the band between the 800Hz and 10KHz crossover points). You can also see the DEQX "correction" filtering balancing out the naturally rising curve of the 1500ALs. (Below 800Hz)

For those who don't understand what this graph shows... it is not the response of the speakers, it is the electrical boost and cut created by the DEQX unit to balance the response of the speakers. Therefore when this curve goes up, that is where the speakers originally had too little output and where the curve goes down, the speakers originally had too much output.


Widget

johnaec
08-13-2006, 04:06 PM
In addition to these parametric filters there are additional FIR filters that are used to "correct" your speakers. These filters are separate and are automatically generated based on your speaker measurements.That was kinda' what my question was about; you've clarified that the speaker correction filters are a different set. I assume they're parametric, (as opposed to numerous fixed "graphic" filters that interact), but do you know how many bands of "automatic" parametric are available for this mode? I assume there must be a maximum number, (which is undoubtedly more than would likely ever be needed). Not that it would make any kind of difference in the real world - I'm just curious...

Or are these FIR, (??), filters a completely different animal altogether, (not band or frequency based, but rather curves somehow extracted mathematically from the speaker response)? I'll also try reading up some more...

John

Mr. Widget
08-13-2006, 04:11 PM
I have no idea how the filters work. As you can see from those curves, you can not create such specific "corrections" with a handful or parametric or even dozens of graphic filters.


Widget

johnaec
08-13-2006, 04:13 PM
I mqay have missed them, but have you posted CLIO curves of your system with the Deqx inline? (I'll try a search later.)

John

Ken Pachkowsky
08-13-2006, 04:17 PM
If I am reading your question correctly it would be a maximum of 10 both graphic and parametric.

This is the first day I have been able to spend really using this and it is truly amazing. The fine tuning flexibility is incredible. That hollow sound I spoke of earlier is history. It just required a fine tuning of the filters.

Widget could be right. He told me if I were patient I would probably really like this unit.....:) .

Ken

Ken Pachkowsky
08-13-2006, 04:25 PM
These are the current filters.

Mr. Widget
08-13-2006, 04:47 PM
If I am reading your question correctly it would be a maximum of 10 both graphic and parametric.Nope. There are ten filters, period. You essentially get to choose how you use them... if you choose graphic, the Qs are set to a fixed value with an even distribution of frequency centers... and then you have a graphic.


Widget could be right. He told me if I were patient I would probably really like this unit.....:) .I think I said that if you could get it set up properly, you'd probably like it. Patience is certainly required, but so is a careful methodological implementation. Good to hear you are starting to get it to work for you.


Widget

Ken Pachkowsky
08-13-2006, 04:51 PM
Nope. There are ten filters, period.

Widget

Got to be carefull how you word things.....yes 10 only, graphic or parametric is what I was saying.

Ken

johnaec
08-13-2006, 10:51 PM
Got to be carefull how you word things.....yes 10 only, graphic or parametric is what I was saying.I take it that's in addition to whatever the Deqx uses for its custom speaker correction filters?

John

Ken Pachkowsky
08-13-2006, 11:02 PM
Yes, that is correct.

Ken

Steve Schell
08-14-2006, 01:15 PM
Hi guys,

Mr. Widget, I sure wish I could bring you to my place for a day to show me the fine points of DEQX setup. My partner and I have been able to grunt through the filter correction process, but it has been like pulling teeth for us.

Our general approach has been to make and apply the correction filters for mono sub and left and right bass and midrange/high frequency horns and also add delay to the mains to let the long path sub catch up. Then we feed pink noise to the system and juggle individual driver levels and perhaps a bit of correction with the parametric to get the most even and pleasing response in the room, monitoring with the Phonic RTA.

I think we are getting close with it. I have recently made some recordings with a coincident pair of ribbon mics and an Alesis Masterlink running 24 bit/96kHz. A recording made at the Fullerton train station worked out well, and the freight trains are now rolling through the living room in a believable fashion.

boputnam
08-14-2006, 05:39 PM
...and also add delay to the mains to let the long path sub catch up. It'd be interesting to see the impulse measurement of each the mains and the subs, if you get them...

boputnam
08-14-2006, 05:41 PM
For those who don't understand what this graph shows... it is not the response of the speakers, it is the electrical boost and cut created by the DEQX unit to balance the response of the speakers. How is this measured, Widget? How do DEQX know?

Is there a mic used to "feedback" into the DEQX the speaker output, so that "it" knows what to do?

Steve Schell
08-14-2006, 06:05 PM
Hi Bo,

I suppose that the impulse plots are in there, but I am not sure how to access them. I am still quite a novice with this thing, even after devoting considerable time to learning it. It's a beast, but then I have never been very good with computers.

I can take a stab at your question about the DEQX measurement process. When you make a measurement, the program feeds several bursts of signal, pink noise I think, to the particular driver being measured. The microphone supplied with the unit is placed in front and its signal is fed back into the DEQX. Once all the measurement data is recorded the attached computer running the program does some serious number crunching and after a couple of minutes produces the impulse response plots for each channel, with the individual drivers overlayed. It asks you to window the graph, then after more crunching produces the "correction filters" or inverse of the speakers' amplitude and phase errors, plus correction for their errors in arrival time. Once these correction filters are applied the speaker produces a virtually perfect amplitude and phase response, at least at the mic position. I have heard the unit work miracles, even with my rudimentary use of it.

Mr. Widget
08-14-2006, 06:07 PM
How is this measured, Widget? How do DEQX know?

Is there a mic used to "feedback" into the DEQX the speaker output, so that "it" knows what to do?Yes, when you buy the DEQX with the calibration software (an option) you get a calibrated mic. The curve is essentially the inverse of what was measured from the speaker. In this case it was two measurements, one for the left and one for the right speaker. In both cases I had the mic on a stand at mid horn height on axis and 1m away from the speaker.


Widget

Mr. Widget
08-14-2006, 06:12 PM
Once these correction filters are applied the speaker produces a virtually amplitude and phase perfect response, at least at the mic position.Yes, and therein lies the rub.

I and other friends have found that with large horn systems it hasn't been possible to get a really good set of correction filters due to room interaction. I have chosen not to use any correction filters and I do all of my corrections manually... with a little help from my pal CLIO. The results are quite impressive. When used properly the DEQX PDC2.6 is a great tool... but as Steve said it is a bear... especially at first.


Widget

boputnam
08-14-2006, 06:23 PM
Hi, Steve...

Thanks - that's what I thought, and figured it must be so.

But then, those response/correction curves of Ken's have some extremely hi Q anomalies. I wonder what was going on - never seen that sort of response...

Ken Pachkowsky
08-14-2006, 08:29 PM
But then, those response/correction curves of Ken's have some extremely hi Q anomalies. I wonder what was going on - never seen that sort of response...

Bo

The curves I posted are from the EQ window not the Filter window. There is a huge difference. The correction filter curves are pretty flat and smoothed out. I will post an example later on.

Ken

Ken Pachkowsky
08-14-2006, 08:52 PM
In your opinion, have I moved the boundry line on this reading to the proper spot to get the best analysis?

Ken

boputnam
08-14-2006, 09:00 PM
The curves I posted are from the EQ window not the Filter window. There is a huge difference. The correction filter curves are pretty flat and smoothed out. I will post an example later on.Yea, I would expect that - that is what DEQX is 'sposed to do. But I remain transfixed on the response curve - I've never seen something like that. Curious...

Ken Pachkowsky
08-14-2006, 09:03 PM
Bo

After applying correction filters this is the frequency response.

Ken Pachkowsky
08-14-2006, 11:04 PM
What, your not going to call me on that;)

Ken

Mr. Widget
08-15-2006, 12:34 AM
Yea, I would expect that - that is what DEQX is 'sposed to do. But I remain transfixed on the response curve - I've never seen something like that. Curious...What's bugging you Bo? Is it the dip I circled? That is likely a cancellation due to the distance of the mic to speaker to floor ratio... it is not all that uncommon to see something like that. I would guess that moving the mic up and down or back and forth will move it/remove it...


Widget

Mr. Widget
08-15-2006, 12:59 AM
In your opinion, have I moved the boundry line on this reading to the proper spot to get the best analysis?Yes, but it is unfortunate that your first reflection is so soon... you really won't be getting much useful data below the midrange.

This is a graphical example of what I was talking about when I said that you won't be able to create a good correction filter. If you took the speaker outside and pointed it up in the air with the mic suspended over it, you would get a much better correction filter.

I realize that DEQX is giving you a ruler flat curve, but that is BS... it is simply subtracting the correction from the source... of course it will be flat... since the real curve isn't what you are measuring, the results are??? If you did this procedure with a small speaker elevated off the floor and a good distance from any objects you would be able to really get it to work... I don't think I am making this any clearer am I... if you read, Joe D'Appolito's book on measurement techniques it will make sense... he is way better at describing what is going on.


Widget

Steve Schell
08-15-2006, 01:34 AM
Widget, I agree that your dip around 160Hz. is probably a cancellation from the floor bounce. If the additional distance to the floor and back to the mic is about 3.5 feet it would be 180 degrees out of phase at 160Hz. I have seen this many times when making LMS measurements.

I also agree that making in room ungated measurements below 300Hz. or so is pretty much useless, as the room modes take over. I spoke with DEQX founder Kim Ryrie and one of his engineers about this, and they agreed with your suggestion of the outdoor measurement. They recommended placing our horns pointing up at 45 degrees and the mic 18" out from each horn on axis to make the measurements.

One problem that we've had is in setting the window on the impulse measurement. It overlays the plots of the midrange/high frequency horn and midbass horn, the latter having a 6 1/2' longer path length. There are so many closely timed reflections in the bass plot that it is difficult to know where to set the right border. I suppose if I hauled the horns outside then this might not be so much of a problem.

Shane Shuster
08-15-2006, 01:55 AM
This is a graphical example of what I was talking about when I said that you won't be able to create a good correction filter. If you took the speaker outside and pointed it up in the air with the mic suspended over it, you would get a much better correction filter.
Widget
But then it wouldn't be good when you placed the speaker back in the room? Or does a DEQX not work like a TACT?

Steve Schell
08-15-2006, 02:18 AM
Shane, I am not familiar with the TACT, but the room is going to screw with the speaker's response no matter what you do. Mostly large peaks and valleys in the bass are created by the room modes, and vary by location in the room. The best that can be done is to have the DEQX (or whatever unit) measure the speaker in an environment that is free of the room problems. The room will still introduce problems when the speakers are brought back in, but at least the room will not influence the measurements.

Having said all that, I've wondered what the results would be if all DEQX measurements were taken with the mic in the listening chair. Perfect amplitude, phase and arrival time in that spot might be great, although the next seat over could be awful.

boputnam
08-15-2006, 07:29 AM
I also agree that making in room ungated measurements below 300Hz. or so is pretty much useless, as the room modes take over. :yes: Bingo.

johnaec
08-15-2006, 07:51 AM
After applying correction filters this is the frequency response.Are you saying that after correction the frequency response of the speaker via calibrated mic is actually that flat?? :blink: I truly can't believe that.


What, your not going to call me on that;)Or are you pulling our leg?

Edit:
I realize that DEQX is giving you a ruler flat curve, but that is BS... it is simply subtracting the correction from the source... of course it will be flat... since the real curve isn't what you are measuring, the results are???Oh - I see...now I understand - that's the theoretical response.

John

Ian Mackenzie
08-15-2006, 07:56 AM
Ken,

Have you been able focus on getting DEQX to emulate exactly what the Westlake active crossover does as far as real voltage drives are concerned?

There appears to be a notch at 4.5Khertz and at 6.5khertz? They maybe crossover point related.

Ken Pachkowsky
08-15-2006, 09:21 AM
Ken,

Have you been able focus on getting DEQX to emulate exactly what the Westlake active crossover does as far as real voltage drives are concerned? I will have my second unit within the next week and have the ability to go 4-way.

There appears to be a notch at 4.5Khertz and at 6.5khertz? They maybe crossover point related.

Ian

As I have not used the crossover abilities of the Deqx I have no idea how it will compare although from what I have read and heard it should do very well.

As far as the 4.5k and 6.5k notches I agree as the crossover point is 4.5k.

I wish I had a way of measuring the voltage drives of each channel on the hrx. I simply don't have the equipment or the know-how.

Ken

Mr. Widget
08-15-2006, 11:00 AM
:yes: Bingo.So I guess I am surprised that you haven't seen these suck outs before... maybe it is because you use Smaart to capture more room and less speaker?



Edit: Oh - I see...now I understand - that's the theoretical response.
No, it isn't theoretical... it is real, but it is only flat at the mic capsule. Since DEQX "heard" all of the bounced information along with the direct information it corrected the speaker based on faulty (not particularly useful) data.

That is why for it to really work, it is necessary to use the DEQX correction technology in an anechoic chamber... NHT does this with their system that they sell with built in DEQX. Basically if you can get a true anechoic measurement of your speaker, the DEQX technology can make it flat to within a fraction of a dB... the next best thing and only practical solution would be to go outdoors...


But then it wouldn't be good when you placed the speaker back in the room? The point is that no speaker is even remotely flat... here is a real anechoic measurement by JBL of the 4345... if they had used a DEQX in there the result would be that this specific 4345 that was measured would come out dead flat. Even the comb filter ringing that occurs around the 10KHz crossover point can be eliminated by using a super steep crossover slope. The room will then mess that flat response up, but that will always be the case as Steve said... DEQX has a room correction feature too... for room correction you take your "flat" responding speaker and take a series of in room measurements... DEQX will then use it's 10 band parametric EQ to reduce the effects of the room.


The bottom line is that it really does what is advertised... unfortunately with most speakers that we like it doesn't work out too well... it seems to me that Kim Ryrie and the gang designed the system for a two-way mini monitor and subwoofer... for this type of system, in room measurements can be quite easily done and the overall improvement can be remarkable. For me since my speakers weigh over 300lbs each, I find the digital crossover, preamp, equalizer, and DAC functions awesome and better than anything else in this price range by a wide margin and I simply don't use the correction features.


Widget

Shane Shuster
08-15-2006, 12:22 PM
The room will still introduce problems when the speakers are brought back in, but at least the room will not influence the measurements.

Having said all that, I've wondered what the results would be if all DEQX measurements were taken with the mic in the listening chair. Perfect amplitude, phase and arrival time in that spot might be great, although the next seat over could be awful.
Then it might not be like a Tact. With a Tact they recommend you move the speakers close to a wall to get bass boost and a better impulse response. You put the mic at the listening position and it pulses the speakers to get a measurement. It then "fixes" level balance, time alignment, and frequency response depending on what you draw in for a target curve.

Mr. Widget
08-15-2006, 02:19 PM
Then it might not be like a Tact. With a Tact they recommend you move the speakers close to a wall to get bass boost and a better impulse response. You put the mic at the listening position and it pulses the speakers to get a measurement. It then "fixes" level balance, time alignment, and frequency response depending on what you draw in for a target curve.All measurement techniques whether using MLS, FFT or whatever process respond essentially the same way to speaker/room issues... placing the speaker near a wall and the mic at the listening position sounds pretty screwy... especially if you don't normally listen to the speakers up against the wall.

Have you used the Tact system? I know that unlike DEQX, they make a wide variety of pieces... and they are generally well regarded.


Widget

boputnam
08-15-2006, 07:01 PM
So I guess I am surprised that you haven't seen these suck outs before... maybe it is because you use Smaart to capture more room and less speaker?In the home application, surely. As Steve posited some posts back, I too measure at and optimize for the listening position. Anything else seems pointless. I don't sit at 1m distance; I sit at closer to 4-5m, so there is where I measure the response.

Also, as per the multitude of pics of my 4345 roost, there is a nice carpet that may mitigate floor bounce.

Regardless, never in my personal experience have I seen a bounce that extreme. Where it possible, I would like to know the coherence of it - it may not be so very high. And in that case, I wouldn't toil over it too much anyway...

Mr. Widget
08-15-2006, 07:27 PM
As Steve posited some posts back, I too measure at and optimize for the listening position. Anything else seems pointless. I don't sit at 1m distance; I sit at closer to 4-5m, so there is where I measure the response.Well... you're wrong. :D

I should have dragged CLIO along when I was over last time.... It is best to get a nearfield (more speaker, less room) measurement to set the L-pads, amps, perhaps a bit of EQ... and then move to the listening position to tweak it a bit. You really need to start out with a "speaker" measurement so that you can correct for it's own unique issues before you try to fix the sound of the room... measuring at a great distance you get too much erroneous data... much of what the mic "sees"... we don't hear, and in many cases the room masks what we are "seeing" on the screen but are hearing. This is one of the reasons that Zilch's RTA plots look smooth but the speakers don't sound that way. (Zilch, sorry to use you as a negative example... it was the first thing that came to mind.)


Also, as per the multitude of pics of my 4345 roost, there is a nice carpet that may mitigate floor bounce. Ken had a pile of pillows on the floor between the speaker and mic. I have been able to get quite a bit of that floor bounce removed by placing a 1' high pile of Sonex sheets... that does help quite a bit. A high nap carpet probably won't affect frequencies lower than maybe 1000Hz.


Widget

Zilch
08-15-2006, 10:24 PM
This is one of the reasons that Zilch's RTA plots look smooth but the speakers don't sound that way. (Zilch, sorry to use you as a negative example... it was the first thing that came to mind.)Oh, POO, Widget.

I've also posted some of the most unsmooth RTA plots ever seen in these forums.

What you see is what I get.... :p

I ignore the LF, typically, 'cause I know there's little to be done about it.

And it's WRONG, anyway, unless measured nearfield or groundplane.

[Or in-box, maybe, which I haven't tried yet.... ;) ]

Mr. Widget
08-15-2006, 11:11 PM
I ignore the LF, typically, 'cause I know there's little to be done about it.

And it's WRONG, anyway, unless measured nearfield or groundplane.Exactly.... except it isn't just the lows that can be wrong... without time windowing the highs are always in question too...

You've read the "good book" ...you know what I mean. I was just pointing out that you, I, and probably everyone who has used an RTA in a smallish space and has EQ'd their speakers to look flat... are not really listening to flat speakers.


Widget

Shane Shuster
08-15-2006, 11:37 PM
All measurement techniques whether using MLS, FFT or whatever process respond essentially the same way to speaker/room issues... placing the speaker near a wall and the mic at the listening position sounds pretty screwy... especially if you don't normally listen to the speakers up against the wall. Have you used the Tact system? I know that unlike DEQX, they make a wide variety of pieces... and they are generally well regarded.
Widget
I own a Tact system. It uses FFT. The idea behind it is that you put the speakers closer to the wall for better coupling and then the room correction cuts the bass back. Less woofer excursion and more amplifier headroom. If you move the speakers or change the toe-in you have to run the measurement process again. It works great on some speakers and less on others. I liked some pulled out in a normal position, others needed the wall.

I haven't tried measuring close like you describe. I guess I always figured if the listening position is where I want it to be flat, then thats where I should measure. I will try measuring 18" out or so this weekend and see if it is better.

Depending on which speaker I was measuring, I have the same or worse frequency dip that Ken has in roughly the same spot. It depended on the woofers height.

I do have a couple of questions for anyone. I somewhat know how to read a impulse response graph. But what does a really great system's graph look like. The first blip should die down right away and stay flat, right?
Any further blips are reflections or driver delays? Theoretically perfect would be a sharp line blip then nothing?

The 2nd question is using a FFT, what is considered a good at the listening position frequency response. (20-20k) Plus or minus 6db is the best I could get in my small uneq'd, untreated room.

Thanks.

Ian Mackenzie
08-16-2006, 05:02 AM
Shane,

Reading and interpreting these graphs as as much a science as it is an art and the same applies to the measurement techniques.

The graphs help confirm what you might be aiming for with a design but they should never be used as a yard stick of how it sounds.

Usually the early reflections 3ms < are what influences the tactile transient response and they relate to the baffle surface and diffraction effects around the driver. There should be rapidly damped ringing after the initial pulse. Small glitches immediately after the pulse may suggest early reflections and multiple glitches may mean time alignment issues in a multiway system. Waveguides are in vogue as they can help minimise early reflections in small to medium size systems.

John Dunlavey formerly of Duntech did a lot of research on transient impulse testing and you may find a few references on the www if you do a search. In short its a complex topic and there is as much agreement as there is disagreement on what matters and what is important in speaker design.

I am not aware of a loudspeaker than can product a perfect square wave.

The thing is many modern systems like the Duntech and Vanderstein systems claim transient perfect behaviours but they just don't have the same snappy transient capability or realism of a JBL or a TAD or Altec system which oddly enough may not exhibit well controlled early reflections or time alignment. Why? Dymanic power compression.

Just trust your ears.

Bo or Mr Widget may be able to assist with your last question.

My suggestion is to attempt to control worst of the bumps in response by careful selection of the listening position and careful selection of room furnishings.

Shane Shuster
08-16-2006, 11:51 AM
Thanks Ian. Thats about what I was guessing.
It seemed like most webpages and books like The Master Handbook of Acoustics assumed the reader has already measured lots of rooms or is a sound professional.

Mr. Widget
08-16-2006, 12:01 PM
I own a Tact system. It uses FFT. The idea behind it is that you put the speakers closer to the wall for better coupling and then the room correction cuts the bass back. Less woofer excursion and more amplifier headroom. If you move the speakers or change the toe-in you have to run the measurement process again. It works great on some speakers and less on others. I liked some pulled out in a normal position, others needed the wall..The problem with sticking the speakers up against the wall is two-fold. First, while it is true that you will get better coupling and therefore "more" bass, it isn't linear... you will not get an even increase in bass... this is even more the case with corner placement. Of course some people want more bass and aren't terribly concerned about the quality of that bass or simply never paid enough attention to notice that they have created a quality of bass that isn't particularly natural sounding... They don't mind having certain notes accentuated and others muted... that's fine. Others are dealing with domestic aesthetic concerns and these weigh more heavily than getting the finest reproduction possible... I can understand that. I am guessing that you are not in either of those camps and are after the best possible sound based on your comments.

Secondly, for most speakers, placing them near the walls interferes quite dramatically with sound stage depth and image specificity.




I haven't tried measuring close like you describe. I guess I always figured if the listening position is where I want it to be flat, then thats where I should measure. I will try measuring 18" out or so this weekend and see if it is better.I have no practical experience with any of the TACT equipment, but if you can first measure just your speaker and correct any frequency or phase anomalies that are inherent in it and then make additional adjustments based on it's actual in room placement I am sure you will have better results. If you can drag the speakers outdoors to do the initial measurements and corrections you would be better off especially considering that your room is small and not controlled.




I do have a couple of questions for anyone. I somewhat know how to read a impulse response graph. But what does a really great system's graph look like. The first blip should die down right away and stay flat, right?
Any further blips are reflections or driver delays? Theoretically perfect would be a sharp line blip then nothing?I pretty much agree with what Ian said... a clean straight line is the ideal, it doesn't exist, and systems that approach that ideal are not necessarily the ideal speakers. It is simply more complicated that we are able to measure at this time.




The 2nd question is using a FFT, what is considered a good at the listening position frequency response. (20-20k) Plus or minus 6db is the best I could get in my small uneq'd, untreated room. That is is the realm of acceptability. You can probably do a little better... at some point your room will take over and there is nothing you can do.


Widget

boputnam
08-17-2006, 06:22 PM
Well... you're wrong. :D

I should have dragged CLIO along when I was over last time.... It is best to get a nearfield (more speaker, less room) measurement to set the L-pads, amps, perhaps a bit of EQ... and then move to the listening position to tweak it a bit. You really need to start out with a "speaker" measurement so that you can correct for it's own unique issues before you try to fix the sound of the room... That's exactly what we did, except used Smaart. The L-pads were and are set to "0", best as can be interpreted from the decal on the foilcal. We made some minor adjustments near-field.

Then we moved to the listening position and fine-tuned things.

But, what you are suggesting really requires two EQ's - one for attaining a flat-as-possible speaker response and leaving it set that way (with my road system I use the KT DN9848 loudspeaker processor with parametric and time-align the mains and subs); the other EQ is to mitigate the room affects (for this I use the KT DN 370 graphic). At home, I feel I get very good results using just the DN370 and optimizing for the listening position. It keeps uneccesary filters out of the signal path.

Mr. Widget
08-17-2006, 06:47 PM
That's exactly what we did, except..That's sorta what we did. I would have pulled both speakers out from the wall to flatten them, and then placed them where they sound best in the room... in this case Susan determined where they sound best ;) so that tosses a bit of a wrench in the works, but what the hell the client is happy so all is good, right?

I don't use two sets of EQs... I save the settings from nearfield and then tweak them... comparing the tweaks to the pure nearfirld settings until I (the client, in this case) am happy... it takes about an hour to get close and then a lifetime to complete.:D


Widget

Ian Mackenzie
08-17-2006, 09:45 PM
The paper speed, scale and division make a big difference to how the graphs appear. Smoothing and 1/3 octave pink noise can make a graph look very presentable for marketing. But on the other hand how audible is every wiggle and glitch?

I tend to shoot for overall balance in the near field with scale so all the drivers have balanced levels as a priority. If there are specific issues with the near field graph I look for the cause. ie room or driver or crossover. Then determine if those issues are likely to impact at the listening position. I think there can be an over emphaisis to obtain as super smooth response without due attention to mitigating other causes of less than optimium subjective performance.

By way of example a Wilson system can be measured in room and show all sorts of response defects. But I have yet to see anyone complain about them in that they sound bad because the review graph is not perfect and tweek the response with 1/3 active eq.

Mr. Widget
08-17-2006, 10:02 PM
By way of example a Wilson system can be measured in room and show all sorts of response defects. But I have yet to see anyone complain about them in that they sound bad because the review graph is not perfect and tweek the response with 1/3 active eq.Yeah, but those speakers are for audiophiles... sorry... couldn't help myself. :rotfl:

BTW: One of our own (not moi) recently traded in his Altecs, JBLs, and TADs for a Wilson system. Who knew?

I agree about your subjective vs. objective measurement comment though. In reality the final analysis is all about the subjective quality of the system. That said the measurement tools are extremely helpful in setting up the system. As you know I have been doing a bit of amp swapping lately and setting the individual levels to a fraction of a dB and determining whether an amp inverts signal or not are not the sorts of things even a critical listener might notice right away, but may sway their subjective opinion... once you've checked to make sure that all of your amps are in phase and the settings are matching then you can subjectively evaluate without an anomalous bias.


Widget

Ian Mackenzie
08-18-2006, 12:38 AM
Yes,

I will be deemed a certified audiophile shortly.

Eq will be taboo

Ian