Kleos - Dipole Line Array

[wkhanna]

.........so I can build a little adapter to help me calibrate the software.

Gee, John.....
I hope you did not use the same method to calibrate your clock! :W

[Johnloudb]

Gee, John.....
I hope you did not use the same method to calibrate your clock! :W

Thanks Bill! I'll recalibrate my clock immediately.

[Johnloudb]

Hmm, well, I took some frequency response measurements in signal scope's FFT, using random white noise as the source. IOScope is for two channel transfer functions, not a simple frequency response measurement, according to Faberacoustical. But I can use it for impedance measurements, and other stuff.

Here are plots of the RD50 (top) and woofer array:

Soooo, looks like there is a considerable dip 350-450Hz in the woofer array, and I think the rise in the 150-250Hz is do to the room. These speakers are facing the length of the room which has some bad room modes. Anything below 50Hz should be disregarded.

[JonMarsh]

Hmm, well, I took some frequency response measurements in signal scope's FFT, using random white noise as the source. IOScope is for two channel transfer functions, not a simple frequency response measurement, according to Faberacoustical. But I can use it for impedance measurements, and other stuff.

Here are plots of the RD50 (top) and woofer array:

Soooo, looks like there is a considerable dip 350-450Hz in the woofer array, and I think the rise in the 150-250Hz is do to the room. These speakers are facing the length of the room which has some bad room modes. Anything below 50Hz should be disregarded.

Is there any way to turn on smoothing, like 1/12 or 1/6 octave smoothing? Most measurement programs will do this. Also, if at all possible, to separate what the speakers are doing from multiple room modes, a burst source like a sine chirp (with convolution to MLS) or an MLS pulse (repeated and averaged to improve signal to noise) will give you more info about what the speakers are really doing themselves, apart form their interaction in their current room position and your current mic position.

Still, you're making progress! :T

[Johnloudb]

I have not found any smoothing function in the software. It lets you specify the resolution in Hz only, and will let you choose the number of averages. These graphs have a resolution of 5Hz, and 8 averages. And you can see as the frequency increases the jaggies get worse, so this may be a limitation with this software. I've been looking at some other iPhone RTA software in the app store.

I wish the resolution was given in points per octave. I'll email Faberacoustical and see if I'm missing something. It does have a sweep function, that has a chirp sound (fast sweep) in signal scope, and I may experiment more with that. But, you can specify the duration of the sweep in IOScope only. The two software are very different.

I'll see what I can find out, and try to get some better measurements.

[Johnloudb]

I see there is a RTA tool 1/3 octave bands for signal scope, but I just downloaded another inexpensive software with smoothing, so I think I'll give that a shot first. Forgot to mention, the low frequency response of the RD50 is affected by a couple 300Hz F-stops at the amp input to protect the driver.

[Saurav]

And you can see as the frequency increases the jaggies get worse, so this may be a limitation with this software.

Every measurement does that, regardless of what mic / software you use. It's the nature of un-gated in-room measurements. What you're seeing is the effect of comb filtering due to reflections from the walls, floor, etc. Don't worry about it. A smoothed measurement will help you 'see through' that noise, and an experienced eye like Jon can probably see the real data in there without needing a smoothed graph.

If there's some way to export the raw measurement data from your phone to a Mac or PC, you can probably find other software for post-processing.

[Johnloudb]

Okay, I can buy a data acquisition add on to signal scope, and then view the files in Arta. So, I may give that a shot, after I try this new RTA software I just bought.

[Saurav]

See if you can save the impulse response. That will probably give you the most control in something like ARTA or HOLM Impulse, because you can then set gates and remove the reflections from the data. Of course, a gated measurement has other issues, most notable being lack of low frequency resolution. You generally have to look at a measurement in several different ways.

And then you get confused by it all and say to heck with it, and just do whatever sounds good to your ear

[Johnloudb]

And then you get confused by it all and say to heck with it, and just do whatever sounds good to your ear

Yeah, that's my plan! :T

But got to take some measurements, just to get in the ballpark, and have someplace to start with the crossover.

Here is another measurement I took of the RD50 using a different RTA software, with 1/6th octave smoothing.



Just been kind of busy doing stuff, but will get some of the woofer array, soon.

[Johnloudb]

Just want to mention again, the low end response does not roll off that early. I have a fourth order 300 Hz high pass before the amp, so it causes the early roll off.

[sfdoddsy]

Looking nice, John, but about that slot in the middle? Slot loaded port in a dipole?

Does this slot actually work to narrow the baffle?

I'm pondering something similar if I attempt one of them fancy narrow baffle dipoles a la LX521 Nao Note.

[Johnloudb]

Okay, I took measurements of the woofer finally! And it turned out kind of interesting. The first plot is that with white noise input. And if you look careful it kind of looks like a first order roll of below 600 Hz. So, I tried a Pinknoise source (1/f) and it looks a lot flatter in the frequencies of interest.

So a first order lowpass filter at 50Hz is something I'm thinking about, and also a shelving filter to bring down the frequencies above 150 Hz, so they are more in line with the lower frequencies.

But I'm going to move the speaker to the other wall where it will be when we listen, and see how that changes the response before I do any crossover work. Next up is to try what Saurav suggested. I'll take some frequency sweep measurements with the other software, as well as impulse response, and see if I can get Arta to help with that.

White Noise Response -



Pink Noise Response -

[sfdoddsy]

Pink noise is the one to use.

[Saurav]

It's a dipole, it's supposed to roll off at 6dB/octave, starting at a frequency determined by your baffle width. You need to EQ that back to flat (and take care of any other anomalies) in the crossover. The dipole compensation needs to be part of the overall transfer function applied to each set of drivers.

For example, here's what my 3-way dipole XO ended up looking like. You'll notice shelving filters on the midrange and woofer - those handle the dipole compensation. The notch filters were to deal with driver/baffle issues.



Of course, if you're only going to use the woofers below 50Hz, then the XO will take care of most of it, and you probably won't need a shelving filter for the whole dipole range. Unless you meant a high-pass at 50Hz instead of a low-pass.

BTW, now that I think about it, I'm not sure the free version of ARTA will import any other application's files. Might be a good idea to check into that before you go to the effort of exporting an impulse response. HOLM Impulse is another free PC application that might be able to import an impulse response file.

[Johnloudb]

Okay, baffle step confuses me. There is clearly more than just the baffle width that determines the baffle step frequency, right. Woofer Q? Other stuff?

Well, white noise has a flat spectrum, where as pink noise has a 1/f spectrum, but has equal power per octave. I read that pink noise looks flat on a lothrithmic scale, but I don't see why that would be the case except that RTA's do smoothing? Noise is additive. Also, that plot isn't a true logarithmic scale.

Well, truth lies in the details. What about a frequency sweep? I'll try that.

So if the pink noise is the more accurate measurement, that's wonderful because other wise I'd have to apply 24dB of equalization to get a flat response down to twenty Hz.

Well, I'll try some more things.

I have the full version of Atra, not the demo.

[sfdoddsy]

You'll still need lots of EQ. I have 22db to flatten mine. Linkwitz adds another 16 or so for his low Q drivers.

[Johnloudb]

Okay, here is a sweep with a period of 0.25 seconds. I exported the a text file and will see if Arta can import that and smooth the response.

[Johnloudb]

You'll still need lots of EQ. I have 22db to flatten mine. Linkwitz adds another 16 or so for his low Q drivers.

Well, looks like I may not have to apply too much EQ, maybe 10-14 dB below 150Hz. The more EQ needed the more sensitivity you loose and the more powerful an amp you need. So that's my concern there. I'm just not sure what's room modes in this picture.

I'll try the speaker against a different wall and see what happens.

[sfdoddsy]

As Saurav said, it's not baffle step, it's dipole roll-off due to front back cancellation.

It looks like you have your dipole peak at around 600-700, then it is rolling off at 6db an octave below that. This close to what Edge predicts for a baffle that size.

Checking my settings, I actually dial in a 20db shelving filter to have my woofers flat to 20Hz. However, the amp doesn't see that much boost because I high pass at 40Hz to my subs.

How low are you hoping to go?

When I first started designing my speakers I used pink noise and a program called TrueRTA. The advantage of an RTA and pink noise is that it is easy to see changes in real time.

The disadvantage is that you can't separate the speaker from the room.

Then I switched to ETF and now I use REW because it is free and many people use it so it easy to get advice.

Another way of handling the dipole peak is to use it to your advantage by applying your crossover lower, at 200Hz or so. The combination of the peak and crossover roll-off cancel each other out and give you flat response.

In theory.

[Johnloudb]

As Saurav said, it's not baffle step, it's dipole roll-off due to front back cancellation.

It looks like you have your dipole peak at around 600-700, then it is rolling off at 6db an octave below that. This close to what Edge predicts for a baffle that size.

Checking my settings, I actually dial in a 20db shelving filter to have my woofers flat to 20Hz. However, the amp doesn't see that much boost because I high pass at 40Hz to my subs.

How low are you hoping to go?

When I first started designing my speakers I used pink noise and a program called TrueRTA. The advantage of an RTA and pink noise is that it is easy to see changes in real time.

The disadvantage is that you can't separate the speaker from the room.

Then I switched to ETF and now I use REW because it is free and many people use it so it easy to get advice.

Another way of handling the dipole peak is to use it to your advantage by applying your crossover lower, at 200Hz or so. The combination of the peak and crossover roll-off cancel each other out and give you flat response.

In theory.

Oh, I though the dipole roll off was baffle step. Okay, good to know. This woofer also has a rise at the 500-600Hz region so I'm not sure that the roll off starts at 600Hz but maybe at 200Hz? In any case it all needs to be taken care of.

I still need to move this speaker and take some more measurements and see what that turns up.

Bought one Seas L26RO4Y sub for my dad for Christmas, to put in our IMF transmission line loudspeakers. I chose it because of it's low Qts and it's Fs of 24Hz wasn't too low, plus it's a really good sub. Just had a hunch, based on experience with the other subs, that it would work well and it does! I lowered tuning on the port a bit, and got flat bass to 20Hz, after taking care of a 30Hz room mode.

Since it worked out well I ordered one for the other sub.

[Johnloudb]

sfdoddsy,

I forgot to mention, I made a type-O when I said I was going to equalize to twenty Hz in an earlier post. I'm just going to use enough equalization to extend the response to 50-60 Hz. As you can see I've got the low frequencies taken care of.

Thanks for the input! You and saurav have really helped.

[Johnloudb]

Okay, I need to update on my progress here. Been kind of preoccupied with the subs getting them dialed in, but did get some measurements of my dipole on the other wall awhile back. And I took measurements at different distances and the response really changes, but at the minimum listening distance of 10 feet looks a low pass filter with a corner of 100-120hz and 12dB of boost would give a pretty flat response to a 600hz where I would turn it into a third order butterworth, or perhaps a 4th order Bessel.

My computer broke and I've switched to Windows and got an HP Envy dv6t laptop on the way. I've been a Mac guy forever but all the software I need is in Windows and I got a more powerful machine for less than if I went with a Mac. I'll no doubt miss my Mac and Windows 8 is just plain strange looking, but I'll get used to it. Most of the world uses it so I suppose I can too.

[JonMarsh]

I'll no doubt miss my Mac and Windows 8 is just plain strange looking, but I'll get used to it. Most of the world uses it so I suppose I can too.

I was just thinking it was time to hear back from you soon, glad you're ready for some more progress. I switched in 2005, no regrets, and I do use boot camp on a few systems to run LspCAD and Altium Designer and SIMetrix, but that's pretty much the limit of my Windows involvement these days- Fuzzmeaure has replaced my Praxis, and high level power simulation is done in PLECS, and of course the miniDSP and REW tools, and Gecko Simulator, being Java based, run on either.

I even bought another copy of WIN7 last October, knowing I'll buy a new Mac Pro when they're out, and NOT wanting WIN8 on the desktop. A lot of strange design decisions, there, which are coming back to bite them. Already bit Sinofsky. l

[Johnloudb]

I used boot camp too. I had a Mac Mini and it's small hard drive and limited memory became a liability to the point the computer was just really slow, because the HD was full. Then it developed an overheating problem, best I can tell ... A dead fan maybe or perhaps something else, and it shuts down after a period. Anyway it is six years old, and I needed bigger and faster. Couldn't really afford a MacBook Pro 15" right now, so I got a nice windows machine. Hope I'm happy with it.

[Johnloudb]

Boy, time flies when you're having fun. Time for a monthly update! Soon after I got it, I took the HP back, because it was noisy, at least too noisy for me. And I went searching the internet and found a nice quiet Lenovo Carbon X1 portable with an SSD, and near silent fan. And I found it reading the very nice in depth reviews on this site: http://www.notebookcheck.net/

They do emissions (noise measurements) in their reviews which I have not found up to this point. It's great! I do not like noisy computers! They really cover everything in their reviews.

I won't actually receive the computer till March 5th though, since it's custom configured and they take their time.

But I am working on re-arranging our listening room, getting ready for my speakers.

John

[JonMarsh]

well, that's cool, John- but where's the update on the speakers!?! This isn't a DIY laptop forum, you know! :W

[Johnloudb]

Ha, ha unfortunately my speaker progress is currently stalled - I need a computer to finish up with measurement analysis and model my crossover. I know I don't need to tell you that the computer is an important tool in speaker design.

[Evil Twin]

Ha, ha unfortunately my speaker progress is currently stalled - I need a computer to finish up with measurement analysis and model my crossover. I know I don't need to tell you that the computer is an important tool in speaker design.

Perhaps you should consider one of the high grade implants available in the Seinar sector- powered from your own neuro system, battery life and interface become non-issues. Then you might be capable of the productivity which a project like this demands...

[Johnloudb]

Perhaps you should consider one of the high grade implants available in the Seinar sector- powered from your own neuro system, battery life and interface become non-issues. Then you might be capable of the productivity which a project like this demands...

Very tempting, but I feel that path leads to the dark side! Once implanted I would no doubt be under the control of dark forces and would become another pawn to the dark emperor. Very tricky ....

I am about to start work installing drivers in the second speaker, but also got to get the listening room in order. Room acoustics are half the battle!

[Hank]

Room treatment you are doing is a good thing, young Luke.

[Johnloudb]

Room treatment you are doing is a good thing, young Luke.

Yes, I think so. We've had RPG skyline defusers on the back wall for a long time. They do a great job. My dad has a bunch of them in the garage so will be placing some behind my speakers once I get the room reorganized, equipment moved and some boxed stuff moved out.

Image not available

[Johnloudb]

I'm going risk it and post an update. I got my computer a few days ago and have been setting it up. Very, very happy with it! Quiet, quiet, and even silent most the time. I'm also very happy with Windows 7 Pro as they have apparently copied enough of Apples OS X features to make it very pleasant to use.

And yes, I have done some more work on my other speaker trying to catch it up to the other one. Had more problems mounting the RD50 as it had a small defect where the steal was folded at the bottom, and it didn't fit perfect cause it was overlapped which make it thicker at that end. So have to route out more wood there, tomorrow as I'm tired now after Yoga class earlier.

John

[Hank]

Solid state drive?

apparently copied enough of Apples OS X features to make it very pleasant to use.

Ouch! :smackbutt: That's telling Bill Gates!

I sense a listening impressions post coming down the pike in a week or so!:W

[BobEllis]

At least you got Windows 7 not Windows (H)8 - described as a good present for an enemy. That one tries to be a phone.

[Johnloudb]

Solid state drive?

Yeah, it has a 256GB SSD drive

Ouch! :smackbutt: That's telling Bill Gates!

I sense a listening impressions post coming down the pike in a week or so!:W

Well, we can always hope ... here's to dreaming! :^x A week or SO ...

[Johnloudb]

At least you got Windows 7 not Windows (H)8 - described as a good present for an enemy. That one tries to be a phone.

I hear ya, I didn't think much of Win 8 either when I tried it, crazy.

[Johnloudb]

Got the second RD 50 installed ... more to come.

[Johnloudb]

Got all the drivers installed, just need to wire them up now.

Image not available

[Hank]

John boy, that thing is boootiful!

[BOBinGA]

OK, John. First post 06-28-2010, 02:25 PM. Coming up on three years now. Let's get cracking!!
(But looking really good.)

-Bob

[Johnloudb]

Thank You Hank, without your encouragement and unwavering support my progress would be much less "speedy"

Thanks Bob, yes, I just always have other "issues" competing for my attention and right now it's my friend Nickie! She's a very good person, I really like her. I will go wire up the drivers now ...

[Johnloudb]

Oh dear, I seem to be short of wire! I'll have to order some more now!

Update: wire ordered will be here Mon or Tues

[Hank]

Uh-oh - women and DIY speakers: Like Water for Chocolate. I too am distracted by a lady for some months now. She has agreed that I will be her first date after emerging from her "transition period" after divorce. To say she is fantastic would be an understatement: intelligent, funny, interesting and she is a triathelete (and built like a brick s__thouse). Don't see what she sees in me, frankly. Here's my surprise for our first date on the 23rd: http://greaturbanrace.com/event2013_austin.php
John boy, I DO understand your distraction :W

[Hank]

Judge: "The jury is hereby instructed to completely ignore witness Hank's recent post as irrelevant, immaterial and unrelated babbling."