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Author Topic: A look at optimum smoothing in speaker EQ  (Read 2330 times)

Mark Wilkinson

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Re: A look at optimum smoothing in speaker EQ
« Reply #20 on: August 16, 2020, 10:06:33 am »

For comparison, the SynTripP uses two B&C 10CL51 10" with a Celestion CDX14-3050 three inch diaphragm 1.4" exit high frequency (HF) driver come in at just under 34 pounds (15.5 kilos) for the 26.5" wide x 11.25" tall, 15" deep (67.3 x 6.075 x 38.1 centimeters) main cabinet. The secondary horn is 41" wide x 25.5" tall x 7.5" deep (104.1 x 64.8 x 19 centimeters), weighing about 5 pounds (2 kilos). The horns nest like Dixie cups, attached by a ratchet strap and bridle assembly to the main enclosure in about the time it takes to tie a pair of shoes. Nominal 90 x 40 degree dispersion.

Used a DBX DriverackPA for the polars below, not enough filters to take care of everything, and some "conical blues".
Seems the ported (81Hz Fb) SynTripP has more consistent (no reversals) below about 600Hz, while your 90x60 is better behaved above.

Anyway, better hit post before another lightning outage, just found my "uninterruptible power supply" is not.

Art

Hi Art,
Have always admired your SynTripP...i think it may me the lightweight champ of the world.
Nice job with tuning. In keeping with this thread, may i ask what your procedure is.....
as in, do you tune to on-axis or some angle near on-axis, and then see how well it holds up off-axis?
Or do you have some other routine that takes in off-axis at the beginning?

I'm a little surprised your measurements don't show more pattern flip or waistbanding.
i've often read pattern flip blooms when the aspect ratio, horizontal to vertical, exceeds somewhere around 1.5-1.6X.
But the SynTripP's 90x40 at 2.25X appears to looks fine, for at least the horizontal.
What'd you do right?  :)

@ Frank, cool, thx..
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Art Welter

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Re: A look at optimum smoothing in speaker EQ
« Reply #21 on: August 16, 2020, 01:33:18 pm »

.. do you tune to on-axis or some angle near on-axis, and then see how well it holds up off-axis?
Or do you have some other routine that takes in off-axis at the beginning?

I'm a little surprised your measurements don't show more pattern flip or waistbanding.
i've often read pattern flip blooms when the aspect ratio, horizontal to vertical, exceeds somewhere around 1.5-1.6X.
But the SynTripP's 90x40 at 2.25X appears to looks fine, for at least the horizontal.
What'd you do right?  :)
What was "done right" is the vertical polars weren't shown, so you can't determine the pattern flip or waistbanding ;^).

As far as the tuning routine, nothing too ground breaking- rough in response on axis, if the on axis corrections don't work off axis, decide what compromise works best overall.

Art
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Frank Koenig

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Re: A look at optimum smoothing in speaker EQ
« Reply #22 on: August 16, 2020, 01:47:56 pm »

Hey Frank,  was thinking about your work with the SH-46.....
How have the polars looked 'as is' with the passive xovers?  Do they generally all more or less fall as angle increases, or do some areas of response increase, even above onax response?

Mark, on polars. I have data for the as-is SH-46 but they're so old now I'd have to do some fooling around to plot them. So it's hard for me to answer that question. The measurements (below) I have for the modified SH-46 (replaced the HF driver with B&C DE980TN and developed new crossover) were taken 13 ft above ground level at a 10 ft measurement distance yielding 16 ms of pseudo-anechoic data corresponding to a frequency resolution of 63 Hz. So there's not too much detail in the range of frequencies where I would expect to see pattern flip. I've blown up the lower-left corner of my usual log-mag plot. This is for a total of 17 measurements taken at 5 deg increments with 6 in the horizontal, 3 in the vertical and one tossed out as an outlier. (0, 5, 10, 15, 20, 25 horiz. and 0, 5, 10 vert.) The colors run through the rainbow starting onax (red) and going through all the verticals for each horizontal. This is admittedly a lousy polar representation but it's what I've got at the moment. However, there is evidence, if I'm reading it right, of some mild pattern flip around 600 Hz. The good news is that the total variation in the response is only ~4.5 dB, which may be why I never gave it any thought until now.

When I'm ready for another programming project maybe I'll work on a better polar representation. What would you like to see?  Possibilities include a clearer collection of frequency responses, traditional polars like you see in a mic spec sheet, balloon plots like CLF, or beam width diagrams. Maybe the best would be to write out the data in CLF format and use the available viewers.

A problem is that unless I get a taller tower (unlikely), I'm stuck with dimishing frequency resolution below ~1 kHz. Ground plane measurements are likely useless for polars. Speaker on the ground pointing up gets confounded as the ground comes into play with dropping frequency. What do you think?

--Frank

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Mark Wilkinson

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Re: A look at optimum smoothing in speaker EQ
« Reply #23 on: August 17, 2020, 10:05:17 am »

Mark, on polars. I have data for the as-is SH-46 but they're so old now I'd have to do some fooling around to plot them. So it's hard for me to answer that question. The measurements (below) I have for the modified SH-46 (replaced the HF driver with B&C DE980TN and developed new crossover) were taken 13 ft above ground level at a 10 ft measurement distance yielding 16 ms of pseudo-anechoic data corresponding to a frequency resolution of 63 Hz. So there's not too much detail in the range of frequencies where I would expect to see pattern flip. I've blown up the lower-left corner of my usual log-mag plot. This is for a total of 17 measurements taken at 5 deg increments with 6 in the horizontal, 3 in the vertical and one tossed out as an outlier. (0, 5, 10, 15, 20, 25 horiz. and 0, 5, 10 vert.) The colors run through the rainbow starting onax (red) and going through all the verticals for each horizontal. This is admittedly a lousy polar representation but it's what I've got at the moment. However, there is evidence, if I'm reading it right, of some mild pattern flip around 600 Hz. The good news is that the total variation in the response is only ~4.5 dB, which may be why I never gave it any thought until now.

When I'm ready for another programming project maybe I'll work on a better polar representation. What would you like to see?  Possibilities include a clearer collection of frequency responses, traditional polars like you see in a mic spec sheet, balloon plots like CLF, or beam width diagrams. Maybe the best would be to write out the data in CLF format and use the available viewers.

A problem is that unless I get a taller tower (unlikely), I'm stuck with dimishing frequency resolution below ~1 kHz. Ground plane measurements are likely useless for polars. Speaker on the ground pointing up gets confounded as the ground comes into play with dropping frequency. What do you think?

--Frank



Big thanks Frank,
I don't mean to be asking you to come up with very detailed, hi-resolution info.   
It's always nice to see careful measurements, but i was just trying to get your big picture take on conical horn pattern flip, and show why I'm interested due to DIY synergy attempts.
I guess it all gets back to the thread title..'optimum smoothing in speaker EQ'..cause i see that, along with xover selection and acoustic time delays, as the only ways of smoothing out polar variations. 
Since xover freq/type/order selection and acoustic time delays tend to become relatively fixed when tuning, EQ's seem to be the big variable. 
How fine to EQ, and to what axis, or to what set of averaged measurements?
But again, just looking for big picture impressions. I enjoy measurements and speaker building a lot, but the real purpose is to simply hear something better than I've heard before.

My polar measurement aren't taken in quite a clean environment as yours.  They are off a deck that faces into a very open setting,  but the deck has a high vaulted roof over it, and it's about 12 ft back to the house wall from where speakers sit. So reflections get in for sure.
Mic is on a boom about 15ft off the ground, hanging from a roof beam. Mic to speaker distance is about 9ft.  The boom rotates and hold 3 mics vertically spaced, but i'm finding i like a turntable a little better.
Anyway, just saying there's a lot of slop in my polar measurements.
That said, my builds do keep sounding better, especially indoors, as polars get smoother.
I really don't know what to do to look for better sound, other than work on polars.  It's so easy to get on-axis mag and phase flat today, that's no longer even a tuning issue imho.



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Mark Wilkinson

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Re: A look at optimum smoothing in speaker EQ
« Reply #24 on: August 17, 2020, 10:08:34 am »

What was "done right" is the vertical polars weren't shown, so you can't determine the pattern flip or waistbanding ;^).

As far as the tuning routine, nothing too ground breaking- rough in response on axis, if the on axis corrections don't work off axis, decide what compromise works best overall.

Art

Haha, yes!...what's vertical anyway ?  ;)

Yep, that's pretty much what i've come to...see if there are any real off-axis problems and start trading off..
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Frank Koenig

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Re: A look at optimum smoothing in speaker EQ
« Reply #25 on: August 17, 2020, 12:10:30 pm »

Mark, I just realized something about that last plot I put up. It's not true polar data because each trace is individually amplitude-normalized and there was less than fanatical control over relative mic distance, although it should be pretty close. This is because I'm going to combine, one way or another, those traces to get the correction curve and their individual gain scaling goes away. You might call them "relative polars". The polars are there in the original data, to the extent that I controlled mic distance, but I need to change the process a little to get them out.

Since I'm not actually designing and building horns, as you are, I'm powerless to do anything about the polars anyway beyond choosing who in the audience to favor with the correction curve. True though, that soon as I change a driver or crossover the speaker is no longer a "black box" and I should look at the whole picture. Perhaps I've met my match. That Klippel rig is NOT in my future  ;)

--Frank
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Mark Wilkinson

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Re: A look at optimum smoothing in speaker EQ
« Reply #26 on: August 20, 2020, 12:37:42 pm »

Mark, I just realized something about that last plot I put up. It's not true polar data because each trace is individually amplitude-normalized and there was less than fanatical control over relative mic distance, although it should be pretty close. This is because I'm going to combine, one way or another, those traces to get the correction curve and their individual gain scaling goes away. You might call them "relative polars". The polars are there in the original data, to the extent that I controlled mic distance, but I need to change the process a little to get them out.

Since I'm not actually designing and building horns, as you are, I'm powerless to do anything about the polars anyway beyond choosing who in the audience to favor with the correction curve. True though, that soon as I change a driver or crossover the speaker is no longer a "black box" and I should look at the whole picture. Perhaps I've met my match. That Klippel rig is NOT in my future  ;)

--Frank

Thx Frank, I'll be very interested if you find an averafing technique you really like.
I keep playing with averaging raw polars using Smaart or FirDesigner, trying the various options, dB vs power, etc.
But it seems such options are a lot less important than determining exactly which polars to average. 
So far, I've been getting best results holding the averaging to within +/- 20 degrees of onax.
If I try to average in beyond that, not so good.
So beyond 20 degs, I just look for bigger problems that trend all the way to coverage boundaries. Then try to correct them, and see how bad it screws up inside 20 deg. 
Kinda a two-part, average first, then go to a manual approach maybe kin to eyeballing response envelopes.

Anyway, here's another project i have going, that used that process. 
A friend gave me a pair of old PAS horns, that i believe was made by DDS. They're about 30"Wx17"Hx16"D.
Below are the horiz polars. Bms4594he on it, hpf at 400Hz, xover at 5.8kHz.
Made indoor close, no gating (i no likey gating), 1/6 smoothing.
Used your rainbow ordering for 10deg takes, so violet =onax, red -50 deg.
Hope verticals don't suck too bad, i kinda like these....

It's amazing to me how much easier it is to get smoother, none-waistbanding polars from manufactured horns than my conical synergy builds.
That's why I keep hoping to see some polars from someone who actually knows how to build one right, aka Mr TD! 
Need to see how much improvement room there is.....to find out whether to play with different secondary flare sizes/angles...etc...cause that's kinda a PIA...
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Art Welter

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Re: A look at optimum smoothing in speaker EQ
« Reply #27 on: August 22, 2020, 11:38:55 am »

It's amazing to me how much easier it is to get smoother, none-waistbanding polars from manufactured horns than my conical synergy builds.
That's why I keep hoping to see some polars from someone who actually knows how to build one right, aka Mr TD! 
Need to see how much improvement room there is.....to find out whether to play with different secondary flare sizes/angles...etc...cause that's kinda a PIA...
Mark,

Straight sided conical horns fit the multiple entry concept nicely, but as you are aware, are not the best approach for consistent polar response.

I don't have a PC anymore, so don't know if the EASE data on DSL's website provids polar response, but judging by the "flagship" SH-50 polars (and Hornresp sims) your results are about as good as you can expect from conical expansions.

Art
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Mark Wilkinson

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Re: A look at optimum smoothing in speaker EQ
« Reply #28 on: August 25, 2020, 03:44:16 pm »

Mark,

Straight sided conical horns fit the multiple entry concept nicely, but as you are aware, are not the best approach for consistent polar response.

I don't have a PC anymore, so don't know if the EASE data on DSL's website provids polar response, but judging by the "flagship" SH-50 polars (and Hornresp sims) your results are about as good as you can expect from conical expansions.

Art

Thank you Art,

Appreciate your ongoing help, here and at DIY, re working with conical horns.

And yeah, I've kinda come to realize the price of a synergy's multiple drivers on a single horn, is the less than optimal straight-wall horn type it takes to mount the drivers.
I guess that just means progress is begging for some really experienced smart DIY guy (hint hint  ;))... to figure out how to fit multiple drivers onto an OS guide or something...
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Art Welter

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Re: A look at optimum smoothing in speaker EQ
« Reply #29 on: August 26, 2020, 03:03:11 pm »


I guess that just means progress is begging for some really experienced smart DIY guy (hint hint  ;))... to figure out how to fit multiple drivers onto an OS guide or something...
That has already been done by a number of guys using 3d printing.
But 3d printing is s-l-o-w, if you want multiple cabinets you need molds.
And you better have it all worked out before committing to the mold costs.
Held on to my 1979 system molds for at least 10 years after that system became obsolete in two years.

Was thinking of making some molds for a few different multiple entry horns about 4 years ago, but fortunately heart and mental health issues, a brain injury, a few hurricanes, colon cancer and hearing loss prevented me going down that rabbit hole again, the market needs new product like I need another hole in my head ;^).

That said,  finally going to use the last of the B&C drivers (4NDF34-8) Bennett Prescott was kind enough to let me demo before things shifted into slow. Got my ass out to the trailer, hauled tools into the apartment (sweated through a set of clothes), let the "fun" begin again!

It's going to be a mixture of about 5 decades of shit crammed in one cubic foot, and will be quite loud for it's size, though it still won't be close to Curt Graber HyperSpike loud.

Art
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Re: A look at optimum smoothing in speaker EQ
« Reply #29 on: August 26, 2020, 03:03:11 pm »


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