baffle roll-off chart

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JohnR

Re: baffle roll-off chart
« Reply #40 on: 29 Apr 2017, 03:16 pm »
Is there di-pole modeling in Uni-box?

No, there is not.

A simple (istic) program for that is Edge, which the OP responded all the way back in post 3 that he had been pointed to.

You can refer to the Theory sticky thread for other software and some (useful) links to theory.

JohnR

Re: baffle roll-off chart
« Reply #41 on: 29 Apr 2017, 03:34 pm »
(click the link and scroll down to see the section where i cut from and highlighted in bold)

http://www.mh-audio.nl/LoudspeakerBasics.asp

That same site has an OB project that the author built, about which he says:

Quote
The first thing about my OB's that really shocks people who think they know open baffles is that they are so strong in the bottom end.
They are concert level loud and are quite explosive at the bottom.

:dunno:

JohnR

Re: baffle roll-off chart
« Reply #42 on: 29 Apr 2017, 03:47 pm »
Here's another quote:

Quote
Frankly, the bass performance beats any other construction on these pages regardless of price. None of my other speakers even comes close to this. Listening to Niels Henning Ørsted Pedersen on This Is All I Ask, track four, "Just In Time", and you'll know what I mean. The articulation in lower registers is phenomenal and overall dynamics scary. This is close to what an upright bass should sound like.

http://www.troelsgravesen.dk/OBL-15.htm

Scott L

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Re: baffle roll-off chart
« Reply #43 on: 29 Apr 2017, 04:30 pm »
Yes, he has done a great job proving information to the community, with virtually no rewards for himself !
Compensation is usually done in the crossover:

Above the final simulation. Now, the midrange usually looks anything but nice on a open baffle due to rear-wave cancellation, but driven from the very simple crossover it looks nice and smooth. Crossover between bass and mid is around 170 Hz Hz, and the crossover slopes follow an (almost) 2nd order LR topology between bass and mid and fourth order between mid and tweeter. The latter facilitates some more upper midrange presence, something that brings the music into the room rather than being a window to the music (read OBL-11 to follow the discussion). The 8008 mid has an LCR on terminals smoothing the impedance peak at 45 Hz and a resistor by-passing C3 makes a 1st order roll-off for the mid-driver. This worked better compared to a straight 2nd order filter and made a more flat response in the 100-200 Hz area - phase is not a huge issue in this area. Having the 8008 driver on a wide baffle almost leaves no baffle step loss, hence quite some response level in the 100-300 Hz range. To overcome the bump here the large chunk of series capacitors are by-passed by R14, something you will not see in any other construction on these pages.

http://www.troelsgravesen.dk/OBL-15.htm

JohnR

Re: baffle roll-off chart
« Reply #44 on: 29 Apr 2017, 04:39 pm »
Right, the crossover is part of the design. So is the baffle shape (usually) -- it's effect in the midrange is the main reason (IMO/IME) to use a program like Edge.

Scott L

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Re: baffle roll-off chart
« Reply #45 on: 29 Apr 2017, 04:40 pm »
And here's more information regarding the front-to-back cancellation:




JohnR

Re: baffle roll-off chart
« Reply #46 on: 29 Apr 2017, 04:41 pm »
Sigh.

AJinFLA

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Re: baffle roll-off chart
« Reply #47 on: 29 Apr 2017, 05:30 pm »
For any of you who are following this thread, and wish further clarification on loudspeaker basics,

here is a place to start :
http://www.mh-audio.nl/LoudspeakerBasics.asp

That doesn't address a single technical or perceptual issue I raised. But ok, let's take a look at your suggested site
http://www.mh-audio.nl/MySystem/Projects/projects.asp#OB
Quote
The first thing about my OB's that really shocks people who think they know open baffles is that they are so strong in the bottom end.
They are concert level loud and are quite explosive at the bottom.
Specialy Ray Brown's Bass on "Moonlight Serenade" is realy impressive.
Ouch.
Ok, I have to surmise you've been kidding the whole time. Got us good.  :thumb:

hurdy_gurdyman

Re: baffle roll-off chart
« Reply #48 on: 30 Apr 2017, 02:25 am »
Man, I thought this thread died weeks ago. Imagine my surprise to find it still going...  First off, I was looking for the baffle roll-off chart just to refresh my memory a bit on basic theory, as I've been out of the game a bit. The EDGE program was much more useful, and much closer to the mark. I'd used this program several years ago but lost it in a computer crash and hadn't bothered to replace it until recently, then couldn't remember what it was called. I did see the chart a few days earlier but couldn't find it again, thus my initial query.

Giving away my age, I was listening to OB's back in the late 60's in the form of several console Hi-Fi's, some mono and some stereo. I was in music heaven! I also started taking my first music lessons back then. Since then my life has revolved around music in the full circle from creating, recording and playing it back.

I bought my first monkey coffin's, err, boxed speakers when I was 18 years old (had the consoles from about 14 years old. I was a scavenger for stereo stuff back then and still am). The box speakers were a pair of brand new Pioneer Project 100's, with a 10 inch air suspension speaker and 2 inch soft dome tweeters. I bought a 10 watt SS Pioneer integrated amp to power them. Talk about a drastic change! Going from 2-5 watt tube amp and open backed speakers to this setup was drastic. However, after a few weeks of getting used to the new rig, I was disappointed. The sound wasn't "right" somehow. I had lost something important but didn't have a clue what. Over the next 10 years or so, I went through several speaks from BIC, AR, EV and a few totally forgetable ones, and also learned to build my own. I'm not great with math, but I managed to make T/S  work for me and built a slew of speaker systems, learned to wind, design and build my own crossovers. That's when my boss at the time gave me and old Bogan mono tube amp he had in his basement. I hooked it up to a pair of AR speakers I had and WHAM!!! There was a bit of that something that was missing. Years went by while I continued both tube, SS and various box speakers speakers. Fast forward to 2002. By this time I had been a professional Folk Musician for many years, performing of eight different type of instruments and singing, been in several acoustic bands and had attended several folk fests and countless jam sessions of all acoustic music, both indoors and out. I knew what music was supposed to sound like, but never quite came out of the stereo that way. I had just got turned on to fullrange drivers again (after a late 60's/early 70's flirtation with them). I built a folded Weems TQWT/TQWP (never sure which term was correct). I was enjoying these very much with a simple Pioneer BOFU 8" driver in each and using all the whizzer tweaks I could find online at the time. If I recall, someone on the old Fullrange Driver Forum was gushing about putting some old console speakers on some plywood and getting remarkable  sound out of them. It just so happened I'd stripped an old RCA console recently for the electronic parts and hadn't ditched the speakers yet. I bought some cheap MDF, did some research, and found the old J.E. Labs open baffle speaker plans, so I built them using those 8" RCA speakers. WOW! there is the rest of what had been missing! I hardly left the living room over the next couple of weeks just listening to this. Sure, they had a peak at about 100 Hz and rolled off rapidly below that, and only went up about 8 kHz before roll-off, but every thing think between was fantastic! I then purchased on ePay as set of 10" Jensen's and 10" Zenith's. I added some old 12" woofers to the baffles nad had some great sound. By this time I'd purchased some EV LS12 fullrange drivers designed in 1958!!! I loved 'em! They sounded like music like I hear live (I'm not sure, but I suspect I hear more live acoustic music than most here). I added a pair of tweeters and took them a small audio get together just over an hours drive from my place. In attendance was two guys from the Decware Forum. JLM and Darrel Hawthorne were there. JLM had just recently purchased his Fostex F200A Brines transmission line, and Darrel Hawthorne had an elaborate and eloquent dual fullrange drive (6" Fostex, don't remember which model). We listened to both JLM's speakers on the ground floor and to Darrel's horn in the furnished basement. Both speakers sounded very good. JLM hadn't received some of the tweaks yet that he would eventually get, like baffle step correction, so his speakers weren't running optimally yet, but they still sounded mighty fine. Darrel's horns were very lively and taunt, as horns usually are. Then it was my tern with these ugly baffles (I didn't have the bass drivers hooked up) with the EV speakers plus tweeters crossed at 10 kHz. You should have seen the shocked look on Darrel face as these just made the whole end of the basement disappear. He couldn't seem to get over it. Anyway, the sound was MUSIC, and the bass was there, although only down to about 60 Hz, but was very clean. To make an already long stong story short as possible, a few months later I received a package by UPS with a pair of the earliest Hawthorne Audio Silver Iris 15" Coaxial speakers. Since then I have built several different baffles and redesigned the crossovers, late helped design crossovers for the Sterling Silver 15's, acquired a pair of 15" Augies, got better measuring equipment and spent a lot of time in trial and error.
What is all this leading to, you ask? Simple. The bass I get from this setup is astounding. I have excellent sounding bass right down to 30 Hz, as powerful as I need it to be. The Augies are driven by a single 250 watt Rythmik Plate Amp, the coaxial SSI's are driven by a 60 watt PP TAD-60 tube amp.
I have had guests have their jaw drop when they hear this deep and powerful bass without a hint of box boom, and the room filling sound that those OB coaxial speakers make. You have to hear them to appreciate them. The Augies mate well with my old EV LS-12's and a new set of Caintuck Audio Betsy's I pick up from Randy (I bought the drivers, made the baffles from a pattern he sent). All sound great and very close to real music sounding (nothing can quite sound like the real thing. but one can get close).

So, just for the record, I couldn't care less what theory and math programs say. This OB stuff makes the most realistic reproduced bass I have ever heard except maybe front horn loaded bass, which I have also heard. They sound similar in the ways that matter. I have never, ever heard a box speaker sound this real. And it does it with all kinds of different music, not just acoustic. I get clean music from my SSI's up over 100 dB (louder than I would ever listen, as it just plain overloads the room up there). BTW, I have measurements I've taken from time to time over the last few years that back this up. I "listen" to the speakers as well as measure them. I don't listen to theory and math programs, just like I don't read the music coming out of my speakers.

Dave  :green:

PS: Please excuse spelling errors. I had a stroke back in December and lost much of my vision. Everything is blurry and a real strain to read and type accurately.

Odal3

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Re: baffle roll-off chart
« Reply #49 on: 30 Apr 2017, 04:19 am »
Dave - thanks for sharing that great story. I very much enjoyed reading it!

pompon

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Re: baffle roll-off chart
« Reply #50 on: 6 Jul 2017, 02:46 am »
Just to show what I get at home with "AE Dipole 15"

OpenBaffle 18 inch wide (no wings)
1 x Dipole 15 per baffle
Room 9.5x12 feets (with diy basstraps and acoustic panels (like GIK TriTraps (bigger)+ 244's panels)

Mesurement from the listening position with Dayton EMM-6 calibrated microphone.

2 Mesurements (left and right)



The hole at 105hz is an acoustic problem caused by my door (open). So just need 2 EQ point to get reasonable flat frequency 20-250. Add another point to reach 400hz ...

I put the crossover at 250hz.


hurdy_gurdyman

Re: baffle roll-off chart
« Reply #51 on: 6 Jul 2017, 02:27 pm »
Pompon,

The chart shows plenty of bass. Who'd want more? Here is a measurement I took a couple of years back of my 10" Sterling Silver Iris with 15 inch Augies. Measurements are with both speakers going from the listening seat about 10 or 11 feet back for the first graph, and just one speaker at 1 meter for the second graph.

Dave  :green:







Here is one speaker at one meter showing dispersion. I had a separate horn (QSC) on the Radian 475 driver for both measurements.







hurdy_gurdyman

Re: baffle roll-off chart
« Reply #52 on: 6 Jul 2017, 02:34 pm »
And here is the current Caintuck Audio Betsy speakers from the listening seat. I'm using a different measuring program, as I haven't been able to get REW to work right in my new computer.











I am still working on integrating the 15 Augie to the Betsy speakers. Getting closer. The Augies are not in the ideal spot, but put in corners for convenience for now.


hurdy_gurdyman

Re: baffle roll-off chart
« Reply #53 on: 11 Jul 2017, 12:09 am »
Up to date graph of Caintuck Audio Betsy and Hawthorne Audio Augie after spending an afternoon tweaking the crossover. Bass is "adequate".




rabbit

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Re: baffle roll-off chart
« Reply #54 on: 11 Jul 2017, 05:26 am »
as your dispersion measurement shows, the low end is way down without EQ. starts rolling off around 200? cant measure bass indoors. the highend is also problematic as the wavelengths are so small.
here is an outdoor of the stock silver iris for comparison.
http://cdn.avsforum.com/6/61/61c0569a_vbattach171770.jpeg

hurdy_gurdyman

Re: baffle roll-off chart
« Reply #55 on: 11 Jul 2017, 02:43 pm »
"as your dispersion measurement shows, the low end is way down without EQ. starts rolling off around 200? cant measure bass indoors. the highend is also problematic as the wavelengths are so small.
here is an outdoor of the stock silver iris for comparison.
http://cdn.avsforum.com/6/61/61c0569a_vbattach171770.jpeg"

That is a 1 meter measurement. Open baffle on moderate width baffles is always thin in the bass until you move back a ways. The listening seat actually had too much bass from that setting and had to be cut. I'll try and find a listening seat measurement from that particular speaker configuration. All of the OB's I've had in recent years use the Hawthorne Audio Augie 15" bass augmentor. All of them get to below 30 Hz at the listening seat. It's very easy to get too much bass from where I sit, use the measdurement charts to get things balanced. The only eq I use is what the Rythmik plate amp has, which is a variable frequency parametric boost/cut control for one frequency. Nobody but a true basshead would want more bass for anything but music sound effects.

Dave

hurdy_gurdyman

Re: baffle roll-off chart
« Reply #56 on: 11 Jul 2017, 02:50 pm »
Here is the same configuration at the listening seat about 11 feet back with both left and right speakers going.

Dave




hurdy_gurdyman

Re: baffle roll-off chart
« Reply #57 on: 11 Jul 2017, 04:03 pm »
"here is an outdoor of the stock silver iris for comparison.
http://cdn.avsforum.com/6/61/61c0569a_vbattach171770.jpeg"


As for outdoor measurements, I don't use it outdoors, only in my living room. Yes, it rolls off in open air, but careful  matching of the Augie and where it's placed in the room, there was very little roll-off. Bass was solid at 30 Hz. using the Augie and filled in pretty good between Augie and 10" SSI.

BTW, this was the 10" Sterling Silver  with the Radian 475 speaker mounted on a 12x16 QSC horn/waveguide (copy of a JBL horn). I never got around to measuring the 15 SSI with the separate horn. Highs were still being adjusted by experimenting with variations on Wayne P's horn compensation guide. I actually preferred it with a bit of treble roll-off. That Radian 475 CD in the QSC horn could get VERY revealing. I didn't need it so revealing that I could tell the sax player was wearing a red shirt.  :green: What I was most impressed with was how consistent the horn was in off-axis measurements.
Great recordings sounded great, poor recordings sounded, well, lets just say it didn't encourage long term listening. That's one of the reasons I went back to single driver paper cones, The Betsy is listen-able on almost every recording, including whole sets of You Tube offerings. Soon, I'm building a baffle to house a pair of EV LS12's per baffle. 16 ohms in series and sensitivity around 98 dB. Could be a wonderful relationship coming up...

Dave :green: