Experimenting With Open Baffle Subwoofers - Unexpected Results
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- เผยแพร่เมื่อ 21 ต.ค. 2021
- A bit more detail:
I tried that first dual woofer sub in three different locations at the front of the room, and saw very little difference in the measured output. But that first measurement and the fullness of the bass produced encouraged me to keep going.
In all instances I had to have the tone control on the Yamaha receiver set to boost the bass. While I could do that in Equalizer APO, that generally means cutting higher frequencies to get enough boost in the bass region. The bass control on the Yamaha seems to be doing a very accurate and natural sounding lift.
Without the bass boost there wouldn't be enough bass output from the 2 woofer setup.
The 4 woofer dual subs that I settled on can be improved by adding a lowpass to 2 of the woofers and using those exclusively in the very low bass range (40Hz and down), while the other two operate up to 80Hz. This should extend the bass output even lower, but does complicate things.
You'll often hear that open baffle speakers don't excite room modes, but I saw no evidence of that. The one distinct advantage I saw was that they are easier to place in the room - boxed subs will perform much differently in different parts of the room, while these work the same (more or less) wherever you put them (within reason - they do need to be away from the walls by a certain amount).
As for the quality of the bass, I couldn't hear any difference other than the struggling problems of the woofers pushing their excursion limits. Keep in mind that this is crossed over at around 80Hz.
My isobaric sub was putting out solid, effortless base that sounded accurate and extended down to 20Hz. These are the same except for the depth of the low end, but sound identical to the isobaric sub. My room is 14' x 14' and is well treated acoustically, and these subs easily provide enough thunderous bass for modern movie soundtracks.
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A bit more detail:
I tried that first dual woofer sub in three different locations at the front of the room, and saw very little difference in the measured output. But that first measurement and the fullness of the bass produced encouraged me to keep going.
In all instances I had to have the tone control on the Yamaha receiver set to boost the bass. While I could do that in Equalizer APO, that generally means cutting higher frequencies to get enough boost in the bass region. The bass control on the Yamaha seems to be doing a very accurate and natural sounding lift.
Without the bass boost there wouldn't be enough bass output from the 2 woofer setup.
The 4 woofer dual subs that I settled on can be improved by adding a lowpass to 2 of the woofers and using those exclusively in the very low bass range (40Hz and down), while the other two operate up to 80Hz. This should extend the bass output even lower, but does complicate things.
You'll often hear that open baffle speakers don't excite room modes, but I saw no evidence of that. The one distinct advantage I saw was that they are easier to place in the room - boxed subs will perform much differently in different parts of the room, while these work the same (more or less) wherever you put them (within reason - they do need to be away from the walls by a certain amount).
As for the quality of the bass, I couldn't hear any difference other than the struggling problems of the woofers pushing their excursion limits. Keep in mind that this is crossed over at around 80Hz.
My isobaric sub was putting out solid, effortless base that sounded accurate and extended down to 20Hz. These are the same except for the depth of the low end, but sound identical to the isobaric sub. My room is 14' x 14' and is well treated acoustically, and these subs easily provide enough thunderous bass for modern movie soundtracks.
Seems to me you need some FI AUDIO IB 15’s or 18’s in your life. They’re reasonably priced and have some real excursion..
A really good FX soundtrack for low bass extension is "War Of The Worlds" is got some wall shaking bass. BTW, is open baffle different from infinite baffle? I'm suspecting they are. Infinite baffle requires the front and back of driver to be sealed from each other right. I don't recall ever seeing/hearing a open baffle before.
@@harryberry474 The "church scene"...yeah just watch all the new Godzilla movies if you want the reall low lows...or the intro to edge of tomorrow...
Very interesting. Yes, I have used isobaric subs and liked the quality and quantity of bass. I currently have my subs as explained previously, roughly at third points horizontally and half way up the head wall of the room. This location definitely seems to produce less reflections by both subs coupling and creating a wave front starting from that wall and moving back through the room. My room is 13'x20'x8' tall. Notice the proportions. They are the golden mean. So the standing waves in any direction are never replicated in the other directions. That may be why the positioning of your subs do not make much difference at 14x14. Not sure of the height.
Why not try an IB (infinite baffle) instead? I mean a system where there is no path between the front and back of the speaker. Of course you can make a box do this effective (as long as the box is large enough that it doesn't materially impact the speaker's resonance.
I like that you mentioned how it sounded the same. Too many people get caught up in the numbers and forget that in the end, how it actually sounds is all that matters.
At the other end are the guys that think that the numbers can't tell you anything and that all they need to do is listen, and from my observations that's the bigger group.
On the whole, running the measurements has pointed me in the right direction and vastly improved my listening experience since I started building the room.
It's the numbers that dictate how it sounds ...
Oh yes , the measurements saves you months of trial and error
And to think I wasted all that time listening to speakers in various heights, different distances from the wall etc., until they sounded best; Do I feel foolish.
Glad you created this channel! I love your other channels also! Always interesting!
When I hear open baffle speakers all I think of is weak low frequency bass since I have played Bass Guitar since I was 10 years old and am now 70. The old Floor Model radios almost all had open baffle 12 inch speakers being driven by maybe 15 to 30 watts and their bass was very weak even if I equalized them for extended low frequency response. I played on some older Bass Guitar Amplifiers that came from the factory with open baffle speaker cabinets since they were originally designed for regular guitars, not Bass Guitars and the low end was very lacking. I obtained a closed baffle cabinet for one of my 20 watt bass amps and found the difference was very great and it even sounded good with regular guitars. Note the speaker in the cabinet was the same model as the speaker that was used in the open baffle Guitar cabinet so the speaker was not the weak part, it was indeed the need to cancel the out of phase audio signal from the back of the cabinet. If the back of the cabinet was removed the bass response went way down as to not be useable for my Bass Guitar playing in the Jazz Band I was in. If people like weak bass, which I know many do, then open Baffle may be the way to go for them. The sound of an open baffle with bass being played through it mostly reminds me of the Orchestral Upright Bass that I used to play and it is ok for that type of bass reproduction but not for Bass Heavy modern music. Just so people understand, I am a retired Electronics Engineer so I have done the work. Lol
This subject always seems to make me fire up my system and give it a listen. It's not perfect, but it is good. It had been so long since I had listened to any Grand Funk Railroad. I loaded Rock and Roll Soul and I suddenly remembered just how good these guys were. Such a tight group of serious professionals.
Of course, now I need to listen to some 2112.
Man, your videos make me wish I can rebuild my speaker cabinets that I designed back in high school. There were some mistakes I made back then that I would like a second chance. One of the main things is in my design I had a Sub built into each cabinet it self and powered separately from the 3 way config. Also, I didn't have the money (being 16 years old) to afford 2X12" woofers and 2x12" subwoofers. But now being old and slightly wiser I'm not sure it would work with only 2 cubic foot of air space.
Side Note: When I built these back in '92 I made them out of 3/4" Birch Ply and everybody including my shop teacher thought I was crazy for using that wood. Now a days it looks like a lot of people are using Birch Ply or Baltic Birch Ply. Looks like I was on to something back then. Also, when they were finished and had the people that thought I was crazy have a listen, they all had the same surprised look on their face. They did end up sounding really good even with crappy Radio Shack speakers and the infamous Realistic 12" subwoofer 😀
Happy to see you experimenting with open baffle. Food for thought: a "w" frame arrangement may also be a good option, as it would cut down on the subs' physical presence and may yield similar results. There's a lot of options out there for tweaking open baffles.
Thats cool! Way to be open minded. My speaker needs to be enclosed bias would have never let me try an open baffle lol
Very interesting. I have been wanting to try open baffle in general so thank you
I made my first set 2 years ago as a Covid project. I had a set 3 way diy speakers with Philips drivers that I bought from a thrift store. They sounded crappy, no dynamic and totally filled up with damping stuff. I took them apart and placed all drivers in a piece of 18 mm thick plywood. Used the cross over as it was(a huge diy thing). The result blew my mind! Very open sound and a musical bass from a 7" woofer. Jazz sounds amazing. At the moment I've made two sets, one a 12" full range Philips driver with added tweeter. Second one is a 3 way using a 6" 10 watt full range as tweeter, 2 x 7" 6,3 watt full range in series as mid range and a 7" 20 watt woofer. Cross over as above from the crappy speaker set. Sounds great! Go try!!!! It' s a lot of fun.
I'm so happy to see that You're also considering the Plan Baffle which is part of my religion ! To make simple: Y've been teached that Close to the source, the sound is spreading like a variable pressure with air deplacement. Further in space, the sound moves like a wave, with pressure instant variation. It's like the microphone that is relying to air speed or air pressure, depending on the system. And our ears work the same way, as we also know how to recognize the distance of alarm signals in life ... This concept maybe explains some of Your conclusions.
Personnally, I adore the Plan Baffle for it's Dipole behaviour, leaving energy sensations to a complementary sealed box .
Just keep producing your ideas on video and thank you for sharing. Until your next informative video, love and a warm handshake from my humble country 💝 the Philippines 🌺💮!!!
Just curious if you ever build the "nicer" version of these? Great info in the video regardless. I am considering OB design for subs I plan to use with my desktop computer speakers (which are also OB) and this is one of the first videos that came up searching for OB sub builds.
Hi John, I have been impressed with your woodworking and hi fi videos. Would you please share your background in audio?
I am guessing you have worked in the field. I appreciate the knowledge you share. I apologize if you have answered this question before. Thanks
I’ve always been curious about that Swarm subwoofer system by AudioKinesis
The minimalist approach looks promising. Brings back memories of a lot of musical instrument amps that ran open back.
Now for the other extreme, you can build a folded horn design to test, next.
Place isn't big enough for horns, or I'd be all over them.
I'm going to keep this simple- awesome shirt!
Great problem to have. Sounds like fun, especially when you get desired results. Have you considered rotating the 2 woofer baffle so that both speakers are close to the floor?
Thanks, for me the best diy and audio channel, really information that is not bs but the facts. I worked diy both isobaric and OB sub and these facts hold true, with OB there is a steep drop from 50hz with near field measurements so the use of OB sub is really questionable, on the other hand the sound was correct and less disturbing than with isobaric.
My little experience with open baffle speakrrs is that they are very sensitive to cancelations and room location.
I see GR research open baffle subs the divers are facing opposite one forward and one rear probably out of phase .
The wings can have effect as well make foam wings and try different sizes and angles
Sir u ve got the skills plus the tools......check some of danny richie s open baffle designs. He uses one wing - flang per speaker at 110 degrees to separate open baffle cancelations. I belive u will find his designs interesting. Cross overs is a big issue for a flat frequency responce. We are waiting anxiously
Great video and awesome shirt.
Please try using a very large open baffle, eg 8 to 20x the surface area of your subwoofer. If you hang it in such a way (for hinge effect with ropes) that the apparatus resonates just below your cutoff frequency, you may find lower frequency response, as the baffle transitions into transducer effect. I had great success mounting a 52" display on top of a high fidelity, sealed enclosure, forward facing subwoofer, driven with lots of power and eq from the center channel source. Clearly the display was somehow enhancing the very low frequencies.
I have been told to keep open baffle subs at least 36" away from the wall. In my room I have found that my open baffle speakers are much better suited for music than theatre. You are more than welcome to borrow my Rythmik amps and GR subs so that you can use the options that the amps offer for delay, cross over, etc. Or you can use the amps to drive your drivers to see if the adjustments actually help in your situation. I cannot use them for a while and would drop them off it that helps. Paul
Thanks for the offer, Paul :)
I don't think there a specific minimum distance they must be from the wall, but of course if they are too close it will basically box them in if they have wings like these do. And very little of the music I listen to has the kind of deep base that movie soundtracks have, and it handled both quite well. Of course these are four 12" woofer with pretty high excursion, so they are moving a lot of air.
What is your “go to” recording? I like Yello’s “Of course I’m Lying.”-
I think you’re doing a great job!
Would love to see a decay response between the two as that should theoretically be one of the advantages of the open baffle, though in the sub area I'm not sure if it appears. The favorite pair speakers I've designed have been a pair with a cardioid radiation pattern, less interference from room boundaries, but these though tower speakers only went down to 60hz, were passive.
Looking forward to the rest of your build!
I love OB bass. I use a 21" OB and the directivity down low is great. Makes everything sound more real
My understanding is that you need an anechoic chamber to do that for bass frequencies. With higher frequencies you can record a time gated response that is shorter than the time it takes for the first reflection to hit the mic. But with the lower freqs. The wavelengths are longer than the reflection distance, so anechoic is needed.
I assume the frequency response curves shown include the mid and high speakers as well. The bass only I would expect to roll off 600/800hz or less.
Open baffles/dipoles need between 2 and 3 meters distance from backside to wall for maximum efficiency. Q-values must bei higher than 0.7. W-shaped Ridthaler type dipoles reach \-6dB@16Hz but need frequency response correction via FIR DSPs. My favorites are open baffles with wide range drivers (e.g. Tangband W3-871SC) for mid- and high frequency range and Ridthaler type dipoles for base. I use Crown XLS power-amps (much faster than e.g. Monacor STA-X00D) to drive the Ridthaler- dipoles.
Hahaha.....I dig your TH-cam channels and your shirt. 👍
I could be wrong, but I think the challenge for some tastes is getting the frequency low enough. You can tune a box, but you can't exactly tune a speaker lower than it's rf. But, you can find them. Problem is they're pretty expensive. And heavy.
Nice shirt. You have to make sure the qts measurements are correct if you use an open baffle to work correctly there's drivers made for ports , closed design and open baffle and you find what works for your design from the qts measurements or it's not going to work the way you want it to.
Hi
Can you give some recommendations for drivers of OB subs. Preferable available in EU.
Awesome shirt!
Hey John. Great video!
I'm curious on the QTS value of these drivers. That's an important consideration when building OB subs. The higher the QTS the lower it can play.
This also makes me want to grab 4 18' with a high-ish QTS, and corner load them in my room for some easy bass.
Also, I was curious if you would not mind looking at impulse response , group delay etc when comparing OB to ISO? That would be a pretty neat talking point, though I don't think those necessarily matter in lower bass.
These woofers are 0.5 Qts.
Virtually no difference in the impulse response between the iso sub and these, but I was measuring the everything together, and not just the subs.
@@IBuildIt Right on.
I'm curious how an H frame open baffle woofer would look measured. Less cancellation around the sides. You interested in trying something like that? Do some H frame OB, vs Flat OB, vs ISO?
pretty low Q for an OB system. It is very difficult to find drivers really appropriate for OB below 30 or 40 Hz. IB or sealed is much easier to find drivers for that can get that last 8va from 32Hz to 16Hz.
Love your shirt.
I don't know how true it is as I am not an expert. But I remember reading reviews while shopping around for speaker drivers and some of the models I looked at people said they were good for open-baffle use because they had a very high sensitivity rating on them versus the "standard" speaker driver. So from what I'm getting out of it pretty much any full-range speaker driver with a sensitivity rating of 100+ db. Again, just something I've read from other builders experiences who deciding to leave reviews. So I don't know if it's true. :)
have you thought of trying an isobaric pair mounted in an open baffle?
Very interesting John. You may have mentioned it before but what drivers are they? I'd be interested in looking at the specs. Many thanks.
The drivers are 12" custom made by Eminence. T/S specs:
Fs - 27.9
Re - 7.4
Qms - 8.9
Qes - .5
SD - 510cm^2
Vas - 126 L
Xmas (peak) - 9.8mm
@@IBuildIt Thanks John. Specs aren't everything but those are good specs! One good thing about open baffle designs is the Qt doesn't change as it does in a box.
What about selling the rear sound wave totally from the front?
Like speakers in the rear deck of a car.
I've enjoyed your speaker-building videos. Hopefully they will get more people interested in the hobby.
OTOH, I've always though that open baffle subs were a really bad idea. At the one extreme, a sub with no baffle simply pushes air around the edge of the frame and the compression/rarefaction waves cancel right at the edge. Add a baffle and more energy gets directed forwards/backwards at higher frequencies.
But at sub-woofer frequencies, say 40Hz, the wavelengths are so long that the baffle would (in theory and if my math is correct) have to be around 15' wide to effectively separate the front/back waves. Double that for 20Hz response.
Add the loss of cone excursion control and I don't see any advantage to open baffle sub design. For those reasons, I've never tried it so I could be wrong.
Maybe try measuring or listening very close to the baffle edge and only a few inches further away. If the difference is substantial, that's wasted acoustic energy.
Anyway, thanks for sharing your interesting projects.
The response down to 30Hz is easy to see in the measurements posted in the video, and I also show the effect of reducing the width of the baffle on the low end output. The original baffle width is a total of 40" with the wings, and 34" after I cut the baffle narrower.
And then there's my under-oath testimony that I didn't detect any reduction in the amount of low bass when compared to the very capable isobaric sub I had in the room. These are in-room measurements, though, and not the actual output from the subs in an anechoic chamber.
So I'd like to know where you are getting your OTOH from? Isn't the evidence I've presented here compelling enough?
@@IBuildIt Well, let me back up. If your goal was to experiment with an open baffle design and see if you could get a reasonable LF response curve, then well done. I think that it's great to test various designs and see what happens. I'm all for that. (I've tossed many more failed box prototypes than I've actually committed to final builds.)
I was simply sharing why I think that the two approaches are not equally "good" sub-woofer designs by any other measure -- efficiency (SPL/watt) and cost ($/SPL) to name just two.
So if you were a hobbyist without extra power amplifiers and EQ equipment and had to pick, which would you spend limited funds on?
Thanks again for investigating and sharing your experiences.
You definitely want Qts well over 0.7. over 1 preferably. H, W, and N frames make for some useful variations.
One of the benefits of my duel open baffle subs is I get a more accurate sounding bass (with music anyway) that seems to be directed towards my listening position, and less of the window and wall rattle that I was getting with my single ported 12" box sub. My girlfriend says she can't here the bass at the other end of the house as much as se did before, yet I hear and feel the bass really well in my listening room (yes, I did have to bump up the bass on my amp with the OB setup). It's a win win in my book
have you ever made? a U Frame dipole? i am thinking of making one with the new F 15 made from Butcher block wheelchair larry
They say that OB load the room less than ordernary speakers.
The frequency graph do not show all the interesting stuff.
I hope you have the measurements in REW. So you can look at the waterfall graph that shows how long time each frequency is bouncing around in the room.
Less bouncing less loading of the room and less treatment.
That would be interesting to see.
Great video!👍
As I said in my pinned comment, I saw no difference between the OB subs and the boxed subs as far as room modes and reverb time goes. So it's less exciting that you were lead to believe :)
But you can have a look here: th-cam.com/users/IBuildItcommunity
Did you try putting the subs into an H frame?
I thought subs were fairly non directional. You can put them almost anywhere in the room and it’s good. I’ve run sound for stage (live theater), basketball games in a small arena, small concerts, outdoor venues, and the common denominator is. Nobody notices good sound. They only notice bad sound.
I notice good sound :)
I think the problem is most people haven't actually heard good sound.
And while low bass is mostly non-directional, the placement of the subs can impact the response at the listening position.
Cool shirt😁
So besides being obnoxiously huge , poor low end frequency response , and reflection issues whats the benefit of an open baffle again ??
Open baffle bass is awesome but you really need servo control to see the real beauty of open baffle bass... U should get some gr research drivers and their servo sub for them for real mind bending bass
I agree… open baffle is an option… Pure Audio …
Open backs are nice.
Cool t-shirt.....
One 21" OB on either side should do it :D
Does the rigidity (natural frequency) of the baffle and its support matter?
Not enough to radically throw off the results from these tests.
Stiffer, stronger and denser is always better. Hard to say exactly how much better, but most guys that are serious about building their own speaker usually try to overbuild.
Interesting that the first stacked baffle didn't benefit from line array coupling to produce a higher SPL. I need to think back a little... Maybe that effect is dissipated as the frequency drops...? That would make sense... It would take longer for the coupling to occur since the wavelength is longer... I bet if you were listening across the street, you'd see the bump. LOL. Sorry for the ramble, it all makes sense now.
If anything there was some comb filtering with the big one because the woofers were so far apart, and that showed up in the measurement (that lumpiness from 30Hz to 150Hz).
Maybe try the stacked version in the corners again, except put some traps in the corners. There has got to be artifacts escaping from the hard surface and corrupting the measurements at the mic.
...or maybe defusers
The wall is a bass trap already. Watch his other videos.
2112 brother !
👍👍👍
I think it's wrong to say there's nothing to design because there's no box, OB just has a different set of design elements from box speakers.
Instead of a free standing free baffle woofer, inside the room, why not mount the woofers in the wall. It is still a free baffle but one side in one room and the side of the driver in the other side. It gets rid of front to rear cancellation and gives you full bass extension the driver can do. But the big thing will be gain of output due to loss of cancellation. If you do, a driver with a qts around .6 would work best mathematically.
Actually working on that right now :)
I was wondering when someone would mention infinite baffle and my room is nearly perfect for it, since there's a utility room behind the front wall.
I thought about doing it from the beginning, but like the open baffle, or even more so, there's not much speaker building involved. But then I can concentrate on making the main pair really nice.
@@IBuildIt yep, that's an age old idea. I have found a speaker with a qts of 0.6 is the best compromise between natural dampening and transient response. Back in the fifties guys would make one wall of their listening room a combination of infinite baffle subs and huge horn speakers. Then they would put a huge grill cloth over the whole wall so that it looked like a ""normal" room. Talk about efficiency. A three watt amp was probably all they needed.
@@IBuildIt Very good idea. OB mains and then a manifold style IB with something like 4 Dayton HF 15 subs. Should cover everything nicely. I would want the OBs covering down to 40Hz with the IB covering the last 8va and a half.
The front fascia and the wings Need to be calculated to optimize response.
Or you can just build it cheaply and test it in the room, like I did.
I would just build a front baffle and use cardboard to optimize the wings. Not in beginning. Near the end to fully optimize. Love your channel. Its a fantastic resource.
Should make them servo controlled
How much money do I need to spend on equipment that tells me that my speakers sound good?
Nothing! There are things on both sides of your head. That's what I use and thrust.
TRY ISOLATE WHIT FOOM FOR FLLOR . GOOD JOB.
Good god, your shit starts and stops on a dime!!! My room, not so much. Some day. At least I know it’s boys speakers I need to be chasing after. It’s the room.
Open baffle subwoofer requires a open baffle amp and special subwoofers. Amateur bullshit here
That was a fine laugh! Open baffle amp!! I'll have to write that one down!