Optimal listening distance for open baffle speaker

[scottjoplin]

By moving farther away you are effectively listening more on axis, have you tried toeing them in when in your original listening position?

 

[tommydoan84]

Gadut,

Thanks for joining You were my 1st inspiration going into OB project many months ago! I still remembered our conversation back then My journey was a bit bumpy at the start but I eventually have good result now. I love what I hear now and planning to further improve it.

To answer your questions. Yes. I have tried SAL in separate baffle. Directly connect different amps to it: AJ, ACA, F5, F4 with no XO , no EQ but the sound was not right for me. Overall sound was very thin. Bass was weak, high notes were peaking.

As for bass, I also adjust the Eminence beta 15 by itself in the plain baffle and semi U-frame with 4 in wings (back then I was just trying out random number for wings with no simulation theories behind). The bass by itself was also so weak and not right. I directly connected F4 with no XO, no EQ to eminence beta. Then add alot of EQ, boost to bass but the bass was still not right either. I also try Pureaudio design earlier with dipole base top and bottom and FR in the middle but cannot get decent bass out of it. I initially had plans to upgrade the driver to higher model like AE dipole or 18'', 21''. That was before. However, not until i tried out H-frame with 7.5'' for front wings and back wings together 16'' long for the distance of the wing according to MLJ quarterwave paper, then the table starts to turn around! I then realize the bass is excellent on my system even just with only 1 Eminence beta H-frame on each side.

Earlier, i think part of my failure was to trying to adjust each driver separately in the wrong direction trying to get optimum sound on each driver first with lots of EQ and Xover, then combine them together. It was a disaster for me! They don't sound right at all. Later on, i tried different approach by playing them at the same time. Only when both are playing at the same time, then my ears can detect how different and offset in the phase time alignment and amplitude. Then I adjust the output volume on each driver first for them to blend in, then XO freq and filter octave slope to find good sound. I was successful in doing that to get good sounding. Of course, other people might have different methods of looking at response curve measurement first to find peaks, dips, rolloffs, trying to add EQ, then XO but I did not find that approach attractive when I couldn't get any good result in my earlier phase. I threw everything away and use my ears to adjust sound. I was somewhat successful doing that. The sound is much much better in the past few days compared to the past few months. I think the bass is the BIG improvement when I switch to dedicated H-frame. Now I'm very happy with the bass, I don't have any needs to switch out any other higher end models. It was that good!

As I mentioned earlier, the sound was good and all but not until I discovered by accident that moving further away makes all the difference! like day and night. You should really give this a try on your system too Gadut. Moving the speaker away from the wall is okay but I don't hear much difference by what i have discovered. I still can't explain why yet until I made some in-room measurements with REW/UMIK as others have suggested but I love what I hear now. Even my wife that does not have a clue about hi-fi music loves it and told me whatever I did make a HUGE differences from what she heard in the past.

Super tweeter is something that I want to try next since I think the high notes can be improved further in my system. Do you have any recommendations for the super-tweeter drivers? I know you tried a few so you might be abel to give me some advices on this end. I love, love, love the lower end spectrum of my current OB now. The bass and soundstage is something I never experienced before with enclosed speaker. I'm sure there will be much better and more expensive choices out there for bass driver but i really have no desire to make any updates from what I heard with my H-frame and the placement that I just discover for my listening position.

-Tom

Tom,

have you tried without any xo for SAL driver? attached it directly to AJ, then you can fine tune beta 15 to get a nice blend in midbass area. better using plain baffle for SAL and beta 15

I wont expect beta 15 can produce any good low bass, you should get a real subwoofer 18" above with strong motor (high BL) and not too heavy cone, this is mostly found in pro audio subwoofer. then put it in H-frame.

until you try supertweeter, you will not know what have been missing from fullrange driver

 

[tommydoan84]

By moving farther away you are effectively listening more on axis, have you tried toeing them in when in your original listening position?

This is a great suggestion scott, I will give it a try. Earlier, I tilted back 5 degree but does not make much difference from my original listening position, i will tilt it back further at higher angle to see if I can replicate what I heard by moving 20ft further away.

Tom, Here are a few ideas for a baffle shape that may help you get pass the usual slab of wood that masquerades as a baffle.
OB gets you out of the same old box sold to us in the shops, into something that allows for artistic creativity in DIY, even though the same laws in physics still apply.
A good OB design simply leaves people somewhat amazed at what they are hearing when they reflect on what they have heard in the past.
I'll get off my soap box now, but here is a goodie in the link below.

Thank you for the link Tweet and some kind suggestions that you had provided. NaO design is similar to Linkwitz Orion OB model. It's worth a try though now that I'm at this stage.

I'm sure OB have their peculiarities, but mostly I think you just discovered the dominant factor that is the room itself and room vs speaker position vs listener position. Many angles to consider there, but since you have a dedicated room that you can move around in, try this first for fun: Stereo Speaker Placement for Optimum Sound - ecoustics.com

Thanks for the feedback. I've seen this page before and did try one or 2 of their models with my 3-way floor standing closed box speakers. I heard a tad improvement but not as significant as with OB. I think their algorithm only works with closed box speakers. I could give them a try with OB and see if it makes any difference. Thanks again for the pointers!

 

[scottjoplin]

That's not what I meant, I mean pointing them more towards you on the horizontal axis

 

[gadut]

Tom, it's great that you finally settle into OB on my 10x16ft room where my audio on wide side, my listening position is only 8ft but I dont find much different when i move forward or backward. That' s what i like about OB, no need for a sweetspot.

I never expect any 6" - 8" fullrange to make any decent bass, or sparkling/air high treble. What i pursue is the naturality of the main area for human voice and avoid any xo on that range. Hence FR should be supported by Subwoofer & Supertweeter.

Fostex T90a is a good candidate for supertweeter, I still dont find any challenger on the same price and same quality.

If you want to explore more, look at lowther america baffle design which suited 12" and 15" woofer. use the design as your guideline and suite your driver size.

TAOB - Tiny Alnico Open Baffle (Lowther America)

This will be my next experiment, i'll build 2 baffle model and try different woofer. currently I have 15" Altec 416a and 12" Fane 12-200lt, on my watchlist is to buy Eminence beta 15a and Celestion G12M (tone tubby is too expensive for me to be imported). Then my current 21" will be on H-frame

I dont suggest you buy AE dipole, but pro subwoofer like Beyma or Eminence Kappa. I'm pretty sure that you will drop your jaw when you hear real deep bass from 21" OB and powered with pro amplifier which I use behringer nu3000dsp. My senior speaker builder, he has build hundreds of boxed subwoofer for his client and he mention to me that my 21" OB subwoofer produce the best bass he never heard, and it is something that he never could achieve with boxed sub.

btw, I'm preparing to build my backyard 16x20ft as my audio video room. I'll be using 8pcs of this 21" driver as my iB subwoofer. it has 2x of my existing 21" Xmax with only 5Hz higher Fs, it should be fine.

21″ PA 127212 SW FAB BY ACR | ACR Speaker

what i mean is I dont believe your satisfaction now for only 1 pair beta 15a, reallly???? you are still far away from real bass bro

 

[tommydoan84]

That's not what I meant, I mean pointing them more towards you on the horizontal axis

Thanks Scott, will give that a try! It's best if I don't have to move too far away for optimal sound

Gadut,
Ahh, it's a gateway drug for this hobby man! You just open up another can of worms for me right when I think I'm satisfied with what my system But it's good though. That's part of the fun if it really gives me good sounding result. I was almost giving up on OB a couple weeks ago after many attempts.

Fostex T90a will be on my shopping list.
Are you referring to BEYMA 21SW1600ND or KAPPA PRO-18LF-8 ? Both their BL, Xmax looks better than Beta 15 however their Qts is quite low only about 0.33. Are they good for H-frame OB ?
BEYMA 21SW1600ND spec looks really good with xmax at 15mm but they are extinct for now. There's another alternative BEYMA 21PW1400Fe. Spec is a bit lower than 21SW but still good. The price point is quite high for this Sub. At 1k price point for a pair, i need to do a few thinking!

what i mean is I dont believe your satisfaction now for only 1 pair beta 15a, reallly???? you are still far away from real bass bro

I hope you're right bro! I really like what I heard and happy with just 1 pair of beta. It's that good. But maybe, like you said, i'm not their yet for "REAL" BASS. I'm not really into chest bumping bass as in DJ or disco/night club though. I'm looking for the natural bass with just the right amount of bunch and I think I got it with what I have. Maybe, part of that effect is due to the FW F4 current amp that I'm using, it's able to keep up with fast bass response of every notes. I bought 2 pairs of 15'' beta. I'm thinking what can I do with the other pair to add more bass to the single Hframe on each side of the speaker.

Thanks,
Tom

Fostex T90a is a good candidate for supertweeter, I still dont find any challenger on the same price and same quality.

If you want to explore more, look at lowther america baffle design which suited 12" and 15" woofer. use the design as your guideline and suite your driver size.

TAOB - Tiny Alnico Open Baffle (Lowther America)

This will be my next experiment, i'll build 2 baffle model and try different woofer. currently I have 15" Altec 416a and 12" Fane 12-200lt, on my watchlist is to buy Eminence beta 15a and Celestion G12M (tone tubby is too expensive for me to be imported). Then my current 21" will be on H-frame

I dont suggest you buy AE dipole, but pro subwoofer like Beyma or Eminence Kappa. I'm pretty sure that you will drop your jaw when you hear real deep bass from 21" OB and powered with pro amplifier which I use behringer nu3000dsp. My senior speaker builder, he has build hundreds of boxed subwoofer for his client and he mention to me that my 21" OB subwoofer produce the best bass he never heard, and it is something that he never could achieve with boxed sub.

btw, I'm preparing to build my backyard 16x20ft as my audio video room. I'll be using 8pcs of this 21" driver as my iB subwoofer. it has 2x of my existing 21" Xmax with only 5Hz higher Fs, it should be fine.

21″ PA 127212 SW FAB BY ACR | ACR Speaker

what i mean is I dont believe your satisfaction now for only 1 pair beta 15a, reallly???? you are still far away from real bass bro

 

[CharlieLaub]

This is only my personal take. Please only take it with a pinch of salt and please don't feel offended Charlie I personally think music has a much higher sense than just number, data theory, simulation, and science according to my own experiences. We're talking about physical sound wave, air moving energy, and human mind psychological interaction here. I know some system has perfect response curve, distortion number and sounds mediocre where as some system has ugly measurement but does sound really good! That's the reason why some people are drawn to tube sound even though their measurement are way off chart for a reference "good sounding" system. I know it does not make sense with engineering but sometimes "good" is "good" and it's beyond words to describe. It's somewhat like religious enlightenment. All religions have the same universal language, once a soul is awakened, you are simply awaked. Plain and simple. You'll see through everything as they way it happens no more no less but there's no science, data, plots to prove that you are really awaked only you who can see and know. It's like life is nothing but a dream and you are suddenly awake from that dream and free from all the suffering, pain and sorrow, etc. Okay enough with this I can go on and on about this topic. It used to be part of my hobbies in the past!

If the listening experience is that subjective to you, I cannot help you. You will need to find your own way to whatever particular audio nirvana that you find pleasing.

 

[tommydoan84]

Not a problem. No offense taken. Thanks for the feedbacks anyway Charlie!

If the listening experience is that subjective to you, I cannot help you. You will need to find your own way to whatever particular audio nirvana that you find pleasing.

 

[luxwinter]

Gadut,
Super tweeter is something that I want to try next since I think the high notes can be improved further in my system. Do you have any recommendations for the super-tweeter drivers?
-Tom

I should chime in at this point. I just bought a pair of the SAL drivers myself from bvtrinh. I actually haven't got them hooked up yet, so I'm reading this with a lot of interest. The seller told me that he thought that the SALs outperformed a pair of field coils he had when both were compared without a tweeter. However, he thought the SAL drivers did not integrate as well with a tweeter as his other drivers - perhaps due to comb filtering - so he decided to pass them on.

 

[tommydoan84]

Thanks for chiming in. I think i'm gonna try out the Fostex t90a super tweeter anyway to see if it will improve the highs a bit further. I'm happy with the higher note from SAL but there a few notes still sound like they are trying hard. Btw, if you're using miniDSP active Xover or any active Xover, you need to turn down the output volume of SAL for it to blend in with the sub. Originally, i didn't know this and I got bad sound from SAL when it goes to higher notes. I have to use almost -13dB down on the driver for them to blend in nicely from mid to high freq spectrum. Still, i think super tweeter can be a great supporter for SAL on the high notes.

-Tom

I should chime in at this point. I just bought a pair of the SAL drivers myself from bvtrinh. I actually haven't got them hooked up yet, so I'm reading this with a lot of interest. The seller told me that he thought that the SALs outperformed a pair of field coils he had when both were compared without a tweeter. However, he thought the SAL drivers did not integrate as well with a tweeter as his other drivers - perhaps due to comb filtering - so he decided to pass them on.

 

[scottjoplin]

I don't see how comb filtering would vary much between different speakers, it's a result of interference dependent upon wavelength and differing distance. At such high frequencies the slightest head movement will change the filtering and it will also be different at each ear. In practice it's unlikely to be audible.

 

[luxwinter]

Not sure either. I hope I didn't misrepresent what he said!

I don't see how comb filtering would vary much between different speakers, it's a result of interference dependent upon wavelength and differing distance. At such high frequencies the slightest head movement will change the filtering and it will also be different at each ear. In practice it's unlikely to be audible.

 

[gadut]

Tom...

it's not chest thumping bass that you are looking for, but deep low bass that punch and press your ear drum and even it does not have much impact on your chest bone at all. Think of thunder rumble, or huge Chinese drum with 5ft diameter

OB subwoofer is not common or maybe not exist in market, unless you DIY it. usually concert subwoofer use multiple 18" woofer to shake the big hall. However in my exploration, if go closer to box then you can rarely hear decent bass, It just like float in the air. You have to go further to get the bass, sometimes in some position there is no bass at all, which i think it already activate room mode.

different with my 21" OB, it can give you the bass equally in almost all position, eventhough on the corner it's stronger but you dont get any blank bass spot.

i paid around $200 for my 21",its cheap because made locally by the same company who produce SBAcoustic driver but this is pro-driver subproduct. Paying $500 each is ridiculous for me, but sometimes reading T/S parameter will be difficult to choose.

Previously i visited Sinar Baja showroom and test almost all available drivers, I stand and hold the driver with my hand and listen to bass that each driver produce. When free air bass is good, I was sure on the baffle it will be better. the good thing was that they profide pro amplifier with mixer, and talking to guy there for 3hr is like a huge asset for me because he knows the product, give advise and never get bothered with my so many questions. It's not something you can get from the retail store.

it seems no any 21" below $300 out there, you are not lucky. but maybe Eminence DEFINIMAX 4018LF is a good candidate with decent specs and decent price.

regarding Qts value, indeed for a starter like me and you, when you google about OB then first you will get a top paper from MJK. Then later for upgrade you will think of AE dipole but if you look at proven design of OB speaker, I can only recommend 2 designs : LX521 or Nao Note. both use low qts and decent specs with proper Eq. but building this proven design is not my choice, where is the fun of exploration? testing-failure-dissapointed then find AHA moment. beside it's also expensive.

or you can look at this guy journey on his OB and then you can decide for yourself. drop him email or maybe you can visit him and ask why he left his 18" AE dipole and choose pro audio driver.

Trans-Fi Audio - OB Speakers

my suggestion for Fullrange driver - i quote it from Lampizator Practical tips loudspeaker DIY - if you dont like it raw unfiltered sound, then leave it and find another one. Eq, passive xo to tune it will only lead you to another headache. my current fullrange is audionirvana classic 8" and i'm satisfied now. my previous fullrange include : Alpair10p and local made 8" FR, also listened to my friend fostex various series and none catch my ear.

~cheers~

 

[Tweet]

Tom, in regard to low frequency drivers for OB in particular is cone surface area ( sd ), a more important asset for driver output than is Xmax. For a given driver its Xmax is used up at 8 times its initial displacement for every octave below that initial frequency of displacement. Simply put, if a cone is being displaced by 1mm peak at 100c/s, at 50c/s its displacement will be 8 mm. At 25c/s its displacement will be 64 mm, of course at this stage it would have well truly bottomed out. So it is necessary to curtail very low frequencies just below resonance or even above if necessary to prevent woofer damage. Typical woofers very quickly run out of Xmax. so the use of a tuneable subsonic filter working around the woofers resonance will be necessary if you going to play at reasonable volume.
Of course the other alternative is to have many series/paralleled woofers working together to increase the overall cone surface area of the system's woofer, this effectively reduces the required Xmax demanded of each driver to reproduce the next lower octave at the same SPL of the octave above.
A series/parallel combination of drivers splits up the amplifier's drive current amongst themselves in accord with their individual impedance's, thus each driver in the combination is less driven in displacement as would be the case of a single driver.
Acoustic loading is very important at these low frequencies, particularly with OB design. Driver overload in cone displacement is a real present danger, something to keep in mind when you are designing your system. A dedicated, powered subwoofer for those very low frequencies is always the better option in practice.

C.M

 

[tommydoan84]

Thank you Tweet for the very informative piece of information for my learning curve!

Gadut,

You are speaking straight out from my mind in your previous post! you touched many points that I was trying and currently doing! I like your post since it speaks out directly from someone that was on the ground doing the actual work and getting his hands/feet wet not all the mumbo jumbo simulations/theories. This is also my approach too. Whatever theories, approaches out there if it cannot bring good sound, that's a dead end road. Plain and simple. Curves, calculation, numbers, simulations can pain the beautiful canvas but your ears never lie. Bad sound is bad sound and good sound is good sound. I only fall back to theories/simulation when I need to verify what I experience real life. It might be a good starting point but never be the definite answer to my hi-fi quest. I learned it the hard way.

You were completely right on point about the bass.

in my exploration, if go closer to box then you can rarely hear decent bass, It just like float in the air. You have to go further to get the bass, sometimes in some position there is no bass at all, which i think it already activate room mode.

I was completely blown away when I moved away 20 ft from the speakers then I realized how good the bass sound! sitting 8-10ft away from the speakers the sound is okay , bass is there but not impressed me at all. After changing my sitting position(20ft), the sound is so open up, 3D, the bass is something that I never experience before. Period! That's why I was telling you that I'm satisfied with what I just discovered. I'm not easily pleased. I have my own taste and hearing in music and it's picky. I used to play instruments in a band back in college. My ears can differentiate different musical notes in any particular scales. I auditioned many hi-end system before. Some sound decent, good but not quite impressed me like what I had a couple nights ago. Funny thing is I tried to move the H-frame bass forward a few more feet away from the wall, that 3D deep bass has lost. It needs to be 4 ft away from the wall and I need to sit 20 ft away from it to really experience "real" bass on top of that SAL FR speakers also open up and sounds good in harmonize with the bass to produce some "real" experiences. My wife and I just auditioned a drum test play tonight on this system sitting 20ft away and man it sounds good! feel like we're in a Blue man band concert hall. We went to their concert a few months ago in Las Vegas and experienced real drum sounds and this OB speakers playing with FW F4 + AJ brings a very closed real live experiences to both of us!

Thanks for all the good inputs and info, Gadut. I'll keep my eyes and ears out for the good 21'' bass when it comes along. Btw, I just placed an order for a pair of Fostex t90a and 2 Lpad to adjust the volume.

Last, I also like what you wrote

if you dont like it raw unfiltered sound, then leave it and find another one. Eq, passive xo to tune it will only lead you to another headache. my current fullrange is audionirvana classic 8" and i'm satisfied now. my previous fullrange include : Alpair10p and local made 8" FR, also listened to my friend fostex various series and none catch my ear.

This is also my philosophy. Right now both drivers sound really good with what I had discovered with the right amount of volume and Xover point. I do not use any EQ to either bass or FR. They are good as the way the are right now and I like it that way.

Best regards,
Tom

 

[scottjoplin]

The bass changes you describe are due to room modes, worth investigating, if you listen to different frequency test tones you can often find a compromise position although it's likely you will be still left with a large resonant peak.

This thread is also worth looking at if you haven't seen it already Fast, fun, Inexpensive OB project

 

[gadut]

I agree with Scott, with your 20ft listening position it's already like the bass have been reinforced by your like pipe room. that is why i previously stated that you should focus on near field bass quality and quantity, when it's weak it means you have weak driver no wonder moving back gives you more bass experience.

btw, I'm glad on my first gut gamble on using big driver, less trouble until now, hence I mostly spend my time to find out what matter most : Fullrange

anyway, have you tried to put extra bass boost and listen in nearfield? not sure safe area for beta 15a xmax which is only 4mm, previously I also tried 2x15" pro driver with Qts 0.7 and no possible way i could listen without any bass boost around 12dB @30Hz.

 

[wesayso]

Not a problem. No offense taken. Thanks for the feedbacks anyway Charlie!

In my humble opinion you (the OP) are missing out on a valuable lesson from Charlie, which quite possibly would have lead you to the magic without the current luck factor involved.

Shooting in the dark may be a fun game, but remember, the real magic is in the music.

 

[mkane77g]

 

[tommydoan84]

Thanks for the inputs Gadut and Scott. That explains it. No wonder why even when I change position of FR panels to point toward my listening position 1 to be more on axis. I think the FR sound improves but I cannot get "good" bass as I'm moving away 20 ft.

At this junction, i'm thinking whether I should put time/effort/money to investigate and upgrade the gears for the right bass or just be happy as the way they are right now with my room mode and move away 20ft just to enjoy the music for the heck of it. I know the issue is still there, it's definitely fun and worth investigating for my learning curve in speaker design but is it really worth it if it involves in alot of extra cash for extra measurement tools/softwares, upgraded gears for what I have already discovered.