[Knight Rider]

Hello!

I'm new on this forum, but I have spend lots of time by reading old threads like "Gravity well of a dark star". I have some experience about simple 2-way open baffles (MJK style), but I have never tried hinged version of only one driver (like Visaton B200).

In old threads it was stated that B200 is a pretty good driver for OB in it's prize range. How about today. Are you guys still using it and/or are there better solutions available for 1-way OB ?

[mcgsxr]

Welcome to AC!  Sounds like you found a great thread for OB exploration if you have read through the very long Gravity thread.

I used the b200 for around 8 years on OB, but only for 1 year without a helper woofer - it just cannot deliver satisfying bass in rooms larger than 10x14 in my experience, and all my basement rooms have been more 2x that size.

I have never heard them, but some folks claim the Hawthorne's can deliver on their own, though they too are most often paired up with Auggies for bass.

What size room do you have?  Amp?

[Knight Rider]

My listening room is quite small, approx. 13.8 x 10.8 x 7.9 ft. Now I have a simple plain baffles with TB W8-1808 + Fane sovereign 18-500 (18"). I have also tried Eminence alpha 15A instead of Fane, but it's not any better. I like the sound in general, but the bass quality is not as good as I could wish for. It's maybe too slow and does not have shades like the best ones.

My amplifier is Vincent sv-236 mk:
http://www.6moons.com/audioreviews/vincent2/1.html

and cd-player is Arcam cd33:
http://www.stereophile.com/cdplayers/704arcam/

Do you think it could be possible to get satisfying bass with my room/gear?

[Knight Rider]

I have some questions related to open baffle design process, could you please help me:

1) As far as I know, there is no simulation software for winged open baffle. But if I use Jeff Bagby's Diffraction and Boundary simulator worksheet to model it like plain baffle, can I get close enough?

2) Which other factors I should take into account when predicting frequency responce in listening room? In other words, is there something which I should sum into predicted diffraction+boundary responce ?

[OB_Newbie]

Hello KR,
I'm new to OB design but have had good luck and having an awesome time with the approach/open baffle design below.  If you are not happy with the bass response you are getting now, this may be an approach to consider.  It’s flexible and can tailor to your room and driver selection. 

Baffle, speakers and amplification
---------------------------------------------
*  U frame baffle : 16 X 36 with 8 inch deep wings, 24 in height.  The depth taken from Martin Kings U/H white paper and used in conjunction with the plate amps xover to achieve a higher cross over point than  plate amp alone can achieve.
* High-freq : Tang band W4-1320SJ with BSC (1.2 mH + 2.2ohm) and cheap cap/1st order to filter bass (147uF at this time).
* bass : 2 MCM 10" pro drivers used in Ed's original Hestia OB design.
* x2 : Yung SD200-6 200W Class D Subwoofer Plate Amplifier Module with 6 dB at 35 Hz.  1 amp for each channel to power the 2 MCM woofers per panel.

Basic design elements
-----------------------------
* The key to the design is the combination of a full-range driver that can play low enough to cross over to the plate amp driven dual 10’s.  The plate amp is fantastic and provides the flexibility to adjust the level, xover points and phase.  Can tailor the bass/lower mid-bass to the room.     
* I didn’t tweak the 1st order high pass on the Tang Bands much.  Testing values from 100 to 240uF.  Found early to set the high-pass and use the plate amp’s for integration. 

Listening impressions
----------------------------
Bass Response:  The bass I'm getting is clean and flat to about 30Hz.  Fast and tight.  Ed's design uses the MCM helper woofer all the way up to about 2K crossed to a 3/4" Vifa.  If it can manage mid-range duties it’s more than adequate for fast bass.  I choose not to go the MJK Alpha route because I tend to prefer mini monitors and wanted better transient response than what a single 15 inch woofer can provide.  I could not be happier with the dual MCM woofers in this design.

Upper bass to high frequencies. 
I LOVE the bamboo Tang Bands.  You have the 8 inch Tang Bands so you know how good they can be.  I am listening to the W4-1320’s now but also have the W4-1879 and W5-1880 that I will be trying soon.  I choose the smaller drivers to push beaming a little higher in frequency.  It’s the simplicity of a 2 way design that makes this design work.  Based on what I’ve learned to this point, I believe it would be possible to take any existing 2 way monitor design and throw it on the baffle and adjust the bass units to match.  In this OB design, I had to adjust the BCS so the xover design would need to be adjusted.  Modeling it in Jeff Bagby’s PCD would make it fairly easy and get pretty damn close I imagine.

Like you, I was worried about the bass response I’d get from an open baffle.  But I can confidently say that I just could NOT be happier right now and enjoying music like never before.  I’ve had WAY too many late nights because I could turn off the damn music!!!

Anyway, I hope this gives you some ideas…

Rich

[Knight Rider]

Hello all!

And thanks about your post OB_Newbie. All new ideas are always welcome

Let me tell you shortly about my DIY history:

About 5 years ago I had Dynaudio Focus 140 loudspeakers. I liked them. (Overall balance was well suited for hard rock music. I still listen to lots of rock but also jazz and many other genres). But there was a problem with room modes. Lowest mode, about 41 Hz, had a high peak and it was disturbing too much. I sold Dynaudios.

After that I heard about MJK and I decided to build TB W8-1808 + EA 15A baffles. It was a big improvement. Bass problems had gone away, midrange area was shining. They also worked pretty well with rock music, so I was happy quite a long time.

Later I needed something to do. I build Pencil 12 cabinets with Markaudio Alpair 12 elements, just to experiment something else. Thet were working very well with highest quality recordings, but if I put something ugly heavy metal it was terrible to listen. But I liked the bass quality very much. It was a little bit thin but otherwise very good. Also Pencils had to go.

After that I built MJK's H-frames with my current Fane 18" elements. It was not successful. I don't know what's the problem with H-frame construction, but it's not working at all in my room. Maybe my room is too small and/or maybe listening distance is also too small. Soundstage was way too obscure. Not good.

So nowadays I'm using plain baffles, approx. 70 x 90 cm, with TB + Fane. They are tilted backwards 5-6 degrees. This is the best solution so far.

Based on the bass quality of Alpairs and what I have heard/read about single FR drivers, I would like to experiment with a single driver. Maybe a bigger plain baffle or a winged version. Unfortunately I don't have much time for experiments, too many things to be done, so all ideas are welcome.

[Knight Rider]

Hello!

Visaton B200's are ordered. I will use 20 mm (~3/4") birch plywood (approx. 680 kg/m3) and piano hinges for the baffle. I will make it 1200 mm (47.24") high. How about the plate widths? If I can remember correctly, Dmason used 10", 12.5" and 14" plates in his famous baffles, and element height approx 30" from the floor. Is it ok?

[mcgsxr]

These were the best baffles I built for the b200, but I honestly liked them better alone on the baffles.  I found the addition of the bass driver smeared the mids, but it brought with it satisfying bass.

By memory the small wing was 6 inches, the large wing 12 inches, and the center around 15 inches wide.  That is a 12 inch woofer for reference.

I recall they were centered around 28 off the floor.

[Knight Rider]

Thanks Mark. It's difficult to choose baffle widths. I have two options:

1) center baffle 10", sides 12,5" and 14"

2) center baffle 10", sides 10" and 18,66"

Second option has more offset for the driver and it is based on to the IEC test baffle proportions. Almost same proportions have also been used in Wild burro audio baffle plan. It will give a little bit more bass boost. But could there be any disadvantage because of big difference in side plate widths? Which one would you choose?

[mcgsxr]

If it were me, I'd take the one with the more drastic size differential for the wings.  I found the different wing sizes to be effective (built on the angled top line of my baffle too).

I'd also suggest that the use of mdf is the best way to build prototype baffles cheaply.  Then you can invest in Baltic Birch or other more attractive "final" baffles.

[Knight Rider]

Visatons are playing. Good news is that there is enough bass available. Better extension than I expected. No need for extra boost. I would say promising sound straight from the box. Best imaging when wings are in approx. 45 deg. angle. But upper midrange/highs are definitely too hot. Some kind of attenuation or notch filter is needed to tame the rising response. Could you please recommend any L, R, C -values ?

[konut]

Hi KR. Have you read this thread? MOX in parallell with a 1 mH inductor for the B200

http://www.audiocircle.com/index.php?topic=31582.0

It discusses the exact subject you queried about. I have a pair of said filters made by Vinnie Rossi that are left over from when I owned the Omega Aperiodic 8s. I sold the 8s and the new owner did not want the filters. If you are interested, send me a pm and I can send you a pic and can discuss terms.

[guest42212]

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

[Knight Rider]

I did couple of measurements today. Baffles directed straight into listening position. Measurement have 1/6 octave smoothing. Raw responce will have much sharper spikes. This is quite interesting. There are not as big humps as I thought. Overall responce will raise only little bit from 2 to 10 kHz. Not bad I think. But listening impression tells me clearly that there is too much tension/attack at upper midrange area. What you think?

[mcgsxr]

Nice graph.  I never measured mine, I always tuned them by ear, I am a purely subjective guy.  I never used a circuit with them.

I'd try 2 things.

1 - change the baffles L to R, so that the smaller wing is on the inside (unless I am seeing things).
2 - toe them in so the drivers are aimed to cross slightly ahead of you - experimenting with toe in brought it all home for me.

Have fun, it is supposed to be!

Thanks for sharing your explorations with the group.

[Knight Rider]

I love these Visaton baffles. Clearly the best sound so far in my listening room.  I think that run-in period is still going on, but they have already started to shine.

I think that I have found pretty good position for the baffles. I have also been experimenting with LRC-filter (4.7 mH, 3.9 ohm, 3.3 uF). Air cored coil with 0.71 mm wire, ceramic 10w resistor and Polypropylene caps from MKP. Not yet highest quality parts, but not bad either. I can already play pretty loud with some good quality recordings. Mark Knopfler's Sailing to Philadelphia will sound truly amazing, so I think I'm not far away from optimum values.

What you think about resistors, is MOX better than ceramic one? And how about higher quality caps, can you recommend any type or manufacturer?

[kephas]

hello!

i am a novice when it comes to ob speakers. i have read martin king´s paper and some threads here etc.

besides wanting to find a way to build a good pair of ob speakers there are domestic considerations. i am therefore interested in baffle designs that can be folded and moved against the wall when not in use or when expecting guests.  i had the idea that something like the "basic betsy open baffle"
http://www.wildburroaudio.com/projects.php might be an option with an eminence alpha 15" woofer mounted in a wider side piece whereas the full range element, say visaton b200, would be mounted in the narrowest center piece.  using an active crossover at, say 100 - 200 Hz, i was thinking there might not be a problem of directionality if the woofer panel were, to keep the rig stable, not completely extended.

i hope i have not made a fool of myself and would greatly appreciate any comments.

p

[Poultrygeist]

My first OB's were the folding wing Betsy's. Enjoyed them for awhile but felt they were a little too bass shy for my tastes. Added Alphas on the long wing but they became so cumbersome I scrapped them and went with these flat baffles.

[Knight Rider]

Hello!

I have a problem with the plywood material in my OB's. Plates are not straight anymore. They have twisted significantly. It can be clearly seen by the eye. To solve this problem I have been thinking to add support plates to the bottom and top. It could help by making the construction more like a box (more rigid). Do you think it could work? Any effect for the sound?

[OB_Newbie]

Hey Knight Rider, how are the B200's coming along?  I'm about to start a build with the B200's and interested to hear your impressions of the B200's now that you have lived with them for some time now.

Cheers!
Rich