[-Richard-]

Hi dgator ~

Yes... I am currently running 1 Alpha per baffle. Is this a perfect blending with the B200's for optimal "realistic" sound... meaning true to the sound of unamplified live instruments in a well designed listening space?... admittedly, my research did not go far enough for me to be certain. I did not try 2 Alpha's per baffle... which many OB AC contributors feel is optimal.

There are a few considerations worth noting here. For one thing, I am not interested in bass sound that is not "natural"... natural meaning more bass sound than would be heard in a room with unamplified live instruments. My wife Deborah is a very important part of my listening experiences at home... she actually listens to music more than I do (she is a professional designer, works at home, and listens to music while working on her mac). Deborah especially does not like bass sound that is exaggerated. However, it is quite clear that many music lovers love bass... and it does create a "floor" for the music that helps to establish a powerful sense of rhythm. Cinema lovers, love to hear explosions and thunderous sounds rippling through their floor and chairs, like in the commercial cinema theaters... quite understandable from their perspective.

Deborah and I do not tend to listen to music with powerful driving bass... although it is always wonderful to hear music with that kind of intensity, we listen mostly to unamplified music... although we love jazz and that certainly uses amplified instrumentation... it is just not as pulse driven, as let's say, "rock".

If we were interested in bass driven music, we might find that 2 Alphas per baffle might work better.

The paradox here is apparent... once unamplified music is recorded and played back in our homes over an electronic audio system, it becomes "amplified"... and that process... music recorded by microphones, embedded in a "master" file (CD or tape), transfered to CD disk, read by a laser, the digital data changed back to an analogue signal, pushed through an amplifier, and finally played back by our speaker systems, has all of those distortions already intrinsically built-in to it... and of course it is "amplified" as part of our "natural" listening experience in our homes. The result is that our listening has become highly conditioned by our rarely hearing music "live"... I am speaking of unamplified instrumentation here (not a concert in which the "live" music is actually amplified).

Is it really worth our time and effort to work at getting our home audio systems not to sound "amplified"... meaning to sound as if we are hearing live instruments playing unamplified music in our home? Some music lovers will work years throwing huge dollar amounts toward that end. I like a compromise here. Or more to the point, if the music sounds "alive" (which may not be the same as "live", if you see what I mean) then I am satisfied... that "aliveness" pulls me into the emotional strands of the musical "zone" where I am transported into a sensory dimension that lifts me to the "timeless"... the "present"... where I can feel deeply.

Yes... low-passing the Alpha 15A's... at around 200 to 300hz, does seem to be an optimal cross-over point for many AC OB members using B200's and Alpha's... in my listening experience, with my amplifier, CD player and baffle design, in my room, the extra emphasis on the lower mid-range... which is to say the overlapping of the Alpha's and B200's in that range... seems to come closest to the sound of unamplified live music.

But, I should play with that cross-over point again... you and Lin, have encouraged me to think this through again. I have 2 other inductors with lower cross-over points that I should try in the next few days... perhaps that integration would work better for a more realistic sound. If they sound better I will mention it in this thread to share that with anyone who might be interested.

With Warmest Regards ~ Richard

[Luigi]

Interesting to hear most comment that two Alphas per side is better. I can believe that. Afterall, most of the commercial OBs use two 15s. And they're so amazingly affordable (cepting when you have to ship them half way around the world).

Not having heard two, hard to know. But from having heard one Im convinced that this is a great move forward. So are the kids and they dont even give a darn.
 
Over the weekend some fairly marked changes. I had a few bits of kitchen-offcut MDF - you know, in a white meltica finish - and managed to break the router bit just before finishing the second cut.
Undeterred, I plowed on with a wee jig saw, finished the cuts, inserted the b200s and laid them on their side on top of the U-frames housing the Alphas. Nice.....but the imaging not great. So instead installed the B200 baffle upright and to the outside edge of the U-frames. It looks like hell but sounds like heaven now.

Then got to fiddling around with the BSC filter on the B200s, and the inductor ratings for the Alphas.
It seems as if it almost doesnt matter what size inductor the Alphas use. I recall someone saying they dont even use a filter, and just let them roll off naturally. I think I can see why this might work. Note to self - must try this.
 
On the B200, the inductor changes are easier to discern. Havent messed with the 6ohm resistor in parallel with the inductor, but changed from 0.6mH to 0.4mh and this opened the sound up a little, but without the shouty brightness of the driver au natural.

Anyway, the other good news is that the imaging is no longer head in a vice like, which I can only think was caused by the wings of the old baffle, angled out as they were to about 45 degrees.
The new B200 baffle now has no wings, is more open, and only an inch either side to free air.

The imaging is very real, and the soundstage now much bigger. Moreover, the height of the baffle is now almost a foot shorter, though naturally the footprint width is wider, but overall will be able to make the final baffle shorter, more room friendly and more aesethetically pleasing. I think two 15s might just dominate the room, and anyway, Im loving how low and articulate just a single pair is here. guess it helps that the amp I use, AKSA, does pretty nice bass anyway and the Lightspeed Attenuator lets it all hang out.

In summary, I cannot believe that a $59 driver can add so much to the mix. I'd advise anyone with B200s to "just do it".
Luigi

[canzld]

Hi Luigi

I run the B200s with one 15a per side like Richard and find this is a good fit - although I don't listen to techno or music with a lot of heavy l bass where it might make a difference. Also like Richard, in fact because of his suggestion many moons ago (many thanks Richard), I cross at about 1000Hz, and run the B200 open (mine are phase plug modified so I haven't found BSC necessary). I initially ran the combo with both open, but found it deleterious to imaging and a bit slow sounding. Crossing at 1000hz integrates well using first order. BTW- I found my 15as took a long time to break in - sounded quite fuzzy at first - took a good period before they caught up with the B200s so I suggest you don't fiddle with crossover settings etc too much until everything is well settled. IME - any wings on the baffle were deleterious to imaging as well.

[Luigi]

Canzld
Interesting findings. I have been messing with the B200 BSC filter lately and am wondering whether i should not ditch it altogether. On their own, the B200s seem less edgy with the BSC filter in, but with the Alphas in tow I might give the B200s a lash running full bore.

I have planet-10 phase plugs in mine, so will certainly try ditching the BSC filter for a bit. And will also wait for a while before settling on a final inductor value for the Alphas. Before doing too much more on crossovers though, I need to actually sort a more final baffle that doesn't have the Mrs rolling her eyes every time she sits in front of my "illusions". Delusions, she calls them.

[canzld]

Hi Luigi,

I have the planet 10 plugs also and while I found the B200 as you  say, a bit edgy sometimes on their own - although marvelously clear, the addition of the B200 really transforms their nature. First time I paired them up I wondered where the visatons had gone  . I played my with both full open till I considered the alphas broken in and have run with the crossover at 1000Hz for a number of months now quite happily. I think crossing so high ameliorates the effect of the B200 rising response considerably. I tried to pick the crossover point to tie in with this. One of these days I will get around experiment with crossing at a more traditional lower point. As for baffle size - with the bass support i think you can easily hack your delusions back to the width of the alpha - especially if you cross high. My wife pays so much attention to my speakers that she didn't actually notice when I quietly slipped the alphas into the house and onto the baffle   My three year old had to point them out to her..

[Luigi]

Canzld
Tried the B200s without the filter again and while the old magic is back, so too is the edginess. I dont think the Alphas ameliorate that, at least not in my system. So the filter goes back in again I think. But a new baffle beckons first. Just have to find the time, and get a new bit for the router so I can do some more circle work. Baffle will initially be simple, for just the B200 and Alpha; I like this combo as is. Besides, the Alphas need more run in time before deciding on whether to double up...
Luigi

[canzld]

Canzld
Tried the B200s without the filter again and while the old magic is back, so too is the edginess.
Luigi

add a tube somewhere in the line 

[Luigi]

Canzld
So funny you should say that (add a tube). Because that's what I think is the difference between those who run the B200s full range and those who don't. Bet you anything that the those who do run them full range have either tubed pre/power or tubed CD or analogue front end (probably not tubed).

As it happens, I can include tubes in the line, replacing current CDP with an Ah Tjoeb player I have as back up. Will give that a lash. And I have decided that I will leave the notch filter out for the time being. I think that the B200 really does lose a bit of its musicality and transparency with bits and bobs added to smooth its response.
Luigi

[canzld]

Very true. I think tubes may also play into the differences observed in bass response. Another critical factor that isn't discussed often, in addition to the obvious one of speaker placement, is the nature of the room itself. I have a very lively listening room with lots of hard reflective surfaces (hard wood floor, bare walls), and I try to bear this in mind when analyzing what I hear. In comparison, my father's listening room is almost completely lined with books, curtains, has carpet etc, and presents a quite different listening experience to mine when using  similar gear. Sometimes a perceived lack of bass or enhanced treble is more to do with the room than the speaker.

[-Richard-]

Sometimes a perceived lack of bass or enhanced treble is more to do with the room than the speaker.

Very wise, canzid... very well understood.

In fact it is not too much of a stretch to suggest that in the Open Baffle configuration (especially if you keep things simple) the room acts in a similar way as if it was an enclosed baffle... so in this sense the listener is "inside" of the baffle... the room being the inside... where as in most conventional box speakers, the room is the "outside".

The result is that uncanny dimensional holographic quality similar in visual terms to a 3-D movie... the sound has spatial cues that brings the music to life.

Like you, I did a very thorough listening session starting with the classic flat Open Baffle approach and then added wings and found the musical presentation lost a clear focus... it tended to soften or slur the delicate musical textures. So I do not use wings (although my baffles do use very narrow wings for structural integrity... I did not notice that they detracted from the musical presentation of a pure OB flat baffle design).

I also use Planet 10's "bullet" phase plugs... admittedly, I tried to avoid them at first (even though I had them on hand)... they tended to move somewhat if the music created strong resonances necessitating readjustment. But in the end I had to admit that they do a very nice job of keeping the B200 performing at their best... nice textural information with details galore.

Tubes really do make a difference... my redesigned Heathkit (circa 1950) gives the bass response all of the richness and presence it needs to sound entirely convincing. Also the harmonic richness must be heard to be believed... it sounds like a very well designed 45 SET on steroids (it has a built-in preamp and uses common RCA EL 84 tubes... oh yes... it has bass and treble controls that work beautifully). And the Single Ended tube design probably helps a great deal to allow the B200 to play where they will without that rise in its frequency response being a problem.

I once lived in southern New Mexico and rented a house there... I set up a pair of speakers I was using at that time (pre-OB's) and there was no bass response using the same equipment (including these speakers) I had used in the house I rented before moving to New Mexico. I experimented moving the speakers around and found to my surprise that I could affect the depth of the perceived bass response based on where I positioned the speakers... so your insights are very important here and should be taken seriously by anyone who is building or wants to build their own OB's.

Where I live now it is much less critical... I am doing everything wrong in positioning my OB's and they refuse to sound anything but fantastic. A bit of luck is operating here no doubt.

With Warmest Regards ~ Richard

[Luigi]

I concur with you guys regarding wings; they totally upset the imaging of my OBs, which I discovered when I made a new flat baffle and just stood it up using a set of L brackets and a small piece of wood at the back for balancing. Much better, wider more stable image. Before it was head in a vice, and changed character with small movements of the head. Very annoying. Never suspected the wings but there you go.

I then re-read what MJK said about Uframes, and H frames in association with Eminence Alpha and immediately set out to build an H frame for the Alphas, which are now crossed at around 300Hz. They're a bit nasty as I ran out of wood and had to use some veneered particle board. I have a friend with a CNC miller so it was easy to get exact measurements and cuts. It's kind of cheating, but it really makes creating a box just so simple.

This instantly paid dividends, as I'm now getting reasonably decent bass output from the Alphas - better than with the U frame - and a vast improvement on what the B200s managed. The dog's tail no longer threatens to take the (other) woofer out. Ha. Harder to accidently kick in too.

I also made the B200 baffle separate and therefore mobile on top of the H frame so I can tune the bass of the B200; move it forward and the bass increases, back and it recedes. I think it is using the top side of the H frame for reinforcement.
This is what it looks like.

[Rudolf]

I concur with you guys regarding wings; they totally upset the imaging of my OBs, which I discovered when I made a new flat baffle and just stood it up using a set of L brackets and a small piece of wood at the back for balancing. Much better, wider more stable image. Before it was head in a vice, and changed character with small movements of the head. Very annoying. Never suspected the wings but there you go.

Funny how things can take the same route at different places:



Regarding the influence of wings: I came to my baffle size from a wider flat baffle - without any wings. IMHO it is simply the reduced baffle size/width which is responsible for the better imaging. Wings have to be quite deep (half the baffle width or more) to produce audible cavity effects. But every wing will add to the effective baffle width - even when folded back 90°.

Next step would be to follow my ingenious (or is it ingenuous ) tweeter solution for even better highs ... 

Rudolf

[-Richard-]

Interesting Rudolf. It would be interesting to hear both of your designs to experience if they sound consistent.

If you do achieve "better" highs... can you please do us the favor of saying why they are better... I am most interested myself in finding out if the "highs" can be a bit more transparent... what they are now is quite wonderful... a kind of "sensual" textural quality... but a bit more transparent would be most welcome.

It is all so terribly subjective... I wouldn't mind if it was possible to be a bit clearer about what it is we are after.

Just sharing my thinking here.

With Warmest Regards ~ Richard

[Rudolf]

If you do achieve "better" highs... can you please do us the favor of saying why they are better...
It is all so terribly subjective... I wouldn't mind if it was possible to be a bit clearer about what it is we are after.

Richard,

I should indeed explain, what I experienced as "better" when changing to those back-to-back tweeters. And "better" is of course a subjective assessment. I can show measurements for the drivers and the system in room, but they don`t tell the subjective experience.

First: My driver is not a B200, but a midrange driver - Monacor SPH 176. So I had to add a tweeter anyway. If you walk around the B 200 (or any other wide range driver with a voice coil), there will be a substantial loss of treble when moving to the back side. This does not change, if you add a single forward tweeter. It means that the rearward sound, which is reflected from the walls, is much duller than the direct sound.

Floyd Toole of Harman Kardon has verified time and again, that people prefer loudspeakers, if the complete energy, which is radiated into the room (the power response), has the same frequency content as the direct sound. And this content should have constant directivity (CD): It may get muted, when walking to the side or back of the speaker, but it should not change its frequency pattern.
This is no individual preference, but is common to (almost?) each and every person which took part in Toole's tests.

How does it sound - moving from dull rearward sound to constant directivity?
With the forward tweeter only I was in a constant dilemma: Without an emphasized treble region I got the feeling, that all walls behind and to the side of the loudspeakers were covered with absorbing curtains. A lack of sparkle and airyness, that I did not experience with earphones. A look at the picture will tell you, that there are no curtains at all.
When emphasizing the treble up to the point where the curtains went away completely, quite a lot of CDs became unlistenable because of increased sibilance and shrieking voices. More than once the treble was glued to the speakers.

Then I installed the rearward tweeters in dipole fashion. Just connected them in parallel with reversed phase of the rear one and dialed the volume in. Until today I have felt no need for attenuation of the rear tweeter.

The result is a much more relaxed treble region. Harpsichords are very "silvery", while Pink (who must have really treble-deaf producers) is still listenable. Imaging has NOT changed - it is still as precise (or unprecise) as before, regardless of the increased reflections. What has increased is the sense of openness, the absence of the front wall. Not to confuse with "depth", which hasn't changed either.

In general listening has become even more immersive and easy over a longer time.

I have to add that this change in experience HAS to be rather room dependant. And it is NOT the same as just pointing any odd additional tweeter at the ceiling for more "air". But it is a change that I can recommend to everybody to (at least) try.

Rudolf

[-Richard-]

Beautifully written Rudolph... very clear and well thought out.

I am deeply grateful for all of the very fine help our community shares with all of us in this wonderful forum of AudioCircle... much of it helps us to get through the technical issues of how things work together... how to put our Open Baffle speaker components together, for example, for optimal performance... why some drivers work better than others in different applications and so on.

There is not much written about that "subjective" response to what we are hearing and why it works for us. Your writing gives me an immediate sense of what you are hearing that works so nicely for you... the "aesthetics" of your listening experience. I deeply appreciate your sharing that with us.

Now it is a quesition of finding the right (and hopefully inexpensive) tweeter to use in that backward configuration and giving it a try... any suggestions from your own investigations?

With Warmest Regards ~ Richard

[Luigi]

With my old OBs which had wings from the bottom to the top, I just could not get true imaging and removed the rear firing tweeters FT17H I was using then. Which of course did not do anything to the imaging.
Bt now that I have the imaging better sorted with a flat baffle, will again try hooking in the
Fostex tweeters, again rear firing only.
I found there was naturally more treble info when adding the tweeter before and more body to the images so will see how things go when they are hooked onto the back of the new baffles. It is easy enough to do, so will report back on how it works soon. But off to Aussie this weekend with work so it may be a few days before i get a chance.
Glad to have sorted out the imaging problem all the same; it was definitely the influence of small wings, which ran up higher than the B200s, in fact right to the top of the speaker.
These were the old baffles alongside the new:

[fakamada]

I'd strongly suggest using different tweeter on the back of baffle. Note that horn tweeter is suited to match b200 off axis response in front ! Wideranger radiates very widely in the back so using dome tweeter blends better.

Joachim Gerhard (AudioPchysic) is currently using SEAS 19TFF1 in the back of his private openbaffles.

[canzld]

Hey Luigi,

Just saw your post - parallel thought processes or somethin'...




I agree with your findings on bass response - significant improvement. Imaging - well I had pretty good imaging before with the flat baffle so if it's better now the difference is small - I have crappy sonic memory so it's hard to tell. To me it also sounds like the rising B200 response is brought to the fore slightly more with the smaller baffle

[Rudolf]

Just adding a tweeter in the back of the B 200 could achieve a bit more "airyness", but will do next to nothing for a better integration of the treble. You need to roll-off the B 200 where it looses its dipole pattern and roll-in a real tweeter dipole. This could be a planar tweeter with open back like the B&G Neo 3 or a pair of really small dome tweeters mounted back-to-back, like I do.

Rudolf

[-Richard-]

"You need to roll-off the B 200 where it looses its dipole pattern and roll-in a real tweeter dipole. This could be a planar tweeter with open back like the B&G Neo 3 or a pair of really small dome tweeters mounted back-to-back, like I do."

Hi Rudolf ~

Thanks so much for the tweeter recomendations and for pointing out the dangers of not fully understanding the issues surrounding integration with the B200's. I have serval questions for you that should help me, and other audiocircle members working with Open Baffle speakers, to better understand what is going on here.

1. Can you clarify what you mean by pointing to the B200 lossing "its dipole pattern?"

I assume you are suggesting that the B200's lose their dipole pattern somewhere in their upper frequencies. Does that imply that the sound in that upper frequency range only radiates forward... losing their back-wave characteristics?

2. What is the range where this "effect" begins... and therefore what is the cross-over point we would be looking for when implimenting the tweeter?

3. If you are using 2 tweeters per baffle, as you suggest ("a pair of really small dome tweeters mounted back-to-back"), then the forward facing tweeter is radiating those upper frequencies (where the tweeter plays) directly into your room... in that case what "extra" thing does the back radiating tweeter do that makes it more effective, in the Open Baffle application, than just the one front facing tweeter is doing?

4. Also, is there an issue with a possible "cancellation" of frequencies arising from the back-to-back arrangement of the tweeters?

Note: the sensitivity of the dipole version of the B&G Neo 3 is 90.5 db... this tweeter might not be able to keep up with the 97 db sensitive B200. A more sensitive tweeter may have to be used.

I deeply appreciate your sharing this very interesting and important information with us.

With Warmest Regards ~ Richard