OB/755A
Despite the fact that Joe Roberts and I both revere the 755A, he never thought highly of my open baffle set-up. To this day, I'm still baffled as to why he featured my home-brewer article in Sound Practices. 😉 I enjoy the engulfing planar-like airiness of the 755A/OB combo which Joe finds lifeless, boring and lacking in snap.
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| OB + 755A |
Could the dip in this RTA trace be indicating a lack of snap? 😜
Custom-built Altec 618 + 755A
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| J-Rob custom 618 cabinet |
Back in the mid-90s, I owned a pair of original Altec 618s. Those sounded boxy and colored, perhaps due to their lightweight construction. So I traded them for a pair of early sand casted 811 horns...😧 Oh well, live and learn. 😁
When my friend Chong gave me a pair of well braced vintage DIY 618 boxes (allegedly built by an ex-WE engineer and used to house a pair of WE755As), I understood the snap that ticked the Joe-man.
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| ex-J-Rob Altec 618 + 755A |
This is the nicest and most modern looking RTA trace in this survey! Loaded with Altec 755As, the sound is snappy and dynamic while retaining that warm and realistic sheen in the midrange, which evades most speakers marketed in the past 50 years. Although some listeners may still find that quality a vintage coloration...
A visit to J-Rob's
People don't always have to agree to remain friends
Case in point: Joe seems to prefer the Japanese 755 - Lafayette SK98/Hamlin/Pioneer PIM8L - over the ferrite 755C. However, if push comes to shove, I'd take the 755C over the various permutations of the PIM8/20L even if I played a role in reintroducing its virtues to the world. Maybe it's just my sentimental attachment to the 755Cs since they were my very first high-efficiency drivers?
J-Rob sez, "I shouldn't even be talking to you since you like 755Cs." 😆
When I visited Joe in the summer of 2018, he had a pair of 4 cubic foot WE753A look-alike cabs that house Western Electric WE728Bs driven by a spruced up Dyna SCA35 which was recently replaced by a J-Rob cloned Peerless A100 PP 6A5G amp built during the Sound Practices era. Signal source is a Mac Mini>Tidal>Audirvana>Wavelength Audio Brick DAC.
Despite the natural high frequency roll off of the 12" WE728B, it sounded very full-range because of its rich overtones. That is, overtones as musicians use it to describe musical instruments. A high quality violin, piano, or any musical instrument for that matter, possesses rich overtones and this has nothing to do with high frequency extension. Even FFT analyses have failed to identify why del Gesus and Strads sound harmonically richer and have greater carrying power in a good acoustic space compared to a painstakingly crafted modern violin.
I was looking forward to hearing the Silbatone SE300B amp on the floor but Joe hasn't gotten around to re-wiring it for 120V, and also to LPs, but the Gates CB500 was waiting for a resurfaced idler wheel. Then he showed me his next project - Klangfilm horn repros (center background) + Altec and JBL large format compression drivers.
Finally, I was introduced to the pair of Altec 755As perched on top of the WE753C-like cabs. I was quite impressed with the sounds emanating from the 755As!
Since there's no sign that he'll be back anytime soon, with his permission, I took it upon myself to write about this 755A cabinet breakthrough.
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| Silbatone/Dr. Bae WE/Altec 755A box plan Copyright Silbatone Acoustics |
Under no circumstances should this be used for commercial purposes!
Let's see if that works...truth be told, I am well aware that there have been a few enterprising individuals who have benefitted commercially from projects published in this blog. So I'm not holding my breath.
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| John Piro Clone Build Interior walls + back lined with two layers of Kimpak |
I sent the drawing to my buddy John Piro shortly after my Altec 753C cabinets were delivered.
Can anyone distinguish JP's clone from the original Silbatone box?
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| Dr. Bae designed Silbatone box + 755A |
J-Rob comments:
"The cabinets were designed by genius Silbatone engineer Dr. Stefano Bae as a group project for the Silbatone-sponsored DIY/Western Electric forum in South Korea. 100 pairs were quickly sold out, immediately driving up the world price for 755As. The original uses Silbatone's custom silver litz wire, which is said to be an essential ingredient of the original recipe, and top shelf WBT connectors.
Over the years Silbatone designed and made literally dozens of experimental boxes, including back horns for up to four (755A) drivers per side. This was probably the most successful, although rather modest.
My analysis of this untuned little cabinet is that it falls under the 'small box with a hole in it' design paradigm."
Unlike before when I felt the need for at least SE300B power to make the OB/755A sing, now I'm enjoying near-field sounds from my JP cloned Silbatone/Dr. Bae boxes + Altec 755As driven by an SE46 amp with tiny Noguchi FM6WS Finemet OPTs.
The SE2A3dx which normally drives the Altec 753Cs in the main listening area had no trouble driving the Altec 755As in Silbatone boxes to moderately high SPL levels.
Even without the silver litz wire and high tech WBT connectors, I heard all the virtues of the slant 618 box + open baffle combined = detail, snap, macro and micro dynamics from the 618 box + airiness and lack of vintage boxy colorations from the open baffle.The Dr. Bae/Silbatone cabinet transported the 70 year old 755A design to the 21st century in a monitor-sized package!
Hurrah! This is just the kick I needed to get my own Silbatone/Bae cabinets rolling! Nice writeup sir, and thanks! -Nate
ReplyDeleteHey Nate,
DeleteOnce you get your Sil-Bae/755A going, send a picture. Happy listening!
JE
Thinking I might have to try this box with my Pioneer PIM-8 drivers. Could never get the best behavior from the PIM-8s when using the Altec 618 cabinets, but there was a definite *something* there with those drivers...
ReplyDeleteThat is in my "to-do" list. I just have too many things lined up. Keep us posted!
DeleteJE
I keep on trying to comment but it deletes them. Anyway, I built these for my Altec 755A speakers. I kept on bugging Joe Roberts until he took some measurements. I thought they made the 755A's sound great. A very modern type of sound with a studio monitor clarity in many ways. But alas, the bass was not enough for me.
ReplyDeleteI had previously only tried the speakers with some smaller vintage cabinets as well as a 1 cubic foot simple aperiodic box. They sounded boxy and stuffy in the vintage cabinets and a bit muddier in the 1 cubic foot cabinet. Anyway, I sold the 755A's but I'd like to try another speaker in these cabinets, which I still have. Any other suggestions?
Even if J-Rob has no love for the 755C, IMHO, it works very well in this box also. A friend in Manila confirmed this. In fact due to "less snap" there seem to be greater perceived bass response. At some point I'd like to try the SK98/PIM8/2L even if I know that requires an even bigger box than the 755s. I can't think of any vintage 8" or for that matter, any modern 8" which can produce more bass in this small box. It's physically just not possible.
DeleteThanks for dropping by!
JE
Hi,
ReplyDeleteCan it be used on other brands of 8” fullrange speakers? eg:Philips 9710.
Thx
So far I've only tried them with Altec 755As and got a very positive reaction from a friend who is a 755C user. If you get good results from the 9710 or any other 8" driver, please let me know.
DeleteJE
Hi, have you tried a 755E in this cabinet? Would you mind share your impressions? Thank you!
ReplyDeleteI left my pair of 755Es in the attic. ;( But based on audio buddies whose ears I trust and are currently enjoying 755Cs in these cabs, I don't see any reason why it won't work just as well for the 755E.
DeleteAny guidance as to the diameter of the internal wiring? I'm using a 755C in my build. I looked in the Colloms book (High Performance Loudspeakers, 7ed) and he'd doesn't address the issue in any detail. Reading on-line provides more opinion that science. Any thoughts are greatly appreciated.
ReplyDeleteThanks,
/d
I use 16 AWG tinned stranded copper wire for internal wiring. Something like this - https://shorturl.at/wyBI9
DeleteGreat, thanks. I just checked to see if I have a leftover 16 AWG tinned copper wire and I happen to have a few feet of leftover silver wire (Mundorf?) at 18 or 20 AWG. Aside from trial-and-error is there any way to determine if 18 or 20 would be appropriate (I'm thinking math here)? Or should I get off my lazy butt and buy 16 AWG tinned copper? Thanks again, /d
DeleteI sense that you're overthinking. Use your leftover silver wire so you can listen to music ASAP! That's the bottom line!
Deletethanks,
ReplyDeleteTo the different drivers already discussed I can add the Signature Series JBL LE8 AlNiCo's (white cones without any suffix)
ReplyDeleteI've had these cabinets on a back burner, for all too long. But finally they're finished and the first drivers to make their maiden journey were the above. Bought a couple of years ago, as an itch I HAD to scratch, having lusted after these since the early seventies. And I'm very pleased to add they make some awesome noises in these Silbatone cabs. Later on I'll try my WE 755A, 755C, Altec 408A, 403A, PIM 8L, Richard Allan NG8 (two variant) and all the different magnet type Saba Greencones and more. But I'm already off to a very promissing start.
The LE8's sound that excellent I'm in no hurry to swap drive units just yet.
I'm glad you're enjoying your LE8s! You'll be busy listening to your 8" driver collection. Happy listening!
DeleteHaving swapped the following drive units: WE/Altec755a, Altec 755C, 408a, 403a and Pioneer PIM 8L NONE of these have been able to muster quite the same mounted in the Silbatone cabs as the JBL LE8's. My WE/Altec 755a's display a smidgeon more naturalness from the upper mids on up. But IMO NOT enough to counter the several extra octaves of sweet music the LE8's are capable of delevering. To give a true very near fullrange sound. You'd only expect from boxes far larger than the Silbatones.
ReplyDeleteI'm floored to tell the truth. Hadn't quite expected this kind of performance from "a small box with a hole in'it". Instead of being speakers good for some music. I feel these might be all you perhaps ever need playing your music. Mine fills a listening room of 27m² perfectly.
Funny thing; I have prior to these Silbatone cabs toyed with the Altec 755Cs in different cabs and in the JElabs OBs.
Always feeling the need to augment their top end, with either the Fostex FT17H and later the Altec H3000 - thee best - almost delivering a PHYSICAL top end paired with all the delicate filigree you could ask for.
But no need for these running the 755Cs in the Silbatone cabs. For reasons I still ponder. If it's the drivers coming in ear height on mass loaded stands, or rather having some really extraordinary treats such as only playing "bass" when it's present in the program material . Differating clearly between diffent quality recordings. Apart from all this above the combination is packed with dynamics micro as well as macro. And a soundstage to nearly die for with a huge listening window stretching far to both sides of the cabinets, as well tall and deep. All in all these speakers are giving my normal everyday speakers - which shall remain nameless - a rather hard time. And to be honest, although still having quite a stash of 8" FR drive units to go through. I do not think I I'll be able to do much better - which is already far far FAR MORE than I expected.
As heard with two layers of Kimsul to the top bottom and both sides + back panel.
A thing of note:
Knowing I'd be using these cabs as a test bed for a vast ammount of different drivers. I chose NOT to glue the two 18mm battens to the refex slots. Making battens of varying widths to experiment with. Glad I did. Cause it's quite alarming how much these alter - not only bass performance - but also the openness of the whole presentation/soundstage and the focus of all therein. For avvery marked difference in performance.
After much trial and error I have landed on NO battens in the two reflex slots.
As heard in MY chain . YMMV.
So my recommendations for people yet to build these cabinets: Do NOT glue the two 18mm battens in place untill you've at least heard the differences these make to the whole package.
Cheers and happy listening!
P.S.
ReplyDeleteNot owning the oft mentioned "mandatory" Silbatone internal silver speaker wire, I opted for some of my Audio Note AN-SPx instead with excellent results.
Thanks for sharing your valuable experience!
DeleteMy pleasure Joe, and thanks for taking my experiences on!
ReplyDeleteAlways being curious - and as fun project I got hold of a very nice pair of the very small, well TINY, Coral Holey Basket fe103a alnico drivers as an experiment. To see how versatile the Silbatone cabs really are. To cut to the chase; even altering the size of the reflex slots to a much smaller size, I was sadly unable to balance their sound to make them have enough bottom end. Reading very good things about the Corals in OBs, I thought perhaps these cabs could be enough.
I believe to make these tiny drivers balance you'll need a far larger bafflle that the Silbatones have on offer. Like the "Telefunken" OB's often referred to - or small quarter wave line horn cabinets.
Although the CHB 103's show promise with especially female voices, they cannot hold a candle to the far larger JBL LE8 - of course. But what was never the less a bit of a surprise; Even the LE8's upper most registers are far far superior too the Corals. I'd have thought given their small size and the fact they're made from some kind of organic material, perhaps would've outshine the LE8's large alu domes.
But that didn't happen either.
So it's LE8's in Silbatone cabs for me!
Cheers Henrik
STOP PRESS STOP PRESS 😄
ReplyDeleteSORRY Joe, to have posted my latest update/findings with the tiny Coral Holey Basket fe103a's a bit premature.
Please forgive me.
Further experimentation has indeed revealed the Coral fe103a's to be drivers to take into consideration. Even if these cabs were meant for 8 inchers.
Whatever happened to make these changes - much of it during the night - I simply dunno!
Bottomline they are fully acceptable top to the bottom they possess. With everything in between sounding very real, natural and engaging. With voices - fenales in particular being a strong point.
So instead of dismanteling their small subbaffles. I'll keep listening to see if these small Chameleons improves further
Have a nice weekend
Cheers Henrik
I have a couple of pairs of those CHB/FE103s. IMHO, they are outclassed by the Altec 405As - https://jelabs.blogspot.com/2023/03/altec-405a.html - which are very difficult to find stateside because most have been exported to Japan and used in Bonsai hifi setups.
DeleteI'm actually not surprised that the CHBs worked well inside the Silbatone box because I've seen an Asian blog (Korean?) wherein smaller than 8" drivers where being used in that box. IIRC, the Diatone PM610s, Pioneer PIM6s, etc.
To cut to the chase.
ReplyDeleteMy CHBs have kept improving in my Silbatone cabs, where they're mounted on a piece of 5mm plexiglass on top of a sheet of thick'ish felt inspired by a pic I saw of Walt Benders 755a "Bender box", to cover the 192mm hole left by my 8" drivers.
Talking about the elusive WE/Altec755a;
I find the tiny Coral Holey Baskets having so much in common. An exceptionel naturalness, sounding so real and not HiFi. Very organic. - Must be that big nice AlNiCo magnet.
Having speed and "snap" and a certain way with voices that is quite uncanny.
Their bottom end is just about enough. Bright recordings will be bright. But given recordings with a more balanced sound, and ones with a healthy bottom end it's quite impressive the amount of "bass" coming from these diminutive cones.
And like Walt's son Early Bender say about the WE 755a; they really show you the quality in a recording. The CHB's like the 755a's really divide the devine from the merely good you thought were excellent.
Having been through the most common 8" drivers mentioned before, the ones that most resembles the 755a's to these ears are these tiny Coral HB fe103a's. Yup!
They bear so much in common, that I won't hesitate to announce them "the poor man's scaled down version of the 755a"
They're that good.
The Altec 405's you refer to Joe, I have unfortunately never heard myself. So can't say. But having also run the Altec 408a's in the Silbatone cabs, all I can say is they're not nearly in the same class as these CHB's, having colorations that eludes the tiny ones. Which on top of all that's been said have all the traits of a tiny drive unit; exceptionel dispersion, pin point imaging - these can really seperate things while at the same time tie all the strings together, sounding like cut from the same cloth - AND sounding OPEN few or no bigger units quite achieves. I could go on an' on, but suffice to say; had I heard these small gems earlier, there would probably have been many of the drive units I have got, that I wouldn't have bought.
And being quite efficient flea watt owners NEED apply!
Happy listening all
I've finally concluded my survey into all the FR drivers in my collection.
ReplyDeleteI had to realize the tiny Holey Basket for all their virtues, restricted my choice of music too much. Being all too finicky with regard to recording qualities. With only the really good ones with a healthy and natural balance having just enough body to be acceptable in the Silbatone cabs.
I believe these tiny drive units will have to go into e.g. some small quater wave boxes, to get enough bottom end reinforcement.
So I've finally settled for my JBL LE8 1.gen.white cone drivers after having given my Altec 755Cs one last thorough run through. These LE8s can even make the venerable 755Cs sound almost colored and lacking in comparrison.
I believe you say somewhere the Cs giving off the biggest bottom end of all 8" drivers in these Silbatone cabs. They are surpassed by the LE8s in this regard as well.
To all of you having these Silbatone cabs I can only encourage you to seek these JBLs out. You might be just as pleasantly surprised as I was - and still remain.