[-Richard-]

About a year ago a very good friend, Dr. Steven Rayle, a member of AC who has the fascinating knack of always selecting some of the best audio equipment I have ever heard, recommended a totally redesigned Heathkit 151A integrated amplifier in Triode mode by the master Korean audio design Sam Kim, of Sam’s Audio Laboratories, in Quebec, Canada. He not only recommended it... he raved about it. Steven uses it to drive his horn speakers. Sam’s Platinum Triode version of the Heathkit 151A has 7 powerful triode tube watts... for my Open Baffle speakers with their 97db efficiency that is “an embarrassment of riches” as Dr. Dan Mason used to say.

http://www.samsaudiolabs.com/

Steven and I talked about the possibility of his driving to Ojai for an audio weekend that would allow us to hear several amps, including his Sam Kim Heathkit 151A, in a kind of shoot-out on my Open Baffle speakers. Steven got very busy so that never happened.

Steven’s description about the performance of Sam’s Heathkit 151A on his horn speakers began to haunt me... I trust Steven’s sense of were the magic lies in audio having shared with him several audio shoot-out weekends in which we listened to a great deal of exceptional gear and compared notes. One day I woke up thinking I had to own Sam’s creation... call it an “insight”... just a sense that this was going to be the ultimate amplifier for me and solve any integration issues I might have with my Open Baffle speakers.

Sam’s total circuit transformation/re-design still uses a quad of EL 84 power tubes... but the rest of the tube compliments actually depends on which tubes Sam feels reflects his most up-to-date technical understanding of what works best in his circuit. My Heathkit circuit uses 2 pairs of 12AX7’s and 12AU7’s (Sam feels the 12AU7’s have better gain and microphonic characteristics in the pre-amp section) and a pair of 6EU7’s for the phono stage (Sam’s Platinum Triode Heathkit 151A has a phono section for those of you using LP’s as your musical medium of choice)... Sam uses the original transformers that come with the Heathkit... Sam believes that these fully-burned-in old iron transformers yield a sweetness and harmonically rich tone impossible to attain in modern transformers that have not been allowed to “age” and settle-in to their optimal musical and tonal performance potential.

Sam’s Heathkit also has tone controls... and they are a dream come true... and one of the most important reasons that Sam’s Heathkit 151A is such an important and potent integrated tube amplifier for Open Baffle speakers.

I have been playing Sam’s Heathkit for a few months now and the sound it incredible... the tonal range is easily the richest and widest I have ever heard on any amplifier... and I have heard and owned many of the best triode SET (and digital) amplifiers out there... the textural instrumental information has a depth, detail and precision that makes every other amplifier I have heard sound dull and recessive in comparison and there is a totally 3-Dimensional open spatial field that completely recontextualizes the space of my listening room to sound like whatever original venue the music was recorded in. Music recorded in large spaces like cathedrals actually sound like we are in a huge vaulted cathedral and the sound goes on forever. Voices sound thoroughly human, rich, articulate (no trace of sibilance or smearing) and with a palpable ripe presence that hovers into your room and pulls at your heart. The entire effect of Sam’s Heathkit 151A is that it has the speed, immediacy and dynamics that matches perfectly with the potential of my Open Baffle speakers to render music with a completely vivid, alive and real musical perspective. Indeed there are times when the musical color pallet sounds as if the music had been transformed into brilliant jewels of sound.

Here are some things that Steve of Sam’s Audio Labs has said about Sam’s circuit design:

“The unique engineering that goes into every Sam’s Audio Labs integrated amp is Stabilization circuitry in the power stage. The advantages are that his amplifiers are extremely reliable, extremely low variation in the power current to the tubes, so for example you will never have to change rectifier tube.

Sam uses what we call Compensation Circuitry what used to be called tone controls... Sam designs his Compensation Circuity so that at 6:00 the sound is perfectly neutral and when you put it at 3:00 or 1:00 you are actually compressing the original signal so that the ORIGINAL SIGNAL STAYS PURE. All other tone control designs boost the signal 10db 20db or 30db changing and distorting the ORIGINAL SIGNALS.

Also all of our units are extremely linear......Sam is a master at linearity. Sam’s favorite expressions about his circuit design is  “These amps contain NO MSG”

Bias to the tubes in most 6BQ5 design amps is 65 to 72 milliamps... Sam’s design is 38 to 42 milliamps while maintaining the richest possible tonal and harmonic presentation... the result is no stress on tubes, transformers, or capacitors... Sam’s amps are extremely stable and reliable.

Sam’s Heathkit 151 A uses 2 separate (dual) volume controls to balance the amplifier which is the best way to attain perfect balance of both speakers.

There is a great deal more I can say about our innovative circuit design but Sam and I don’t want to give away too many of our secrets... please let everyone know I would love to hear from them if they would like to speak with me about Sam’s Platinum Triode Heathkit 151A integrated amplifier. They should check out the website too to see what else we offer in the way of totally new innovative circuit re-designs for the great retro-looking amplifiers from America’s golden age in tube design.”

Sam gets $2,900 for the Platinum Triode Heathkit 151A. It takes a minimum of 160 to 190 hours for Sam to rebuild his new circuit from scratch (Sam first strips the old Heathkit chassis and thoroughly cleans it). When you call Sam’s Audio Labs in Quebec Canada, you will be speaking with Steve who is Sam’s partner and contact person for all sales. Steve is a wonderful person to work with... he is a dedicated music lover and he has an unbounded love and enthusiasm for the extraordinary work that Sam does. His phone number is 514.880.3587. If Steve does not answer the phone, please call back... Steve apologized to me but said he can’t return calls on his cell phone to the USA.

With Sam’s Heathkit 151A no other form of equalization is necessary for my Open Baffle speakers... they impart an entirely organic fully integrated sound to my Visaton B200 and Eminence Alpha 15A drivers hooked up in parallel (the B200’s play full range and the Alpha is crossed over at around 1200 Hz)... the bass controls set at 12:00 noon is so powerfully deep (super fast articulate bass... no bloating) that I have to turn down the bass controls or else my walls begin to shake. It is really great to be able to fine-tune the sound for each recording.

Incidentally, just before I was to purchase my Heathkit from Steve at Sam’s Audio Labs, one came up for sale on Audiogon which I purchased immediately. It sounded fantastic when I received it except that the transformer ran a bit hot. Steve at Sam’s told me to send it back to him and Sam would go over the amp completely and find out why it was operating on the hot side. Sam replaced the old set of NOS EL 84 tubes with a new set of NOS RCA’s which I sent him and readjusted the bias to perfectly match the new EL 84 tubes. The Heathkit runs nice and cool now. Steve and Sam treated me with the same high level of excellent professional service just as if I had purchased the Heathkit new from them.

I am finally finished searching for the perfect amplifier for my Open Baffle speakers. Sam Kim’s Platinum Triode Heathkit 151A integrated amplifier is a dream come true.

With Warmest Regards ~ Richard

[BrassEar]

Wonderfully written post, as usual Richard.

Yes, there is magic in them thar EL84 tubes (taking nothing away from Sam's talent). I am currently using a 1962 Scott LK-84 integrated with two pairs of El84 tubes and I share your experience. I think simple OBs with EL84 amplification is some kind of magical cosmic accident. SET is also good but rarely has the power and bottom end punch to satisfy long term. EL84s in push-pull does the job on my 2 x Alphas with waveguide/compression driver DIY speakers. I get a fully fleshed out, holographic, and organic presentation that is nothing like I have ever heard before. I have been an audiophool for so many years now I know that when you get it all to lock in on the magic - don't change it. RELAXED is the term I keep returning to.

Makes me almost feel sorry for audiophiles that try endless combinations of expensive gear with Class A ratings from such and such high gloss audio pubs and never find what they are craving. It's all right there with simple OB designs and 40+ year old tube technology.

Thanks to you Richard, Dr. Mason, and many others here for bringing these affordable solutions to light. And so appropriate in these recessionary times.  I think this is the least expensive system I have ever assembled and it is hands down the most realistic and enjoyable. Having a glass of CA Merlot right now and listening to some late night jazz and watching the tubes glow!

[ZLS]

About a year ago a very good friend, Dr. Steven Rayle, a member of AC who has the fascinating knack of always selecting some of the best audio equipment I have ever heard, recommended a totally redesigned Heathkit 151A integrated amplifier in Triode mode by the master Korean audio design Sam Kim, of Sam’s Audio Laboratories, in Quebec, Canada. He not only recommended it... he raved about it. Steven uses it to drive his horn speakers. Sam’s Platinum Triode version of the Heathkit 151A has 7 powerful triode tube watts... for my Open Baffle speakers with their 97db efficiency that is “an embarrassment of riches” as Dr. Dan Mason used to say.

http://www.samsaudiolabs.com/

Steven and I talked about the possibility of his driving to Ojai for an audio weekend that would allow us to hear several amps, including his Sam Kim Heathkit 151A, in a kind of shoot-out on my Open Baffle speakers. Steven got very busy so that never happened.

Steven’s description about the performance of Sam’s Heathkit 151A on his horn speakers began to haunt me... I trust Steven’s sense of were the magic lies in audio having shared with him several audio shoot-out weekends in which we listened to a great deal of exceptional gear and compared notes. One day I woke up thinking I had to own Sam’s creation... call it an “insight”... just a sense that this was going to be the ultimate amplifier for me and solve any integration issues I might have with my Open Baffle speakers.

Sam’s total circuit transformation/re-design still uses a quad of EL 84 power tubes... but the rest of the tube compliments actually depends on which tubes Sam feels reflects his most up-to-date technical understanding of what works best in his circuit. My Heathkit circuit uses 2 pairs of 12AX7’s and 12AU7’s (Sam feels the 12AU7’s have better gain and microphonic characteristics in the pre-amp section) and a pair of 6EU7’s for the phono stage (Sam’s Platinum Triode Heathkit 151A has a phono section for those of you using LP’s as your musical medium of choice)... Sam uses the original transformers that come with the Heathkit... Sam believes that these fully-burned-in old iron transformers yield a sweetness and harmonically rich tone impossible to attain in modern transformers that have not been allowed to “age” and settle-in to their optimal musical and tonal performance potential.

Sam’s Heathkit also has tone controls... and they are a dream come true... and one of the most important reasons that Sam’s Heathkit 151A is such an important and potent integrated tube amplifier for Open Baffle speakers.

I have been playing Sam’s Heathkit for a few months now and the sound it incredible... the tonal range is easily the richest and widest I have ever heard on any amplifier... and I have heard and owned many of the best triode SET (and digital) amplifiers out there... the textural instrumental information has a depth, detail and precision that makes every other amplifier I have heard sound dull and recessive in comparison and there is a totally 3-Dimensional open spatial field that completely recontextualizes the space of my listening room to sound like whatever original venue the music was recorded in. Music recorded in large spaces like cathedrals actually sound like we are in a huge vaulted cathedral and the sound goes on forever. Voices sound thoroughly human, rich, articulate (no trace of sibilance or smearing) and with a palpable ripe presence that hovers into your room and pulls at your heart. The entire effect of Sam’s Heathkit 151A is that it has the speed, immediacy and dynamics that matches perfectly with the potential of my Open Baffle speakers to render music with a completely vivid, alive and real musical perspective. Indeed there are times when the musical color pallet sounds as if the music had been transformed into brilliant jewels of sound.

Here are some things that Steve of Sam’s Audio Labs has said about Sam’s circuit design:

“The unique engineering that goes into every Sam’s Audio Labs integrated amp is Stabilization circuitry in the power stage. The advantages are that his amplifiers are extremely reliable, extremely low variation in the power current to the tubes, so for example you will never have to change rectifier tube.

Sam uses what we call Compensation Circuitry what used to be called tone controls... Sam designs his Compensation Circuity so that at 6:00 the sound is perfectly neutral and when you put it at 3:00 or 1:00 you are actually compressing the original signal so that the ORIGINAL SIGNAL STAYS PURE. All other tone control designs boost the signal 10db 20db or 30db changing and distorting the ORIGINAL SIGNALS.

Also all of our units are extremely linear......Sam is a master at linearity. Sam’s favorite expressions about his circuit design is  “These amps contain NO MSG”

Bias to the tubes in most 6BQ5 design amps is 65 to 72 milliamps... Sam’s design is 38 to 42 milliamps while maintaining the richest possible tonal and harmonic presentation... the result is no stress on tubes, transformers, or capacitors... Sam’s amps are extremely stable and reliable.

Sam’s Heathkit 151 A uses 2 separate (dual) volume controls to balance the amplifier which is the best way to attain perfect balance of both speakers.

There is a great deal more I can say about our innovative circuit design but Sam and I don’t want to give away too many of our secrets... please let everyone know I would love to hear from them if they would like to speak with me about Sam’s Platinum Triode Heathkit 151A integrated amplifier. They should check out the website too to see what else we offer in the way of totally new innovative circuit re-designs for the great retro-looking amplifiers from America’s golden age in tube design.”

Sam gets $2,900 for the Platinum Triode Heathkit 151A. It takes a minimum of 160 to 190 hours for Sam to rebuild his new circuit from scratch (Sam first strips the old Heathkit chassis and thoroughly cleans it). When you call Sam’s Audio Labs in Quebec Canada, you will be speaking with Steve who is Sam’s partner and contact person for all sales. Steve is a wonderful person to work with... he is a dedicated music lover and he has an unbounded love and enthusiasm for the extraordinary work that Sam does. His phone number is 514.880.3587. If Steve does not answer the phone, please call back... Steve apologized to me but said he can’t return calls on his cell phone to the USA.

With Sam’s Heathkit 151A no other form of equalization is necessary for my Open Baffle speakers... they impart an entirely organic fully integrated sound to my Visaton B200 and Eminence Alpha 15A drivers hooked up in parallel (the B200’s play full range and the Alpha is crossed over at around 1200 Hz)... the bass controls set at 12:00 noon is so powerfully deep (super fast articulate bass... no bloating) that I have to turn down the bass controls or else my walls begin to shake. It is really great to be able to fine-tune the sound for each recording.

Incidentally, just before I was to purchase my Heathkit from Steve at Sam’s Audio Labs, one came up for sale on Audiogon which I purchased immediately. It sounded fantastic when I received it except that the transformer ran a bit hot. Steve at Sam’s told me to send it back to him and Sam would go over the amp completely and find out why it was operating on the hot side. Sam replaced the old set of NOS EL 84 tubes with a new set of NOS RCA’s which I sent him and readjusted the bias to perfectly match the new EL 84 tubes. The Heathkit runs nice and cool now. Steve and Sam treated me with the same high level of excellent professional service just as if I had purchased the Heathkit new from them.

I am finally finished searching for the perfect amplifier for my Open Baffle speakers. Sam Kim’s Platinum Triode Heathkit 151A integrated amplifier is a dream come true.

With Warmest Regards ~ Richard

    I second everything that Richard says.  Given speakers of sufficient efficiency it is hard to imagine a better amplifier. 

    There are many recording that will tell you what the 151 is capable of, but the one I used for a  reference was Ishafan from Duke Ellington's Far East Suite.  The Johnny Hodges solo on Alto Saxaphone a work of art. 

[panomaniac]

Open baffle - 7 watts.  How?

For 7 watts you better be near 100dB/watt on your rig.  I've never seen an OB rig (that had bass) anyhwere near that.
What the heck are you using? 



(yes, i love low power amps - but have not seen one that would do OB bass)

[MJK]

Open baffle - 7 watts.  How?

For 7 watts you better be near 100dB/watt on your rig.  I've never seen an OB rig (that had bass) anyhwere near that.
What the heck are you using? 



(yes, i love low power amps - but have not seen one that would do OB bass)

The key is two Alpha 15A woofers. Without EQ in a properly sized baffle you can get mid to high 90's efficiency. You can go passive with a Lowther DX2 or PM6A and get 94 dB/W/m without any EQ down to 40 Hz. Big powerful efficient OB performance. I keep telling people that high Qts drivers like the Alpha 15A are required for OB but not many people seem to listen. Hence, I don't post much any more on DIY forums.

[panomaniac]

OK, 2 Alphas in parallel on a big, MJK size baffle with wings.  Yeah, I can imagine that working with 14 watts*.
But alas, I have yet to hear such a rig!   :-/  (I need to get out more...)

*(4 ohm load / 7.5V / 1.87A)  Can an amp like this supply that on its 4 ohm tap?

[MJK]

OK, 2 Alphas in parallel on a big, MJK size baffle with wings.  Yeah, I can imagine that working with 14 watts*.
But alas, I have yet to hear such a rig!   :-/  (I need to get out more...)

*(4 ohm load / 7.5V / 1.87A)  Can an amp like this supply that on its 4 ohm tap?

No, not a huge baffle with wings. All you need is a 20" wide by 40" to 48" tall baffle. People need to start engineering OB designs and stop making them up on the fly and wondering why they have no bass. Use engineering to pick the drivers, crossover points, and the baffle shape and size. OB design is where TL design was 10 years ago, it is a trial and error approach that results mostly in error. If people would think about the physics involved in an OB the answers would be obvious.

[BrassEar]

I have two Alpha 15As on a 19.5-inch wide by 48-inch tall baffle. No EQ. Of course I do use multiple small powered subs ala Geddes but I am lucky in that my Scott has a preamp out center channel to drive them. I just augment the OBs with subs around 60-75 Hz or so. Running that Alpha out to 1 kHz or so gives you the full measure of OB dipole depth and magic. All IMO.

[-Richard-]

Hi Panomaniac ~

Admittedly... I am rather confused by your suggestion that a well-executed 7 watt Triode push-pull EL 84 tube amplifier would have difficulty rendering a powerful musical performance from a simple dual-driver Open Baffle configuration like mine.

In fact I used only 2 watts from Jeff Korneff's 45 SET tube amplifier for well over a year and the performance was quite wonderful... granted 2 watts will not generate the dynamic inner thrust... that remarkable sense of musical urgency... that 7 watts will generate. But everything was there and it sounded quite rich and robust.

I am also using the 4 ohm tap on Sam's Heathkit 151A for my single Alpha 15A and B200 hooked-up in parallel.

The sound from my simple Open Baffle speakers is electrifying and explosive... I cannot even begin to open up what the amp can do without getting my neighbors upset.

Dan Mason has always remarked that in many cases it is the cross-overs that tend to sap energy from a complex driver hook-up. My hook-up uses just one (small) coiled inductor... the Alpha is 97db efficient much like the B200... and the combined 4 ohm load does not seem to pose any problems to the amp.

Hi MJK ~ Yes... I can see that it must seem to you sometimes that you are that rare voice in the wilderness that is revealing that simplicity of design can achieve remarkable (actually quite fabulous) performance... I must admit that sometimes it seems as if many people who go the DIY route want to work with incredibly complicated solutions in order to satisfy their need to engage multiple layers of technology.

Honestly... 2 Alpha's per baffle in my 20' x 26' listening room... using Sam's Heathkit 151A with its tremendously fast, articulate and powerful bass tone controls would be too much information in that frequency range for the music I listen too. One Alpha 15A with the B200 running full range creates a convincing musical floor. I can easily see, however, that if large orchestral works was someone's main musical appetite... or perhaps very powerfully rendered rock & roll or other music that uses powerful bass as an important musical "texture" that 2 Alpha's would be ideal (assuming their house could "contain" that level of powerful bass sound).

Perhaps if I move to a house that is not quite so close to my neighbors in the future, 2 Alpha's per baffle might be a perfect solution. I purchased the Alpha's thanks to your suggestions (and frequency graph) and Scorpion's post about it.

My baffle size is 23" wide x 36" high and it seems to support the bass frequency very nicely (augmented by the bass tone control).

I have always been deeply grateful to you, MJK, for your invaluable and extremely generous help and advice... I hope you can always feel comfortable sharing your insights with us.

Hi ZLS/Zack ~

I had no idea you also have a Sam Heathkit 151A... I know your listening experience must be quite fantastic. I will PM you very soon to ask you a few questions.

Hi BrassEar ~

Yes... Dr. Dan Mason changed my musical life and my way of thinking about audio... bless him!!

Nice to hear that you are enjoying your EL 84 amplifier as an important part of the magic behind your Open Baffle experience. I don't quite know what took me so long to discover what these magical (and relatively reasonably priced) tubes in a well-executed push-pull circuit can do to bring out the fullest potential of the incredible Open Baffle speaker experience.

Incidentally, I spoke to Dr. Dan Mason recently and he is also using an EL 84 tube amplifier from yester-year for his newest Open Baffle magic-show... a Magnavox, I believe, that he has reconfigured into Triode mode. He loves his EL 84 amplifier as much as we love ours!!!!

With Warmest Regards ~ Richard

[mcgsxr]

Yes, the EL84 amp can work wonders.  I use a 3-5 wpc single ended Magnavox myself.

For me, the secret is biamping (woofers have their own 300w digital amp), and crossing over at the line level, rather than speaker level.

As for my baffle design, I call into the "on the fly" camp.  I am still using the design I first built 4+ years ago.

I am designing a new one, and will leave the "on the fly" camp behind in the next iteration.


Thanks for sharing Richard!

[tubesguy2]

Sam gets $2,900 for the Platinum Triode Heathkit 151A. It takes a minimum of 160 to 190 hours for Sam to rebuild his new circuit from scratch (Sam first strips the old Heathkit chassis and thoroughly cleans it).

When are those darn Canadians finally going to update their minimum wage law?     Seriously, while I have no doubt that you are enjoying your new amplifier, I doubt that Sam really spends four to five work weeks to complete each amp, now that the design is finished and (presumably) he has parts on hand.  It's just parts, right?  There's no extensive casework or other labor-intensive work, I wouldn't think.

At any rate, always nice to hear from an audiophile without buyer's remorse. Very nice review. - Pat

[-Richard-]

Hi Mark(in Canada) ~

Please post a picture of your latest Open Baffle design once you have it ready... I am most interested to see your latest thinking.
Glad to hear you are enjoying the EL 84 magic as well.

Tubesguy2 ~

I have spoken to Steve at Sam's Audio Labs many times over quite a few months and he seems to always refer to Sam's actual time spent in "tuning" each amp to around 160 to 190 hours... Steve says that Sam actually takes parts in and out of each amp while critically listening to it until it sounds perfect sonically. Steve also mentions that most amps are done on the assembly line... that 'commercially' manufactured amplifiers are simply put together... as you suggest... and that assembly-line methods gives most amplifiers a generic sound and is why so many amplifiers sound the same.

What Sam does is to fine-tune the values of the parts he uses until the amplifier sounds right... and that apparently takes time. All I can tell you is that the sound is like no other amplifier I have ever heard... possibly the magic of the EL 84 tubes and a well-executed circuit has a lot to do with it... but I suspect that the real difference between Sam's work and other terrific amplifiers I have heard is the extra time he puts into that fine tuning work.

All I can say is that it sounds quite fabulous and I am very happy with it... and the tone controls make it the perfect amplifier for Open Baffle designs (especially if you don't want to fuss with special amplifiers just for the woofer drivers). When you use one really terrific amplifier for all of your drivers (assuming their combined sensitivity is in the 90db and higher range) you get a wonderful holographic wholistic sound.

Warmest Regards ~ Richard

[panomaniac]

Hi Richard -  Certainly I did not intend to insult you, your amp or your rig!  I was just surprised, that's all.  Why surprised?
'cause I've heard and built literally 100s of small amps in the 7 Watt range.  Lovely as there were, they just didn't seem capable of driving OB bass.

But remember, I did say  "But alas, I have yet to hear such a rig!"  By that I meant an OB rig with the Alpha or any other driver with a Qts of 1 or higher.  People seem to love them, I just have not heard one yet.
What I have heard in the past couple of years includes:
Bastanis
Linkwitz Orion
Nightingale
Magnepan
Hawthorn (with and without Augie)
Emerald Physics CS1
GR Research
Nelson Pass Lowther + 2x10
several home made rigs with 12s or 15s or 18s or dual 18s.
And some I'm sure I've forgotten.

As you'll see, not an Alpha in the group!  So I really can't judge that driver.

None of these I've heard or built could do good bass with 7 watts, so most of them were active - at least the commercial designs.  Thus my surprise that your nice low power amp is able to push them. 

People need to start engineering OB designs and stop making them up on the fly and wondering why they have no bass.

Ummm....  and just who would these people be, Martin?  Any of the above listed? (OK maybe one)  Or Rudolph or Erling or Graham or John K?
You can certainly accuse me of making them up on the fly and you'd be right, even tho I owned your worksheets for a year. Heck, making it up on he fly half the fun of open baffle!  But the rest of these guys?  Come on.

So I'm ready to be surprised by the Alphas.  Up to this point no OB I've ever heard has real bass without massive EQ - even if the owner thought it did!  Clean? Sure. Real? No.

[opnly bafld]

Up to this point no OB I've ever heard has real bass without massive EQ - even if the owner thought it did!  Clean? Sure. Real? No.

Did the P-Audio at RMAF (that was keeping everybody on the 3rd floor up at night  ) have real bass?
Did it have EQ? 

Lin 

[-Richard-]

Hi Panomaniac ~

You wrote: "Open baffle - 7 watts.  How? For 7 watts you better be near 100dB/watt on your rig.  I've never seen an OB rig (that had bass) anyhwere near that. What the heck are you using?"

You seemed to be honestly questioning whether 7 tube watts could play an OB to a level that you feel is adequate for serious listening pleasure. I tried to answer your question with a factual accounting of my experiences with a 2 watt SET amplifier and Sam's 7 watt Triode Heathkit 151A... it never occurred to me to feel offended in any way... I always enjoy reading your insights and I am grateful to you for sharing with our Open Baffle community your experiences and suggestions.

Your experience with "commercial" Open Baffle speakers places you in a unique position to compare what is really going on in that burgeoning field... a very interesting place to be... it seems you are doing a good amount of research. It also seems that your experience building your own low watt amplifiers is commendable. That also places you in a unique position to really know what is going on in that world as well. So you have every right to present your audio experiences as a list that few of us can match as proof that your insights are well founded.

I think the whole question of "real" bass is rather subjective in one important way... personally I am not interested in the music that is being re-created in my listening space actually replicate the same levels that the composer/player reached while performing in the recording space... I prefer the sound to be "tailored" to the levels in my listening room that sound appropriate for that space... so I limit the scale of the sound to "fit" what feels comfortable for Deb and I (and our neighbors)... and of course that affects the levels of bass that are generated as well.

Deb does not like bass that is overemphasized in the musical presentation unless the composer/player feels it is absolutely necessary to the intelligence/understanding of what their musical intention is... and I agree entirely. So for us "real" bass would probably find you (and many serious music lovers) feeling that something vital is missing from our home audio experiences.

But honestly, Panomaniac, 7 Triode tube watts is really an extraordinary amount of power for drivers in the 96db/97db range. If one's room is not overly large, with very tall ceilings, and not overly carpeted with large drapery and large sofas, you should have all the power you need... and then some. I am not at all certain why your experiences and mine in this regard seem so far apart. So be it.

One more thing... the reason I am so excited by Sam's Heathkit 151A is that the tone controls are most certainly a kind of EQ that I am using to get the most from the Alpha's ability to generate convincing bass... that was actually the main reason I sought out this integrated amplifier... I am not at all a fan of "separate" EQ devices... I do not like the op amps they use... I think I hear them... I do not like the way they compress the sound when you augment frequency gamuts with them... I do not like all the extra cables... it feels like fussing to me. OK... I suppose I am old-fashioned... I like... no make that love... tone controls that are exquisitely designed... that give you powerful bass if you want it... or heavenly treble tones if you wish to take advantage of a recordings upper frequency information without ones ears and nerves being agitated and stressed out. It is EQ... but very user friendly EQ. And it works!

So there are 2 schools of thought here. MJK and I (and Dr. Dan Mason and many others) honestly feel that less is more... we "design" (DIY) our home stereos with that objective in mind. It is an aesthetic decision. It is the basis for almost the entire ground of the late ninteenth century and twentieth century sense of modernity... it is also the essence of good science: "make things as simple as you can, but not simpler" Einstein. 

Am I offended? Please, Panomaniac, accept my sincere affirmation that I am not offended... we are merely looking at this whole field of Open Baffle design together... all of us... and making suggestions to each other of what approach could work based on our personal experience.

With Warmest Regards ~ Richard

[panomaniac]

Hey Richard,
 thanks for your kind reply.  As you can tell, I wasn't here to slam anything, just surprised because I had not heard it done before.  If high Qts drivers can give a good tonal balance on OB (and they should) then massive EQ and power should not be needed.  I quite agree with you that a system sensitivity of above 94dB/W can really move some air with a few watts.  That was my big surprise when I sumbled onto the high efficiency rigs and SET amps back in the mid 80s.  A real game changer.  The only problem for me is that I have yet to hear an OB rig that sensitive in the bass - and I don't know why.  But I'd love to!

(I'd love to play at live levels too, but also feel that it does not often fit will in a domestic setting.)

Did the P-Audio at RMAF (that was keeping everybody on the 3rd floor up at night  ) have real bass?
Did it have EQ? 

Real bass?  Almost - but it could be better, deeper. JB is working on that. It was running on a 25W tube amp, BTW.
EQ?  You betcha!  In the form of a very low Low Pass Filter.  All that inductance is a form of EQ.  Trading away the rising mid to get a better tonal balance.  That is the trade-off of most OB.

But I won't go into that here, it's unfair to Richard, as this is a thread about his amp, not OB bass.  That deserves another thread.

[fivestring]

Panomaniac, I believe you`re right. I have worked with various dipole configurations throughout the years, among them with two
Peerless SLS 12 woofers on a simple I baffle (45 cm wide and 1.2m tall) and judging from the amount of mid/high attenuation,
my estimate for sensitivity was about 80 db, after passive EQ with one big coil. For my tall OB project (six 12 inchers),
my estimate for sensitivity was about 86 db, which seems a lot to me, but the baffle was 215 cm tall and 60 cm wide.
If you download the Stereoplay review (pdf available at Jamo site) of the Jamo R909 dipole speaker (two 15" woofers), you can see
they achieve about 84 db in the bass at most, with response extending to 20 Hz. Even this might be too optimistic as the
measurement conditions remain unknown. Mathematically calculated midrange sensitivity cannot be maintained throughout the low
frequency spectrum...

http://www.audiocircle.com/index.php?topic=60856.0

regards
miro

http://www.loudspeakers.we.bs/

[chakija]

As this topic is about amps, i have to reply my insight regarding bi-amp with one Alpha in my system.
Mid-high is oval alnico+motorola-like piezo tweet helper for >12KhZ ,and i estimate that they like 94-95db overall sensitivity. I run them through Aleph J clone-like amp, spawn Zen Mod, Babbelfish J .
Alpha was driven by Pioneer A757 amp (AB class,120W@4oms, dual transformers, inferior sound comparing to Babel ,but good enough for experiments).
Crossover on Alpha is Graham's T-bass, and inductor that makes ~6db/oct@2Khz+30uF for additional taming of the mid's.
When i run my A757 amp direct, without boost, i have completely incoherent sound with dreking alpha. Mid's that are coming from alpha's are really spoiling the whole sound and bass is not there at all. Than i tried to boost bass a little with tonal controls. Treble=min ,Bass=max ,+loudness .This boost gave different sound in terms of energy that is coming out of 15'' ,but when speaking of quality ,it is clear that pioneer cant compare with class A amp. HOWEVER ,overall sound was pretty good but even with this much boost on bass i had to turn up my volume much more than i expected in order to follow mid-highs, when listening little louder. On lower listening levels this difference is not so big.
I must add that i was very satisfied with sound of one alpha crossed and alnico FR running passive on class A amp, but now i doubt that i could turn back to that setup again because now i see that Alpha can give much more if driven with proper amp.
So , i guess that i will have to start building another class A amp (NP F5) for mid-high, buy another pair of alpha's and drive them with my Babbelfish through T-bass network and 12db/oct low-pass filter at ~150 HZ. Than i think that i will be completely satisfied with bass in my system.

[giamba76]

Hi guys,
Yes first post...

After several reading on OB pages, i build my own dipol speaker using 2 Alpha15a and 1 Ciare HX201 (similar to B200) each side in a baffle of 120cm tall and 88cm width, cut at 120hz passive.
I start to run my OB with a tube amp Yarland M34 with passive filters, surprised i miss the bass, probably depend on my room, depend of position wrong, but miss. I wait the time for breakin the drivers, but nothing! Change polarity, notihng!
Then i go for bi-amp the OB with my other little friend Yarland M84 (~15Wpc) only for the HX201 and the M34 (35Wpc) to the Alphas woofer, ok someting change, because now i have 2 volume controls and i can adjust more accurately, but i'm not so glad!!
Finally i decide to buy a Parametric EQ/ notch filter Beringer T1951 (vintage style) and an active cross-over Behringer CX2310 and adjustig in accordance to my ear, i have found the bass and the deepest bass...wow what a bass  i feel my shirt vibrate...
Just yesterday i add a little tweeter in the rear top cut with a 3.3 mF cap for to have more anbience...so i reach the paradise for my ears!!

I hope that my bad english can hepl someone... my source is the Advance acoustic MCD203mk2 tube cd player

Links: www.yarland.com / www.ciare.com

Cheers
Andrea G. 

[-Richard-]

Hi Chakija & giamba76 ~

Thanks for sharing your very interesting experiences experimenting with Alpha 15A's as your bass drivers in your Open Baffle speaker systems. I find your writing very informative.

It is not an exaggeration to suggest that using a simple double-driver configuration, a mid and a bass driver (or 2 Alpha's hooked up in parallel for more extended bass as in giamba76's case) for one's Open Baffle system can immediately let you know how well your amplifier can "do" bass... how effective it is.

I went through quite a few amplifiers before I found 2 that did bass adequately... without any augmentation to the drivers... Deb and I could live with them happily... but my present Sam Heathkit 151A grabs the bass frequencies and moulds them to the deepest most satisfying levels I have ever heard while still being articulate. That is one of the reasons I am writing about this amp so enthusiastically for Open Baffle speakers, with their natural cancellation issues (the slow moving back wave bass frequencies meet the slow moving front wave bass frequencies and they tend to cancel each other).

So one can say 'with an EQ boost my bass is now quite good'... and we are lucky that we have that as an option for Open Baffle speaker design applications... but it also tells us a great deal about how well our amplifiers are handling the need for powerful bass without any augmentation.

In the Golden Age of audio... the 1950's... many speakers were essentially set up as an Open Baffle designs... the baffles were often opened at the back... and rarely were there any fancy internal "chambers" that redirected the sound in order to boost the bass frequencies... so amplifiers had to have powerful bass augmentation in the form of tone controls that gave the music lover a level of control missing from most amplifiers currently being designed today... which was really a user friendly EQ.

If you want to hear how effective your amplifier is at doing bass effectively, try putting together a simple Open Baffle dual-driver system like mine or Chakija or giamba76... it may very well be an eye opener.

It is easy to suggest that as Open Baffle speakers become more "mainstream"... as a viable alternative to the usual dead-sounding (in comparison) speaker modalities currently being offered by the commercial speaker industry... that new amplifier circuit strategies will have to be innovated to allow Open Baffle speakers to play at their full potential... you will then see a return to the Golden Age of audio tube circuit designs. With a revised understanding of how to effectively use tube amplification circuits with tone controls, working in concert with Open Baffle speaker designers... it may no longer be necessary for Open Baffle speaker designers to resort to using complicated EQ electronics to "boost" frequency response.

We would then see a simplification of the design approach to designing great sounding Open Baffle speakers... as MJK/Martin already suggests.

I feel as if I am already living in that future.

Warmest Regards ~ Richard