[giamba76]

Thanks richard...
you say well...because you know whato you say, like Panomaniac and MJK, however, like in my case of first OB spesker, the position in the room is Very important, i think, more than the amp behind them.
At my home i notice also that i loss bass if i run them with the door opens (1 left and 1 rigth) or if you put next to the walls.
Yes the amp shown how it's good his frquency responce with this kind of speakers, but i think that you don't have any Eq or notch filter, is not possible to compare with bass reflex or other design in the bass region, when you are a newby on OB speakers, so you can say "oh sheet sound", but however the fistr song with my OB (yes little bass) was heard in e new strange way...like omnidirecional sound...!
Is difficult to explain in english (i'm italian...)
Cheers

[-Richard-]

Hi giamba76 ~

That is a perfect description of the Open Baffle "sound field":

"...like omni-directional sound..."

With Open Baffles there is no need for a multi-channel setup... which is yet another attempt to overcome the inherent severely limited directionality of almost all box speakers... necessitating the so-called "sweet spot"... which is simply a nice way of saying, poor off-axis integration. Deborah was lying on the couch yesterday for a little rest and noted "the music still sounds fantastic and it still sounds like it is coming from the center of the speakers...". Deb was about 5 feet away to the right of the right hand baffle.

Honestly, giamba76, I do not notice quite the same placement anomalies that you and many Open Baffle explorers seem to experience. Admittedly, there seems to be a "minimum" distance apart for both baffles... in my case about 6 feet apart and toed-in about 9 inches with the inside edge of both baffles only 2 feet from the back wall... where voices and the music become entirely independent of the speakers and penetrate the sound space as you describe so beautifully... as omi-directional.

I have read posts on AC of the phenomena of bass frequencies disappearing when certain physical conditions of the room are altered... what I have found in my own experience is that there seems to be less interaction with the elements of the room with the combined front and rear sound waves... than occurs with just the front wave of a box speaker... it could be that the rear wave disperses in a more open pattern... overcoming some reflection issues.

Yes... bass reflex and other box speaker designs do help to enlarge the bass frequencies... but I find that bass reflex designs sound artificial now that my ear has accustomed itself to the highly articulate "natural" bass response of my Open Baffle speakers.

Dr. Dan Mason used to say "once the ear gets used to the natural sound of Open Baffle speakers there is no going back to boxed speakers!". He was right!!

Glad to hear that you are having so much fun with your Open Baffle speakers, giamba76.

With Warmest Regards ~ Richard

[ezr]

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
hello
 i am useing  quad classic ll an old 2 mono block  with my  open  baffle (altec 605)  and i like to know  if  quad  34 pre- amp  can  mathing  the ampl 

regards  ezra

[-Richard-]

Hi Ezra ~

Somehow your post seems to be attached to the bottom of my initial post when it was placed in the "blue" quote box.

I think your post is meant to read like this:

"hello- i am using a quad classic ll, an old monoblock amplifier with my open baffle speakers (altec 605), and i would like to know if a quad 34 pre-amp is a good match for the amp?
regards  ezra"

I have no experience with your particular equipment... however, perhaps someone in our OB community with experience with your equipment can respond to your question. Good luck, ezra.

Incidentally, what are you currently using as a preamp?

Warmest Regards ~ Richard

[panomaniac]

Thanks Richard - I couldn't figure out that post. Glad you did!

[dmiller]

Thank you Richard for the recommendation to Sam. I've had a email conversation with Steve and will probably call him later in the week.
I'm curious, what's your usual source material? Vinyl, CD? do you listen to  Jazz, Classical? I can be helpful when reading subjective opinions to have an idea of the complete setup. Thanks

The way I play music and power speakers I would not use tubes for O.B., but I sure would for corner BLH. For budget it seems a 3870 based gainclone is perfect. I'm about to build my first gainclone kit. It's great that with a few carpentry skills, $200 in drivers, and a $150 gain clone, a person can build a wonderful system.

Concerning driving 15 inch base units in OB. Driving 2 in serial at 2 ohms, no downstream crossover, and a better pro amp meets the designer's intent. For dynamics and control of the woofers' motion I expect many much more expensive amps do worse. When it comes to dynamics, there are advantages to driving 3 watts continuous with 300w amp/channel. Lower power amps now approach clipping more gracefully, but that's not the same as having good control over the large surface area of two 15 inch drivers. With bi/tri amping there are many good choices for the easier to drive channels.