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Hari's Open Baffle, Vintage single driver Russian speaker! Allison Kraus is in the house!



Well-Known Member
Jan 31, 2015
Hi everyone! So this is a review on Hari's system which consists of a DIY open baffle speaker. Hari was nice to have me over to his home where we listened to his system. Since I have never heard any of the components in his setup, this is more of a system review though certain characteristics are attributed to the OB speaker.

First of I must say that he has done a fantastic job at building a setup. It will easily outbeat any entry level setup. The choice of DIY DAC, 300B valve amps, cables etc. are a work of art because he has managed to put together a very nice setup using sweat and blood without having to spend silly money. When the power cable was noisy he put a ferrite ring on it. So he has built and tuned most of the setup himself without relying on buying so called 'high end' products.

System as configured:

1. Marantz 5001 CD player used as a transport
2. DIY DAC using BB1794 + AD827 opamp
3. Dared monoblocks with 2 x 12au7 drivers + 1 x 300B per amp with their own gain/ volume control. 6W amps.
4. Speakers as Hari has described (1950's driver!)
5. All DIY cabling using single core magnet wire.
6. Power cords with DIY ferrite rings

So now onto the review:

The dac which is basically a DIY kit from China is IMHO a star. The systems sound never got muddy or confused, nor did the soundstage collapse when the music got complex which I usually attribute to cheaper DACS. Nor did it sound extremely one note-ish.
The tube amps are 2 x 12AU7 + 1 x 300B mono blocks from Dared and they drove the speakers with aplomb.

When we first started, I felt that the bass response wasn't right nor were we getting enough weight in the mids. I felt that the lack in mid weight was due to some cancellation between the front and back wave of the driver as the driver, is closer to one edge of the baffle than the other. Hence we switched speakers around. After moving the speakers back and adjusting toe in, compensating for the lack of one side wall, etc. things fell into place. The aspect which we couldn't address completely was that the sound had a hard/ brash overtone to it which we later attributed to the tungsol 12au7s in the amp. Unfortunately I had only one set of RCA tubes which seemed to address this.
Hence all listening was done with the tungsol tubes.

Being a single driver speaker, the sound emanates absolutely freely, without your brain getting puzzled by two different drivers. It is like there is no stress to the brain and you want to listen to music. You have to listen to it to understand what I am trying to say. When you listen to a conventional 2 way speaker, there is always a little stress to the sound due to the crossover, two drivers having different material and profiles, etc. With a single driver speaker all this just disappears.

My rant on modern day systems:

Once again my feeling that people in the 1950s-1980s built music systems, where as we now build technology systems that are mainly about measurements and theory seemed true. This is why I hate it when John Atkinson measures equipment in Stereophile and then comments on how it isn't good engineering. He measures equipment reviewed by other reviewers mainly and yet comments on the measurements as if he is making equipment himself. The problem with this approach to reviewing is that it forces manufacturers to tune their systems to measure well, rather than to sound well so that Stereophile gives them a good review. I can understand measuring output power, impedence curves, input/ output impedence of electronics as these serve as guides for system matching but beyond that I think one diverges from the art.

Of course some people will disagree but this is how I feel:

If one wants a technically perfect system, just buy a Dynaudio studio monitor (active) and listen to it. It is matched to the amp to have enough drive and to be ruler flat and costs < Rs. 2L. One buys an audio setup to enjoy music, not to make measurements and yet we expect it to measure flat. The dynaudio will let you hear everything going on, but it is flat and devoid of any emotion. You will stop listening to music on it within 20 mins. I have tried it first hand. Even studio engineers will replay the music on a set of home/commercial/ TV/ car speakers (depending on where their music is going to be heard) to see how it would sound in the real world post mixing on their monitors.

Now back to Hari's system:

There is an ease to listening to the human voice with this speaker and you feel like listening on and on without worrying about what it lacks, which is how I described a level 3 setup elsewhere. No, this speaker doesn't and cannot extend into the upper highs nor can it go low and shake you. It is a single driver speaker which reproduces a fixed bandwidth, but does it pretty well, especially for a 1950's driver. The point
I am trying to make is that it lures you into the music by being simple rather than try and impress you with a particular frequency response.

You are not going to hear every instrument with this setup. You are not going to here someone coughing in the background. Your jaw will not drop either. What you do get is a very nice vocal, fully integrated (or should I say not disintegrated due to the single driver) with decent timing. Being open baffle you get a large sound and the speaker almost disappears. This is a speaker for the human voice, not for heavy rock music or techno.

I kept coming back to Allison Kraus, Louis Capart, etc. It makes you want to listen to the singer. You could almost get up and give a hug to Allison on some tracks. On other tracks like Peter, Paul and Mary's El Salvador the system showed it limitation. It just couldn't keep up with the fast guitar and high spl vocals.

1.A completely 'un-disintegrated' sound
2. Free, big and open sound, not confined into a box
3. Makes you want to listen and not worry about highs and lows and mids and people scratching their who knows what in the crowd in a smoky club
4. Easy to drive
5. Not a jaw dropping sound which is usually impressive at first but then gets tiring later on
6. Hari factored in everything. All wiring is simple magnet wire (single core). He has made an attempt to be a true audiophile on a budget. Instead of buying cheap speaker wire and then saying it sounds bad he addressed the problem by using a better option and yet sticking to his budget.
Kudos to him for that.

1. Will not suit all forms of music in the way people want to hear them. Blast Aerosmith on this speaker and the cone may come flying at you instead of Janie's gun.

2. Flat sounding in the lower mids (like a sudden lower mid suckout), little brash/ hard edge tone to the sound.
(though this was changed once we switched the 12au7 to RCAs. Unfortunately I didn't have enough tubes to switch both amps)

3. Got a little compressed/ confused on faster music like a fast acoustic guitar with vocals. Wasn't able to keep up with the strumming and vocals. Could be driver limitations. But its an old driver that was manufactured long ago and has been sitting around forever. Even grandpa needs a break!

4. Lacked height to the sound

I believe that you will not find a floorstander speaker below Rs. 70,000 with these positives, especially the ability to make you want to listen to music rather than focus on the attributes of sound. Infact I would go on to say that this setup will put most systems < Rs. 2L to shame.

If Hari can address the tonal hardness/brashness, lower mid weight and height aspect, then this is the speaker to beat below Rs. 1L on vocal music.

Infact I would push hifivision reviewers to go and review the speaker or system and support our DIY champ Hari. Sridhar time to visit Mumbai?
Vivek time to make a trip to Hari's home?

This system just goes to show us that one doesn't need big budgets, 300W amps or fancy multiple driver speakers to enjoy music.
A simple SET 6W amp, an ancient driver and a man with perseverance can easily put new age gimmicks to shame. If vocal music is your forte and you are on a budget, then this maybe the road for you to follow.
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Well-Known Member
Jul 31, 2014
If you ever travel to Jaipur, You are welcome to visit my place for a listening session to my 2 way OB with FRD running unfiltered by tube and 15" bass drivers by Solid State. I did some upgrades myself, driver stage tubes with RCA long black plate and a few others. Its a DHT pre driving the PP tube amp. After some 50 hours of break-in with new tubes, the setup surprisingly started handling ALL KIND of music with ease and amazingly so.

Its surely banging open the door to the "Audio Nirvana Land" and it does so with ease, from 17k down to 40Hz of prefect room response.

It would be fun to have you point out "Pros" and "Cons", since you already reviewed Hari's OB setup. I wish we could bring together our goodies at some common place and have great listening sessions and know each other.


Staff member
Dec 8, 2007
Very interesting suggestion Ravindra!
Start another thread on the topic and let's have our DIY gurus opinion on it.




Well-Known Member
Oct 26, 2014
Nice write up. looks like next weekend I might hop to Hari's place and listen.

Hari Iyer

Well-Known Member
Feb 8, 2010
Thanks Audiopro for such a detailed review. Appreciated.

1. Marantz CD-5400 CD player used as a transport

The magnetic wire suggestion for the speaker cable and interconnects were recommendation from FM Prem with whom i had a very interesting discussion couple of weeks ago. I extended his suggestion and went magnetic also inside my preamplifier internal wirings. Now i have to replace the preamplifier power supply internal wiring with magnetic wires. Also in the cards is to change the power amplifier internal wiring with magnetic wires. These mods will take some more time.

Also will plan change of the pre-driver tubes with RCA / GE tubes.

Also am planning a small wing on the smaller bafffle edge (on the backside) to prevent wave cancellation of frequencies from 922Hz below till 300Hz. Below 300Hz it will be dominated by other room resonance anyway.

PS: Attaching pdf file due to large size of the file.


  • OB speakers.pdf
    200.5 KB · Views: 26
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