Unitron Speakers

Unitron speakers? Huh? An easy thrift store pass by..... It is what is in the box that the treasures can be found.

This pair caught my eye as the cabinets are in pretty good shape and made of real wood veneer, they do need a bit of sanding and new polish, that is easy work.

I opened these up and found a 10" Coral woofer and Coral Alnico tweeter, I figure the cabinets and the drivers were well worth the low low asking price.

My plan was to find a new home for some 10" Foster Alnico woofers and a tweeter of some sort, these boxes would fit the bill.

 I got these home and listed to them with the Coral's in them, boomy, boxy sound was all I heard. The Q's are too high from the woofer for this box. I pulled them out and inserted the Foster 10" Alnico woofer and a Radio Shack 4" Alnico full range speaker, crossed over with a simple 22uf cap around 900hz. Now these speakers sound delightful, like amazingly delightful.

 

Like amazingly delightful, I am going to do more finishing work on them but I have them up and running and I like what I hear.

I mounted the Corals on a spare baffle board that I had around and gave these a listen....OMG these on a baffle are a completely different speaker. Super efficient, the high Q's add beautiful sounding bass for its size of the woofer and the mids and highs are dreamy delicious. Just as I suspected.

New baffles will be made for these and I will offer them up for sale in the near future.

Next Open Baffle Project: Akai/Foster 12" woofers with Foster FE-103 4" clone full range

My next open baffle project will be this Akai/Foster 12" woofer matched up with a JMI Japanese Machinery and Metals 4" full range speaker.

The JMI full range resembles a Foster FE-103 speaker in every fashion. The JMI and Akai are both ferrite magnet speakers. Presently I have them set up on a temporary baffle until I make some new baffles. I am running both speakers without a crossover, relying on their natural roll off, so far this combination is the one I like the best out of the three I tried today.

Of course the finished product will not look like this, this was just a temporary set up to get an idea of matching the speakers and the sound.

I tried these 4" alnico full range also and found I needed to croos them over with a 15uf capacitor, still the 4" speakers shouted louder than the woofer and the bass was mismatched to the woofer output.

Last I tried a pair of Foster FE-163 speakers, these too were much more efficient than the 12" woofers and sounded unbalanced. I think the Foster Fe-163 will saved for a back horn loaded speaker build in the future.

The Journey to Open Baffles and Tube Amps

This blog is a journey into the wonders of hi fidelity. As I travel this path it opens up more and more.

My first memories of hi fi was my dads dynaco tube amp that he built with a pair of AR3 speakers. He had a cassette deck and I used to listen to Simon and Garfunkel Bridge Over troubled Waters over and over through a set of headphones.

My first real stereo was a JVC PC-11, half boom box half component stereo. It was around 20WPC and was pretty cool at the time.

Later I bought a Pioneer turntable to go with this system.

My first set of speakers was a pair of Mission 700S and  we had that connected to a JVC JR-S301 and then some sort of Sansui amp. Both the JVC and the Sansui were great at frying the Vifa tweeters in my missions at that time. Heavy fingers on the volume.

My first decent receiver was a Harmon Kardon HK 380i, a step up in sound and lots of head room. I stopped blowing tweeters.

Next came a Rotel RA-840B amp that ran 40WPC, I chose this over the AR Cambrige A60, although in retro spec I should have bought the AR.I had the Rotel for many years and just recently sold it in the past couple of years.

My next great pair of speakers was a pair of Energy 22's which I had for at least 20 years of which has seen some time on this blog.

It was the first tube amp that really sent me down the rabbit hole. The fidelity you get from 1 or 2 watts per channel can put the biggest monster receivers to shame.

Since being bitten by the tube bug, I have not really cared for solid state stuff and pretty much pass over most of it unless there is an end game for the stuff I pick up.

The tube amp has opened the door to speakers and their design.

In my journey I have found that the early well designed speakers from KLH or EPI with minimal crossovers are the best, after all in is signal in and signal out. Keeping the path of least resistance is the key.

When running a tube amp, speakers need to be over 90db in efficiency and the higher the better.
Another thing I found is horns in the mid range and tweeters give incredible clarity of which paper or domes can not. Some can come close.

Now I am finding that open baffle speakers are really clean in sound and the reason speaker were ever put in a box was to make them a piece of furniture that a wife could like. The bass in an open baffle is really clean as if the box imparts plenty of resonance, colouration and a myriad of other problems.

Open Baffles need a special room or space to work properly. A few things I have discovered in the open baffles is Alnico drivers work best, minimum of a 10" woofer is needed, a 3-5" full range is optimal for the mid range, preferably open in the back to get the proper refraction. I tend to like a horn tweeter to top the music off.

Of the open baffles that I have built to date this Foster Open Baffle is stunning in its' sound. I had to tame the tweeter down a bit with a resistor. The little Foster 8F3 full range is spectacular, a massive open sound stage is presented while the bass is really articulate, tight and clean with the 25E33.

So as the journey continues I have decided to sell off many of my boxed speakers and will concentrate on building what I think from my ears and years of experience some vintage cool efficient open baffles.

Stay tuned I have about six unique designs in my head and the drivers to create the path into this wonderful hobby.

I leave you some things to read and ponder.

Linkwitz Lab conclusion on OB versus box speakers.

Hawthorne Audio on the Art and Science of Open Baffle speakers.

Speaker Projects.

Good luck on your journey and I hope if you read this far try a tube amp some day and if you get the chance a really nice pair of open baffles.

Foster Open Baffle Speakers

The latest open baffle speakers I have put together is a 3 way Foster driver speakers. The donor driver came from a pair of Noresco NEC-571  plus a horn tweeter that I picked up from a set of Zenith Allegro speakers.

This project turned out to be spectacular with the push/pull tube amp, almost in the league of openness and fullness as the Speakerlab Super 7's, almost. The Super 7's are really an amazing loudspeaker.

 The original Noresco speakers used a 10" Foster 25E33 alnico woofer with a massive magnet assembly crossed over to the Foster 8F3 three inch full range speaker. The original crossover was used as the crossover point between the woofer and the full range driver is around 650hz.

A foster horn tweeter was included to handle the high end as I found the 8F3 seemed to roll off in the highs.
A 2.2uf cap was used with a crossover point at 9000hz, it seems to have added the high end depth and sizzle that I like.

This combination came out way better than expected. Bass is full and clear, the mid range from the 8F3 is luscious and smooth, very deep and wide. the horn tweeter takes care of the highs in spectacular fashion.

Before I started this project I had an idea as to how this set up would sound, but it came out way better than I expected.

If this is what open baffles are supposed to sound like, then I am a believer now.

Aesthetics came out beautifully with the dark mahogany veneer.