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Thursday, April 20, 2017

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.

Realistic Minimus 1 Speakers

Another pair of speakers that I picked up today is this set of Realistic Minimus 1. Realistic used really nice Foster/Fostex driver in the early days. This pair uses a 5"alnico full range driver and a nice cone tweeter.






This pair will be cannibalized for their driver and put into an open baffle system.

Coral 10L-17 Woofers

I picked up this set of Coral 10L-17 woofers today in mint condition. These 10 inch units will be used in a future open baffle project. Older Alnico woofers tend to be really efficient and have really nice bass tone.



I have discovered that Coral's, Foster and Fostex drivers are really efficient and work really well in open baffles.

Wednesday, April 12, 2017

Akai/Foster Open Baffles

Last week I picked up this pair of Akai SW-135 speakers that has Akai branded Foster driver in them.
In the original box these speakers are not much to listen to, in fact they are boxy and not to open on the sound stage.



I promptly removed the drivers and went down to Makers Lab to start my project.


This is the finished product and I think this forth rendition of my open baffle experiment turned out really well.



Once again with open baffles there is a really open sound stage, the three drivers are all designed to work together with minimal crossover which is a 16uf cap for the mid range and a 2.2uf cap for the tweeter.

Bass is exceptionally strong, tight and articulate in these speakers, mid range is nice and smooth and the highs are perfect for a cone tweeter, not as strong as in the horn tweeters.

Best suited with a single ended tube amp versus the push pull tube amp. I am going to keep an eye out for the vintage Akai speakers as they can be had for next to nothing and they have really good alnico drivers in them.

Tuesday, April 4, 2017

Next open baffle project Akai SW-135 Speakers

Just picked up this pair of Akai SW-135 speakers for the next open baffle project. These seem to have Foster or Coral Alnico drivers, perfect for open baffles.

The cabinets have been gutted and speakers are in perfect condition.




Saturday, April 1, 2017

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.

Sunday, March 26, 2017

12" Utah Pandore Open Baffles

Another project finished this week is the Open Baffled 12" Utah Pandore speakers.






More bass than the 8" Realistic Americana Open Baffle speakers that I did 2 weeks ago, there is also a compression horn driver for the highs.

these speakers sound very natural and I do not miss the boxed bass that are part of every other speaker.

The results of this project came out much better than my expectations. I am pleased as punch with theses speakers and will most likely keep with the 12" open baffle designs. Although I still have a few 8" coaxial driver that will be featured soon.

And of course these are being driven by a SET tube amp.

Very impressed....