SE 300B and Folded Horn Fullrange Speakers

[alexc]

Hi - just wanted to ask if anyone else has gone down the

.......'SE 300B and Horn Loaded Fullrange Speakers'..... path

I'm just deciding my my next 'project' in the way of stereo tube amp and speakers 

Same old 'PP' or 'SE' thing I go thru everytime! 

Right now, I'm leaning again to the SE side; 5 honest watts  ..  and with some diy loaded transmission line jobbies. With Nice Timber  :'(  SO very cool.

..  Ah, choices!

My trusty old  single tube SE 6L6 with 70s Realistic speakers is making me wax tearfully lyrical on SE and high sensitivity speakers.

I'm thinking to get some local woodworking talent to cut some nice Tasmanian Blackwood and have a stab at assembling one of the Fostex fullrange public domain designs.

So - looks like my next project is in play.  Some single 300B and Fostex  for me 

I'm really getting to the point where I need a dedicated 'listening' room - nothing crazy, but done as best as possible for ... listening. (and solo performer recording)

On a clear day here, 5W - real, soulful watts  goes a long way

These guys aren't shy of 'neighing' their opinions  ...

 

[emrr]

The bigger Fostex look interesting, I haven't heard them.  I guess it depends on how much of a junkie you are for low end.  I run a pair of Klipsch La Scala with new drivers and crossover, an earlier simpler crossover design.  They are in the range of 105dB/1W/1M and with a 15" woofer really move some air.  They are big.  3' x 2' x 2'.  Gotta have size for bass in a horn.  Even with that size they typically need some bass boost to balance well.  If I had room for Klipschorn's I'd be looking.  I can run them to earsplitting levels with a 10W tube amp. 

I have heard very nice multi-driver full range systems.  It's worth looking around at all the crazy things people are building on that front.  If you stick to 5Wish power you have lots of options.  I think you can find Klipsch plans, you could consider building La Scala/etc bottoms run full range with something else on top to finish the picture.  The industrial line La Scala were made for awhile with tops and bottoms separate, it could be worth looking for a pair of those bottoms from a PA company or nightclub, use as a foundation.  The cool thing about that version is you could aim them properly into room corners to achieve something closer to Klipschorn bass range, and aim the tops as needed. 

The SE 300B amps I've heard have been fun to listen to.  It's been quite awhile since I've heard one, and I haven't heard any real side by side comparisons. 

 

[alexc]

I've some reading to do regarding the Klipsch - the Audio Cyclopaedia has some sections on the Klipschorn.

I also really like the Karlson enclosure is also interesting - wonderful aesthetics.

 

[alexc]

But yes - staying with the fullrange config, and a single driver, for now 

The Fostex 8" are interesting and ones catching my fancy are the Audio Nirvana drivers.

Sounds like a 12" full range with a 100dB sensitivity could be fun  8)

Kind of negates the need for them fancy folded horn loaded boxes!

This is sort of thing I'd like - maybe a 10" full range driver.

I'm building a parallel triode-mode SE amp in the 160mA current range, at present. It's an attractive sound.

So - decisions, decisions.

Single tube SE or parallel tube SE ?
How much 'juice' ?
How big of a driver ?

and of course - what cash?

At least, now, I cost in a set of what I consider appropriate speakers for any new tube amp build. Kind of 'honest accounting in tubefoolery' 

I'm seeing  a project the dangest sound I can conflate , for 1Kaud speakers and 1Kaud for the 2 amp channels.

That's pretty reasonable and I think I can do an interesting thing for that kind of 'dough'.

----

So - local timber, a pair of 10" mid-cost Audio Nirvana drivers and no crossover.

Cabinet likely to be a folding horn, rear loaded, big for a 10" driver.

Amp most likely using parallel low cost driver tube with SE at around 125mA or so per channel giving around 8Wrms or so.

I start the process now, and 2years hence - bingo, a real class setup.

 

[fazer]

Good luck Alex,  With all your builds, I'm sure this will prove to be a success.  I would love to have a 300b SE amp.  Audio Note use to make a really good kit.

Recently I wanted to hook up my La Scala's.  Only thing is the La Scala's have such a long throw.  You want to be back like 20 feet from them, or at least I do.  You need a big room for them to breath.  I hooked them up recently to test them and was going to sell them,  Then I was liking the sound so much I could not part with them.    I need an audio intervention . 

Emrr:  what is the crossover you switched too?    I always liked the sound of the oil caps in the crossover of the La Scalla.    It had a smoothing effect on the bite of the horn.

 

[emrr]

I hadn't seen the Audio Nirvana drivers, they look interesting too.  It appears there are enough 'full range' products out there at 'non-collector' cost to reload or recreate various vintage speaker systems. 

I did the full Bob Crites modernization, and even hacked the horn mounts to the front of the boxes to get rid of the last bit of diffraction from the box, so they sound cleaner further off axis.  New CT-125 tweeter type, his A4500 crossover that is optimized for that tweeter, his woofers, original K-55-V mid drivers (supposed best version).  I wouldn't go back to the original tweeter after hearing his new ones, new is much more extended and clear. 

http://www.critesspeakers.com/bk-sound-type-a4500-crossov.html
http://www.critesspeakers.com/klipsch_tweeters.html

I'm in a small room, and throw isn't a huge problem for me.  I can sit between them within 5 feet for quiet listening and have a great experience.  They sound loud and huge at very low volume.  Bass sensitivity is such that I have a few EQ curves I move between depending on the source, to get best bass balance. 

Efficiency is such that I can hit the threshold of pain with 10W, no sign of driver or box distortion like all my other small box speakers do long before my ears hurt. 

 

[fazer]

Sorry to Hijack alex. 

EMRR:  Crossover shift to 4500 and new 125 tweeter  makes since.  I have some 2015 plans now. 

 

[fazer]

The Cornscala look like a good build also from Crites.

http://www.critesspeakers.com/cornscala.html

 

[emrr]

Any and all first range reports on various modern full range folded horn systems are welcome!  I am curious. 

 

[letterbeacon]

I keep threatening to build a couple SE 300B monoblocks, but the flat I live in is far too small for the size of the speakers needed for them 

I might have to settle on a high power push pull circuit... or get a bigger flat.

 

[alexc]

Any and all discussion on crazy big speakers, crazy inefficient SE amps and such is all good

The Klipsch La Scala IS the biz!  What a beautiful and properly sized enclosure 

I have to look into them some more. Here's some 'Heritage' series info :

The Heritage Series La Scala three-way loudspeaker provides a very Klipschorn®-like performance with sparkling highs; extreme output yet smooth midrange; and the unsurpassed low distortion bass response of the patented Klipsch folded-horn woofer. Utilising the same horn-loaded drivers used in the Klipschorn® and Belle Klipsch the La Scala is highly efficient and can produce high volumes with very little power and undetectable distortion.

    Highly efficient: 105 dB 1W / 1M
    Fully horn-loaded three-way system
        folded-horn 15" woofer
        2" midrange
        1" tweeter compression driver
    Traditional "utility" plywood construction and finish

 

[emrr]

Letterbeacon, you won't need speakers so giant and efficient in a small flat, as I'm guessing your neighbors might chase you out if you really put them to work.  Do the 300B amp (or similar) and use what you can!

I still think the La Scala bottom run full range with a smaller full range on top might really be pretty great.  Aim the bottoms in a corner as the Klipschorns are meant to do. 

Some fancy restorations showing a La Scala with some Klipschorns.  You can imagine the top and bottom of the La Scala being separate pieces, I can't find a good pic of the industrial version. 

Or heck, watch for a pair of Klipschorns locally, you might be surprised.  They frequently sell reasonably because no one wants to move or ship them.    Somewhat true of la Scala as well. 

 

[alexc]

My word!!

Such beautiful pieces. So, so wonderful 

I can imagine some choice USA tube amplifiers that would blow my mind.

GE, Altec , RCA and of course the Western and Northern Electrics ....
Probably Surely many more.

Gosh.

 

[alexc]

I do like the 'point source' idea - my main 'studio' (music room!) monitors are Tannoy System 8.

(that's smallish volume ported cabinet, coaxial speaker with internal crossover network (bi-wirable).

Now that speaker, 'coaxial' rather than 'fullrange' (apparently) is pretty good.
The bottom end is there but takes some serious power to move them.
I would think they are in the 86dB type sensitivity with a typical power of 30Wrms or so in use.

HENCE, the desire for something 'similar' in philosophy but of the higher sensitivity camp.
ie. a 12Wrms typical power level and work for the best I can do there

-  full but balanced bass, wonderful mid and hi's that don't irritate my mid-life ears 

SO - resolved now to the Audio Nirvana driver. Resolved on SE.

Yet To Decide

Still tossing up a standard ported cab or a crazy ass cabinet config

Still tossing up single tube final or parallel tube finals in the SE config.
I should go lower and stay with a single tube  - the  (real) 5W  option.

But the caveman in me just can't say no to 12W  8) 8) - so probably parallel SE tubes.
WHich is great. I have a single 6L6 SE stereo amp.
My 'most used'. It's probably 4Wrms max.  (65mA at 350V for 22W quiescent - 70s RCAs )

And of course, the output traffo choice. AM thinking seriously of  ElectraPrint.

http://www.electra-print.com/singleended.php


( I am not affiliated with any of these fine companies    )


So - parallel SET, horn loaded single Audio Nirvana drivers no crossovers, nice timber

If at all possible, a 'double throat horn' jobbie, run at 10Wrms for LOUD.
But more likely, just a largish ported 12" box  :'(

Still - not so bad.

 

[alexc]

like these ....

 

[alexc]

or the simpler version single port

 

[alexc]

Amp looking something like this 

But with seperate power supply unit cabled to the amp unit.

 

[alexc]

One thing is for sure.

This time, I WILL use a choke plate load in the driver circuit.
That's my main reason for doing a SE again.

Does it make a difference over a simple 5c resistor for a plate load.

Like the guy said 'only one way to find out'.

 

[alexc]

If I don't go for a single 300B (or even a pair!) then I'll go with parallel, low cost triodes

Like this ...

I'm thinking 5x 6S4A triodes - for 125mA of bias dc  per channel ay 250Vdc and some in reserve.

Miniscule output Z,  driving a relatively low primary Z of 2.5Kohms or so.
(Unfortunately however, the parallel'd input capacitance does add up)

This one, with the happy 6S4A at a modest 250V, has some hv volts to spare - so cathode bias this time.

..

At the end of the day, I still have that decision to make - a great 5W or really good 10W amp.

Of course, I can delay that decision till the end : I'll make the speakers first, try them out with my existing amps to get a feel for what's what with the speaker - then make the amp build decision.

SO - off to get some wood 

Summer time here in the southern tas fields (of australia) is the time for wood work.

 

[alexc]

like this builder ... Sachiko ..