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Open Baffle Epiphany!

Wes_in_VA said:
So Decware claims that the SE84 matches best with 4ohm speakers and from the messing around I've done, that sounds feasible. With the OB's I'm running (which are 4ohm) so far the little Zen seems to have plenty of juice and is actually less strident than the Legacy ss amp I initially tried with them.
I wonder if your experience with the Zen and your Cornwalls is more evidence that maybe that 4ohm match makes sense?

EDIT: BTW, not trying to derail the thread. Sorry for the slight detour into a discussion my Zen.
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Dunno -- my 1974 Cornies were, I think, nominal 8 ohm loads (not 4). At low-ish volumes, it sounded pretty good with the Cornies but a pair of Bottlehead Paramours bettered it considerably even with generic Chinese 2A3s. Best I ever heard my own Cornies sound was being driven with a Marantz 8B (they sounded pretty good with a Fisher 500C, too).

I do know we tried the SE-84B with a pair of 15 ohm Lowthers once and the din was horrific (even compared to the usual screech of classic Lowthers).
 
If there was such a thing as screech Lowther's rolled whizzer cones fixed that early this century.

One carrot of the Lowther is their large dynamic contrast, i.e. the ability to go suddenly from very soft to very loud and back again without congestion. With the Bottleheads even at low levels the Lowthers startle the crap out of me.

I've tried so many FR drivers in OB but none have come close to the DX3's. I'd bet MJK might say the same for his Lowthers. The company's marketing slogan is "Lowthers For Life" and after owning a pair for the past two years I get it.
 
That may be -- I haven't heard any of the newest Lowther offerings.

The classic "PM" Lowthers could sound scarily real with excellent program material, but they didn't fare well with heavily processed "pop" recordings IME (i.e., "multi-track mono mixed to artificial stereo" -- as is essentially the rule with pop music, and even some 'classical' music recordings).
 
Wes_in_VA said:
So Decware claims that the SE84 matches best with 4ohm speakers and from the messing around I've done, that sounds feasible. With the OB's I'm running (which are 4ohm) so far the little Zen seems to have plenty of juice and is actually less strident than the Legacy ss amp I initially tried with them.
I wonder if your experience with the Zen and your Cornwalls is more evidence that maybe that 4ohm match makes sense?

EDIT: BTW, not trying to derail the thread. Sorry for the slight detour into a discussion my Zen.
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I don't know.
It seems that little side excursions into amplification is fair game when when the topic is OB.
SET is certainly very nice with HE drivers in OB.
My experience with a 300b set amp was very good.

Things really changed though (for the better) when a 300b amp in push-pull configuration was introduced into my system.
All the mid-range goodness plus better extension at both ends.
Most notably the bottom end extension on OB.

However the 300b SET manages to dig pretty deep and sound really great when matched up with with a pair of 4ohm Revox speakers.

Man oh man, that mhardy really knows his stuff doesn't he.

EDIT
With the OB's I have also used a pair of modded Akai M8 mono blocks (6bq5 single ended pentnode) which put out about 3.5 wpc.
A terrific combination.
SECOND EDIT: 6BQ5 = EL84

Art
 
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I run my Omega Super 3R full range drivers with the Zen amp and loved it. I didn't think it would posible get better until I put in a lo mu 6sn7 tube pre amp. Just that little bit of gain really increased the detail, range, dynamics, openness. Everything got better.
 
The DX series still has the characteristic lowther frequency response mountain right around 10khz, but they do a nicer job off axis then the PM series. Listening to them at 30 degrees off axis really tames the peak. On axis, without accounting for it in other ways, it can make for an unnatural high end, but does give the illusion of higher frequency extension than what is really present. The PM series, IIRC, didn't handle the off axis stuff quite as well as the DX drivers. The only situation where I found the PM6 truly useful was in a nice 3 way system as a very high efficiency system. I'd say the DX3 is the best lowther I've heard by quite a bit, and set up properly, it can be quite good. Like most high efficiency drivers, it's low power compression is noticeable, I think PG named it "dynamic contrast". It's not a term I'm familiar with, but the description seems to fit the "low power compression" definition, quite well.
 
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A guy in nearby Augusta builds/sells these C-horns with the DX3's. Gorgeous horns with stunning clarity but as you might expect they lack the bass of woofer assisted OB's.


CHorn.jpg
 
PioneerGuy75 said:
Getting ready to do OB project here real soon...
Ill keep you posted!
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I'd suggest you start your own build thread in the DIY Forum. You will get a lot of help and support if needed. You will also be helping others who might be thinking about building OBs. Good luck.

cubdog
 
Poultrygeist said:
A guy in nearby Augusta builds/sells these C-horns with the DX3's. Gorgeous horns with stunning clarity but as you might expect they lack the bass of woofer assisted OB's.


CHorn.jpg
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Very interesting look. Even though I like the very modern and the unusual in speaker design I'm not sold on the plexi. Still, I like them better than most old box designs and I'm pretty sure I'd like their sound better than most box speakers.

cubdog
 
I jist gone semi-OB'd.

KakaoTalk_20140907_185532752_zps867e7e77.jpg


I'm reserving my judgment yet, but my wife likes this better.

I was told that I'd need subs for the bass reinforcement, but the bass quite plentiful already. I am listening to Schoenberg verklarte nacht as I type.

The cabs are bottom-ported and the port is pretty large - more of a void really.
 
davidro said:
I jist gone semi-OB'd.

I'm reserving my judgment yet, but my wife likes this better.

I was told that I'd need subs for the bass reinforcement, but the bass quite plentiful already. I am listening to Schoenberg verklarte nacht as I type.

The cabs are bottom-ported and the port is pretty large - more of a void really.
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Tell us more !

Judgement! We love judgement....
 
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Ok a few days passed by, and i like this setup very much. I like the type of sound that's big, wide, deep & natural - as if you're in an actual concert hall.

This semi OB achieves that like no other. My wife says it sounds as though we're in a much bigger room.

The sound doesn't sound as though it's shooting out from the speakers. It sounds as though it's spreading around from the speakers, like how actual instruments sound.

The previous owner of the drivers and the gent who helped me enlarging the baffle hole commented that I'd need subs to have good bass. Well perhaps due to this being semi OB or the speakers being cornered the bass is pretty deep, big and natural. But i might sti tinker with DB to fine tune the lowest notes.

I was a little worried the sound will have that church hollowing character with OB, but there's still the focus for good imaging. Good mid range too. Not like some omni type stuff like Bose 901.

I'm also considering adding sime simple bracing in the cabs as an experiment. Perhaps a few pine timber slabs? Might also try some padding inside. Perhaps the high will have a bit more air that way.


Sent from my X10a using Tapatalk 2
 
Glad to hear you like it, David. What you have doesn't have any of the benefits of a dipole like others here enjoy, but that doesn't mean it can't perform well. I think DB would only help.
 
davidro said:
So it's nothing like an OB at all?
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Hi David. Dipoles are a specific type of OB. They have some benefits with reducing the impact of the room on the sound. They aren't ideal, but they sure beat a monopole. Your enclosure will impact the back wave differently then the front reducing some of the benefits of a true dipole. It's hard to predict the exact impact but I'm not surprised that the bass you were originally was better than you anticipated.
 
Yeah i didn't think itd be the same but i thought i was getting at least some of that backwave.

Sent from my X10a using Tapatalk 2
 
Oh, you do, there will be some cancellation at low frequencies, but the response probably more closely resembles a cardioid pattern like you'd get from a U-frame.
 
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