[Bob in St. Louis]

I would also recommend a good SS amp for the Lowthers.

Really!?!? I don't hear that very often.

[MJK]

I would also recommend a good SS amp for the Lowthers.

Really!?!? I don't hear that very often.

Yup ..... really. It is totally politically incorrect and I have been shunned by the Lowther purists and gurus.

So I will repeat myself one more time just so everybody knows my totally unacceptable position.

I USE A 200 WATT SS AMP AND A SS PREAMP (probably considered mid-fi by most) TO DRIVE MY LOWTHERS AND I LOVE THE RESULTS!

In my opinion there are a lot more options available for designing a full range speaker system using a SS amp compared to a low powered low damping factor tube amp. I do not believe that the resulting sound using a SS amp will be compromised or inferior. The couple of die hard tube people I know who have heard my system over the years have not complained much other then on principle alone.

Martin (the Heretic)

[opnly bafld]

Martin (the Heretic)

 

[ttan98]

In the past I use valve amplifier to drive my speakers.

But now I use very effcient speakers and drive them using Chipamps, in biamp or tri-amp config.  I am very happy with the Sound.
 
With global warming I think we need to use efficient appliances, Valve amp. is not one of them.

[Mr Content]

I agree with you Martin. I myself use a class A 120w amp to drive my B200's, realising over time that tube amps did not have the control and drive in the bass that was needed for my setup. It also has a very relaxed and open delivery as compared to low wattage tube amps.

Mr C

[Bob in St. Louis]

Ok, looks like we've got some amps. Lots to choose from there Alex. Now we need to figure out where you want the DX2 mounted in the baffle. You're on your own regarding the crossover network though. One of the experts can build that one. Building custom XO's is new territory for me.

Regarding SS vs Tubes=
I see how it is..... ......You guys finally get me over to the dark side and force me to buy tube amps, than you all "change you mind" and go back to solid state.
What's up with that? 

Bob

[sts9fan]

I would also recommend a good SS amp for the Lowthers.

  Really!?!? I don't hear that very often.


Yup ..... really. It is totally politically incorrect and I have been shunned by the Lowther purists and gurus.

Its not that odd.  Mr Pass has used his F3 to drive the Lowthers in his open baffle active speaker that uses Seas bass drivers.  Plus The dude from Lowther is a big First Watt fan.

[Mr Content]

.

Regarding SS vs Tubes=
I see how it is..... ......You guys finally get me over to the dark side and force me to buy tube amps, than you all "change you mind" and go back to solid state.
What's up with that? 

Bob

Comeon Bob, who would have urged you to get some glass glowing in your system???? I still like a nice tube pre, but so far I havn't heard a tube amp hold a candle to my SS in my system. Well not a lite candle anyway.


Mr C

[Bob in St. Louis]

Comeon Bob, who would have urged you to get some glass glowing in your system????

Everybody on Decware. Mainly Dave (HurdyGurdy), Bob Pace(troutsnook), Steve Deckert, Bob(Zygi), Rap, etc.....
(The first forum I joined years ago {when I was young, and impressionable} and my introduction into "first watt" theory). 
And more recently, all the St. Louis AudioCircle guys. 

Peer pressure WORKS. 

Bob

[opnly bafld]

Bob, don't forget the guy that loaned you a broken Almarro for 5 months. 

Lin

[TerryO]

I would also recommend a good SS amp for the Lowthers.

  Really!?!? I don't hear that very often.


Yup ..... really. It is totally politically incorrect and I have been shunned by the Lowther purists and gurus.

Its not that odd.  Mr Pass has used his F3 to drive the Lowthers in his open baffle active speaker that uses Seas bass drivers.  Plus The dude from Lowther is a big First Watt fan.

Nelson Pass has, over the years, been trying to achieve the "sound" of a good single ended design with little or no negative feedback. He has admitted that tubes can sound very good and a SET is just about the perfect configuration for those requirements, with the exception of power. Triodes are the most linear device yet conceived while transistors usually require copious amounts of NFB to achieve linearity and their vanishingly small amounts of Total Harmonic Distortion (THD). If the THD figures equated to good sound, then all would be right with the world, but it seems that this isn't the case as tubes have many times the THD as most SS amp and yet...
Nelson Pass has been advocating reduction in NFB, especially Global Feedback, as a key to better (more tube-like?) sound. Coupled with reduction in the number of gain stages (he's down to one stage on the recent designs) he seems to have achieved significant sonic advances with his First-Watt designs.

Tubes have been commonly faulted as having "flabby, out of control bass" and critics have been quick to point out that tubes, especially SETs have very low Damping Factors, often under 20, while SS has numbers into the many 100's.
As the Damping Factor of a SS amp is almost always derived from high levels of negative feedback, we start to see this "number" is a "byproduct" of NFB and isn't actually or necessarily a bonus. Tubes with their output transformers can almost always achieve a half octave of bass extention over most transistor designs... if the impedance of the speaker is fairly flat. This is easy to test by installing a 2 or 3 ohm power resistor in series between your SS amp and the speaker's positive input terminal. The resistor will lower the effective damping factor of the amp as seen by the speaker and you will probably gain some bass extension. Many of the best speaker designers (Greg Monfort for example), when doing a custom design will ask if you're planning on using tubes, as they take that into consideration in the overall design plan. Where tubes run into problems is with wild, fluctuating impedance curves. Please note that it's the curve that's important, not just a static number summarizing the whole complex impedance variations. As a lot of speakers are voiced using SS amps, the impedance curve tends to be forgotten as it really isn't as big an issue as it is with a tube amp. It's no wonder that tubes sound bad in many systems, as they have to contend with circumstances that are not congenial and should have been taken into consideration during the speaker design process.

Now that I've gotten that off my chest, I believe that bi-amping is the way to go with tubes for the mids and treble (they sound great) and a powerful SS amp for the bass. Yes, you should look at the impedance curve of your woofers and you can certainly apply the series resistor trick to see if you can add some bass extension with the SS amp.

Best Regards,
TerryO

[tubesguy2]

OK, here are my recommended crossover options...

Hope that helps,

Martin

Does indeed. Thank you, sir. - Pat

[Bob in St. Louis]

EXCELLENT post Terry!  Thank you.

Lin - Yea, how could I forget the guy that drove three hours to personally hand deliver a tube amp (the first one in my home) so I could audition it for five months. I have you to thank most of all. My greatest apologies for forgetting such a monumental milestone turning point in my life. 
Thank You Friend! 

Bob

[AJinFLA]

Hey there. 

A local buddy of mine is asking me to poke some holes in some plywood for a pair of Lowther DX2's he has. He does not have the wood working tools needed to accomplish this, so I volunteered to help him out. This is his first venture into OB. He's already got two pieces of plywood that measure 2' X 4'.
I've done many baffles, but not for Lowthers, so naturally, I've got a few questions.

- Where do I put the hole. You know, that whole "closer to the top, offset, front/rear mount, more to one side" argument.
- What's the ideal baffle size? Should I just use his 2' X 4' pieces, or trim them to....???
- What kind of bass output should he expect for a pair of DX2's on an open baffle?

I'm a bit confused here Bob. What method(s) did you use to construct all those many baffles? Why would these very same methods no longer apply for your buddy's to be built system?

Nelson Pass has, over the years, been trying to achieve the "sound" of a good single ended design with little or no negative feedback. He has admitted that tubes can sound very good and a SET is just about the perfect configuration for those requirements, with the exception of power.

I'm not quite sure what relevance someones purely subjective preferences would have for another person. Can you explain?

Triodes are the most linear device yet conceived while transistors usually require copious amounts of NFB to achieve linearity and their vanishingly small amounts of Total Harmonic Distortion (THD). If the THD figures equated to good sound, then all would be right with the world, but it seems that this isn't the case as tubes have many times the THD as most SS amp and yet...
Nelson Pass has been advocating reduction in NFB, especially Global Feedback, as a key to better (more tube-like?) sound. Coupled with reduction in the number of gain stages (he's down to one stage on the recent designs) he seems to have achieved significant sonic advances with his First-Watt designs.

You seem to be presenting purely anecdotal claims as some sort of evidence of fact. Can you produce a shred of scientifically acquired data to support any of these sonic claims? I would love to see them.

Many of the best speaker designers (Greg Monfort for example)

Who is Greg Monfort? When was it determined that there were "best" speaker designers and what makes him one of them?

I believe that bi-amping is the way to go with tubes for the mids and treble (they sound great) and a powerful SS amp for the bass. Yes, you should look at the impedance curve of your woofers and you can certainly apply the series resistor trick to see if you can add some bass extension with the SS amp.

Best Regards,
TerryO

People hold lots of beliefs. 
Many have zero effect on soundwaves (and are more visible spectrum light and/or priori knowledge related). Others are based purely on their own preferences and biases, which may or may not be applicable to others.

cheers,

AJ

[Bob in St. Louis]

I'm a bit confused here Bob. What method(s) did you use to construct all those many baffles? Why would these very same methods no longer apply for your buddy's to be built system?

-- What method did I use to construct MY baffles:
Experimentation. Plain and simple. Call it sweat equity if you'd like.
I'd build a baffle, mount it up and listen for a few days/weeks/months. I've sent more plywood with 15" holes in it to the burn pile than I can shake a stick at. If there was an aspect the baffle was insufficient, I'd give some long hard thought as to how the next baffle should be designed to 'repair' that deficiency. Works pretty darn well if you ask me. Every baffle I've built sounds better than the last.

-- Why won't my method work for Alex:
Simple: Because now I'm spending someone else's money. I don't want to see his baffles in the burn pile.
He asked me if I would help him build a pair of baffles. He doesn't want to revolve a series of ugly test mule baffles through his living room until one that suits the driver is accidentally stumbled on by me. I doubt he'd tolerate that. I'm not a math guy. I've never once designed a speaker based on what some software says and I'm not going to start now. My motive for this thread was to suck up some of the OB knowledge here by asking folks that have already installed DX2's on baffle where to put the darn thing. You can call it lazy if you'd like (and you'd be right), but the way I see it, this is a one shot deal and I don't want to burn it on the wrong alignment/configuration. I'd like to make something that's worth more than the plywood it's made of. AND, I'd like to make something Alex can be happy listening to and proud to own.
Bottom line: I don't know JACK about a Lowther and what it takes to make one sing properly, and I don't want to f... this up.

As we all know, driver orientation on a baffle can have a large effect on FR, sound quality, bass output, imaging, etc...
That being said a 15" driver, being the size that it is, is almost it's own baffle. At one point in time I had mine mounted in a "baffleless" configuration with very good results. A 6.5" driver (that I am very unfamiliar with) is handicapped in some regards and is much more dependant upon a baffle to reproduce an acceptable FR, bass output, etc...
I just wanted to know where to put the damned hole. 

Bob

[Mr Content]

Hi Bob, I would start with putting the Lowther about 850mm from the floor, This seems to work well for most seating positions. Also you could offset it slightly. Keep the 15 close to the floor to inprove boundry effect. Now if you really want to get fancy, you could go with a taperziod type baffle, this will cut down on cancellations. Also make the baffle as strong as your friend can afford. And try to make it thick enough to put a radius on the edge, the bigger the better. Now these are just my personal opinion, but they have seved me very well. Good luck Bob


Mr C aa

[Bob in St. Louis]

There we go. 33.5" and offset it a bit. Thanks Nig, you 'da man! 
I'll ask him about the trapezoid shape. But tell me, do you mount your driver (offset) under the peak of the trapezoid, or on the opposite side?

Thanks again Sir!

Bob

[MJK]

Bob,

If you are planning to use the crossover I specified earlier in the thread, it goes with the driver positions and baffle geometry shown in the simulation I linked originally. If you change the driver positions or the geometry it will require re working of the crossover. The crossover is set up to take advantage of the SPL hump inherently produced by that specific baffle geometry. You can see how this all comes together in the plots shown in the simulation.

Martin

[Bob in St. Louis]

Ok Martin. Gotcha. I didn't think about that, thanks for the heads up.
It should be plainly obvious by now I don't design crossovers and use software to build baffles. 

Alex - If you plan to augment the bass, the Alpha's are a known good choice. If you're interesting in hearing my pair of Augie's, I'd be more than happy to fire them up for ya'. Although, the Augie would most likely require a different crossover network than what's been mentioned here. Alex, I'm MORE than willing to fire up the router and let the sawdust fly building your baffles, sounds like fun. But when it comes to designing baffles for Lowthers and building XO networks, I'm the wrong guy. If we can decide what route we (you) want to take, I'll be in the workshop with power tools in hand in the blink of an eye.  aa
You can always go active (I CAN do that), but that defeats the purpose of what we began.
Alex where should we go next?

Bob

[MJK]

Bob,

The problem with the Augies is they are not as efficient as the Alpha 15As. Also, the low frequency cut-off will be determined by the baffle size so you can only expect bass down to between 40 and 50 Hz with either driver. Then there is the higher cost of the Augies compared to the Alpha 15A to consider. I am sure the Augie is a great driver but in this particular case I believe the Alpha 15A is a better choice, so the crossover was designed for a pair of Alpha 15A drivers.

Martin