Beyond the Ariel

[dmason]

hi Kurt,

The Tubbys are pretty much in a league of their own. The hemp vibe is just magnified it seems, by the addition of the Alnico magnet, whose properties pretty much defy a written explanation, other than Lynns' description, of "low level delicacy," which addresses it nicely. They are stunningly musical. Giant Lowthers with balls. A 2 wat SET provides scary dynamic capability.

Are you using the Dayton 15-IB woofers?

[SunRa]

Hello,


I am sorry for the slight off-topic. I have a question I am sure have adressed here but I don't find it with the search function:

What is the program Bjorno uses in the simulations above?

Thank you!


dmason,

it's great you can offer a feedback on the tubby's. The selenium woofers seem to be a safe bet too.

[KCHANG]

Hi Dan,

Glad to hear that you like the Tubbys that much.

I am acutally going to San Diego around the end of this month. Perhaps I can stop by to say hello? I'll PM you.

I am not using the Dayton 15" IB woofers. Just some clearance-sale 15" subwoofer drivers I got from PartsExpresss several years ago. I've set a policy for myself to try to use the drivers I already have (too many already) before buying new ones. Someday when I have finally settled on an "ultimate" OB design, I'll consider buying better drivers to build that design. Let's see if the Tubbys will become part of that design.

Cheers,

Kurt

[bjorno]

Hi SunRa,

See page 30 posting #47:

Beyond the Ariel

b

[SunRa]

Thanks Bjorno!

[Lynn Olson]

Just to draw attention to the previous posts - the simplest version of what I've blathering about for almost a year would be:

Some kind of compression-driver HF - at the minimum, a B&C DE25 with one of the waveguides that Magnetar and others have suggested, the 18Sound XD125, or any of several other 1" plastic-film compression drivers.

Midbass - the 12" Tone Tubby, with or without EQ, to personal taste. In terms of EQ, there's a lot less to EQ than a Lowther or Fostex (which both have much rougher response), far higher power-handling, no midrange "shout" thanks to no whizzer cone, and just as much delicacy thanks to an old-school paper VC former and an Alnico magnet. Listen to the TT, you won't go back to drivers with whizzers - and I'm including the Feastrex here.

Bass-fill - Good to hear the 15" Seleniums are working out. They certainly have more appealing specs than many guitar speakers - more Xmax, quite usable Qts, and higher efficiency as well. I'd use two of them side-by-side at floor level, with the TT directly above them.

The higher power handling, efficiency and cone area of the Seleniums are very desirable in an OB system. The problem with the great majority of OB's is simply not enough power-handling for the task, which is what I heard at the RMAF. If you economize on cone area and efficiency, you get thin and scrawny sound. Get the dynamics right, and the other virtues of OB can shine out.

Crossover - there's no reason the HF and midbass can't use a straightforward passive crossover in the 1.5~2.5 kHz region. The bass-fill drivers can be independently driven with a 100~200W prosound transistor amplifier, with a prosound crossover/parametric equalizer. Note if you use a digital crossover/EQ, there will be a latency delay between input and output, depending on the amount of signal processing you do.

I would strongly urge that you do NOT pass the mid and HF signal through the pretty marginal sounding electronics of the crossover/EQ unit, and use high-quality amplification for the mid and HF units.

I consider Class AB, D, and T amplifiers on the lower bound of hifi, since all of them have significant rises in distortion with increasing frequency - fine for bass, not so fine for the highest quality mid/high applications. By avoiding switching artifacts (inherent in Class AB, B, D, and T) in the forward signal path, true (thermal) Class A amplification has better performance at lower levels and higher frequencies.

I like direct-heated triodes for the way they sound and their extremely low inherent distortion, but other folks like solid-state Class A - which require astonishingly large heat-sinks if the amplifier is true thermal Class A. Dynamic sliding-bias Class AB isn't really the same as true Class A (despite marketing claims to the contrary), but it does sound (a little) better than plain old-fashioned thermal-tracking Class AB.

[SunRa]

Hello,

I was thinking at the importance of the 300-1Khz spectrum of music and I was wondering if two Tone Tubby's per side would have combing/difraction problems.

Why using two? There are a couple of good reasons: around 100dB SPL in this configuration, and so easyer to match with a phenolic or radian CD in a 30cm waveguide, easier support of the highly complex music in this frequency region (a problem especially in open baffle where Sd really counts).

So again, what problems could appear in this configuration, considering a low-pass around 900-1.2Khz?

edit: 2 Lil' Buddys per side would also qualify with the advantage of a smaller offset between their sound centers and with even higher spl. Although the bottom end might not be as good as for the tubby's, nor the sweet alnico sound.

[bonjonno]

Lynn

You just answered a bunch of my questions. I've got the fever after reading about magnetar's latest success. I am considering the Lil Buddy 10" and B&C DE10 because the Tone Tubs are out of my budget. Was also looking at the 15" Seleniums and wondering if 4 are necessary. So now I guss they are. I was going to use an old behringer xo to separate the subs from the mids and understand what you mean about usin the low output only. So are you saying to just put a cap bundle in series with the mid array? If so, how good do they have to be? Will a couple of electrolytics with a quality bypass cap do the trick? And what xo frequency should I aim for?

Thanks, Jon

[apassgear]

Jon,

I’m not Lynn but I can also give you my point of view on hi pass caps or any cap on a passive XO…

They are as critical as any other cap on the system and I would never consider lytics, caps should be non polar, my preference goes for good Poyprop and they should be adequate bypass by a combination of smaller caps down to 0.1uf. bypass caps should be the best you can afford. Test for best results.

Amp performance is directly related to its load so the combination of XO + speakers is of prime importance.

My two cents.

[Graham Maynard]

Two 10" to 12" LS side by side are going to lead to notable voice reproduction anomalies for any listening done off-axis, especially with a combining reflected rear wave.

Its not just the centre to centre spacing, but the overall spacing between outer cone edges which will promote frequency selective interferences.

Cheers ........... Graham.