[jkelly]

I really love the "Richard" B200/Alpha15 combo.  I run it with either
a Vista-Audio i84 or a Jolida 102b and just love the bass and mid-range.

So I was thinking...

Since the prices are pretty affordable, would there be any benefit
to running 2 or 4 B200/Alpha 15's on a panel? What would I gain
and what would I loose?

thanks,

Jeff

[opnly bafld]

Jeff,
I wouldn't see any advantage of using another B, but another Alpha might be a welcome addition if your amps are up to it.
Keep in mind if you add another Alpha in parallel your inductor will start rolling off the bass drivers at @125hz instead of @250hz you have now.

Lin

[-Richard-]

Hi Jkelly ~

I am very glad to hear that your B200 and Alpha-15 OB's are giving you so much pleasure.

Since you mention the bass and midrange as being particularly pleasurable, I was wondering if you have tried the Planet 10 phase plugs in your B200's yet... I found it added "air" to the upper frequency musical material.

Adding the phase plugs also translates to a great deal more texture, detail and transparency to instruments that operate in that range.

However, it may reveal aberrations in ones equipment if there is anything a bit "hard" sounding in that frequency region... seeing that both of your amps seem to be ideal matches for your B200/Alpha OB's you should not have a problem with a refined sense of resolution. In that case I think you will find that the phase plugs will reveal quite a lot more musical material in the upper frequencies than you may now be hearing.

If you said that your amp and preamp were particularly intense in that region than I would not go that route... otherwise it is a very reasonable "upgrade"... easy to do as well with plenty of photographs on David's site to guide you through it... some "burn-in" time is needed after the surgery for things to smooth out.

Also... once the upper sonic region of your B200's is "liberated" the bass sounds even more fleshed out... without necessarily having to add another Alpha-15 driver... one of the strange enigmas of frequency "perception".

Warmest Regards ~ Richard

[TerryO]

I'll second Richard's recommendation of Dave's Planet 10 Phase Plugs. I listened to a pair mounted on Dave's "Ultra-Open Baffles" at last Summer's 4th Annual Vancouver Island Meet. I though they really helped, what was already a very good driver, to sound even better.
I've used some on my speakers (not B200 Visatons however) and they really transformed the sound...again, for the better

Best Regards,
TerryO

[mcgsxr]

I third the b200 plugs from Planet10.  Fantastic, cheap, and well worth the effort to install.

As for more subs, well, I would always try that... I run a 12 per panel, and would consider more subs for my place, but I cannot comment on your setup, I have not heard an Alpha, perhaps had I invested in those instead, I would be satisfied!

[richidoo]

This week I have been playing around with Martin King's Quarter-wave mathcad worksheets. They provide software simulation for the kind of question you are asking. It costs $25 to license them for one year. It can simulate any single full range driver in baffle, or 1 full range with any helper woofer, or with 2 helper woofers. I'm finding it very useful designing my first OB.

Website here, and a good article on OB design using the software.
Rich

[Michael V]

jkelly,

As someone who runs the same speaker setup, I would personally argue that using additional Alphas takes away from two main strengths of this design:  small baffle and small investment. 

To my ears, any time you can reduce the size of the baffle (while maintaining LF response) it's for the better.

Thanks to everyone who re-suggested the phase plugs.  Looks like it's time I finally took the plunge.

Regards
Mike

[Dmason]

If I were starting from scratch, depending on the size of the room involved, I would use two 15 inch drivers. They do two main things: move twice as much air, and allow the use of a narrower baffle, which means greater imaging, and lesser apparent width. I could be very happy with the Richard set up, in fact, I cannot wait to actually hear them, but with two drivers, you gain SPL, moreover, in relation to the rated SPL of the mains driver, in this case the B200, where it becomes a concern.  A smaller diameter, lower SPL driver, less so..[read Martin's paper] this was the single most important, and practical thing I myself learned; the relationship of SPL between mains driver, and bass driver. Having two, you now have a fairly seriously effective air mover, lowered distortion, lower power requirements.

ex: soon I will have two 96db, 16Ohm, 12 inch, hemp flavored JBL mains to play with, [ ] and these, ideally, would need two 18 inch pro audio bass drivers to keep up with them, making them unacceptable for smaller rooms, such as mine, but really good for big ones. Conversely, for a condo, I would look at smaller diameter, lower SPL mains, like B200, or Tone Tubby 4.5, and use ONE 15 bass driver. With B200 and up, another bonus is that you get to enjoy our lovely flea powered friends, such as 45, 2A3, and Maggie EL84. This is the relationship, as concluded upon, by Martin. Thanks, as usual, Martin. In fact, for a scaled down approach, I suspect the Tone Tubby 4.5 would be amazing. Hope my translation from Pano flavored Spano is readable.

[JeffB]

DMason,

Is this SPL matching a concern for passive networks only?

I have separate electronic cross-over, separate amplifiers for the main and sub-drivers and an additional volume control on the sub amplifier.
I can use the volume on the sub-driver to very closely match the output of the main and sub-drivers.
So basically I can't see a need to worry about the SPL of the drivers in my setup.

Unless there is just some basic inherit driver speed thing to worry about that is related to the driver SPL.

[Dmason]

Jeff,

Yes it is. Martin King's paper is enlightening, to say the least. ...Of course, active is ideal, but I was deferring to the above posts where their systems were running passively. Martin's conclusion is key, to this type of arrangement, which would be enjoyed by the vast majority of OB-nauts.

[markC]

I'm going to have to call you on "the imaging" comment of the 2 - 15's, DMason.
Unless they're contributing up into the high hundreds of hertz, I can't understand how they could contribute to imaging.

[Dmason]

Mark

Maybe my verbage was misleading; I was of course referring to the output of the mains, on narrower baffles. With respect to bass, I was referring to two drivers being able to move more air, for the above mentioned reasons.

I found that narrower baffles produced a more, far more 3D image; John Kreskovski concurs, however, this requires alternative means of dealing with bass, in his case preferring H baffles, with the NaO. So, with compromises in mind, an 18 inch baffle holds the 15 inch drivers, and is relatively narrow. I should add that Barfind, Nigel of Oz, after building 40 baffles for the B200, concluded that 18 inches wide was optimal for that particular driver. He uses Decware plan WO32 dual driver compound horns per side, for bass. I have seen 18 inch OB baffles contain two 15in drivers, mains, tweet, and covered with black grille cloth which obscures the large drivers, while black absorbs light therefore reducing apparent width, further. They really were a quite manageable size. I was impressed. This is how I will approach a DarkStar 2, later this year.

[markC]

Didn't mean to knock you Dan, just keeping you on your toes.
I've read many, many posts authored by Nigel, Barfind, Mr. Content ...with great interest over the last couple of years.

[-Richard-]

Hi Dan ~

Dark Star 2!!!!!!!... how exciting!... it sounds like your highly-tuned intuition and incredible powers of intense information gathering are reaching a confluence of sorts... the next "level"... level 2! is being forged in your creative mind as a further assault on audio nirvana on the cheap... the revolution continues!!!!!!  Viva la Revolution!!!!!

You mentioned compromises... that is how I look at my current OB baffles... visually they fit my room very nicely... larger than what I have now... even if they are narrower but taller, for example... would tilt the present visual balance of the room toward them... something I want to avoid.

But I am the exception, I believe... most serious music lovers that have followed your original suggestions to get involved and explore the cheap yet on-the-way-to-being-the-definitive sound that OBs are capable of would gladly upgrade to the Dark Star 2 solution... with your preternatural surreal sense of where the magic lies in DIY OB speaker designs I am certain it will catipult us to a much higher level of sonic bliss.

What I am hearing is deeply satisfying. And for me it all started with your gentle push to get me involved... thanks Dan for your incalculable help.

Warmest Regards ~ Richard

[Dmason]

hi Richard,

thanks for the undeserved praise...

Looks as though I will have a couple of interesting things dropping on my lap to evaluate, one is the above mentioned, Tone Tubby tweaked JBL D130, and the other is a 5 inch, 30 year old cheapo Japanese TV speaker. For me, based on my own experience, I have become interested in magnet material contributing to the overall OB gestalt as much as anything else. It is well known that there is some unmeasureable alchemy going on, with Alnico magnets. The engineers over at Audio Salem will dunk your head with their slide rules, but, then, why do guitarists insist on Alnico. And they likely have never listened to speakers with alnico magnets anyway. At any rate, Alnico rules, and drivers operate in a mechanically, or physically optimal set of conditions, mounted on  open baffles, static air masses on each side of a completely unloaded driver. SET + Alnico driver + OB = Magic. More magic. Alnico is mo betta. With the JBL, I can see what a big wideband super high quality JBL does when it is upgraded, tuned up ,and has a hemp cone. A VERY nice set of circumstances, there. The TV speaker is a Coral, and has a large Alnico magnet. Ed Schilling recently commented that THE best smaller wideband drivers he has heard over many, many years, were the old Japanese TV, and radio speakers. Many were Coral. This diameter driver is ideal for a smaller OB set. A one bass driver set up.  The clouds of imagery are gathering.

[fergs1]

Greetings Fellas, D Mason wrt the alnico guitar drivers the reason guitarists (myself included)like them may have little to do with hifi, but then again? The basic premise with alnico is that its magnetic flux is much more dependant on operating temp than other magnets and so in affect when pushed very hard (ie. guitar amp to 11) the coil heats up, the flux reduces giving less control over the movement of the cone thus distorting and 'smoothing' out the sound giving rise to that creamy overdriven sound along with the sound of the amp clipping(valve of course)
   In regards to hifi I'm sure there is something in alnico giving a particular sound but in a different context to guitar speakers            peace and goodwill     fergs