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Correction [message #50507 is a reply to message #50492] Wed, 10 January 2007 15:06 Go to previous messageGo to next message
FredT is currently offline  FredT
Messages: 704
Registered: May 2009
Illuminati (1st Degree)
In my intitial post I erroneously stated the external height of the One Pi Tower is 48". The correct dimension is 38".

So..when will the dual kit come ? =) [message #50509 is a reply to message #50492] Wed, 10 January 2007 20:33 Go to previous messageGo to next message
Steve H is currently offline  Steve H
Messages: 7
Registered: May 2009
Esquire
Im looking forward to seeing the dual woofer kit (hint hint !). That would be the perfect thing for the amp on my workbench right now...

Side Firing Sub [message #50510 is a reply to message #50504] Thu, 11 January 2007 04:44 Go to previous messageGo to next message
FredT is currently offline  FredT
Messages: 704
Registered: May 2009
Illuminati (1st Degree)
Good idea! If I were doing this I probably would use a different design from the One Pi, with an Eminence Beta 8 in a sealed chamber instead of the Alpha 8 in a ported one. The Beta 8 has greater power handling capacity and it will perform well in a sealed box as small as 0.3 cu ft.

A good economical woofer section could include the Dayton 10" DVC sub that's on sale for $25. You could drive it with the 75 watt MCM plate amp that's now on sale for $40. The Dayton DVC sounds really good in a 1.5 cu ft sealed enclosure, so everything would fit fine in the original One Pi Tower enclosure with the mid, tweeter section sealed off from the woofer section just below the Beta 8.

Here's another idea that would be helpful if you were driving this with flea power SET amps like my Paramours. You could drive the subs' plate amps directly from the line output of the preamp and insert a passive high pass filter at each SET amp's input to roll off it's output below 100hz. Relieving the amps of low bass duty would enhance their ability to drive the Beta 8's.

Now I'm confused about which version of the enhanced One Pi tower I should build:)

Re: Could be popular. [message #50515 is a reply to message #50509] Thu, 11 January 2007 12:42 Go to previous messageGo to next message
Matts is currently offline  Matts
Messages: 359
Registered: May 2009
Grand Master
The one pi as is is great- i"ve built a pair. But if the cab size could stay relatively small with 2 woofers in there, it could be the answer to the SET dream of a good hi-eff speaker with "good" bass, minimal xover components, and, low cost. The 8" Alpha is a nice driver.

Xover thoughts... [message #50519 is a reply to message #50515] Thu, 11 January 2007 20:16 Go to previous messageGo to next message
Steve H is currently offline  Steve H
Messages: 7
Registered: May 2009
Esquire
Thoughts on how to go about a smooth crossover for the two woofers ?

Re: Xover thoughts... [message #50521 is a reply to message #50519] Thu, 11 January 2007 23:45 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18027
Registered: January 2001
Illuminati (33rd Degree)

I would use a 2.5-way crossover, measure it and see how it goes. I can't see any reason it wouldn't provide everything you would want. The idea is to crossover one woofer at a relatively low frequency, so both are playing down low. Then run the second woofer up to the tweeter crossover point. The low frequency woofer should be mounted low in the box, and the midwoofer should be mounted higher. I'd put them all on the same baffle, aligned vertically. The low woofer isn't as critical with respect to placement, just make sure it's within 1/4λ at the crossover point.

I would run the low woofer up to 150Hz or 200Hz, so that it can smooth the floor bounce modes that would exist for the upper woofer were it to be operated alone. As I said, I would position it no further than 1/4λ below the midwoofer at the crossover point. Tweeter crossover is about a decade above low woofer cutoff, around 2kHz. The tweeter should be placed just above the midwoofer, less than 1/4λ away at its crossover point. Each of these crossovers can be made first-order, because none of the drivers is particularly sensitive to over-excursion, and each driver is to be placed within 1/4λ of the adjacent driver at the crossover point.


Re: Pi Studio One Tower [message #50527 is a reply to message #50492] Sat, 13 January 2007 11:41 Go to previous messageGo to next message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
Hi FredT,
Very nice. I lyke your One's.
I appreciate very much your "Old Style Theatre Speakers" (and your work), the ()3 Pi Theater two-way using Eminence drivers. They could go in a movie retracting the fifties: They have a very powerfull "wood" looking, real vintage style. Nice.
I like your "right tools" you have on your speaker-shop. I would bring them to my mum's dinning room where I have my speakers on the dinning table for a few months. Hi hi.(Sorry mum). They despise speaker people anyway, I don't know why, and is not because of loud sound. Nice work on the Shop. dB

It Could Be A While [message #50536 is a reply to message #50509] Mon, 15 January 2007 03:52 Go to previous messageGo to next message
FredT is currently offline  FredT
Messages: 704
Registered: May 2009
Illuminati (1st Degree)
All this talk about the Studio One Pi motivated me to pull my One Pi towers out of my cavernous speaker storage warehouse (a small upstairs bedroom:) and set them in the system for a few days. I have to admit these speakers are hard to beat just as they are with one 8" woofer. They probably woulnd't fare as well as most high end speakers in an anechoic chamber test, but it a real room they sound very "right" - tight and reasonably extended bass, warm midrange, just enough treble sparkle to let you know they are quality speakers, and no hard edges anywhere. Anyway, I have all the parts for a couple of other projects including enclosure refinishing for a pair of Cornwalls, so I believe I'll set this project on the back burner.

Somebody has asked about buying the existing One Pi tower enclosures, and if he does I'll be left with a pair of one Pi kits with no enclosure, and that will provide the motivation to buy another pair of Alpha 8's and get started on the dual woofer towers. In the meantime if anybody else in the Houston area wants the tower enclosures they're $100 with internal damping material, bi wire spkr terminals and ports installed (and your word you'll order the One Pi kits from Wayne).

Re: Pi Studio One Tower [message #93022 is a reply to message #50492] Tue, 26 January 2021 16:28 Go to previous messageGo to next message
tomlang is currently offline  tomlang
Messages: 6
Registered: February 2011
Location: Augusta, GA
Esquire
This is certainly the oldest thread I have ever brought back from the dead. It seemed appropriate though, as I went back through this forum and behold, found something very interesting to build.

I have attached a proposed dimensioned drawing of the One Pi 2.5 speaker. Assuming running the lower woofer only up to 200 Hz, I come up with a 1/4 wavelength of 16.875 inches, so I spaced the lower woofer up 16.5 inches from the floor and same spacing to the upper woofer. Does this seem reasonable? Is 200 Hz a good choice? If I went lower, say 150 Hz I could make the tower taller. But not knowing the tweeter crossover point I'm not sure if that is better.

This 3 cu ft box is tuned at 49 Hz, F3=43 Hz. That is not quite as low as the single woofer 2 cu ft box discussed above. That brings up a question as I have never listened to a 2.5 speaker before. Will the 2.5 seem like more apparent base as it fixes some floor bounce problems?
Re: Pi Studio One Tower [message #93025 is a reply to message #93022] Wed, 27 January 2021 09:45 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18027
Registered: January 2001
Illuminati (33rd Degree)

I like the whole concept of the 2.5-way speaker very much. It's the best and most natural way to resolve baffle step, in my opinion. Of course, that means running the lower "helper" woofer up to the baffle step frequency.

This brings me to the flanking sub concept though, which is a modified form of a 2.5-way system. By detaching the helper woofer and offsetting it a couple feet in all three dimensions, it mitigates SBIR and lower-frequency room modes in addition to baffle-step correction.

That's a pretty big deal, because it smoothes the notches created by reflections from nearest boundaries. As you've mentioned, there's a notch created by the reflection from the floor and there's also notches from reflections from other nearby boundaries. The one I've found is actually most objectionable in most cases is the wall behind the speakers. It's responsible for a huge 15dB hole somewhere between 80Hz and 120Hz in a large number of installations.

So if you place the mains on a stand so they are at ear level, and then put the helper woofers on the floor - beside and slightly behind the mains they are flanking - they will provide SBIR mitigation and will reduce higher frequency room modes in addition to baffle step compensation.
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