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Old 1st November 2008, 03:30 AM   #1
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Default Spherex Class D amps on Ebay

Klipsch has been selling a lot of the complete Spherex systems--including the amps--on Ebay this week. They've been selling for around $100, usually between $90 and $120, with $20 shipping.

The amps use 6-channels of the Apogee DDX8001 chip with 40W H-bridges. These are true digital amps, with no analog conversion if you use the SPDIF input. The ST part number for the DDX8001 is the STA308A. The STA308A is NRND, but the STA309 is the replacement. The STA308 is used in a lot of smaller home theater systems from Hitachi, JVC and others. The Spherex amps have a decent toroid that supplies a switching regulator for the amps. So it's a nice amp to play with, and the speakers that come with it are a bonus.

The Apogee chips are very cool. Each amp channel has 10 digital biquads that allow you to build crossovers and EQ--that's a lot of processing power waiting to be put to good use. I've got a piggyback board that takes control of the I2C bus to program the biquads, along with Windows code that models the biquads. Eventually I'd like to build my own ST309 boards, so I've been using the Spherex amps to get this software working. I don't have any plans to sell or give away a mod kit for the Spherex amps because there aren't that many of them, but I might come up with a generic mod kit for the ST308-based home theater systems that would work. But that's well off in the future...
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Old 14th November 2008, 04:22 PM   #2
stinems is offline stinems  United States
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Hi Neil, I bought a pair of the satellites off PE a while back, sans sub and amps. Interesting sound that is well executed but you can only take low quality drivers so far. At any rate, your mention of the amp/filter Spherex guts intrigues me more.

It sounds like I'd need an I2C adapter for my PC to interface with the DSPs. I found some used PCI card adapters on Ebay for a reasonable amount, but I'm not sure what I need. Am I understanding correctly that your 'code' is something you made ad hoc as a GUI of sorts to tweak the filters? Is there a command line interface supported by TI?

Just curious...

Cheers,
Sam
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Old 14th November 2008, 06:50 PM   #3
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Quote:
Originally posted by stinems

...It sounds like I'd need an I2C adapter for my PC to interface with the DSPs. I found some used PCI card adapters on Ebay for a reasonable amount, but I'm not sure what I need. Am I understanding correctly that your 'code' is something you made ad hoc as a GUI of sorts to tweak the filters? ...
Sam
I've got a microprocessor board that I connect to the Spherex amp to control the I2C bus. This micro is a lot more capable than an off-the-shelf I2C adapter because it can initialize the DDX-8001 chip and can save preset register loads and switch back and forth between them. The micro can store up to 6 different crossovers for the amp channels, and will reprogram the amp in response to a single command from the USB interface or in response to toggling a switch connected to the micro.

I've also got a Windows application that lets you define the crossovers and EQ parametrically (freq, Q, gain, and filter type). The windows app also has a math model of the biquads, so it plots the predicted filter response for each amp channel. The application also reads in driver measurements (FRD files) and predicts the composite response of the driver and filter combination. For that reason, the application is called the Biquad Crossover Designer. This code also calculates the coefficients for the biquads in the DDX8001 chip and sends them to the microprocessor board. So you can experiment with different crossovers or EQ and hear the results almost instantaneously (the program uses 500 sample points, so it takes a couple of seconds to calculate the response).

It's pretty neat stuff, but I keep going back and forth between two different versions of the program and building more hardware to test it. One version of the program is for smaller 2 or channel amps, and the other version is for the multi-channel amps like the Spherex. Neither version is "finished", but I can program the Spherex amps and the TAS3004 amps and use my application to build crossovers from speaker measurements. So I can actually say it works! But there are a lot of features I still need to implement, and lots of "cosmetic" stuff to do.

There is more info on this project, along with an early sample of the 2-3 channel version of the Windows apps in this thread:
more info

So, I don't really have an answer to your question on what you need to hack into the Spherex amps, because I'm not selling anything right now, and it takes a lot of work to retrace the steps I've taken. Eventually I'd like to sell my software with my own amplifier boards, but I don't intend to offer a mod kit for the Spherex amps. It takes quite a few cuts and jumpers on the Spherex amps to hack into the I2C bus and to re-route some of the I2S lines (the Spherex amp uses a TI DSP chip to route the SPDIF and A/D to the DDX8001, so the board needs to be modified). I haven't even finished figuring out all the Spherex mods yet--I've only got the SPDIF input working. If you are interested in tracing out the Spherex circuitry and developing a mod procedure, maybe we could work something out...
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Old 14th November 2008, 09:04 PM   #4
cuibono is offline cuibono  United States
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Thanks Neil for pointing out the ebay auctions! I had tried to get a set of the spherex speakers a couple of years ago, but no one was selling them anymore. I just happened to find this post the day before the auctions closed, and I won one last night. I'm excited to hear the system. I'm currently developing a couple of multi amped speaker pairs, and either use a computer or analog equivalent for crossover and frequency adjustment, but the idea of using a stand alone, flexible digital solution is very attractive.

Sam, wrt the quality of the spherex speakers, see this, if you haven't already. Peter Aczel is a controversial, but serious and well respected reviewer. He's done some pretty high end loudspeaker reviews - the Linkwitz Orion++ and the B and O BeoLab5, among others. He gives the spherex system very high marks. I saw the individual components available at PE, but without the amp Neil is playing with, they probably can't match their original design.

Neil, good luck with your work. What do you think of the original spherex system? I just recently left a job in Reston btw...
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Old 18th November 2008, 10:05 PM   #5
Havoc08 is offline Havoc08  Denmark
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Thank you for the heads up. I contacted Klipsch on ebay, but they only ship to US

That Spherex set looks very promising and I had never heard of it before this thread.

There shouldn't by any chance be an american citizen in here Who could forward it to me if I purchased it via paypal to their adress? (expenses covered of course)
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Old 20th November 2008, 08:20 PM   #6
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Quote:
Originally posted by Havoc08

There shouldn't by any chance be an american citizen in here Who could forward it to me if I purchased it via paypal to their adress? (expenses covered of course)
You might like to try these people, they seem to offer the service you need. They will forward parcels from the US to many countries in the world.

http://www.myus.com/index.shtml

http://www.mailforwarding.biz/
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Old 20th November 2008, 08:57 PM   #7
Havoc08 is offline Havoc08  Denmark
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wow nice links cirrus... thx

I'll read up on their terms tonight so maybe I can get at set when they re-list the spherex set.
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Old 20th November 2008, 08:58 PM   #8
cuibono is offline cuibono  United States
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I've been listening to the spherex setup for two days now. I am very happy with them. They are excellent for small rooms - very inconspicuous, very forgiving of placement and their omni design fills the room with very evenly dispersed sound. I haven't tried setting them up in a larger room, but I think they would do very well.

I would say their frequency response leaves nothing to be desired - almost - there is a small bump in the lower midrange that was prominent while they were burning in, making singers sound a little congested. Boxy sounding. But this has mostly gone away now. They have a very enjoyable sense of spaciousness, especially in the 5.1 setup. The bass is a little woolly, but I wouldn't expect more from such a minimalist system.

Their imaging is more vague than I'm used to, due to their omni nature, but that's okay - what you get in exchange is very consistent sound in a small place. Anywhere in my room, they sound the same, and great. That's hard to do in general.

One would expect that for the price, and considering their intended market, speakers like this would be pretty flawed. The above list are the only flaws I'd cite these speakers for - very little, in my opinion. Really, I'm thrilled with how they perform, and they've overcome my high expectations I had to begin with.

So I'd say these are very well engineered speakers. I haven't had any technical problems with them (very good, considering their complex guts), and for $130USD, they are more than a steal. I highly recommend them for small rooms. I'm not sure they are 'giant killers', but really, I haven't set them up next to my main speakers yet. I have no reservations about them besides the slight boxiness in voices. In every other area, they really excel. Their price to performance ratio is unbelievably high IMHO, especially since they come with six channels of amplification and a remote control. Try them, you won't be sorry.
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Old 20th November 2008, 10:14 PM   #9
Havoc08 is offline Havoc08  Denmark
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Sounds great, thx for the mini review cuibono (hope you haven't encouraged people to purchase them all before I get a set ).

Does anyone know if this set have ever been sold in Europe? Or if it was intended for the US market only?
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