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DBX souhdfield imaging speakers

shrinkboy

shrinkboy

Addicted Member
guys-- tryin' again here. i picked up a pair of the DBX SF-10 Soundfield Imaging Speakers. they blow my mind, but the problem is they do not have the matching SFC-10 Soundfield Imaging Controller with them. i know a lotta you guys are general scroungers, and i am hoping someone has either come across one, or will come across one and let me know about it.

BTW, anybody ever heard a set of these? i am using an old 10 band Eq right now, and kinda guessed a profile for them. they make a 30 watt kenwood integrated sound like like 300watts. they really blow my mind.

i'm not kidding.

shrinkboy
 
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DBX SPK, SF- 10 SOUNDFIELD SYSTEM
Description: (2)10" WOOFERS, (2)4" MIDRANGES, (4)1/2" TWEETERS
Manufacture Years: 1985 - 1987
Additional Information:
Retail
MSRP: $1,500.00
 
thanx, bolly! got em for $100. now all you gotta do is find that SFC-10 soundfield imaging controller and send it to me... :D

always your friend

shrinkboy
 
Jim,
If you can dig up the suggested crossover frequencies, speaker impedence and how they are connected (series or parrallel) then it would be fairly simple to design a passive network. Buying good foil open air chokes, quality caps and resisters from Parts Express or Welbourne Labs it shouldn't be difficult to build good passive crossovers of even 4th order. There are a number of online calculators to use if you have the numbers to type in, it takes few parts and would be a east layout. Many of the Dallas Audio Club members could give you the help you need given the proper information.
Except for the chokes you could get most everything from Tanner's but I would recommend this for only a prototype and using better resisters and caps bought online for the finished crossovers. Having the crossovers outside the boxes is the best way to go and the use of double sided terminal strips would help to get the padding of the tweeters correct and allow you to leave L-pads out of the finished crossovers, keeping a cleaner signal.
 
wow! david-- that is a very intriguing and uh...challenging idea. i even think i may understand a small percentage of what you are talking about there. you are saying: skip the associated eq box and build an external passive crossover, substituting for the active crossover of the eq, and build a box using parts purchased from suppliers. right?

the DBX Eq has pots for bass and treble. plus some other push button selections which i forgot about now. how do you account for those controls and differences offered by different rooms? isn't the crossover 'set' once all the components you mention are assembled? this is one of those areas where my ignorance overcomes completely my interest (remember the schematic reading fiasco?)

can you splain more

j
 
I am not familier at all with the speakers you picked up but there are a few basics that will always apply and if you are planning on keeping them in one room you really don't need to adjust once you get it set. You have tone controls to fine tune for different music anyway.
Basically an inductor or choke only allows freqs under its value to pass, so it will cut off how high your woofer goes. A cap will only allow freqs above its value to pass so it sets where you tweeter starts. A combination will allow only freqs above the cap and below the choke to pass so that is how you set your mid.
Slopes are how many decibals fall off per octave and a 1st oder which is only a cap or a choke is 6 db or the slope is 6 decibals per octave, a shallow slope. By making a circuit using resisters, caps and chokes you can go as far as a 24 db slope which is probably where most active crosses will take you.
So if you know where the woofer rolls off and where the tweeter kicks in you have the 2 points for the crossovers and you can build them with steep to shallow slopes to get the same sound as an active crossover only it is not adjustable. You can make crossovers with L-pads in them that will give you some leeway in adjusting your mids and highs but they often are not worth the sacrifice in sound quality if the speakers are really good.
Any speakers you have that have knobs you can turn to adjust the tweeter or midrange have L-pads. If you put resisters in the circuit to limit the highs because of them being too bright it is called padding.
To be able to get the values of the componants to build the crossovers you have to know the freq to start and or stop at and the impedence or how many ohms the speakers resistance is. If you have 2 8 ohm tweeters they will be 16 ohms in series or 4 ohms in parrallel.
Basically you have to know the ohms of the drivers, how they are wired if there is more than one of the same and where the crossover points are. With that you type the numbers into a calculator and it will give you the values you need for the componants used in all the crossover slope types.

Or you can shell out the cash and buy the specific EQ built for the speakers. I just wanted you to know that unless there is some weird thing going on in the EQ like the one for Bose 901s for instance that you can build a passive crossover network that should achieve the same thing.

Most active crossovers separate the freqs between the source and the amp(s), so if you want to adjust lows, mids and highs you need 3 amps. Bose 901s have 9 drivers that are all really mid range and the EQ for them changes the signal to extend the bass and highs. You cannot do that with passive crossover componants, so if that is what the EQ for the DBX does you will only be able to use a DBX EQ or using a schematic build one.

You with your limited knowledge on reading schematics and soldering skills could build exellent crossovers because they have very few parts and the quality of the crossover depends on the quality of the parts since even complex crossovers are very basic circuits.

You heard my system and for each channel there are 2 componants acting as crossovers. The 2 way has a free running 12" so there is nothing on it and the tweeter has a 1st order or 6 db high pass which is a single capacitor. The sub on each side has a 1st order or 6 db low pass which is a single choke.

Today I stacked a second pair of Heils on top of the first wiring them in parrallel, so I doubled the ohms and had to halve the capacitance to keep the high pass at the same freq. The wiring is pos to one side of the cap, from the cap to the pos of the 1st tweet, neg from tweet #1 to pos of tweet #2 and neg to the neg post for the speaker cable. Now just to make you crazy electricity runs from neg to pos.
 
don't have time to completely digest at the moment, but, i think i learnt alot in there just now. thanx for a thoughtful, helpful and complete reply. will get back to you...

can i email an attachment to you that a guy sent to me?

jim
 
ok, dave- let me axe another question-- what is the difference between an active crossover and an equalizer? lets say the DBX Eq doesn't show up for a long time. instead of fabricating the external passive crossover you mentioned, what if i were to go to an active external crossover? would i get anything with that that i don't get using a generic 10 band equalizer?

thanx
 
An active cross divides the signal before amplification, so if you have 3 way speakers you have to have 3 power amps (stereo), each dedicated to a separate bandwidth.

If you can get an approx with an EQ then apparently the speakers don't use crossovers and operate along the kines of 901s, or they don't sound right without boosting the signal in certain areas. Crossovers only divide the signal up before it gets to the drivers and don't effect EQ at all.
 
I see you put an add in an online electronics web page. It came up when I did a search to find out what these speakers are.
 
Dbx Controller

I own a set of DBX-10's with the SFC-10 imaging controller. If you need specs from the original manual I can provide that for you since I have a copy.

Let me know>>>Jeff
 
jdeh-- i see this is your first post on AK-- did you get here somehow by searching for info on the DBX SF-10 or the controller? i appreciate your response, but all the problems i was having when i started this thread have been solved and have been enjoying my 10's for most of the year.

how long have you had yours, how do you like them, what do you drive them with? i have found a small, and i means SMALL community of users on the web who have provided me with info and support regarding them. i think they are a great speaker, and my only quibble is that they are so damn ugly.

if you could upload pix? that would be great; i don't have a digicam, and i'd love to show the rest of AK these speakers. you have joined a neat community and i hope you'll hang around. thanx for posting

shrinkboy
 
I've been reading through most of the postings here, and I have to state categorically that, regardless of how well you are currently enjoying your SF-10's, you are not getting the full benefit of them without the active controller that was REQUIRED for them to work optimally. The SF-10's were a lower-cost alternative to the very costly, top-of-the-line dbx SF-1A's, which also used an electronic controller, and both its controller, as well as that for the 10's had, to paraphrase another's posting, similar goings on inside as did that for the Bose 901's.

Finding such a controller is probably going to be very difficult, but in the event that you do, you'll be amazed at how much better your SF-10's will sound than they do now.

And, yes, they ARE ugly!
 
emaidel-- if you are addressing me, shrinkboy, e. i have long since located an SFC-10

controller. and yes, you are right, they DO sound better. but i appreciate your post.

shrinkboy
 
I'm glad for you that you obtained the controller and now realize how much better the SF-10's sound. Insofar as their cosmetics, we in the salesa department at dbx (I worled for the parent company, BSR, from 1983 until 1989) always referred to them as "trash cans." The dbx engineers howled in protest until one day, at a trade show, someone entered our booth and actually tried to throw out a styrofoam coffee cup into an SF-10!! Thought you'd get a kick out of that one.
 
>> Thatch Ear: "...unless there is some weird thing going on in the EQ like the one for Bose 901s for instance then you can build a passive crossover network..."

Sorry Thatch, but with DBX soundfield speakers there is definiately "something weird going on"; even weirder than Bose 901's. Soundfield 1 and 10 speakers are phased arrays. The controller "individually tailors both the amplitude and the phase of the musical signal to each of the drivers [14/speaker for the soundfield one, 8/speaker for the soundfield ten] so their outputs sum in space to produce an oval radiation pattern at all frequencies". These speakers are truely unique. For a thorough article on how these were designed and measurements comparing them with other high-end speakers available back then check out: http://www.bostonaudiosociety.org/pdf/bass/BASS-17-06-9005.pdf
 
chinasailor- don't know if you noticed that you commented on a zombie thread...but thanks for the input. i used the SF10's for several years, but eventually sold them on. my wife hated their 'trashcan' appearance (i was never too fond of their look either) and i could not get away from the fact that while hanging a magical soundstage, nevertheless the woofers boomed, the mids squawked and the tweeters seemed to shriek. i sold them to a guy who, get this, paid someone to drive from LA to Dallas to pick them up so they wouldn't have to ship commercial...
 
jdeh said:
Dbx Controller

I own a set of DBX-10's with the SFC-10 imaging controller. If you need specs from the original manual I can provide that for you since I have a copy.

Let me know>>>Jeff
Click to expand...

if you have the manual please let me know also the specs. my email is zenter35@gmail.com been looking all over for them. thank you so much
 
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