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2pair
03-25-2005, 05:17 AM
Now that I have your attention! :D
L110 vs. 104/2
I have a question regarding how to A/B these speakers. I recently upgraded speakers and amps, and now don't know how it all goes together. http://audioheritage.org/vbulletin/images/smilies/banghead.gif
My problem is this....My L-110's (recently rebult to like new mechanically) are 8ohm, my 'new' Kef 104/2 are 4ohm. My amplifier (dbx BX-3) also recently aquired, has a switch on the back that says: A or B= 2-6 ohm/A+B= 4-12 ohm on one side on the other it says A or B= 6-16/A+B= 12-16 ohm .
So..if I'm reading this right, if I use the Kef's alone as 'A' system I would have it set to A= 2-6 ohm, right? and if I use the JBL's alone as A system I would set it to A= 6-16 ohm right?
Easy so far... now what if I want use Kef's for A and JBL's for B? Or worse yet, what if I want to play A and B? Did any of this make sense? So if 'A' is 4ohm and 'B' is 8ohm, the load is what? 12 or ? I would then use A+B=4-12ohm, right? But then its only set right to play the Kef's alone as 'A'. To play the JBL's alone as 'B' I would have to set the switch to A or B=2-6ohm, right? http://audioheritage.org/vbulletin/images/smilies/banghead.gif (I think I can Bi-amp 2 sets of speakers from this one amp, but I have more studying to do....http://audioheritage.org/vbulletin/images/smilies/blink.gif )
Anyway, back on topic...to add to the 'problem' this amp is 4channel mono so I have to learn how to bridge too...If I'm reading this right, I could give the L110's 550W/ch if I wanted to get all 'Mad Scientist' with this...http://audioheritage.org/vbulletin/images/smilies/eek.gif http://audioheritage.org/vbulletin/images/smilies/screwy.gif
I would appreiciate any advice you all have to give me... I don't want burn the house down...(not 'till I get my stuff out, anyway..)
Untill about 8 months ago all I knew about stereos was plug 'em in... but then I got the L110's,( gave away my old Energy2's) and my old recievers sounded like hell. So I upgraded from a Technics reciever Sa-r377 to a dbx CX-3 preamp and a Rotel tuner, and above mentioned amp. A little better, eh? (and a CD player from le-14 thumper, thanx)
Thanx guys!
P.S. (You guys have taught me everything I know...but not everything YOU knowhttp://audioheritage.org/vbulletin/images/smilies/applaud.gif )

Steve Gonzales
03-25-2005, 10:03 AM
If your amp is a discrete 4 channel , ie : 4 SEPERATE inputs , then it doesn't matter WHAT impedence your speakers are in respect to WHICH output channels they play on, just as long as they add up to the recomended value. If it is a true four channel, the pairs will put a load on the amp as if they were connected in parallel, this is why they specify the impedence be within a certain range. They assume that if you have one pair of speakers, you'll hook them up to "A", that's all, it's NOT that the "B" pair isin't the exact same amplifier(in ability). This is a 2 ohm stable amp, treat it as such and you will be fine. If it is a STEREO amp and you assume that it is 4 channel because it will ACCOMMODATE 4 speakers, you are mistaken and more than likely, but not absolutely, the speakers are "in series" when both A+B are playing at the same time, I'm not trying to offend you, I just don't know if everyone knows the difference, that's all. If there is a bridging switch, then there should be a graphic on the chassis or imposed lines around the speaker terminals to show the correct speaker terminals to use when bridging mode is used. Good Luck, Steve G

Edit: Upon further review, I believe that even if it IS just a stereo amp, it is 2 ohm stable and A+B are in parallel too. Don't Bi-Amp two pairs!. Listen carefully to the sonic difference when doing it to even one pair, it might not sound too good then too. Same for bridging them also. I think that the 12/16 ohm for A+B refers to bridged mode because in this mode, whatever your "nominal impedence" is, you cut that in half for calculating the "load the amp sees" in bridged mode, thus if A=4 ohms and B=8 ohms, the amp "sees" a 1 ohm load, 6 ohms if the switch puts them in series. I hope I've got this correct, Mr. K, Giskard, where are you?


BTW, I never got to see your completed grills, or was that someone else????

Earl K
03-25-2005, 01:35 PM
2pair,

- The info you have posted is somewhat muddled and confused .

- Take some pics of the back & front so that we can see for ourselves all the connector options - as well as the printed info you've referenced .

- Your description of all the options superficially describes an amp / that lacks a power supply large enough to run all 4 channels simultaneously at even 8 ohms.

- Remember ; theres a good reason that dbx no longer makes amps.

( You can get a users manual for this by buying one online ).

:)

Steve Gonzales
03-25-2005, 01:38 PM
He'll get it figured out with the proper info, Thank you! :p

2pair
03-25-2005, 09:02 PM
- The info you have posted is somewhat muddled and confused .

I know! thats my problem... http://audioheritage.org/vbulletin/images/smilies/biggrin.gif

maybe this will help, from the manual...



incorporating 4 independant power amps, the bx-3 functions as a stereo amplifier, a 3 channel amplifier, or a 4 channel amplifier, and up to four pairs of speaker systems can be driven at one time






speaker impedance selector- this system should be set to the rated mpedance of the speaker system in use. comsulting the operating manual of your speakers, set the selector to the proper posititon
for instance, when driving only one set of the speakers using 8ohm impedance speakers, set the selecetor to the right '6-16ohm' position. when driving simutaneously both speake systems A and B which use 8oh, impedance speakers, set he selector to the left '2-6ohm' position





- Remember ; theres a good reason that dbx no longer makes amps.




Why would that be...?


BTW, I never got to see your completed grills, or was that someone else????

That was me...I never finished http://audioheritage.org/vbulletin/images/smilies/sulkoff.gif , and I dont have a camera to send pics sorry...


-
Your description of all the options superficially describes an amp / that lacks a power supply large enough to run all 4 channels simultaneously at even 8 ohms.


from manual...
power output single mode;180W/ch 8ohm 320W/ ch 4ohm 400W/ch 2ohm.
bridged: 550/ch 8ohm 800/ch 4ohm 850/ch 2ohm


also has a 3 way switch marked:2ch(BTL) /3ch(BTL) /4channel (what does BTL mean?)

I hope this helps....thank you all!

Zilch
03-25-2005, 09:40 PM
BTL = "Bridge to Load." It's how you convert any two channels into a single channel with twice the power capacity.

In the 2-channel position, it's bridging the four amps into 2pair.

In the 3-channel position, it's bridging one pair to make 3 total, like to drive a mono subwoofer, for example.

Read more, and it'll tell you which ones, which inputs to use, and how to connect the speakers in those modes....

2pair
03-25-2005, 09:46 PM
thanx!
Its the ohm load that I don't understand...
I can play one or the other set of speakers, but not both w/o flipping the switch(at the back, of course)

Zilch
03-25-2005, 09:52 PM
Yup. OR, you could run each pair of speakers on a different pair of amp sections....

Earl K
03-26-2005, 05:39 AM
Hi

You know, it really seems the source of your confusion stems from a divide between what "you" want to accomplish ( A/B two sets of speakers ) and the actual function of some switches which happen to have an "A/B" function marked on them . So ;


(i) INPUTS :
- How many input connectors are there ?
- What type or sort are they ?

(ii) OUTPUTS :
- How many output connectors are there ?
- What sort are they ?

(iii) FRONT SWITCHES :
- How many switches are there on the front of the amp ?
- What do they say ? or What are they called ?

(iv) BACK SWITCHES :
- How many switches are there on the back of the amp ?
- What do they say ? or What are they called ?


(A) From the info you have posted ; The wattage ratings that you quoted would indicate an amplifier that does have a large enough power supply to run your 4 speakers at one time . You should read that manual a few times - taking note of any special like "Warning - do not do the following :blah: "

(B) Assuming there are 4 inputs and 4 sets of outputs ; hookup your 4 speakers to these individual channels. Drive the 4 inputs from 2 sets of independant stereo outputs on your preamp. If that doesn't exist on your preamp you'll need to purchase or build a solution.( DBX marked a front end unit to this amp. ) To compare speakers back and forth, select which set of speakers to listen to from a preamps' A/B selector switch .

- The "A/B" switches that you referred to in your first post shouldn't be confused with an "A/B" input channel selector switch. They (it ? is ) appear to be, simply impedance load/matching switches. Again, pics at this stage would be really helpful .


Why would that be...?

The very fact this conversation is necessary indicates "muddled" thinking on the part of dbx(s)' product development team .

- Don't put one KEF and one JBL together onto one output channel . From the info that you posted / your amp won't blow up - because it has a 2 ohm rating. The reason not to combine dissimilar speakers is simply that they are likely going to have different sensitivites that you cannot independantly control when they are wired together. Put them on separate channels . FWIW ; the load that a KEF & JBL represent to the amp when paralleled together is @ 2.7 ohms .

- Yes, it sounds like you can use this amp to biamp something .

- Yes, as Zilch pointed out , you can use the "BTL" options to gain more power by combining amplifier sections.

:cheers:

2pair
03-26-2005, 07:40 AM
Front has four buttons all under heading of 'Speakers', under that heading a subheading 'front', then another sub heading rear...and under each of these is A-B, for each . k... Oh, and 4 vol. knobs.L/R L/F R/R R/F...2 meters, and a power switch.
Bach has: aformentioned 2ch/3ch/4ch...has four inputs:2 front 2rear..8(eight) speaker outputs ,4pair, 2 A ,2 B
then theres that pesky speaker impedense switch....A,B=2-6ohm/ A+B=6-16ohm on one side...A,B=4-12ohm/ A+B=12-16ohm... fan outlet, unswitched outlet, voltage selector....thats it!

Maybe I haven't been clear, what I want to do is switch , instantly from one to the other, not neccasarily(?) play both at once.
By the time I turn it off, flip the switch, back on...I 'forget' what the other sounded like, Ya know?


The very fact this conversation is necessary indicates "muddled" thinking on the part of dbx(s)' product development team .

good point
Thanks again all, but you know it's youse guys fault, or at least JBL! http://audioheritage.org/vbulletin/images/smilies/wink.gif

Earl K
03-26-2005, 02:56 PM
Front has four buttons all under heading of 'Speakers', under that heading a subheading 'front', then another sub heading rear...and under each of these is A-B, for each .

- These buttons ( or are they toggle switches ? ) sound like they might be source selector switches ( to choose stereo inputs #1 or #2 ) for each of the four amplifier channels.

- By what terminology does the operators' manual refer to them ?




... Oh, and 4 vol. knobs.L/R L/F R/R R/F...

Are they volume controls for each of the 4 amp channel or balance ( panpot ) controls ?

- How does the operators manual refer to them ? ( By what terminology ? )

2pair
03-26-2005, 04:49 PM
- These buttons ( or are they toggle switches ? ) sound like they might be source selector switches ( to choose stereo inputs #1 or #2 ) for each of the four amplifier channels.

- By what terminology does the operators' manual refer to them ?




From the manual:
SPEAKER - Speaker System Selector
Two speaker speaker systems, System A and System B, can be connected to the BX-3 for all modes(2,3,4ch). these swiches choose the system to be used.
Press Front A or B, Rear A or Bbuttons in accordence with the speaker terminals to which the speaker system is connected. The red LED above the selected button will light.




Are they volume controls for each of the 4 amp channel or balance ( panpot ) controls ?

- How does the operators manual refer to them ? ( By what terminology ? )


Input Volume Controls
For use in adjusting the incoming signal level. The input level will increase by turning the knob....... ... Keep the input Volume Controls turned fully clockwise in normal operation.
My fingers are cramping!

IS there ANYBODY with a scan of this manual out there!! http://audioheritage.org/vbulletin/images/smilies/banghead.gif

I'll just be happy with one speaker system or the other, I guess, But I really did want to A/B these things to see how the old JBL stood up to the newer 'reference' Kef's. From the muddling about I've done so far Bass definition is WAY better on the JBL's. But I have to admit that Norah Jones does sound sweeter on the 104/2's.
Thanx for trying to help , Earl...