AudiogoN Forums: Possible impedance matching issue with subwoofer?

Possible impedance matching issue with subwoofer?

Ok, many of us know about the importance of impedance matching with gear. I guess I have not thought enough about this with my sub. My sub is a powered sub like many are. It has it's own built in plate amp. The input impedance of these plate amps/powered subs is often quite low. Mine and many are 20k ohms or so. My preamp has an output impedance of 5k ohms, making for a possible poor match with the sub if I use the 2nd outputs on my pre into the sub's RCA inputs. This is the way I now use the sub.

I suppose I could hook the sub up by going from my amp to the high level inputs on my sub? I could simply run a second set of speaker cables out from my amp to my 2 subs this way right? This would avoid the impedance issue with my pre. Am I thinking correctly?

I think my subs may be rolling off the deep bass because of the impedance issue?

The system sounds very good as is, just wondering if perhaps I am onto something I have missed with possible bass performance improvement.

Grannyring (Reviews | Threads | Answers | This Thread)

02-05-12

Responses (1-33 of 33)

Click title to read one, or click date to read all below it.

02-05-12 Hi granny, yep, this is another example of poorly executed b ... Sgr

02-06-12 Sgr, as for balanced tube designs, bat and audio research ha ... Spinaker01

02-06-12 Thanks for the responses, but looking for an answer to my qu ... Grannyring

02-06-12 Grannyring, all of the understandings you expressed your op ... Almarg

02-06-12 you can add a ss buffer ... 1 to 1 gain amp ... to 2nd out ... Davehrab

02-06-12 Al, understand all your comments and thanks. very interestin ... Grannyring

02-06-12 This burson buffer may be just the ticket. thanks for the id ... Grannyring

02-06-12 yes, again you are completely correct. the amp would see a ... Almarg

02-06-12 Al, you are the man! thanks so much for your help. Grannyring

02-06-12 Btw, my pre to amp ic is only 3 feet long. yes, i use the lc ... Grannyring

02-07-12 Not sure what kind of sub you have, but with the ones that h ... Nsgarch

02-07-12 hi neil, not sure what you mean by the word "samples&q ... Almarg

02-07-12 No al, that's not the way it works (anymore ;--) yes, in th ... Nsgarch

02-07-12 Hi neil, i recognize and agree with everything in your last ... Almarg

02-07-12 Al, your erudite response notwithstanding, it's unlikely any ... Nsgarch

02-07-12 Thanks nsgarch and almarg for your comments and help. Grannyring

02-07-12 Input impedance is stated to be 20k so the preamp sees 20k t ... Koestner

02-07-12 Koestner, thanks. grannyring, koestner makes a very impor ... Almarg

02-07-12 Al, the builder told me if the plate amp has the negative hi ... Grannyring

02-07-12 Yes, but in addition to connecting the + output of the atlas ... Almarg

02-07-12 Ha, ya a big hum is the last thing i need1 Grannyring

02-07-12 Ok, one last question so i can make my final decision. i am ... Grannyring

02-07-12 I would add to the key facts that you listed for your gear t ... Almarg

02-07-12 That is what i thought and thanks al. Grannyring

02-08-12 If you hook the sub up in parallel to the preamp you will go ... Koestner

02-08-12 Koestner, i'm curious as to what preamp you were using. per ... Almarg

02-08-12 Koestner, i have only seen these placed between the preamp a ... Grannyring

02-08-12 Grannyring, the answers to the four questions in your last p ... Almarg

02-08-12 First off, i must say that al definately knows more about el ... Koestner

02-08-12 Hi koestner, agreed 100%, assuming that only a nominal pream ... Almarg

02-09-12 Thanks al for taking the time to write such an informing res ... Koestner

02-10-12: Sgr
Hi All,
While it is true that many manufacturers including ARC do make a balanced designed preamp, they don't conform to the balanced spec. (I'm sure this has a name, I'm not aware of it.) But I was having a similar problem as Grannyring between my ARC REf 3 and my Xilica Crossover. I made a quick call to ARC to see is my suspicions of incompatability were correct. The tech at ARC said, there is no point in even trying to get the two to work together that the ARC preamps could not be configured to work with low impedence input and outputs because of the circuit design. His quick less than two minute explanation was sell your ARC unit and don't purchase another unless the equipment you use are compatible with the ARC design.
A subsequent conversation with the guys from Atamasphere provided me with much of the explanations I outlined above but I did leave out all the technical reasons why tube preamp designs do not conform to the balanced standard that the music industry uses today which prevents impedence matches between equipment. The audio industry has adopted the balanced connector part of the equation and the cables are built correctly by the cable guys, it is the electronics guys who are at fault.
If all audio equipment was built to the balanced specs the music industry uses, we would not have these issues of impedence mismatching. And, I believe the music industry does successfully mix tube gear with solid state with no problems.
Not to sound like I'm picking on the tube manufacturers alone, but shame on the subwoofer guys for not dealing with this problem in their designs as well. If one is going to design products with class D amplifier circuits, then care should be taken to raise the impedence so that it matches so that it conforms with an industry standard as well. One wonders how many subwoofers have received bad reviews or that have had unhappy customers because of an impedence mismatch, and not the design and construction of the woofer itself.
Sgr (System | Threads | Answers | This Thread)

02-10-12 Wanted to update folks on my progress. well i have two subs ... Grannyring