AVS Forum banner
Status
Not open for further replies.
1 - 11 of 11 Posts

·
Registered
Joined
·
3,556 Posts
Discussion Starter · #1 ·
For instance I was comparing the Swan Diva speaker with an HTD speaker and the Swan gave their specs as Impedance 6ohm while the HTD is impedance 8 ohms. Does that mean I cant directly compared their specs?

Regards
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by Luis Gabriel Gerena
For instance I was comparing the Swan Diva speaker with an HTD speaker and the Swan gave their specs as Impedance 6ohm while the HTD is impedance 8 ohms. Does that mean I cant directly compared their specs?

Regards
Luis,


In terms of quality or sound - impedance tells you absolutely NOTHING!


The only use for this spec is in pairing the speakers with an amp - because it tells you

how much of a load the speaker puts on the amp. The lower the impedance, the more

difficult it is to drive, since the amp has to output more current into a lower impedance

load for a given voltage.


For instance - suppose you wanted to "double up" on the Swans - get two of each and put

them in parallel. If you parallel two 6 ohm speakers - you get a 3 ohm impedance - and

that might be difficult for your amp to drive. Amps usually will drive 4 ohms, since there

are many 4 ohm speakers - but lower and you are not guaranteed.


However, if you parallel the 8 ohm HTDs, you would have a 4 ohm load - and you amp

probably could drive that without problem.


Concerns such as those are the reason for the impedance spec. It tells you nothing

about sound quality, efficiency, power handling, how loud they will play...


Best advice is to ignore the impedance spec during speaker selection - and only have

it come into play when you are choosing the amps.
 

·
Registered
Joined
·
201 Posts
You must pay some attention to the impedance rating. As Morbius said, a lower rating puts more strain on the amp. Some receivers may not handle 4 ohms speakers, although it is becoming more common that they will.

Also, the rating is usually called "nominal" because that is an average of the resistance. Impedance is related to frequency. So, a 8 ohm speaker might have a low impedance of 4 ohms at some frequency, and a high of 12 ohms at another frequncy.


And, you could wire speakers in series. Two 4 ohm speakers in series will give a total of 8 ohms; two 8 ohms=16 ohms, etc., which is easier on the amp.
 

·
Registered
Joined
·
3,556 Posts
Discussion Starter · #4 ·
Is sentivity also something to consider along impedance. For instance a 6ohm speaker with 90db sentivity will be much harder to move than a 8ohm speaker with a 87db? Is sentivity more important or impedance when easying the load is the matter or are they not related at all?

regards
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by Luis Gabriel Gerena
Is sentivity also something to consider along impedance. For instance a 6ohm speaker with 90db sentivity will be much harder to move than a 8ohm speaker with a 87db? Is sentivity more important or impedance when easying the load is the matter or are they not related at all?

regards
Luis,


Here again - sensitivity doesn't tell you about quality - its use will be in selecting an amp.


The lower the sensitivity - the higher the power of the amp needed to drive it to a given

sound level.


Both impedance and sensitivity are used in selecting amps - not speakers.


Impedance will tell you what the load on the amp is.


Sensitivity will tell you how loud the speakers will be with a given amp.
 

·
Registered
Joined
·
609 Posts
It is really rating the efficiency of the speaker. A speaker with a higher sensitivity (higher number) will be more efficient to drive and take less watts to produce the same SPL as one with a lower number.


So the 90db one will be 'easier' than the 87db one regardless of ohms. In terms of watts needed.


A higher number in impedance is 'easier' on the amp, some amps will become unstable at low impedance. With lower impedance the output of watts increase from the amp. Thus making the amp work harder.
 

·
Registered
Joined
·
264 Posts
Speakers have a varying impedance, the manufacturers call it nominal impedance. A woofer can go as low as 2 and a tweeter as high as 32+. The nominal impedance is the middle of the range. So If you are looking at a 6 ohm speaker make sure that the electronics are safe with a 4 ohm load because a 6 ohm speaker will hit 4 before a 8 ohm will.
 

·
Registered
Joined
·
3,556 Posts
Discussion Starter · #8 ·
Sorry to bug so much but I needed to have that clear since my current receiver is an old Kenwood VR 409 (came with the HTB 503 HT package) and I know I cant take too much even with its 100W per channel rating which I think is more like 35W in reality. Still not bad while I get my HTD speakers and then upgrade the receiver to possibly a Denon 1804 or Yamaha or something in the less than $500 better yet $400 range. Thanks for the help and explanations.


Regards
 

·
Premium Member
Joined
·
1,999 Posts
Quote:
Originally posted by Luis Gabriel Gerena
For instance I was comparing the Swan Diva speaker with an HTD speaker and the Swan gave their specs as Impedance 6ohm while the HTD is impedance 8 ohms. Does that mean I cant directly compared their specs?
Not at all. The impedance rating is nominal or approximate. Further, any good quality modern amplifier can drive either impedance, although the 6 ohm speaker, should it actually average 2 ohms less than a comparable 8 ohm speaker, will draw more current to reach the same output, all other things being equal. Which brings us to your next question:

Quote:
Originally posted by Luis Gabriel Gerena
Is sentivity also something to consider along impedance. For instance a 6ohm speaker with 90db sentivity will be much harder to move than a 8ohm speaker with a 87db? Is sentivity more important or impedance when easying the load is the matter or are they not related at all?
3dB difference in sensitivity equals a halfing or doubling of output, given that the impedances are identical. In other words, a speaker rated at 87dB is half as sensitive as a speaker rated 90dB, and the latter will thus require 1 watt for every 2 watts the former does.


Obviously, this gets a little complex when we factor both load impedance and sensitivity into the equation at the same time, but be assured that any decent amp will very likely favor the 90dB/6 ohm speaker over the 87dB/8 ohm speaker.
 

·
Registered
Joined
·
3,301 Posts
Individual specification numbers tell virtually nothing useful by themselves. What is more important is (unfortunately) what is not generally published. That is the relationship between Impedance Magnitude and Phase angle vs. frequency.


Nominal impedance ‘use to be’ a rating whose value was limited to not drop much below (1 or 2 ohms lower than stated, I don’t exactly remember) but could exceed (greater than) almost infinitely. It is not an average.


Here’s a reasonable write up explaining some of the concepts that show even lower sensitivity and lower nominal impedance speakers can be easier to drive.

http://www.symphonysound.com/articles/tubefriendly.html
 
1 - 11 of 11 Posts
Status
Not open for further replies.
Top