Sensitivity?

[zumbo]

If you have a dvd player, put in Godsmack "Changes". Let the pyrotechnics go off. Call me when you get your hearing back.

 

[zumbo]

toasters suck some serious power

Watch-out for the iron. I watch the lights flicker while it's in use.

 

[highfihoney]

If you have a dvd player, put in Godsmack "Changes". Let the pyrotechnics go off. Call me when you get your hearing back.

i like godsmack but ive never heard of "changes" is it a concert dvd & if so is it titled changes?

im always on the look out for killer concerts especially ones that rock

 

[zumbo]

It's sooooooo killer. It is a dvd called Changes. I started a thread about it in the dvd section. If you like them, you have to have it. DTS baby!

http://www.amazon.com/gp/product/B0002NRRBA/qid=1139442719/sr=1-1/ref=pd_bbs_1/104-2895742-9951958?_encoding=UTF8&v=glance&n=130

 

[j_garcia]

I have all of their albums. Fun band I even have their logo worked into one of my tattoos. I'll probably go pick up that DVD I haven't been able to catch a show locally though...

 

[Buckeyefan 1]

I've got an old tune from the 80's called "Turn up the radio" by Autograph. The beginning of that song makes my headlights dim in my F150. My dual VC 4 Ohm 10's wired in parallel are making my mono amp see 1 Ohm. The truck's amp is pushing out 924 watts rms to both drivers with a 2 fared cap. It still drains on the alternator.

Zumbo: OK. But where did that Audio Source come from? I mean, you hurteded my feelings.

You updated that one too fast for me.

I'm just poking fun at this one from Ubid. How they can call it an amp at 8lbs makes me chuckle. I've had power boosters in Monzas and Vegas that put out more current.
http://www.ubid.com/actn/opn/getpage.asp?AuctionId=10608322

 

[PENG]

If you use one 4ohm sub, it hits much harder than one 8ohm sub because of less resistance. So, the amp is trying to double it's power. The same goes with home audio. Hook-up a 4ohm speaker, and the amp tries to double it's power. So, to me, that throws the XdB @ 1w 1m out the window.

Zumbo, it does not throws the XdB@1W 1M out the window. As you said, hook up a 4 ohm speaker to the amp, the amp tries to double it's power. So the speaker gets louder not because it's sensitivity suddenly increases to (X+3)dB @1W 1M but simply because you are now giving it double the power and you now get (X+3)dB @2W 1M. The bottom line is, in your original example, the 4 ohm speaker will not sound louder than the 8 ohm speaker given the SAME power input.

That being said, you are right about the 4 ohm speaker being able to play louder at the same volume (therefore same output voltage assuming the additional volt drop due to the higher current is negligile) but it is simply because 4 ohm speaker will, in this case, draw twice as much power from the amp as you pointed out yourself. I seem to be saying the same thing you are saying except the "that throws the XdB @1W 1M out the window" part. Sorry if I misunderstand your point.

 

[Jack Hammer]

My point is that one will never enjoy the potential of a well made 4 ohm home speaker with an average receiver. If one adds a separate quality power amp (not your $150 Audio Source), it won't be an issue.

Easy there pal, I've currently got well made 4 ohm speakers (M&K) with a slightly above average receiver (denon2805). And to top it off, I'm using an Audiosource amp ($68ubid) for zone 2. And I'm thinking of picking up a few more to experiment with monobridged front amplification.

 

[Jack Hammer]

I'm just poking fun at this one from Ubid. How they can call it an amp at 8lbs makes me chuckle. I've had power boosters in Monzas and Vegas that put out more current.
http://www.ubid.com/actn/opn/getpage.asp?AuctionId=10608322

I believe it. I posted a link in the deals section the other day for that amp as a cheap way for someone to power an additional zone at moderate levels.

I'm using the next model up for my 2nd zone and to be honest it is more than adequate for it's purpose. It doesn't hurt any that I only paid $68 for it.

 

[zumbo]

Zumbo, it does not throws the XdB@1W 1M out the window. because you are now giving it double the power and you now get (X+3)dB @2W 1M. The bottom line is, in your original example, the 4 ohm speaker will not sound louder than the 8 ohm speaker given the SAME power input.

But, I don't mean the same input. I mean the same physical level from the same source. In other words, hook-up the 8ohm speaker at half volume. Now, hook-up the 4ohm speaker at half volume from the same source. The 4ohm speaker will be louder. To me, that makes the dB rating null.

 

[zumbo]

The more I look at it, the more I see Mac answered my question in the first post.

87dB@4ohm=84dB@8ohm.

With 1w, the 4ohm speaker is louder.

Mac settled this one without even posting.

 

[Jack Hammer]

Here's what I measured on my system...

...this isn't fully scientific, but, I measured the difference between putting an 8 ohm speaker is place of my 4 ohm speaker. This was done simply by swapping the cables and moving one speaker. I used a meter stick with my Radio shack spl meter duct taped to the end, it made the distance 36", then I just put the end of the stick up against the speaker, between the tweeter and woofer.

For a consistant tone I used the Avia test disc and ran it in my Pioneer dv578a dvd player. hooked up to a Denon 2805 receiver with the volume set at -7. I also used the "external in" option.

I measured both left and right 4 ohm speakers and they were identical, Then I swapped cables and tried 2 different 8 ohm speakers.

The 4 Ohm speakers measured right at 80db, the 8 Ohm speakers both measured 77db, exactly 3db less. This says nothing about wattage or anything other than the 4ohm speaker was 3db louder than the 8ohm.

The speakers I used were: 4 Ohm M&K LCR851, and for 8 Ohm I used one each of a M&K K5 and a M&K K4.

Assuming the physical size of the speakers makes no difference and I didn't miss some other variable, then the a 3db difference seems to be valid. (I know, for it to be more scientific the size of the speakers would need to be identical, save the Ohm rating)

It actually took me longer to type this up than it did to swap speakers and take measurements.

 

[PENG]

Actually the key is, whether the sensitivity of the two speakers are the same. If they were, then the 3db difference was expected as you would invariably be feeding more power to the 4 ohm speaker, given that the volume was fixed at -7. Double the power (because the volume was fixed at -7) into the 4 ohm speaker resulted in the 3 db increase in SPL.