RF-83 Impedence

[Jay481985]

they are 8 ohms acceptable...... but why didn't you put them on the 4 ohm binding post to begin with?

[MudPuppy176]

I didn't hook them up to the 4 ohm posts because I wanted 250/channel, not 125/channel. I didn't hook them up to the 2 ohm posts because I didn't want 62.5/channel. If you hook up 8 ohm speakers to the 4 ohm posts, you get half the power. Halve it again with the 2 ohm posts. Unfortunately the opposite also holds true: Hook up RF83s to an 8 ohm post and you'll cook/overheat an amp because they're 4 ohm speakers and will draw twice the power. These are 4 ohm speakers advertised as 8 ohm speakers. It does wonders for that fabled Db/watt number, but doesn't do an amp much good. Don't get me wrong, they're awesome on the 4 ohm posts. Conversly, I have a couple of expensive large paperweights that were designed for an 8 ohm load they simply didn't get.

[Jay481985]

usually a sign of a good amp is that when you half the ohm you double the wattage as it can step down sufficently if it can.

Also you really never will use 250 watts..... I believe 64 watts will reach maximum volume.

[michael hurd]

"I didn't hook them up to the 4 ohm posts because I wanted 250/channel, not 125/channel."

You would have gained 3db. If you want more power, BUY more power. You could hang more power on them if you want, nowdays power is cheap. Most of the people on the forum with the same speakers drive them with receivers. Unfortunately the speakers did not play well with your amplifier.

[DrWho]

Replacement RF83s arrive, hook up to new Mac. Mac overheats at 25 watts indicated (RF83s hooked up to 8 ohm binding posts).

Hook up the RF83s to the 4 ohm binding posts, voila, works fine. Loud, nice to say the least.

Simple conclusion: these are NOT 8 ohm speakers, I have two cooked amps and a new Mac that say so.

Interconnects, speaker wires, etc are not to blame. The only variable was the RF83s.

Could two pairs be assembled incorrectly? I suppose its possible, but highly unlikely. They are just not 8 ohm speakers.

25 watts into an 8 ohm load is still only 50 watts into a 4 ohm load - which is well within the current carrying capacity of your amplifier.

For what it's worth, your process of elimination is not conclusive that your speakers are "8 ohms". There are hundreds of speakers on the market with similar impedance dips and are rated the same. And then there are other people on the forum running Mac amps with RF-7's and RF-83's that don't have any issues either.

If running on the 4 ohm taps works, then great....but I have a feeling that it's a band-aid fix.

Btw, how do you know u didn't get the same speakers back?

[MudPuppy176]

I know they're different speakers because I had both pair here at the same time. The dealer dropped off the new and picked up the old pair. I spoke with McIntosh tech support yesterday. He said the RF83s dip to 2.8 ohms at some frequencie(s) but didn't have access to an actual impedence plot. He seemed very surprised Klipsch would call them 8 ohm speakers. He mentioned B&W's high end speakers dip to 3.2 ohms which he also found too low to be classified an 8 ohm speaker. His opinion was that its basically a marketing ploy to raise the efficiency numbers. Consumers want to see 100dB/watt when they're paying high dollars for speakers.

[Jay481985]

most recievers handle it fine

[michael hurd]

"I am driving my 83's with a McIntosh 6300 integrated that only has 100w per. It has PLENTY of power." jmorgan32

[Fish]

The bottom line,to keep it simple.If an amp can't drive 83's or 7's without serious issues and damage,toss it and get a real amp.

[turbobusa65]

DrWho make it three! my first set of RF-7's that I got around christmas had a wire off one of the mid's, they were fresh off the U.P.S.truck!

[DrWho]

Yikes, 3 it is!

Btw, the reason they call them 8 ohm speakers is because many people freak out when they see something other than 8 ohms. A prime example of this is the KG series speakers - many of the exact same model were all labelled as 4, 6, and 8ohm at different times. People always focus on the single low impedance dips but often ignore the rest of the bandwidth with very high impedance. The music we listen to is essentially playing at random at every frequency which means the amp is seeing a combination of impedances between 3 and 30+ ohms. Heat is what kills amplifiers and the average current over every frequency is going to be much less than if you had an 8ohm resistor for a load instead of the speaker...unless you're playing something that hits only a few frequency bands at loud levels.

In other words, the nominal rating of a speaker is a meaningless concept - yet more meaningful concepts always seem to get rejected by the market...

Nevertheless, I kinda agree they should be rated at 4 ohms...or maybe klipsch should just stick to a meaningful rating system and ignore those that choose to reject them. It's really a lose-lose situation. Sell no speakers or risk stuff breaking when people start pushing the limits (25W into the RF-83 is fricken loud).

[MudPuppy176]

Thanks for your concurrence DrWho. The whole impedence issue is grey at best as I know of no "standard" means of measurement. Its very complex as its frequency dependent as you noted. The amp and speaker manufacturers all have their own methods of rating their products it seems. There are people (I for one) that like it quite loud at times. A fried amp is never the goal however. To Fish who said get a real amp (or words to that effect) I tend to lean towards the belief that a McIntosh MC-252 more than qualifies as a real amp. (250W into the RF-83 is WAY fricken loud).

[Jay481985]

max output is supposed to happen at 64 watts on the rf-83 its just headroom.....

[DrWho]

or more like power compression...

[MudPuppy176]

Headroom and power compression, interesting terms. As far as I know they're rated at 250RMS, 1000peak each.

Anything more than 64 watts goes to heat, gamma rays and/or invisible light? Maybe I need a tin foil hat. Please advise ASAP.

[DrWho]

lol!

Ideally, when you double the power to the speaker, you should get a 3dB increase in SPL. However, at very high SPL's this "linear" relationship falls apart and you need more than double the power to get a 3dB increase. The extra power goes to waste as heat inside the voice coil - which further leads to more compression. So though the speaker might be able to achieve a 120dB transient with 100W of power, it might need 200W to maintain 120dB (which would equate to 3dB of power compression).

[jmorgan32]

"I am driving my 83's with a McIntosh 6300 integrated that only has 100w per. It has PLENTY of power." jmorgan32

Mike, you freaked me out! I saw the post subject line about RF83 & I was interested of course. Scrolling down, reading, drinking Bud Light (of course) and all of a sudden I see you post above. I bolt up in my chair and think "WOW this guy is just like I am!!" Then I see my name and realize you pasted a quote from me. I don't post here that often. OK, I guess you "had to be there."

Take care Mike,

Joe

[MudPuppy176]

Klipsch must be well aware of the improper rating of their reference series of speakers. They are now offering to repair my amps. RF-83s really don't qualify as 4 ohm speakers, let alone 8 ohm speakers. A horrrid dip to 2.8 ohms can never qualify as an 8 ohm load. Their willingness to repair my amps is a testament to good customer service, but honest marketing would've precluded the problem. Rf-83s are less than 4 ohm speakers, but may be considered 4 ohms within reason. If it all pans out, Klipsch will have redeemed themselves in my eyes, but others' amps may self-destruct with less than designed speaker loads. Just a word of caution: RF-83 are actually less than 4 ohms, certainly not 8 ohms. On the positive side, they have no reason to falsify their efficiency. They are quite impressive. Very nice speakers, just count on 4 (or even 2) ohm loads.

[TNRabbit]

The reason they are 8 ohm speakers is because if you put an ohmmeter on them, it gives an overall average of 8 ohms average across the audio spectrum (as almost all speakers do). ALL speakers have dips & rises in their impedance/resistance at varying frequency levels. Generally, the LOWER the frequency the dip occurs (where the main power requirements are), the more it can affect your amplifier. It's not uncommon at all for an "8 ohm" speaker to dip to 2.* ohms at a given frequency.