I have a Pioneer SX-1250 and I have an opportunity to pick up some Cerwin Vega D7's and D9's. I've seen official spec sheets on all the D series CV's posted here and elsewhere, which shows nominal impedance to be 8 ohms. But I've also seen specs stating nominal is 4 ohms. Cerwin Vega's own website states that this rating only means that at some point(s) during testing the output throughout the listening spectrum that 4 ohms of impedance occurred, however briefly. I know my receiver is rated down to 4 ohms but I'm concerned that if I drive both A and B together I'll overheat the amps. Any thoughts?
Can I safely run two pairs of Cerwin Vega's
- Thread starter Dougfoot
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From what I can find the D7s are 8 ohm while the D9s (or, at least some of them) are 4 ohm. If so, I would not run them in AB speaker mode.
Having said that, it is always best to check a speaker's nominal ohms with an ohm meter (especially with older speakers that could have drivers that differ from the OEM units).
As for the term "nominal" the simplest way I can explain it is that "nominal" means that on average the ohm (impedance) will be X but that this impedance can, and will, drop below and rise above the given nominal impedance rating depending on frequency.
Having said that, it is always best to check a speaker's nominal ohms with an ohm meter (especially with older speakers that could have drivers that differ from the OEM units).
As for the term "nominal" the simplest way I can explain it is that "nominal" means that on average the ohm (impedance) will be X but that this impedance can, and will, drop below and rise above the given nominal impedance rating depending on frequency.
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Here's a link to the spec sheet I was referring to:
http://audiokarma.org/forums/showpost.php?p=3532419&postcount=9.
And here's a quote from Cerwin Vega's FAQ page:
"Question #2: My receiver is 8 ohms but your speakers are rated at 4 ohms. Is there a problem?
Answer: The 4-ohm impedance rating on some of our speakers refers to nominal impedance meaning literally “in name only”. Since a speaker’s actual AC impedance varies depending on the frequency of the input signal, its nominal impedance refers to the impedance or resistance at only one point along the frequency curve. Cerwin-Vega’s nominal impedance rating refers only to the lowest point of the impedance curve which immediately follows its resonant peak. In order to establish this rating, Cerwin-Vega does a sine wave sweep encompassing the entire frequency band and rates the impedance as described above.
When tested, an amplifier is usually driven with a 1 kHz sine wave into an 8-ohm load for 6 to 8 hours without overheating or exceeding its rated distortion levels. This is a very strenuous test and in the real world of normal listening, is the equivalent to playing music at full volume for 6 to 8 hours.
A recent magazine article stated, “. . . if your receiver handled 8 ohms during the UL test, it should handle lower impedance loads under less strenuous conditions at home.” The article went on to say, “. . . a name brand, component grade [stereo amplifier/receiver] will comfortably handle a pair of 4 ohm speakers.”
(Stereo Review, June 1996, p. 64)"
I kinda already know the answer, I was just hoping somebody with definitive knowledge would say "no prob, the 1250 is a beast and can handle it all day long!". I just got really excited about the prospect of blasting the D9's AND the D7's at the same time. Ohhh the SPL's!!!
http://audiokarma.org/forums/showpost.php?p=3532419&postcount=9.
And here's a quote from Cerwin Vega's FAQ page:
"Question #2: My receiver is 8 ohms but your speakers are rated at 4 ohms. Is there a problem?
Answer: The 4-ohm impedance rating on some of our speakers refers to nominal impedance meaning literally “in name only”. Since a speaker’s actual AC impedance varies depending on the frequency of the input signal, its nominal impedance refers to the impedance or resistance at only one point along the frequency curve. Cerwin-Vega’s nominal impedance rating refers only to the lowest point of the impedance curve which immediately follows its resonant peak. In order to establish this rating, Cerwin-Vega does a sine wave sweep encompassing the entire frequency band and rates the impedance as described above.
When tested, an amplifier is usually driven with a 1 kHz sine wave into an 8-ohm load for 6 to 8 hours without overheating or exceeding its rated distortion levels. This is a very strenuous test and in the real world of normal listening, is the equivalent to playing music at full volume for 6 to 8 hours.
A recent magazine article stated, “. . . if your receiver handled 8 ohms during the UL test, it should handle lower impedance loads under less strenuous conditions at home.” The article went on to say, “. . . a name brand, component grade [stereo amplifier/receiver] will comfortably handle a pair of 4 ohm speakers.”
(Stereo Review, June 1996, p. 64)"
I kinda already know the answer, I was just hoping somebody with definitive knowledge would say "no prob, the 1250 is a beast and can handle it all day long!". I just got really excited about the prospect of blasting the D9's AND the D7's at the same time. Ohhh the SPL's!!!
Baron K Rool
Well-Known Member
I measured 5 ohms on some D-7 speakers. Claimed 8 ohms on the box.
Why temp fate. If the speakers are being paralleled by the A + B speaker switch position the amp could see a 2 ohm impedance periodically depending on music content; this could be very stressful if it's sustained and ohhh the SPL's could turn into ouch the SPL's. :tears:
bowtie427ss
Lunatic Member
DC resistance is NOT the nominal impedance of a driver or speaker system.
Resistance readings at DC are meaningless in this exercise. While it may be helpful in assessing certain situations, it in no way indicates the load your amplifier will see at any given frequency. It's wanking.
If you have a true RMS DMM and a signal generator, you can wire up a bridge and measure your speakers impedance at any given audio frequency that way, or invest in DATS or similar software which will do a sweep and show you a nice graphic representation of your speaker's impedance curve across the audio spectrum.
EDIT: After reading your other thread on this topic it occurs to me that nobody has bothered to ask what the current health status of your 1250 is. Minimally, the regulator section should be rehabbed before i'd connect ANY speakers to it. If a competent tech has deemed it healthy and safe to operate, i'd probably run both pairs of CV's without giving it much thought. In good working condition, 1250 is a very capable receiver. If it's original and unserviced in recent years, you're flirting with disaster and it's only a question of "when" not "if".
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Chris Brown
Super Member
Like I mentioned in your other thread (there is really no need to have two threads about the same topic), I used to run 4 D-9's and ran them off an SX-1050 and definitely pushed them to their limits. I also ran the 4 D-9's using my Yamaha M-2 at one point which is no fan of low-impedance loads either, with no issues. I find it EXTREMELY UNLIKELY that the D-9's are 4-ohms, not only because the spec sheet says otherwise, but simply because if that were true my SX-1050 very likely would have burst into flames. Just keep an eye on the light-bulb in the tuner section, if it's dimming on the bass notes, then you're near the amp's limits.
As a matter of fact....
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http://www.audiokarma.org/forums/showthread.php?t=301366
bowtie: I can't say for sure about how many or how thorough, but the previous owner had the unit recapped and after I got it I took it to a tech I trust and had him deox it and go thru it to make sure everything was up to snuff. I'd say on a scale of 1 - 10 its aesthetically a 9.5 and operationally a 10. But to be honest I am saving up to have it completely done, frame off restore, ALL caps and most transistors as advised and documented here in AK on a thread dedicated to 1250's.
Sorry everybody, I didn't mean to offend with regard to me posting this question here and in "speakers", I'm kinda new here and I just wanted to cover all bases as far as opinions from different viewpoints goes.
Sorry everybody, I didn't mean to offend with regard to me posting this question here and in "speakers", I'm kinda new here and I just wanted to cover all bases as far as opinions from different viewpoints goes.
KutzlerTrans
Jennie & I with Buddy and Barney.
No insult taken, Were big boys, I have ran 3 sets of 5.6 ohm klipsch's and others full blast w/dire straits low bass. Ya better check and reset your "idle current" and "dc offset" first and run Fans on the heatsinks. You can get a service manual on AK Free. it will tell you how to do these adjustments. If it does not sound right to you,Stop runnin it, Fix it. When these units are right, It'l run 1/2 throttle all day long. I you- tubed freight trains at 3/4th volume. Shook the neighbors walls. These 1250's are top shelf workhorses. Keep it cool. If you plan on runnin it hard, Re-grease the output transistors. I will repeat, Keep it cool.
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charles 1973
Super Member
Dougfoot:
According to the Spec Sheet in your post #3, Both the D7's and D9's have an 8 ohm Nominal Impedance. Operating Both Pairs is 4 ohms, and within the Safe Operating Limits of your Reciever if it is Clean (heat sinks) and in good operating condition. As a Safety Precation, I'd suggest, when operating at 4 ohms, keep the power level at -3 db (1/2 power) at the most, this will insure No clipping occurs, and keep it well ventilated.
When an Amp is rated for 4 Ohm Speakers, they take into account it is a Nominal Rating and should easily drive a 3 ohm or perhaps lower load over a narrow bandwidth. I have driven 4 Ohm speakers (that dip bellow that) with my AVR, Rated for 6 Ohms and had no problems.
According to the Spec Sheet in your post #3, Both the D7's and D9's have an 8 ohm Nominal Impedance. Operating Both Pairs is 4 ohms, and within the Safe Operating Limits of your Reciever if it is Clean (heat sinks) and in good operating condition. As a Safety Precation, I'd suggest, when operating at 4 ohms, keep the power level at -3 db (1/2 power) at the most, this will insure No clipping occurs, and keep it well ventilated.
When an Amp is rated for 4 Ohm Speakers, they take into account it is a Nominal Rating and should easily drive a 3 ohm or perhaps lower load over a narrow bandwidth. I have driven 4 Ohm speakers (that dip bellow that) with my AVR, Rated for 6 Ohms and had no problems.
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BillyBatts
ALOHA!
I've been running four JBL-L19's off of my Yamaha CA-810 for over 30 years.
Now, I don't listen to College-Level Earth-shattering volumes any longer, but still, never had a problem.
If you are concerned, don't do it. But I would. But.... That's just me. I typically run two sets of speakers from my systems. Always have.
That reminds me, I have a 1975 Radio Shack Receiver (whopping 12 watts per channel) that has "Quatravox" 4 channel. I used to like that set-up. I'll have to give it another listen and see if I'm still as enthused as I was back then.
Now, I don't listen to College-Level Earth-shattering volumes any longer, but still, never had a problem.
If you are concerned, don't do it. But I would. But.... That's just me. I typically run two sets of speakers from my systems. Always have.
That reminds me, I have a 1975 Radio Shack Receiver (whopping 12 watts per channel) that has "Quatravox" 4 channel. I used to like that set-up. I'll have to give it another listen and see if I'm still as enthused as I was back then.
Tedrick
Infinity-phile
In this case nominal ≈ approximate. Impedance fluctuates with frequency, so nominal is used to report an overall approximation of a speaker's impedance.