[oldnacl]

I have a pair of Nobis speakers (they were made in Milwaukee WI by a small company). They're about 30 years old and still sound great, but they're 4 ohm and my amp wants 8 ohm (also, I'm using them with 8 ohm surround speakers)

Any suggestions on what to do to make them compatible or a recommendations for a reliable S Florida (West Palm Beach to Ft Lauderdale) speaker repair shop that would do the job for me?

 

[Morbius]

Quote:

Originally posted by oldnacl I have a pair of Nobis speakers (they were made in Milwaukee WI by a small company). They're about 30 years old and still sound great, but they're 4 ohm and my amp wants 8 ohm (also, I'm using them with 8 ohm surround speakers) Any suggestions on what to do to make them compatible or a recommendations for a reliable S Florida (West Palm Beach to Ft Lauderdale) speaker repair shop that would do the job for me?

oldnacl,


You may be fine with 4 ohms - provided you don't turn the volume up too high.


The problem is that an amp rated for 8 ohms may run out of current when driving

4 ohm speakers - but not if you keep the volume control down.


If you really want to turn your 4 ohm speakers into 8 ohm speakers - wire a 4 ohm

resistor in series with one leg to the speakers. The amp will see an 8 ohm load.


However, half the power will go into heating up that 4 ohm resistor.


That's why the former solution is preferred.

 

[cpc]

Use it as is and watch your amp for heat and listen for distortion. If you ever run into problems, I wouldn't even go so far as to wire a 4 ohm resistor, I'd try a 2 ohm resistor first. If 4 ohms is too low, 6 ohms would probably be ok.

 

[Larry Fine]

At a given volume from the speakers, the amp is more likely to clip with series resistors than without. Use the speakers straight and monitor the heat of the amp until you get used to keeping it set safely.

 

[oldnacl]

Well, I don't believe the problem I have is related to high volume (I listen with the volume relativly low) but I hear distortion, especially when the system is on auto decode, as from digital input from the DVD player. That's why I also asked for a reliable repair shop in S FL, thinking it may be a speaker problem. With the amp set to 2 channel stereo, the audio sounds fine.

 

[oldnacl]

Oh, and the problem goes away when I connect the 8 ohm R & L speakers that came with the surround sound package. I just like the sound of the Nobis - maybe I should hook them up to the "B" speaker connections and just use them with analog input...

 

[Kal Rubinson]

The amp is clearly inadequate with this load and probably will not be able to handle the additional output required if you add the resistors, anyway. Since you say that it was a package, you are likely stuck with using it as such or buying a higher quality amp. I wouldn't bother unless you went to a higher quality system overall.

 

[oldnacl]

To put the information into layman's terms, the 4 ohm speakers require higher output from the amp than 8 ohm speakers for the same volume level - is that correct. Carrying it a bit further, might the "speaker problem" extreme distortion (yes, it's less noticible at very low volume) actually be the reciever emitting screams of pain? As I posted earlier, I thought it was a speaker problem because the 8 ohm units that are part of my bargain surround speaker system sound fine. The receiver (cringe) is a Sony STR DE635. Don't flame me, I'm just off the boat (literally - I lived on a sailboat for the previous 15 years and my audio system was a marine version of a car stereo) and didn't know better when I bought it. So, if I assume the problem is more receiver than speaker (can I prove this somehow before laying out money for a better receiver?) what would you recommend? The price would have to be modest - say

 

[Drew Eckhardt]

Quote:

Originally posted by Morbius oldnacl, If you really want to turn your 4 ohm speakers into 8 ohm speakers - wire a 4 ohm resistor in series with one leg to the speakers. The amp will see an 8 ohm load.

The amp will see a load which varies with frequency. The attenuation will also vary with frequency. Assuming a 3 Ohm minimum impedance and 30 Ohm maximum, it will vary from -3.6dB to -.5dB. This will be audible.


You need transformers like these

Transformer


although stereo amps stable into 4 Ohms can be found for less.

 

[Larry Fine]

An amp that can't handle 4-ohm speakers, even at low volume, is struggling to do well with 8-ohm speakers. The power supply is obviously the limiting factor.


The price for those autotransformers is too much for the average mid-fi system. Plus, ther are electrical considerations. As with a standard 2-winding transformer, voltage and current vary inversely.


If you use a transformer to power a 4-ohm speaker from an 8-ohm-rated amp, sure you'll halve the current demand, but it will require twice the voltage, and that will assure clipping.


You really do need a better amp; one that at least has a 4-ohm rating.

 

[SimonStern]

Perhaps a Yamaha HTR-5760 if you want a new receiver? I am waiting on mine right now and it cost a little under $400, don't know if it does 4-ohms though

 

[ace5000]

NO

 

[oldnacl]

Well, darn. Those Nobis' are sweet speakers - I paid around $1000 for them in 197x, loaned them to friends while I was living on the boat and recovered them now that I'm back on land. I sure would like to use them but in my retirement, I can't really justify spending megabucks for a hign end receiver / amp to drive them. I don't even remember what amp I had back then, I think it was a Yamaha (or maybe an Alpine) that I bought from the same place I bought the speakers, but it also got recycled to friends and wasn't recovered, so I have to make do with my limited budget. I'm glad to get the responses anyway.

 

[timesnewroman]

There may be a way to salvage this situation cheap IF your receiver has preout RCA jacks. Obtain some funky old stereo receiver or integrated amp from the 70's or 80's (your closet, garage sale, ebay, thrift store) and use that to power your 4 ohm mains.