4ohm loads and Vintage Marantz 22xx Receivers

[_tk]

I know a lot of people in here like to run older era-correct speakers with their receivers, but I was wondering how the old units handle modern 4ohm speakers. Specifically, either my (restored) 2265b or 2285b might be hooked to a new pair of 4ohm bookshelf speakers in the near future,

I've ran modern 6ohm speakers on them with no sweat and I think they sound really, really good. Just have not tried any modern 4ohm speakers on them.

 

[Mike Sweeney]

They call out 4 ohm loads in their data sheets. This is from the owners manual for the 2245 Marantz. Make sure your cooling is up to spec. And frankly, I'd be cautious if the output transistors are the OEM at 40 + years old with an unknown history. This is assuming running vintage speakers that take a fair bit of power vs newer speakers which tend to be more efficient ( at the cost of sound I'm told) and if you are really cranking things up. New transistors I'd happily beat on

 

[_tk]

Yeah, I know they rate them for 4ohm loads (my 2285B is rated for 110wpc @ 4ohms). I just didn't know if people were having luck and/or issues when driving these types of loads.

My "cooling" is the receiver in a wooden case (with the original metal case removed), so probably better than just the original metal case alone.

Definitely not going to be "party" speakers, but I may crank it up a little on certain occasions. My favorite listening method is low-to-moderate volume with the loudness button on and the bass a click or two to the positive.

 

[Mike Sweeney]

Well, I can say at 8 ohms, 1/3 volume at loudness enabled, my 2245 transistors run 85 degrees F all day long. I tend to run heavy bass I don't have any 4 ohm speakers but I do have some big-assed 4-8 ohm resistors handy.. I'll hook them up tomorrow and let it bake for an hour or so at 4 ohms and 1/3 to half volume.. just to see

 

[Dudeman7]

I've been running 4 ohm CV's with my 2245 for years.

Never had issues, amp stays cool and sounds great.

 

[_tk]

Yeah, I absolutely love the bass these receivers can put out and I exercise that aspect of them quite a bit. New receivers just don't seem to have that same quality.

Good to know that 4ohm is a possibility and I'll be anxious to see how hot the transistors run. Even on my 2285B, temps seem to be somewhat the same regardless of volume level. It's a pretty composed receiver.

 

[spicer]

I've seen many such units... Marantz, Pioneer, Kenwood, Sony, Sansui... from that time period running two sets of eight ohm speakers at high volume for hours without a problem. Many people stacked speakers such as Advent and ran them for hours assuming the amp meant it when it said four to eight ohm speaker loads. This would assume bias is properly set, not overly high, which I'm sure was the case since these units were not old at the time. If anything you might check how hot the metal of the case is above the output heat sinks after five or ten minutes of playing at high volume. It can get nice and warm but should not feel like it is getting hot. Allow room for ventilation.

 

[tranguru]

if the amp is OK - then you should be OK.
if not then it will blowup no matter what - just a bit faster than with 8ohms.

 

[Mike Sweeney]

So I got my coffee and wandered to the bench this AM while the new apple watch was updating.. what else am I gonna do? put up Xmas lights?

Anyways.. 2245 that has fully restored amp boards and mostly restored tone board ( waiting on transistors), new filter caps, restore PS. So it's in fairly good shape right now.

4 ohm 400 watt resistor loads on speaker A set
1/2 rotation of volume control.. thats a bit more than 1/2 volume since it's not a full 360 degrees for the rotation of the pot.
1/2 hour of running.. ambient air is 72 degrees
power draw at 118 VAC is .75 amps and 65 watts
Left channel transistors are 103 degrees
Right channel transistors are 100 degrees

The bias is a bit off since I adjusted them out of the chassis and now they are in the chassis. But it's not off by much.. both are under 5 mV right now

The power supply board in one corner where the caps are hits about 100 degrees. I had left the OEM diodes but I think I'm going to change them out given how beat up this unit was.

Anyways.. 4 ohm load works pretty well. I'd be cautious in the middle of summer with a non-ac room if it's hitting 90 degrees ambient or so.

 

[_tk]

Again, thanks for the benchtesting--much appreciated. My units only live in a climate controlled area (with nothing stacked on top of them) so I hopefully don't see heat being an issue.

I'll probably be ordering up those 4ohm speakers after all!