4 Ohm 8 Ohm Switch?

[Keith H]

Just received a mint Sony STR-V444ES receiver and i am hooking up a pair of 4 Ohm front speakers with a sensitivity rating of 104db.Question,should i leave the impeadence switch set at 8 Ohm so the receiver delivers more power or be safe and switch it to the 4 Ohm position?Thanks for any help,Keith..

 

[whoaru99]

IMO, 8.

I had a Sony receiver (STR-G3) with a 4/8 Ohm switch and ran Cerwin Vega D9s (4 ohms, 101dB) for years on the 8 Ohm setting with no problems. I still have the Cerwins, but gave away the Sony and know that it's still working fine - well, as fine as it normally worked, that is (neat, but POS VisionTouch egg remote).

With 104dB sensitivity you likely won't be using much power, but just leave it plenty of ventilation anyway. The STR-G3 ran fairly warm/hot as normal course anyway, as do many AVR/HT receivers due to all the added processing boards, etc.

I couldn't tell any difference at low volume, but when I put the pedal to the metal, I could really tell the 4 ohm setting limited the receiver.

 

[bastek]

My Yamaha DSP-A1 has a 4/8 ohm switch. My amp. never gets too hot in either setting (i never saw the little fan turning). The 4 ohm setting is limiting the voltage to the power output transistors by 30-40% (from 60V to 45 V in my case), to prevent overheating. This is limiting dynamic range and power output. Even so, i could swear the 4 ohm setting sounds more sweet and natural to me. But i rarely hit 12 o'clock on the volume knob. I need to do some more testing on high output levels.

 

[cademan]

You actually get more power using 4 ohms. Phase linear model 400, series two spec says, 260WPC @ 8 ohms, 360WPC @ 4 ohms.

 

[whoaru99]

You actually get more power using 4 ohms. Phase linear model 400, series two spec says, 260WPC @ 8 ohms, 360WPC @ 4 ohms.

Yes, if the speaker is 4 ohms generally the receiver will deliver more power.

However, that's not the same as using the 4/8 ohm switch on the receiver. The 4/8 ohm switch on the receiver puts additional voltage/current limiting circuitry into play when in the 4 ohm position. This is done so that the amplifer doesn't get as hot when using 4 ohm speakers.

The downside, as I mentioned, is that the amp doesn't perform as well in the 4 ohm setting.

 

[outshined]

My Yamaha DSP-A1 has a 4/8 ohm switch. My amp. never gets too hot in either setting (i never saw the little fan turning). The 4 ohm setting is limiting the voltage to the power output transistors by 30-40% (from 60V to 45 V in my case), to prevent overheating. This is limiting dynamic range and power output. Even so, i could swear the 4 ohm setting sounds more sweet and natural to me. But i rarely hit 12 o'clock on the volume knob. I need to do some more testing on high output levels.

I have a DSP-A1. I use the preouts on all channels driving outboard amps.
I have not seen a fan in the A1... nor does the manual make any mention of a fan. Am I mistaken? (My A1 was purchased new in '96.)

 

[bastek]

The fan is in the middle of the amp. above the huge caps and transformer. Looking from the top, is next to the left heat sink, and in front of the big transformer. You can see the fins with a bright flashlight. The DSP-A1 is a great amp., even for two channels.

 

[outshined]

Thanks, bastek. Good to know, especially if I use the A1 without external amps. I was always concerned about heat using the A1's amps and 4 Ohm speaks. Although, the outboard amps will deliver much more power into low impedances.

 

[johnda]

In the early days I had a Harmon Kardon Award tube amp with 3 settings 4,8,16 ohms. I changed the settings to match the rating of the speakers I was using. I would suggest that with 4 ohm speakers you use the 4 ohm setting. I really wonder what someone would do if they have Warfdale 9.5 tower speakers which have a 6 ohm setting.

 

[whoaru99]

With tube amps it's a completely different thing, IMO. In that case, you're actually matching the characteristics of the output transformer to the speaker, generally to improve the sound and power transfer.

In the case of solid state amps it's not doing that, it merely puts additional limiting on the amp output stages which, from my experience, hurts the sound.

The switch isn't there for anything to do with sound, per se, it's there to allow the amp to pass UL approvals.

Check this out.

 

[johnda]

Thanks for that link, it was very interesting! Gosh, you learn something new every day! So, the message is "Use the 8 ohm setting for everything, and let the devil take the hindmost."