4 ohms højtalere - recordere.dk forum

Thomas...c skrev:

Kan du så ikke forklare hvad du mener med et ringere resultat ?

At der mangler de sidste 25% effekt ?

Giver det et ringere resultat, at køre med tre tændrør, når motoren har fire cylindre?

Sony 65 A1 Oppo UDP 203
MICHI S5 MICHI P5 Mark Levinson No 5101
Rega P8 Apheta3
Aria MK3 RIAA
Dynaudio Confidence 50
Denon X6200W Dali Mentor 6 Mentor Vokal Fazon Sat KEF TDM 34DS B&W ASW650

Q: How do I connect a set of four ohm speakers safely to an eight ohm system?

A: There are many variables to consider when connecting 4 ohm speakers to your system. Please consider the following:

Define your system

Are you using a Receiver or separate power amp to drive your speakers?

Receivers: Most midfi Receivers may have problems adequately driving a 4 ohm load. However, many of the better Receivers today have a large enough power supply, heat sink area, and current capability in the amp sections to handle 4 ohm loads. You are usually safe running these speakers on the Flagship Receiver models from: {Yamaha, Denon, Onkyo, Harman Kardon, NAD, Nakamichi).

NOTE: Some Receivers have an impedance selector switch. In most cases we recommend the 8-ohm or more setting. The manufacturer puts them there for UL/CSA approvals as well as easing consumer concerns about driving low impedance loads. These switches step down voltage feed to the power sections which will limit dynamics and overall fidelity. Keep the switch set for 8 ohms regardless of the impedance of your speakers and ensure proper ventilation of the Receiver.

For a detailed explanation on how to set the impedance switch on your receiver, read: Setting the AV Receiver Impedance Switch

Upon further investigation on this topic we have discovered that in most cases the switch is doing nothing more than reducing the rail voltage. Please check out our measurements on page 2 of the Yamaha R-XV4600 review for more information on this.

As you can see the measurement differences between the "low" setting (less than 8 ohms) and the "High" setting (8 ohms or more). This is the reason I usually recommend keeping this switch in its default "High" setting and using common sense when mating a receiver with inefficient 4 ohm speakers in large rooms.

All the "Low" setting of the switch is doing is stepping the rail voltage down so when UL tests the amp at a specified distortion level, the amp will achieve that distortion level sooner since it runs out of headroom more quickly than it would in the "High" (8 ohm or more) setting. This in turn generates less heat since the amp isn't driven as hard. You really aren't buying any protection for driving low impedance loads as you actually risk clipping the amplifier more since it can run out of headroom more easily. The switch is there more for certification purposes.

The reason you don't see this switch on separate amps is twofold:
• They typically have more heat sink area, and bigger power supplies and can better manage the heat
• They aren't UL certified and don't have to meet the requirement.

Så omskiftningsmuligheden er der reelt set, for at kunne UL/CSA godkendes, i USA.

M.v.h.


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