jdm56 Posted October 30, 2005 Share Posted October 30, 2005 ...Is there a safe way to do it? I'm talking about driving 4 ohm speakers with a typical A/V receiver, most of which are not rated for 4 ohm loads. Would just putting a 4 ohm resistor in series with the speaker be an option? Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 30, 2005 Share Posted October 30, 2005 Putting a 4 ohm resistor in series with your loudspeaker will reduce the damping factor *significantly*. In other words, you can expect muddy bass. Quote Link to comment Share on other sites More sharing options...
jdm56 Posted October 30, 2005 Author Share Posted October 30, 2005 I figured there'd have to be a downside to such a simple fix, but I didn't know what it would be other than wasted amplifier power into the resistor. But...assuming the use of a separate powered sub for everything below 100Hz or so, would the reduced damping factor still be an issue? Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 30, 2005 Share Posted October 30, 2005 Or you could just not turn up the volume dial all the way [] Seriously though, the reason for the 8 ohm limit is because twice the amount of current flows into a 4 ohm load. If you wanted to find the limits of your reciever, plug in an 8 ohm speaker with the same sensitivity as your 4 ohm speaker. Measure the max SPL (where the amp starts to clip) and then switch to the 4 ohm speaker and don't ever go above the SPL u just measured. In other words, don't tell the reciever to output more current than it is capable of providing (this silly little test is just a way to figure out the limits). Also, the 8 ohm rating for a speaker is a nominal level. The actual impedance at a specific frequency can be anywhere between 2 and 400 ohms! If your 4 ohm speaker doesn't dip much lower then you should be just fine with your reciever. So I guess more specifically...what 4 ohm speaker are you looking to hook up to what reciever? Quote Link to comment Share on other sites More sharing options...
jdm56 Posted October 31, 2005 Author Share Posted October 31, 2005 I bought three ADS HT400LCR's to use accross the front. They are 8 ohm, so no problem, BUT, I would like to possibly use the ADS HT300's in back, and they are 4 ohm. My receiver, is a Pioneer Elite VSX-55TXi, and is not specifically rated for 4 ohm loads, although it does have a switchable 6/8 ohm operating mode. -Not sure what is happening in the different modes. I'm thinking I might be able to get by with using four of the 4 ohm speakers as surrounds because they aren't really doing THAT much most of the time, but I'm just a little leary of it. Just fyi, the ADS HT400LCR's are pictured in my avatar. They are about 16"x7"x10" (HxWxD)and weigh a healthy 39 pounds each. They use steel and aluminum enclosures, with a pair of 5 1/4" mid-woofers and a 1" dome tweeter. The HT300's are the samedesign, except they use just one mid-woofer and the box is shorter. They weigh 20 pounds each. Quote Link to comment Share on other sites More sharing options...
ironwoods Posted October 31, 2005 Share Posted October 31, 2005 I'm thinking I might be able to get by with using four of the 4 ohm speakers as surrounds I'm not sure if you mean in a 7/6.1 configuration, but if you use them in 5.1, you can run a pair in series, and you'll achieve the 8 ohm load. You wouldn't be having this dilema if you were to use Klipsch brand speakers. [] Quote Link to comment Share on other sites More sharing options...
jdm56 Posted October 31, 2005 Author Share Posted October 31, 2005 7.1 is the configuration I'm doing. Currently I use these little Radio Shack Minimus 77's which are cheap imitations of ADS L310's. The RatShack jobs are 8 ohm though, so there is no problem there (other than the cheap drivers and cross-over[:$]). I may just stay with them for the time being - they actually do a pretty decent job for surround duty. I am always tempted though, to have everything matching, ya know? The ADS 400's are incredible for their small size and cost, and the 300's would be a natural for the surround positions, other than the low impedence. I could use 400's all around, but that seems like overkill. Maybe I should use just two and limit it to 5.1 - that's not a bad option. Those two back surrounds seem to me not too needful, really. I guess it depends on the room and set-up. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted October 31, 2005 Share Posted October 31, 2005 Unless you have an especially WIERD amplifier (which I doubt), almost all modern direct-coupled transister output stages are designed for and are capable of supporting both 4 or 8 ohms interchangably without any problems whatsoever. Considering that no speaker actually presents either a true 4 or 8 Ohm impedance to the amp, it is a tempest in a teapot, anyway. DM Quote Link to comment Share on other sites More sharing options...
JohnA Posted October 31, 2005 Share Posted October 31, 2005 As stated, it will not be a big deal, just do it. The real problem is heat generated by the higher current flow allowed by the low impedance speakers. Limit the heat by controlling the loudness or by ensuring there is plenty of cooling and the receiver will be fine. Quote Link to comment Share on other sites More sharing options...
jdm56 Posted November 1, 2005 Author Share Posted November 1, 2005 Thanks for the advice, guys. I appreciate it. Damn the low impedance, and full speed ahead! Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 1, 2005 Share Posted November 1, 2005 "Damn the low impedance, and full speed ahead!" You might want to rethink that, unless you really don't like your gear. Unless it is rated to do so, I would not attempt it. Kinda like driving your car to work in first gear, at the redline. Read this: http://forums.klipsch.com/forums/627398/ShowPost.aspx Quote Link to comment Share on other sites More sharing options...
jdm56 Posted November 1, 2005 Author Share Posted November 1, 2005 "Damn the low impedance, and full speed ahead!" You might want to rethink that, unless you really don't like your gear. Unless it is rated to do so, I would not attempt it. Kinda like driving your car to work in first gear, at the redline. Read this: http://forums.klipsch.com/forums/627398/ShowPost.aspx party-pooper![*-)] Quote Link to comment Share on other sites More sharing options...
psg Posted November 1, 2005 Share Posted November 1, 2005 NAD receivers are rated for 4 ohms (perhaps even down to 2 ohms). h/k receivers are not technically rated for 4 ohms in the manual, but they are "high current" and are regularly tested to 4 ohms in reviews. I tried my h/k avr-325 on a friend's 4-ohm nominal speakers because he had no dynamics at all with an Onkyo (not rated for 4 ohms) and it sounded fantastic in comparison. He bought a NAD to solve his problems. It sounds good but suffers some software glitches and he needs to reset it once in a while. Quote Link to comment Share on other sites More sharing options...
jdm56 Posted November 1, 2005 Author Share Posted November 1, 2005 I think my receiver (Pioneer Elite 55TXi) could probably handle the load, at least on the surrounds. I drove the B&W 703's with it for awhile and had no problems. They are actually rated as an 8 ohm speaker, but according to tests, they actually dip down close to 3 ohms in the bass. Quote Link to comment Share on other sites More sharing options...
sivadselim Posted November 1, 2005 Share Posted November 1, 2005 my denon 3803 has pushed 5 4ohm speakers with no problems whatsoever. i think it will depend upon the receiver. some are more robust than others. what manufacturer? Quote Link to comment Share on other sites More sharing options...
jdm56 Posted November 1, 2005 Author Share Posted November 1, 2005 Pioneer Elite VSX-55TXi (7 channel) Quote Link to comment Share on other sites More sharing options...
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