the 4 ohm rating

Samadhi Acoustics offers an excellent full range speaker (28hz up) rated at 94db and 4 ohms. A custom interstage transformer coupled SET 300b with 7 watts can drive these speakers with ease. The transformers are custom wound Electraprint and designed for 4 ohm loads.

There is an excellent article on 4 ohm and 8 ohm speakers on Roger Russell's McIntosh history website. Here is what it says:

Impedance of Home Systems is Changed To 4 Ohms

All systems manufactured prior to 1993 are 8 ohms and have an industry standard sensitivity rating of 1 watt into 8 ohms at a distance of 1 meter. All systems made after this date are 4 ohms and have a sensitivity rating of 2.83 volts into 4 ohms. This turns out to be 2 watts into 4 ohms, making them appear to have greater sensitivity. To convert to a 1-watt level, subtract 3 dB from the rated sensitivity. For example: the LS350 is a 4-ohm system rated at 89dB for 2.83 volts. This converts to the industry standard rating of 86dB for 1 watt at a distance of 1 meter.

Generally, a 4 ohm speaker will play louder on a direct coupled amplifier than an 8 ohm speaker simply because it draws twice the power with the lower impedance. A few companies have used this strategy for many years. The idea is that when a simple switch arrangement is used in a dealer store to compare different speakers, the louder one is supposed to be the one that gets the sales—and this does help.

Reducing the speaker impedance to 4 ohms does not improve the accuracy of the speaker, reduce distortion or make any other improvements. However, it does create problems for the customer. It means that the customer must purchase heavier speaker wire to maintain the same low losses compared to the earlier 8-ohm speakers. The total DC resistance of the wire must now be less than 0.4 ohms instead of 0.8 ohms. It also requires better connectors at the speaker and amplifier terminals to make the contact resistance even lower.

ok guys,ive read all the responses & all of them were well writen but there wasnt anything that really answers my question.

most of the responses went on to further puzzle me as to why people choose 4 ohm gear when by the statements written in the responses 4 ohms looks even more like a drawback to me then ever before.

if by having your amp running in 4 ohms uses more current to run at that wattage isnt that current being drawn from the power supply(wall outlet)& isnt the increased current being drawn making the supply weaker creating the need for dedicated lines,power conditioners & beefier power cords & custom cabling.

also as C123666 pointed out with his article that running 4 ohm speakers dose not improve a speakers accuracy,reduce distortion or make improvements in any other area other than playing louder but then requires the use of heavier wiring & better connections at the amp isnt that a drawback.

im not saying that 4 ohm gear dosent sound as good or even better than 8 ohm gear but from everything i see & read is that 4 ohm gear requires alot more aftermarket products to let it reach its full potential.

once again this wasnt an attack on 4 ohm gear but i clearly see multiple drawbacks that not only shorten the life of amps but require more cash to be spent to reach top performance.

mike.

Mike,
I didn't take it as an attack. Yes, I know speaker manufacturers make speakers with 4 ohm ratings to make their 'sensitivity' ratings look better. Yes, I know that my 90db 4 ohm speakers would be just 87 db at 8 ohms.
I've never had a problem when running 4 ohm speakers though. I guess if I wanted to run a tube amp I might. However, I can't say that I've ever made any changes in my system because I have 4 ohm speakers. My power cords on my front end equipment are thicker than my speaker cables. I've long been a fan of dedicated power lines and conditioners, regardless of speaker design.

The only drawback that I've ever thought of is running tube amps. I've never tried a tube amp yet. I would probably just get a pair of Paul Speltz's Zero's to let the amps 'see' my speakers as an 8, 12, or 16 ohm load should I ever decide to try a tube amp. I can't say that I've ever given a moments thought to buy anything because my speakers were 4 ohm (aside from tube amps). I actually bought my M100's because I liked the way that they sounded. It was afterward I found out that they love 4 ohm loads.

I would have had dedicated lines run and bought my Shunyata Hydra, etc. no matter what speakers I had.

I don't know if this helps or not. I don't know if a system (amps, wires, etc) would work harder on my 90db 4ohm speakers than it would on a 87db 8ohm speaker. If playing at 100db, what does it matter if my amp is putting out 10 watts into 8 ohms or 20 watts into 4 ohms? Both speakers would be outputting a 100db signal. Maybe someone else can answer this.
The only way I could see this affecting the amp would be if the amp doesn't 'double down'. As most high end soild state amps do, I would guess that unless using a tube amp or receiver, it wouldn't be a factor at all. If using a tube amp, it may require an additional investment of $450 for Paul's Auto-formers. That doesn't seem like much money compared to what many folks here spend. Especially since the Zero's can also replace your speaker cables.

Does this help at all? Or am I not understanding what you're trying to say?

Cheers,
John

John I'm with you totally. However, even using tube amp on 4ohm speakers are not much problem at all. I'd rather have flat 4ohm speakers than 8ohm speakers deep down below 4ohm. My BSL Type II is 4ohm with 102db with very flat responce. So it needs 1watt to do 99db and 2watts to do 102db driven by Mothe Si2A3 (3 watt SET). No problem at all. My Melior One is 4ohm (very flat) with 87DB and I use them with Bel Canto SET40 (40watt single ended triode). Again, no problem what so ever. Both my speakers don't have x-over so I gain back 3db at least. Many ways to skin a cat.

A speaker voice coil has inductance as well as resistance. An 8 ohm coil, in order to produce the same force from less current must have more turns...twice as many. This means twice the inductance. Not good.

Magneplanar speakers don't have voice coils. The wires that move the diaphram are glued on flat, so there is little inductance, and that makes Maggies an easy load for the amp to drive, although they do benefit from lots of power.

Some drivers are made with a split voice coil ...essentially two coils at say 8 ohms each. You can hook them up in parallel or in series, and have a 4 ohm or a 16 ohm driver. It has almost no effect on the way the driver works. The choice is made based on how the driver is used with others in a system.