Owen Posted June 3, 2011 Share Posted June 3, 2011 TC say that their RH heads will run 3 of their 8 ohm cabs safely. That is 2 ohms. But they cannot guarantee that it will run down to 2 ohms with anyone else's cabs. Would there be anything clever that they will be doing to their cabs to make it guaranteed to be 2 ohms? They say that they can only guarantee 2ohms with their own cabs. Is this marketing spiel? Quote Link to comment Share on other sites More sharing options...
henry norton Posted June 3, 2011 Share Posted June 3, 2011 2 reasons. One, they can't guarantee the impedance of another manufacturers cabinets and two, they want you to buy theirs Both these add up to a third, saying they produce fantastically consistent speakers, high quality speakers will perform at their very best only when used in conjunction with one of their very own amplifiers in a perfect combination. Whether you believe any of it is another thing though.... Quote Link to comment Share on other sites More sharing options...
BB3000S Posted June 3, 2011 Share Posted June 3, 2011 Isn't three 8 ohm cabs more like 2.67 ohms? Quote Link to comment Share on other sites More sharing options...
stevie Posted June 3, 2011 Share Posted June 3, 2011 There was a thread about this a while back. This is marketing guff and I'd like to see somebody prove otherwise. If the amps are 2- or 3-ohm capable, TC should say so. Instead, they make their customers think they are doing something "clever" with their cabs but are in fact simply misleading them to flog them more product. I have a TC amp, but this lack of transparency (ahem!) does not endear me to the company. By the way, three 8-ohm cabs isn't 2 ohms, although a member here has confirmed that the amp handles a 2-ohm load OK. Quote Link to comment Share on other sites More sharing options...
Lfalex v1.1 Posted June 3, 2011 Share Posted June 3, 2011 There might be a bit of truth to TC's spiel... Drivers/Loudspeaker systems' impedance is not fixed. It varies with frequency. If you plot a graph of frequency (horizontal axis) against Impedance (vertical axis), the resulting trace (no pun intended) describes the system's modulus of impedance. This shows how much the demand on the driving amp changes in a real-world setting. The figures quoted on cabinets for reference (4 ohm, 8 ohm etc.) are Nominal impedance figures. I presume that the TC cabinets' impedance does not present too varied a load in its various combinations. They're not likely to research all the other alternatives from other manufacturers... Quote Link to comment Share on other sites More sharing options...
mart Posted June 4, 2011 Share Posted June 4, 2011 [quote name='stevie' post='1256020' date='Jun 3 2011, 10:19 PM']There was a thread about this a while back. ....[/quote] Here are two threads, and I'm sure there's at least one other - I recall Mark from Bass Direct chipping in with some thoughts. [url="http://basschat.co.uk/index.php?showtopic=103342&hl=TC+ohm"]http://basschat.co.uk/index.php?showtopic=...2&hl=TC+ohm[/url] [url="http://basschat.co.uk/index.php?showtopic=129239&hl=TC%20ohm&st=0"]http://basschat.co.uk/index.php?showtopic=...%20ohm&st=0[/url] Quote Link to comment Share on other sites More sharing options...
Owen Posted June 4, 2011 Author Share Posted June 4, 2011 Rats, I had actually trawled but but was looking for 750 info so missed both those threads. How embarrassing. The fact that I cannot make 8+8+8 = 2.67 tells you all you need to know about my enhanced knowledge of impedance. I just fancy pairing an RH750 with a couple of 4 ohm ACME 12" cabs. My gut feeling is that it should be ok. Quote Link to comment Share on other sites More sharing options...
mart Posted June 4, 2011 Share Posted June 4, 2011 Three 8 ohm loads in parallel is indeed 2.67 ohms: one way to think about this is that the current through each load is inversely proportional to the impedance, so an 8 ohm cab takes 1/8th the current of a 1 ohm load. Now if you've got 3 of those cabs, and you can just add up the current going through each, so that's 3/8ths (1/8 + 1/8 + 1/8). Which is the same as if you had one 8/3rds-ohm cab. And 8/3 is 2.67. And that's why each 4 ohm cab draws 1/4th of the current of a 1 ohm cab, so 2 of them draw 2/4ths, i.e., 1/2 the current, which is the same as a 2 ohm load. So two 4 ohm cabs is a lower impedance than three 8 ohm cabs. My reading of all this stuff about TC cabs is that they know the properties of their cabs, know the tolerances, and know that their heads will cope with the exact current 3 of their cabs will draw. I wouldn't be brave enough to conclude that if TC have confirmed that their head will work with the (notionally 2.67ohm) load of three of their cabs, that it will be ok with a load that is notionally 2ohm (but may be less if these particular speaker cabs behave differently from the TC ones, and less means more in that less ohms means more current means more chance of your head going phut). Your call! Quote Link to comment Share on other sites More sharing options...
stevie Posted June 5, 2011 Share Posted June 5, 2011 If the TC amps work with 3 x TC 8-ohm cabs, there is no reason why they shouldn't work with 3 of anybody's 8-ohm cabs as long as they adhere to accepted specification standards. Amplifier manufacturers don't have to test everybody's cabs to provide a minimum load impedance. This is a complete red herring dreamt up by TC's department of propaganda and disinformation, aka the marketing department. Mark's test showed that the amp is likely to be 2-ohm-capable. It would certainly be useful to have the correct information from the manufacturer. Quote Link to comment Share on other sites More sharing options...
chris_b Posted June 5, 2011 Share Posted June 5, 2011 [quote name='stevie' post='1257377' date='Jun 5 2011, 03:03 PM']....Amplifier manufacturers don't have to test everybody's cabs to provide a minimum load impedance. This is a complete red herring dreamt up by TC's department of propaganda and disinformation, aka the marketing department.... It would certainly be useful to have the correct information from the manufacturer....[/quote] +1 Quote Link to comment Share on other sites More sharing options...
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