whatever55 Posted November 11, 2007 Share Posted November 11, 2007 Hello, I would like some opinions on 2 configurations... I have an MC252 and a pair of Belles and a pair of RF-7's What are the +'s or -'s of... connecting them in parallel and to the 4ohm post or in series and connecting them to the 16 ohm post. With autoformers I know thw power out stays about the same... but with one more current the other more voltage to achive the same watts. Please don't reply with try them both and decide... I am looking for reasons why to do one over the other. Or maybe it would not make a difference. Thanks Quote Link to comment Share on other sites More sharing options...
WMcD Posted November 11, 2007 Share Posted November 11, 2007 Putting them is series is not going to work properly, see below. Therefore you're stuck with parallel. I can't guarantee the amp will like that because I believe the impedance of both speaker models drops to 4 ohms. Therefore at some freq, you'll have a 2 ohm load. That is a real expensive amp to use as a gunea pig. The series problem is more difficult to explain. It arises from the fact that the input impedance curves of the Belle and RF-7 are almost certainly not likely to be identical. This is particularly so when you are looking into the crossovers, i.e. the situation at the normal input terminals. Thus when you wire them in series there is going to be a varying voltage drop across one or the other as frequency varies. E.g. at 600 Hz, the current through either is the same. Howevery if the impedance-resistance are not identical, the voltage drop will vary. Remember if you have two resistors in series, the voltage drop across a given resistor is proportional to the resistance. The exception to this series issue (but not the principle) is when two identical speakers (typically raw drivers) are hooked in series. When frequency varies, there is an identical voltage drop across either because their resistances, even if varying with frequency, are identical. This should also hold true at the input to the crossover, i.e. terminals, if you're looking at input to crossovers. There is one trick I saw long ago in an EV (?) publication. When hooking up two speakers to an amp with an output transformer . .. hook up one between C and 8 and the other between 8 and 16. I believe this is a bit flawed. I think the voltage delivered is not identical. Also, the varying speaker impedance (assuming they are not identical) will load the amp down, somewhat and make output uneven. I'd use this only if absolutely necessary, and with expendable equipment. Gil Quote Link to comment Share on other sites More sharing options...
whatever55 Posted November 12, 2007 Author Share Posted November 12, 2007 Update... I just got a reply from McIntosh and was told either way would be acceptable and would not harm the amp. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted November 12, 2007 Share Posted November 12, 2007 You might want to backup a little first. Gil offered some reasons why this might not be a good idea even if you could implement it. What is it that you are trying to accomplish, what is the end goal? -Tom Quote Link to comment Share on other sites More sharing options...
whatever55 Posted November 12, 2007 Author Share Posted November 12, 2007 Back up from where ??? I sent the same question to McIntosh and just posted their response for everyone to read and maybe comment... You might want to backup a little first. Gil offered some reasons why this might not be a good idea even if you could implement it. What is it that you are trying to accomplish, what is the end goal? Play all 4 speakers at the same time ????? -Tom Quote Link to comment Share on other sites More sharing options...
WMcD Posted November 12, 2007 Share Posted November 12, 2007 Hmm, BTW, I don't see a 252 on the Roger Russel website. Is that number correct? In any case, let me gripe. It seems like McIntosh gave you an okay for either, and you would not accept that sort of equi-vocal answer from us when you submitted the question! No fair, no fair, no fair. It is, though, good to hear that McIntosh believes their amp is that good. I did a little thinking since last night. It occurs to me that impedance is proportional to the square of the number of windings. Therefore, 0 implies a raw number of 0 4 implies a raw number of 2 8 implies a raw number of 2.828 16 implies a raw number of 4 Therefore the number of windings between 0 and 4 are the same as between 4 and 16. Voltage is proportional to the number of windings. Thus the relative voltage between these pairs are the same. My EV solution might work for you. You can, of course, do the parallel thing. I expect distortion might go up a bit. But maybe not too much. Gil Quote Link to comment Share on other sites More sharing options...
whatever55 Posted November 13, 2007 Author Share Posted November 13, 2007 Hmm, BTW, I don't see a 252 on the Roger Russel website. Is that number correct? http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=&id=14&cat=Power+Amplifiers&prodid=1055&product=MC252 In any case, let me gripe. It seems like McIntosh gave you an okay for either, and you would not accept that sort of equi-vocal answer from us when you submitted the question! No fair, no fair, no fair. I was looking for an answer... I got some... I thought it would be interesting to post what McIntosh said for everyone and to continue the discussion. It is, though, good to hear that McIntosh believes their amp is that good. I did a little thinking since last night. It occurs to me that impedance is proportional to the square of the number of windings. Therefore, 0 implies a raw number of 0 4 implies a raw number of 2 8 implies a raw number of 2.828 16 implies a raw number of 4 Therefore the number of windings between 0 and 4 are the same as between 4 and 16. Voltage is proportional to the number of windings. Thus the relative voltage between these pairs are the same. My EV solution might work for you. OK what is your EV solution I must have missed it. You can, of course, do the parallel thing. I expect distortion might go up a bit. But maybe not too much. Gil Thanks everyone... I did not mean to offend. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted November 13, 2007 Share Posted November 13, 2007 Back up from where ??? I sent the same question to McIntosh and just posted their response for everyone to read and maybe comment... You might want to backup a little first. Gil offered some reasons why this might not be a good idea even if you could implement it. What is it that you are trying to accomplish, what is the end goal? Play all 4 speakers at the same time ????? -Tom "Play all 4 speakers at the same time ?????" Well that is a good place to back up to. Yes, you have been given advice on how to implement this, but the question is whether you would want to. I will assume you specifically want to play all four speakers in the same room at the same time. If this is the case then some problems will occur (regardless of what effect it may have on your amp). The voicing will differ between the two pairs of speakers (Belles vs RF7s). This may not end up sounding very good. Are you setting up the speakers in each corner, or side-by-side or what? In addition to voicing issue, you will have lobing problems (the two sets of signals could, in effect, be creating a delay and add configuration). This will lead to comb filtering and can be quite audible and annoying. I am also not sure what the relative sensitivities of the 2 speakers are. If they are much different, you may end up "listening" mostly to the more efficient pair. Have you investigated what the two efficiencies are? So when I asked what your end goal was, that was not a trivial question. -Tom Quote Link to comment Share on other sites More sharing options...
WMcD Posted November 13, 2007 Share Posted November 13, 2007 Oh my gosh. I'm so used to looking at vintage McIntosh amps that I didn't even think of looking at their website Now I can see why McIntosh is not worried. Prreeety heavy duty. Also I see there are 2O output taps. Therefore, putting the speakers in parallel to there would be perfectly fine. Sorry for the oversight. Gil Quote Link to comment Share on other sites More sharing options...
whatever55 Posted November 15, 2007 Author Share Posted November 15, 2007 NO problem.... Thanks for the time and input. The speakers will be in the same room, Belles towards the center... the RF-7's on the outside. So far it sounds very nice... Thanks again Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted November 16, 2007 Share Posted November 16, 2007 NO problem.... Thanks for the time and input. The speakers will be in the same room, Belles towards the center... the RF-7's on the outside. So far it sounds very nice... Thanks again Okay now we understand what you are doing. I will stop after this since I think I am beating a dead horse. Gil and others have given you advice on how to implement such a scheme. However my friendly advice is that you may want to re-think what you are doing. You are mixing differnt types of speakers, this may not be a good idea. You are creating lobing by introducing additional sources that are covering a common area, this may not be a good idea. You are introducing additional sources that are no longer going to have the same path to the listener and thus creating phase and time delays. This is a recipe for comb filtering (which can be quite audible), this may not be a good idea. I have no doubt that the sound will be quite different than just using one pair of speakers. I also have no doubt that the accuracy of the reproduction has also been compromised. I expect the novelty of what you are now hearing will soon wear off, IMO. Good Luck, -Tom Quote Link to comment Share on other sites More sharing options...
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