BillH2121 Posted February 20, 2005 Share Posted February 20, 2005 OK - I spent a little time yesterday playing with the different taps on my Mac 2125. It's easy to change on the Macs - just loosen a screw and insert the lead on 2, 4, 8, or 16 ohm taps. When I went to 4 ohms, I didn't notice a marked difference although it seemed that there was more articulation in the bass. I played several jazz LPs that have accoustic bass and it seemed as if I could hear the attack on the bass notes more clearly. My wife, who has much better hearing than me, thought the vocals were more clear. I thought maybe the soundstage opened a little. Went to 2 ohms next. I didn't lose any of the bass improvement and it seemed that the sound stage opened way up and the midrange sounded fat. The high end remained clear and precise. However, when I listened to some Little Feat cranked up to my usual auditorium-level dbs, I had to turn the volume knob to almost 3 o'clock as opposed to the ususal 12 o'clock. I can remedy that by switching the input level on my Mac from 2.5 volts to .75. However, I am hesitant to do that as my manual recommends 2.5 with all Mac sources, such as my C-26, for best signal to noise ratio. SO - I'm back at 4 ohms and I think the overall sound is better. Or, is it the power of suggestion from previous posts and what I think I want to hear?? One thing, I know there's no degradation in sound quality resulting from the change from 8 to 4 ohms, so for now the leads remaind hooked to the 4 ohm taps. I'm interested in hearing from others with SS gear and if they think there's any change in sound between 8, 4, or 2 ohms. Quote Link to comment Share on other sites More sharing options...
leok Posted February 20, 2005 Share Posted February 20, 2005 BillH2121, Keeping the sensitivity down on your amp is more a factor if you're not using the range (which would be the case if the volume control was always at something like 9:00 for loud). If you need more range, I'd suggest you use it. For that matter, running with a volume control wide open sometimes gives you the best s/n and lowest distortion. Anyway, in your case, the two alternatives are splitting hairs. If 2 Ohms sounds better (and I'd expect it to) I'd use it. You might consider adding a 10 to 15 Ohm (22 to 33 Ohm if you use the 4 Ohm tap) 10W resistor across the speaker terminals in parallel with the speaker. This will further reduce interaction between speaker impedance and your amp. Leo Quote Link to comment Share on other sites More sharing options...
BillH2121 Posted February 20, 2005 Share Posted February 20, 2005 OK Leo, I'm switching back to 2 ohms and I'll spend the day listening. I don't have alot of experience comparing audio systems, components, etc, so I can't really engage in the kind of esoteric discussion re desciption of sound of which others are capable (analagous to wine to me - some taste good, others don't - I've never really experienced "robust fruitiness with a hint of leather"!!). However, with the change to 2 ohms I definately noticed a difference in the bass response, vocals, and what seemed to be a much more expansive soundstage. I listen primarily to jazz LPs at moderate loudness levels, so the volume thing is probably not that big of a deal when I think about it. Are you saying though that even if I feel a need to change input sensitivity to .75 that I won't notice a change in overall sound quality? Thanks Quote Link to comment Share on other sites More sharing options...
leok Posted February 20, 2005 Share Posted February 20, 2005 Bill, The two sensitivity settings will probably sound the same. There can be small technical arguements going either way depending on details of your amp and preamp. In either case, it sounds like you're close to optimized. Leo Quote Link to comment Share on other sites More sharing options...
organ Posted February 21, 2005 Share Posted February 21, 2005 Doctor, The sound is excellent. I still haven't had time to listen loud but tomorrow I will crank them up. Hope the bass stays as strong and dynamic as they do at lower volumes. It's too bad we can't find an impedance graph of the RF-35 anywhere. Congrats on the amp. Sounds like a good deal you got there. Enjoy the new toy. Maurice Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted February 21, 2005 Share Posted February 21, 2005 A little off topic but yesterday, at Andys house, I had my amp running on the 4 ohm taps to drive his mighty Khorns. The bass was clean and tight, mids were sweet and the highs were clean and crisp. I hava a set of Forte 1s that I normaly drive with the amp and they are labled on the speakers as 4 ohm but listed here on the website as 8 ohm. I like the sound better at 4 ohm and as it takes a soldering iron to change the taps, they stayed on 4 ohm at Andys house. Quote Link to comment Share on other sites More sharing options...
Deang Posted February 21, 2005 Share Posted February 21, 2005 With reactive networks, I prefer the use of the swamping resistor hands down. By the way, I noticed Andy is using ALKs on his Klipschorns. All amps connected to this network should be wired to the 8 ohm taps. The network is a true multiplexer providing constant load impedance to the amplifier. The amplifier sees the speaker drivers, not the network! With the woofer and tweeter outputs terminated in 8 Ohms and the squawker output terminated by 13 Ohms, the input polar impedance to the network is approximately 8 Ohms +-1 Ohm at +-10 degrees from 20 Hz to 20 KHz. Quote Link to comment Share on other sites More sharing options...
doctorcilantro Posted February 21, 2005 Share Posted February 21, 2005 ORgan - no impedance graph for the RF-35? Not in the specs? Maybe we can ask Trey or Dean ; )could ask since he has a repoire with him. I am going finish this CC89259 speaker cable and biwire at some point. Right now I am using the 4ohm tap. New amps so it's hard to discern what's going on as it all sounds so good. Once I get the new preamp and cables done I'll switch between 8 & 4 and see what happens. Glad it's sounding good for you all....and ORGAN>>>>>CRANK IT UP! DC Quote Link to comment Share on other sites More sharing options...
organ Posted February 21, 2005 Share Posted February 21, 2005 Doctor, Oh yeah, it's CRANKED and I'm loving it . I got to pump them up earlier today when the parents were out and the sound is incredible. Much more effortless, deeper and more powerful bass with excellent control. The soundstage actually improved and the mids sounds a lot cleaner at high volumes. I swear it feels like the amp has so much more power now. Let me know how your bi-wire cables go. I haven't tried bi-wiring yet. Just using 16ga M*nster right now. I plan to go 12ga in the future. Looks like you're going to be very busy (in a good audio kind of way). Enjoy! Maurice Quote Link to comment Share on other sites More sharing options...
doctorcilantro Posted February 26, 2005 Share Posted February 26, 2005 What about the RF-7's at 4 ohms. Is this okay to try? Organ, I have some Monster cable I may nnot need if you want it for Bi-wiring. Let me check how long it is and you can have it for the ship cost. Dr. C Quote Link to comment Share on other sites More sharing options...
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