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  1. Thorne, what you describe is bi-wiring and the "benefits" of doing this are frequently debated. When you select both sets of speakers on the Fisher, that selector switch inside the Fisher applies exactly the same signal to both of Fisher's speaker output terminals. In this case, you can connect the return speaker lines together at speaker terminal 1. The advantage of doing this is you can select (via the Fisher selector switch) to listen to the woofers or the mids/tweeters or both. When you leave that lead dangling (not connected), you cannot select to listen the mids/ tweeters alone. Again, you may connect this way when bi-wiring (that is using a single amp). You should not connect this way when bi-amping unless both amps are of the common ground design. Regards, Jerry
  2. Thorne, the switch description means nothing. Post the circuit diagram. Most of these devices are designed for modern amps.
  3. A common ground amp has the high level speaker output (red speaker output terminal) referenced to a common ground that is consistent throughout the entire chassis of the unit. This means both black speaker output terminals are always at the same potential all of the time. Your Fisher has output transformers (one for each channel) and neither of these outputs are connected to the output of the other channel. They are isolated from each other and should never be connected together. Hope this helps.. Jerry
  4. Perhaps, Thorne, you should review your pics in your 2nd post in this thread. (The pics with the dangling com lead.) My comments were in reference to that post and those pics. Now, as for your TC-905B, do you have a schematic for this thing? From what I can find, it has a headphone jack. Headphone jacks (that is the standard 3 connector 1/4 inch plug) are designed for common ground amps. Your Fisher is NOT a common ground amp and you could damage that old unit connecting to a switch not designed for it. Regards, Jerry
  5. Well, if you are running two amps EACH WITH ITS OWN VOLUME CONTROL, you are by definition bi-amping. There is a huge difference between bi-amping and bi-wiring. With bi-amping you gain voice control, because you can vary power sent to each speaker half. Bi-wiring has absolutely no provisions for doing this. I am well aware that your Marantz is a solid state common ground amp. Remember I instructed you to turn on the Fisher and instructed you to disconnect the Marantz. Disconnecting a turned off amp would normally do nothing. In your case, disconnecting the Marantz will cause the Fisher powered drivers to go... quiet. Regards, Jerry
  6. Thornev, for the past 9 years I have been bi-amping my AR-3a's using just the 3 terminals AR provided. Each of my amps has it's own volume control and thus I can vary "voice" by simply varying the power I send to each speaker half. Huge advantage to doing this is to flatten the response curve (see below). This curve was provided by AR with both pots set to max. As you can see AR intended the higher frequencies to "roll off" and this yielded very acceptable results when playing back records produced at that time. I found it way, way too laid back and somewhat "muffled" when playing back CD's and other digital recordings. Notice that with a single amp there is no way to "flatten" this curve unless you modify the xover. With two amps (bi-amp) you can apply more power to the mids and tweeters. Since the tweeters in the AR3a lag the mid driver, you'd cut the mid back (via that mid control) to bring the mids and tweeters into balance. Now this makes a base heavy speaker even more bass heavy and muffled! The key is to advance the mid tweeter amp volume control to bring everything back into balance. Now for the differences between what I do and you do. Both of my amps are of the common ground design. That is, I can connect the commons of the amps together and connect both to terminal 1. YOU SHOULD NOT DO THIS. Your Fisher is not a common ground amp and it is good that you left that "com" lead hanging. With my amps I can power just the woofers or just the mids tweeters. The setup you have the return line for the Fisher is through the shielded cables from the Marantz. To prove this turn just the Fisher on and set the volume low. Then disconnect the audio cables going to the Marantz and you'll find the speakers going quiet. (Quickly plug the Marantz back in because it is usually not good to run tube amps totally unloaded.) If you really want to run the tube amp on the mids and tweeters, the safest way to do this would be to modify the xover and bring out that 4th terminal. By doing this you isolate the power output stages of the amps from each other and can run any type of amp on each speaker half. Hope this helps... Regards, Jerry
  7. Well, Gene, that is exactly the problem and why I choose the SuperZero - in hopes that its natural roll off would NOT overlap the SVS unit in the LOWEST frequencies. I don't know, but my gut feel is a single low frequency driver would yield the clearest, cleanest bass. Regards, Jerry
  8. Gene, is there any reason you did not chose this option? https://www.nhthifi.com/products/16546-c-3-bookshelf-loudspeaker?category_id=1964842-bookshelf-speakers#specs Now, I felt the unit went too low and would overlap too much the SVS sealed 12 inch sub. Regards, Jerry
  9. Adams, you just might be right about that. Another possibility is that board members rather than seeking high performance speaker systems, are spending big $'s on high performance hearing aids. Regards, Jerry '
  10. Gene, your point about AVR LFE output being a summed signal is on the mark. It would be of no value with two subs where we wish to maintain imaging. I did mention in my post above about an external xover, but that would NOT be my goal. I just wish NHT published the frequency response graphs of their units. I suspect that 4.5 inch NHT unit begins to roll off somewhere in the 150Hz to 100Hz range. This natural roll off could be complemented quite well by the sub. As for the low pass defeat, SVS is not the only manufacturer that provides for a complete by-pass. The idea is to let systems like Audseey take complete control of satellites and sub. Regards, Jerry
  11. Adams, it looks like you are correct that the LFE setting is the only way to cross the SVS sealed sub above 160Hz. That is, the actual crossing must be done outside the sub. AVR is one way to do this, but so is an external electronic xover. In both cases, IF YOU CROSS THIS HIGH, you must also make certain that you limit these frequencies from the bookshelf (i.e. the other speaker in the stack). With the NHT unit I choose, I suspect crossing at 100 to 120Hz would be ideal. That is, assuming the NHT bookshelf does a decent job in the 100 to 200Hz range. Now bear in mind, it is "rated" down to 85Hz. Regards, Jerry
  12. Well, Adams, it certainly gets confusing, especially when you bring in AVR units. I don't have a lot of experience with these. I do own a Marantz 5.1 AVR with Koss mains, KLH rears and an AR sub. For movies, it is great! For music... not so hot. I much prefer my AR's powered by a rather standard two channel amp. (Actually my unit has two full range amps in a single box allowing bi-amping with just the three terminals AR provided.) Anyhow, when my AR's finally succumb, I know I would never be happy with a single sub for music. I simply must have a sub for each channel. Further, I want sealed units, because I enjoy the bass delivered by the AS system. I can hear the difference over ported systems and I simply prefer the AS sound. So with the "heavy lifting" being done by the subs, and having found in SVS sealed units capable of being driven by speaker level inputs, my next problem is to find AS units to handle the mids and highs. (I believe Rel is correct that integrating subs into music systems works better when the subs "see" exactly the same signal as the mains with any and all phase shifts introduced in the power amps. Next the SVS unit can easily go to 200Hz, which is another plus.) So to reiterate, the remaining problem would be to achieve the dispersion of the domed mid and that is NOT easy. My "gut feel" is that the NHT unit with the 4 inch "mid/woofer" would do this better than units with larger drivers. My fear is that larger drivers would just become far too directional at and near the xover with the tweeters. Thus giving up dispersion to gain... what? So I am back to where I started. Clearly, the SVS/NHT stack is not perfect, but it still might be the closet you can get with modern components. My only real fear is with the NHT SuperZero and will it really get down to the range of 200 to 150Hz smoothly. Possibly members who have them can comment. Regards, Jerry
  13. Supposing you really enjoy that acoustic suspension sound "invented" by AR and supposing you no longer wished to "struggle" keeping those 40 to 50 year old speakers running and properly tuned. How would you achieve that "AR sound" with devices in today's audio market? There is a current thread about the resurgence of KLH started by Frank, but I did not see any AS offerings in that new line. (It's possible that AS speakers will be included, but as I said, I did NOT see any.) Thanks, Frank, for that thread as it is interesting to see an American company ... trying! Anyhow, I have been giving this subject some thought and given that I would be willing to spend some $'s, but NOT mortgage my house, I think stacking something like these: https://www.nhthifi.com/products/10654-superzero-2-1-our-amazing-mini-monitor?category_id=1964842-bookshelf-speakers#specs On a pair of these: https://www.svsound.com/collections/1000-series/products/sb-1000 Just might yield acceptable results. The SVS 12 inch, front firing sub is a sealed box and the NHT unit is also sealed. The specs on the NHT rate it down to 85Hz, but my suspicion is that around 120 is more realistic. At the same time the SVS is rated up to 260Hz, but again looking at the actual graph, 200 is more realistic. My point is there should be adequate "room" to merge these units using the variable xover on the sub. Two questions: 1. What do you think of this stack? 2. How would you achieve that AR sound with modern components? Regards, Jerry PS: Just happened to think that for Frank and his LST's, you could get 4 of the NHT units and wire them two units for each channel in parallel.
  14. Well, I agree with you, GD. In small to mid-sized rooms, you'll get some 'room gain' that coupled with the shallower roll-off slope, will get you a low frequency bass extension. When you elevate, you give away that room gain and will never hear those lowest notes due to the roll-off in frequency response. In short, elevation results in a low end response almost identical to the speaker's quasi-anechoic frequency response. Regards, Jerry
  15. RAY, not vintage, but the Sherwood RX-5502 (see datasheet attached) would handle 4 AR-3a's. Reason for this is this unit has 4 full range amps (i.e. 2 stereo amps) in a single box. Each amp is rated 100 wpc at 4 ohms. Beauty of this scheme is you get two independent volume controls so you can balance the two set of speakers to get similar volume in spite of room placement. With a single amp, one speaker set with dominant the other just due to its position in your room. Regards, Jerry Sherwood-RX-5502-datasheet.pdf
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