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ReliaBill Engineer

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  1. ReliaBill Engineer
    I’ll be rebuilding these early AR/3a dome midranges. Open circuits, per the seller. Once complete, I’ll use them to compare sound to the 2” hard dome midranges above.
  2. ReliaBill Engineer
    Great news!! I have a pair of AR-3a dome midranges coming my way. They need repair work done. I’ll document the repair. Then I’ll compare to my dome midrange “mod” for the 2ax. This will be my 3rd pair of 1965-1969 3a dome mid repairs. The other 2 pair got sent back to their owners locally (in state). This pair is mine.
  3. ReliaBill Engineer
    The light beige looks just like my original cloth grill on my 2ax. Very difficult to see any difference.
  4. ReliaBill Engineer
    Sound deadening. Acoustic damping inside the speaker cabinets. I’m working on an interesting project at work that pertains to this. Artemis IV has a “hollow” tubular section 33 feet in diameter, 40 feet high, 34,194 cubic feet volume, where computer modeling shows it to have destructive levels of acoustic resonance. In essence a huge bell, or a volume that will build up acoustic vibrations from air passing over the outside of the volume at very high velocity. Modeling shows the acoustic vibrations to build to a level shown to be a structural hazard both to the section as well as to the avionics and structures within the volume. The solution has to be low mass, low volume, and fire proof. Frequencies 10 Hz to 10 kHz. 30 dB of damping.
  5. ReliaBill Engineer
    Original tweeter, woofer, crossover capacitor values. These have the sound I was looking for. Airy, clear. Not “laid back”, but very musical over long listening sessions. Perfect for my tastes.
  6. ReliaBill Engineer
    I’ve been/am very happy with these ‘65 AR-2ax speakers. They are musical, and just great to listen to. These are now in my workshop in the garage, getting some needed cosmetic attention. Listening to some Bonnie Raitt: Finished my listening sessions. Now to fully incorporate the much better midrange drivers, while keeping the AR motif. Auditioning a new cartridge and stylus:
  7. ReliaBill Engineer
    I’ve been/am very happy with these ‘65 AR-2ax speakers. They are musical, and just great to listen to. These are now in my workshop in the garage, getting some needed cosmetic attention. Listening to some Bonnie Raitt: (Wife not happy in the kitchen. James Bond on TV….)
  8. ReliaBill Engineer
    The original foam is soft polyurethane foam. Medium density open cell. Finding it in black is the problem. But, probably available on eBay.
  9. ReliaBill Engineer
    Comparison. Original paper cone mid and the dome. Original: Dome midrange:
  10. ReliaBill Engineer
    I have a bearing press. I already have the forms made. Using a propane burner to anneal the titanium. This alloy can be softened; otherwise it would crack badly when put through the expanding dies.
  11. ReliaBill Engineer
    The expanded titanium arrived today. Very comparable to the original aluminum.
  12. ReliaBill Engineer
    I’m very happy with the sound of these at present, using the original woofer and (super)tweeter, and 4/6 uF capacitors. With the 2” dome mid, it has everything I want. Surprisingly, I’m having a really tough time sourcing the expanded aluminum guards for the mid. 1/2” x 1/8” diamond opening, 18-20 gauge thickness. I plan to replace the perforated steel guard currently on these domes. Just to keep the AR appearance. I’ve ordered expanded titanium from China. Closest I could find. Using this dome midrange/tweeter, I found that it, too, needs to be wired just as AR did, out of phase polarity-wise, to get a smooth transition. The tweeter domes don’t go way out to 20 kHz. But the end result is a hugely pleasing easy, comfortable, effortless sound that I can listen to all day with no regrets. In my opinion, I’ve done the least amount of molestation to these old girls, while improving the sound, yet keeping the old character. The 16 ohm pots, 6 uF caps, with the new domes and small 0.1 mH smoothing inductor at the dome terminal, helps to control the dome nicely. Whether at very low listening level, or much higher volume, the speakers just sound GOOD to me. No matter the age of recording, nor genre, they are a relaxing, good listen! My wife prefers listening to her CD collection vs my vinyl collection. Yesterday was her day. Trisha Yearwood, Bonnie Raitt, The Supremes, The Drifters, Patty Loveless, Oak Ridge Boys, etc. She had a good time!
  13. ReliaBill Engineer
    And performance? Sound, characteristics, plots, tests?
  14. ReliaBill Engineer
    So we’re back in the Mids and Tweaks back alley. Someone please describe the difference in performance between the paper cone midrange used in the early 2ax, and the dome midrange used in the early 3a….. Descriptions and/or plots and measurements are all fine for answering.
  15. ReliaBill Engineer
    The titles of the clips are dead give aways:
  16. ReliaBill Engineer
    Nearfield recording vs further back in the room also makes a difference. It’s a lot like most people preferring the louder of 2 playbacks. As for the Hello Dolly recording, I don’t know which recording you’re listening to. Digital or analog. You didn’t hear it with whatever you’re listening through and from. From the album, it’s actually at 1:14-1:16 primarily in the left channel. I figured you’d hear it on your way into the 1:30 mark. My mother was a perfectionist. It bothered her. I hear it from the dome mids in my room, and over my headphones, and first heard it from my Polks several years ago. In ‘65-‘66 my dad had the AR-2ax’s and couldn’t hear it. But, he was using a Shure M44C cartridge also. I couldn’t hear it over these stock AR-2ax’s. My dad reminded me of the history associated with that album, at least in our household.
  17. ReliaBill Engineer
    Not a tweak or mod. Just an attempt at comparison. There is a story behind that Glenn Miller album. I can remember my parents having a heated discussion about it. My mother worked for Columbia Records when that album was recorded/mastered/pressed. As the QC Supervisor of the California pressing plant, she raised the issue of a mistake made during recording of “Hello Dolly” with Columbia Executives. The decision was made not to re-record it. Prevailing opinion at that time was that home listeners won’t be able to hear the mistake. In ‘66 my dad’s system wouldn’t reveal it. Stock, these 2ax won’t either. But if you pull up the original soundtrack, at 1:30 into it, you’ll hear one of the trombone players hit the music stand in front of him! That’s why my mom brought that recording home, and my dad was adamant that my mom was making a big deal, risking her job. She didn’t lose her job. She was promoted, and trained the new hires for the new Santa Maria CA pressing plant.
  18. ReliaBill Engineer
    This isn’t about room placement nor equipment. It’s not a show of someone’s “system.” It’s not about someone’s choice of music media. Suffice it to say, identical equipment was used for both, except for the midrange driver. It's just a comparison of midrange drivers. It’s my attempt to keep the AR sound character, yet use a mid driver that has better dispersion, a less strained sound, and render more detail from the recording. I listen to 95% vinyl sources, so that is what I used for comparison. In my experience, it is entirely possible to keep the AR sound, but also add more fidelity, and remove some listener fatigue. Those paper cones wear on me after a while. I’m convinced that’s the reason AR added the fiberglass padding.
  19. ReliaBill Engineer
    Both are from the same track on this original 1965 Epic vinyl record. Passed down to me from my parents. No electric bass. Played using the Shure V15V-MR cartridge.
  20. ReliaBill Engineer
    If you *looked* at the videos, you’d see the stock midranges on one video vs the domes on top of the cabinets in the 2nd video.. And “Thank you!!” The fact that the 2 videos sound so much alike is a complete validation of my efforts! Very difficult to capture the entire differences using a cell phone. And yes, I know that there will be differences from speaker placement, together on the floor vs on 20” stands 8’ apart. But my point is that the domes blend so well with the AR tweeter and woofer, and achieve/keep the original sound character! Yet….In the actual room one can hear so much more detail from the recording and so much more “air” to the sound using the domes, vs the colored and directional sound from the paper cones. To capture a better sample from my cell phone, with less room interaction, I toed the speakers in to my standing position between them. Normally I listen with the speakers facing directly forward. There are no “crossover mods.” Same 6 uF caps and same 16 ohm pots as used with the original AR paper cone mids. Fact is, all I did was clip the green and yellow wires from the paper cone mid and attach them to my dome leads. The paper cone mids are out of the circuit entirely. I used weatherstripping foam gasket that allowed me to pass the wires behind the paper cone mids, yet keep the airtight seal.
  21. ReliaBill Engineer
    For comparison. How can anyone make a comparison of changes made, using 2 entirely different tracks?
  22. ReliaBill Engineer
    Well, I went back and moved my original AR pots to their original positions. On my first speaker recap of the 2ax pair, after cleaning the pots, I moved them so the “dot” was exactly midway in the total rotation of the pot knob. As RoyC later advised, it wasn’t a good move. Agreed! So now both speakers have both pots in their original positions. And now I run both speakers with mid and tweeter pots in their “home” dot positions. I documented my midrange mod in the “Tweaks and Mods” section of the forum. Goal was to have the same sound as the original 2ax drivers, just cleaner, with more detail. That goal has been totally realized. But I did run into the same sort of issue that AR did with its paper cone midrange, namely that the top registers of sound were peaky and ragged. Same issue with the dome mid I selected. I chose an inductor to roll off that raggedness of the 2” dome. But regardless, I ran into the same issue that AR engineers did 58 years ago. So, full circle, I ran into the same issues that AR did, and answered my original question of “why the FG pad over the midrange driver?” Just a comparison. I chose a 1965 record of The Glenn Miller Orchestra on Columbia’s Epic label for jazz. My experience is that these records are recorded “hot.” They can be fatiguing over long listening sessions. But here, the pots are at their “dot positions” for mid and tweeter. Original crossover values, original pots, original internal rock wool damping. Not much difference in sound character between mids (domes vs paper cones) other than smoothness, dispersio, and level of detail. (Domes are wired to the internal wires for the original mids, the yellow and green wires. Polarity of dome reversed the same as original mid and tweet. Using internal crossover and pot.)
  23. ReliaBill Engineer
    Just some sound samples. Such a big, effortless sound! Longer track. Linda Ronstadt: Shorter track, also Linda Ronstadt: And, for contrast, the squawky AR paper cone midrange: Same track as above, 1965 Glenn Miller Chattanooga Choo Choo:
  24. ReliaBill Engineer
    Next, these will get the expanded aluminum grills, to keep with the AR midrange driver “motif.” And BTW, yes. I did remember to reverse the polarity of the midrange dome driver. I love the effortless, airy sound! I can listen for hours on end, with no irritation or fatigue. When complete, this will look the part of an AR driver, look right at home! But belie the squawky, numb sound these had. All my goals will have been met.
  25. ReliaBill Engineer
    So the next step…. I tied in to the original AR crossover network. Using the internal 6 uF capacitor and 16 ohm pot (rheostat). Plus my shaping network at the midrange dome. Added a foam ramp in front of the dome to deaden diffraction from the front edge of the cabinet top. But in alignment with the VC of the original midrange. Used foam weatherstrip to reseal the original mids and allow passing wires from behind the mids. Seal was good by using the “pressing the woofer cone” technique. I played some Epic label Bobby Hackett trumpet music (playing Bert Kaempfert’s hits). These can sound hot or squawky on different speakers, especially so using the Shure V15V-MR cartridge. I think it sounds great! My wife actually noticed the difference, and began dancing in the living room! These sound very smooth, neutral, detailed, and very airy, with a huge spacious sound. Imaging is tremendously wide and deep, not 1-dimensional. I’ve found that these mid domes sound best at a 65% setting on the pots. Tweeter at 85%. And yet, still very much the AR sound. Just a whole lot less colored and squawky. And, now I can lose the toe-in position of the speakers. Just point them straight out.
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