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QLS dimensions

Discussion in 'Infinity Loudspeakers' started by AirCombatGuy, Mar 15, 2017.

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  1. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    I've owned a pair of Q2's since they first came out, love them a lot, but regret that I didn't pop for the QLS. The attached file contains a CAD drawing of a QLS derived from the photo in the Infinity brochure. I would very much appreciate someone who owns a QLS verifying the various dimensions. I have been bitten with the speaker building bug and am contemplating creating a QLS look-alike (Watkins woofers, but everything else new). I've seen the QLS and Q2 hybrids folks have created, so they give me some confidence that this is do-able.

    Saw the amp thread, and for the record I push my Q2's with an Adcom 5802. Previously used a Bryston 4B and before that a Dynaco 400 (which surely dates me!). None of them have had any issues with the Watkins.

    In the drawing, the woofer, mid-bass coupler, dome mid-range and tweeter diagrams were all derived from direct measurements on my Q2's (and I have CAD drawings of them as well).
     

    Attached Files:

  2. 7.62

    7.62 Gearhead Subscriber

    Messages:
    640
    Location:
    Las Vegas
    I'm not sure if they're the same but I have a pair of quantum 5's in my office, Watkins 12 inch Woofer, with the dome midrange and emit Tweeters. If you would like actual dimensions from these no problem.
     
  3. SicMan

    SicMan Fire up those speakers

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    2,953
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    Wolcott - CT. USA
  4. slimpikkins

    slimpikkins Super Member

    Messages:
    1,419
    Location:
    South East PA
    Sounds like a fun project. I have the original QLS1 with the black front. My mid bass coupler is a little lower than what you have. From floor to center it is around 25 1/4". The bottom edge of the first mid dome is in line with the mid bass couplers center. Center line between the mids is 6". Bottom of the bottom tweeter is 21 3/4 from the floor. Edge of the cabinet to center of the tweeters is 3 1/2. Center of mids is 7 1/4. My base is around 7" high with 3/4" space before the main box and base.
    Hope this helps.
    Jim
     
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  5. chef free

    chef free AK Subscriber Subscriber

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    1,855
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    Oakland! What?!
    This is a very interesting idea! I'd like to know more about the drivers you plan to use, what will you use for the mid domes? The rest of them are pretty available.

    I think the weakness of the QLS-1 is the fact that they sound so different when I stand up or sit down. The problem is the mid bass coupler being so low in the cabinet. I've had the fantasy of putting a second mid bass coupler near the top of the baffle. Since Braun made a 4 ohm version, it would be pretty easy to wire them without changing the crossovers.

    It's worth noting that Bill Watkins considered the cabinet of the QLS-1 to be too large to get the best out of his woofers. He preferred the Q-3 cabinet size. Bill Jr. once told me that his father had suggested to Arnie Nudell that the QLS-1 cabinet should have a baffle inside it to make the box smaller. We know that Arnie used smaller woofer enclosures with tall baffles for the mids and tweeters on his RS series.
     
  6. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    Jim, those are just the dimensions I needed, thanks, I'll update the CAD drawing.
     
  7. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    I'm still evaluating drivers, other than the Watkins, which are a given. Selecting a mid-bass coupler is tough given how critical that frequency range is. At the moment, I'm leaning toward the Madisound Scanspeak Illuminator 12MU/4731T-00 4.5” 4 ohm driver. I understand that the original QLS-1 Philips driver was 8 ohms, and if needed the Illuminator comes in an 8 ohm variety too. Very flat, but unfortunately also pretty pricey. I've thought about having two per cabinet, but that makes the price even worse. A cheaper, but probably not as good an alternate is the PE Tang Band W4-1720 which is a 4 ohm part. As far as the dome mid-ranges, I've seen that at least one Infinity Q-3 owner has successfully used a PE Dayton Audio DC50FA-8 2" dome. I've also been looking at the PE Morel MDM-55 (and CAM-558 round version) and the EM-1308. Both appear to be a lot flatter than the Dayton Audio DC50FA-8 but again more expensive, especially when used in large quantities! I've thought about going to planar mid-ranges but was disappointed in the Bohlender-Graebener offerings -- not very flat (at least not without some work) and pricey. No QLS look-alike would be complete without ribbon tweeters. Again, I've been pretty disappointed with what I've seen so far. Most of what I've seen at PE and Madisound are not very flat (without work) and some of them (the RAAL tweeters!) are really expensive (I can't imagine doing a line array of RAAL tweeters -- more money than I've got!). For the moment, I may settle on the PE Dayton Audio PT2C-8 planar tweeter which isn't terribly expensive in quantity, and is reasonably linear. It falls off fairly gracefully and won't sound too hot.

    Although I intend the exterior dimensions of my cabinets to mimic the QLS-1, I plan to sub-divide the cabinet internally so that the woofer only "sees" a volume equivalent to a Q-2 and I'll use the Q-2 crossover values for the Watkins tuned-circuit. I've never had a problem with my Q-2 woofers bottoming-out and in a brief e-mail exchange I had with Bill Watkins he felt this would be a good place to start.

    There are still lots of things to consider, not the least of which is figuring out the crossovers. The E-array project on the PE project website by R Carpenter should help me a lot. I'm also doing a lot of thinking and web surfing about the cabinet construction. The QLS-1 cabinet seems to be pretty simple, but I think cabinet construction has evolved quite a bit since then and I may want to use some newer techniques. This is going to be a very time-consuming (and expensive!) project, so I want to get things as "right" as I can before I start committing real dollars and time. So by all means, feel free to make suggestions!
     
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  8. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    Jim, just tried to update the QLS CAD drawing based on your measurements but had a problem with your measured tweeter and mid-range (vertical) center lines. You said "Edge of the cabinet to center of the tweeters is 3 1/2. Center of mids is 7 1/4" -- the 3 1/2" to the center line of the tweeters seems accurate since I had 3 1/4" based on the photograph; but the 7 1/4" to the mid-range center line seems too little given the width of the tweeter and mid-range units. Your measurements suggest that it is just 3 3/4" from the tweeter center line to the mid-range center line but the tweeters are 2 3/4" across (so 1 3/8" from edge to center line) and the mid-range is 5 1/8" across (so 2 9/16" from the edge to the center line). But given the size of the units the center lines have to be at least 3 15/16" apart even if the tweeter is butted up against the mid-range (and at least in the photo, they are not). Something doesn't computer... I'm pursuing this measurement exercise mostly as a learning experience, not because I'm intending to mimic them that closely.
     
  9. slimpikkins

    slimpikkins Super Member

    Messages:
    1,419
    Location:
    South East PA
    Hope this helps. Top photo scale is at the edge of the cabinet. Bottom it is at the centerline of the mid. Mid and tweeters are touching.
    IMG_0408.JPG IMG_0410.JPG
     
  10. tubed

    tubed Lunatic Member

    Messages:
    12,026
    Location:
    Aztlan
    I don't experience any difference in sound presentation from my QLS-1's, whether I'm sitting standing or rising up out my chair or back down again.
    I have to be less than a foot away from the speakers while raising or lowering my ears to hear any changes between drivers.
    Moving more than a foot away, and further, cancels out any of that kind of effect(comb filtering?).
    I think the design with it's higher frequency drivers so close together allows for an unchanging sound effect whether standing sitting or moving around the room.
     
  11. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,855
    Location:
    Oakland! What?!
    Wow! Really? That's my major complaint about these, otherwise outstanding, speakers. My wife hears it too. I wonder if it's the room...

    I've tried turning the "mid-bass coupler" up and down but I can't make it right. How do you have your crossovers adjusted? I've got the EMITs at 3 o'clock (old age hearing), the domes at 12 and the mid-bass at 9, with the crossovers on "HIGH" and the rear EMITs off.
     
  12. tubed

    tubed Lunatic Member

    Messages:
    12,026
    Location:
    Aztlan
    I wouldn't mess with ya , Chef.
    Actually I don't remember ever noticing that on any speaker system, only losing the imaging on some Maggies by tilting my head to the left or right a couple of inches,ie.
    I pretty much run all the pots wide open, the tweeters even have a slightly larger capacitor to boot.
     
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  13. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    Fascinating! The Infinity Quantum Line Source brochure copyright 1977 which shows a black front QLS-1 shows a sizeable gap between the tweeters and mid-ranges. I wonder which implementation came first -- the one in the brochure or what you've got? Tried to upload the brochure photo but they claim its too large... I guess Infinity kept experimenting with driver placement. My initial CAD drawing was derived from the photo in the brochure. On the other hand, my Q-2's have the mid-range and tweeters butted up against each other and the center line distances are only very slightly different from what you reported for your QLS-1 so maybe the brochure photo was a prototype and what you have is what they delivered.
     
  14. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,855
    Location:
    Oakland! What?!
    I'm guessing that the picture in the brochure was a mock up because I have never seen any other pictures or actual speakers with that set up. The square off set ring around the woofer is the give away. Here's that picture: http://bobbyshred.baberuthband.co.uk/infinity/qls.html Look at ANY other picture of the QLS-1 and you will never see a square off set ring or this arrangement of drivers.
     
  15. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    Guess I've been oblivious of the woofer mounting... so it's a ring and not square? My understanding is that it protrudes about 1 1/4" although that distance changed over the production run.
     
  16. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,855
    Location:
    Oakland! What?!
    The "early" QLS-1 has the black painted baffle, it's the one with the "time alignment" ring, (and wire frame grills, itchy pink fiberglass stuffing and the first crossover with 1600uF caps on the 2 ohm side of the Watkins) they have serial numbers below 1007000.

    The second version has a wood veneer baffle, but only a plastic trim ring around the Watkins, (and the "stand off" grills, white polyfill stuffing, and the later crossover, dated Feb. 2 1978, with 1400 uF in place of the 1600uF caps.)

    Are you planning on using the second crossover? (shown here>) [​IMG]
     
  17. slimpikkins

    slimpikkins Super Member

    Messages:
    1,419
    Location:
    South East PA
    Hey Chef free wasn't it the 1600uf caps and 4.5 coil changed to 1100uf and 6.5 coil on the 4 ohm side and the 1400uf and 20ah coil on the 2 ohm side the same on both?
     
  18. AirCombatGuy

    AirCombatGuy New Member

    Messages:
    9
    Location:
    Hudson Valley NY
    I am currently planning to use the Q-2 values (and internal cabinet volume) for the Watkins woofer; I don't need it to go down to 18Hz (and risk bottoming out) - 24Hz is good enough! I would like to keep the same crossover frequencies, if possible, but the drivers I select will probably have some influence on that and consequently the crossover componentry. I'd like to keep the whole thing phase coherent, like the QLS. The simpler the crossover the better.
     
  19. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,855
    Location:
    Oakland! What?!
    I wish I knew for sure but that's how I remember it. Maybe others with the original painted baffle could check...
     
  20. tubed

    tubed Lunatic Member

    Messages:
    12,026
    Location:
    Aztlan
    1400uf/20mh/2ohm on my veneerd fronts
     

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