QLS 1 Amp Discussion

Discussion in 'Infinity Loudspeakers' started by tlcasper, Feb 13, 2017.

  1. tlcasper

    tlcasper AK Subscriber Subscriber

    Messages:
    177
    Location:
    Ontario, Canada
    Hello all, I'm one of a number of QLS 1 speaker owners here, and a very happy one.
    I picked mine up last summer, they needed very little work and have easily become my favourite speaker.
    I have been powering them with a single, restored, McIntosh 2205. The amp handles the speakers fine, and never gets warm, even with extended sessions of pushing it. Man can these big speakers really fill a big house when pushed, the music is everywhere.

    My original thoughts where that I would get a second 2205 at some point and try bi-amping them or use the amps as two 400 watt mono blocks, depending on which I liked better. But prices, and lack of a decent 2205 in my area are making consider other options. My 2205 is very sellable, restored, excellent condition, with the slant leg cabinet.

    I'm looking at a single McIntosh 2300, or a 2500. Though the 2500 would stretch the budget.
    A Mark Levinson No. 23
    And wondering how a 70 WPC Conrad Johnson 11A tube amp would work with the QLS's

    Any thoughts or experiences with these speakers, or other amp suggestions that have surprised would be appreciated.

    Also, I'm in Canada, and have yet to find another Canadian with QLS 1's. I wonder how many pairs made it North?
     
  2. chef free

    chef free AK Subscriber Subscriber

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    1,781
    Location:
    Oakland! What?!
    When they are set up right, with everything restored and working, in the right room, and with proper amplification, they are stunning speakers, for sure! Which version do you have, the painted baffle or the veneer baffle?

    I started just like you, using an MC2200 (your 2205 without big blue meters), then I got a good deal on a second, rust-free, local 2200. The difference in woofer performance was not subtle. These speakers were measured, in a magazine review, at 82.5 dB, so they NEED a lot of power to be played as loud as I like my music.

    I'd love to get a 2300, 2500, or 2600, (or two!) and bi amp them. I'd like to try a Bryston 10b crossover to maybe squeeze a little more power out of those amps too. Infinity recommended against an active crossover, stating concerns about phase problems being introduced but they did suggest vertical bi-amping.

    Arnie Nudell insisted on demonstrating them with tube power, so how about a pair of 3500's on the top? Now that would way out of most folks budgets but I bet it would sound great! You could try that 11A on the highs and the 2205 on the lows, you might get a better sound.

    You might be able to sell that nice 2205 and make almost enough to afford a pair of 2200's but these amps are all getting old and need to have the electrolytic caps replaced. (That's not an opinion, it's a matter of physics.)
     
  3. whoaru99

    whoaru99 Epic Member

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    36,800
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    LoTL
    Amongst all you listed I have a Levinson No. 23. It's a very nice amp. I use mine (mainly) with a pair of Thiel CS3.6, that run about 2.7 ohms across the majority of the audio spectrum.

    If the QLS has a nasty impedance curve or severe phase angle thing going on then an amp such as the Levinson can be beneficial. However, if they're a relatively benign load then, IMO, an amp such as the Levinson isn't really necessary.
     
  4. totem

    totem AK Subscriber Subscriber

    Messages:
    4,576
    Location:
    Vancouver B.C.
    1 in BT as we speak.
     
  5. 7.62

    7.62 Gearhead Subscriber

    Messages:
    511
    Location:
    Las Vegas
    I was at our vintage shop just the other day, he has a 2255 and a 2105, for a brief moment I thought about purchasing both. 2255 for Woofer duty and the 2105 up top handling the rest. We discussed the option but we both agreed the 2255 might be a stretch on the bottom. For the price of both I'm pretty sure I can find a used 352 or 401 and just be done with it.

    Right now I'm doing an Emotiva but being very cautious with the volume knob.

    They sound insanely good. I can't image how good they can be with the proper amp driving them.
     
  6. slimpikkins

    slimpikkins Super Member

    Messages:
    1,382
    Location:
    South East PA
    Running a MC7200 on my QLS. Only speakers I owned that ever lit the power guard lamps. It is in good condition and is over 300wpc at 4ohm. Would love a second one someday or an MC2500. The QLS blew the right channel in my Philips 578. I cannot fix it and it's now a 70lb paper weight. Hard speaker to drive to realistic levels...
    Jim
     
  7. tubed

    tubed Lunatic Member

    Messages:
    11,651
    Location:
    Aztlan
    While quite inefficient, I think the QLS-1 was designed as a relatively benign load.
    From my point of view, room size and sound pressure determines how loud you can go, realistic or beyond real life listening levels.
    The size of my 14' X 17' room and 250 watts per channel is more than enough power.
    The amplifier never breaks a sweat, although I do enjoy more realistic(or less) type of listening levels.

    To get a +3db increase, double the watts per channel to 500 per, probably not necessary unless in a really large room, imo.
     
  8. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,781
    Location:
    Oakland! What?!
    The Watkins woofer was designed to make the impedance curve controllable across all the frequencies that it reproduces. Arnie Nudell wanted impressive specs (18 Hz), so he didn't use the circuit recommended by Bill Watkins. And he added 35 grams of mass under the vc dust cover. This drives the load down to 1 3/4 ohms at certain frequencies, hence their reputation as "amp killers".

    Edited to add: "That's what the Watkins' told me."
     
    Last edited: Feb 13, 2017
  9. tubed

    tubed Lunatic Member

    Messages:
    11,651
    Location:
    Aztlan
    Inefficient but not amp killers, as far as my experience goes

    Stereo Magazine 1977 measurements showed some wild swings of the inefficient QLS-1s.

    " Our impedance measurements verified Infinity's claim.......
    From 6 ohms @ 20khz, it dropped to 4 1/2 ohms @ 50hz before rising 11 ohms @ 900hz,to 7 3/4 ohms @ 2khz then rose to 18 ohms, falling to 9 12 ohms @ 10khz, 4 1/2 ohms @ 20khz, falling to 3 ohms @ 60HZ before rising again."
    Emphasis on power consumption.

    Infinity's brochure basically claims the Watkins bass circuit stays around 5 ohms, if I read the graph correctly.

    I know Watkins was miffed at Nudel but perhaps Arnie gave in?
    Anecdotally, I've had the dust cover off more than a few Watkins woofer and never came across any mass loading stuff.
    Never killed an amp withe QLS-I, perhaps I've never overdriven it.
     
  10. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,781
    Location:
    Oakland! What?!
    That's just what I was told by Bill and Bill Jr. They were not happy that people were blaming their woofers for killing amps. Those measurement seem very safe for most capable amps, nothing like Infinity's bona fied amp killer, the original Kappa 9. Maybe people with under powered amps just burned them up trying to get volume out of these things...
     
  11. tubed

    tubed Lunatic Member

    Messages:
    11,651
    Location:
    Aztlan
    There's an interesting communique in which Bill Watkins states he had never met Arnie Nudel, never been to the Infinity factory and was only responsible for sending Infinity prototypes of the Watkins woofer.

    Also of note it seems as though the mass loading/misalignment was limited to the original QLS-1 and "a few later ones" that sounded "bad", according to Watkins statement.
    So it seems likely a limited number of problematic QLS's ever existed, perhaps hopefully, a very few?

    All the Watkins/Infinitys I've had, had very good bass response, never caused amplifier trauma, were not mass loaded and I don't believe came close to producing 18Hz lows.

    http://iccbrabant.tripod.com/icc/id1.html
     
  12. slimpikkins

    slimpikkins Super Member

    Messages:
    1,382
    Location:
    South East PA
    The song which I noticed my power guard lamps flash was "Into the fire" by Sarah McLaughlin. Heavy extended bass. I think the cd that killed my 578 was Bill Cobham "warning" any thing of his must be played loud, my favorite drummer. The open track on his spectrum album is incredible on the QLS too. May not be considered a killer but the QLS killed my 578 and does the very hard task of sucking everything out of my mc7200 on some songs. That amp is stable to 1 ohm btw...

    Thanks for that letter Tubed. I think I saw that here before but was nice to read it again. I thought he also said that he felt the cabinet was too big for that woofer as well...
     
    Last edited: Feb 14, 2017
  13. tlcasper

    tlcasper AK Subscriber Subscriber

    Messages:
    177
    Location:
    Ontario, Canada
    Hey chef free, do you use your 2200's bi-amped, or in mono, one per speaker?

    I was looking at the 2500 in BT, but shipping to Canada is a killer.

    Good info here.
     
  14. tomlinmgt

    tomlinmgt AK Subscriber Subscriber

    Messages:
    10,219
    Location:
    Arlington, TX
    I started out with a Soundcraftsmen MA5002 pushing my wood faced Q1's and only saw it approach clipping a few times when I was really pushing it. It was a great sounding amp, but not the best I tried. A Hafler 500 was ok but not as nice as the Soundcraftsmen. An Emotiva XPA was a sonic disappointment, but an Aragon 8008 was a winner and illuminated what I felt was the best route to take with the Q's...a high current and super stable neo-vintage (80's/90's) design The best I tried and what I ultimately settled on was a Threshold s/300. It did everything better than all that preceded it. I was so impressed I picked up a second so I could biamp, but honestly couldn't tell a huge difference between single or multi-amp configuration (a testament to how extraordinary Pass' STASIS design worked with a design like the QLS-1's, I suspect). Never tried a Krell...was completely smitten with the Threshold and tweaked with preamps and DACs rather than power amps after I savored in its greatness night after night. It was also about that time I started messing with distributed bass...which was a huge game changer (even with the QLS-1's).
     
  15. chef free

    chef free AK Subscriber Subscriber

    Messages:
    1,781
    Location:
    Oakland! What?!
    I have the 2200's strapped in mono for 400 watts per. I'm assuming that strapping cuts the damping factor in half. I have tried them both vertically and horizontally bi-amped but never with an active crossover. More power made the woofers sound best but it was nice to have separate volume controls for high and low frequencies.

    I'd love to get that amp, and it is a good price, I've seen them go for between $2500 - $4500, but I have determined to buy more music and less equipment this year.
     
  16. tlcasper

    tlcasper AK Subscriber Subscriber

    Messages:
    177
    Location:
    Ontario, Canada
    There is one Threshold 400a near me. And for some really big power, a pair of Bryston 7B ST mono blocks.

    My QLS 1's are the painted baffle, quite early 751 and 752. With the itchy pink stuff inside.
     
  17. Ds2000

    Ds2000 All About every cool stereo component. Subscriber

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    Location:
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    What isn't able to be fixed on the 578?
     
  18. slimpikkins

    slimpikkins Super Member

    Messages:
    1,382
    Location:
    South East PA
    Something is frying resistors on the driver board. I've exhausted my abilities and research on the internet. It's one of those documented problems that many have written about on this site and others but never have completely fixed or the threads just petter out.

    To me it is not worth the money to get it fixed. By the time I pay someone for their time it will not be cost effective. Also the units cheap chassis of the amp would never make it through shipping. It is too heavy and even well supported and double boxed it would get bent up for sure.

    I still have the preamp as well. When they are in working order both are real gems.
    Jim
     
  19. rdka

    rdka AK Subscriber Subscriber

    Messages:
    264
    Location:
    Myrtle Beach
    My son uses a bi-amped Audio Research setup. He is not a member here & I bought the stuff for him. D76 tube on top/D120 for bass/heavily modded LS 1 tube pre-amp.
     
  20. 7.62

    7.62 Gearhead Subscriber

    Messages:
    511
    Location:
    Las Vegas
    We had some fun lastnight, used just the Emo Gen-2 but I put a small household fan above the front of the amp so that it would blow cool air thru the chassis. I also replaced those ugly green midbass with some tang band neodymium mids I had laying around. Fan on, music on, the Emotiva handled everything with ease.....to our ears everything sounded really good, of course bad recording sounded really bad. I really pushed it hard. Going to keep an eye out for a clip on type fan that will attach to my rack.
     

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