Infinity Qa Vs. Qb

Discussion in 'Infinity Loudspeakers' started by Pyrrho, Jan 22, 2019.

  1. Pyrrho

    Pyrrho Well-Known Member

    I recently acquired a pair of Infinity Qa speakers, and used the information in this thread to help me repair the one tweeter that was not working:

    (Reading a later post about the magnets was really useful. Thanks to all who added useful information in that thread.)

    Anyway, they sound really great for old speakers that were "bottom of the line" when they came out (though almost $300 for a pair back then was plenty of money, too much for me at the time). And the woofers seem to integrate well with the tweeters. I am not the only one to think so; you can read a Stereo Review article about them at:

    in which they say, among other nice things:

    The high-end response, in particular, was at least the equal of anything else we have heard in regard to smoothness and dispersion. Furthermore, it was so well blended with the woofer output that we felt a sense of listening to a single unified sound source.
    Now, since the Infinity Qb uses the same woofer and tweeter, and simply adds a midrange unit (which I would normally expect to be a good thing with a 10" woofer), how much better can it be, if at all, given how well the woofer already integrates with the tweeter in the Qa?

    This is a purely academic question for me, since I am not planning on buying the Qb (but who knows? I was not planning on buying the Qa). Do any of you have both models of speakers presently, and, if so, what are your impressions of the differences between these speakers? What good is a midrange driver added to a system in which the woofer and tweeter already integrate so well?

    Or, if not having them presently, do any of you remember listening to both models in the past, and, if so, what were your impressions of the differences?

    I know, this is a subjective sort of question, and I welcome all perspectives on it.


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  2. swechsler

    swechsler Frog Whisperer

    7th row center
    I no longer have my Qa's (gave them away a few years ago), I do remember being very impressed by them. My one complaint, however, was the subdued midrange, which I would assume the Qb fixed. If Qa's midrange, as-is, doesn't bother you, then there's probably no reason to upgrade. But keep in mind, I was comparing them to my Kappa 8s.
  3. absolve2525

    absolve2525 Super Member

    I don't have Qb, but I do have Qa. I read that enthusiastic review also. They surprised me with how well the drivers integrate. Perhaps the simple crossover in this model may contribute to that. Definitely a sleeper!
  4. Newk_Yuler

    Newk_Yuler Active Member

    Florida, USA
    I would wager a significant difference in perceived sound quality for the better with the Qb. Especially when doing a side by side comparison. My 2 cents based on fading memories and impressions while listening to incremental Infinity models side by side at the dealer in the early 1980s. I was 19 in 1980 and could actually hear the EMIT magnificence. Hooked for a lifetime.
  5. lissenup

    lissenup Active Member

    Vancouver, B.C. Canada
    I had a pair of Qa’s with one tweeter similar to your situation. I repaired the tweeter and used them until a set of Qb’s came up without the tweeters. I swapped the tweeters and two of the best of the four woofers into the Qb cabinets, removed the fuse protection and have found a significant improvement in the sound quality. The Qa’s definitely had a slight “hole” in the midrange, and the Philips mid that Infinity used nicely fills that deficiency.
  6. petes'picks

    petes'picks Well-Known Member

    North Denver Burbs
    I had both at the same time, I preferred the Qa. The b just seemed the upper bass was lacking on my examples and although it seemed to go lower it was boomier. Maybe more fill would of helped but they are long gone. My Qa's were let go also only because they were not taken of by previous owner.


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  7. Pyrrho

    Pyrrho Well-Known Member

    For a simple crossover to work well, one needs quality drivers (with no issues that one corrects with the crossover) and the drivers need to match very well. They don't tend to make complex crossovers because they want to get rid of some extra capacitors, inductors, and resistors!

    Most of the speakers I have really liked have fairly complex crossovers. I don't recall ever hearing a speaker I like as well as these that had an equally simple crossover. (For those who want to tell us about better speakers with such simple crossovers, these run the woofer full range and just have one capacitor and a variable resistor in series with the tweeter.)

    As for the original price, to confirm my memory, I looked at the Radio Shack catalog from 1978, when the Qa was introduced:

    Radio Shack had only two models of speaker that cost more than the Qa (and one of those was virtually the same price as the Qa). Most of their speakers were much cheaper. Although the Qa was a "budget" speaker for Infinity, it was not a budget speaker to the average person. Which is why I did not own any Infinity speakers back then.

    And looking at this inflation calculator:

    $300 in 1978 would be $1,155.40 in 2019. That is not a budget speaker.

    I would think that they *must* sound better, or else Infinity would not have made them and marketed them. But it seems very odd, given the glowing review of the Qa, especially the remarks about how well the woofer and tweeter integrate, and my own experience with my pair. Here is more of the review to which I previously provided a link:

    Our simulated live-vs.-recorded listening test also gave the Qa perfect marks for its upper-mid-range and high-frequency accuracy. We could hear some extra warmth in the lower mid-range or upper bass, but only upon direct comparison to the original "live" sound.​

    That really does not make it seem as though the midrange is lacking. And that fits my subjective impression. This makes me curious to hear the Qa and Qb side by side.

    As an aside, Infinity is not the only company that, in the 1970's, had two models of speakers where the difference was the more expensive one added a midrange. JBL did this with the L26 and the L36. Those also had 10" woofers. In the case of the JBLs, I have heard the three-way L36, but not the two-way L26. This is making me curious about the difference between those speakers, too. I don't know of anyone doing anything like this anymore, but I can't say that I pay attention to every speaker that every manufacturer makes, so it could be that someone is. Most of the time, when one goes up to a higher model speaker, one gets better bass (or possibly better treble). Usually, the difference is not just in the midrange.
  8. goodolpg

    goodolpg Just an old fart trying to help.

    Some random thoughts...
    The Qb seems well liked going by posts on the internet, and possibly even more so than it's successor the RSb which doesn't seem to have near as many positive statements on the internet as the Qb.
    Interesting (to me) is the fact that Infinity put a midrange control on the RSa even though it had no midrange driver (and even used that midrange control as a marketing tool in ads), was this an afterthought as to the Qa maybe lacking midrange? And I would think that simple change may have made the RSa crossover significantly different (more complex?) from the Qa crossover, though I have not actually compared the schematics.
  9. big&loud

    big&loud New Member

    I currently own a pair of Qa's, a pair of Qb's, a pair of RSa's, and a pair of RSm's.
    I bought all but the RSa's brand new back in the day.
    I had bought the Qa's after hearing a pair a buddy at work had. I knew nothing about the Qb's at that point.
    I went to the same store where he bought his, and picked up a set. I used them for the better part of a year then I happened into
    another store where they had the Qa's and Qb's both set up on a switch, I liked what I heard and added the Qb's to my system and put the Qa's on my 'B channel. I ran the system like that for a couple years till I decided to upgrade my amp. After some shopping around, I settled on an amp, and decided two fresh speakers were in order so I bought the RS monitors. I picked up the RSa's a few years ago at a yard sale needing a refoam job.
    Personally, now that I've had these all these years, the RSm's are by far my favorite, with the Qb's pretty close behind. Side by side, to my ears, the Qb's have the best sound. So much so that I've not touched my Qa's in a while, nor the RSa's.
    If I knew about the Qb's first, I'd have never bought the Qa's.

    As far as price, I don't know if I agree with all those inflation meters online. In 1979, I was taking home $325/wk. When I retired in 2016, I was taking home $485 per week doing the same job. Back in the day, the Qa's basically cost me a weeks pay. I don't think I could buy anything close to them these days for a week's pay now. I also bought a new Ford Fairmont back then, its sticker price was $4490, I drove away after paying $3750 cash. A comparable car to that today would be a Taurus, which costs around $28,000. The difference between a weeks take home pay and the cost of a new car has increased substantially. In 1979, it took me about 14 paychecks to pay for that Fairmont, today, I'd be looking at almost 60 paychecks to buy a comparable class car.
    I most certainly was better off week to week back then than I was as time went on. Wages didn't keep pace with inflation or costs. Cutting loose $300 back then hurt far less than doing the same these days. On top of all that, gas back then was about $.65 per gallon, I filled up this morning and paid $2.21 per gallon. The general cost of living has increased, the cost of quality products has gone up, but wages haven't kept pace. In fact, many wages are lower these days for the same job than they were 20 years ago. Top pay for an "A" rate technician in 1999 was around $24/hr. The top guy in most shops here now makes $15/hr. The lower ranked techs make even less. The difference between entry and top level pay is far less today then is was back then.
    Now that I'm retired, I make $22 less per month than I did when I was working collecting Soc. Sec. Only now, Medicare pays 80% of my medical costs rather than them coming out of my paycheck every week.

    There's no way I'd dig into my cash these days to buy a pair of $300 speakers, let alone anything higher. These days I'm limited to only what I can find used at fleamarkets, yardsales, and on Craiglist.
  10. swechsler

    swechsler Frog Whisperer

    7th row center
    A better comparison to your Fairmont would be a base model Fusion, which can be had for *about $20k (last time I checked, which I believe was the 2018 model year). Still more than what you paid, but on average, inflation-adjusted car prices have been fairly stable, at least for non-exotics.

    At the the time the Qa and Qb came out, Infinity was considered a high-end speaker manufacturer, and at one time they were the largest high end speaker manufacturer in the world (guess what happened). So while the Qa/Qb/Qe were not budget models when compared with something like the AR 18, when considered as entry-level high end, that gives you a better idea of where the pricing fell.

    *Just checked, the MSRP is now up to $22K.
  11. big&loud

    big&loud New Member

    I didn't buy a Fusion due to its size, the Fairmont was a fairly decent sized car, more along the lines of the earlier Granada or LTDII I suppose.
    The Fusion is smaller than the Taurus, which itself is a lot smaller than the old Fairmont. I wanted a new Crown Vic but they quit making them.
    Back when I bought the Fairmont, I was after a simple, easy to work on car I could keep a long time. I kept it about 10 years and traded it in on a Crown Vic.
    I needed a car with lots of room, I had been driving a 1971 Maverick back then and it was all but useless for carrying things like big speakers or even groceries.
    In hindsight, I should have bought the Fairmont wagon, but got that part right ten years later with the Crown Vic wagon, which I kept for 265,000 miles and 17 years.
    I moved up to a Town Car that year that I bought used. Its not a wagon but I used it to haul most of my system from my old house to here, including the 250ti's.
    I still have the TC, but bought the new Taurus because I wanted something newer to rely on since the 05 TC is getting up in miles. Hopefully I'm done buying cars. Being retired, I don't see
    me being able to afford any more new cars.

    Even the Fusion is more than four times the cost of what I paid for the '79 Fairmont, yet paychecks surely didn't increase by four fold.

    When I bought the first Qa and Qb's, I wasn't thinking high end or low end, I just bought what sounded right to my ears.
    The one thing I can say about the Qb's is that they seem to sound good on a variety of amps and in just about any room. They definitely like being on their original stands and they like a lot of power from an amp that can dig deep when it needs too.


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  12. Pyrrho

    Pyrrho Well-Known Member


    Okay, but what is it that sounds different? Is the midrange clearer, louder, or is it something else?

    Inflation calculators cannot represent everything; they must merely deal with averages. Some things go down in price, so they will not be properly represented by such things. And I don't know what job you had, but I am glad I did not have a job like that where the pay fell so far behind inflation. I would make a comment about minimum wage, but that would be a political comment and this is not a political forum. In any case, a week's pay for you did not keep up with inflation, and so you could not buy as much for a week's pay today as you could in 1979. That is not a fault of the calculator, but an unfortunate aspect of your pay. According to the calculator, your 1979 pay of $325 per week should have gone up to $1,074.41 per week in 2016, to have the same buying power. Anyway, I am glad you have some decent speakers that don't require much in the way of maintenance or repair (the Qa and Qb having butyl rubber surrounds on the woofers is good), so you can enjoy them without spending more money.

    As for cars, modern cars are much more reliable and require less maintenance than cars did in 1979 (remember all of those tuneups?). So it is difficult to compare, since the new one is better in many ways. I like the looks of some old cars, but when I think about the maintenance and reliability issues, I am glad my car isn't one of them, even though my car is pretty boring. But that boring is not all bad, as it does not give me the excitement of leaving me stranded on the side of the road or failing to start when I want to go somewhere. As for the gas prices, the prices you list fit well with the inflation calculator, as it seems to be about the same adjusted for inflation. Since your pay did not track with inflation, gas is more expensive for you now than it was then. I am sure it is much more upsetting to you, but I find it upsetting that people get paid as poorly as you have. People should be able to have a decent life (I hope that is not too political for this forum).
  13. Pyrrho

    Pyrrho Well-Known Member

    That comment about a midrange control on a speaker without a midrange driver made me curious, so I did a bit of searching and found the schematic for the RSa:

    The "midrange" control is affecting the crossover to the woofer. It is not a level control for the total output of the woofer (which would be silly since there is a control for the tweeter's level). I don't recall ever seeing anything like that before, but I don't spend a lot of time studying crossovers. The tweeter control simply controls the overall tweeter level, as is usual for such controls.
  14. chef free

    chef free AK Subscriber Subscriber

    Hayward, Ca
    I bought a pair of Infinity Qb for $400 in 1978. At the time that was a bunch of cash for a 17 year old kid slinging pizzas for $2.65/hr.! But when I went into Pacific Stereo, I listened to many speakers and the Infinity line caught my ears with their sparkling EMIT highs. I seriously considered and listened to the Qa, Qb, QJr. and the Q5. For the price the Qb was the clear winner. Yes the Watkins in the Q5 was impressive but not for $650! And the QJr. had a muddier bass than the Qb. But the Qb had a great sound overall so I choose them.

    Over the years I found I liked the treble (@10,000Hz) and bass (@ 100Hz) turned down a bit at volume. When I upgraded from a 20 watt Concept to a 45 watt "high current" H/K, it became clear that these speakers like power. However the H/K's bass tone control was crossed at 50Hz and turning it down didn't helped the sound, these speakers have a "hump" around 100 Hz.. Eventually, when I replaced the 12.5 uF cap on the mid, I added about 30% more stuffing to the box which tamed the 100 Hz "thump".

    Infinity recommended that these speakers be on a 12" high stand, they even made a stand. I've found that the mids image better toed way in but that the EMITs have less phasing with zero toe in. It's one of their big limitations.

    I never regretted spending that kind of money and I still have them in the family room today! $400 for 40 years of service is a great deal. If adjusted for inflation they would be about $1,600, I'll bet a nice pair of modern $1600 speakers would sound better though! If minimum wage had kept up with inflation, it would be about $11/hr...
    TomBig58 likes this.

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