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Discussion Starter · #1 ·
Hey folks,


While not DIY per se, the QSC K12 speakers sure seem to do a lot of things right. They run about $800 street ea. 75 degree horn on top matched to a relatively low crossover point (for a p.a. speak) see here: http://www.qscaudio.com/products/spe...re=directivity


in order to match directivity of the woofer to the horn for a smooth power reponse. Then they throw in active power (1000w class d, 500 woof x 500 tweet) and DSP that I'm sure corrects some frequency response issues and time aligns the drives. Additionally, the high sensitivity drivers make that 500 watts per drive really add up in spl.


These K12's seem to do a lot right for the money and I was wondering if anyone had experience with them and what opinions were.

http://www.qscaudio.com/products/spe...series_K12.php


Too bad we can't find the money to buy a set for a "listen around" thing where each person chips in some cash to hear them and then forward the speaks to another guy. If we could by some miracle get QSC to kick in a set, would there be any interest in paying the "shipping only" to audition a set then forwarding to the next guy? On this paragraph, just thinking out loud. Main questions are up above.


QSC's site kind sucks for navigation, so you have to scroll way down on the right to link to some of the features. Just a heads up.


for example, here is a whitepaper on the dsp correction:
http://www.qscaudio.com/products/dsp...paper_2007.pdf


I'm not sure how I found it...just kept clicking around...


Here is the frequency response before and after DSP. With a linear power response, on axis dsp changes will affect total sound power, so this linear frequency response should be preserved off axis as well.


The net response appears to be +/- 1 db from 80 hz to 20 khz, which is pretty good. I suppose that we could get into phase and ask about that, but doesn't phase response change with distance, so if you are far enough back it shouldn't matter?




I will cross list this in the speaker forum as I don't think that would be considered out of bounds.
 

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QSC have a good engineering pedigree and aren't fools, so I'd expect them to perform well in the desired application, possibly better than a lot of the competition. But that doesn't mean they'll transition well to home (though I suspect they will).


Best bet would be to get to a store where they have some and try them out. Not a perfect plan, but you'd at least have a better idea. I'd be interested to hear what you tjhink of them if you do.
 

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had a pair of K10's for a short while before they were installed with another pair in a nightclub. Also had a single K12 (Its all I could get) We sat down in front of the K10's for about 3 hours. The other listener used to have his own speaker company (designed in NRC). Both of us have been involved for many many years mostly having listened to B&W,Energy,Mirage,Martin Logan,Totem model 1) Genelec, etc.

We were impressed by how smooth they sounded. No unwanted horn "honk". High's were natural & detailed. Midrange sounded fine & powerful. Bass tight & powerful but not deep. The volume was low to moderate to really compare against hifi stuff. We knew the QSC would destroy hifi speakers at at high output.

I think a surround system would be awesome & WAY cheaper than just about every active design out there. Once & awhile I thought I heard a slight resonance from the cabinet (plastic) but I was being very picky. I myself wonder about K vs KW series. Basically KW has or is replacing the HPR series. Its basically the same but with a wood cabinet.

I love my Genelec 8050 but I have to admit 5 - 7 QSC (whatever's) would save a ton of money & have way higher output. Recommended.
 

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yeah these thing look like a really good deal for lcr's


you can also get the baffles from the qsc store, the baffles contain the waveguide.
 

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I'd be interested to know what drivers they are using. I'm not sure they are doing anything extraordinarly unique. There are a few similar JBLs.


It would be cool pull the drivers and amp and put them in a nicer cabinet with roundovers. Almost all SR cabs have tons of diffraction and the plastic ones ring like mad especially when the woofer is playing up to 1.5khz or so. For $700 + $50 in plywood you could have a pretty awesome powered HT speaker. Well beyond anything retail HT/hifi at that price point.


I'd be most interested in the KW153 though. I'd bet their 3-way would work best. These speakers all use mediocre drivers which is what keeps their prices down. A 3-way would take some of the load off the woofer and CD.


The JBL PRX635 would be tough competition. It uses Zilch's Econowave horn for the top end and a midhorn that is similar to the new ScreenArray 3730 but smaller. It will hold directivity much lower and play the drivers within a cleaner range. I'd like to compare the QSC KW153 and the JBL PRX635.


I'm curious which drivers the KW's use now. If it is the same as the HPR series I'd give the nod to JBL when it comes to raw drivers in this case. QSC might have better waveguides though and the amp/dsp section is likely a wash.


I know many people want the JBL cinema stuff but these will get you similar performance to the entry level JBL cinema for less money and smaller packages. In fact, when you take into account the included amp/dsp it might even be a better performer than some of those.


It would be nice if QSC would publish spec papers similar to JBL (and many other pro manu's) that have pretty detailed FR and polar plots. I wonder if that stuff is available.
 

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I've always been a proponent of these. Like others,....I too feel these are a tremendous value for a HT application. The QSC philosophy is absolutely bullet proof build, and these shouldn't fail you in a residential environment. They're plastic, composite whatever, but handling them imparts a nice sense of solidity. One can easily do much worse.


We all have seen the stereotypical AVS audio newbie, hitting us up with the standard "here's my room, I want impact, I want this, I want that", then they pursue some sub-par, lower sensitivity, passive two way HiFi speaker. The smallish LF section is woefully inadequate for any reasonably linear realistic output below 300hz, and breaks up and Doppler modulates the MF,...then hands off to some $10-$20 HF driver (with no measure of directivity control) that cannot, under any circumstance produce realistic playback levels.


Perhaps this two way is powered by a multichannel AVR, and when all channels are driven during peak demand, can't meet spec. The source material's special effects average levels become muted due to the AVR's PS being taxed, and the two way entering compression. Additionally, the peaks are simply lopped off from the output stage's clipping from demanding peak-to-average levels. What energy is imparted to the room's acoustic is done so in a manner whereby no directivity is used, thereby illuminating the entire room, and bombarding the LP with more reverberant content, less direct energy.


Rant over.


One can easily do much, much worse than a room full of active two ways from QSC. The AVR's burden is eased, the speaker cabling issue (if any) is removed from the equation, Multiple power supplies feeding local amp stages, the signal tracking ability of each frequency section, of each channel is appropriately handled, signal shaping is employed, focusing the forward radiating energy is addressed, low distortion, high capability drivers with much less compression than the passive example.


All this adds up to addressing some of the key elements in HT loudspeakers; dynamics and lack of compression being experienced by the layperson is quite extraordinary. The ability for the widely dynamic signal voltages of demanding material, to be tracked and handled in a manner that immerses the listener in the realm that the engineering team intended can't be over-stated in my opinion. Yes, other aspects of audio reproduction in the home are important, however in HT, allowing the dynamics to pass through in proper scale, and without significant non-linearity, is a very key component to the suspension of disbelief.


Typically, once one experiences this sense of dynamic realism, it's difficult to go back. These QSC two ways are not the be all, end all. Actually, one can do much better at a higher price level of course. Like other active, signal shaped, high output, low distortion designs, they are nice, turn key approach toward eliminating many of the issues plaguing loudspeakers tasked for HT.


I've got to stop here
Sunday moring coffee,..btw,... I've been up all night , many friends/aquaintances invloved in truss roof collapse last night.
 

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Preaching to the choir FOH. Very well said. When I first listened to a set of Tannoy V12HPs in my living room next to a set of more expensive hifi speakers I was blown away. It didn't matter the source material, music or HT it was night and day. The V12HP's aren't even particularly refined. The stock crossovers are very basic and a few tweaks definitely cleans them up.


These entry to mid level powered SR speakers are a great way to get pro level dynamics and directivity control. It amazes me how much people spend on their receiver when the differences are minimal. Buy an entry level receiver in the $500 range instead of that $2000 model, pair it with something like the K10 and call it done.


FOH, I didn't mean to imply that the plastic cab's are terrible, just that a nice baltic birch or MDF cab would be an improvement. Add in some nice roundovers and flush mounted drivers and horns too. These are relatively minor but IMO worth the effort. SR cabs aren't built with that in mind, but that is about the only change I'd make.


BTW, are you in Indy? I live just outside of Indy. I had some friends at the concert and they were leaving when the storm was hitting because they didn't want to get soaked. Their seats were a few rows from where the truss hit. Terrible.
 

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Quote:
Originally Posted by coctostan /forum/post/20820639


Where were you able to find that? Are there parts lists for these speakers?

On the QSC site in the support section......parts lists, CAD drawings, specs, par #'s ....i googled the QSC number and scanned through the results for celestion and got a few hits for the Celestion model i linked. I can't say for sure as QSC may have an OEM program with celestion but they used a lot of off the shelf B&C and 18 sound stuff in their older systems so who knows. The Celestion CD's are off the shelf as well.
 

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Thanks Mayhem, I found the CAD drawings. The K and KW series seem to use the same drivers. They've upgraded the compression driver significantly from the CDX1-1445 in the HPR to either the 1.75" coil CDX1-1731/1730 (not sure which one). This should allow them to cross down around 1200-1500hz which the 1445 couldn't do.


The 2-way K and KW should best the JBL 2-ways because JBL uses a weaker CD which forces a higher cross and a poor directivity match and requires the woofer to play beyond its comfort zone.


The K12 for $700 is an absurd value. The CD alone sells from QSC for $130. There is something to be said for mass production.


Here is what you can get for $750 in home hifi and it is passive: Polk Rti A9 - http://www.crutchfield.com/s_107RTIA...ck.html?tp=185


Or you could go with the K12 for $700 and it is powered by a better amp than what you will find in nearly any AV receiver.


Comparing the two, the Polk only wins in aesthetics, size and extension. Performance wise, it is like a Porsche vs a Kia. If only QSC would put it in a decent looking box they would have a world beater. It would still be a little wider than most would like, but come on!



I did notice the K series uses a molded baffle with a bunch of diffraction inducing elements. That's too bad, but I'm sure it is part of how they are able to sell at such a great price. You'd have to go to the KW to DIY the enclosure. The only differences I can see between the K and KW are the ply vs plastic cabs, molded baffles vs a separate horn and different waveguide profiles.
 

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Discussion Starter · #13 ·
also, just in case anybody cares, many more and richer replies in the diy section than the speaker section on this question. :) great info guys.


the hpr122i is crossed at 2khz, which seems a little high for a 12 inch driver. the k12 is crossed at 1.2 khz, which seems more reasonable.


i'd be interested if anybody knows which driver is used and what the distortion plots look like in the k12.


there is a parts list for the hpr122i, but i could not find one for the k12, though the qsc site isn't exactly easy to navigate, so i'll keep looking or maybe send them a note.


seems like the jbl prx612m is the comp from jbl and looks ok, but also crossed at 2khz or so.


for a buy vs. build, another interesting option appears to be the new vx series from tannoy (vx12). i'd like to hear that one.


then again, the diy route is probably the way to go. maybe something around that crazy nice and equally crazy expensive 18 sound 12" coax, the 12cx800 iirc.
 

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The problem associated with these composite "Pro" speakers is oftentimes their waveguide/horns ring. They need damping as many DIYers employ like duct-seal, or equivalent type stuff. A simple tap or knuckle rap can easily spot potentially problematic issues. Also, coctostan is right, they could really benefit from diffraction lessening round-overs,.. etc. They simply do so many things right for the price.


Here's a killer litmus test that quickly separates the men from the boys; with a mic, mic pre and a power amp, listen to your voice through a single speaker. You can quickly either dismiss, or accept a speakers ability, especially in the all important midband,...if it can't render the midband as well as another suitor, cross it off the list and move along. If one were to perform that with the Polk mentioned above, vs the K12,...I'm betting the K12's low distortion ability to render voice at realistic levels would crush the otherwise solid Polk.

Quote:
FOH, I didn't mean to imply that the plastic cab's are terrible, just that a nice Baltic birch or MDF cab would be an improvement. Add in some nice roundovers and flush mounted drivers and horns too. These are relatively minor but IMO worth the effort. SR cabs aren't built with that in mind, but that is about the only change I'd make.

These budget PA speakers can be offered so reasonably priced for several reasons, however chief among them is simple injection molded composite cabinets. Yes, good multi ply Baltic Birch is preferable, but as I'm sure you know it's a different market/approach.


In general, the value offered for good entry level PA speakers is tremendous if one is reasonably careful with which one. I once did an live event, and important live event,..whereby the label brass was in attendance, and it was a CD release party. Got in a bind, a terrible bind. The normal mains I was using couldn't be used. So I used these single 12" two way Yamaha compression HF mains. These were maybe $300 new. I had one per side, on top of (4)JBL 15"s per side. These cheapo Yamahas kicked ass
, and many, many good things came from that evening. At the time, my normal rig woulda been a processor based Apogee AE 5 system. The Yammies are obviously an entirely different box, but I'll tell you, they fared pretty well. I don't remember, but the Apogees were likely at least $2k apiece, or more. This wasn't some corporate gig either, this was balls out, full tilt, visceral show (a least the (8)15's
). I raised the cross, eliminating some of the strain from the Yammies and never looked back.


Point being, if one could find the ideal box for your room, there is superb value in the sound reinforcement loudspeaker market.


Here's the closest thing to them,..actually look the same;



Here's a link.


I'm in no way recomending these for HT, their cabs are really budget.

Quote:
BTW, are you in Indy? I live just outside of Indy. I had some friends at the concert and they were leaving when the storm was hitting because they didn't want to get soaked. Their seats were a few rows from where the truss hit. Terrible.

Yep, outside Indy. Many friends working the event. I went outside with the dog, called the rest of the family outside as the initial front blew through,...wicked stuff there. Then came in as the rain began and my cell started going crazy. Very sad evening as details poured in
 

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Quote:
Originally Posted by LTD02 /forum/post/20821190


drivers used in the hpr series 12" (hpr122i)

http://professional.celestion.com/pro/pdf/TN1230.pdf

http://professional.celestion.com/pro/pdf/CDX1-1425.pdf

I mistyped the 1425 as 1445.


The KW and K series all use 1730 or 1731 (it spec's a Celestion 1.75" coil neo CD and those are the only two, not sure which but they don't look very different) are much more robust drivers than the 1425. It is a bump from a ~$50 driver to a ~$130 driver. The 1425 is dead below 2khz. The 1730/1 is good to 1.2khz but no lower.


The bottom line is that on the 2-way JBL PRX series and QSC HPR series speaker the bean counters beat out the engineers by spec'ing a cheaper CD. There is nothing inherently wrong with the JBL 2408 or Celestion 1425, but they won't play below 2khz which causes the designers to play the woofer higher than ideal. Those woofers are beaming pretty badly up at 2khz especially the 15s and it isn't exactly in their comfort zone either.


QSC came out with their marketing term "DMT" or "Directivity Matched Transition" which isn't exactly a technical achievement as it is an accounting battle won by the engineers. JBL (and most others) match directivity, but not usually at those price points because it takes a more expensive CD. Even I know how to match directivity.


QSC has definitely put some R&D into the waveguide though and that is worth quite a bit there. It is especially surprising given the price. JBL has more trickle-down effect, but I think the QSC wg's are just as advanced.


FOH, I'm in Westfield and I was shoving my dog out the door as the storm hit. It wasn't too strong aside from heavy rain up here.


How cool would it be to program the DSP in these speakers. For one of us to buy the equivalent amp/DSP would cost more than the K12 alone. Anybody think they can hack the DSP code?



BTW, you can find the parts list stuff at http://www.qscaudio.com/support/tech...rt/schems3.htm
 

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Quote:
Originally Posted by coctostan /forum/post/20821727


I mistyped the 1425 as 1445.


The KW and K series all use 1730 or 1731 (it spec's a Celestion 1.75" coil neo CD and those are the only two, not sure which but they don't look very different) are much more robust drivers than the 1425. It is a bump from a ~$50 driver to a ~$130 driver. The 1425 is dead below 2khz. The 1730/1 is good to 1.2khz but no lower.


The bottom line is that on the 2-way JBL PRX series and QSC HPR series speaker the bean counters beat out the engineers by spec'ing a cheaper CD. There is nothing inherently wrong with the JBL 2408 or Celestion 1425, but they won't play below 2khz which causes the designers to play the woofer higher than ideal. Those woofers are beaming pretty badly up at 2khz especially the 15s and it isn't exactly in their comfort zone either.

The higher end QSC models (ie. QSC HPR-152i) actually use the Celestion 1745 CD which I found to be a very viable CD and at its price tag it sounded much better then my Selenium comparison. The CD is $70 on QSC parts ordering. Not sure where the $120 is coming from?
 

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umm... 80 to 20k? Looks like 800 to 20k to me.


I'm guessing that's the plot for the waveguide only. Not saying that its bad, though. Wish they had shown some off-axis plots.
 

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Quote:
Originally Posted by coctostan /forum/post/20821093


Thanks Mayhem, I found the CAD drawings. The K and KW series seem to use the same drivers. They've upgraded the compression driver significantly from the CDX1-1445 in the HPR to either the 1.75" coil CDX1-1731/1730 (not sure which one). This should allow them to cross down around 1200-1500hz which the 1445 couldn't do.


The 2-way K and KW should best the JBL 2-ways because JBL uses a weaker CD which forces a higher cross and a poor directivity match and requires the woofer to play beyond its comfort zone.


The K12 for $700 is an absurd value. The CD alone sells from QSC for $130. There is something to be said for mass production.


Here is what you can get for $750 in home hifi and it is passive: Polk Rti A9 - http://www.crutchfield.com/s_107RTIA...ck.html?tp=185


Or you could go with the K12 for $700 and it is powered by a better amp than what you will find in nearly any AV receiver.


Comparing the two, the Polk only wins in aesthetics, size and extension. Performance wise, it is like a Porsche vs a Kia. If only QSC would put it in a decent looking box they would have a world beater. It would still be a little wider than most would like, but come on!



I did notice the K series uses a molded baffle with a bunch of diffraction inducing elements. That's too bad, but I'm sure it is part of how they are able to sell at such a great price. You'd have to go to the KW to DIY the enclosure. The only differences I can see between the K and KW are the ply vs plastic cabs, molded baffles vs a separate horn and different waveguide profiles.

If the ed cinema are done correctly then i think those will be the best buy over the QSC/JBLs
 
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