Comparing Monitor 10's and RTA-12's
redsled
Posts: 21
I've got a pair of Monitor 10's that I like, and a pair of RTA-12's is available but a considerable drive. Except for the 2" larger passive radiator and external tweeter, they look very similar and aren't the drivers all MW6500's ? Is the RTA-12 a significant upgrade in sound quality over the Monitor 10 ? Thanks.
Comments
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RTA 12 every day all day
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RTA 12 every day all day
What is it about the RTA 12 that you like over the Monitor 10 ? -
It's time (phase) aligned.
I also believe Polk did something to address the comb filter issue inherent to the 10.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Are you looking at the first RTA 12 model or the later b or c series? IIRC, the early model was not phase aligned. I could be wrong, so someone else chime in. For what it's worth, I had 10's and RTA 12b's, and the 12's were much, much better than the 10's.
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Are you looking at the first RTA 12 model or the later b or c series? IIRC, the early model was not phase aligned. I could be wrong, so someone else chime in. For what it's worth, I had 10's and RTA 12b's, and the 12's were much, much better than the 10's.
The early ones were different in the fact that the part of the crossover that handled the midwoofers was less sophisticated. In the later ones you mention each midwoofer received a different signal to reduce the combing effect and were mirror imaged pairs marked L and R.
In my mind real time aligned or phase aligned refers to the design element employed where the tweeter is set back from the baffle that the midwoofers are mounted on.
I definitely drooled over the pictures of the early RTA12s in the magazines after I bought my 7Bs but it wasn't in the college kid budget.
Even if those are the early ones, you could follow the mods that @Jazzhead has done to his. He's very happy with the results.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Fortunately Polk already did the work and this is about as clear as the mud in the bottom of your coffee cup, but this gives you an idea of the engineering that is involved:
https://purifi-audio.com/blog/tech-notes-1/time-phase-alignment-acoustic-center-lobing-etc-14George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Thanks for the comments. These that I'm looking at are the original RTA12s.
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A time and phase correct speaker will have a step response like this.
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It’ll also have a first order crossover and robust drivers.
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It’ll also have a first order crossover and robust drivers.
The RTA12B was Fourth Order "Isophase" crossover. It would be awesome if someone with the early ones could draw the crossover networks that are in them.
https://us.v-cdn.net/5021930/uploads/editor/6y/9w66jw1hi3so.pdf
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Found a sketch in the archives not on official Polk Drafting Dept. paper but must be the early RTA12. It is Fourth Order but there is an extra shunt of a resistor and capacitor in series for the midwoofers which would be an impedance equalizer. Fourth order gives a 360deg phase shift at the crossover point, which means the drivers are in phase but one is a wavelength behind the other. Polk probably compensated for that by the relative positioning of the tweeter (correction - nope because that would be about 0.1 meters). Page one is apparently missing.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
The tweeter is where it's at to be (time aligned) with the woofers. In all cases I know of time aligned means all voice coils are on the same plane. If the tweeter was on the front bezel like the monitor 10 the tweeter voice coil would be in front of the woofer voice coils, hence not time aligned.
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@redsled
Are you looking to upgrade/modify the speakers you get, or run them stock? There is a modification that can largely mitigate the comb filtering/lobing issue with either model (the first generation RTA-12 or the 10) if you are interested. My experience is that the 12's will outperform the 10's, upgraded or not. Does the RTA-12 seller have stands for them (they sound better off the floor)?
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There is a 180° phase shift in the XO for the tweeter, therefore the tweeter in this model is wired out of phase to shift back into phase with the drivers.Gardenstater wrote: »Found a sketch in the archives not on official Polk Drafting Dept. paper but must be the early RTA12. It is Fourth Order but there is an extra shunt of a resistor and capacitor in series for the midwoofers which would be an impedance equalizer. Fourth order gives a 360deg phase shift at the crossover point, which means the drivers are in phase but one is a wavelength behind the other. Polk probably compensated for that by the relative positioning of the tweeter (correction - nope because that would be about 0.1 meters). Page one is apparently missing.
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There is a 180° phase shift in the XO for the tweeter, therefore the tweeter in this model is wired out of phase to shift back into phase with the drivers.Gardenstater wrote: »Found a sketch in the archives not on official Polk Drafting Dept. paper but must be the early RTA12. It is Fourth Order but there is an extra shunt of a resistor and capacitor in series for the midwoofers which would be an impedance equalizer. Fourth order gives a 360deg phase shift at the crossover point, which means the drivers are in phase but one is a wavelength behind the other. Polk probably compensated for that by the relative positioning of the tweeter (correction - nope because that would be about 0.1 meters). Page one is apparently missing.
Well I'm still learning but what I found says that for 4th order high pass and low pass there would be +180 deg phase shift for the tweeter but -180 deg phase shift for the woofer, so 360 deg total. But maybe that impedance equalizer (zobel network) addition to the woofer circuit effects things, phase-wise, requiring them to swap the + and - on the tweeter.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Thanks everyone for your input.
Jazzhead: I was asking about both the Monitor 10 and RTA 12 being in factory stock condition. The pair of RTA-12's in question do come with the factory stands.
When I auditioned my Monitor 10's I pressed with both thumbs on the passive radiators and the drivers moved outwards like they should. However, the other day I read somewhere that when I release the passive radiator the drivers should take at least three seconds to return to neutral position. Mine return right away. Will this cause a significant reduction in bass response ?
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Nope your doing it wrong. Of course when you release the passive it will suck the active drivers back in quick just like it pushed them out quick.Thanks everyone for your input.
Jazzhead: I was asking about both the Monitor 10 and RTA 12 being in factory stock condition. The pair of RTA-12's in question do come with the factory stands.
When I auditioned my Monitor 10's I pressed with both thumbs on the passive radiators and the drivers moved outwards like they should. However, the other day I read somewhere that when I release the passive radiator the drivers should take at least three seconds to return to neutral position. Mine return right away. Will this cause a significant reduction in bass response ?
You push the passive in all the way quickly, then count without releasing the passive until the drivers come back to rest.
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With your thumbs??? Where did you get that idea? Just use one hand.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
With your thumbs??? Where did you get that idea? Just use one hand.
Maybe they have a hand with 5 thumbs.
If so, pics are mandatory!
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Nah, no one wants to see that.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
AI comes up with stuff like that all the time (5 thumbed hands, supernumerary digits, etc.).
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mhardy6647 wrote: »AI comes up with stuff like that all the time (5 thumbed hands, supernumerary digits, etc.).
Easier to peel an orange 🍊 -
... and to climb trees.
