Im so confused. I tried reading and it made it worse!
CH46E
Posts: 3,591
On the rta12b or any front loaded polk PR speaker does the radiator move the same direct as the powered drivers? I thought i have read somewhere that they dont operate like most people would assume.
I was under the impression that when the powered driver pulls in so does the radiator (how is beyond me) hence they are in phase? Or does it push the pr out like i thought it would.
O teying to figure out how to set up my new subs. Thefe will be on beind the couch facing the polks at the fron of the room but the sub (for now) is rear fire port. Then there is the same sub in the front of the room facing the couch but it is front port ( for now).
My plan is to source two more drivers. Two in the fron and two on the rear behind the couch.
To minimize phose issues wjatbwould you guys do? Down fire sub? Fron fire rear port or vice versa? I ha e been reading for hours. Please help.
My jead feel like it going to explode.
I thought maybe some band pass boxes since id only have ro deal with the port ditection for phase????
I was under the impression that when the powered driver pulls in so does the radiator (how is beyond me) hence they are in phase? Or does it push the pr out like i thought it would.
O teying to figure out how to set up my new subs. Thefe will be on beind the couch facing the polks at the fron of the room but the sub (for now) is rear fire port. Then there is the same sub in the front of the room facing the couch but it is front port ( for now).
My plan is to source two more drivers. Two in the fron and two on the rear behind the couch.
To minimize phose issues wjatbwould you guys do? Down fire sub? Fron fire rear port or vice versa? I ha e been reading for hours. Please help.
My jead feel like it going to explode.
I thought maybe some band pass boxes since id only have ro deal with the port ditection for phase????
Comments
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Maybe a bit of sleep would help?
PRs work off the pressure in the enclosure and the tuned mass of the PR along with the inherent delay that happens between the compression of the gas (air) and the inertia of the PR to keep things in phase once the PR becomes active when approaching it's tuned frequency. At least that's how I understand it to work.
As far as sub integration, because of placement and possible room nodes, you're just going to have to experiment to see what works best at the LP. You may also find that you need to adjust the frequency at which the sub comes in to avoid a phase interaction. A few sweeps with a tone generator off you phone should get you in the ballpark. -
A passive radiator serves the same purpose, physically, as the mass of air in the port of a ported enclosure (Helmholtz resonator). Compared to a traditional "bass reflex" port, though, it has a steeper rolloff and a more complicated response curve.
For this purpose, the important thing in the borrowed figure above is the shape of the response curves (not the frequency responses per se).
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Electromechanical transducers (speakers!) don't move air as much as they excite it. Wave mechanics is a little non-intuitive if one's not used to thinking about waves. Energy moves through a medium when a wave propagates -- but the medium itself incurs no net motion.
This doesn't mean (of course!) that you can't feel the effects of a "wave" -- but it's not the same as a breeze!
EDIT:
good ol' The Internet
In terms of bass reinforcement in a real room -- can't beat empiricism, I'd opine!
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good old The Internet^2
This isn't exactly cogent, but it may help to illustrate what happens in a real room excited by real sound waves
source: http://www.cambridge-mt.com/ms-ch1.htm
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https://youtu.be/g3hhcSxI6Cw
Remember that the water in which these waves is propagating does not, of necessity, move in a net fashion itself.
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Ported and bassive-radiator speakers are not phase-accurate in the way that acoustic-suspension speakers are. A ported-or-bassive speaker can be frequency-accurate within it's frequency-response limitations, but not time-accurate within it's frequency-response limitations.On the rta12b or any front loaded polk PR speaker does the radiator move the same direct as the powered drivers? I thought i have read somewhere that they dont operate like most people would assume.
The port or the radiator goes progressively more out-of-phase as the frequency lowers. At some point the port or radiator is 180 out-of-phase. I suppose that a speaker could be made where it's so out-of-phase in the bass that it comes around full-circle (360 degrees) and is back in phase again. -
Double post. Sorry.
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Ahhh crap, that just (all good info) made things worse.
So forget all the technical munbo jumbo, how should i arange 4 10 inch subs. Two in each cabinet ported. One on the front wall and one on the rear wall.
Options are front fire rear port.
Front fire front port.
Front fire with port to the ground by raising the sub 3 to 5 inches off the ground. Or downward fire with ports also downfire.
Or i could do upward fire with ports in any direction.
What would you guys recomemd i do to minimize any phase issues. I run the rta12b full range. I do use the subs for certain musics. Sometimes i run the SRS2 in there also.
My HTR (Yamaha Aventage RXA1050b i love this htr.) runs a parasound amp for the fronts. But it is a 7.2 with YAPO with the reflective so and so. I dont remember the acronym. Unfortunatly i have only seen it do the bass calibration for one sub even though they are both plugged in. And they play both subs on opposite side of the room at one time for thier messurment.
The subs are the pretty Infinity C.M.M.D. cone. Id like to be able to show them off but not at the cost of sound quality. It might sound funny to pick them but i love thier ability to hit the lows and get that kickdrum. They really are a nice driver.
And WOW. Sorry about all the typos in the first post. I hate this Samsung phone. Thanks for bearing with me. -
I dig this guys set up. For sale on the bay now
In CALIFORNIA. Same drivers i have.
If i could get a taller box like this for a smaller foot print would be awesome. Heck, id eaven mount them to the celing or half way up the wall if i thought it would sound better. -
So -- I don't know... but you can experiment, you know? Put them someplace, run a low frequency sweep and listen to what happens (first and foremost, at the listening position). Any response anomalies (nodes and antinodes) will be readily apparent.
I am sure LF sweeps are available as files you can play on a phone or -- whatever if you don't happen to have an audio frequency sweep generator gatherin' dust someplace.
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Here's a good picture of how a ported enclosure works, from the user guide to speaker system simulation software called Basta!.
http://www.tolvan.com/basta/Basta!UsersGuide.htm
This shows the relative contributions of the speaker driver (woofer) response and the response of the port to the overall "system" LF response of the driver in the ported box. It also shows the phase in the top panel; not the "sudden" reversal of phase at the resonant frequency of the port (35 Hz, in this example).
The System response (black) / Driver response (solid blue) / Vent response (dotted blue) / Electrical impedance (dashed green). It can be seen that the vent response has a peak at 35 Hz, which is fp [the resonant frequency of the port] for the vent. Above this frequency, the contributions are in-phase and the system response becomes greater than the individual contributions. Below fp, they are out of phase, and the system response level becomes lower than the individual levels.
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Oh, one more thing (as Lt. Columbo used to say)...
there was recent discussion somewhere on these forums about elevating a subwoofer. I really like that idea in principle. Unfortunately, I cannot find the darned thread (it was in the last few weeks), but I guess the takeaway is that you can think about positioning your subwoofers in three dimensions, not just two!
Probably not what you (the OP) wanted to hear, though
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@mhardy6647 that diagram shows exactly why I'd make the port tune another half octave lower... extended the system curve and allow the room gain to bolster any dips at the bottom end.
For me, any sub used for music reproduction had better be able to hit 27.5Hz or it's not worth putting in the system. The graph above shows only a low E and not the low A that an orchestra or organ can hit. -
Hey Mark @mhardy6647 - I think this is the thread you were looking for. It's an older thread, but Dan brought it back to life very recently.
http://forum.polkaudio.com/discussion/110168/raising-sub-woofer-level/p1mhardy6647 wrote: »there was recent discussion somewhere on these forums about elevating a subwoofer. I really like that idea in principle. Unfortunately, I cannot find the darned thread (it was in the last few weeks), but I guess the takeaway is that you can think about positioning your subwoofers in three dimensions, not just two!
Probably not what you (the OP) wanted to hear, though -
Ported and bassive-radiator speakers are not phase-accurate in the way that acoustic-suspension speakers are. A ported-or-bassive speaker can be frequency-accurate within it's frequency-response limitations, but not time-accurate within it's frequency-response limitations.On the rta12b or any front loaded polk PR speaker does the radiator move the same direct as the powered drivers? I thought i have read somewhere that they dont operate like most people would assume.
The port or the radiator goes progressively more out-of-phase as the frequency lowers. At some point the port or radiator is 180 out-of-phase. I suppose that a speaker could be made where it's so out-of-phase in the bass that it comes around full-circle (360 degrees) and is back in phase again.
So getting ported subs to be "mostley" in phase is going to be difficult.
I dont notice any issues per say during movoes. But when i want to play music at high volume where the rta12 cant keep up in the bass department i do notice issues. Ive experimented and can either get killer slam but no boom or vise versa.
I used to have a M&K MX150 (push pull 12's) never could i get it to sound right no matter where im the room i placed it. But thats when i was useing JBL L80ts.
Now that i have one sub in front and one in the rear its great. But im looking for a bit more spl. Tha5s why i wanted to go with 4 subs. 2 in front 2 in the rear. I may juat try feont fire front port amd run the rear sub 180 degrees out.
I have a very "hard" room. Tile over concrete, 2 of the 4 walls are cinder block filled with concrete and very little insulation between the 1x2's that the drywall is on. Then the other two walls are interior but insulated for some frigging reason. Was PITA to fish them.
Thank you guys for the details. I understood about 1/2 to 2/3 of it. Lol.
I will take a look at that last thread about elevating the subs. I was thinking about hanging them. It would allow me to build the giant family seat near the back wall.
Thanks again guys.
