Explain "phase issues" please.
Most companies do as it is a cheaper way to get "full range" sound. And as long as you have a big enough room, you can get away with the phase anomalies and some of the challenges in terms of speakers placement to avoid room modes.
when the sub runs into the main speakers' range, then the port's output is out of phase with the mains, at various degrees. The result is audibly muddied bass in that region, and dependent on a system's resolution, it is easily audible. . . .
Is this true even if the sealed main speakers are playing down to 20Hz or 25Hz or so, and the ported subwoofers are low-passed to start at 20Hz or 25Hz or so?
when the sub runs into the main speakers' range, then the port's output is out of phase with the mains, at various degrees. The result is audibly muddied bass in that region, and dependent on a system's resolution, it is easily audible. Magico solves this in two ways: sealed, plus software-controlled cutoff (not crossover per se) at a certain frequency. Simply brilliant.
Finally, ported designs - main or sbs - always measure with a big hump at the port's resonant frequency, and that fundamentally bothers me.
Is this true even if the sealed main speakers are playing down to 20Hz or 25Hz or so, and the ported subwoofers are low-passed to start at 20Hz or 25Hz or so?
What you're hearing is modes, caused by overlapping phase, but you aren't actually hearing the phase itself - you may be hearing the character of the ported subwoofer as well. This will happen with any subwoofer.
...frankly, I no longer see the point of the ported subwoofer concept - why!
Note that the specs on the Wilson Subsonic include this wording: "10 Hz to 150 Hz. +0, -3 dB Room Average Response". Imo this implies Wilson is taking anticipated room gain into account. And by using the word "average", I think they are acknowledging that the real-world in-room response will have room-induced peaks and dips which will stray outside that +0, -3 dB window.
So the main reason I use ported subs - and I THINK the main reason Wilson uses ported subs - is so that we can do a better job of compensating for the room's anticipated effects.
The only thing is that with the Wilson system there is no speaker-level input, so one cannot use the REL system of tapping off of the outputs of the power amplifiers driving the main speakers. And I like the REL speaker-level system to drive the subwoofer amplifiers so the subwoofer amplifiers are infused with the sonic character of the amplifiers driving the main speakers.
Thank you very much, Duke, for this clear and understandable post!
This can be accomplished via something called a "voltage divider network", which derives a line-level signal from the speaker-level outputs on your power amps, with negligible effect on the amp/speaker interface. I presume the RELs incorporate a voltage divider network. Imo the maximum output voltage of the amp driving your mains, and the maximum input voltage of the Wilson active crossover, should be taken into account in designing the voltage divider network.
Thank you, Ron.
One of the implications of the higher power required to get equivalent SPL & -3 dB point out of a sealed box is, the amp and woofer have to work harder and correspondingly heat up more. A hot woofer motor + a hot amp + a compact enclosure can result in a short, exciting life for the amp.
“Voltage divider network” sounds like a fancy name for “potentiometer.”
It looks like a fixed L-pad, but with something perhaps along the lines of 22k Ohms for the series resistance, and 1k ohms for the parallel resistance... these are values I have used for a 200 watt (40 volt) amp, deriving a lower-voltage signal for my subwoofer amp's 12K ohm input impedance. So the power amp sees 22k Ohms in parallel with the speaker's impedance curve. With other amp/line-level input impedance (and input sensitivity) combinations the values would change.
See acks' respons above, exactly correct. Which is why I plug the ports in my speakers and tune with multiple sealed subs in my moderate - sized room.Ported designs are not "cheap" by any means, they are just another design strategy.
It is a convenient way to get deeper bass while sacrificing bass linearity and injecting phase misalignment. To procure deeper bass in a sealed cabinet designs often require increasingly robust driver design and power to adequately for such drivers. See Magicos as an example.Ported designs are not "cheap" by any means, they are just another design strategy.
How many budget speakers do you know employ sealed cabinet designs? Customers love bass, everyone wants 'full range". Stick a port in the back (usually) at the most beneficial diameter and depth based on the speakers' design and you achieve another 10+ Hz of low frequency output. Sealed, not so easy.Ported designs are not "cheap" by any means, they are just another design strategy.
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