Did you hear the Pi speaker sitting on top of that sub? The piano black stack? Could a DAVE drive that without a tube amp??? So you mean the Voxativ 9.87 is the powered sub that the Pi sits on top of and they are $10 k each, and how much is the Pi single driver PI speaker each? It looks like that goes down to 20Hz so why even need a sub??
Anyway you lost me with the word sweep. I like the idea of adding a powered sub to my Omega Alnico XRS floor standers driven by my HUGO2. How do you wire it to the HUGO2? Is a powered sub a stand alone speaker that picks up sound from the single driver with a microphone? Sorry I am so ignorant about this stuff as a newby.
Yes, the 9.87's (Pi*Pi) is the combination that has a Pi cabinet sitting on top of a bass unit (in my case, it was the piano black version). The unit I auditioned had the Voxativ AC-4D driver, which is the upgraded driver (basically same specs as the AC-4X driver, but with an extra 1dB of sensitivity). My BluDAVE drover it to room shaking levels with no problem at all. I suspect Hugo2 could driver it to comfortable levels no problem.
In this configuration, the Pi box on top has some dampers in it to cause it to naturally roll off around 100Hz. The bass unit is an active unit (it has a 250W class A/B amplifier built in), and has an equalizer built in. You tune the cross over and bass boost to what works best in your room. In the case of the audition room I was in, the bass unit was set to ~100Hz. Is this this bass unit that takes the response down to a VERY clean 20Hz.
It is possible to buy the bass unit separately (retail ~$10k) and use with any speaker you like. There is also a single driver of the bass unit for less money called the Voxativ Z (usually bundled with the Voxativ Zeth bundle, a more entry level line), but that is still retail $4k. The Voxativ Z has a single 96dB sensitivity driver (vs 2 96dB drivers in the Voxativ PI Dipole Woofer System, which is the bass unit in the 9.87's)
By "sweep" I meant getting a music file that is a frequency sweep from 200Hz down to 20Hz (these are all over the internet, I happen to use one from one of the Chesky discs). As the tone sweeps through the frequency range, I listen and adjust levels and cross over points and phase by ear until that it is as smooth as practical in your room (alas, at the low frequencies, nothing is ever ideal). You can also go the extra mile and get a calibrated microphone and some software that does the sweep and measurements for you, then make adjustments until it is mostly flat. This part of the process that I described would be the same with any subwoofer you're adding to the system. There are different ways to set up a subwoofer and blend with your speakers. I was describing the method I use, but at the end of the day you want have a smooth blend between your sub and your speaker.
If you want to learn more about this, there are lots of resources on the internet. I just saw that 2xHD released a "Audiophile Speaker Setup" disc: https://2xhd.nativedsd.com/albums/2XHDFT1095-audiophile-speaker-setup
If you page through the booklet PDF, there is a section about how your adjust a subwoofer to match your speakers, with some nice figures that highlight what you're trying to do. See:
https://dsd-files.s3.amazonaws.com/2xHD/2XHDFT1095/2XHDFT1095/2XHDFT1095.pdf
To answer your other question, a powered sub is basically a speaker with an amplifier built in. If you connect it to your source (in your case Hugo2 or DAVE), it takes the normal output of the source them amplifies it so the sub can get all the power that it needs. The trick is to set the "volume" level on the sub so that it matches the volume level on your regular speakers (this is the master level of the sub I was mentioned). The next trick is to adjust the sub so it it falls off as the speaker begins to ramp up. The sub can handle all the low frequencies then, and your speakers the other frequencies. The low pass filter helps set where that hand off will be, and the other adjustments let you fine tune it so it is smooth.
Both DAVE and Hugo2 are able to drive your Omega speakers and a sub at the same time (using 2 of the outputs)
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