Solved! Mixing high-end tower speakers & sub for theater system

[Habz]

I have high-end stereo speakers (Infinity Crescendo CS-3008 Speakers) and rejuvenated them by replacing the foam rings. Also have the Infinity 12” powered subwoofer to match. They sound (and look) great in the room (22’x15’) I want to turn this into a full surround sound system Without tossing these quality speakers. That means adding a center channel and rear channel speakers (and maybe side channels too). What would match these?

 

[Sonic Illusions]

You didn't mention the system that will be driving all of your speakers. The GOOD NEWS is that most all decent A/V receivers have ways to match speakers, using EQ, timing delay (depends on distance to listeners) and volume level adjustments. Some receivers use a test signal (pink noise) and a microphone and automatically EQ for "flat" response. No need to toss those Infinitys!

If you've gone total high-end with monoblocks for the mains, for example and a nice high-end DSP (ATMOS) and pre-amp, with dedicated high-current multi-channel amp for the surrounds (center, sides, rear and possibly ceiling), you have more flexibility and certainly better performance. My system has been fully calibrated for the room (20*25), with full acoustic wall treatments to avoid time-smearing reflections.

In order to properly integrate a sub into the environment, you need to know the low-end roll-off of your mains. Let's say you're at -3dB@30Hz. Your sub will need to "cross in" near that frequency or higher (choose "high-pass" point for mains, low-pass for sub), in order to not be too "heavy" at the bottom end of the spectrum. Most subs have built-in crossovers for this. Many A/V receivers and DSP pre-amps will be able to as well, in the speaker set-up section of the settings menu.

Being a high-end person, you most likely know this - One thing the A/V components cannot do is compensate for phase. Many subs have continuously-variable phase controls and some simply have 90 or 180 or both. Phase is CRITICAL in the performance of speakers, especially in the lower frequencies and out-of-phase mains or surrounds will TOTALLY destroy imaging. The alternative to those controls on the sub is to rotate the sub. This is experimental and depends on the configuration of your sub - which way the driver(s) is/ are facing has everything to do with acheiving the proper phase angles to reinforce the lowest octaves. Also, positioning the sub or subs in various spots in the room can have a positive or negative effect. Now, we're talking room modes, length of sound waves (40 feet @ 20Hz!!), cancellations, etc.... Integrating speakers into a room properly and knowing their response curves, room modes, timings, reflections, etc... can be a very complicated task, but the reward is awesome.

 

[Habz]

You didn't mention the system that will be driving all of your speakers. The GOOD NEWS is that most all decent A/V receivers have ways to match speakers, using EQ, timing delay (depends on distance to listeners) and volume level adjustments. Some receivers use a test signal (pink noise) and a microphone and automatically EQ for "flat" response. No need to toss those Infinitys!

If you've gone total high-end with monoblocks for the mains, for example and a nice high-end DSP (ATMOS) and pre-amp, with dedicated high-current multi-channel amp for the surrounds (center, sides, rear and possibly ceiling), you have more flexibility and certainly better performance. My system has been fully calibrated for the room (20*25), with full acoustic wall treatments to avoid time-smearing reflections.

In order to properly integrate a sub into the environment, you need to know the low-end roll-off of your mains. Let's say you're at -3dB@30Hz. Your sub will need to "cross in" near that frequency or higher (choose "high-pass" point for mains, low-pass for sub), in order to not be too "heavy" at the bottom end of the spectrum. Most subs have built-in crossovers for this. Many A/V receivers and DSP pre-amps will be able to as well, in the speaker set-up section of the settings menu.

Being a high-end person, you most likely know this - One thing the A/V components cannot do is compensate for phase. Many subs have continuously-variable phase controls and some simply have 90 or 180 or both. Phase is CRITICAL in the performance of speakers, especially in the lower frequencies and out-of-phase mains or surrounds will TOTALLY destroy imaging. The alternative to those controls on the sub is to rotate the sub. This is experimental and depends on the configuration of your sub - which way the driver(s) is/ are facing has everything to do with acheiving the proper phase angles to reinforce the lowest octaves. Also, positioning the sub or subs in various spots in the room can have a positive or negative effect. Now, we're talking room modes, length of sound waves (40 feet @ 20Hz!!), cancellations, etc.... Integrating speakers into a room properly and knowing their response curves, room modes, timings, reflections, etc... can be a very complicated task, but the reward is awesome.

The heart is an Onkyo TX-SR707. Yes, it does have a test mic to run the sound test that equalizes the system from the listening positions .
The subwoofer is an Infinity BU-2. It has a frequency range control which I set to avoid clashing with the drivers. I'm not savvy on much of what you describe there at the end; call me a lifetime aspiring enthusiast. You didn't mention anything about selecting the center channel or rear speakers. Those are what I am shopping for. But if I understand your response, I don't have to worry about trying to match brands or models. The receiver will adjust for it, yes?

 

[Sonic Illusions]

Yes, that's correct. If possible, if you stick with the same brand of speakers designed to work together, you'll have an easier time integrating them into the room. If you need more clarity with what I mentioned about phase angles - in a nutshell, you want the speakers working together to reinforce each other; the cones must be moving in the same direction. Do this experiment: listen to an audio track with good bass with just your mains on. Turn off your amp. Change the polarity of ONE of your mains (switch the -NEG to the +POS terminal and the + to the - terminal. Turn on the amp and play the same track. Sounds like total CRAP, right? The signals are 180 degrees out-of-phase with each other (cones opposite directions), cancelling the sound, destroying the bass and imaging. ALL SPEAKERS must be in-phase with each other in the room, at the listening position(s). The SUB is no different. It's critical to ensure phase relations between the sub and mains/ surrounds is as good as it can be, at the listening position. A continuously adjustable phase control is best. It can really pay off big-time to do this and it may also be necessary to experiment with different locations in the room to determine which is best, while adjusting phase at each. This is because room modes, where the sound waves interact, can also cancel certain frequencies.

Regarding choosing the low-pass cut-off: I would choose a point toward the upper useful end of the sub, 150Hz. The reason is to conserve the Onkyo's power. In the lower bass octaves, the amp is required to produce FOUR TIMES the power for each octave. It takes lots of power to move the air needed to reproduce low frequencies. Leave that to the subs' amps. Your sub amp delivers 100 watts, which really isn't enough for the lower frequencies in a 700 watt surround system. I advise getting another sub, because in full surround mode, your ONKYO is delivering 100W x 7 channels. The sub's job is to augment ALL channels, so you really need more than 100 watts to the sub in this setup.