Adjusting front L/R crossover on the Amp without a Sonos Sub
After my initial setup and tweaking with the grouped Sonos systems with Q Acoustics speakers, I put it through its paces with a variety of music like Pop, Indian – Bollywood, Indian – Classical, Rock, Disco, Jazz, Oldies, Western Classical etc. I also tried out a few movies with Atmos soundtracks. It was great, but after a while, there was a nag.
The bass at certain frequencies felt too powerful with an edge of boominess. It was not evident always and depended on the soundtrack producing those frequencies. It was somewhat in the mid-bass range. In those cases it actually seemed to overpower some of the midrange and even caused me a bit of fatigue with bass-heavy music.
I was going to tweak the usual bass, treble and sub audio controls when it occurred to me that the Q Acoustics and the Sonos Sub in the Arc group had bass overlap. I had alluded to this in the earlier post but did not pay much attention at that time. The Q3030i can go down to 46Hz while Sonos Sub in the Arc group likely crosses over at a relatively high 96HZ – 100Hz range. This is based on what I read elsewhere. So, we have a significant overlap among the two speakers that is making that range overly powerful. The Q3030i are two-way bookshelf speakers so, if I could set a low-end crossover, it will take the bass load away and let their woofers handle midrange better. Once set, a crossover also adds a high-pass filter to the front speakers to block any frequencies below the crossover point reaching them. The Sonos Amp lets us set a crossover, but only with a subwoofer connected to the Amp. In my setup as described in the previous post, I have the Sonos Sub bonded to the Arc along with surrounds in a 5.1.2 configuration. The Amp is setup as a stereo. Unfortunately, the Sonos Amp tries to be smart and does not provide a crossover control if a subwoofer is not connected to it. I was not going to get another Sub for the Amp just for this!
So, I started looking for possibilities for a dummy subwoofer like load. The Sonos Amp sub out is an RCA line-level output that needs a powered sub. After quite a bit of digging this PAC LC1 RCA level control seemed like a good candidate that puts a 50K ohm dual gang potentiometer across the output. However, I also read that the Amp just tries to detect a connector on the RCA sub out. That means that an even cheaper simple RCA cable should also work. I eventually decided to get a 3.5mm female to 2RCA male audio cable. I had a cheapo powered computer speaker lying around. So, if plugging in a cable did not work, I could then simply connect my computer speaker’s 3.5mm input jack to this to provide an actual load. The speaker will be off and not producing any sound. Interestingly, plugging in just the cable actually worked! The crossover control popped up in the Amp’s Sub Audio section in the Sonos App.
This allowed me to experiment with different crossover settings. I tested the Q3030i speakers alone first, without grouping with the Arc surround to identify the effects of the crossover. The Sonos app allows to easily toggle the Sub audio on or off and made it easy to compare the effect of the crossover. I used some bass-heavy music for testing and eventually settled on a crossover frequency of 96Hz. I also set the Amp’s sub audio level to the minimum of -15. I was not trying to get an actual sub output on the Amp, just wanted the crossover control. The difference was not huge but the effect was quite clear. Taking out all the bass below 96Hz from the Q3030i immediately made them more clearer and detailed with the midrange. It seemed as if a small valve had been opened allowing more clarity through. The woofers are not having to deal with the heavy lifting below 96Hz. I grouped them back to the Arc set and then tested with movies. Dialog was much clearer and distinct. Both vocal and instrumental music showed differences. That slight boominess had disappeared. Explosions still rocked (thanks to the Sonos sub) but with tight control.
The journey still continues. I am having fun and learning a lot of stuff while also enjoying all the music along the way.
The Pseudo Random Bit Bucket 