Got a subwoofer, but I'm not so sure I need it. Help :)

[audiofooled]

Yes!
2x10" 40 Hz @ 100 dB SPL=3.4526
VS 4x7" the same =3.5231 Xmax.

If you say so, than yes. 7 inch drivers can have 3.5 mm excursion, no problem. In fact, in a ported box, at 40 Hz, they would hardly move at all. Ok, so do 10 inch drivers...
But that wasn't my point, that is if we look at the OP and this setup. He paid money to get a 12 inch sub, which alone (at 40 Hz) would theoretically extend itself by a whopping 1.3mm in order to produce equal SPL as 4x7. Bellow the mains tuning frequency, which is a bit higher than 35 Hz (-3db), the 7 inch drivers will start to roll off much more rapidly than a sealed sub would do. They will use room gain, but so will the sub, and then some, being a sealed one. https://www.audiosciencereview.com/forum/index.php?threads/analytical-analysis-room-gain.23211/

The lower the frequency, the mains will go more and more in excursion, until they can't handle no more. A sub will still be happy about it. So this stuff is rarely apples to apples. Perceiving low notes because of the room gain does not sound the same as having a dedicated transducer handle it, with no audible distortion.
In a sense, it can be true that we don't need subs until we hear a properly integrated one. You are right, for music we rarely need anything lower than 30 Hz. And some subs are certainly overpriced for what they are. But there is certainly audible difference, there are advantages in using them, there are people who like it flat to DC. Each to their own. It's a hobby.

 

[ZolaIII]

@audiofooled it's not me it's calculator so try to pin it on him. You are aware that each and every siled sub use Linkwitz transform function incorporated towards max driver excursion rate /power in order to even come close to ported one regarding bottom end response, how you said apples to apples. That chenges things a lot or you think otherwise. I have and use two siled 10" sub's which do the job for me just fine (30 Hz 0 dB up to 115 dB SPL) and with a lot of headroom in real use while I cut them under 26 Hz. Actually I use all sealed enclosure mains and sub's and in half treated room. I don't have anything against hobby even if it's exaggeration nor I have a nead to feel physically vibrations, actually running away from it and with experience working with stage equipment in the paste. He bought the sub and he doesn't hear difference so he probably doesn't need one aside from learning curve to integrate it. I am not a fussy guy who doesn't know how to do it nor a young monkey who would exaggerate and feal impressed by doing so. In the end if you like to experience a jet plane take off realistic or sound of nuclear explosion that's fine with me.

 

[Tom C]

Found this measurement on line. The top graph is the impedance curve, the bottom is the FR on axis and listening window.
Based on this data and the information provided by the OP, I have to think there is considerable bass boost from the room set up. If one were to pull the speakers further out into the room, I expect the measured response to have significantly lower bass.
This, of course, was realized by the OP, and built into his query. Even high passing the mains and choosing a higher crossover frequency for the handoff between sub and mains may not change things a great deal, simply because he’s getting so much boost from the room. In fact, I think this might be too much bass for me even without the sub, and I usually like to have a bit extra.

 

[audiofooled]

To me it was never about bass quantity, my mains in room dig down quite similar as the OP's, and they get plenty loud, no issues there. It was the uneven FR in the bass region that motivated me to build, a 12 inch sealed sub. It is seamlessly integrated, and when it comes to bass quality and articulation, the difference is night and day (at MLP). For even better response throughout the room I would need another sub, located exactly where my wife likes to sit. So, I'm out of luck.

Hearing is getting less and less sensitive the lower the frequency, so that may be a factor. OP's measured response, even though it's by phone app, and volume set to 40%, shows about 5db boost in the region he crossed the sub to, and that is a lot. But for the subjective perception, maybe not, or at least not at modest SPL. Room gain is often a reason why people think they don't need a sub, and room modes are the reason they do. I can imagine that with better integration and REW-Umik1 the measurable results would be a lot better and more perceptible in the entire bass region.

 

[Tom C]

Take a look at the 100Hz region, in the first graph, the one without the sub and no crossover. There’s quite a boost below that frequency, and above it drops like a cliff.

 

[audiofooled]

Take a look at the 100Hz region, in the first graph, the one without the sub and no crossover. There’s quite a boost below that frequency, and above it drops like a cliff.

It drops because it measured only 20-80Hz sweep. Red line is max hold, showing maximum reached only for this frequency range ...

 

[Tom C]

It drops because it measured only 20-80Hz sweep. Red line is max hold, showing maximum reached only for this frequency range ...

Well, you’re right, he does state that. I guess I forgot that when I saw the red trace continue on up the frequency spectrum. Where is that coming from, if it doesn’t actually represent a measurement?
in that case, I don’t think we have enough information to guide decision making. Why not go ahead and do a full sweep?
We also don’t have anechoic distortion measurements, so we don’t where at what point in the response the bass distortion rises.

 

[audiofooled]

It's just a fun FFT app which uses your phone's mic. IMHO, without calibration, as trustworthy as those SPL meter apps. Also, at lower frequencies it is highly dependent on mic FR. I'm not so confident phone mics are made for 20 Hz. The rest of the spectrum is either the remnant of the max hold not reset from previous use, or ambient noise picked up. The red line represents max SPL at frequencies measured all day, if you don't reset it.

 

[Digital_Thor]

Another thing. Get that subwoofer away from the mains.
When the mains play well into the lows, you then need the subwoofer to be somewhere else in the room, to excite different modes and create better possibility for a smoother response. As you already found out.... you won't see much difference when adding a sub, when the sub mostly sees the exact same acoustical situation - as your right main.

Third thing. Try writing Yamaha, and ask if you can use the pre-out to link back into the XLR input. This way, you could add a 4 way DSP to EQ both mains and subwoofers - and chose any filter/slope/level and everything. Though.... fair warning... this is going down the rabbit hole. But it could also potentially make your system sound way better

If the loop-around works. You can free up a lot of power in the Yamaha, by relieving it from producing the deepest bass. Since your mains jump down to 3 ohms - I wouldn't fully trust that your Yamaha likes that - further encouraging the DSP loop through, to relieve it from the deepest bass duty.
The overlap, that you should aim for with any sub/main combo, is used to average out the response. The whole way of thinking filter slopes and phase, is way different for bass, than for midrange/tweeter arrangements. Wavelength, and our perception of hearing, is the key to grasping this.

 

[notsodeadlizard]

"Got a subwoofer, but I'm not so sure I need it."

Urgently buy a second subwoofer and the situation will become clearer