Frequency Response

No and no but that’s just me.

There’s been many threads about using multiple subs in a DBA (distributed bass array). You might want to look that up. There’s also digital means of integrating the sub/s into the system, to help it be more seamless. Not seem less.

As there is still quite a bit of information in that region and below. You’re going to miss out on the development of the full spectrum found in most music that has any percussion instruments.

Giving a more specific answer would require more information, like room size and dimensional ratios, transducer type used, and there’s no definitive answer here on always using a sub.
Even for a stand mount 45Hz seems a little light in the bottom end (especially in room), why did you choose the particular loudspeakers you’re using?

@rixthetrick - I am pondering speakers that go to 45Hz - I haven't heard them live yet but I like the design.  My current speakers go to 35Hz - so its just a thought.  As always in this hobby - you have opinions on both sides of the argument.  I haven't used my ears yet to make a decision but thought it might make for a good discussion.

not personally, depends entirely on whether you think you have enough bottom end, nothing else..

45hz could be adequate for most music if the frequency response is flat at 45 hz and started to roll off at that frequency. I doubt that it is but you must factor in the roll off when doing comparisons. Some speakers that say they go to 45 hz actually start to roll off much higher and you would certainly need a sub for decent bass.

Also consider what 35hz really means as well.......

Also consider what you might accomplish, bass wise, by placing your speakers to take advantage of bass nodes in your room.
 

FWIW

For me 36 Hz can be low enough to not need a sub but 20Hz is a lot better on those recordings that go that low. 

It depends upon how the loudspeaker was measured, your taste in music and how loud you listen.  I'll tell you why if you divulge the name of the loudspeaker and the size of your listening room.

My opinion is yes and yes. I was surprised how much low bass is present at 30Hz. or below. I'd say try at least one sub, you can always sell it, and if you buy used you won't lose $$ should decide it's not for you.

In short, yes and yes.  I went from floor-standing speakers rated to go down to 30 Hz, to large stand-mount speakers that go to 40Hz (2x9-inch woofers in each sealed box). I then added two subs made by the same manufacturer.

The bass from my current system is far superior to what I had with the floor-mounted speakers because the sealed box provides more detailed bass down to the ballpark of 40Hz and the dual subs get to 20Hz with impact. This combination loads the room much better and the subs have a remote control so I can quickly add +1 or +2 or take away -1 or -2 to adjust the bass response for the volume I happen to be listening at and for the music I am listening to. IME, it is hard for a single speaker to cover the entire frequency range and do justice to the bass. Not saying it can’t be done but rather that is is not always done well.

I would like to add a third or fourth sub and would also like to run my main speakers through a high-pass filter (at 40-45Hz) so the amps and speakers do not need to work so hard on the low end. Fortunately, as recommended by the manufacturer, the speakers sound good rolled off naturally below 40Hz, my amps have the power to drive them without working too hard, and it was fairly easy to integrate the subs at that frequency. If not done in the digital realm, the trade-off of using a filter is comparing the benefits resulting from requiring less effort of the amplifiers and main speakers against the detriments with respect to what it does to the sound of the signal above the high-pass point.

@polkalover 

Yes you should use at least one sub. Your speakers bass response depends a lot on placement and on the room itself. The placement requirements for your mains to provide good images and tonality are different from the requirements to provide adequate bass. For good bass, your speakers need to be close to room boundaries. For good image and tonality, they need to be away from your walls. Subs are the only way you can get both without compromise. And then there are these pesky room modes…

45hz +-3db? 6db?  What's the SPL at 45hz? 

Maaaaaybe...

The manufacturer specification and the the measured in-room response are different, and the decision to include of subs depends on the latter as well as the individual preference and ambition. 

@erik_squires 

Nice article.  It’s well written and well executed  I appreciate your honesty when you said:

”Lets be honest, these are not typical results.  This happens to be the combination of my speakers, room, listening location and, very importantly, room treatment.”

Back in the real world, DBA is how we do it, you know that. 

1st, measure what you are actually getting in your space.

https://www.amazon.com/gp/buyagain/ref=ppx_yo_dt_b_search_bia?ie=UTF8&ats=eyJjdXN0b21lcklkIjoiQU40QkNTUzc3OExSRiIsImV4cGxpY2l0Q2FuZGlkYXRlcyI6IkIwN1lT%0AOTQ0MkMifQ%3D%3D%0A

get one with threads for a tripod mount, set it up seated ear level at your listening spot. 

measure what you say?

this test cd has 29 individual 1/3 octave bands, 

you can measure as setup, alter the toe-in a bit, move in/out of corners ...

you will definitely learn something.

now compare what the speaker's specs say and what you have been/are getting. you might be surprised how much bass you think you have and how much bass your mic thinks you have.

Just use your ears and listen. Placement is important but not measurement.

Definitely. My remote controlled subwoofers are simply fun. With the exception of certain LP's I prefer the systems presentation with the subs on and using various gain settings. 

SVS offers a painless trial period that might help you decide. I can't speak to their quality. 

The low frequency response for my speakers is 26Hz +/- (1.5 dB anechoic). At my rooms listening position they fall to 0dB at approximately 31Hz. My subwoofers most used customized EQ preset is just over +2dB @ 37Hz -18Hz as well as the variable Q, slopes and filters.  

@onhwy61 the room size is 17.5X14  and the speaker is the muraudio SP1.  Once again haven't heard live but like the design.  Do I get a decoder ring and secret passcode?  I listen to a broad spectrum from rock/hard rock/pop/jazz and classical played from loud to ears bleeding to background music

my speakers are -3 db at 32 hz and a pair of REL made a wonderful difference

For $20K and not hearing the speaker I'd ask if they took it to Canada NCR anechoic chamber for testing since they are made in Canada. If so ask to see the spins.

 To the OP, pay attention to the posts from @djones51, ​​​​@onhwy61 above

it starts with how the speakers were measured and the room 

your working with. 

A proponent of DBA.

I might.  I been there and done it.  It depends.  But only 40+ hz is a good reason to consider it.

Polkalover, the loudspeaker you are considering doesn't do really loud, let alone ear bleeding.  Keep that in mind.

The bass response is spec'd at 45Hz for a -3dB rolloff as measured anechoic.  With room boost that should give you very usable bass down to around 35Hz.  For nearly all music types there is very little music below that frequency.  There's sound, but not a lot of music.  Pipe organs and some electronica excepted.  As an example, the lowest note on a 4 string bass is 41Hz and for 5 string basses its 31Hz.  But modern recording techniques typical roll off these frequencies in order to not muddy up the recording.  So at moderate to somewhat loud volumes you really don't need a subwoofer with that loudspeaker in your room.  But that doesn't mean you won't like it better with a subwoofer.

My last speakers were Salk Songtowers. In this room bass was good...really good. For me, no need for subs. They were fine...let’s just say...I worried about other things than if subs were needed.

But my last house. Holy smokes! The mid bass was a shade less fullsome...but low bass was much deeper. On some tracks it just took my breath away. I could not wrap my mind around how deep 38hz felt.

But 38hz...measured in what way? I guess every manufacturer ’presents’ their numbers differently. Just like every room presents sound differently.