• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Subwoofers make all big speakers obsolete?

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
6,442
Likes
6,485
Location
Brussels, Belgium
Subs also has disadvantages.

They are designed to operate below around 100Hz, which cause strain on the small speakers at high levels. Also achieving correct low pass filter at that frequencies is complicated as the small speaker’s fc is near the crossover frequency.

Finally, even if you have custom stands to place the small speakers on top of the subwoofers, the floor area is much larger than a floor stander’s.
Can you please explain why doing a crossover around the Fc is problematic?
 

DonH56

Master Contributor
Technical Expert
Forum Donor
Joined
Mar 15, 2016
Messages
6,551
Likes
12,640
Location
Monument, CO
I'd like my mains to play an octave below the crossover point if possible. Crossovers are not brick walls that drop to zero instantaneously on either side; they roll off gradually, so there can be significant energy an octave above and below the crossover frequency. It is easier to integrate subs when there is goodly overlap with the range that the sub can handle.

Copy of my old standing response to "why subs?":

I use subs, and have for decades, for all the usual reasons:

- Very (perhaps extremely) few "large" speakers actually play well below 40 Hz let alone 20 Hz. They distort heavily when presented with large bass signals (which most are -- see Fletcher-Munson) and driving them hard down low robs headroom for higher frequencies and causes distortion well above the fundamental signal frequency (harmonic and nasty intermodulation). Subs typically enable the mains to operate with much lower distortion.

- Very rare is the room setup such that the best place for stereo imaging and soundfield is the best place for the subs (or deep bass drivers) to counter room modes and such. Having independent subs provides placement options to smooth the in-room response. It is almost impossible to counter a null without subs (typically must move the MLP or change the room's dimensions though there are purpose-built panels that can also work). This is one of the things that led me to subs despite having quite capable mains.

- Powered subs offload the main amplifiers of the need to provide deep bass energy, providing more headroom and cleaner sound from the amplifiers.

- Music (let alone action movies) often contains deep bass content even if it is not real obvious. Kick drums, tympani, organ, sure, but also piano hammer strikes, plucked strings, beat patterns from instruments playing together, etc. May not really notice when they are there but usually obvious when they are taken away. Having subs fill in the bottom octave or three can make a difference.

- Purpose-built subs can provide high output cleanly at relatively low cost. The amplifiers and drivers need only cover a fairly limited frequency range so have fewer constraints upon them than woofers in a full-range system.

I do prefer main speakers with fairly deep bass and always have. Crossovers are not brick walls so a fair amount of energy still comes from the mains an octave below the crossover frequency. Higher-order crossovers allow you to reduce the overlap, but I still like having the capability. I have never really understood the idea of running "passive" bi-amping as implemented by an AVR (sending full-range signals to multiple channels and letting the speaker's crossovers separate frequency bands -- wastes amplifier headroom and seems to me of little benefit). Nor do I agree with the "plus" setting putting subs and mains in parallel; again, my idea has always been to isolate the two for the reasons above.

My first sub was a DIY design using an Infinity IRS woofer with my own control box to provide the crossover and a servo circuit using the second voice coil of the woofer. I had a Hafler DH-220 around so also incorporated a circuit to bridge it for use as a subwoofer amp. It worked well and the -3 dB point was ~16 Hz. I now run four small (F12) Rythmik subs using a similar (but updated) servo design with my Revel Salon2's and am happy with the result.

FWIWFM/IME/IMO/my 0.000001 cent (microcent) - Don
 

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
Can you please explain why doing a crossover around the Fc is problematic?
A speaker is a high pass filter. 2nd order slope if enclosed and 4th order if vented. Most small speakers have their fc (resonance frequency) around 60Hz. If you use a crossover at say 80Hz, then the slope will change below 60Hz. The slope of the driver will be added to the slope of the crossover.

My old friend Siegfried Linkwitz RIP explains it here. A layman explanation is here.
 
Last edited:

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
- Very (perhaps extremely) few "large" speakers actually play well below 40 Hz let alone 20 Hz. They distort heavily when presented with large bass signals (which most are -- see Fletcher-Munson) and driving them hard down low robs headroom for higher frequencies and causes distortion well above the fundamental signal frequency (harmonic and nasty intermodulation). Subs typically enable the mains to operate with much lower distortion.
Your argument is about the size of the woofer. What’s different between a subwoofer with a 12” driver and full range speaker with a 12” woofer?

- Powered subs offload the main amplifiers of the need to provide deep bass energy, providing more headroom and cleaner sound from the amplifiers.
If the main amplifier is struggling why the sub amplifier doesn’t?

- Purpose-built subs can provide high output cleanly at relatively low cost. The amplifiers and drivers need only cover a fairly limited frequency range so have fewer constraints upon them than woofers in a full-range system.
Why not just biamp large speakers?
 

DonH56

Master Contributor
Technical Expert
Forum Donor
Joined
Mar 15, 2016
Messages
6,551
Likes
12,640
Location
Monument, CO
Your argument is about the size of the woofer. What’s different between a subwoofer with a 12” driver and full range speaker with a 12” woofer?
You do like to argue.

I am not quite sure your first question. Audyssey and most room correction programs have two settings for the main speakers: "small" and "large". Nothing to do with subwoofer size. What the two settings really mean are "use bass management" and "do not use bass management" so determine whether band-limited or full-range signals are sent to the mains.

As for physical size, it is not about woofer size per se, but about the capability of the main speakers (and amplifier driving them) to handle very LF content without distortion. Subwoofers typically have greater excursion and power handling than main speakers, and include large built-in amplifiers significantly more powerful than an AVR. There are speakers that include built-in subwoofers, some active, of course.

If the main amplifier is struggling why the sub amplifier doesn’t?
See above. Subs typically have much larger amplifiers inside than an AVR as well as purpose-built drivers. Using a subwoofer also means the main amplifier does not need to provide extremely LF signals where most of the power is required (see Equal Loudness Curves).

Why not just biamp large speakers?
Cost and complexity. The vast majority of AVRs do not provide true bi-amp capability (just separate full-range outputs) so the user would have to add an external crossover and integrate the system. Many, perhaps most, inexpensive AVRs do not even include preamp outputs to use with a crossover.


And of course all of this leaves out one of the primary reasons for separate subs, the ability to place them in the room to help counter modes and smooth the overall bass response.
 
Last edited:

sigbergaudio

Major Contributor
Manufacturer
Forum Donor
Joined
Aug 21, 2020
Messages
1,192
Likes
2,093
Location
Norway
I'd say obviously yes because most subwoofers have more capacity than even pretty large floorstanders, so it will be fullrange in the proper sense of the word. But depending on which speaker you choose to pair it with, you may be lacking in midbass. Integration is not always trivial either. But if all is done well, the result can be better than a floorstander.
 

puppet

Senior Member
Joined
Dec 23, 2020
Messages
346
Likes
212
That is if you've integrated the sub as a 3rd way, crossing much higher than a sub's defined range.
 

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
You do like to argue.
This is a forum. Do please check the meaning of the word. You don’t have to reply.
Cost and complexity. The vast majority of AVRs do not provide true bi-amp capability (just separate full-range outputs) so the user would have to add an external crossover and integrate the system. Many, perhaps most, inexpensive AVRs do not even include preamp outputs to use with a crossover.
Why are you constrained with the use of an AVR or the niche case of a HT when arguing if subwoofer with small speakers vs large speakers? Your question has nothing to do with HT.

FYI, you don’t need a special biamp capability. All you need is a Y adapter! Biamp doesn’t require a crossover.

Besides, you need a subwoofer anyway for the LFE channel (unless you feed that to the LCR).
 
Last edited:

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
That is if you've integrated the sub as a 3rd way, crossing much higher than a sub's defined range.
How can you do that with a standard active sub?
 

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
I'd say obviously yes because most subwoofers have more capacity than even pretty large floorstanders, so it will be fullrange in the proper sense of the word.
Why? What’s stopping a floor-stander to use a 15” woofer? The Revel Salon2 has an equivalent of a 14” woofer.

How many subwoofers you know that can match the high SOL distortion of, say a JBL M2 at bass frequencies?
 

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
The LFE inputs usually bypass the sub’s electrical low pass.
Wasn’t aware of that. Just read the user manual of a REL subwoofer and it wasn’t clear on that.
 

DonH56

Master Contributor
Technical Expert
Forum Donor
Joined
Mar 15, 2016
Messages
6,551
Likes
12,640
Location
Monument, CO
This is a forum. Do please check the meaning of the word. You don’t have to reply.
Did I use it wrongly?

argue

är′gyoo͞

intransitive verb​

  1. To put forth reasons for or against; debate.
  2. To attempt to prove by reasoning; maintain or contend.
  3. To give evidence of; indicate.
The American Heritage® Dictionary of the English Language, 5th Edition.

Why are you constrained with the use of an AVR or the niche case of a HT when arguing if subwoofer with small speakers vs large speakers? Your question has nothing to do with HT.
Did not say I, you, or anybody was constrained to use an AVR. But I think the majority of folk are using an AVR. My original response, from 10+ years ago, was in a thread on a forum about HT systems. And yes my original post was meant to encompass "all" audio systems.

FYI, you don’t need a special biamp capability. All you need is a Y adapter! Biamp doesn’t require a crossover.
The benefits of bi-amping require a crossover that a simple Y-cable will not provide. Using a Y-cable sends a full-range signal to all drivers so you are still using all the voltage swing of all the amplifiers (power may be reduced, but most amplifiers are constrained by voltage) nd using the passive crossover within the speakers. In that case the potential benefit is primarily isolating back-EMF from the HF and LF sections of the speaker, IME negligible particularly for SS amplifiers. In addition to the amplifier and speaker headroom issues a crossover helps alleviate, using a crossover to isolate the frequency bands allows more flexibility in placing the subwoofers to optimize in-room frequency response.

Besides, you need a subwoofer anyway for the LFE channel (unless you feed that to the LCR).
Yes, but that is HT (movies and some multichannel music) only, and of course as you say it could be fed to the main speakers. Especially if as you argue they can handle the LF energy. Many stereo recordings include significant low-frequency energy. You can of course use bass management in your AVR/AVP or whatever to send those signals to your sub(s).

Rather than continue to argue/debate/converse/whatever you call it every statement I make, it may be easier if you simply create your own post to counter my post and correct all my mistakes. I have to get back to work...
 

More Dynamics Please

Addicted to Fun and Learning
Joined
Nov 18, 2020
Messages
562
Likes
716
Location
USA
Concerning crossover slope THX tried to establish an industry standard for a system consisting of sealed satellites, subwoofer and AVR with appropriate crossover slope that was described in a hometheaterhifi.com feature article:

The THX crossover consists of an 80 Hz, 4th order Linkwitz/Riley filter alignment, and it was not chosen lightly or without serious consideration. As the crossover frequency increases, it becomes harder to blend the subwoofer with a satellite, and the subwoofer becomes more difficult to audibly "hide". At the same time, as the crossover frequency increases, distortion from the satellite decreases, the total dynamic range increases, and loading the room for the flattest response becomes much easier. The logic of the 80 Hz crossover point is that it's high enough to ease demands on the speakers and amplifier, but low enough to make the whole setup work without a tremendous headache. The 4th order (24dB/octave roll-off, 6dB/octave/pole) Linkwitz/Riley alignment not only offers a steep slope, but one that immediately transitions to that slope, maximizing the benefits of that slope near the crossover point. The high-pass side minimizes excursion and power requirements, while the low-pass minimizes more localizable content at higher frequencies.

To correctly achieve this, THX satellite speakers are sealed systems with an 80 Hz –3 dB low frequency cutoff (preferably with a Qtc of 0.71). The electronic high-pass filter applied to them is an 80 Hz, 2nd order (12dB/octave) Butterworth alignment. The speaker and the filter sum to a 4th order Linkwitz/Riley roll-off which matches the electronic filter applied to the subwoofer, and an excellent crossover is achieved.

 

DonR

Major Contributor
Joined
Jan 25, 2022
Messages
1,223
Likes
2,155
Location
Vancouver(ish)
I have towers and a sub. Due to room placement constraints, the sub is... suboptimal. I prefer to listen to music in stereo with no processing as the towers extended down to 40Hz which is enough. HT, of course, is always better with a sub as mine goes down to 28Hz and rolls off slowly after that. I cross it at 100Hz with the towers which simply cannot match the sub for HT content in SPL but are more accurate due to placement issues. In retrospect, however, it's not that big an issue and I could easily live with bookshelves and a sub for everything and probably should have gone down that route.
 

sarumbear

Major Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
4,568
Likes
4,138
Location
Southampton, UK
The post title declares but also asks a question:

Subwoofers make all big speakers obsolete?​

I tried to explain that in general the declaration is false as a subwoofer doesn’t bring any objective benefit.

A floor stander can easily have more SPL capacity than a subwoofer with a small speaker. Almost all floor-standers have at least an equivalent of a 12” woofer. Two of them means the total woofer size is 14”, similar to a large subwoofer with a 15” woofer. A hefty floor-stander like the Revel Salon2 has equivalent of a 14” by itself, or larger than a 18” subwoofer in total.

We have not even touched the problem of SPL limit of the small around the subwoofer.

Not to mention we must use a DSP based crossover due to the high-pass filter slope being affected by the driver.

Now tell me why subwoofers make all big speakers obsolete?

This is an objective forum, I appreciate arguments that are objective too.
 
Last edited:

thewas

Major Contributor
Forum Donor
Joined
Jan 15, 2020
Messages
4,757
Likes
10,568
The main advantage of subwoofers is their addictional freedom of placement while for example big floorstander placement is in most practical cases a compromise between imaging and bass/SBIR.
 

TimVG

Major Contributor
Forum Donor
Joined
Sep 16, 2019
Messages
1,175
Likes
2,497
I was curious so I looked: this is your 74th thread on speakers alone.
 
Top Bottom