There's a lot more bass in a 6.5" driver than most of you think

One topic of discussion I often see new audiophiles touch on is whether to get larger speakers for more bass.

I usually suggest they tune the room first, then re-evaluate. This is based on listening and measurement in several apartments I’ve lived in. Bigger speakers can be nothing but trouble if the room is not ready.

In particular, I often claim that the right room treatment can make smaller speakers behave much larger. So, to back up my claims I’d like to submit to you my recent blog post here:

Look at the bass response from those little drivers! :)

I admit for a lot of listeners these speakers won’t seem as punchy as you might like, but for an apartment dweller who does 50/50 music and theater they are ideal for me. If you’d like punchy, talk to Fritz who aligns his drivers with more oomf in the bass.

To be clear: I am a big fan of subwoofers.  :) I have a 15" Hsu. I don't mean to advocate against large speakers, or against subwoofers at all.

What I do want to say is that the path to great bass starts with the room. Whether you are going to stick with a 2-way monitor, upgrade to larger or start adding subwoofers, a well treated room is the shortest path to bass nirvana than all other paths.
I have several of the Purifi Audio 6.5 inch drivers on order. By manufacturer specs and now 3rd party test reports these maybe the best out there. They have a unique surround that will reduce a polarity of shear from returning back into the cone. I don't think they realize that function. Tom
I have several of the Purifi Audio 6.5 inch drivers on order.

Very cool looking.  Would hate to have to replace the surround in 10 years though! :)

Let usu know how they measure @theaudiotweak .



In 5 yrs there will be someting better. If someone else understands how to reduce interfering energy all the better..mostly accidental in many designs and material shapes..Will let you know. I will also be applying materials from Perfect Path Solutions to this driver and magnet structure and also to the inside of the poured granite cabinet. What I have experienced with the PPT products is amazing. Also some other tuning methods that are used in string instruments that can be modified and adapted from my patents. It's all a continuum.  Cant wait. Tom
My mission Cyrus 781 have a 6 inches bass driver with a potential so good that I dont give a damn now to connect the Kreisel subwoofer I bought 2 years ago... :)

My tweaks, Helmholtz resonator, and room treatment, with an audio system at his highest potential level is more than sufficient... Who needs 20 hertz or even 30 ? The important thing is the clarity all across the spectrum for me....
Subs when properly implemented increase midrange clarity, solidify  and  increase soundstage dimension and space. The Purifi driver itself has a resonant frequency of 30 hz.and can be used in a rather small box. This driver will be a drop in replacement for most Seas and Scanspeak  6.5 in. drivers. Tom
This driver will be a drop in replacement for most Seas and Scanspeak 6.5 in. drivers
no it will not. Its unlikely to fit the exact size hole and every driver must be custom tuned to the box. No such thing as a drop in replacement. 
and erik is wrong again. 

A 6.5 inch woofer must not do bass. Its too small. You need big 15 inch woofers to do bass. And doing bass and mids is a horrible compromise. Erik is all wrong. 

Yep, Erik.

As an owner of the Joseph Audio Perspective speakers I know what you are talking about.  Their (even smaller) dual 5.5" long-throw woofers continue to blow me away, often seeming to sound even deeper and punchier than the big Thiel 3.7s the replaced (3 way with 10" woofers).

As John Atkinson, a man not unfamiliar with the performance of many speakers, said in his review of the Perspective2:

----  "When the kickdrum was doubled with synth dropped-bass notes, I was astonished by how much clean, low-frequency energy four 5.5" woofers could pump into my room. " -------
I was astonished by how much clean, low-frequency energy four 5.5" woofers could pump into my room.

yeh right. And he would be even more astonished if i replaced those small woofers with 12 inch woofers. 

Read the 3rd party test reports..does your 'Puter reach Europe and the Netherlands? Tom
and erik is wrong again.

A 6.5 inch woofer must not do bass. Its too small. You need big 15 inch woofers to do bass. And doing bass and mids is a horrible compromise. Erik is all wrong.

I've got the measurements that illustrate and prove my thesis.  You've got two hands holding air.

yeh right. And he would be even more astonished if i replaced those small woofers with 12 inch woofers.

You really don't understand what's going on (or the point) do you?
It's sort of amazing.

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Subs when properly implemented
increase midrange clarity, solidify and increase soundstage dimension and

Absolutely true.   The problem is always proper implementation.
+1 for Fritz speakers. Have had a pair of his Carbon 7 MK II speakers -(here is a link to the Carbon 7 MK 11 spec page-
I have Definitive Technology - SuperCube 2000 7-1/2" 650W Powered Subwoofer with crossover and phase control for anything under 35HZ....barely hear the sub except for very low sounds and sometimes don't event hear it at all. This is for more of near field listening in a 20X25 room with speakers and listening in an 8' triangle....Sound is amazing...just ask Fritz for a loaner for 30 days and hear for yourself !
My Dali Epicon 6 speakers have fabulous bass with this size driver.  I use Perfect Path Audio mats, cards and paste on my speakers and they seem to now play like 12 inch woofers. No kidding. Fun. 
I was actually astonished at the bass quality out of my Graham Chartwell LS3/5's. Now those are small speakers! Of course it helps that they are in a small room,but I was still amazed.
Read the stereophile review of diamond 225's...6.5 inch woofer, wave guide soft dome tweeter, and an unusual port on bottom of reviewer was astounded to see usable bass frequency output down to about 31.5 hz! Now that's nuts. Sure it was down several decibels from its rated 45 hz, but it was there and significant....pretty close to his words. I can attest to this as mine never fail to amaze me for a lousy $449 bucks! Freaking great speakers....
For sh#ts and giggles I just grabbed a pair of vintage recoaned the smaller advents with the fried green egg tweeters and the spit ball woofer, they are 4 ohms and I will drive them with my rogue sphinx, should be a blast! Acoustic suspension speakers are special.
In my experience small woofers are not satisfying for long.  There's something wrong with the punch they produce.  Small woofer speakers that produce deep bass rely heavily on port output and that is slow and low resolution.  I don't think you need a huge woofer but 8" is the minimum for reasonably deep bass and punch that can satisfy long-term.  Surface area is very important.  
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one reviewer was astounded to see usable bass frequency output down to about 31.5 hz
The woofer would need to move a huge distance to do that. Why push a small woofer to its limit when you could just use a bigger woofer? Do you think you can have your cake and eat it?
I’m just stating what they found when reviewing the speaker (the 225’s) and in my own listening room I have to agree that Peter comeau (the designer) did a hell of a job with the budget he had to work with to design a speaker that can satisfy most. As herb Reichert put it, it’s an audio conissuer component.
Certainly there are of course better speakers! But for $449 you will be hard pressed to find one that sounds this good for that kind of cash outlay period.
To me, I find it far more satisfying and rewarding to not have to spend a fortune yet get a large slice of audio heaven. I grin every time I listen to these darn things, they are hard to walk away from and just keep you wanting to listen...I think that is what this hobby is supposed to be about really. Not who spent the most on this and that. You do not need to spend a ton to get quality, not in today’s hifi world.
There are numerous components I could list that fit this mold, including the outstanding Hana EL cartridge, the discontinued Shure m97xe cartridge. the musical fidelity v90 dac, and the AKG k550 headphones to name a few. Ton of quality for not a lot of dough.....another one was the marantz pm6005, a killer integrated amp that I unfortunately sold. 
I heard a Devialet Phantom today.  It's a $3k, 4500W bluetooth speaker that absolutely blew my mind.  The two bass "engines" are about 6-7' diameter.  Frequency response is a real 14Hz (-6dB).  Very impressive for its size.  You should've seen the excursion on those drivers!  
The Devialet cheats!!! :D

OK, so the two 7" probably have about the same effective area as a 10", but you are right, they have massive excursion capability, much more so than any other 7" speaker should have.
I have the Soliloquy 6.3i pair. 6.5 woofer, 6.5 mid, and a 1” silk dome tweeter. I am not sure, but everywhere I look them up it says they are rated down to 25HZ. They are ported in the rear so I keep them 2-3 feet off the rear wall. They sound amazing!
I’ll let you know what my the smaller advents sound like when I get them. Ebay score with 9.5 inch acoustic suspension woofer designed by the great Henry kloss....I hear they were renown for some marvelous bass. Stereophile did a throw back to the smaller advents and were blown away by the bass response of this relatively small speaker, although it measures a bit larger than today’s typical bookshelves being that its 20 inches high etc. It can supposedly get into the 30’s with relative ease....
Of course folks what we’re talking about here is what happens to a speaker in a room, or what Troels Gravesen calls "room gain." That is, the difference in a speaker’s response between the anechoic measurement, which is usually the -3 dB spec cited, and the completely room acoustic dependent response, which is what I measure in the blog post.

You can’t violate the laws of physics, and we aren’t. A speaker in a room sounds entirely different than it does in a measuring lab, and that’s where so many of our troubles come into play as we look for deeper, bigger bass.

The more of us see and know about it, the more audiophiles will get good buying advice, and more of them will be happier.

That’s the goal.
Assuming low distortion, a small driver can either go low or go loud.  Most small woofer systems have relatively high distortion as they go low and cannot achieve high SPLs.  In average sized rooms and for most listeners it's a reasonable compromise.
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What nigels SNR 1 really proves is how easy it is to be a speaker designer. All he has done is put a set of high end scanspeaks into a wooden box. Thats 50% of the job. I assume he didnt cut the wood himself either.

The crossover is simply a matter of taste. Although the graph of the SNR 1 shows an almost ruler flat curve which clearly betrays Eriks desire to boast about what he has achieved. The irony being that a flat response is not correct. So all that effort that has gone into achieving it, has been a waste.
It's also worth mentioning that all the bass response and crossover simulation is done on a computer. So there's no effort required by the so called designer. The software does it all for you. 
The 7-inch woofer in my Spendor D7s produces much lower (into the upper 20Hz range) and dynamic bass than the 12-inch driver and 15-inch passive radiator in my Klipsch Forte III (38Hz).  It's not even close.  The Spendors are tight, detailed, never fall apart at higher volume, and produce wonderful imaging.  The Forte IIIs are relaxed, sound like live music, and completely immerse you in the experience.  Both are music and both couldn't be more different.  Evaluating bass quality in a vacuum is like trying to describe art with only one color.
The room.

My friend has a pair of custom speakers, each a pair of 6" woofers. Upstairs, very large room, high ceilings, no side walls, carpeted floor, the imaging was terrific, but a bit bass shy.

He moved his system to a smaller room, lower ceiling, closer walls, and the bass is definitely stronger, the imaging not as great as the big room.

Before, large room, he was thinking of adding a single subwoofer, now not feeling the need. If only 1 sub, I think it would add mud. A pair of small directional subs, say 10", self powered, adjustable crossover and individual volume, could extend the bass keeping it directional.

Bring music with strong clear bass you are familiar with. Listen, hmmm, sounds right. You cannot tell how showroom demos will sound in your room, if possible get the dealer to loan you his demos, (already broken in) even for a short time, or allow return of new pair. You will know ’essentially’ how much bass reinforcement your room will give right away (if new, perhaps break-in period needed).

Imaging. Small 6" allows a narrow front width, allows better imaging. Adding a pair of small self powered subs takes the bass load away from both the speakers and the amp, thus the smaller mains can do a better job.
@three_easy... Actually, one Can 'do art' with 1 color...but that's a different discussion for another forum.  And really a network time waster that we shan't launch into Here....*G* ;)

@erik_squires ....Thank You. *S*  I've been concentrating my foray into a smaller Walsh DIY driver based on 6" drivers.  The properly sized (proportional) and shaped cone works out to the surface area of approx. a 9" dia. cone of 'conventional' design....and it works. *S*

Bass? Yes....Lower frequencies?  Not really....without opting to the current 'Ohm' configurations, MHO is I'm 'asking' a larger cone to be a 'one-trick pony' and do Everything.  Flawlessly.

Not likely.  And that's why I hand off those fq. to....Yes, a 6" sub. *G*

More accurate, controlled response.  It's the only thing that can 'keep pace' with my Heil AMT's.

I have noticed that if one desires 'room-filling' bass lines in a larger space, you'll likely opt for a larger sub driver.  You need to induce more 'air motion' into said space to create the same effect.  'Big' for 'big'....

It's all a 'work in progress', but I'm emboldened by the response of a listener when exposed to my Walsh 2-ways vs. a pair of small Maggie's...

"Which do you prefer?"

"Yours....sound more 'real'."

I Will carry on....;)
I work in a high end store, but do not care to pay the cost for anything we sell, even at half retail.  So I built speakers using components from Parts Express, including their pre-fab crossovers.  I used the 4 ohm Reference Series 7" aluminum cone woofer, and their 1 cu. ft. cabinet (since discontinued) with a vented alignment with an f3 of 39 Hz.  With room gain, I'm measuring into the mid-30s and it sounds it...very solid not muddy at all.  I settled on Morel's integrated "Twee-Mid" and made the system bi-ampable.  With zero engineering, but a lot of experience in audio, I came up with something I feel closely conveys the sound I hear at Boston Symphony Hall when I play live recordings of concerts I actually attended and heard performed live.  To me that's the gold standard.
I took my home-brew speakers in to the store and compared them to a variety of contenders...they held up rather well.  They did not perform up to my personal favorite, the Focal Sopra No.1, but they cost me one third of what those half price!
I write this to support the OP's claim that satisfying bass can be obtained with relatively small woofers.  But also to remind that a reasonable cabinet volume is monitors mine ain't...and that room size is a factor...mine is only 2000 cu. ft. (plus openings to other spaces).
With room gain, I'm measuring into the mid-30s and it sounds it...very solid not muddy at all.


That's what I'm talking about. Smaller speakers can integrate a lot better into a room, and leave you more satisfied with less effort.  The combination of better matching the room gain, plus not disturbing the dragons in the depths (room modes) is a big big win for a lot of consumers.

There are a lot of ways of getting great, deeper bass in a room, but they don't come easy and they don't come cheap.


BTW, anyone notice how damn smooth that bass response is??

Ty GIK acoustics and a semi-open room. :)
There seems to be some confusion in a couple of post of bass vs sub bass,  as Erik posted,   he is 100 percent accurate. 

Looking at specifically a 6 1/2. 
There is a problem on moving air for real impact in larger rooms.... Of course Erik qualified Apartment dwellers or some home theater use. 
To get a 6 1/2 to truly go down (and you can),  it requires some mass to get the fs down, which kills sensitivity,  it then requires some good excursion limits and decent size coil to get some power handling..... Its a real balancing act to create a 6 1/2 that does it all as far as just a sub bass perspective.  
Of course multiple drivers move more air,  several 6 1/2's could make a very good sub.... I used multiple 4 inch at one time just to make a point.... I had several 4 inch in series/parallel configuration that would get into the mid 20's.  
In general,  a good 6 will get you into the mid 30's and do a very good job for bass through midrange until your room just gets too big and needs more cone area to move more air. 
long term, ive never been happy with 6 inch woofers. even if the bass at first is quite decent. tit has nothing to do with extension either. real bass need to move air

no replacement for displacement.

As we all know, most of the bass we hear (tone, texture, definition) occurs between 50-200 hz...which is easily done by any decent 6" woofer in almost any size, I completely agree with Eric as he isn't saying that 6 inchers are the best sounding solution for every room and every situation...just that they may be better than you suspect.

I think we also have to remember that a 6" driver in a sealed box, vs a ported box vs a transmission line box is going to behave/sound different in each situation with the transmission line being the most likely to give the most toneful and powerful bass (but also the hardest to implement).

The bass we feel (and that which causes ear pressurization) can often be done by a 6" woofer...if the room is the correct size...even remembering that the loudness of the bass actually needs to be more than the mids/highs to create the proper sound balance.

The idea that there is no "replacement for displacement" probably holds true in bigger rooms...but even then, if you runs your mains at full range to get the great tone and if you have a sub, cross it below 40/50hz to get the feel and get the best of both worlds...and having low bass, surprisingly, enhances the sense of ambience which adds realism.

I owned a pair of the well regarded Silverline Audio Preludes for years and they had an extremely coherent full range sound from D'Appolito arrayed 3.75" titanium/magnesium woofers. It seems that the overall design relative to how the cabinet interacts to bolster the low end is what's important, and those things went down to the mid 40s clearly. I only replaced them for higher efficiency needs (small single ended tube amp). 
elliotbnewcombjr:"Before, large room, he was thinking of adding a single subwoofer, now not feeling the need. If only 1 sub, I think it would add mud. A pair of small directional subs, say 10", self powered, adjustable crossover and individual volume, could extend the bass keeping it directional."

Hello elliotbnewcombjr,

" A pair of small directional subs, say 10", self powered, adjustable crossover and individual volume, could extend the bass keeping it directional."
     What? Did you just invent a new 10" sub that defies the laws of physics? Do you think you just point them in the general direction of your ears and the bass soundwaves just travel like a beam of light directly to your ears? C’mon Man, bass below about 80 Hz is not even directional meaning we cannot localize it. The bass below about 80 Hz is actually the opposite of directional and is, in fact, omnidirectional which means the bass soundwaves radiate out from the sub driver in all directions at once. The bass spreads out from the driver in all directions at once forming a spherical pattern and does not travel solely in a straight line, directional path as the soundwaves above about 80 Hz do.
     There’s also some other pesky laws of physics to consider, such as the length of soundwaves increase as its frequency descends and decreases in length as its frequency ascends (soundwave length is inversely related to frequency). Also, our brains can’t even perceive a sound at all until a complete full cycle soundwave is detected in the room by our ears and multiple full cycle soundwaves need to be detected before a change in pitch is perceived.
     Based on the speed of sound of about 760 mph, this calculates to a 20 Hz deep bass tone full cycle soundwave being 56 feet long and a 20,000 Hz high treble tone full cycle soundwave being a fraction of an inch long. Given these facts, it’s not very hard to comprehend that the very long and omnidirectional bass soundwaves behave very differently in any given room than the much shorter midrange/treble soundwaves behave in any given room.
     All of the above almost guarantee that the highly omnidirectional bass full cycle soundwaves launched by a speaker’s bass driver into the room, some of them likely being even longer than any of the room’s dimensions, will bounce or reflect off of one or more room boundaries (floor, ceiling walls) prior to reaching and being detected by our ears and our brains processing it as a perception of a bass sound tone. This is true whether the soundwave is launched from a 5" or 15" driver.
     More to the point of this thread, however, it does seem logical to believe that a larger driver would be much more capable and efficient in reproducing the correct bass frequency soundwave amplitude (intensity level or volume level of the frequency) than a smaller driver would. IOW, reproducing deep bass notes requires moving a lot of air. Given identical excursion range distance (the distance a driver is able to move forward and backward like a piston.), a driver that has a larger diameter will move more air than a driver with a smaller diameter will. 
     The only way for a smaller driver to move more air, to equal the total volume of air moved by a larger diameter driver, is for its excursion range distance to be increased. However, the excursion range distance of drivers are not unlimited. There are factors that limit the maximum excursion range distance of a driver and this specific excursion range distance measurement, along with the specific driver diameter, also limit the maximum bass frequency depth the driver is capable of reproducing.

     A pair of good quality subs, properly positioned and configured, are capable of providing exceptionally good bass performance in any room and seamlessly integrate with any pair of main speakers at a single designated listening position. Utilizing two pairs of good quality subs will perform about twice as well as a single pair, with near sota bass performance along with providing this bass improvement throughout your entire room and not just at a single designated listening position.

Word to your mother,
You are talking about many different things in this post: smallish apartment rooms, added subwoofers, and room treatments.
Sure, smallish rooms can better support smallish speakers.
Room treatment in every room can have a dramatic effect on SQ.
Subwoofers can increase SQ of big and small loudspeakers. A sealed speaker system in a larger room will never produce low end energy by itself.

There are many speakers systems with smaller woofers but the better 1’s use multiple smaller drivers instead of 1. Also, the reason why these systems can produce low frequencies is due to the port setup, which can increase lower bass frequencies. I used to have the Usher mini dancer 2’s with multiple 7” drivers and they would produce low levels of bass energy for its size, but not the cleanest bass output. I tuned the port with acoustic fill and added 2 Rel subs. This was in a treated dedicated 27x16x15’ foot. I sold them and went with the larger Ushers with the 11” woofer, much better tighter lower end and no need for subs.

...the interesting thing about line arrays is when all those small speakers combine for bass lines.  If one doesn't get too enthusiastic with the drive levels, they respond quite nicely...

I remember my 901's of eons past....not all that accurate, but plenty of it...;)
Thank you all for participating so actively, especially those who can share personal, specific experiences and who read the nuance in my original post.

I was thinking of something that I think has helped this discussion: I used a DIY speaker as my example, otherwise many would accuse me of shilling for a particular brand. At the same time, I don't mean to imply only this speaker can output this much bass in a modest listening space, I'm sure many others can as well.

 I used a DIY speaker as my example, otherwise many would accuse me of shilling for a particular brand
you used your own DIY designs. And all the effort youve spent making that response curve as flat as a pancake has been a waste because that was the wrong curve. You will need it completely retuned now. We need to examine the off axis curve too.
I think I read somewhere (KEF I believe) that the natural resonant frequency of a 15” woofer is lower so therefore it generates lower frequency bass with more ease? Is there truth to the notion that a smaller bass driver (6.5” - 10” etc.) will be quicker sounding / more resolving than 15” drivers? I’ve heard many biG horn / compression driver JBLs with 15”woofers that sound very fast and agile in the bass. I had a pair of KEF Maidstone R109 that had huge 15” drivers that sounds very agile and ‘big’ too.
Hi @adameos
Is there truth to the notion that a smaller bass driver (6.5” - 10” etc.) will be quicker sounding / more resolving than 15” drivers?

No, but that’s what we are touching on here. Less bass = low risk.

I’ve heard many biG horn / compression driver JBLs with 15”woofers that sound very fast and agile in the bass.

There is simply no substitute for surface are when it comes to deep bass and high output levels, especially in a test chamber or outdoors with no reflection points.

The trouble really is the room. Small rooms, untreated are much friendlier to smaller speakers with limited bass output. And that’s the blog post. :)