6.5 vs 8 vs 10 woofer


IMHO I think the 8 is the ideal size cone for mid/small sized listening rooms. Even for large size listening rooms. 
The lower mid hz's seem cleaner/clearer. And  there is so little fq's in 905+ of the music we listen to, it seems to me the 8  driver is the most perfect size cone.
A 10 size cone  has the potential to become overwheling, aggressive, attacking when amp gain is pushed just a  tad too much, = Better  volume  control with a  8 vs a 10. 
The 6.5 misses some of that lower bass which a  8 can voice superior. 
After listening to several YT vids with a  10 FR, I had considered going 10, but i think  staying with a  8 avoids regrets. 
I listen at low/mid volume. 

mozartfan
Why then are most all subs 10” and 12” or bigger?
hard to isolate

depends on implementation with many many other factors
I fundamentally disagree with the notion that there is only one approach to any aspect of speaker design.  That someone purports to have determined what diameter is ideal for a full range driver, regardless of other aspects of speaker design, such as type of enclosure and type of bass alignment (bass reflex, open baffle, sealed box, quarter wave back-loaded horn, transmission line, etc), the type of tweeter to be used with that woofer, and a whole host of other factors, speaks to the lack of experience and understanding of the OP.  That this conclusion was arrived at by watching You Tube videos, adds to the folly of this assertion.

I've heard many different full/wide range drivers used full range, or with a tweeter or with a woofer or in three way systems, and there was not one single characteristic that was common to what I considered successful implementation.  Size did not necessarily matter, type of magnet structure did not matter, cone material, you name it, did not universally determine what was best.  Yes, I heard terrific 8" full range drivers, such as the AER BD 2, used in several different systems and the sound was completely different because other aspects of design were different.  The best application I heard of this driver was in a single driver, quarter wave backloaded horn system by Charney Audio (utterly amazing); another system where that driver was used in an open baffle system with a subwoofer was not as successful to me.  The very best system I heard with a wide range driver had a 13" field coil driver in an open baffle (the 13" driver operating full range (no low pass filter cutting off its upper frequency response) with a tweeter crossed in way up high in frequency. 

There are more ways to make a speaker system than there are ways to make lasagna--don't tell me that there is only one correct recipe, even if it happens to be the one I like.
Not this crap again! 
I showed how this guy made sweeping declarations about full range drivers, and that he was fundamentally ignorant of the fact that the brand he was boosting, Voxtiv, makes a sub with a crossover. OOOOOPS! 

Now, he is starting with stupidity of 8" is the ideal woofer. 

"Listening to several YT (YouTube) vids..." What a joke! Remember, this guy is in about a 10x12 room, so his big discoveries are entirely limited by his room. He is one of the most biased persons claiming to be informed on this site. 

"Better volume control with a 8 vs a 10." This is just fundamentally ignorant. 

Who need this garbage?  :( 


I don't know about that OP.  I run

6 12" OB servo subs in 3 columns (GRs)
12 8" MB PP drivers in 4 SAT columns or 2 72" NB columns (Mine)
12 8" planars in 2 74" 420 lb HDF NB Di or Bipole columns (switch flip)
2 AC G1s Tweeters ribbons 6" ribbon
4 AC G2si Tweeters ribbons 2" ribbon (VMPS RMx Elixir cabinets)

36 active drivers

OB = Open Baffle
NB = Narrow Baffle
PP = Phase Plugs
HDF = High Density Fiber
SAT = Stack and Test speaker system

I don't care WHO say it.. More is better when it comes to drivers...

Fully active direct coupled MB columns (8") with full blown DSP, and an active OXO

These 8" drivers work from 60hz to 300hz.. I use 12K Behringers and a 2496. Absolute control. Very good dampening that actually WORKS..
Dampening CAN'T work unless they are direct coupled. NO OX between the driver and the amp. Most folks don't know that...

Getting them ALL to work correctly together, that's a whole different story with this 13 year old project. I'm close.. This year maybe.. :-)

SO 8" X a lot works for me. :-)

Regards
One thing I have learned after all these decades is there are no rules on what designs are the best because there are GREAT designs of every possible description. 
oldhvymec,

You need to take a video with your cell phone so we can validate your approach.  
I think we have a new Kenjit. Very few people can fill those shoes, but we seem to have a winner!
Clearly the OP doesn't list his room size and mention 8" woofer is sufficient for large sized rooms come on. Doug Schroeder hits the nail on the head. 
Just left Richard's shop, we looked at some charts of the 8's  vs  10's , which i am considering. 
10's is the better choice.
I asked Richard about some of the low hz's in the cello section, , seems the 8's range would miss out  in the lower range fq's. 

Having owned the 6.5 MTM, for now going 20 years, I'll finally get to hear some of the lower bass I've been missing out in my  full orchestra recordings. . 
Now let me ck out a few of the above comments. 

, Voxtiv, makes a sub with a crossover. OOOOOP


~~~~~~~~~~~~~~~
I've lost interest in the Voxativ
1st off , good luck attempting to get in touch with any USA  distributor.
2ndly
I'm more interested in a  10, for the lower fq range. This will be my very 1st 10 inch in my system, I'm excited. 
The   10, I will not require a  sub.
 Another local tech strognly suggested to avoid all subs. I agree.

These 8" drivers work from 60hz to 300hz.

~~~~~~~~~~~~~~
Well yeah, if you can confirm that 60hz for the 8 as real.
manufacturers tech's sometimes are a  bit ~stretched~.
From the chart on the web site, Richard sees the 10 going ~ 40's~~
Which I am not so sure there are 8's which can go into the 40's, in ~ accurate testing~~ apart from what the lab states on the specs. 

I don't care WHO say it.. More is better when it comes to drivers...

~~~ My 2 local techs, emply stacked speakers, = More is better at least for their requirements. 
I am not interested in ~~more~~ my listening rm is 10x12, a  single 10 will be more  than  enough spl.
I'm not interested in ~~concert sound stage~~.
I'm trying to acheive the most accurate fidelity at low/mid volume. 
FR meets this requirement.
xovers are a  dismal failure
+1 to what everyone else said...

this guy doesn’t strike me as another kenjit but I have been mia for a little bit.

I was thinking that drivrr material, weight, power of the magnet, voicecoil size, cooling, basket material etc. all play a larger role than size, no pun intended.

At the end of the day though, theres no replacement for displacement... technology you say?  Apply that same tech to larger and its better
oldhvymec,

You need to take a video with your cell phone so we can validate your approach.

<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>

I’m bad about pics but you can see some primed MB and Servo units on my page here.

As far as validate anything.. None needed I really don’t look for validation from anyone. One of the best systems I’ve ever built though.. I did have a Strathearn System, that might have been better.. 500 lb bass bins.. TONNAGE comes to mind...Bigger rooms back then too...

I’ve built, NOT bought, quite a few... Though the VMPS RMx Elixirs aren’t my idea, the Dipole option and Tweeter relocation are.. The rear section to the monitors are and have been in primer sense the stupid heart attack thing.. SLOWED me down.. LOL all 16 of them.. Hands twisting up in knots after 15 minutes.. PITA...

OP don’t get all upset.. If I would have know you were in a smaller room I would suggest NOT stacking my SATs Just one on top of the OB servos from GR or no GR at all. My columns are good from 26-700hz. If I want..
Accurate, LOL almost ZERO overshoot..... Reproduction has never been better, but mighty close..

I like the Columns and RM30 monitor too. (no bass section) Accurate and FAST come to mind with less that 10% distortion in the bass region...Can't get that from a larger cone speaker... 8" is the right size for me.

BUT I use a 10" that reaches 18 hz in a small box... about 5 or 6 years sense that discovery.. 145. per driver..
8 in a room, look out.. They use to make the curtains move in and out of the cracked windows.. A few nails came loose in that room KIDS.... :-) 20X16x8

Like I said maybe this year.. PICS too.. More is better...

Regards
I was able to get the7” scan speak revelator that Fritz uses in the Carreras to play -3db at 24hz and 0db from 28 hz to 120hz in a 12x14 room.  
I used Sonarworks reference 4 and the supplied calibrated mic to get those measurements.

I’m guessing though that I’ve gotten Rels to play down to 20Hz, possibly lower, at 0db.  I’ve felt Rel play lower than I can hear

Mercy Doug.. I just read your post... Not like the calm collected fellow you normally are.. OP ticked you off a bit did he?

Deep breaths... LOL

Regards
Four 8" woofers of good quality will always outperform a single 15" in terms of speed and resolution while providing about 15% more cone radiating area to move air.

This is a general statement, not withstanding the quality/performance of each driver.
Four 8" woofers of good quality will always outperform a single 15" in terms of speed and resolution while providing about 15% more cone radiating area to move air.

This is a general statement, not withstanding the quality/performance of each driver.

~~~~~~~~~~~~
Well yes dual 6.5's do havea  certain ~~Punch~~ in the bass whicha  single 8 evena  10 might not mtach.

had the Thors been , if we can fantise a  bit, over 91db sens,  they would have made my perfect ideal speaker, But 87db, is ridiculously UN-sensitive.
So I have to give up deal 6.5's with Neodymium magnets. 
A single 8 might be a bit limp in the bass vs dual 6.5's. 
Perhaps not, if we throw in 95 db sensitivity on the single 8, might easily match dual 6.5's 87db.
10 inch with high sensitivity will bring my system all the bass i've been missing all these decades. 
I'm expecting good things from the 10 in my full ~~cellos, double bass, timpini ~percussion~~orchestral  recordings. 
Building the cabinet now, for the 10, but will  use the 8 til i order the 10. 
Just going to stuff a  bunch of fill in bottom section for the 8's parimeters.

double 6" or 7", per side.

Fast, clean. mates up better with a tweeter.

MTM arrangement (midbass-tweeter-midbass)
with the right crossover, pointed straight out, you at the tip of the triangle between them. if done right, the levels will be fine. Then a window of toe in is available, of maybe 15 degrees. quasi 18 on the tweeter, quasi 12 on the woofers.

Tweeter must be a monster. King of the hill in bottom range, power handling, and efficiency. The Holy Trifecta of Tweeters. MDT33 or the ET338, is a good choice. Crossover in the 2.2k range. Some ribbons might work. Probably don't have the efficiency, though. You generally want a good 91db for one watt on the tweeter, preferably 92-93db efficiency. You'll be doing phase and crossover tuning and that will eat efficiency up, so you need to start with overhead.

be at least 9 feet away, for the pair of woofers to integrate better, and be more like a point source, than a line source.

But then again, anything can be tweaked.
oldhvymec, every so often I unload with both barrels. Usually only one. :) 

Actually, I have been working on improving my cardio. Lots of steps on the step mill, which is painfully tough if you push yourself, and purposeful deep breaths and exhalations to improve lung function. It's quite nice to be able to breath deeply without strain.  :) 


Who cares.... you should always run a minimum of one sub preferably 2  (with about any speaker setup).....really dumb post!
So I'm no bass junkie and an 8" driver seems right for my small room. But I've heard some pretty amazing 12' and 15" drivers too that I would love to have if I had the room. So as has been said on this thread repeatedly there is no one right way. Great post @
"I use 12K Behringers and a 2496."

Explains a lot.  Leaving it at that. 
They probably are with new woofers but with a vintage woofer you can use as large as you want because of the high impedance drivers. The high impedance and large coils and strong magnets allows them to control themselves and not need an amp to control them.
@b_limo 

Sounds like you're voting for quality of speaker over size. I agree - just got my own Revelator sub working (9") in the HT. Now for that Bryston 4B ...
OP you got their attention today!
I believe @larryi pretty much nailed it.
I fundamentally disagree with the notion that there is only one approach to any aspect of speaker design.......There are more ways to make a speaker system than there are ways to make lasagna--don't tell me that there is only one correct recipe, even if it happens to be the one I like.
So many different factors affecting quality of bass, not the least of which is acoustic suspension vs. bass reflex design, but also number of drivers, voice coil, magnet, cone material, surround, the box (size, shape, materials), impedance, crossover frequencies, sub(s) or not, and on and on.
Revelator sub working (9")

~~~~~~~~~~~
Scanspeak  makes some beast like woofers, Monstas, Rip roaring bass drivers,,
But its not my cup of tea.
So to answer my OP q' a  8 is superior to a  6.5, <<obviously>> Buta  10 which has properly behaving, polite lower mids, is the ideal, if not most perfect driver for bass/upper bass.


So i will be going from dual 6.5's witha  mere ~disgustingly low~~ db sens of 87,,to a  single 10 with , ~~get this~~ 98db sens.. 
IMHO any driver below say 94db, is , at least to my ears, worthless old out dated technology.
hate to repeat this 1m x's, but I'll say it one very last time, db sensitivity is 100% the most important tech value you ned to look at 1st in any speaker's performance.
All those wonderful things Seas says aboutn their Excel speakers, MIGHT BE true, so long as there is no high sens wide band in the room.
When i get the high sens 10 in, the Seas Thors will not sound like Wet Blanket speakers, more like speakers covered in tar, Just ugly, real ugly.
Even the Diatone was blown away bya  94db sens, Each 1 db you go up the ladder, smashes the one below, 
db sens is everything  concerning speaker voicing. 
Scan and seas does have a  few high sens, but nothing that will compete with the new high sens drivers.
Those 2 labs are stuck in the 1970's technology. 
Thanks for sharing. Based on your informative post, I just put my two Rythmik F25s with their ridiculous dual 15-inch drivers out by the curb with a "free" sign on them. 
efficiency, though. You generally want a good 91db for one watt on the tweeter, preferably 92-93db efficiency.

~~~~~~~~~~~~
There are tons of choices of new compression horns which are 108-115 db efficiency. Why settle for a   dismal, poor efficient  93db, ??
Always seek high efficiency. Higher the db sens the superior the voicing of fq's This is a general rule , but more often true than not. 
In fact  now that i made the high sens discovery, its  my Golden Rule.
Thors 87db  lol 
You should go see what Seas says about their Excel drivers, In my book, none of which is true.  


I like many different kinds of woofer setups in speakers: multiple smaller drivers in the Revel Salon/Studio II and the Raidho’s, multiple larger drivers like in the Wilson’s, and right now using the 11” single Eaton driver in my Usher floorstanding speakers
 Rythmik F25s

~~~~~
170 lbs of monsta bass,
I mean to ask, do you have neighbors, close by? Guess not, and your pets? Guess not. 
10 inch bass will provide MORE than enough bass in any size room. 
dual 15's ,  This is the bass The Who uses at rock concerts. 
"hate to repeat this 1m x's, but I'll say it one very last time, db sensitivity is 100% the most important tech value you ned to look at 1st in any speaker's performance."

While I agree with this sentiment 100%, there is always the exception to the rule.

15 years ago, I was in a band, and we were getting ready to do our first headlining show.  It was a small club, and we had to supply our own PA.  I advocated for us to spend fifty bucks (we were getting paid $400 for the show, so this was not a big deal) to rent a couple of mains, since one of our supporting bands had already agreed to bring a pair of their monitors for the gig.  

Our singer was stubborn, though, and was combing Ebay as hard as possible to find a different path.  One of the things I told him was that efficiency was a VERY big deal with loudspeakers, because the lower the efficiency, the more power we needed to drive them, and I didn't have unlimited amplification capabilities.  

Lo and behold, he finds a pair of mains ($100 for the pair plus $100 shipping) claiming 500w power handling and 98dB efficiency.  I told him it sounded fishy, because there would be a ceiling on max dB output, but he went ahead with the purchase.

The voice coils caught fire less than half an hour into the first band's set.  LITERALLY CAUGHT FIRE.  All we were running through them was vocals, so there's no explanation for this other than they were just cheap, shitty speakers, no matter what stats they claimed.  
Well, I combine those with a pair of SVS SB-13 Ultras to make sure there's just enough bass.

They all come with volume controls. They don't have to be turned up to 11.
Wow!  I'm Not Sure..  Crazy!  the time we all have that is Free Time, on this..  is All..
I remember way back when...before the popularity of (invention of home) subwoofers... 8" was considered the 'proper' woofer size in many a sealed box 2 way system. 
I also agree no one size fits all!
My more 'conventional' speakers are 6.5s' with a passive for speed, to keep pace with Heil amt's.  Below that, a pair of 10" backed by a small sub for impact on demand.

The Walsh only need the sub for 'bottom'. *s*  Same for the Maggies.

Between the 3, I can adjust for the media du jour. ;)

The only 'one size fits all'....is a hanky.
Mozartfan is a very suitable handle.
His dogmatic unevidenced statements seem to be formed from the scientific knowledge available in the eighteenth century.
The voice coils caught fire less than half an hour into the first band's set. LITERALLY CAUGHT FIRE.  

~~~~~~~~~~~~~~
Richard Gray did advise , that I am going in the very opposite direction as his Atmosphere 2.8watt SWET with 83db eff speakers, 
While the Atmos owner burnt up his SET amp, <<like 3x's>>?? according to Richard's testimony, That I would witha  100 pure watt PP amplifier <<Litterally Fry the 98 db speakers>>
This morning as i awaoke, i realized, just at what vol level on the linestage jadis can I turn before i have << high db level>> 
Might have to get that Italian step attenuator for $300 have Ricahrd install, 
OR sell off the Defy7 and make a offer on Richard;s 250 tube SET amplifier he  designed, its all attached to a  piece of plywood, , but thats neither here nor there, Its how does it sound.
After I get the 8's up N running I will test the 2 amps. 

I mean even with the 6.5 Diatone, the vol knob hardly ever goes past 9 oclock, if that. 
94db, then 98 db, now i am beginning to understand all this SET vs PP paired with super high FR speakers.
Got it. 

While I agree with this sentiment 100%, there is always the exception to the rule.


~~~~~~~~~~~~~~~~~~~~
Yes my above post.
I am already looking fora  845 used SET amp on Ebay now. 
Its possible the Defy may have to go.
Seems after all these years, it was high snsitivity speakers that i was after all this time,. However the caveat here is, will a SET perform complex full orchestra w/o getting all ~discombobulated~, Flustered~ breakdown~.
If yes, Defy stays.
Will order Richard's recommended Italian 47 step attenuator. 
Just can't use hardly any of the power of the Defy. 
Will have to ck the magnet temp now and then, so its not over heating.
My 10" tannoy dual concentric driver sounds good to me with none of the negatives you profess. 
My 10" tannoy dual concentric driver sounds good to me with none of the negatives you profess.
I own 2 pairs of them 12 inches with no negative to my ears for 40 years....

Alas! sold....

Too big for my desk....
Nonsense.  It depends on several factors bu is certainly not as simple as you suggest (or often even in that direction!):
1. rollover frequency - lower means less coloration due to cone distortion2. Area - Pi*R^2 = more is better to move air; more area also means less excursion required = less distortion of some types3. flip side, more are means more flex --> mitigated if not being used as a midrange - back to roll off frequency
A badly designed speaker is just that.  For smaller two-ways the trad-offs are major and you will have issues in the midrange if large, no bass if small.
With a properly designed, hgih quality drivers, well-amped 3 or 4 way speaker, bigger is, within reason, better.  Bu that is all things equal, which they rarely are.
G
If you want bass, use a 24" Hartley in an appropriately designed box.  Last one we built for Mark Levinson's HQD system was about 5' tall, 2' deep, and 3' wide made from 1.25" press board.  It was on 4" casters as it weighed a few pounds, but if you power a pair of them right, you will get some bass in your room that your friends and neighbors will not have.

Cheers!
Like just about any audio equipment assessment, the answer to what makes a perfect woofer diameter is: "it depends".
Why the ad hominem attacks on the OP? He's stating an opinion and adding in his personal experiences to support thoughts on the matter. If you wish to refute it, fine but I don't believe there's any reason for name calling. The churlish remarks don't paint one in the finest of ways. And for the record I don't know the OP though I've seen previous posts.
Also, in this case I happen to disagree with him only based on personal experience with a 10" sub. I do agree with several responders that the individual implementation, source material and personal preference would practically dictate which is "best". For my office system the OP recommended 8" woofer suffices nicely whereas the 10" of my full system would be overkill.

In any case, I suggest a bit more civility ladies and gentlemen. There's simply not enough of it in the world IMHO.
Happy listening.
Very odd that high sensitivity speakers never really took off in popularity. In my limited experience , wide band high sens is the only speakers that exist. 
xover things are deleted permanently in my book.
WEll perhaps the SET amplifiers may have beena  road block, as most are very heafty and very expensive back through the years. 
And no doubt this was the issue.
Now SET's can be found relatively low price + new developments in high sens, wide band, seems to me the future will go that direction. 
So far the 91 sens Diatone plays quite nicely witha  PP 100 watt. 
Next test will be the 94 sensitivuty wide band. 
has anyone here paired a  high sens speaker with a  100 watt PP amplifier?
Did the magnet heat up?
Was there issues with vol control on preamp? 
That is at 9 oclock vol, was there too much gain  for the driver?
In any case, I suggest a bit more civility ladies and gentlemen. There's simply not enough of it in the world IMHO.


~~~~~~~~~~~~~~~~
Appreciate the back support
But this is Audiogon, a  few snides here and there, is all part of the discussion. 
Just so long as  the  mud slinging does not get out of hand to fist swinging.
This new high sensitivuty speaker is all brand new to me. 
I was studiously looking over FR back a  year ago,  but until one has the actual experience of hooking 1 up to the amplifier in real time, then the whole thing becomes clearly apparent. 
I havea  feeling the Defy will have to go adios. And look for a  SET, perferably mono blocks. 
I'm done lifting amplifiers over say 50 lbs. 
The Defy is at 70+ lbs. 
Mozartfan,

Most of the speakers up to the early 1960's were high efficiency speakers.  In those days the speaker were quite large in size.  But, when stereo came along and television sets were also populating living rooms, it became important that speakers become much smaller in size.  The "air suspension" (sealed box) speaker came along to solve that problem.  These speakers were inefficient, but, solid state electronics came along that offered higher power in practical packaging.  

There has been a small revival in higher efficiency speakers and lower-powered amps, but, it remains a boutique community because the rest of the world places higher priority on small size (you can just plop the speaker on any table), portability, etc. and sound quality hardly matters that much.
Completely ignoring the enclosure type and room parameters makes this argument a fallacy. Just sayin.