size of the driver

1) size of the driver is related to efficiency in producing deepest bass. But bigger drivers become problematic in transient response. Sub woofer manufacturers like REL and Velodyne make money selling a well tuned optimized home use choice to supplement less than full range speakers for the lowest bass
2) the ear is most sensitive to high frequencies. When you reduce volume below the original performance db levels the lower the frequency, the more you will feel something is missing (fullness). Inexpensive gear oft had an equalizer feature (loudness) to compensate and avoid ill will from neighbors. Audiophiles don't compromise/take it for granted music is to be played at original volume.

Avs9 writes:
>But nowdays I am seing 6 inch drivers stated as "bass". Just curious how well those perform

They provide enough mid-bass output to meet a woofer for serious listening or a sub-woofer at polite but not realistic levels suitable for hold and elevator music.

>or in another words what is the secret behind those if they really can perform at the same level as the 12 inch ones?

They don't.

Output at the maximum linear excursion into full space for various representative drivers at 3 feet is as follows at 120, 80, 40, and 20Hz. Many drivers have less excursion and lower output. Subtract 3-5dB for living room dimensions and more for a larger space for the SPL at your listening position

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer.

Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB
12" Peerless 830500 483 x 12.5 121dB 114dB 102dB 90dB

As a frame of reference I like my jazz at less than live 85dBC average levels which makes for peaks on good recordings with 20dB of dynamic range of 105-107dB at the speakers. The scale is logarithmic, so at 80Hz that's more than 10X what you can squeeze out of a 6" driver and 100X at 40Hz.

>And another question which I guess is too simple and too basic around here that's why I couldn't find some point to point answer - when we speak about sensitivity - would that be a true statement to say that higher level (say 92-95 db) will allow to extract "fuller" sound spectr at a lower level of volume?

Not with equal frequency response although design considerations mean you might get a boost in higher frequency bass output so it sounds that way.

Efficiency is at best inversely proportional to the cube of the low frequency cut-off and proportional to the size of the enclosure. To make a speaker play one octave lower using the same bass alignment (sealed, ported, band-pass) it needs to be 8X as big to maintain the same efficiency; or conversely at a given box size a speaker with one octave less bass extension can be 9dB more efficient (or 3dB for 1/3 octave).

When people build speakers with limited bass extension they often boost the output before the roll-off starts so there's the illusion of low bass and since higher frequencies have a lower threshold of hearing you can notice the extra bass at listening levels where you couldn't hear the real thing since our threshold of hearing and equal loudness curves require higher SPLs at lower frequencies.

Small and efficient speakers can't have low bass but are often built this way although that doesn't mean all efficient speakers are.

04-27-12
Responses
04-28-12: Jmcgrogan2
Smaller bass drivers have gained in popularity for two reasons.
>B) they may not go quite as deep, but the bass will be tighter.

Apart from physical limitations on the displacement needed to achieve a given SPL driver size has no bearing on bass quality.

>04-28-12: Sounds_real_audio
Boy you are old. Listening to music in the 70s. Smaller drivers are trendy because they go fast.

Driver size has nothing to do with "fast" or "slow". Twice the motor strength will accelerate double the mass as a smaller motor/mass combination whether we're talking about vehicles or drivers.

Smaller drivers are trendy because they're less expensive (which allows for bigger profits) and not as offensive to women who are more likely to contribute to the family pot and have a say in how it's spent than in the 1970s and before.

People retiring their tube gear in favor of transistors have also made smaller and necessarily less efficient enclosures practical. With 80 transistor Watts you can drive an enclosure with the same low frequency cut-off to the same SPL you could a speaker 8X the size with just 10 tube Watts.

>Bigger drivers can still have that old school sound. Bigger drivers move more air but tend not to be as accurate and have trouble keeping up with a 5" midrange so you can loose cohesiveness.

Nope.

04-28-12: Ngjockey
>Although bass extension is generally less with smaller drivers, some of the dynamics can be equivalent or even superior with multiple drivers.

Right. Looking at the table I provided you'll note that with 10 6" drivers you can match the headroom for dynamic peaks you get with a single 12" driver. Where you only get 2-4 6" drivers the smaller drivers can fall short.

It turns out the large woofers of the '60s and '70s were counterproductive to bass extension, driver blending, and the distortion of cone breakup.

Smaller drivers solve many problems in dispersion and driver integration. A 12" woofer starts beaming (i.e., no dispersion to speak of) at 1100 Hz. A 6.5" driver doesn't beam until about 2100 Hz, making it much easier to blend with a tweeter. A 6.5" driver will also accelerate and stop faster than a 12' one, and it's easier to make a 6.5" speaker that won't have significant cone breakup at full excursion than a 12" one.

Great strides have been made in cone excursion. A 6.5" driver with 1/2" excursion can displace more air than a 12" driver with 1/8" excursion (typical of a '70s woofer). Twin 5.25" woofers with 1/2" excursion have 50% more potential displacement than a 12" with 1/8" excursion.

Then, as was mentioned before, you get better dispersion and therefore better in-room power response with a narrow baffle than a wide one. So all in all, smaller woofers make for better overall speaker systems--better imaging, better dispersion, faster response, higher crossover points without suckouts. The Atlantic Technology AT-1 manages to get <30Hz bass extension from an MTM arrangement with two 5-1/4" woofers and unique cabinet loading.

Thanks, folks. Once again I came to realize to helpful the audiogon can be. A lot of information to think over, "sounds" similar to my thoughts very often. Yes, I am not 15 any more, for the last 40 years. I remember back then in Russia the speakers from Estonia were popular, I can't recall the sound of course, been a long time, but I was really impressed. Then routes of life displaced all, was able to start getting "back in shape" a year ago and guess what - from all out there I bought Audes 027 made in Estonia :-)
Best Regards to all

If you are interested in dynamic speaker drivers and technology, read up on Walsh drivers for something completely different, as they used to say.