Do you think you need a subwoofer?

Dear Velocityyofhue: As I posted and from my point of view and experiences the main target to add subs to your audio system ( almost any system ) is not to go deep in the bass or higher bass quantity but to improve the quality performance of your Thiels ( and achieve a lot whole better system performance. ) lowering its high IMD/THD ( intermodulation distortion/total harmonic distortion. ), this target when you achieve it makes a difference like night and day, period.

Now, your Thiel's are a very good example on the subs subject because the Thiel woofer handle a wide ( more than five octaves ) frequency range: 28-30Hz to 1Khz ( due to its first order slope crossover. ).
That woofer needs to reproduce at the same time a 40Hz frequency and a 500Hz one ( example, the reality is more complicated due that the woofer has to handle all the frequencies in its very wide range. ) where the needs to the 40Hz frequency reproduction stress ( IMD ) heavy the 500Hz frequency reproduction where this one loose its un-distorted/clean reproduction that we heard like a smeared non-transparent no precise definition, etc, etc.
I know that you like what you are hearing, well you can't imagine how good is your system till you make that the IMD in your speakers goes really lower and one of the alternatives is through the integration in true stereo fashion of two self powered subs blended seamless.

When you achieve this the Thiel's woofer will work between around 80 Hz and up lowering the IMD that clean-up all the frequency spectrum response, now that woofer will work with out the " stress " ( excursion, overhang and the like that affect seriously the whole woofer quality performance: a heavy compromise. ) in favor of overall speaker quality performance.
At the same time the whole bass response will improve its quality performance because right now that bass frequency range is handle for a dedicated ( was expressely designed for ) speaker ( the subs. ) and for a dedicated amplifiers that was expressely designed to match exactly the needs of that subs drivers.
Here you will have and wll hear the quality on the bass that you never heard in any full range speakers ( non powered ) at any price.
You not only improve the quality of the bass response but obviously you improve to in the bass quantity and in a lower/deep bass response that you will hear only when the recording demand it.

Everything change for the better: power handling because your Krell will be working in a less wider frequency range: its overall performance improve, sounstage will be a lot better too, there are so many improvements that is almost impossible to name it.
Other thing: right now the position of your speakers is a compromise between the in room bass response and the mid/high response, there is a trade-off.
When the " deep " bass liberate the Thiels then you can move it/change a little its room position to achieve a better in room mid/high frequency range response/perception and the subs will be locate too at its best in room position: best of two " worlds "!

IMHO it is worth to try it, the change is of paramount importance with several and true rewards.

It is almost useful/vain to argument against the subs with out listen/try the whole alternative.

Of course that some speaker manufacturers and/or audio dealers/reviewers can't support the subs " road " because the alternative goes against business ( $$$$ ) where the money is on sales of bigger ( more costly ) ( next model in a speaker line. ) or different speakers ( more expensive )than in two inexpensive subs that we even can buy second hand.
But even IMHO if we are wealthy enough the fact is that we can't achieve better quality performance ( everything the same or that the main speakers were decent speakers. ) with the new " big " speakers " than with the un-expensive subs alternative.

Regards and enjoy the music.
Raul.

Big speakers need love to Raul.
Look at Oneobgyn. He's got he big Wilson's and the big JL Gothams. I bet there is unbelievable ease to his system.
Gregadd

Dear gregadd: That system is a " impressive " cost no object alternative.

However, those Gothan's are used as a bass re-inforce " tool " where the Alexandria's works full range.

Here, the owner's system choose ( IMHO with all respect I take this system example like that an example only and not like a critic on it and not telling that my " voice " is the only and right one. ) not taking advantage on the subs whole subject ( well he is taking advantage on the bass re-inforce but with many trade-offs, one of them is that the main speakers are playing in the low bass at the same time than the subs. ).

I f I was " there " ( unfortunately I did not, a healthy " envy ". ) my choice will be for the Velodyne's DD-15/18 or the DD-1812, both have a high-pass filter that we need to liberate the Alexandria for the low bass range.

The Velodyne choice not only give me that HPF but better specs on bass frequency range and its HD is the lowest on commercial home subs: less than 0.5%, this is very important because we want a clean in room response down there and according with the HD " quality " of the main speakers.

Other advantage to separate the low bass on the Alexandria's is that those Lamm's amplifiers will perform better with out " see " that bass range.

The Alexandria's are " easy " to handle almost for any amplifier SS/tube due to its very high efficiency ( 95db. ), Wilson say that you can start with amplifiers that put at least 7 watts but IMHO and due to its low impedance ( 3 ohms. ) and complex electrical impedance curve this speaker is not an " easy " one and its needs ( like the music needs specially on transients. ) are demanding to a matched amplifier ( not almost any. ) to show its best and great quality performance.

The sub's integration in true stereo fashion IMHO can help to improve the quality performance of the Alexandria/Lamm combo.
Of course that I can be wrong but this is what I think about and what I do with that system.

Gregadd, the audio/music home sound reproduction is a very complex one if we want to achieve a near " perfect " quality performance. The audio chain has many links and the relationship between those links are almost infinite.

IMHO each of those links has its own learning curve where we have to understand the differents steps in that learning curve to take its advantages and try to eliminate its dis-advantages. This link/chain " learning curve " know-how is one of the keys to our " audio dream " sound reproduction.

The sub's subject is one of those links where many of us are at the begin/start of the sub's learning curve, we need to grow-up ( like in other audio link's learning curves. ) learning with true experiences about, it is very difficult to learn if we don't " live "/feel with experiences on the subject.

IMHO as we grow-up on each audio link " learning curve " as better ( not only different but better. ) quality performance will show our home audio system.

Regards and enjoy the music.
Raul.

As usual Raul you are not without an good opinion. Dragging us kicking and screaming to better sound.

My point was just because you have a big expensive full range speaker does not mean you don't need subs.
As for what the crossover point should be and whether Jl or Velodyne is the proper sub I'll leave that fight between you and the Doc. I'm in enough controversy.
Gregadd

The sub's alternative IMHO is a tremendous " tool " to improve almost any home audio system quality performance that use tube amplifiers.

Due to tube technology characteristics and the fact that in a sub's system the amplifier does not " see " bass frequency range this improve the tube amplifier overall " power " in the remaining frequency range ( main speakers ) and permit that this un-stressed tube amplifier performs and match better to the main speakers.
The quality improvement is really significant and IMHO this " road " is a must to go specially when we are using tube amplifiers, I can't imagine a better system up-grade everything the same.

Regards and enjoy the music.
Raul.