Why build towers?

[davidB]

Mid-sized animals(dogs,small children,etc) are a very good reason for a tower with a low center of gravity.

Separates like the Taurus, Continuum w/bass(base?)unit, etc are good as we age and collect injuries.

A good compromise. Also easy to try different mid/high units.

[fpitas]

Mid-sized animals(dogs,small children,etc) are a very good reason for a tower with a low center of gravity.

Separates like the Taurus, Continuum w/bass(base?)unit, etc are good as we age and collect injuries.

A good compromise. Also easy to try different mid/high units.

I built mine with separates so I could stack them in place myself, but also because I think it's easier to make smaller cabinets non-resonant.

[dlneubec]

As with all things audio, there are implications with every decision you make in speaker design. Why towers? Here's a couple of my thoughts:

1) You prefer the look of towers.
2) You prefer the potential for improved stability/safety of towers over stand mount for children or pets
3) You want to leverage the space that would be committed to stands anyway to provide improved or extended speaker performance/response, whether single driver, 2-way, 3-way..... etc.
4) You want to improve midrange clarity and distortion by reducing the bass load that driver has to handle and as a result, potential doppler distortion from that driver
5) You can't or don't want to use multiple subs placed all over the room to even out low bass response, either because of space, aesthetics, SAF, $, etc.

As to the Allison boundary affect. Basically, where the cancellation that occurs is based upon the location of the bass driver (specifically the driver covering the 100-300hz range) relative to surrounding boundaries floor, front wall, side walls, ceiling, etc). For most stand mount speakers and traditional tower speakers (those with the woofer mounted up close to the midrange), that cancellation dip occurs in the 100 to 200 Hz range. So if you are using multiple subs crossed at under 80 or 120 Hz, you aren't going to address the dip you will get from your stand mount 2-ways or traditional towers, assuming they are playing down to 80-120 to match the subs. The cancellation will occur based upon the location of the driver that covers the 100-200 Hz frequency range, regardless of stand mount or tower. Multiple subs will smooth the frequency response only in the frequency range they cover.

There are several ways to address the "Allison dip". Place the woofer or woofers near any boundary. The closer to two or more boundaries, the smoother the response and the more boundary gain you obtain. Just look at the Allison designs to see how Roy addressed it. Woofers near the floor, woofers near the floor and front wall, woofers near the front wall only. He used all these techniques to smooth the bass response, even in his 2-ways. Woofers on the back of a speaker placed close to the wall will also work. But for these to work, they have to cover up to at least 200 Hz, ideally higher.

Personally, I have done many designs with subwoofer built into towers, sometimes two subs/tower, crossed in the 220-350 Hz range, woofer(s) placed near a boundary, and found them to do an excellent job of addressing the Allison boundary affects in a couple of ways. First, you get boundary gain when you place the woofer near a boundary gaining 6-9db output from your woofers when compared to a woofer mounted high on the front baffle. You smooth the bass response through the Allison dip range. You also get a start on the benefits of multiple subs to smooth out the bass response below the Allison dip, but without have the drawback of additional subs around the room. Frankly, I've never felt the need to use additional subs with any of these speakers, either for music or HT, but if one has the inclination, space, etc. to add more subs, it could help smooth the response further in their operating range.

[Geoff Millar]

Thank you for those most interesting and useful comments, Dan.

Geoff

[camplo]

... what are the advantages of building towers and larger speakers that produce those low frequencies if those frequencies are better suited to be played by multiple distributed (sub)woofers? Instead of building a three- or four-way tower, should the default decision instead be bookshelves and multiple subwoofers crossed at 80Hz to get an even in-room response?

Its not about finding magic locations, its about having multiple locations and then summing them together, regarding your multi sub, for small rooms approach. So a large main that can help out the subs is yet another source to be summed with the rest of the low end woofers resulting in a smoother FR.
The best location in the room for any speaker is either soffit mounted or corner loaded....For my planned system which is a large one, I have 18"s on the bottom with a 15" mid and a horn on top.....These are my mains.....I intend to add two more separate subs for the multi sub approach but, as is, Corner loaded, I should end up with a very decent FR. If I were not able to corner load my mains, it would be much more important to create the multi located bass playback situation that generates the good FR we want.

[critofur]

..that cancellation dip occurs in the 100 to 200 Hz range...

I refer to this as "floor bounce cancellation", because I found this flaw myself trying to figure out what was wrong w/the sound - sure, other folks "discovered" it before I did, but, it's negative impact is significant enough that it was driving me nuts until I did enough experimenting to figure out exactly why my "stand mount" speakers were really lacking in some way that was hard for me to put into words, but, I basically accidentally found to be fixed by:

Placing subwoofers under each stand mount speaker, raising the crossover frequency on the sub, and making sure the sub's woofer was facing me. (In effect, the end result essentially turned my 2-way stand mount speakers into 3-way towers)

Eventually, I've come to this conclusion: stand mount speakers simply cannot sound "good" without the caveat that they'll have this FBC which I find bothersome - perhaps some people are less bothered by it, or, are simply blissfully ignorant but would be bothered once they heard the improvement that could be had by filling in that dip.

TLDR: you simply can't achieve very high quality sound [in a typical listening setup] without implementing some type of "tower speaker" design even if your cabinet is multiple parts.

[Blenton]

Where's the 'mind blown’ emoticon when you need it... You just connected so many dots in my brain it might have resembled a synapse. Muchos grassius seenyor!

[JonathanPenner]

Good point. It makes sense that the cancellations can occur at any boundary. That’s certainly another reason why floorstanders are beneficial, especially if the cancellation from behind the speaker can be addressed.

dlneubec I’ll check out some of Roy Allison’s designs!

[Blenton]

Ummm... is that it? I still half a can of coke and some popcorn left. Dang it!