why do bookshelves have "tighter" imaging?

[Davemcc]

tower speakers call for more amplifier power,

Not true. Bad generalization.

 

[TLS Guy]

Not true. Bad generalization.

Actually I would bet on the whole it is the reverse, as bookshelves are usually 5 to 6 db less sensitive than towers quite frequently.

Here is a small bookshelf that a lot of receivers would not drive.

 

[KEW]

Salks argument is correct, it has to be.

I just wanted to be clear on this. I don't dispute that Salks argument is correct. There is absolutely no doubt that given the conditions he outlines, there would be no difference! My point is that it is an impractical argument because towers and bookshelves almost never use the same cabinet volume (and, often, not the same drivers).
Certainly, if you look at Salk's most popular floor standing SongTower and bookshelf SongSurround speakers you will see that his own product does not adhere to the condition of maintaining cabinet volume.
Similarly, in his Veracity series, he utilizes his version of "Transmission Line" design into the towers which requires volume exceeding that of the bookshelf version.
I may have missed one, but I could not find any examples among Salk's offerings which adhere to the criteria he uses of towers and bookshelf speakers using the same interior volume!

While I like the sound of his speakers, I don't understand why he would contrive such an argument that is correct in theory, but not even applicable to his own product line.

If I am missing something, and someone can make sense of this, I would appreciate it. It really bugs me when someone presents info as "myth busting" using conditions which are obscure and generally not in accord with reality!

PS - I am aware of the NHT model 3 bookshelf and model 4 tower, which do adhere to the conditions of his argument and am sure that other examples do exist. However, I would estimate less than 5% of mainstream consumer speakers adhere to this design principle. Usually larger volume and, often, additional drivers are added.

 

[lsiberian]

I know what you are talking about from demoing speakers. I wonder if the floor boundary effect has something to do with the differences. I think this is likely a placement phenomena instead of a design one.

 

[yepimonfire]

Not true. Bad generalization.

generally larger speakers and larger drivers are more efficient. this isnt always the case but more often then not it is.

Emp impression tower: 87dB
Emp impression bookshelf: 85dB
Klipsch RF tower (5.25" drivers) 96dB
Klipsch RB bookshelf (5.25" driver) 92db
Axiom M2 Bookshelf (5.25") 87dB
Axiom M50 Tower (5.25) 89dB

now to prove my point about larger drivers generally being more efficient

Polk Audio CS2 (6.5" drivers) 91dB
CS1 (5.25" drivers) 89dB
Klipsch RB 51 (5.25): 92dB
RB 61 (6.5): 95dB
Axiom M2 (5.25): 87dB
M3 (6.5): 92dB

please keep in mind i am not a brand fan of any of these speaker mfg., i simply just know the specs off the top of my head because i have looked into buying these specific speakers several times.

 

[Davemcc]

generally larger speakers and larger drivers are more efficient. this isnt always the case but more often then not it is.

This suggests that generally larger speakers require less amplifier power. Just to be clear, I was objecting to the statement that towers require more amplifier power. So I guess we are all in agreement that that was indeed a bad generalization.

Emp impression tower: 87dB
Emp impression bookshelf: 85dB
Klipsch RF tower (5.25" drivers) 96dB
Klipsch RB bookshelf (5.25" driver) 92db
Axiom M2 Bookshelf (5.25") 87dB
Axiom M50 Tower (5.25) 89dB

now to prove my point about larger drivers generally being more efficient

Polk Audio CS2 (6.5" drivers) 91dB
CS1 (5.25" drivers) 89dB
Klipsch RB 51 (5.25): 92dB
RB 61 (6.5): 95dB
Axiom M2 (5.25): 87dB
M3 (6.5): 92dB

I also note (in bold) that for the driver sizes you listed, the most and least efficient speakers in your list are both 5.25" drivers. All other speakers fall in between (except the EMP) regardless of driver size. I think this negates any argument that larger drivers are more efficient.

I think the point that should be made is that each speaker must be considered according to it's own characteristics. Volume, efficiency, impedance and amplifier requirements are in the hands of the designer and are not inherent characteristics of the cabinet design, driver size or number of drivers.

 

[yepimonfire]

when using the same drivers in a tower and in a bookshelf the towers are more effecient is what i was getting at.

 

[Davemcc]

when using the same drivers in a tower and in a bookshelf the towers are more effecient is what i was getting at.

Not always. Again, it's up to the designers. I offer the Dynaudio Focus as an example. The Focus 140 bookshelf is 4 ohm 86 db using a 6.5" driver. The Focus 220 tower is 4 ohm 86 db using two 6.5" drivers.

You would expect that adding the additional driver would add 3 db to it's efficiency yet that's not the case. Each driver must be less efficient since the sum still only totals that of the bookshelf with one less driver. The designers could also have used the extra driver to lighten the impedance load from 4 ohm but chose not to.

In this case, suggesting that this speaker is more or less efficient or presents a more or less difficult load to the amp because of it's cabinet appearance would be false. Checking the specs is more necessary than generalizing based on it's cabinet's appearance.

 

[Brahms]

And why active monitors, being bookshelves, use to sound that much directional? is it becouse its clear and bright sound by nature?