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  #11  
Old 1st September 2006, 06:14 PM
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petercom petercom is offline
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Default Re: WD25a vs WD25t

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Originally Posted by Primalsea
Would this be a similar situation with the WD25 standmounts imaging better that the floorstanders but having less bass.

I'm not sure if its interaction with the bass frequencies that can muddy imaging or if good imaging is just a virtue of smaller boxes and smaller drivers on their own.
The standmounts and the floorstanders image the same. There is no reason at all why large speakers can't image. The main reason that large speakers usually deliver a 'smeared' image compared to small ones is because the larger cone does not usually approach the dispersion of the dome of a treble unit as you approach the crossover frequency.

We managed this in the WD25 by a) allowing the cone to breakup gradually through the upper midrange, so it is only the centre portion of the cone and the dust cap that is producing output above 1.5kHz and b) lowering the crossover frequency to 2kHz so that the treble unit is handling a lot of the upper midrange.

If you have heard a 3-way speaker that doesn't image either then it is usually because of inept crossover design (it is difficult enough to design a 2-way successfully, designing a 3-way increases the difficulty factor by 4).

The usual reason given for narrow baffle speakers giving 'better' imaging is because there is less diffraction. Where this came from I don't know as a little thought indicates that the narrower the baffle the greater the diffraction. It is possible that it is a truism based on the concept that the further the baffle edges are from the drive unit the more delayed in time the secondary reflections from those edges reach the ears of the listener. In fact there is very little evidence that secondary reflections from baffle edges are audible at all as their level is very low. In fact there are greater problems from drive units that see a step in the response caused by narrow baffle widths in the midrange area. In addition, if you use a grille, the relatively close edges of the grille to the drive unit(s) form a cavity which introduces all sorts of tonal coloration.

One difference that is obvious between a floorstanding and stand mount speaker is that the relationship between the floor and the bass driver is altered. On a pair of open stands the stand mount lessens the bass driver's coupling to the floor compared to the baffle conjunction to the floor of the floorstander. If your room has bass resonance problems then the stand mount will lessen these by not coupling to the room modes so well. This could be a reason why stand mounted speakers are preferred in small rooms where the room modes are more audibly obvious and troublesome.

So the floorstanding WD25t will deliver a more powerful bass performance partly because of its greater internal volume that allows better bass extension and also because of its better coupling to the room. In other words it 'drives' the room better.
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Old 1st September 2006, 08:32 PM
Primalsea Primalsea is offline
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Default Re: WD25a vs WD25t

I never seem to be on one learning curve and they are never linear either!

Many of the larger speakers I have heard have not been just 2 or 3 way designs. Some KEF reference speakers had 1 tweeter, 2 mid drivers and isobarik bass drivers inside the cabinet. Martin Logan summits are electrostatics with 2 bass drivers at the bottom.

So if I understand what you said correctly I you have these "non conventional" set ups with many drivers the task of designing an optimised crossover becomes a mamouth task often not accomplished. Although the KEF's and the ML's sound good they just don't image like the Kans.

Also I guess that it's partly true that smaller speakers image better that larger one by virtue becuase the designer has to think less about intergrating a large bass driver which tend not to beam with the mid range, which tend to beam.

So really large speakers are capable of fine imagine but it's a difficult task which in reality does'nt happen often.
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