Posted this on diyAudio
just curious what you guys think too:
I'm considering a pair of bookshelves to pair with my LMS5400 subs. Planning of using a RAAL 70-20XR as a tweeter. Can someone compare/contrast the
offerings such as:
Accuton c173-6-096e
Accuton c90-6-078
Audio Technology C-Quenze 18 H 52 17 06 SD
ScanSpeak Illuminator 18WU/4741T-00
ScanSpeak Revelator 18W/8531G-00
You're going to want bigger/better midwoofers if you're using multiple subwoofers with LMS Ultras. 7-inch pea-shooters don't apply.
Which would you use with the RAAL 70-20XR? and why?
None, though I also wouldn't use the latest forum boner tweeter, either.
I'm also open to a 3way as well to pair with the existing subs.
MUCH better idea. If you can't/won't constrain tweeter directivity, then you need to use a three-way with a very small midrange. The crossover is more complex, though.
Selecting one driver such as the RAAL is a bad way to start a speaker design.
First you set the parameters of what you want your speaker to do at a specified budget.
Then you look for drivers that are promising for the task at hand. ***
Agreed. Drive-units are just tools. People seem to forget that.
I would say that ribbons are hard to work with and integrate with a woofer. They are not inherently superior to dome tweeters and in many respects inferior.
Ditto.
Two way designs using ribbons are especially problematic.
Ditto, unless we're talking an NHT SuperZero-sized speaker.
If it is bookshelves speakers you are planning then a three way speaker is a nonsense, as you have an extra crossover point. Crossover points always cause problems, no matter which ones they solve. So it is always a good idea to minimize crossovers.
Yes and no. It is better to maintain a constant power response than to avoid crossovers. Though someone unskilled in the science of crossover design - and now it really is more science than art! - well...probably won't get good results either way.
If these speakers are always going to be used with a sub, then a sealed or a labyrinth design with a -6 db point around 80 Hz is an excellent plan.
No need to waste effort with anything other than a closed box, unless one is attempting a cardioid midbass pattern. A degenerate vented box ("transmission line") still goes dipole below tuning.
To design a three way speaker to meet those criteria is absurd.
..and here you go off the rails. There are many good reasons to go 3-way. For example, one wants controlled directivity, reasonable efficiency, and high output capability, in a narrow package. (Others should note, as TLSGuy stated earlier, the configuration of the speakers should flow from the design criteria; starting with a drive unit and trying to kludge a speaker together around it isn't a good idea.)
Yes, probably a 2-way with a concentric or waveguide-loaded tweeter and a 10-12" midwoofer blended with multiple subwoofers starting at 120Hz or so is probably the optimal way to make music in most homes. But sadly many of us just can't fit mains that wide. So a 3-way with a 5" concentric driver or tweet loaded in a waveguide and 4-5" mid range and supplemental woofers, something like
this with the port plugged - is just about the only practical approach.
What is the knock against ribbon tweeters? Just curious.
In addition to the dispersion problems, look at a ribbon. All those sharp edges around the diaphragm are bound to cause diffraction. For the Raal, look at the faceplate? See those teeth? In pro audio terms, that opening is a
diffraction slot. The diffraction slot is the source of "horn honk."
I suspect that's why I invariably find ribbon tweeters fatiguing over a long listen. Just as I find hornloaded speakers that use old-fashioned diffraction slots rather than modern waveguides fatiguing.
Can I ask your opinion on the Salk offerings and possibly the Philharmonic offerings?
Salk does great woodwork, but the driver choices he makes are often puzzling. Smooth and even midrange pattern seems not to be a design criteria.
The Phils are interesting. Dennis does the ribbon thing right by using a narrow midrange and effecting the crossover where (horizontally, at least; similarly even coverage in the vertical axis has not been shown to be as important) both mid and tweeter are basically hemispherical radiators.
While the Phils would likely not be ideal for a very live room or for placement close to the sidewalls (due to the very wide coverage), I can see them doing very well in a deader room with a lot of space between the sidewalls and the speakers.
