Open baffle because all wooden boxed speakers colour the response DRASTICALLY . You dont really realize it till you have lived with open baffles for a while and then gone back to wooden boxes- the bass from a wooden box is just plain mud in comparism to an open baffle.
Of course there are various degrees of this "muddiness" and some wooden boxes are much better, through the use of extensive bracing, heavier materials and exotic materials (aluminium etc)
Wooden boxes can produce more power and "thump" but for pure definition and realism it is very hard to beat the sound of an unihindered driver being allowed to follow the music without restriction or resistance.
Again, this is a little simplistic, and there are many conditions that need to be followed in order for an open baffle(OB) to outperform a wooden box.
Sadly, there has been a lot more effort in designing drivers for boxes than OB's and good drivers, designed specifically for OB's are rare.
The baffles have to be of a largeish size to get reasonable bass , and for the lowest octaves of bass , DSP or subs are required.
There are a few companies making drivers for OB, with different degrees of success. For my money, the best I've heard are the French Supravox drivers.
They have extended frequency response , which is relatively smooth , and fulfill another requirement for audio bliss which is high efficiency. (HE)
High Efficiency = Dynamics. Its as simple as that, if you want excitement and to get as close to realism as possible , then the higher efficiency your speakers have , the better they will be at extracting dynamism from your recordings.
Again, very simplistic and there's a huge caveat to this statement.
HE drivers are invariably coloured and often a little (or a lot) ragged. Think of Lowthers, which might be impressive at first listen, but become quite demanding to long term listening. Some use complex notch filters or DSP to tame them, but its infrequently successful.
The Supravox are not perfect, but they are smooth enough to play music very well, and with the advantages of high efficiency produce extraordinary amounts of micro and macro dynamics.
I've written in this blog of my Supravox 215 Field Coil drivers, used with 15" Eminence bass drivers and Raal tweeters.
The 215 are used full range, the tweeters have a simple 6dB crossover , and the bass drivers use DSP to roll of the upper bass and para EQ to equalise the lower bass response.
With a nearly all tube system, it works a treat , and while perhaps not a reference quality speaker , its damn impressive.
Its impressive because it has nearly the dynamics of a full horn system, without the colouration that horns always bring with them.
Bob sent me a pair of the Supravox 285 - , and being larger than the 215 you would expect better bass response from them.
I built a baffle 1200mm high and 600mm wide with 300mm sides - no back , so essentially a 1200x900 mm baffle.
The only unused tweeter I had to hand was a Yamaha horn tweeter with a compression driver rated from 800Hz to 20,000 Hz.
Aluminium horn that rang like a bell , but a generous layer of lead sheet on all exterior surfaces minimised that, and using it a high crossover frequency would alleviate any mid range raggedness.
The 285 has on axis response to 7000Hz , so I used a 6dB filter at 4500 hz for the horn.
300B SE amp on 285, EL34 PP amp on horns .
First surprise was how good bass was, it doesn't do sub bass, but what it does do is defined and reasonably powerful. A sub at <50Hz would compliment it , but not neccessary for 90% of music.
After an hour of adjusting levels and listening to all sorts of music, I decided to try a 12dB second order crossover on the horn.
Perhaps a bit smoother , more listening needed. Importantly , where it is used it doesn't sound "horny" , but matches the 285 well.
The Supravox aren't cheap, but the results are quite unlike anything you will hear from a box speaker- you will hear every inflection and tilt of the music, every little note and the smallest detail will reveal itself , you will hear everything. And it will sound natural and musical , without any box woodiness.
If you have a first class preamp capable of delivering all the music (a Supratek!) then you owe it to yourself to at least listen to a well sorted and infinitely satisfying Supravox OB.
And Bob tells me the TQWT designs are also extraordinary.
