Sloped baffle

Tim, although I don't understand the science, I recall reading that a sloped baffle is one component of achieving phase coherence. The proper cross-over order (1st, 2nd, and so forth), plus maintaining a specific listening position, plus, setting the cross-over frequencies at the right points, and so on and so forth also contribute to maintaining optimal phase coherence.

In addition, assuming that the drivers are in proper phase alignment in the overlap region of the cross over points, presumably there should not be phase cancellation or augmentation which will mess up the frequency response. That is frequency response should remain flat. But what about maintaining the proper harmonic structure of complex musical passages?

What other benefits are gained by locking one's head in a head vice in order to maintain the precise listening position, which presumably will enable the wave fronts from the various drivers to combine in an optimal phase coherent fashion at the listening position.

So ... how much of this is hype? What other characteristics make for a good sounding speaker? I used to think I had a handle on this this issue ... but no more.

BIF

Al and Ralph ... are you catching any of this?? Throw me a line. I'm sinking in techno quick sand.

Hi Bif,
Well, you've got a bit of confusion going on. A sloped front is used to align the voice coils on the tweeter/woofer or tweeter/mid/woofer. The idea is to get all frequencies starting on the same plane... Using an easy example is a 2 way... A woofer may be 6 to 8 inches deep and it may be 5 inches or to where the voice coil meets the spider & magnet gap (that is your alignment point).... The tweeter however may be less than 2 inches deep. On the sloped front, you can move the tweeters voice coil backwards in alignment to the woofer's voice coil by moving it up the slope.... Guys, I am on solid ground here, you can ask, who ever you want, I may not be known like Al or Ralph and don't come close to their electronics knowledge, but Speakers, I've got a good handle on.
There are tons of other issues that we haven't discussed. Moving the tweeter too far from the woofer (Depending on crossover frequency) can cause all kinds of problems with smearing, lobing and other dispersion issues. I was only trying to handle the original question of a sloped baffle and phasing.
I've had great luck using 6/12 crossovers on 2 ways @ 2500hz and find most of the time (depending on driver) that the speaker is in phase at the crossover point with those slopes. I am currently using an MTM, crossed at 1700 htz with 12/18 slopes, it is phase coherent at that frequency and time aligned in the crossover and images as well as anything that I've sat in front of.
Simple 6 db slopes cause less problems to deal with, I've used them with great success also, but its not the only way.... I hope this helps, Tim

A good step response and square wave response can be a significant indication of wave form fidelity, things that any other piece in the system should readably be capable of.
Much of the need for correct listening position for the appreciation of such design principles is in regard to distance from the speakers for proper driver integration, typically such designs have something of a wide horizontal dispersion, sometimes there is concern for the listeners vertical position. Many of us do serious listening while sitting somewhat centered between the speakers. Such designs at least offer a very good semblance of wave form fidelity at some position as opposed to never providing any semblance of wave form fidelity from any position. You don't have to sit with your head in a vice to get the virtues of such designs!

06-21-14: Bifwynne
Bombaywalla, I have a follow up question. How are small speaker manufacturers able to design speakers without the benefit of the R&D budget, engineers, and testing facilities that some of the larger manufacturers have at their disposal.

Bifwynne, as Timlub wrote earlier, I don't think it's necessary to have an extensive R&D budget, scores of engineers, anechoic chambers & mutli-million $ machines to make a good sounding speaker *iffffff* the manuf really knows how to design a speaker.
The companies that you stated need this to make-up for their lack of knowledge of speaker design. Focal has gotten better over the years. when I 1st heard their Electra series speakers, they sounded like sh**. Their ultra-expensive speakers have a big wow factor but nothing more. Those R&D budget, scores of engineers, anechoic chambers & mutli-million $ machines are good marketing hype items that sells. ;-) of course, my opinion based on listening to many of the cited manuf's speakers.

If one really knows what one is doing then it is possible to select & buy speaker drivers made by OEM speaker driver manuf that are superlative in their specs & performance. The next thing to do is to design a speaker integrating those drivers into a cabinet such that sum of the two is greater than each part.

Al and Ralph .... where are you??? :)
Bifwynne

You know Bifwynne, it is entirely possible that Al & Ralph cannot help us here. Raplh is an amplifier expert & the fine points of speaker design might not be in his 'quiver of arrows'. Same for Al.
Unlike explaining electronics, one cannot explain way speaker design unless one has dealt with this complex task.

Yeah, everything is a compromise - engineering is an applied science. By its definition it is supposed to make compromises to bring about a solution. The key is: which engineer makes the best compromise?

I believe that the 3rd link I stated clarified your earlier question re. the difference between time coherent & phase coherent.
The sloped baffle gives you a time alignment of drivers but does not tell anything about the time or phase coherence of the speaker.
Another thing I learnt was that just because a speaker has a 1st-order x-over does not mean that the speaker is time or phase coherent. I found that a lot of speaker manuf hide behind their using a 1st order x-over. I found that many such speakers used a 1st order x-over but their drivers were some higher order (such a 2nd or 3rd) which means that the driver performance rolled off with a higher order well before the 1st-order x-over kicked in. So, in effect, such a speaker is a 2nd-order or 3rd-order speaker & not a 1st-order speaker.
To be truly a 1st-order speaker the speaker has to be electrically & mechanically a 1st order speaker meaning to say that the driver's performance needs to extend beyond the x-over point so that the roll-off is being done only by the electrical x-over network.

it's complex material that cannot be absorbed in 1 reading. I've those threads printed off & re-read them from time to time to refresh my understanding. Each time I extract new info from them. Like Unsound wrote earlier the 1st thread & I think the other 2 as well are some of the very best threads to have appeared on A'gon.

I'll be off the net for a couple of days, so I'll end my part of this thread here. Simple 6 db slopes do not tell the story at all, Most would be amazed that when you put a simple cap on a tweeter expecting a 6db slope, many times you might find 9 or 10 db slopes.... There is a difference between electrical vs acoustic slopes... On my MTM speakers that I referenced... I may be using 12/18 slopes, but the finished acoustic slopes are 24db per octave. Speaker design with new drivers from scratch requires measurements, you can get amazingly close with some of the better software however... Then lastly to throw another wrench in the fire... you can easily get time alignment between a tweeter & woofer without being phase aligned, but you can never achieve TRUE phase alignment between a tweeter & woofer without time alignment. I haven't read either of the threads referenced above, but hopefully a quality speaker manufacturer out there has explain it better.
I was only trying to help, Tim