A different tilt on things.

[VantheMan]

Just to provoke signs of life:
I recently spent a bit of time checking stability, levelness, distance from rear wall etc of my WD25TEx speakers. Mine are on improvised isolating plinths using screw-in rubber cone like bungs instead of spikes and thickish felt pads between marble slab and the boxes themselves. They wobble like a jelly if you touch them but I don’t touch them and they seem to work at least as well as spikes and I was tired of having a dartboard instead of a wooden hardwood floor due to conventional spikes. My tweeters have always been around ear height but this time I decided to inject a tilt-back factor by using thicker felt pads up front than those at the back. So much so that my tweeters now seem to aim a fair bit higher , more like at the top of my head or even over my head. This would seem to have levelled up the power output at higher frequencies and cymbal brushwork is much more obvious and easy to hear. Could it be that the fact that in these speakers the back tilt helps not because of where the tweeter aims but because the woofer has a fair bit more mids info than is usual due to the highish crossover point and is therefore also more directional than would be the case in a 3 way ? or does it seem to have improved by getting over the negative effects of my largish coffee table between me and my boxes. Has anyone else tried tilting their WD25ts back a bit ? Discuss

[bob orbell]

I think what is happening is because the HF travels at greater speed than LF's, you have now changed the time that the sound arrives at your ears, it is now most probably arriving at the same time, this is good and has been talked about a lot over the years. This is very much like a good RIAA stage and a bad one, the good one has more precise time Constance and the bad one, poor time Constance. Bob

[VantheMan]

Hi Bob,
So, inother words, so a layman canunderstand it, rather than speed up the arrival of mid frequencies from the woofer, I mayhave slowed down the arrival of the higher frequencies from the tweeter because my ears are nolonger in a straight line with the Millenniums. I had even thought of some strange lobing effect present caused by my coffeetable so that it is only now, with them pointing higher than my head, that hi frequency info is reaching me in time because it is curved downwards rather than feeding straight out.
Not to worry, it definitely sounds for the better.
Cheers,
Chris

[A Stuart]

Originally Posted by bob orbell

because the HF travels at greater speed than LF's

According to good old Wikipedia "In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO2 which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies (> 28 kHz).",
and goes onto say
"The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about 0.1 m/s as the frequency rises from 10 Hz to 100 Hz. For audible frequencies above 100 Hz it is relatively constant."

But apparently beer and hot chocolate cause weird effects. Is either of these a factor in your house, Bob?

Directional effects seems more down to earth explanation. Given that the wavelength at 3kHz is around 10cm, then altering the driver to ear distances by a few mm by tilting might just about be significant.

Alastair

[VantheMan]

I still think this has more or at least as much to do with tilting the mid-woofer and is not limited solely to the tweeter. In fact with my dodgy lugs, I’d guess a fair bit of what I hear comesvfrom that driver.

[VantheMan]

Of course, I meant to say “ a different slant on things”. I’ve been away too long.

[VantheMan]

I’ll carry onrambling about my wd25T experiences, if anyone is interested: After a forum member (Stefi) mentioned on here his idea that the main brace in these speakers might be a bit too close to the woofer and thereby unwanted rebound waves be affecting its linearity, I got in touch with him. His being much more experienced in building speakers and tuning crossovers than I am (not difficult) I have left the moretheoretical crossover work to him and after discovering that my aperiodic vent foam was non existent having crumbled away (as has Stefi’s) I set about the more menial task of drilling out 2 more 63mm diameter holes in my main brace on either side of the central hole prescribed in the original plans. Yes I didhold onto the discs I had cut out just in case they needed to be hastily glued back in place but it sounded quite promising and I decided togo ahead and so I set out sorting out the stuffing of my vent and boxes. My original stuffing was not as Peter had prescribed as I was late getting started and I never in fact bought a complete “kit”, having been given the Millennium tweeters and buying the woofers from Falcon. I used extra amounts of the Arboseal “gunge” to line the inner walls of my boxes and then acoustic felt on topand then some polyester stuff from Monacor here and there without any sort of direction. Bass had always seemed less than perfect regarding consistency so in for a penny…….. I had little to lose ……… to be continued.