View Full Version : Speaker Tilt = Time Alignment?


Xtinc
05-08-2010, 10:46 AM
I plan on building a pair of speaker stands for some bookshelf speakers I have and was curious what a better design wouild be. My ears are approx 3 feet off the ground when sitting in my listening position. Speakers are Yamaha NS670, Advent 4002 (possible ewave soon) and pair of older Magnavox 2way with horns.

Is a lower stand (1ft) with a tilt back or higher stand (2ft) with a flat platform better? I know other factors may come to play, but I was wondering about the tilt/time alignment factor. Would this have any significance with the speakers mentioned above?

thanks!

gkimeng
05-08-2010, 11:33 AM
I prefer flat. A tilted speaker means that your ears not only have to be at the right height relative to the speakers, but also at the right distance. This is less of an issue with speakers that have wide vertical HF dispersion, but it doesn't go away.

I have never been able to hear any difference in "time aligned" speakers, and it's a non-issue for me. YMMV.

4343
05-08-2010, 11:42 AM
Tilting the cabinets back will put some speakers in a better position as far as the time alignment of the drivers, but it only works if the tweeter is shallower than the woofer. For the horns, with the sound source farther back, you might need to tilt forward. It's all about the acoustic center of each individual driver and the distance to your ears.

Shallow tweeter+deep woofer=Tilt Back.
Deep tweeter+less deep woofer=Tilt Forward.

This ignores the directional characteristics of the drivers, of course. You might find with a shallow woofer and a very deep horn that so much tilt is required to align the acoustic centers that you are outside of the horn's vertical pattern. Spraying the carpet or ceiling, not the listening position in effect. A separate cabinet (or none) for the horn is often used to allow for positioning the horn further forward without aiming it too far down. Flying them works pretty good though...

Coytee
05-08-2010, 03:22 PM
Why not use an active crossover, then you can insert any amount of signal alignment you want.

Zilch
05-08-2010, 03:32 PM
Because that requires an active crossover, multiple amplifiers, knowledge of how to do it, redesign of the loudspeakers, and measurement capability to verify the result.... :dunno:

orionkc
05-08-2010, 06:17 PM
These work very well for me. I alternate between the NS-690 and the ADS L-810. They are tilted.
http://i228.photobucket.com/albums/ee307/orionkc/Yamaha%20NS-690/122_2236.jpg

JohnVF
05-08-2010, 06:20 PM
I have never been able to hear any difference in "time aligned" speakers, and it's a non-issue for me. YMMV.

My mileage varied. :)

I used a stand with back-tilt on my old KLH sixes..helped with imaging and the overall coherency of the two drivers sounding like one source but it was a slight improvement at best. My current speakers are time and phase aligned and they don't sound like 3-ways, they don't sound like drivers or cabinets or anything....just a big open sound.

sm19422
05-08-2010, 09:54 PM
Having the front of the cabinet sloped 7.5 degrees using a tweeter and woofer with voice coil centers closely spaced about 6 inches apart, gives a zero plane delay. Most flat baffles designs have the listener hearing the tweeter after the woofer.

Coytee
05-08-2010, 09:56 PM
Because that requires an active crossover, multiple amplifiers, knowledge of how to do it, redesign of the loudspeakers, and measurement capability to verify the result.... :dunno:

Well, it does appear I screwed up. I read him to be saying he was building a new speaker (not stands) and wanted to know about tilting the speaker back which I interpreted to mean having a front to rear slant on the front baffle to gain this signal alignment.

Seems I had my stupid pill for the day :D :yes:

Ghoulardi
05-08-2010, 09:56 PM
How does the amount of MY angle apply to all of this. At times I become quite askew during a listening session...possibly even obtuse...:smoke:

JohnVF
05-08-2010, 11:18 PM
How does the amount of MY angle apply to all of this. At times I become quite askew during a listening session...possibly even obtuse...:smoke:

My speakers came with a diagram for where you're supposed to sit in relation to them for the best imaging. It works....huge difference in moving just a few feet out of the right spot. It's not that they sound terrible in other places, just that the full effects come into play in a certain place.

Zilch
05-09-2010, 01:34 AM
Most flat baffles designs have the listener hearing the tweeter after the woofer.Nope, opposite, unless it's hornz.

[That's why they tilt (or move) 'em back.... :) ]

ehoove
05-09-2010, 03:39 AM
I must be missing something here. If a speaker stand tilts the whole cabinet, Wouldn't all drivers be affected? The factory stands for my Polk Monitor 10's tilt the cabinet back, but the drivers are still not time aligned by any means.
Regards,
Jim

speaker dave
05-09-2010, 07:11 AM
I experimented with system tilt for time allignment years ago. It worked with a 2way system but took a lot of back tilt, like 30 to 40 degrees. A 5 degree tilt won't do it.

This puts you way off the design axis so the crossover (if well designed) will need the tweeter polarity flipped. I do recall that the response to square pulses improved.

Did it sound different? Sure, now I was bouncing half the sound off of the ceiling.

David

spkrdtr
05-09-2010, 08:04 AM
Hi Dave.
That tilt you described seems quite excessive. However, Spica TC-50 is one known exception that comes to mind.

Most tilted fronts on commercial speakers sold today seem to me (visually) to be in the 15 to 25 deg. range.

whoaru99
05-09-2010, 08:12 AM
I'm with speaker dave on this. Unless the tilt is very "tilted", I don't think you're gaining too much in time alignment with the typical tip back distance in a speaker stand.

If anything, it's more an attempt to aim the tweeter at ear level.

dnewma04
05-09-2010, 08:28 AM
Smart crossover designers account for the time alignment and randomly tilting back speakers will absolutely end up in the mixed bag of results most are seeing here. If the speakers aren't designed with a tilt, the only reason I can think of to tilt them would be if optimal positioning isn't something you can get away with and you have to end up with aiming the speaker at the listener.

Just tilting them for time alignment reasons is going to be a rather random experiment.

speaker dave
05-09-2010, 10:41 AM
Hi Dave.
That tilt you described seems quite excessive. However, Spica TC-50 is one known exception that comes to mind.

Most tilted fronts on commercial speakers sold today seem to me (visually) to be in the 15 to 25 deg. range.

Hi Carl,

Its a bit hard to define the tilt except on a case by case. Roughly you would need to get the voice coils in allignment, so depth of the woofer and vertical distance from woofer to tweeter is the primary factor. The natural rolloffs and the delay of the crossover networks will add further delay (more to the woofer) so you may need to tilt even further.

I'm not a big proponent of linear phase. I just remember trying to get a two way to work while watchiing square pulses. Sufficient tilt along with a tweeter polarity flip gave a reaonably square pulse with the system I was playing with.

David

hififarmer
05-09-2010, 03:06 PM
I've listened to the Vandersteen's that use a tilted tweeter, and although they sound exceptional I'm not sure they achieve perfect alignment. I can't get past the idea of the tweeter pointing upward, although in theory this should correct for lobing. I recently purchased B&W dm2000's that use time alignment in their passive crossover and the alignment is definitely significant. I haven't done much research into it yet, but my concern with this concept is what the circuitry does to the signal. I've built speakers in the past and have used an MTM design to compensate for lobing, but I've never tried to correct for time shift by tilting or by using a crossover to delay. I've found the biggest improvement is by using extremely good quality components in my crossovers. Premium caps and coils can make the cheapest Audax drivers sound better than the more expensive scanspeak drivers with cheap components. Way off topic I know, but my point is that putting a little angle on your stands isn't going to hurt anything, but unless you have the ability to measure the delay it will be hard to achieve the correct angle unless you make them variable and just go by what you hear.

Susurus
05-09-2010, 04:12 PM
Sometimes the real advantage isn't so much the tilt on the stands, it's that they are on stands vs. on the floor.

My best speakers are Hales Rev 3's. When he made the upgraded model 5 he went to a slight tilt-back on the front baffle. . Goes without saying that Hales knows more about loudspeaker design than I ever will... :music: I tried my 3's tilted back like that and couldn't hear any difference though. 19mm Ti dome Vifa tweet has pretty good dispersion so I could have tried a steeper angle. More worried about those 100-lb concrete baffle towers falling over. :eek:

I have some very nice DQ-20 and DQ-12's with the mids and tweets on a separate limited baffle that's both stepped back and tilted back, atop the front-facing AS woofer cabs. They're 1st order. Yeah, they do image.

Always liked Vandies. Difference is thier tweet is mounted on an open baffle, not even a limited baffle like the DQ's. Would like to hear Spicas, which have higher angles, but I don't expect I'll want 2-ways since I like bass. (Watt Puppys angle back, sure, but they're kilobucks.)

For my BG RD-75 ribbons project I'll go active--no way around that at least during the testing phase... Behringer 9624 is what I'm thinking since it has delay.

sm19422
05-09-2010, 09:07 PM
Nope, opposite, unless it's hornz.

[That's why they tilt (or move) 'em back.... :) ]

Loudspeaker Design Cookbook p.91 figure 7.1 shows the comparisons. Horn loaded tweeters are correct for 7.5 slope. None horn loaded tweeters require more tilting. It depends on the ratio of vertical and horizontal and displacement.