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Time aligning tweeter
Time aligning tweeter
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Old 16th September 2021, 09:31 PM   #41
ThatSoundsGood is offline ThatSoundsGood
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This is how I figure out the tweeter delay. I put both speakers on the same baffle and then bi-amp them. I put a LR 2nd order crossover (1600Hz or whatever you think is best) on both of them then flip the polarity of the tweeter. I run pink noise through them then use DSP to delay the tweeter until you see the crossover region flatten out. You might also see artifacts well above and below the crossover flatten out. If you go too far with the delay then it starts to get bad again (you will see peaks and bumps get worse). There will likely be compromise in this but pick the best spot then listen to it. Convert that delay (often between .1 and .2 milliseconds) into distance and you get your offset. (.1 milliseconds is .034 meters or 2.4 centimeters) Depending on what kind of tweeter you're using, you will generally get to a spot where the spider of the drivers lines up. My last design ended up being a little over 1.5", which means I now have to mount my tweeter 1.5" deep in a waveguide. This creates all kinds of other issues with diffraction, but it sound so much better than flush mounting the tweeter. So many people focus on frequency spectrum and don't deal with the phase. Phase coherency is sooooo important.

This process can be greatly affected by which drivers you're using and where your crossover point is. I always use a 2nd order and flip the polarity of one driver to get the phase to align, but you can change the crossover later, just make sure it is still in phase.
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Old 17th September 2021, 05:26 AM   #42
Mario Pankov is offline Mario Pankov  Europe
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Time aligning tweeter
Quote:
Originally Posted by Augusts View Post
The tweeeter has a very low resonance
And the sb woofers bresk up is at about 2khz. I think it would work witha a 3rd order filter . Plus I simulated this setup with an active xo at 1,5kHz and everything was fine. Flat response. I am low on budget I cant affford to buy more buy more buy more
"Work" and "sound" even acceptable are different things. 2Khz breakup means you`d have harmonic nodes at the lower corresponding harmonic frequencies and despite your flat crossover measured at some point in space, it will sound harsh. The Vifa tweeter misleads lots of newbies with its characteristics. Theoretically it can do 2Khz with a 4th order if you don`t push it a lot. And then come more problems due to directivity patterns. I`d abandon that idea - this tweeter is better suited for 3-ways or used in a waveguide.
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Old 17th September 2021, 01:47 PM   #43
hifijim is offline hifijim  United States
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Quote:
Having mulled this over, Augusts, it pains me to say you have chosen terrible drivers here.

This 8" 4 ohm metal one is a complete horror for midbass duties:
Yeah, this woofer is best used as the bass driver in a 3-way system. Looking at the OEM response curves, I am guessing that 800 Hz is the upper limit for a crossover. It is not a good candidate for a 2-way.
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Old 18th September 2021, 05:56 AM   #44
Augusts is offline Augusts  Latvia
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what about this?
2 way TL using SB23NBACS45 and SB29RDCN

you dont like it because its aluminum?
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Old 18th September 2021, 06:06 AM   #45
ScottG is offline ScottG  United States
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It's a good 8" lower midbass driver - quite nice as high as 600 Hz.

Midrange driver? Not so much - and in fact most 8" drivers aren't particularly good because of their off-axis behavior when used in a typical 2-way configuration.


2-way standard driver to choose is the Peerless NE180W-08: it's sort of unbeatable at its price for a 6" driver.

If you don't want to cut-into a face-plate to get the tweeter as *close as possible to the midbass - then this is about as good as you can get without spending a ton of money (..and in fact sounds better than most of SB's ring-dome tweeters, and many dome-type tweeters in general): SB26STCN-C000-4

Note a reviewer's comments here:
Midi 150

IF you want a tweeter with a bit more low-freq. extension for a range of crossover (types), then I'd look to the Peerless DA32TX00-08, but you'll really want to cut-into that face-plate to get the tweeter *closer to the midbass driver.

*this is largely about minimizing vertical "suck-out" (or dips off-axis vertically), which can be significant.
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Last edited by ScottG; 18th September 2021 at 06:31 AM.
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Old 18th September 2021, 06:12 AM   #46
norman bates is offline norman bates  United States
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Actually, anything at 2k, it would have a harmonic resonance at 4k, but it would be way higher than normal due to 4k resonance.

Simple cone harmonic distortion sneaks around notchs i think, i wonder if anyone has tested this..........


I'm liking the info on 4ohm paper sb23nrx 8", actually moving up my "maybe buy" list (for a 2k 6db passive).
Not perfect, but an option for me.
SB Acoustics SB23NRXS45-4

Scott, that peerless is back ordered till nov, big 5k peak.
I'd be suprised if they are still being made........

Curt campbell "slapshot" and mike chua "raven/cat" use daton's rs180p
Raven-CAT (Morel CAT378 + Dayton RS180P + DA270) – AmpsLab
MTM Speaker by Curt Campbell – Rhythm Audio Design

Last edited by norman bates; 18th September 2021 at 06:24 AM.
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Old 18th September 2021, 06:12 AM   #47
digitalthor is offline digitalthor  Denmark
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It's all a compromise. Add a 5" NBAC for midrange and shape the baffle to make rounded/edged corners (diffraction issues). Then cross around 500 and 2200hz.
This is why I love active systems... simply delay the signal to the tweeter... done.. still flat baffle.
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Old 18th September 2021, 06:38 AM   #48
ScottG is offline ScottG  United States
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Quote:
Originally Posted by norman bates View Post

Scott, that peerless is back ordered till nov, big 5k peak.
I'd be suprised if they are still being made........
It's worth the wait.. (..don't know why it wouldn't still be manufactured - it's their only premium offering at this size.)


-still, Augusts is in Latvia - I doubt he will have problems finding it in stock.


Tim's got it measured here:

"Vifa" instead of "Peerless":
Timothy Feleppa's Pages: Speaker Measurements - Woofers 5" to 8"
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Last edited by ScottG; 18th September 2021 at 06:41 AM.
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Old 18th September 2021, 07:14 AM   #49
norman bates is offline norman bates  United States
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Ne180w looks good.
Profiguy said no way 6db with its peak, 12db 2.2k and 4.8k notch.
2-way bookshelf Morel ET338 Peerless NE180
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