Time-align, TubaHT to LaScala

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DriftlessIA
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Time-align, TubaHT to LaScala

#1 Post by DriftlessIA »

I just finished building a 36" wide TubaHT LP subwoofer. I am trying to blend it with my '85 LaScala speakers. I am new to blending subs/speakers, DSP, etc. I would like to ensure that my speakers and sub are time-aligned. Given their locations in relation to my seated position, I assume that I need to add delay to my LaScalas. If so, what is the best way to go about doing this without effecting sound quality?

Current gear chain:
Bluesound Node 2i --> VTA ST-70 integrated tube amp --> LaScalas.
Bluesound Node 2i (sub out) --> MiniDSP 2x4HD --> Behringer NX-6000 amp --> TubaHT.

I assume using my MiniDSP 2x4HD to add delay to my LaScalas would degrade sound quality (?) If so, are there higher quality options out there?

What would improve if my speakers and sub were time-aligned? Right now, the crossover is set to 100hz. I may go as low as 80hz.

Distances:
Seat to LaScalas: 7.5ft (plus 2.6ft for horn length).
Seat to mouth of TubaHT: 5ft (plus 11ft for horn length).
20240119_075311.jpg
'85 LaScalas
VTA ST-70 tube amp
Bluesound Node 2i
TubaHT LP, 36" width
18" Ultimax, sealed

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Bill Fitzmaurice
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Re: Time-align, TubaHT to LaScala

#2 Post by Bill Fitzmaurice »

Time align with subs is seldom required, the wavelengths are too long for it to matter. If you have the ability to delay the mains by 10ms or so by all means try it, but it probably won't be audible. Besides, doing so could cause a sync issue with the images on the TV screen.

Bruce Weldy
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Re: Time-align, TubaHT to LaScala

#3 Post by Bruce Weldy »

You won't hear any difference by trying to time-align the 1-2ms that you'd implement. I wouldn't bother.

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Bruce Weldy
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Re: Time-align, TubaHT to LaScala

#4 Post by Bruce Weldy »

Bill Fitzmaurice wrote: Thu Jan 25, 2024 12:00 pm Time align with subs is seldom required, the wavelengths are too long for it to matter. If you have the ability to delay the mains by 10ms or so by all means try it, but it probably won't be audible. Besides, doing so could cause a sync issue with the images on the TV screen.
Are you off by a factor of 10? Using his measurements, it's under a 10 foot difference and if I remember correctly, it's about 11ft per ms.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: Time-align, TubaHT to LaScala

#5 Post by Bill Fitzmaurice »

Maybe, but for sure if it's 1ms you won't hear it. Even at 500Hz where time align is most easily heard you can hear 1ms.

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Seth
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Re: Time-align, TubaHT to LaScala

#6 Post by Seth »

To be really honest, I'm not entirely sure I understand the difference between Phase Align and Time Align in the context of Home Audio/Theater. When I hear time align, I think adjusting to compensate for offensive audible differences in sound arriving from two different sources that are very far apart, ie. Delay Stacks at a large outdoor concert venue. But, when I think of it in the context of Home Theater, my mind can only comprehend phase alignment between the LaScalas and the THTLP. Which, in my opinion, isn't 100% necessary. As long as you've flipped the polarity to verify you have constructive summation at the effective crossover frequency, you should be able to use different crossover types and EQ to solve any resultant small dip in the response curve. That said, I would if it were me. Just because I like to geek out on this stuff and I'd feel like the system is even more dialed in, even if it wasn't an audible thing.

Am I missing something, perhaps a distinction in the Home Audio world, where Time Alignment means something different than it would in Pro Sound?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bill Fitzmaurice
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Re: Time-align, TubaHT to LaScala

#7 Post by Bill Fitzmaurice »

Phase and time align are inseparable, you can't have the one without the other. It can cause serious issues, like the famous Eleanor Powell 'double tap' when her movie tap dancing routine was clearly heard as a double hit as the LF and HF horns weren't aligned. That led to the development of the Altec VOT. Its woofer wasn't horn loaded just for sensitivity, it was also to move the driver acoustic center back so it would be aligned with the HF driver on its horn. The HF assembly was also on a sled atop the cabinet, so it could be moved back and forth to get the alignment precise. Phase wasn't that much of an issue, as it takes a 1/2 wavelength difference between two sources to be audible, but of course as the sled was moved back and forth the phase response changed as well. The main challenge in live sound is delaying the PA to align with the instrument backline amps. In the home it seldom causes a problem so long as the subs and mains aren't 180 degrees apart at the crossover, and that's an easy fix. HT mains seldom have a problem either. For instance, the LaScala. It works just fine without jumping through time and phase hoops, and that's with a long woofer horn. You see much made about some direct radiators being phase coherent or time aligned, but in practice the acoustic centers of direct radiating elements don't have enough offset to be a problem with respect to phase or time. It does make for nice advertising copy.

Oh, yeah, I did mean 10ms. The speed of sound is 1130 feet per second, so a close enough time align for length of horn figure is 1ms per foot.

DaveMacKay
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Re: Time-align, TubaHT to LaScala

#8 Post by DaveMacKay »

I just finished a similar exercise and, although I don’t have a fraction of the knowledge that Bill or the other posters have, I’d be happy to share my experience with you.

I have a pair of 1986 La Scalas and two minimal-size THTLP subwoofers. Each subwoofer is powered by a 250W SPA250DSP plate amp.

My initial configuration used a Bluesound Node as my source. It fed a Yamaha R-N803 receiver. The sub-out on the receiver was connected to a MiniDSP 2x4HD. The 2x4HD controlled each of the subwoofers.

I tried several different passive networks in the La Scalas (AA, AL, ALK Universal, ALK Universal/4500) but was never entirely satisfied with how the La Scalas sounded.

I decided to remove the receiver (which didn’t have pre-outs) and tri-amp the La Scalas through a MiniDSP Flex Eight. The Bluesound Node is connected to the Flex Eight. The Flex Eight drives the two THTLPs and — via three Aiyima A07 amps (one each for tweeters, squawkers, and woofers) — the 6 drivers in the La Scalas.

I spent hours and hours and hours taking measurements with REW and configuring the DSP. It took a lot of work to configure the La Scalas so that they were +/- 3 dB across the frequency range (measured at 1m). I then worked with Mutli-Sub Optimizer (a very nice freeware program) to integrate and align the subwoofers. Finally, I used Dirac (available as an option for the Flex Eight DSP) to tailor the system to my room and seating positions.

I described the whole exercise (in tedious detail) in this post on Audiokarma:
https://audiokarma.org/forums/index.php ... k.1037354/

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Bruce Weldy
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Re: Time-align, TubaHT to LaScala

#9 Post by Bruce Weldy »

Bill Fitzmaurice wrote: Thu Jan 25, 2024 3:54 pm

Oh, yeah, I did mean 10ms. The speed of sound is 1130 feet per second, so a close enough time align for length of horn figure is 1ms per foot.
Now that I'm searching my memory......I guess I was thinking 1.1 ft/ms instead of 11. So, I was off by a factor of 10. Pesky decimals.

Mea Culpa

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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