Home Theater Correction using TTD

hulkss

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It is time for the ultimate TTD correction solution with Audiolense. For this I do not need to be concerned with latency, I will be playing content from my hard drive or blu-ray disk, not streaming from the internet. To avoid having to change signal routing in my MOTU 16a when I switch from Min Delay to TTD, I will reuse some of the previous full range set-up.

Here's the speaker setup window. My sub array will act as a single bass driver for each of the three front speakers.

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Here's the input signal routing. I drop all the channels except LFE by 10 dB and then combine the LFE channel with the center (this is discussed in my subwoofer array thread). I do not use the 10 dB amplification of LFE in this case.

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Here is the crossover setup. With the linear XO filters and TTD I have selected narrower filters than when using minimum phase XO. I have also set all bass XO at 100 Hz. I don't want my sub array to be -6db at the typical 80 Hz XO. 100 Hz gets me a better chest thump from the subwoofers.

I do not re-route bass from the surround channels. I let the surrounds run full range (mine are good to 40 - 50 Hz which is fine). I do not want to blur the sound from my front main sub array with those signals. The surround signals are intended to create ambience in the room, not compete with drums and bass guitar up front.

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Here is the MOTU signal routing matrix. Input channels from the Audiolense convolver across the top, analog outs to my amps on the left. Three separate bass signals are mixed and sent to three subwoofers. To the mixer loop at the bottom and back on Main L at the top.

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hulkss

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Audiolense has really efficient work flow for measurement and correction of multi-channel, multi-amped systems. After an all-in-one measurement and some experimenting, I shortened the time windows (cycles) a bit, turned off pre-ringing prevention, and selected TTD per driver. I'm using a minimum phase target (that really helps keep pre ringing to a minimum).

Under partial correction, I don't bother correcting the surround speakers. They are passive speaker systems that are fine for ambience as is. Using a target as EQ is enough for them. It's easy to improperly over-correct a surround speaker that is not directed at the measurement mic.

I stopped frequency correction of the front speakers to let the drivers roll off naturally at the very top and I stopped TTD correction above the operating band of the upper crossover filter.

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hulkss

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Always look over your correction filters for issues. They can have weird problems. A good filter looks like the opposite of the measurement. Here's the sub-bass measurement and filter, almost perfect opposites.

Next is the full system filter set. The digital gain of your system is limited by the high point on your filter set. Oddly for me the tweeters max out first. I switched from 8 to 16 ohm drivers and I could use a bigger amp there.

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hulkss

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The end result is a frequency response that is right on target for the front mains and great looking step responses too.

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hulkss

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OOPs.......I just noticed I have "Ugly" impulse responses.

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So I unchecked TTD correction per driver. All better now and the step response is still good.

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eriksinn

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My AV System  
Preamp, Processor or Receiver
Arcam FMJ AVR550
Additional Amp
Marantz SR7008
Universal / Blu-ray / CD Player
Marantz UD7007 / Cambridge Audio Azur 851C
Front Speakers
Elac Adante AS-61
Center Channel Speaker
Monitor Audio Apex A40
Surround Speakers
KEF T301
Surround Back Speakers
Dynavoice Magic FX-4 v.3
Front Height Speakers
Magnat Interior IC 62
Rear Height Speakers
Magnat Interior IC 62
Subwoofers
SVS SB-1000
Video Display Device
LG 55C9 / Optoma UHD51a
Screen
Kauber Contrast-S
Streaming Subscriptions
Pro-Ject Xtension 9 / Ortofon Quintet Black
Hi, thank you for this great thread. I'm a beginner with FIR filtering and no experience at all with audio interfaces like MOTU, therefore my questions will probably be really basic and some of them not really smart. :) ... However, here they are:
1. What kind of latences do you experience in this setup and how do you handle it to avoid lip sync problems.
2. What kind of convolver do you use and where in the setup is it positioned?
3. Is it possible with MOTU to route the analog input signals from the AV processor through the computer USB ports (where the convolution would be deployed) and then forward it to the analog outputs? I hope this question make sense.
 
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