The official "Theta" thread - Page 111

In my experience the CEntrance is better than the 1.5+/- published spec suggests. I have tested 3 random samples and found all three to be accurate within .5dB. I don't know why they state the 1.5dB deviation on their cutsheet. In any case they represent a great value for $150.

The comment that Dan Francis made about the Audix TM1 reminded me of another point. The TM1 draws more current than does the Earthworks M23. Some laptops struggle to deliver sufficient current thru their USB ports to properly power it. In those cases the microphone won't run or shuts off at the most unfortunate times! Some of my customers have reported this problem. If you are currently shopping for a measurement microphone I suggest that you buy an Earthworks M23 over an Audix TM1 (if you can afford it!) just to avoid that potential grief.
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Best Regards,
Carl Huff

I purchased a used M30 for a little more than the Audix. I will send it in and have it checked and buy the calibration file. A friend has a Classe SSP800 that he wants tuned a bit more to his liking. That was good enough excuse . It might be wise to ascertain whether Theta might include a microphone for others. That would be a surprise though at the price.

I would not necessarily assume it should be a surprise. The price they are charging is substantially higher than Datasat charges for the Dirac Live upgrade in their AP20 SSP (the Cinema version). Even including a very good mic and USB pre puts Theta well above the upgrade cost charged by Datasat (the AP20 does not include a mic or USB pre)

You are right but that price was for the pro market. The current price of the consumer processor has tripled. Still we agree, it is best to know for sure.

Keep in mind that Theta is adding at least 96-24 capable DSPs hardware, not just Dirac Live.

And DTS-Neo X. The more I think about it,
consider me pleasantly shocked if you get a microphone and preamp in addition.

I have been looking at the USBPRE2. It is a really slick device with a few other uses than just as a microphone preamp. The analog to digital conversion is at 24/192. This is intriguing because I can think of a few interesting experiments. The first would be to connect the Marantz SA7 or other good SACD player to a Gen VIII series 3 via an analog connection. Next I would connect the SACD player's analog outs to the DSBPRE2 which would do an analog to digital conversion @ 24/192 which would be feed digitally to the Gen VIII and compare the results.Sure all can see where I am going? If the sample rate conversion were largely transparent, this would be a cost effective way to copy SACD. I read a review where one owner used this device to digitally record his LP collection at 24/192, which is where I got the idea for SACD as well.

Strictly as a measurement tool, you are paying for a stereo device when all you need is a mono USB microphone preamp like the one Carl recommended. But there is an added advantage if you use to convert analog stereo to digital at a high sample rate. With some outboard room correction product performing A/D conversions, at minimum, this could provide a way to compare how transparent such conversions really are.

I had forgotten about that. So there is a hardware cost on top of Dirac Live. That being said, I would imagine they will include a mic and pre, it is sort of expected at this level of expense/equipment.

Edit: Also DTS Neo X? OK, that is quite a few things, but consumers in this price bracket quite often expect all required parts to be included.

One of the considerations when I purchased the Metric Halo digital preamp was that it had an excellent mic preamp that could be modified to accept a MC cartridge signal. That way I could convert about 3K LPs to digital. Needles to say the "easier" step was making the purchase...I keep on procrastinating on the conversion part

Agree--and FYI couple of AVS folks have done that and posted in DIY forum- the difference between some of the calibrated ECM8000 and M30 while present was little and not that significant. Caveat--YMMV based on quality of cheaper/calibrated Mic-but M30 has been solid performer.

Regards,
Kishore

I would expect Theta to bundle mic/software with Dirac Upgrade (similar to what Anthem does) - but what do I know

Regards,
Kishore

Originally Posted by Roger Dressler
...
"I am also somewhat skeptical that the mic needs to cost so much as an Earthworks. The mics used by Audyssey and Sherwood (Trinnov) seem to work well enough, and that's at the extreme opposite end of the spectrum for cost and performance. Easy enough to determine: Measure the room with several candidate mics (with cal files), then see if the a) correction EQ and b) sound quality are materially affected."

And then by Kishore
...
Agree--and FYI couple of AVS folks have done that and posted in DIY forum- the difference between some of the calibrated ECM8000 and M30 while present was little and not that significant ...

Gentlemen the reason that I recommend against using cheap measurement microphones when doing room optimization is not about their frequency response. Cal files do a good job of handling that . The reason that I recommend against using cheap measurement microphones is that in my experience (and validated by some inhouse testing that Datasat did when I was there) is that cheap measurement microphones have poor and inconsistent omnidirectional qualities above 6.5K. The TM1s, M23s and M30 are all guaranteed to be truly omnidirectional out to the limits of human hearing. Every room optimization product that I am aware of assumes that the measured data that it's algorithm is operating on is from an omnidirectional source. In my experience using a cheap measurement microphone can and often does have an affect on the way that the resulting filters sound. Subjective phrases like 'lack of air' and 'digital sounding' are often used to describe the results. Altho I have my suspicions, I do not know what exactly is happening and why. But what I do know for certain is that my results are more consistent when I use better tools to get there.
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Best Regards,
Carl Huff

Hi Carl,

I have to defer to your experience. I just raise one eyebrow slightly because a) I used the Earthworks mic w/ MobilePro that came with the AP-20 installers kit, and the HF response above 15 kHz had an odd shelf from the front L/R speakers. I think you advised that I should run the measurements again with a slight adjustment of the mic's angle. If it were truly omnidirectional, why would that make any difference?

I also postulate that we are "coerced" to use such careful and maybe repeatedly tweaked mic positions (not just Dirac but Audyssey, too) to try to find the best place to pick up all the speakers spread around a single mic position (per location). I like the DEQX idea of placing the mic aimed directly at each speaker (for part of the routine anyway).

If it were possible to measure/calculate a single speaker, from all the various locations, the mic could be aimed more on axis. Yes, major drag because the user now has to move the mic 5 to 7 times as much. Not fun. But why prevent it?

"I like the DEQX idea of placing the mic aimed directly at each speaker ..."

I would bet that DEQX recommends doing that for the very reason that I described. Last I knew the DEQX mic was a rebadged Behrenger ECM8000 that becomes directional above 6.5K. I seem to remember DEQX offering a better (ie: much more expensive) microphone for those customers that wanted it. The problem with progressively pointing the microphone at every loudspeaker when measuring is literally the fact that you are moving the microphone. For room correction algorithms to work at their best you need to sample every loudspeaker once without touching the microphone. The whole point is to measure every loudspeaker repeatedly from a collection of points in space. What gets captured and operated on by the algorithm changes with every move, no matter how subtle. The best results are always realized when you properly place the microphone and then sample every channel before moving it to the next position to repeat that sequence. I recommended that you angle the microphone forward in the direction of your center channel by 15 degrees because even the most expensive measurement microphones are not perfect.
_____________
Best Regards,
Carl Huff

The reason they explain is that by taking a 1m measurement they have a good snapshot of what is coming directly from the speaker before the room alters it. This is then compared with the more usual in-seat room measurements to make the corrections. I'm not saying it's any better, but just as an example of reorienting the mic for each speaker instead of a one position measures all.


I can see that wrt setting distance and levels wrt the MLP.

To be clear, just as in the normal protocol, each speaker will be sampled by many (9+?) mic positions in the room, so the EQ will learn which errors are common (correctable) and which are not, for example.

My apologies to the thread. This is OT relative to Theta. Maybe it should move to the RS-20 thread.


You may be right. I just wonder, how the measurement from the Center speaker would alter how the Room EQ tunes the L speaker? If I change the center speaker (or remove it), does this affect how well the L speaker is tuned? What if my system has only 2 speakers, or one? I would expect it would make no difference.


That will be fine as long as the surrounds are elevated enough so they hit the mic at 15-deg, too, no?

"That will be fine as long as the surrounds are elevated enough so they hit the mic at 15-deg, too, no?"

Yep, just as in most things it's a compromise. But then best practice is always about driving down the liability of compromises.
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Best Regards,
Carl Huff

That is exactly the reason I suggest an alternative sequence in the measuring phase of the several speakers. By having the option to align the microphone optimally for each speaker, that compromise can be reduced.

Let me summarize the proposal.

Currently, when measurement is initiated, the noise steps thru each speaker. I would add an option that tells the system to sample only a specific speaker. The benefits are two-fold: optimal mic pickup, and the ability to tune a single speaker rather than recreating all the curves. (The latter benefit could be of value no matter how one prefers to aim the mic.)

Until the system has multiple mic locations representing that speaker, it would not calculate corrections, exactly as is the case now.

This could be a future feature for the Theta implementation of Dirac that would set it apart from the Datasat version, thus adding real value to the Theta product for its rather fastidious users, with zero added cost (aside from minimal NRE costs to alter the software routine).

"This could be a future feature for the Theta implementation of Dirac that would set it apart from the Datasat version, thus adding real value to the Theta product for its rather fastidious users, with zero added cost (aside from minimal NRE costs to alter the software routine)."

That's an interesting idea but I don't expect that to happen. Dirac Research has been noisy about the need to support a common and generalized software tool for all of their licensees. Most likely the same tool that Theta uses will be used to gen the filters for Dirac's own (soon to be released) PC & Apple computer runtimes. That is the case for my own DL2 and DL3 products as well.
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Best Regards,
Carl Huff

Me neither. Certainly not without any demand or other justification.


Very pragmatic. Multiple versions leads to multiple headaches.

Carl - as opposed to putting the mic directly in front of each speaker, which positions for the mic make the most sense from your end? Is there a specific recipe or is it more room dependant?

The recipe that I follow is one that I have evolved over time that was inspired by the boys at Dirac Research for best use of their product. That recipe is to take a minimum of 9 measurements (I always take at least 12) within the prime listening area. I typically work from left to right building up a matrix, never moving the microphone more than 3 feet between measurements. If there is to be a 'sweet spot' I move the microphone 1 foot between samples, effectively giving a higher priority to that region. The tip of microphone is always at listener ear level and angled 15 degrees pointing at the center channel. If there is no center channel then I point at the mid point between left and right front loudspeakers. That's it! Be consistent in your technique and use good tools for the best results.
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Best Regards,
Carl Huff

Hi Carl, thanks for sharing your experience/expertise. Who knows when Dirac will come to Theta but all these RC discussions are making me very curious.

1. I have a single row of 3 chairs in my hometheater. My question is, if I only "truly" care about sound for the sweet spot (center chair), then does limiting my mic measurement to that sweet spot result in "better" sound for the center chair?
In other words, Dirac that is optimized for center seat *versus* Dirac that is optimized for the front row of seats, which sounds better for the center seat? I expect the former?

2. Re. the mic, 15 degrees from vertical, or horizontal?

3. For what I guess is the majority of audiophiles, with little more than a Radioshack SPL and the Stereophile warble tones and pink noise CD, in your experience could Dirac be successfully set up without professional help? The reason I asked: You mentioned using Real Time Analyzer to "touch up" subwoofer gains; so for example, without RTA, the setup is not complete?
TIA

"1. I have a single row of 3 chairs in my hometheater. My question is, if I only "truly" care about sound for the sweet spot (center chair), then does limiting my mic measurement to that sweet spot result in "better" sound for the center chair?"
Usually yes, but your guests for the most part will never be aware of that slight difference unless you point it out to them.

"2. Re. the mic, 15 degrees from vertical, or horizontal?"
15 degrees down from vertical with the tip positioned to be ear level

"3. For what I guess is the majority of audiophiles, with little more than a Radioshack SPL and the Stereophile warble tones and pink noise CD, in your experience could Dirac be successfully set up without professional help? The reason I asked: You mentioned using Real Time Analyzer to "touch up" subwoofer gains; so for example, without RTA, the setup is not complete?"
I use an RTA to check my results mostly looking to be sure that the room has constant coverage and to verify my work. A Radio Shack SPL is sufficient to check the relative levels of the channels. I use a calibrated Simpson SPL but a Radio Shack or similar product will work as well. If someone is paying me good money to setup their room I make a point to show them before and after results. Screen shots of RTA software screens captured from the prime listening position is a good way to do that.

Dirac Live is easy for a novice to install. However as in all things, that novice will become better at it each time that he or she does the job! Will an experienced installer get better results the first time? Probably. Whether or not you choose to install Dirac Live yourself or hire a professional really depends on your interest, time available and money in your wallet.
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Best Regards,
Carl Huff

Carl, another question for you. I am a 90% 2 channel guy, and would consider upgrading to Theta HD Dirac level if I like the results in 2.2 mode (being able to use it 5.2 would be a bonus). However, since I have not upgrade to CBIII HD level yet, going to HD Dirac would be a big outlay and a leap of faith. I am toying with the idea of trying to pick up a used Tact 2.2xp to asses if I like that EQ does for my room/system. if I like the EQ I would resell the Tact when Theta Dirac comes out, if I don;t like it I resell the Tact and never upgrade my CBIII. So my question to you is do you think a Tact 2.2XP will give me a good indication of what Dirac will do in 2.2 mode? I will be using the same outboard dac for my mains in the Dirac and Tact setup. Anyone else that has experience with EQ, in particular in 2.2 mode is welcome to chime in as well.

I'm curious to see what Carl says about this one. A judgment call on the expected quality of the CBIII Dirac HD based on 2.2 measurements using a unit from a different mfg? A great topic for discussion and I have to admit to seeing merit in both the pro and con.

I am slow to comment subjectively on products that are not Dirac Live. I have limited experience with the TacT products. I can tell you that the science behind their products looks very good but I have little experience with their implementation of that science. As result I don't have an answer to your question.

Altho I hype and demo big systems, I too spend most of my time listening to 2 channel source material. In recent years I've become interested in 2 channel systems with synthesized center channels. Bongiorno's Trinaural box is an interesting analog product. Of late I have been exploring digital equivalents that could be included in a product containing the Dirac Live IP that targets 2, 2.2, 3 and 3.2 systems. We shall see if that effort is ever worthy enough to escape my dev lab.
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Best Regards,
Carl Huff

Thanks Carl, I am suffiently intrigued so I am scanning audiogon for a used Tact 2.2XP. If I like the results this would probably be enough "proof of concept" for me to jump on the CBIII HD Dirac bandwagon when it ships. If Dirac eventually synthesizes a center channel (something like Meridian Trifield I presume), for 2 channel sources, that would be a nice bonus.

3K LPs? Whew betcha have some good stuff! I though about you reading comments about the complexity of using Dirac Live. Did you use it to correct your room? Any other end users around that can comment? I would like the perspective from end users and comments/comparisons to other similar product if they have experience with these.

I'm betting the first person that gets a Dirac HD upgrade is going to be pretty busy answering questions on this thread. As I think about it, that's a pretty radical step for Theta - considering their cool handed approach to everything in the past. Perhaps those days are gone?

No, I still have some other issues to resolve in my system (I'm using the Datasat as a digital x-over as well; the problems have nothing to do with the Datasat and everything to do with my system and procrastination) before I'm ready to properly play with the Datasat I know a couple of other forum members that bought it are very high on it (contact JapanDave if you want some insight from a consumer setting it up). My bet is you Theta owners are really going to enjoy that upgrade.