20-39 PCi vs PC plus

shiu

Originally posted by Dr. Spec
It's extremely rare to get strong content at 10-12 Hz, but it does happen; Revolutions is a good recent example.

Did you mean the Matrix Revolutions? I hope the answer is yes. I have that DVD and I can't wait to hear/feel that 12 Hz sound when my PC Ultra gets here. Could you really sensel frequencies that low?

Dr. Spec

Yes, Revolutions has tons of bass in the 15-20 hz region. I recommend the stock tune first, and then possibly the 16 Hz tune, next.

You CAN feel infrasonic bass - you'll know immediately what I'm talking about when you fire it up and spin Matrix Revolutions.

The PCU will troll to 17 Hz in the stock tune, so try that first.

shiu

I hope that beast shows up on a Friday or Saturday so I can test it right away without losing sleep. How do they produce those frequencies, electronically? I thought even pipe organs only go down to 16 to 20 Hz.

By the way, I like the sound of the double bass a lot, this is where I find my PSW404 does well. What is the range of the double bass? Will the PCU do justice to the full range of this instrument? Thanks in advance!

Dr. Spec

Yes, synthesized bass - the mix engineers can do anything these days, it seems. The PCU will do justice to anything you throw at it - don't worry a bit.

shiu

My PCU arrived yesterday. I still got that room peak, just slightly lower (55 HZ) than the 60 HZ that the PSW404 was doing. I have to adjust the PEQ level to almost maximum to get rid of the 55/60 HZ peak. The SPL for 20 to 100 HZ is now between 81 & 85 dB, averaging 8 dB higher than the other speaker levels.

Even at this high level (8 dB higher than the other speakers), the bass is not any louder than that produced by the PSW404, but it sounds cleaner, and without the 404's boominess. I have only listened to Diana Krall in Paris so far, finding NEMO will be next.

Dr. Spec

"The SPL for 20 to 100 HZ is now between 81 & 85 dB"

Uhhhh.........I'd be doing back flips if I had a 20-100 Hz response of +/- 2 dB. That's incredibly flat. I guess the PEQ did its job as advertised (with even a bit of room to spare on the range). GREAT work!

Keep us posted on your impressions as you get used to the sound and experience different music and DVDs.

Doc

shiu

Could someone tell me how to post excel graphs please!

shiu

Originally posted by Dr. Spec
Keep us posted on your impressions as you get used to the sound and experience different music and DVDs.

I have been busy setting it up to get that "flat" curve. I watched NEMO briefly, very unexciting. Just started X men, 15 minutes into it, my Golden retriever (I thought they were bred as gun dogs) decided that this thing is not good to him. I can see it in his face! As for everyone else in the house, as soon as they saw it, they laughed and said "I have never seen a scratching post that big". Indeed, one of the cats tried once already. Hopefully by the time I finish watching X-men, they would have learnt to stay away. That's all for now, as soon as someone tell me how, I will post my excel graph of SPL vs frequency.

gatemplin

Nemo was very unexicting with the sub? Why? The Darla, submarine and mine field scenes are awesome. My door shakes.

To post the graph, right click the chart, copy it. Open Microsoft Paint and save it as a Jpeg, maybe resize it to make it a little smaller. Then post it using the IMG function, read the vB code help if you get stuck.

Dr. Spec

Hmmm....

What does your electronic set-up menu look like for the DVD player and the AVR?

Could be a set-up problem with a limiter or something.

gatemplin

Doc, by limiter do you mean something like dynamic range compression feature?

Dr. Spec

Yeah......I usually recommend double checking ALL of these things, even if you think they are right.

All speakers set to small.
Pre/pro xo set to 80 Hz.
Sub level to -5 in the pre/pro.
DVD player set to bitstream (i.e., DD/DTS decoding).
All dynamic range control circuits off in DVD and pre/pro.
All bass limiters off in pre/pro.
LFE channel (i.e., ".1") level set to max (i.e., unattenuated level) in pre/pro.
Low pass filter disabled at the SVS.
Phase to 0 at the SVS.
All ports open and tune switch to 20 Hz.


Many times the DRC is enabled, or the LFE channel is attenuated, or a bass limiter in enabled, or the DVD player is not bitstreaming and there is no DD or DTS. Lots of things can go wrong to make the experience "unexciting". In that size room he should easily be able to hit 115 dB if he feels like it.

shiu

Here it is:

Almost flat from 50 to 20.

Dr. Spec

Is this with RS correction factors?

shiu

No, it is the digital one part # 33-2055, I thought it does not need correction.

gatemplin

She needs correction too

shiu

Gatemplin,

I read it from somewhere before that the digital model did not need correction. I didn't doubt it at the time because with digital it would have been easy for the manufacturer to implement self correction. Either way, my graph is still not too bad, except that I would have trouble explaining the peak (after correction) at 20 Hz.

Since I do not feel that I am getting too much bass at the moment, I am going to stop playing with it for now. Its movie time.

Thank you for your help,

Shiu

gatemplin

I have used both the analog and digital and haven't noticed a difference. It is my understanding that it is not just the RS meter but also the "C" weight setting that causes the low reading in the lower frequencies. Doc knows all about this stuff, maybe he can clarify but I have never heard that the digital meter measures flat.

Dr. Spec

It needs correction. Use the standard RS correction factors.

shiu

Hello Doc,

Do you have the standard RS correction factors from 20 to 100 HZ in 5 HZ increments? The correction factors given in the SV site only covers 20,25,31.5,40,50,63,80,100,125.

Another question, when I watched Attack of the clones today, I played the THX audio test that is included in the DVD. For all 6 channel, my RS meter read 73 dB, only 2 dB lower than what I got with my calibration DVD disc. For the subwoofer channel, the meter read 61 dB, that is at least 20 dB lower than what it read when I ran the LF sweep test using the calibration disc.

The disc I used is called Home Theatre Optimizer. The sweep test goes from 120 to 20 HZ. I did not bother trying it with my receiver's test tone because I am pretty sure the test tone frequency is too high for use with the PCU. If the THX audio test included in the Star War disc is accurate, then my subwoofer level is way too low, but it is already capable of scaring the crab out of the cats and dogs, I can't imagine increasing it by 20 dB. What should I do next?

pjdami

This will get you a little closer. If you know how to interpolate you can dial in right on the frequency correction you are after.
It's close enough probably because you will have more error reading the meter.

Hz Corr (db)
100 2.000
94.4 1.860
89.1 1.728
84.1 1.603
79.4 1.500
75 1.500
70.8 1.500
66.8 1.500
63.1 1.500
59.6 1.500
56.2 1.500
53.1 1.500
50.1 1.500
47.3 1.770
44.7 2.030
42.2 2.280
39.8 2.512
37.6 2.641
35.5 2.765
33.5 2.882
31.6 2.994
29.9 3.492
28.2 4.015
26.6 4.508
25.1 4.969
23.7 5.650
22.4 6.300
21.1 6.950
20 7.500
18.8 8.700
17.8 9.700
16.8 10.700

shiu

Thanks, after applying the correction factors, I got 82.5 to 87 dB from 20 to 100 HZ, with peaks over 85 dB at 20,25,30,58,60 HZ.

Still pretty flat, can't complain.

pjdami

Congrats, that sounds really good. However, I would like to see a graph to help me visualize (if its not too much trouble). We are getting a nice collection of "real world" in room frequency response graphs in here and some people have great results and others struggle with it due to poor room acoustics.

Dr. Spec

Yeah man, post it up. Let's have a look-see.

Also any feedback on checking for a set-up problem? That sub should be kicking major **** and if its not there's a problem somewhere.

shiu

Thanks to pjdami, this is the graph plotted with the corrected data. The reading for 20 HZ is not reliable because my DVD's LF sweep test only goes down to 20 HZ. As soon as it hits 20 HZ it stops almost immediately so the meter may not have time to capture the minimum.

The curve is not as smooth as the one with the uncorrected data, but still within +-2.25 dB. I was happy with its performance in Attack of the Clones and X men. I still don't know why the THX subwoofer test tone from the Attack of the clones DVD only registered 61 dB.

Dr. Spec

Deep six the sweep and burn some tones. Paul will get you straight. The meter can't respond fast enough on the sweep. You should be getting huge amounts of room gain in that size room.

pjdami

shiu,

Many of us have used the 1/12 octave test tones from the following website. Download the mp3s, convert it to a format that your source will play, and burn a disc. Send me a pm with your email address and I can email you an excel spreadsheet that fits those tones and plots the graph for you with correction factors built in.

http://beyond_gomer.tripod.com/

Paul

shiu

I selected "fast" and hope it would be fast enough for the sweep. I'll try to download the tones and do the test again this coming weekend.

Thanks again,

Shiu

shiu

So my previous "flat" curve was resulted from the rolling average that I was getting from the LF sweep. Even at "fast" setting, the RS meter's 1 sec response time was still too slow. I got a much uglier graph (despite many hours of work) using the downloaded test tones and Paul's spreadsheet. I have not given up yet but will have to wait until Saturday to find time to work on it again. It does seem like I need a multi band PEQ to tame my room gain.

Dr. Spec

This curve looks worse than it sounds.

Your scales are giving the impression of lots of big peaks/nulls, but in truth you are +/- 3 dB (using a 77 dB average) from about 70 Hz to 30 Hz. That is very, very acceptable - when you start hitting peak/nulls in the 10 dB range, then start worrying.

Then the infamous room gain crops up and 20 Hz cruises to a nice juicy peak (don't worry about that - you'll never hear it on regular music and it will be a benefit for HT).

Alter your scales by killing the 0-15 Hz and making a 10 dB increment between numbers instead of 5 dB. You'll be amazed at how much better the curve looks.