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Anyone tried the Infinity RABOS EQ system


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#1 of 24 OFFLINE   Stephen Dodds

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Posted March 21 2001 - 02:27 PM

I just picked up a pair of Infinity Prelude MTS and I was wondering if anyone has any experience with the RABOS system. Thanks Steve

#2 of 24 OFFLINE   Tony Genovese

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Posted March 22 2001 - 06:25 PM

Steve: I ordered the kit from Crutchfield for $59. It includes a CD with 23 tones from 20hz on up to 100hz and a meter with LED's that show the level. The range is from 0db to -20db (I think). The meter seems more accurate than the RS meter. In fact I don't think it needs a correction factor, at least up to 100hz. The bugaboo of the meter is that since it uses LED's, it eats batteries for lunch (and breakfast and dinner, too). Figure a 9 volt alkaline will last one calibration. If you want to redo it, get a new battery. The instructions are very clear and I think you'll find it allows you to remove the main room peak you have. I don't own Infinities but do own a parametric EQ (Symetrix) with subs (2 Hsu TN1220HO's) and the RABOS helped me zero in the subs with very little fuss. Crutchfield offers a 30 day MBG, so what have you got to lose? BTW, I'm keeping mine - and signing up for Radio Shack's battery club : )

#3 of 24 OFFLINE   Brian L

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Posted March 23 2001 - 07:38 AM

Finally, someone that has used this in comparison to the RS Meter! I posted a question about this some weeks back and got no takers. My hopes (and you may have confirmed it) is that the Infinity meter and Test Tones are designed to work together, and that the meter has appropriate averaging built in. The real PITA of the RS meter (as least the analog) is that for anything below 150-200Hz, the needle bounces around way too much (even on slow response). It makes taking room measurements an exercise in guesstimation! Its great to balance your overall speaker levels, but pretty useless (IMHO) to tweak an EQ. I read the write up at Crutchfields, and though there should be no reason that you could not use this to take room measurements and adjust an EQ; you don't really need the Infinity RABOS system to use the meter. FTR, I ended up using the demo of SpectraPLUS to adjust my Bijou, but the demo turns into a pumpkin after 30 days. It would be great to have a low cost handheld device to make adjustments in the bass region (the most critical area, IMHO). This sounds like just the ticket. Best Regards, Brian

#4 of 24 OFFLINE   Patrick Sun

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Posted March 23 2001 - 08:39 AM

This is why I got the digital version of the RS SPL meter, I don't have to deal with bouncing needle fluctuations. Posted Image

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#5 of 24 OFFLINE   Tony Genovese

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Posted March 23 2001 - 09:59 AM

But it evidently suffers from the same poor quality mic as the analog version. I was looking at a Gold-Line SPL meter for around $200. I called them and they said that it was really for broad band measurements and not tones and they could not guarantee the accuracy of the mic as they hadn't tested it for my intended use. So the Infinity filled the bill quite nicely for $60.

#6 of 24 OFFLINE   Sundar Prasad

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Posted March 23 2001 - 10:05 AM

When I run either pure sine tones or warbles (the warble tones move +/- 4 Hz around the centre frequency at a rate of 5 Hz, i.e. a 60 Hz warble will produce frequencies between 56 and 64 Hz), the RS Analog meter I use remains very steady when measurements are taken at the listening position. If there is any motion of the needle, it happens for the lower frequency (< 30 Hz) tones, and even then, the oscillation of the needle is never more than +/- 0.2 dB or so. Also, unless specific calibration curves have been provided for the Infinity SPL meter, it must be considered as accurate (or inaccurate) as the RS meter - IMO of course. Sundar

#7 of 24 OFFLINE   Tony Genovese

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Posted March 23 2001 - 01:12 PM

[quote]

Also, unless specific calibration curves have been provided for the Infinity SPL meter, it must be considered as accurate (or inaccurate) as the RS meter - IMO of course.

[quote]

Does Radio Shack provide a calibration curve? I did not see one with mine. If you read Dick Pierce's writing on rec.audio.high-end he claims to have measured dozens of RS meters and they all measure differently.

Thus I do not understand those who claim that the calibration curve that is circulating is universal to all the RS Meters out there.

Finally, I put the RABOS meter against the RS meter, and the RABOS meter adhered quite closely to the RS calibration curve, i.e. the RABOS did adhere closely to RS meter after calibration.

I therefore feel that the RABOS meter is quite accurate. Also, the RABOS meter is specifically designed to measure bass tones from 20hz to 100hz. The RS meter is essentially a broadband sound pressure meter.

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#8 of 24 OFFLINE   Jack Gilvey

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Posted March 23 2001 - 01:23 PM

[quote]

Finally, I put the RABOS meter against the RS meter, and the RABOS meter adhered quite closely to the RS calibration curve, i.e. the RABOS did adhere closely to RS meter after calibration.

[quote]
That would mean that the RABOS might be as random as Dick Pierce claims the RS meters are, since they all measure differently, no? Who's to say your RS meter is accurate after the corrections?
Or, if you assume, as you do, that the RABOS is accurate, we must assume that the RS meter w/ universal corrections is also, since it corresponded closely with the Rabos.

Anyway, that's an interesting unit, I'd like to learn more about it. I agree that all those bass tones are useful, and that it would be good to have a unit optimised for bass, if that's the case.

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#9 of 24 OFFLINE   Tony Genovese

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Posted March 23 2001 - 07:43 PM

[quote]

That would mean that the RABOS might be as random as Dick Pierce claims the RS meters are, since they all measure differently, no? Who's to say your RS meter is accurate after the corrections?

[quote]

My point exactly. But I think that since Infinity designed the RABOS as a bass equalization system that includes a parametric eq (in the speaker) and the meter and test tones to measure the bass, that it has a much greater possibility of being accurate than the RS meter which was designed to measure broadband noise and not individual tones.

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#10 of 24 OFFLINE   Jack Gilvey

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Posted March 23 2001 - 08:01 PM

I don't think I follow,Tony. If the Infinity is giving you the same readings as the corrected RS, I don't see how one can be considered more accurate (just given that evidence). (We already know that the raw RS is inaccurate, being that we have to add corrections. For the sake of argument, I'm considering the RS with corrections applied). The only "standard" against which it has been judged is the RS itself. I would think you'd have to compare it to the results from an RTA to see how close it gets. When considered as a system, as you say, I assume it should be accurate to eq those speakers, as any needed "corrections" should be accounted for. ------------------
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#11 of 24 OFFLINE   Tony Genovese

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Posted March 23 2001 - 08:14 PM

Jack: Sorry if I was unclear. My point re the RS meter was that it was not necessarily accurate even with correction. I don't know whether the RABOS is accurate, but it has a better than fighting chance because it was designed to do what I'm using it for, measure low frequency sounds. The RS meter was designed to measure broadband noise (or sounds). I do find it interesting that the correction factor works with my RS meter, so perhaps the RS meters are fine for this purpose, provided you use the correction factor.

#12 of 24 OFFLINE   Stephen Dodds

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Posted March 24 2001 - 03:27 AM

The RABOS mike and the corrected RS mike through Spectraplus give similar eadings in my tests as well. The problem with RABOS is not the measuring, but rather that the EQ system in the subs doesn't appear to do a lot. Steve

#13 of 24 OFFLINE   Jack Gilvey

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Posted March 24 2001 - 05:10 AM

OK, Tony, I see, and I agree. There is a chance, I suppose, that they are both accurate. What I mean is that it would be quite a coincidence for both units , given that they read the same, to be off by exactly the same amount at each common frequency. It may be that they're both reading pretty close to reality, close enough for the purposes of home theater, anyway. I personally would think that more likely, but that's pure conjecture.
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#14 of 24 OFFLINE   Patrick Sun

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Posted March 24 2001 - 05:22 AM

Here's a way to mod your RS SPL meter: Analog or Digital versions. The mod supposedly relieves the need for corrections down to 20Hz, but you'll need to mod the mic for anything over 10KHz or so.

I have not tried the mod...yet.


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#15 of 24 OFFLINE   Tony Genovese

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Posted March 24 2001 - 11:43 AM

I just bought an RS analogue meter. I will test it against the digital I own to see if they measure the same. Given the correction chart that is supposedly one size fits all, they should measure the same (prior to correction). Tony

#16 of 24 OFFLINE   Jack Gilvey

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Posted March 24 2001 - 02:07 PM

I'd like that comparison,Tony. I've got the digital model, and I've always just used the corrections as posted. Not really sure if that's correct,though.

This thread has some info. on the corrections and their applicability.

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#17 of 24 OFFLINE   Tony Genovese

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Posted March 24 2001 - 05:24 PM

OK, here are the measurements. Broadband pink noise: Analog 75 Digital 75 Freq Ana Dig 100 83 84 95 82.5 84 90 80.5 82 85 78.5 80 80 77 78.5 77 77 78.5 72 75 77 66 70 71.5 63 68.5 70 56 65 66.5 52 64 66 49 64 65.5 46 64.5 66 43 67 67 40 69 69 38 72.5 73 35 72 73 30 72 73 26 72 73 24 72 73.5 22 72 74 21 71.5 73.5 20 71 73 Well the two meters are within 2db of each other over most of the bass range. On broadband noise they measure pretty much the same. Not sure how useful this was, but there it is anyway. ------------------

#18 of 24 OFFLINE   Tony Genovese

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Posted March 24 2001 - 06:12 PM

Just reran the tests using the RABOS. Results as follows: Freq DB 100 84 95 84 90 82 85 80 80 79 77 79 72 78 66 75 63 75 56 73 52 71 49 71 46 73 43 75 40 76 38 77 35 77 30 77 26 78 24 79 22 79 21 79 20 79 I used the RS meter to set the initial sound pressure level and then adjusted my readings based on what the RABOS meter gave me for a deviation from the initial measurement. The RABOS reads in minus dbs not actual numbers. ------------------

#19 of 24 OFFLINE   Jack Gilvey

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Posted March 26 2001 - 06:00 AM

Thanks for the results, Tony. You do get some lift @ 20Hz, don't you? Posted Image
I think that I must get some lift extremely low in my room, as the T-Rex footsteps from "Jurassic Lunch" (Telarc's Great Fantasy and Adventure cd) shook my room with a single 1220, and they're supposed to be 12Hz signals.
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#20 of 24 OFFLINE   Jones_Rush

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Posted March 26 2001 - 10:08 AM

[quote]

...as the T-Rex footsteps from "Jurassic Lunch"... shook my room...and they're supposed to be 12Hz signals.

[quote]

I, for once, think that the T-rex is being hyped too much by the media. 12hz footsteps ?!, how come ?, It's just a tall and fat animal, that's it.
I don't think Apolo 13 launch hit so low.




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