SPL Meter - Is this right?

[Mavicator]

Just bought my first SPL meter and I'm hoping I've done this right. The guy selling me a sub needs to know the actual sound level I will be playing at so I measured just the three front speakers with the meter. Here's what I did...

Turned on Denon's internal test tone

Set meter to 70, C weighted, Slow response.

Adjusted the three speaker levels until all three measured +5 on the meter, giving 75db overall.

Now my two mains are set to -7 and the center to -3. Does that sound right, and am I safe to turn the volume to my expected max level and give the sub guy the reading from the front panel of my recevier? Looks like I'm not going over -10 according to the receiver now, which measures 85-90db on the SPL meter. When the speakers were set to 0 on the Denon, the same audio level was more like -25 on the panel.

Thanks from a confused and clueless noob.

[J.4knee]

OK it sounds like you are using an analog meter and of the various types of analog power meters I've used your procedure seems to pass muster. Now having said that I am not familiar with your particular meter. I use a digital meter. Regarding the question your sales rep asked I think he wanted to know the level you normally listen to, so he can match a sub your listening habits. As far as using the meter to calibrate your system, yes use the test tones from your receiver and then set the levels to match all speakers to the same level if that means attenuating you mains some to accommodate efficiency variances in your speaker array then yes do so. It is always better to EQ down than up. Most HT's are calibrated to 75 db I believe that is the "THX" spec. The front panel indication of where your volume control is set really plays no bearing on this other than to remember where this is at to quickly set your system up to play a movie if you wish to listen at that SPL level you calibrated your system to. But back to your sales rep question, what you should do is play your system and monitor the SPL level you are listening at and tell him that number. But what your rep seems to want to address, is to make sure he does not sell you an under-performing sub or perhaps an overbearing one. Also let him know w what speakers you use and that should help him as well.

EDIT: Just noticed you have a REF 7 set up. You can prettty much take all the sub he can throw at you but the Klipsch RSW 15 is a good mate, as well as the various SVS subs.

Where are you at in So Cal? There is a number of us on the forum who are from So Cal.

[Mavicator]

I'm using a Radio Shack analog meter. The sales rep at SVS already recommended the PB12-Plus/2 but we (read: my wife) are having issues with the massive size of that unit. So... I asked him if the standard 12 would work. That's where he wanted me to calibrate the system and report back.

Btw, I'm in the San Fernando Valley about 25-30 miles north of LA on the 101.

Thanks so much for the reply!

[michael hurd]

Is the reading taken at the listening position? If so, then you must also account for the loss of spl due to the distance from the listening position to the speaker.

This must be factored in, and taking into account the Thx spec of 115 db at the listening position, when choosing a particular unit.

[J.4knee]

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On 8/2/2005 9:14:02 PM michael hurd wrote:

Is the reading taken at the listening position? If so, then you must also account for the loss of spl due to the distance from the listening position to the speaker.

This must be factored in, and taking into account the Thx spec of 115 db at the listening position, when choosing a particular unit.

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Thx spec of 115 db ??? I thought THX spec was calibrated to either a 75 db or 85 db reference level at the listening position depeding upon the calibration source you use?? What does the 115 db spec equate to ...transient burst headroom for the amplifier?

[Mavicator]

I didn't realize you had to calculate for listening distance. How would you do that exactly? Is there a standard formula?

[michael hurd]

Thx spec for subwoofers is 115 db at the listening position, and 105 db from each main channel.

[J.4knee]

I am not calling you out on this but what is your reference? To me 105 db is virtually unlistenable at a listening position in your average room/home, I can see 105 db peaks but not an average level. I mean that is hearing damage levels. I have always read and understood you calibrate your system to 75 db at the listening position. 105 would allow for a transient peak to be 30 db greater than the source average. But 105db calibrated level would leave you with almost no speaker capable or reproducing the transient peaks.

[dragonfyr]

I am a bit confused by this entire process.

I am not sure why you need to 'calibrate' anything at this point... And I fear that you are making this more difficult then need be...

It would seem that your only concern is that the sub be able to 'keep up' or exceed the response of the rest of your system And quite frankly, the only issue would be if the sub underperforms, as over performing is a simple adjustment of the gain!

It would seem that the simplist way to get a loose feel for this ios to look at the sensitivity ratings of the systems - assuming these are relatively accurate, this should give you a rough idea of the match of the units.

And all things being equal, personally, I would buy the a quality subwoofer with the most gain you can afford, as I do NOT think you will ever be unhappy with that!

Ask anyone! The ONE thread we don't see is the one complaining that their subwoofer is capable of too much gain!

[Mavicator]

You're confused? Try going through it with my level of knowledge! The main thing at this point is to see how LITTLE of a sub I can get away with since the one I'm looking at is big enough to use as a bench... for two people. I'd rather get the next smaller model which has a cabinet at least 60% smaller overall, but the SVS rep is concerned with not having enough sub to keep up. Since we're on the edge of the two models, he's asking for real-life numbers from the room.

Here's the data I sent him in my email a while ago, showing what the receiver's volume display says and what the SPL meter was recording at the listening position...

Low volume: -35 to -25db (65 to 75db on SPL meter

Typical volume: -20 to -25db (70 to 80 on SPL meter)

Max occasional volume: -10db (80-85db on SPL meter)

Scaring friends: -5db (85-90db on SPL meter)

[dragonfyr]

PB12-Ultra/2: 19" wide x 26.5" high x 28" deep.

PBS12-Ultra: 18" wide x 25" high x 25 deep.

PBS12-ISD: 18" wide x 21" high x 20" deep.

Personally, in trying to match sensitivities with the Reference series, I would not go below the PBS-12-Ultra.

As far as the size...I really don't know what to tell you. You may find a unit smaller, but not by much. And if your primary consideration is size, then...well, perhaps you should look at a Sunfire (based purely on size)... or perhaps one of the upright oriented tube subs, as their footprint is smaller, but they are taller. Unfortunately you are running into the physics of low frequency enclosures.

Now it is simply a matter of what tradeoff in performance you are willing to accept. And from what I can tell, all are able to reproduce ~85dB SPLs. What I don't know is whether you will be satisfied with that.

Good luck!

[michael hurd]

J4knee, I should have explained more, the THX home spec is 105 db output capability per channel, not continuous average. This is also measuring at the listening position, not 1 m from the speaker. The subwoofer spec calls for an additional 10 db, for an output capability of 115 db at the listening position.

With very efficient loudspeakers, and most average rooms, you can get by with fairly low power requirements, as the loudspeaker sensitivity drops, power requirements explode.

Edit: the 115 db spec for the LFE or .1 channel is not THX, but rather apparently a Dolby Digital spec, I am still searching for a good link.

[michael hurd]

http://www.thx.com/mod/products/chosngProduct.html

http://www.thx.com/mod/techlib/volume.html

The reason to set the volume level to 75 db is to have adequate headroom for loud passages, yet present dialog at a level that does not cause listener fatigue.

http://www.audiovideo101.com/dictionary/thx-reference.asp

[Petrol]

Klipsch RSW-15 DIMENSIONS:

19.2" (48.8cm) x 18.6" (47.2cm) x 24.5" (62.2cm)

http://www.klipsch.com/product/product.aspx?cid=371&s=specs

while my little sub is only about 2" x 14" x 15" and makes a decent side table, I could easily fit the larger RSW-15 in the same space...in my small house (if I could afford said sub, LOL)

[CAS]

Just curious why all the speakers are set in the negative range. I set my digital meter to 70 dB, my speaker levels to the factory (0), turned the master up to 70 dB on the meter, then adjusted from that point. My mains are both (-1) and my center is at (0). With your settings of (-7) and (-3), wouldn't it make sense to turn down the master, achieve 70 when at default (0) then adjust? Then you wouldn't have to turn up the master all the way up to -10 and your levels would be closer to factory default.

[Mavicator]

The test tone defaults to zero on the AVR's master volume. I thought it was best to leave it there. Is it OK to lower the volume on the test tone to calibrate? Will that not throw off the reading on the volume display during normal use? Or does it not even matter? Lots of question marks in this post!

[bertsummerkids]

The best way to calibrate the speakers is the following. Set your master volume to 0 on your receiver. Make sure you turn down the individual speaker settings because when set from the factory this is very loud sound level. Then begin your test tones and set each speaker to 75 or 85 if you use Avia. At this level your fronts will probably be at about -7 or -8. once they all match the same spl then your system is calibrated. the reason you turn your master to 0 is so that you know when you turn your volume to 0 then you are playing movies at the intended reference levels that give your speakers the best sound and balance. for example if you set up as above and play the movie at lets say -10 then the surrounds or center may sound not sound as in tune with the mains. whether you use 75 or 85 for reference depends on which test disc you use. Avia is at 85 and video essentials is at 75

hope this helps

[dragonfyr]

You folks keep referring to tones rather then pink noise.

I have no idea what frequency the tones are at, but you will probably need to adjust the measurements accordingly.

You would be better off using pink noise rather then measuring lots of tones.

Good luck...

[bertsummerkids]

the test tones that i refer to are the pink noise signals that are found on avias disc or your avr receiver

[Trey Cannon]

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On 8/3/2005 1:00:01 PM bertsummerkids wrote:

The best way to calibrate the speakers is the following. Set your master volume to 0 on your receiver. Make sure you turn down the individual speaker settings because when set from the factory this is very loud sound level. Then begin your test tones and set each speaker to 75 or 85 if you use Avia. At this level your fronts will probably be at about -7 or -8. once they all match the same spl then your system is calibrated. the reason you turn your master to 0 is so that you know when you turn your volume to 0 then you are playing movies at the intended reference levels that give your speakers the best sound and balance. for example if you set up as above and play the movie at lets say -10 then the surrounds or center may sound not sound as in tune with the mains. whether you use 75 or 85 for reference depends on which test disc you use. Avia is at 85 and video essentials is at 75

hope this helps

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This is not a bad way to do the setup...but not the way I do it...this is why.

I use a Denon as well. IF all ch levels are at 0 then my max volume setting is +18. As I change levels per ch. that max number changes. (from +24 to 0)

I think of most receivers as good units when it comes to power, BUT all of them and any amp have their limits.

IF I run my receiver at 0 on the volume then I am at the edge of clipping the amp.

I want more headroom in my amp than that.

So, what I do is set the master volume to about -25db (where I listen most of the time) then start my test tones. (which on the Denon is pink noise that is bandwidth limited)

Then I set my ch levels...my Mains (La Scala) are at +2 or so in DD 5.1 / DTS. My rear ch is set to +4 or so.

( I like to piss off the folks next door, my sub is set to +10)

The Room level I set to is 85db.

Therefore, when I am done and watching a movie. I have the master set to about -25db and my over all output is around 80-95db. The receiver has tons of headroom and never goes into or close to clipping. ( FYI: clipping is what damages most speakers)

All this is a balancing act. Just like mixing a live show.

your ch levels are input gains

you master is output gain

your looking for an over all output level of "X"

IF you run your input gains to high you clip the preamp and things sound crappy

IF you run your output gain to high you clip the amp stages and blow tweeters.

For you sub question, Look for a sub that can give you an max output of 115db or so across its bandwidth in your size of room.