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[Nicolas Lowman]

I have a friend who purchased an older model several years ago because it was being closed out for like five or six hundred bucks. I think it still lives in his workbox, I don't think it gets used very much. It was a cool toy for that price. For many of us engineers we buy the tools that we use out of our own pockets and I personally have seen a lot more interesting things to put four grand towards.

Nicolas

[chris fletchall]

We have used the sp395 for about 8 months now and love it. But our primary use for it is home theater installs.
We have used it on our live rig but with a dbx in the rack ... its kinda hard to get off my butt and dig out the sencore when I can just click on the mouse to look at the dbx.

Good unit though.

[Shane Ervin]

Hi Bennett,

Sorry to take so long to cruise to this part of the forum and see the thread.

We at Integral DX Engineering had been looking for a device (or system of devices) that would do the following, as required by the ASTM E336 & E1007 measurement & reporting procedures (pertaining to condo and office sound isolation testing):

• IEC 1260 1/3 octave filters
• 30 second Leq, after the filters
• plenty of mic positions before being forced to offload the data to a laptop
• suitable for field use
• interface with a TYPE 1 measurement mic

When Sencore released a firmware upgrade around 2007, the SP495 became, in one stroke, a candidate solution - and the least expensive one capable of meeting these requirements, so we bought one, then another a few months later.

As to your comments about price for function, we tend to agree; it's just that we didn't find anything else out there for less than double the price that met those bullet requirements I've listed above, so we were glad to find it.  Not even Larson Davis offerings would compete at double the price, two years afterwards.

In a moment, I'll describe using the FFT to ring out wedge monitors, but first, while I'm on the ASTM E336 sound isolation testing topic, I'll add this:

If anyone is interested in doing the 30 sec Leq measurement after the RTA filters, with the aim of offering ASTM compliant test services, beware that the Sencore manual steers you wrong (unless they've updated it pursuant to my teleconf with an ex-employee of theirs).  In post-processing, you need to be able average the post-filter 30 s Leq SPL's.  The STC screen only works on a single mic position scenario - which doesn't cut it without a rotary boom, leastways.  Also, reverb measurements in 1/3 octaves are required for some scoring metrics (e.g., Normalized Noise Isolation Class).  Still, a quick'n'dirty, single mic, un-normalized Transmission Loss measurement can be obtained with the STC screen functions.

Here's what page 72 (page 77 by the pdf page ctr) says:

Quote:

Transmission Loss is used to measure the amount of sound isolation that a partition provides. Typically, a noise source is placed on one side of the partition, and the room noise level is measured in 1/3 octave bands, sometimes at more than one point. Then, the measuring device is moved to the other side of the partition (presumably in another room) and the same measurement is taken. Then, the transmission loss (TL) at each 1/3 octave bands is computed, and a formula is applied to derive a numeric number representing the relative noise reduction of the partition. The idea is that this number can be used to effectively compute the amount of reduction in sound level that a partition (wall) will provide in actual use. There are several ways of measuring transmission loss. One key issue is whether or not the measurement is being done under laboratory conditions, with carefully controlled room reverb time and control of sound leaking around the partition, or whether the measurements are being taken in the field under minimal control characteristics. Several standards apply here, including ASTM 90, which talks about how to measure the transmission loss data, ASTM 413 (or ISO 717-1), to define a laboratory measurement, and ASTM 336, which takes the lab measurement and applies it to field work. The SP495 calculates laboratory values including STC, RW, and OITC. STC (Sound Transmission Class) is the ASTM (US) measurement, RW is based on the European standard, and OITC (Outdoor-Indoor Transmission Class) is based on an A-weighting curve, and is considered by some to be more modern.

Here's what you should do instead, for each stationary mic postion, if you're doing an ASTM E336 / E1007 type measurement:

• Use the RTA screen, not the STC screen (go figure)
• Set the average time to "AVG" - NOT 30 s (again, go figure)
• Set up for 1/3 octave RTA mode
• set up for "FLAT" freq wtg
• set the auto-gain to "M" for manual, and adjust the pre-amp for no clipping when the pink noise is playing in the Source condo/office.
• store settings using the UTILITY screen (because when shut off and back on, you'll want this as a default state)

Next, each time, before beginning a 30 s Leq measurement:

• "Pause" the RTA (if it had been in "Play")
• Clear the averaging buffer by this technique: scroll cursor over to the freq wtg parameter, adjust it off "Flat" and back again to "Flat" (makes no diff if you choose "A", or anything else, but this action empties the buffer, and gives you an honest to goodness ZERO to start your Leq averaging period).

Scroll on over to "Play" and at the end of your 30 s averaging period, "Pause" the RTA.

The height of each filter band's yellow marker is indeed a legit 30 s Leq measurement, post an IEC 1260 third octave filter.

Save to a memory location, or use a connected laptop and/or dump to a Terralink spreadsheet.  A macro is advisable here, too, to increment the memory pointer prior to the "Store" action; otherwise you risk writing over a memory location holding data from an earlier mic position.

We use the Sencore MACRO feature for most of these steps - including the actual 30 s "Play" -to- "Pause" interval.

Finally, post process the filtered SPL's by arithmetically averaging (convert to pressure, then average the pressures, not the decibel values, then convert the answer back to SPL) - within each 1/3 octave band - across the multiple mic positions to obtain the average SPL's for each 1/3 octave in the source condo.  Repeat for the victim condo.  Then compute the
NIC - Noise Isolation Class

Reverb RT60's in the victim condo are required for:
NNIC - Normalized Noise Isolation Class
FIIC - Field Impact Isolation Class

Anyway, for ringing out wedges, life is a lot easier:  Use the FFT on 1 or 3 second time averaging and use the cursor to read off what freq should be notched in your DSP crossover, or cut with a graphic EQ.  I've made 25 year-old bi-amp wedges really work well with a BSS Mini-Drive, and the Klarks left flat.

(Edit: Added pic of RTA screen with settings as described (1/3 oct; Avg; Flat)

[Shane Ervin]

More pics.

[Shane Ervin]

The main menu of the SP495.

[Shane Ervin]

Clicking the jog/shuttle wheel on "Acoustics" brings you here, where you can select the RTA function.

[Shane Ervin]

Here's the FFT screen.

I've used the jog/shuttle control to move the cursor to the FREQ field; then clicked on it (changing that field's display to a yellow font against a purple background, as shown).

At this point, further spinning action on the jog/shuttle control moves the thin blue vertical line in the FFT display left or right.  The peak at 752 Hz is shown.

To ring out wedges:

• served by a graph, but no parametrics, I'd likely use 1/3 oct resolution;
• crossed-over with a DSP, or otherwise having parametric notches available, I would set FFT resolution to 1/30th Oct to see an appropriate notch filter frequency.

Again, the overall point here is that it's way more expensive than a Smaart license and a laptop.  But as others have said in their posts, there will be cases, like that of the firm for whom I work, where it fits for some circumstantial reason.

(Edit: typo)