output devices on X -X.5 and XA.5

[buzzforb]

Impossible. No way the sea would part for a poor old man and a bunch of vagrants. The Egyptian elite, on the other hand.....

[Stefanoo]

Originally Posted by 5th element

As you can appreciate B&W could easily apply smoothing to their curves to lessen the impact of this peak and if they wanted they could simply photo-shop it out, it wouldn't be the first time that manufactures have done this.

True, but I unlikely see a well respected manufacturer such as B&W doing something like this and then give their prodcts away for audiotioning and technical review and especially with their very best product.
Again this are just assumptions and it might as well be just like you said.

[5th element]

Originally Posted by Stefanoo

True, but I unlikely see a well respected manufacturer such as B&W doing something like this and then give their prodcts away for audiotioning and technical review and especially with their very best product.
Again this are just assumptions and it might as well be just like you said.

Oh I agree with you, but if you look at the white paper written for the development of the 800D you will see on page 13 in the bottom right hand corner (img 14) a measurement of the FST without a crossover and it too shares the same 5dB peak at about 3.5kHz. Yet in the measurement for the driver in the cabinet with the crossover (img 12), the peak has suddenly vanished. Where did the peak go?

Now here

B&W Group North America Service & Support - Service Manuals

You can download the service manual for the 800D where it shows you the midrange drivers crossover, it's quite simple, a 2nd order electrical filter is used for both the high and low pass. This wont combat that peak in any which way, but it's suddenly vanished. Air brushed out so it looks better in the white paper? Or perhaps this was a prototype that had a notch filter. Either way we wont know. Every measurement of the FST shows that it contains this peak and almost every third party measurement of the 800 series show that this peak hasn't been notched out. The service manual shows that the xover doesn't have a notch in it either, yet it's gone in the white paper.

[Stefanoo]

Makes sense.
Curiosity, if the midrange by B&W is one of the most linear components for these frewquency range, why would it be so bad with resonance?
B&W declares instead that the midrange was resonance free, meybe I read that wrong don't know!
Am I right or you use the same FST for your own developments?

[a.wayne]

Originally Posted by 5th element

No idea what spl the measurement was taken at as this doesn't really matter. Probably around 75-80dB, normal listening levels for that speaker.

If you say it's only accurate down to 1.2kHz then how come all measurement programs, that show you the accuracy cut off for the given gate length, say different? ARTA says this is accurate down to just below 300Hz providing I've set the gate accordingly, as does Holm. They ain't gonna lie about something which is presumably calculated mathematically.

Besides what makes you choose 1.2kHz?

You need to know or should know your reference voltage, industry standard is 2.83volts ..

The graph posted looks heavily smoothed and i can tell from the reflective trace to where it starts to smooth out that the software is fudging the results. I can also tell you are knowledgeable but lacking hands on , based on your comments and interp of your own data , Hence your previous comments about impulse and step responses...


I would suggest using less smoothing 5th ...



I spent many years , many moons ago , doing such sweeps, indoor treated, mic distance from floor 1m/2m/3m/ and i can tell you it does not match anechoic nor GP, GP open field , or pit firing up is best IMO, it was impossible to see any accuracy indoors below 1K unless we had a mic distance above 3M from the floor ...

Again if you wanted to know what JA would see, you had to duplicate their setup , before submission ...it's not going to look the same with , near field measurements, cutting , splicing and adding summations ...

Originally Posted by imix500

I spent about 9 years working with Meyer's SIM2 and SIM3 measurement systems doing repair for a Broadway rental house. The truth is you can get some funky traces depending on the environment you are measuring in. The beauty of those particular system's is you have a visual indication of where the software isn't sure of the result- for SIM it's the Coherence trace. Many other pieces of measurement software do this, but SIM always seemed to perform a bit better. Then you can adjust the measurement window to suit the environment and look at your relative phase trace to get the best result trace.

What we ended up doing to have the best chance indoors was use a bunch of acoustic absorption panels. We used Sorber panels made by ClearSonics which are commonly used for vocal and drum booths for live concerts and shows. We made a sort of portable booth surrounding the SUT with 10 feet or so of panels on the floor in front of the SUT and a couple behind the measurement mic (usually a DPA 4007).
This was in early 1900's converted railway warehouses with finished plywood floors and parallel brick walls.
We found that compared to manufacturers traces done in their own anechoic chamber, we could get very close. Certainly close enough to confirm a within spec window of +/- 3 dB.

+10


Correct, wool batons and r19 thrown around the floor does help, but why bother when you can yank the damn thing outside ..



I'm sure 5th will still hang on to his "belief's" .......

[Stefanoo]

AHAHAH!!! Woow...you guys are so knowledgable....

so my question for you wayne is: why JA was unable to match the B&W set of curves? and why does the speaker show such a coherent sound balance while looking at the curves the sound should be completely different from what you actually hear from these devices?

[a.wayne]

Sound quality of any speaker is determined by more than a flat on axis frequency response curve. Its also what kind of distortion you are sensitive to..

Myself find B&W speakers hard on the upper midrange and top end, i did not find the 801's like that , but their other modules for sure. There biggest issue with their previous versions where the small modules. Testing had shown the mid range cavity has to be pretty large to absorb reflections with out dynamic compression, our reference monitors at the time had a pretty large cavity that housed the 6 inch midrange driver .

Low and behold their revised versions (current) did have larger modules and larger drivers.

I would not read into the measurements too much , without looking at the full picture, 5th did not post up the impedance magnitude and phase , interesting to see if there were any wrinkles presentand if not for marketing most would just use paper midrange drivers , much better, very natural sounding vs Kevlar.


regards,

[5th element]

Originally Posted by a.wayne

You need to know or should know your reference voltage, industry standard is 2.83volts ..

I don't see why knowing what exact SPL or drive level you've measured your drivers frequency response at is important. If one is using a signal that isn't so quiet as to limit the signal to noise ratio, or so loud as to have compression become an issue, then it shouldn't matter. I do make all of my distortion measurements at 2.83Vrms though.

Originally Posted by a.wayne

The graph posted looks heavily smoothed and i can tell from the reflective trace to where it starts to smooth out that the software is fudging the results.

As I wrote in the previous post, there is no smoothing applied whatsoever in that measurement. That's ARTA specific unsmoothed analysis. I can show you what it looks like with smoothing if you wish, but I don't really see what the point of that would be.

Originally Posted by a.wayne

I'm sure 5th will still hang on to his "belief's" .......

Well if I am wrong, then so are a lot of other people out there and who's designs must all be inaccurate and plagued with problems due to poor measurements. They aren't, though. Maybe things have changed.

Zaph did write this on his website though regarding the topic and I think it's quite relevant.

Going off on a slight tangent, I'll mention that I've heard several industry professionals say that it is impossible to obtain accurate measurements in a home environment. This is flat out wrong, and shows the closed mindedness of some people. That's almost like me saying "I don't know how to rollerskate, therefore rollerskating is impossible." There are workarounds and methodologies that may not be known (or ever needed) by someone who has an anechoic chamber at their immediate disposal. Someday when I get some time, I'll write a page on the subject.

From my point of view I guess we will just have to agree to disagree on this.

[5th element]

Originally Posted by a.wayne

5th did not post up the impedance magnitude and phase , interesting to see if there were any wrinkles present

Wrinkle at 3.5kHz, no surprise there.



Frequency response + phase without the crossover.

I don't really see why the phase angles through the impedance are important though. I didn't make any impedance measurements of the driver myself because the entire system is active, so I have no absolute need for them.

[a.wayne]

Projecting 5th ...?

pretty Poor anology ( who is Zaph ?) I have done the test both ways , others have said the same , you on the other hand have not , yet you condemn what is being said ..

Condemnation without investigation ..?