First FR with SW

[Vikash]

The response doesn't look particularly good, but I don't know how these Speaker Workshop scare stories came about. Wasn't too difficult getting it to spit out a frequency response at all (thanks Claudio!) albeit a little laborous

The measured speaker is the TB-W3871S monitor. The top end looks very unconvincing even with the notch applied (help! is this a gating issue possibly? and how do you apply the baffle step into the equation to sort that bottom end out?

All in all it's a straighter squiggle than I was expecting for a first effort.

[Vikash]

A bit more playing around with the view and the top end doesn't look too out of place all of a sudden.

Using the same scale as Zaph, and superimposing his FR a little higher up, it's actually comparable - so something's right somewhere . There seems to be alot more data in his mid and low end response, what's have I missed here?

And how do I sort that blasted bass hump. I'm still guessing that accouting for the baffle step will smooth it out?

[ShinOBIWAN]

Originally posted by Vikash
A bit more playing around with the view and the top end doesn't look too out of place all of a sudden.

Using the same scale as Zaph, and superimposing his FR a little higher up, it's actually comparable - so something's right somewhere . There seems to be alot more data in his mid and low end response, what's have I missed here?

And how do I sort that blasted bass hump. I'm still guessing that accouting for the baffle step will smooth it out?

Hi Vikash,

I had some similar problems with SW. Its great for measuring T/S specs etc. though.

I'll mail you and try to help out.

[lufbramatt]

hi
the last few days ive been playing around with SW, and id agree that it was nowhere near as hard as i had been led to believe, but ive still got to do a bit of fine tuning as my graphs still seem a little wierd- im getting a huge max impedance at the Fs of my scanspeak 8555 woofers ive been testing, although if i smooth the graph out a bit the estimated TS params are very close to the published ones. Ive been using a hastily badged together claudio negro cable loom jig, which seems to work fine, but im going to build a slightly more permanent version this weekend.

I have had a little play with the FR function using the mic and preamp kit i got from vikash- cheers it went together really well - so will be interested to hear peoples comments here.
My main problem at the mo is the high ambient noise level here in uni halls- think im going to have to stay up really late to wait for all the drunkards to fall asleep before i can do some decent testing!

[soongsc]

Originally posted by Vikash
A bit more playing around with the view and the top end doesn't look too out of place all of a sudden.

Using the same scale as Zaph, and superimposing his FR a little higher up, it's actually comparable - so something's right somewhere . There seems to be alot more data in his mid and low end response, what's have I missed here?

And how do I sort that blasted bass hump. I'm still guessing that accouting for the baffle step will smooth it out?

Looks like baffle diffraction (do not confuse with baffle step). Depending on how far the measurement was made, the low2 end might be okay. But with this kind of data, I wonder what you hear when organs play. What notch values are you using?

[Vikash]

lufbramatt, the wallin jig is defintely worth considering It's just so easy with it.

Zaph measured his response using TrueRTA which he reports didn't have gating at that time. My pulse response shows the first pulse at 4ms and the second at 6ms! So not much data to play with in the gating. I'm not sure to what extent the effects of the above are, but I'm sure there is some.

A little excerpt from from John's write-up:

The W3-871 is a little different from other smaller drivers in that it doesn't need much baffle step compensation at all due to the natural response curve. The filter is a simple 3 component notch. This notch serves two purposes, it not only reduces a small bump in the speaker's natural response, but the main baffle step hump is in the same vacinity.

Ok, so the low end rise is ok and the nearfield measuring technique doesn't show the effects of baffle step (sanity check please)? which would otherwise show a flatter low end response...

soongsc, Baffle edge diffraction refers to the rough mid/top end right? 5.75" wide box with 6.8ohm-3.3mfd-.7mh notch

Measurements were taken in my converted attic with sloped shallow wall/ceilings. Farfield measurements were taken from 1m, and spliced with nearfield at 750Hz.

[Nemophyle]

hello vikash

i think that what zaph is saying here is that this driver, due to the drooping response that we see on your graph, dont need Baffle step compensation , so if you want the expected response youd better do farfield measurements all the way ...

[soongsc]

Originally posted by Vikash
lufbramatt, the wallin jig is defintely worth considering It's just so easy with it.

Zaph measured his response using TrueRTA which he reports didn't have gating at that time. My pulse response shows the first pulse at 4ms and the second at 6ms! So not much data to play with in the gating. I'm not sure to what extent the effects of the above are, but I'm sure there is some.

A little excerpt from from John's write-up:

Ok, so the low end rise is ok and the nearfield measuring technique doesn't show the effects of baffle step (sanity check please)? which would otherwise show a flatter low end response...

soongsc, Baffle edge diffraction refers to the rough mid/top end right? 5.75" wide box with 6.8ohm-3.3mfd-.7mh notch

Measurements were taken in my converted attic with sloped shallow wall/ceilings. Farfield measurements were taken from 1m, and spliced with nearfield at 750Hz.

Not knowing what room dimensions you have, but you could try adjusting the measurement setup around 45 degrees to all walls, and let the speaker backside face the down side of the ceiling slope. This will possibly delay the first reflection a bit more. If you haven't smoothed the curve, it looks pretty clean. I'm amazed.

Yes, the two humps starting from the mid to the right. The extreme highs is possibly the driver itself.

[Vikash]

I'll move things around see if I can delay that first reflection a bit. Only the nearfield below 750Hz has been smoothed to 1/8 octave as per Claudio's webpage. The rest is as-is.

I went through John's article again and picked up things that I tended to ignore in my pre measurement days

Namely he mentions the baffle diffraction dip at ~3Khz, and a dip and peak at 6Khz and 12Khz respectively related to flush mounting. I wonder if those socket head bolts are having an effect too?

[soongsc]

I'ts probably also good to look at the manufacturers FR plot. If some of the trends match, then it's most probably the driver itself. There's also a dip at the 1KHz.