Measuring Some Vintage Speakers

[bconline]

Here's a comparison of the Sonus Faber Concertino with the larger and more modern Focal Chorus 806V.

 

[bconline]

I also had some time to improve my measuring technique:

• Measured outside, on concrete driveway. Unfortunately, it was breezy. So the noise floor was high.
• Calibrated the soundcard.
• Soundcard direct to power amp. No preamp.
• 1 meter distance, 1 meter height, tweeter axis.
• Solid sand-filled stand.
• Lower level (~75db) full range
• Higher level (~85db) starting at 50hz, to avoid overdriving the small woofer
• 25 millisecond gate
• 1/12 octave smoothing

 

[bconline]

Horizontal polar response at 0, 10, 20, 30, and 40 degrees. Graphed with 6 millisecond gate. Shown from 200hz up.

 

[TheBatsEar]

Very cool lines, my dude.
Also very cool Sonus Fabers.

 

[dagfinn]

I also had some time to improve my measuring technique:

• Measured outside, on concrete driveway. Unfortunately, it was breezy. So the noise floor was high.
• Calibrated the soundcard.
• Soundcard direct to power amp. No preamp.
• 1 meter distance, 1 meter height, tweeter axis.
• Solid sand-filled stand.
• Lower level (~75db) full range
• Higher level (~85db) starting at 50hz, to avoid overdriving the small woofer
• 25 millisecond gate
• 1/12 octave smoothing

View attachment 366580 View attachment 366579
View attachment 366578

Looks like you're making progress . Did you remeasure any of the initial speakers to compare vs indoors results?

 

[bconline]

Looks like you're making progress . Did you remeasure any of the initial speakers to compare vs indoors results?

Yes, I remeasured the Focal 806V outside at the same level that I measured it inside. Frankly, I was disappointed that the outside measurement seems just as lumpy as the inside one. Here's inside (purple) v.s. outside (green) with no gating:

Here they are with a 25 millisecond gate:

Here they are with a 6 millisecond gate:

 

[DanTheMan]

Raising them off the ground further will give you much nicer graphs, but in truth they look pretty darn good outdoors. I don't remember if you have much room in your garage, but if your garage is cleaned out in the middle and you put the speakers on a 5ft stand, you'd be in good shape. Nonetheless those outdoor measurements will really teach you about SBIR problems.

 

[DanTheMan]

I decided to fix these Bose 201 series IV up a little bit further. I bought an Infinity car dome midrange for a very good deal. sort of assuming Infinity would build a great crossover to start with and mocked it up in a cardboard box with the car tweeters I had placed in the Bose. After fiddling with the crossover a bit, I was able to go from "complete disaster", to a very nice summing. However, the handoff is still audible and I think it's because of the discontinuity in radiation pattern:

I honestly can't imagine a situation where the stock crossover would work well.

In any case, I didn't have the parts on hand to make a 3-way work so I went back to the 2-way and eventually got to this (with on hand parts from the daze of my youth:

Those 4 measurements are covering about 60 degrees across the front on one side. The room is left in and the grill is in place. This is easily the best I've heard this speaker and even though its measurements aren't great, it manages to sound pretty reasonable. I may build a little notch filter in this later to knock down the 1.5kHzregion, but beyond that, this is a vast improvement over the original for not a lot of outlay. I'm sure it could be easily bettered for that matter. When Amir EQs these great speakers he gets to measure, he's being ultra picky. Make no mistake about that. Bose might still be in the home speaker making business had they just spent a little extra (money) on these (and several of their designs). If I can do this with a multimeter, measuring microphone and REW, imagine how easy it would be for a company using circuit modeling. I'd have to buy a $30 audio interface to make that happen and a couple resistors, but I'm content with these for the time being. I do have more perfect speakers, but these will be nice for the second system in the man cave.