SBAcoustics SB17NBAC35-4 and SB17NBAC35-8 measurements!

[gornir]

Hi Göran,
My measured response curve is very choppy below 1000 hz while yours is smooth. Can you post your frd file so I can compare them directly please, especially below 500hz?


I've seen only a few people who have actually used this speaker comment on this forum and they generally say they are very happy with them so does anyone have any suggestions why I am having trouble in the spoken voice range? I'd very much appreciate anyone who has used this in a 2-way system chime in here.

Hi,

I can't say I understand your measurements.

All cross-over designs starts with having high quality measurements of the drivers in the actual loudspeaker enclosure. These should be measured in an anechoich environment (gated measurement) of the individual drivers as well as measurements of them both for determine the drivers relative acoustic center offset. These measurements should be done both at on-axis as well as off-axis. You also need proper impedance measurements of the drivers in the enclosure.

In order to do these measurements you need a high quality mic with a calibration file as well as a high quality calibrated sound card together with good software to do the job.

Doing a gated measurement in a normal room, you can expect to have a valid frequency response down to 250-300Hz for a 1m measurement and down to 350-400Hz for a 2m measurement if the loudspeaker is placed properly in the room in relation to the measurement mic.

When you have all the necessary measurements, you can start the cross-over design with the proper simulation software. On line calculators are not one of these. They can at most, give you a rough estimate in order to start a cross-over simulation in more advanced software.

Your measurements doesn’t seem to be a gated measurement, instead it looks like your in room response and the jagged response you see in the lower frequencies is the contribution of the room and the speaker placement in the room.

The real issue you have is the cross-over design. It doesn’t do the job for you. A single in room response on-axis doesn’t tell the whole story of your issues, but both the mid-woofer and the tweeter x-over needs a rework.

To fully master the technique of designing cross-over takes years of study and testing and building different designs. I really hope you don’t get offended by this, but it seems like you are trying run before you have learned to walk.

My advice to you is to start with learning the measurement techniques and get some good equipment and software for the job. Then it would also be good for learning purposes, to buy and build a proven loudspeaker kit and analyze it by doing measurements and cross-over simulations to learn how things interacts.

The SB17NBAC35-4 mid-woofer is a really nice driver and it measures very good, especially compared to other hard cone drivers.

Personally, I prefer the sound of the NRX drivers, but that´s a matter of taste and is not a technical one.

Cheers,

/Göran

 

[Tropic]

Yep, I think you're right in that I put the cart before the horse, tried to run before crawling and bit off more than I can chew .

I'm away for a while, but when I get back, I'll see if I can run a 1m open air, in-speaker response test for the woofer and tweeter. I thought the curtains would eliminate most reflections but it looks like the floor and ceiling could be coming into play. If the response looks good, I'll have another go at the crossover and see what I can do to eliminate the ceiling and floor reflections in my theatre and also use ARC to eliminate the rest.

Thanks for the advice,
Rohan