SB Acoustic 3W

[pierre666]

Hi,

I have been looking for a while for a 3 way project using SB Acoustic drivers. I wanted to have a small tower that can deliver good base extension and a great midrange for jazz and rock music. I have heard such a project in our regional DIY annual meeting but a lot of thing wheren't exactly what I wanted...
I found eactly what I wanted at Rabu Acoustic.

http://rabu-acoustics.dk/byggesaet-43/3-vejs-sb-acoustics-p1256

Since I am mostly a cabinet maker, I am not capable of designing crossover or calculating phases etc... Rabu Acoustic is a Danish vender of Sb Acoustic that has designed a 3 way using on each side:

1 x SB-Acoustics SB29RDC-C000-4
1 x SB12MNRX25-4
2 x SB17NRXC35-8

I know that this combinaison of drivers is a winner, the only things I am worried about is the crossover design. As I said, I know nothing about crossover design but if you read the writup of the design, his first music test was done with AC/DC and Megadeth....!!! I am no stranger to metal music but is it possible to evaluate a crossover design with that type of music ??

Here it is...

Please reassure me ....I am about to start this great project!!!

THX

[Wolf]

Re: SB Acoustic 3W

Since they're all on the flat-baffle, I find it unlikely that the electrical slopes should all be 12dB.

Other than that, the coil on the woofers seems a bit small.

Just a penny or two...
Wolf

[[email protected]]

Re: SB Acoustic 3W

yeah, the woofers must be crossing quite high.

[ryanbouma]

Re: SB Acoustic 3W

I think the low pass on the mid is a little odd.

Considering they measured in an anechoic chamber gives them quite a bit of credibility over us hacks, but they don't show the FR. They do show this: http://rabu-acoustics.dk/popup_image...780&height=800

Hard to read the FR off a CSD plot, but I'd say the FR looks bad based on that...

That's not a cheap speaker. I wonder if there isn't better for the money out there. Why all SB? Can you go with a larger woofer?

[pierre666]

Re: SB Acoustic 3W

That's not a cheap speaker. I wonder if there isn't better for the money out there. Why all SB?

Because I know what I am getting into...I've heard those drivers SB17 and SB12 ( except for the tweeter) and I can tell you that they really sound much more expensive then they really are...! Problem; getting a fine Xover design!

[pierre666]

Re: SB Acoustic 3W

I think this thread should have been in the Tech talk Forum...!! Sorry!:D

[[email protected]]

Re: SB Acoustic 3W

the sb29 is a fine tweeter.

[spasticteapot]

Re: SB Acoustic 3W

Don't underestimate other high-value drivers. SB Acoustics products are very good, but frequently lose to similarly priced speakers using parts from other manufacturers in DIY competitions. The SB12 has the same limitations as many cone midrange drivers, and the SB17 may distort more than larger woofers at high output.

[chrisn]

Re: SB Acoustic 3W

As I said, I know nothing about crossover design but if you read the writup of the design, his first music test was done with AC/DC and Megadeth....!!! I am no stranger to metal music but is it possible to evaluate a crossover design with that type of music ??

I use music I'm familiar with when designing/voicing a speaker, since that will be its final use. Besides, who would want a speaker that can't play metal? Those drivers look good on paper. I think it would be a good idea to sim the design first. Crossover count seems small for 12db slopes, no notches...

[pierre666]

Re: SB Acoustic 3W

Here is another one...is this one any better ?

[ryanbouma]

Re: SB Acoustic 3W

It's tought to tell Pierre. The low end bump is strange, but that might be BSC is they just used FR traces. If you're set on those drivers, try both cross overs... If they suck, mail them to me and I'll use them ;)

[pierre666]

Re: SB Acoustic 3W

so here a look at the ''almost'' finish product

[ReissM]

Re: SB Acoustic 3W

Those are absolutely stunning! You REALLY need to nail the crossover. You wouldn't want people to be disappointed in their sound after you put so much time & effort into their aesthetics, right?

OK TT guys, how can we help him smash this out of the park?

You definitely need to measure this puppy and import everything into Jeff's PCD software. I agree with WOLF... it's possible, but unlikely... that all of the electrical slopes would be 12dB/octave.

I would guess that your speakers would probably sound "ok" with either of the two crossovers shown above. BUT YOU DON'T WANT TO SETTLE FOR "OK"... you want jaw-dropping awesome! And that's going to take some testing and optimizing of the acoustic and electrical responses (simultaneously taking into consideration the acoustic phase and electrical phase response as well.)

Is there anybody out there in cyber-space that lives nearby and can measure his speakers???

After the .FRD's and .ZMA's are measured, I'm sure that several of us would offer to play with those files in PCD for him. Then he could build the PCD optimized version and run them through another round of testing to confirm the results.

[pierre666]

Re: SB Acoustic 3W

Those are absolutely stunning! You REALLY need to nail the crossover. You wouldn't want people to be disappointed in their sound after you put so much time & effort into their aesthetics, right?

OK TT guys, how can we help him smash this out of the park?

You definitely need to measure this puppy and import everything into Jeff's PCD software. I agree with WOLF... it's possible, but unlikely... that all of the electrical slopes would be 12dB/octave.

I would guess that your speakers would probably sound "ok" with either of the two crossovers shown above. BUT YOU DON'T WANT TO SETTLE FOR "OK"... you want jaw-dropping awesome! And that's going to take some testing and optimizing of the acoustic and electrical responses (simultaneously taking into consideration the acoustic phase and electrical phase response as well.)

Is there anybody out there in cyber-space that lives nearby and can measure his speakers???

After the .FRD's and .ZMA's are measured, I'm sure that several of us would offer to play with those files in PCD for him. Then he could build the PCD optimized version and run them through another round of testing to confirm the results.

I have already modified the original Xover design with someone that really knows what he is doing, in fact I am in the last phases of voicing....I have upgraded 2 caps ( C1 & C2) with Obbligato caps. For now I must say, the precision of the mids and high have dropped my jaw. Now I have to adjust the image between mid-High notes and bass....for now the bass is too powerful....
here is the schematic modified

[ReissM]

Re: SB Acoustic 3W

I have already modified the original Xover design with someone that really knows what he is doing, in fact I am in the last phases of voicing....I have upgraded 2 caps ( C1 & C2) with Obbligato caps. For now I must say, the precision of the mids and high have dropped my jaw. Now I have to adjust the image between mid-High notes and bass....for now the bass is too powerful....

That's great to hear! Are you going to post some measurements after you finalize everything? Thanks.

P.S. - Don't forget that the loudspeakers' placement in the room can significantly affect their bass response due to Boundary Augmentation. Try varying the proximity to nearby boundaries to see if the bass still seems too much.

Additionally... axial, tangential and oblique room modes can inject weird "hot spots" and "dead spots" within a room, so be aware of those "environmental" issues that can sometimes make an excellent speaker seem to perform poorly. If you can walk 3 feet over and the bass response appears to change very dramatically, you might have some room mode issues, not speaker issues. There are several ways to deal with this problem if it becomes necessary. Let us know how things go. Thanks.