Visaton B200 / Alpha 15a - What design??

[aquapiranha]

Hi Chaps! I have built a a set of OB's using a B200 and 2 X Alpha 15's per side, but I cannot no matter what I try get any decent amount of bass from the system! Don't get me wrong, I am not expecting subterranean earth shaking bass, just something musical, and visceral.

I am currently using the system active via a Rane AC22B X-over, and the bass drivers are wired in series (I did try them for a while in parallel, but the load seemed too great and there was hardly any bass...) and powered using a Sure 4 X 100W board ( I have tried others including a hefty hypex unit)

So, what am I asking/. well, I am hoping someone can come up with an alternative design, presumably with the B200 in OB, maybe the Alphas in another arrangement? I am not limited by WAF, just by cost, so cheap and cheerful!.

The option I have seriously considered is using the B200 alone, in an OB and going back to passive with maybe a small tripath (trends for eg.) or valve amp. If this can be done while providing at least a modicum of musical bass I will be happy.

I know that is a lot to ask, but any ideas / experiences would be very gratefully appreciated. Many, many thanks in advance, Steve.

[rjbond3rd]

Hi Aquapiranha,

If you're not getting monster bass, I would suspect a phase / wiring issue. After that, a room issue. After that, maybe the baffle is just too narrow for the bass you're expecting?

I have the same Rane xover and the B200. I'm wondering:

(a) how low do you get (have you tried test tones maybe?)

(b) what xover point are you using on the Rane?

(c) how are you going into the Rane's XLR? Does your pre have XLR out or, if RCA, are you using level/impedance matching box?

(d) Have you read this MJK article? The setup is similar (4 Alpha's, active crossover): Project 7 : Lowther Open Baffle System Design Project

[aquapiranha]

Originally Posted by rjbond3rd

Hi Aquapiranha,

If you're not getting monster bass, I would suspect a phase / wiring issue. After that, a room issue. After that, maybe the baffle is just too narrow for the bass you're expecting?

I have the same Rane xover and the B200. I'm wondering:

(a) how low do you get (have you tried test tones maybe?)

(b) what xover point are you using on the Rane?

(c) how are you going into the Rane's XLR? Does your pre have XLR out or, if RCA, are you using level/impedance matching box?

(d) Have you read this MJK article? The setup is similar (4 Alpha's, active crossover): Project 7 : Lowther Open Baffle System Design Project

Hi RJ, many thanks for the response. Out of interest, can you describe your set up in more detail?

I have not tried test tones, but suffice to say I was getting a lot lower in the same room with a Sachiko and FE206E.

I am using adapters with the Rane, and I appreciate that this means a loss of 6 db, but that is treble as well as bass.

MJK very kindly assisted me with the design, and advised me on the sizeof the baffle, I will try to find the mail.

I have read the article, but I am not very au fait with the theory to be honest.

does anyone recommend using a different set up for the bass? maybe a H frame or similar, maybe a box?

Thanks, Steve

[ra7]

You should have earth shaking bass with those woofers... well, you certainly should have bass. Check your crossovers and whether you have them configured them incorrectly.

I had a similar thing going on for a while, with a single 15A per side and it turns out I had some errors in the crossovers. Even with one per side, there is enough bass to wake the neighbors.

[aquapiranha]

Originally Posted by ra7

You should have earth shaking bass with those woofers... well, you certainly should have bass. Check your crossovers and whether you have them configured them incorrectly.

I had a similar thing going on for a while, with a single 15A per side and it turns out I had some errors in the crossovers. Even with one per side, there is enough bass to wake the neighbors.

Yes you are correct. I do not even want massive bass, just something tangible and real. I have been thinking and now I think I will look at the x-over. It is set up correctly, but I have a suspicion it might not be doing its job properly?

I need to finish my LDR so that I can run the signal directly into the bass bypassing the rane, who knows? maybe the rane is u/s?

any other ideas would be great, or anyone selling a dbx driverack pro for peanuts....?

[Vix]

Try these crossover points:

Alphas: 120 Hz 12/db oct. L-R
B200: 300 Hz 12 db/oct. L-R

Alphas better be wired in parallel. Make sure yuu try it with another, capable SS amp, as it can make big difference.

Also, For Visaton you may want to try a 0.68-1 Mh inductor with 6.8-10 Ohm/ 10-20 w resistor (try different values to suit your taste) in series with a positive lead, between a speaker and the amp.

It can be a bit painful and time consuming until you hit the right combination, but it's worth it.

[SAC]

On the multiway Systems Pictures and Descriptions thread, you can see my system on Post 1763. It is very similar to yours, and even moving the crossover up to 5khz instead of 1.2khz, reducing the treble hump, made great improvements to perceived bass.

The rising response top end of the B200 is far more sensitive than the bass from the alphas. I do not know if you have done anything about this but the system is commonly held to be unlistenable until this is dealt with, and the volume will be unbearable before the bass gets going.

As a test, if you turn up the volume with the B200 disconnected, can you get satisfactory bass that way? If so, then it is just a matter of balancing out the sensitivities of the B200s and the alphas.

Ditto to getting those alphas in parallel (4ohms) versus series (16ohms).

[ra7]

Yes, being able to turn the volume down on the b200 is important as you want to make up for the ob loss in bass. What is happening is you're trying to match the efficiency of the full range to that of the woofer down low. This means you'll need more power.

Ditto about a good ss amp.

[aquapiranha]

Thanks guys. I have tried adjusting the crossover point on the rane, as well as the gain of the treble against the bass, and this made no difference other than to dull the sound. With the gain for the b200 on 2/3, and the alphas on full, there is still hardly any bass output. I have tried changing from parallel to series and this made little difference either. I did not want to go down the route of messing about with a passive crossover, hence me using the rane.

Hmm.... I need to have a good think. I have seen people with a similar set up saying that the impact and bass they get is incredible, so there must something seriously awry here I think.

Steve

[ra7]

How much power are you outputing to the woofers? Which amps are you using?