Baffle step on a tweeter

[5th element]

I assume that normally in a loudspeaker baffle step isnt required on the tweeter network because the woof and tweet share the same baffle and is sorted out with the woof.

However if you have a three way and each driver is mounted in its own enclosure, appart from the bass (as baffle step has already occured in the range it will be covering, ie all the requencies it will be called upon are already down by 6db realtive to its output at high frequencies so you just turn up the bass) do both the mid and trebble require bafflestep? Treb enclosure is about 9cm sqaure front as is the mid but at about 16cm. Therefore im guessing baffle step might be needed on the mid. But what about the trebble?

Im not 100% aufait with baffle step, but I would assume that baffle step starts at about 3700hz in a 9cm enclosure, therefore it would stand to reason if crossed at 3500 baffle step is needed to maintain the crossover slope. Is this just me making a mountain out of a molehill, ie can you compensate for this in the xover (which is being made active and i want to get everything right). Or do you just ignor it completely. Also would baffle step be absolutely neccessary on the mid? Im assuming that it would be.

Whats brought all this up is I just messsed around with the KX drivers which have been acting as a temporary xover over the past month as I get the fully active one built. This has only been working two way with the tweet and mid, with the mid (w15cy) playing mid/bass. Now I decided to alter a few things and put in a low shelf to boost 6db at about 400hz, this filled out the bass nicely, but thats not surprising as the little 5" in a sealed enclosure isnt going to fill the room, this sounded better but a bit dull. So I tried whacking up the tweeter a bit, not the answere this wasnt needed. So I added a low shelf on the tweeter at about 4000hz with again 6db and this seemed to sort it out.

Now I was listening to it quiet happily without any of these low shelfs thinking that it sounded good. If I switch out the shelfs it sounds distictly thin and weedy, but I know this to also happens if you have been listening with the bass and trebble whacked up and you turn them down.

What im saying is that have I just added some boom which sounds good because im lacking real bass but isnt natural, and because ive added bass the trebble level sounds lower so you need to boost that too. Or have I compensated for baffle step and what im listening to is how it should be. The shelved version is deffinatly more enjoyable, but I really like bass so it could just be that. When I had the bass connected up the room was boucing with bass and the sound was full, but it seemed to lack something, this wasnt a large something just a small thing said this could sound better. Could this be baffle step on the mid?

I know this probably seems to be an awful lot of half explained junk, but if yoou can get the gist of it I would like to see what you think. It would be nice if sum1 who knows about all this stuff could listen to it and say yes or no u need to do this that and the other, but I doubt that will happen.

Anyway thanks in advance Matt

[PaulHilgeman]

It all depends on the width of each enclosure, and what your crossover points are.

For the tweeter, no, you will not need any BSC. It will however effect the slope of the HP filter. So if you are currently getting the correct slope, dont mess with it.

From what it sounds like, you need to get some measuring equipent, or if you have it, get it out and use it.

What you are describing is exactly what BSC is, and it sounds like it is affecting your lower end response.

If you speaker is sitting well away from any walls, it is likely that your overall low frequency sensativity is about 6dB below that of the midwoofer. Since it is the W15cy, I would guess that this is an 86 db Sensative woofer. That means that from above the Fb, you are getting a sound output of about 80dB per watt. Thats very low. If you had a 92dB sensative tweeter, you have to pad about 12dB!!! So, what you need to do is take some measurements, and first figure out where your baffle step occours at. at 16cm, it likely starts rolling off at 750Hz or so. It rolls down to a -6dB at probably about 150Hz. And since it is a sealed box, it probably starts rolling off at 100Hz or so anyways. Then desing a filter to correct for the BSC. If passive, just an inductor that tunes the frequency, with a resistor that controls the padding. Parallel them up, and put them in series with the midwoofer. If active, I forget the circuit, but look around Linkwitz Lab.

This will help correct the baffle step by padding down the midrange to equal the bass. Now pad down your tweeter to match the midwoofer. and like i said, this is going to be a large padding.

-Paul Hilgeman

[planet10]

Baffle Step -3dB will be about 1.3k on your tweeter box and 725 Hz on the mid box.

dave

[5th element]

Ok cheers ppl, its what I had thought anyway. As its all active the sensativity of the whole lot its kinda academic due to the way you correct for the different levels of drivers. What I am doing is making the system fully active, it used to be partially active between the bass and the mid/tweet section. Now I am just gathering all the information for making it fully active (i know how to make the xovers) im just seeing what is absolutlely nescessary to include. I dont want to make my PCB's and then two weeks later find out that I should have added BSC.

At present I dont have any "good" software for measuring and designing. I have toyed with free stuff but never bought anything. What I am going to do however is find out what I need to include in the xover make it with trimpots so its fully adjustable, then tweek till it sounds good. I have a good idea of where to start from anyway. Then I am going to get SoundEasy in the next few months, which I will use to make everything "perfect". It may sound a strange way of doing things make the speaker then get the software but thats the way its going to happen.

So as far as I can tell, I need level adjust on the bass and trebble to pad to the mid, baffle step on th mid, notch filter on the mid and the filters.

This is what I had assumed anyway, it just means more opamps, which I have already anyway so its not really a problem.

Ok well cheers again and if you have any other crazy ideas dont hesistate to make them im a crazy kinda person . Anyway

Matt.