narrow tower BSC

[tvrgeek]

I have not built towers this thin before. 6 inches. I find the baffle step to be over 8 dB. I got it beat down to a total of 2 dB. More than that I get into the crossover range. I have not had this much trouble in a long time. Is this normal for really thin towers? Any advice?

[AllenB]

It is worthy to note that baffle width makes fundamental changes to a speaker that cannot be 'fixed' with a crossover. BSC is merely a compensation aimed at the on-axis response.

That said, it should be no greater than 6dB. If you can see more than that it is likely that you are looking at multiple issues.

[fastbike1]

You might ask on TechTalk (http://techtalk.parts-express.com). Lots of narrow designs there. No one having issues w/ BSC.

[mdocod]

Perhaps if we could get a feel for the drivers and network components you have running we could help spot what is going on.

[sreten]

Hi,

Baffle step for a driver typically has a 2dB bump above the nominal
6dB level for a total effect of 8dB (for a driver that measures flat).
This is true for any driver in a baffle width near its size.

For narrow baffles the high frequency of the baffle step colours
the critical midrange more than wider boxes, it is quite normal.

rgds, sreten.

[mdocod]

Hello sreten,

Please excuse my ignorance... When you say "colours the mid range," do you mean that it changes tone, adds harmonics, or changes level?

Thanks,
Eric

[tvrgeek]

Thanks. That was what I was afraid of. 2 or 3 dB is what I usually see.
The driver is a Zaph aluminum mid/base. I think I wound up with about 1.2 mH and 8 Ohms as the best compromise. I had to push the frequency down so far it started a little dip at about 680 just to get the hump down to 1 dB. More than 8 Ohms just worked like a LP, not a BP. (7 Ohm driver you know)

It is a darn decent mid priced driver. My nephew wanted thin towers and I had not built any, so why not? Now I know why not. I used them before in 9 inch wide cabinets without too much difficulty. After I get the LP section done and see how it integrates, (2K) I'll see if I need to add a second filter. Towers this thin don't even leave me any room to round over the edges for reduced refraction.

[tvrgeek]

Wonder what Totem does?

[tuxedocivic]

Isn't there a benefit to thin towers, from moving the diffraction bump high into the passband, they near the stop band and is more easily dealt with in the xo? There is appeal to me for a narrow cab for looks, and moving that diffraction and baffle step near to and even above 1khz, where the primary inductor can whack it into place.

If going active, I'd take the wider baffle to push the lowest portion of baffle step down below the area of room influence (<200hz) and where I usually dump onto subwoofers. This absorbs some of the baffle step effects results in less SPL losses.

Baffle step colours the sound either way. It's how you deal with it.

Hmm, I should try some crazy narrow towers like Totem, might be fun.

[tvrgeek]

The lower one crosses over the Zaph the better, but, there aren't many half decent tweeters that can safely reach there. Maybe the SB. I am using the 27T metal Seas for these so 2K is about it. Maybe 1800.

I have been thinking about the old days when we had true mids that covered the entire high sensitivity range. The old 3 inchers that could be happy from 500 right to 5K. That puts the crossovers out of the critical range. I guess the monitor/sub concept killed them off. Hmmm. Might look around.

I have not given up on passive yet. Maybe a few more.