DBX 260 and crossover recommendations with 16" wide Tub

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jjg · #1 Post by **jjg** » Tue Sep 25, 2007 9:20 pm

have a coupled pair of 16" wide Tuba 24's (very well built for me by Tim Ard - one of Bills listed builders) and recently picked up a DBX 260 processor. My tops are new powered RCF ART 322A's (sort of a higher end Mackie SRM 450).

Wondering if anyone has recommendations on a couple of key crossover issues with the DBX 260.

1. What are others using for the recommend crossover slope and frfequencies for low and high pass filters with the Tuba's (db slope (12-48DB) and type of crossover filter (LW, Butterworth, Bessel).

2. Recommmended delay to the tops asuming the subs are in a horizontal line with the mid/tops (i.e center clustered)?

3. Anyone have an example of RTA'd EQ settings with the tubas and these speakers?

Alan Star · #2 Post by **Alan Star** » Tue Sep 25, 2007 11:57 pm

If anyone feels I need to be picked up on this, please do so ... but in my experience, using horn loaded subs with active tops such as the rcf or mackie ... crossover low, around 65~70hz. Your top end won't go as loud but you won't get a big lump in the sound as you would if you crossed higher say 80~100hz, there is no way the tops will meet the subs there, but if you cross low, the subs are only doing the really low stuff and will sound more balanced. Otherwise if you cross higher eq so the subs will meet the tops... and/or build some horn loaded top boxes to go with your subs

I'm probably not too qualified to say but I have been using a similsr set up myself.

Apparently below 80hz, up to 20ms of delay is unoticible so you don't even need to delay your tops, some people may argue with that tho I tend to agree.

Crossover slopes i'm not sure about and would be interested to hear also.

LelandCrooks · #3 Post by **LelandCrooks** » Wed Sep 26, 2007 5:38 am

Got a response chart for your RCF's ? Pretty tough call without hearing it or seeing some specs.

Alan Star · #4 Post by **Alan Star** » Wed Sep 26, 2007 5:56 am

have got a bit of time on my hands just now ... here is response chart for the art 322a... taken from pdf download off the rcf site

and for multiples of the 16" version of t24, not sure which drivers you have so ...

and

hmmm, looking at the charts, seems the rcf doesnt go low enough to cross over at less than 80hz i'm guessing maybe to cross at 100 hz and to use eq on the subs to bring down the freq to match the rcf's ?

bgavin · #5 Post by **bgavin** » Wed Sep 26, 2007 11:03 am

I have not seen that T24/BP102/16" chart before, and cannot find it in my plans or the SPL section.

Alan, where did you find this? There appears to be a big difference between S2010 and BP102 response.

Tim A · #6 Post by **Tim A** » Wed Sep 26, 2007 11:44 am

Hey...I know you!

Since you picked up those subs I finally bought myself a real crossover. I have had a whole lot of luck in the 115-120Hz range.

In looking at the chart of your new tops (FOR SHAME!

) it looks like it's fairly flat right in that range and running about 99dB or so. The sub is flattening out there too, being louder though at around 106dB.

To me that's a good thing. It happens that 100dB with a pair of those cabs is right smack in the middle of it's response. It will let you pull the sub back some from 70Hz up and boost it below those frequencies. Seems like a good match.

Bruce: Charts are from page 21 of the plans. There's a whole mess of them after the cut sheets.

bgavin · #7 Post by **bgavin** » Wed Sep 26, 2007 12:36 pm

Doh!

The two charts show the significant difference betwee the two drivers. The BP102 is a MUCH larger (acoustically) driver than is the S2010. The dip in the BP102 box is smoothed out by the larger 24" box.

The downside is that puts the T24-II right back into the full size, squat Tuba thing again. Although it doesn't go down as low, S2010 looks more friendly to T24-II.

[ edit ]

It would be VERY interesting to see the MCM 55-2421 in T24-II at 16" or so....

jjg · #8 Post by **jjg** » Thu Sep 27, 2007 1:36 pm

Hey Tim - Good to hear from you. The subs use the BP102 driver.

If I hear everyone - let me suggest the following and see if you all agree or want to comment. Like to know if anyone has experienec with the different types of crossover filters and recommended slopes (LW, Bessel and Butterworth).

My thoughts:

High Pass 40HZ - using 24 db crossover filter (anyone have a preference between LW or Butterworth slopes)?

Low Pass 90-100HZ using 18 or 24db? LW filter to cross over to the RCF's.

Should I boost the EQ (perhaps via a PEQ on the DBX 260 between 40 and 60Hz to get the output to 100DB and lower from 70 - 100Hz to get down to 100Hz?

Also will not worry about delay.

Alan Star · #9 Post by **Alan Star** » Thu Sep 27, 2007 1:39 pm

bgavin wrote:I have not seen that T24/BP102/16" chart before, and cannot find it in my plans or the SPL section.

Alan, where did you find this?

yes, is in the spl section

Tim A · #10 Post by **Tim A** » Thu Sep 27, 2007 2:03 pm

jjg wrote: High Pass 40HZ - using 24 db crossover filter (anyone have a preference between LW or Butterworth slopes)?

40 is safe, but I wouldn't think 35 would be a problem with those subs at their rated power. Maybe someone else will chime in differently. No comment on the slope, I use the one in my crossover.....

jjg wrote:Low Pass 90-100HZ using 18 or 24db? LW filter to cross over to the RCF's.

I'd go higher. Your tops are dropping like a rock at 80, and the sub is just stretching out. Take advantage of the added dB on the sub and take some of the strain off your tops at the same time.

jjg wrote:Should I boost the EQ (perhaps via a PEQ on the DBX 260 between 40 and 60Hz to get the output to 100DB and lower from 70 - 100Hz to get down to 100Hz?

Find the center point and boost some/cut some.

jjg wrote:Also will not worry about delay.

I've not had to delay mine yet. Play with it when you set up. If it sounds better with some delay, leave it. When it comes right down to it it's all about your ear.

jjg · #11 Post by **jjg** » Wed Dec 19, 2007 8:33 am

Hey all:

Been playing with the settings above and am not getting the output I want from the subs. Going to try and move up the crossover (Low Pass) from 100 to 110-120.

Also curious if anyone else is using the Tuba 24's (either 16" or 24") with a DBX drive rack and has found the right mix of crossover settings and boost/cut points to get more from their subs. Thanks

JG

jjg · #12 Post by **jjg** » Wed Dec 19, 2007 8:34 am

By the way, I use a Crown CE 2000 to drive the subs in Stereo mode (400 watts/side at 8 ohms). Have tried it brideged as well.

Tim A · #13 Post by **Tim A** » Wed Dec 19, 2007 8:40 am

Bear in mind those are small subs John. It's possible you simply need a second set. Have you tried them with the coupler plate? As I said before, I've been using mine with no problems, crossed around 120Hz. I actually cross them slightly higher when using them with my DR200's, about 125.

Wed Dec 19, 2007 8:56 am

Tim Ard wrote:Bear in mind those are small subs John. It's possible you simply need a second set. .

+1. In terms of both power and physical size a general rule of thumb is that subs must be two to four times the tops. A pair of 16" T24s would be just borderline with those tops. To fully match them four would be much better. That would give you equal top/bottom sensitivity all the way down to 35Hz.

Mark Coward · #15 Post by **Mark Coward** » Wed Dec 19, 2007 10:04 am

Tim Ard wrote: I'd go higher. Your tops are dropping like a rock at 80, and the sub is just stretching out. Take advantage of the added dB on the sub and take some of the strain off your tops at the same time.

In this case I think the tops need to handle as much as they can, I wouldn't go over 100hz.

I'm wondering if the drivers have been broken in? Many sound much better afterwards. Also you can try raising the HPF up to 50hz or so, to maximize what those two subs can do.

One more thing, if you're testing in a small room that can have a negative effect especially on the sub frequencies.