2 x RS180 Daytons, DC28F, or CORE + .5 woofer

[ontariomaximus]

I built a system late last summer.
Here is the gist of it:

2 x RS180 Daytons in a WWT configuration.

Approx 44 litre cab tuned to about 46hz - happy with that.

But I am not happy with the crossover, It's something I just cooked up.

What I am thinking about is the Core crossover but with the second woofer hooked up as a .5 woofer.

My question is do I duplicate the LP section of the crossover, but then add a large inductor just in front of the .5 woofer?

Any ideas would be appreciated.

[MSaturn]

Use Jeff Bagby's Passive Crossover designer.

He was a pioneer of the 'cascaded 2.5 way' design in which you simply place a second inductor in front of the second woofer in parallel with the first. It works quite well. Do a search for the software; those drivers have been extensively modelled, so you can easily simulate them.

[Chris Roemer]

I built a system late last summer.
Here is the gist of it:

2 x RS180 Daytons in a WWT configuration.

Approx 44 litre cab tuned to about 46hz - happy with that.

But I am not happy with the crossover, It's something I just cooked up.

What I am thinking about is the Core crossover but with the second woofer hooked up as a .5 woofer.

My question is do I duplicate the LP section of the crossover, but then add a large inductor just in front of the .5 woofer?

Any ideas would be appreciated.

Details of current XO?

[ontariomaximus]

Here is the CORE crossover, no cap across the 6 ohm resistor for the silk dome.

I can't remember what the current crossover, I know it's crossed over higher which revealed the rough response of the RS180 above 3kz. It's in the cabinet, but it's coming out, and wholesale changes are going to happen. The current crossover has both 7" RS180's operating up to meet the tweeter.

[JimHRB]

That CORE crossover uses a different tweeter and only one RS180. Not going to work. Perhaps someone here can help as learning to use PCD from scratch is going to be a daunting job.

[ontariomaximus]

The CORE is correct, the part that was cut off indicates C4 (across the 6 ohm) is not used for the silk dome.

Yes I know the Core has only 1 woofer and not 2. My idea to use the above crossover for 1 woofer and tweeter, the question is what do I do with the second woofer? Duplicate the low-pass portion of the above crossover for the .5 woofer, the ADD a large inductor in series with the driver to roll of at 200hz to compensate for hemispherical to spherical radiation.

[JimHRB]

The CORE is correct, the part that was cut off indicates C4 (across the 6 ohm) is not used for the silk dome.

Yes I know the Core has only 1 woofer and not 2. My idea to use the above crossover for 1 woofer and tweeter, the question is what do I do with the second woofer? Duplicate the low-pass portion of the above crossover for the .5 woofer, the ADD a large inductor in series with the driver to roll of at 200hz to compensate for hemispherical to spherical radiation.

Pretty sure the silk tweeter that can be used in the CORE is the RS28F, not the DC28F you list. Two different tweeters.

The usual 0.5 arrangement has the two midwoofers in parallel, with an additional inductor in the + line connecting the two. This results in a very different impedance compared to a single midwoofer and requires a different crossover for the midwoofers.

[Paul Carmody]

Two problems:
1. The tweeter used in the Core is the RS28, which is an entirely different tweeter than the DC28. The two are not interchangeable at all. So if you wanted to go the route of the Core, you will need to change tweeters.

2. Adding another woofer, through .5 alignment or any other, is going to double bass response. The result will sound tubby/muddy/bass-heavy/whatever you want to call it. Doing a 2.5 alignment would mean a significant change in the woofer's filter.

I wish I could be more helpful. It might be possible to simulate the crossover and get close to the Core's response.

[Chris Roemer]

Here is the CORE crossover, no cap across the 6 ohm resistor for the silk dome.

I can't remember what the current crossover, I know it's crossed over higher which revealed the rough response of the RS180 above 3kz. It's in the cabinet, but it's coming out, and wholesale changes are going to happen. The current crossover has both 7" RS180's operating up to meet the tweeter.

If you just look in there and tell me what you've got (it was only a year ago), maybe we can just add a 0.50c cap across your coil to notch out the upper garbage and away you go.

[Paul Carmody]

Just remembered something...
Roman did a 2.5-way for the RS180 + RS28. It's a simmed design, but Roman was very meticulous, so I imagine it works pretty well. That should be what you need. (Again, you can't use the DC28, though)

http://www.rjbaudio.com/RS180MTM/rs180-rs28-mtm.html

EDIT: Oh, well it appears as though Roman didn't do Jeff Bagby "cascaded 2.5-way" (that is, just with an added coil. As a result, there are some extra parts in Roman's version (in my opinion). However, no "cascaded 2.5-way" of the RS180 + RS28 exists, to my knowledge. Doesn't mean it can't be done; just means no one's done it.

[ontariomaximus]

I'll pull the crossovers out, I shutter at what I initally used. I never put a lot of thought in the xover as they weren't my main speakers. But I think the design has a lot of potential, and is worthy of the effort.

And yeah I just realized the core used RS and I have a DC.

But the schematic referenced above looks workable.

[ontariomaximus]

whoops, my memory is not what is used to be.

The drivers are actually RS128 but the 4 ohm version and they are connected in series.

So I can change tweeters, and perhaps the Core crossover as posted might be good.

[Chris Roemer]

whoops, my memory is not what is used to be.

The drivers are actually RS128 but the 4 ohm version and they are connected in series.

So I can change tweeters, and perhaps the Core crossover as posted might be good.


I've yet to hear of the RS128 (just a tiny bit bigger than the 125?), but it doesn't seem like a pair of 5-1/32" woofers would need a 1.55 cf vented box. Your box COULD work for a pair of 180-4s, but even then, it seems small to me, although your tuning seems high as well.

Anyhow, I think it's pretty hard (really - don't even know if it's possible) to do a 2.5 way with series woofers.

Are you sure you built a TMM, and not an MTM? Can you redo the baffle and make it an MTM? Why don't you get back to use after you know exactly what you've got: internal box volume, baffle dimensions, driver compliment and layout, current XO topology, port id and length, and anything else you'd like to tell us?

Chris

[ontariomaximus]

Arghh, another mistake. What I mean to say is this:

2 x RS180 speakers 4 ohm each connected in series
1 x DC28F tweeter

[Chris Roemer]

Arghh, another mistake. What I mean to say is this:

2 x RS180 speakers 4 ohm each connected in series
1 x DC28F tweeter

Try this:

3rd order high pass - 6 ohm series resistor, then 8uF series cap, then a #20 0.25mH shunt coil, last a 6uF cap to the + tweeter (-070) terminal

2nd order low pass - 2mH series (iron core) coil WITH a tiny 0.22uF pp cap in parallel with it to notch down the woofer hash, followed by an 8uF shunt cap to ground.

Like I say, I THINK you need 2 woofers in parallel to use the 2.5 topology. This XO will attenuate your upper range RS180 junk, but the XO freq. is 2.3kHz, and really would work best if you arranged your drivers in an MTM arrangement.

Chris

[ontariomaximus]

Thanks Chris,

I realized I had to abandon my 2.5 idea when I found the 2 woofers in series.

The HP crossover is for the existing tweeter and not the RS right?

Don't know if I have components on hand but I'll let you know how it turns out.

WTW ain't possible without a major cabinet redo.

What is the function of the .22uf across the 2mh?

[Chris Roemer]

Thanks Chris,

I realized I had to abandon my 2.5 idea when I found the 2 woofers in series.

The HP crossover is for the existing tweeter and not the RS right?

Don't know if I have components on hand but I'll let you know how it turns out.

WTW ain't possible without a major cabinet redo.

What is the function of the .22uf across the 2mh?

Yup, this is for your $15 "Silky", not the RS tweeter.

The RS180s, if run full range, have a metal cone "breakup" (ringing) about +8dB louder than the rest of the range around 6kHz, and again, about +10dB at 10k.

Without the small cap in parallel with the big coil, that garbage is only about -17dB @ 6k, and -24dB @ 10k. WITH that little cap, both peaks drop down to -27dB. That's a 3 to 10dB reduction in that upper end garbage for next to nothing.

Actually, I've worked the cross point down to 1.9 kHz, which can't hurt your situation.

HP, left (amp) to right (driver):
6 ohm resistor, 8uF cap, 0.35mH shunt coil to ground (this can be a #20 coil), (another) 8uF cap. Positive polarity to the tweeter.

LP: 2.2mH "P-core" coil with the small 0.22uF cap (NOT a 0.11, OR a 0.33) across it, then a 12uF cap to ground.

Good luck.

[ontariomaximus]

thanks. they won't be pushed to their limits so the lower crossover will be good.