Dayton RS180-8 & Vifa XT25, what would you do?

Mayday

Member
2004-03-02 10:43 pm
Sweden
As the title says really.
I've got a pair of Dayton RS180-8 7" and I have a pair of XT25 on the way.

What type of speakers would you build with those?

I don't mind floorstanding speakers as long as they aren't huge.

I've been trying to learn speaker design software during the day, but I would prefer not reinventing the wheel if there already are good designs with these drivers out there.

And I have spent the better part of 2 years or so getting decent at KiCad and PCB design. Unless necessary, I'd like to avoid learning another set of software's that I'll use for most likely this one project.

I have one pair of each so a dual 7" 2.5-way or similar is out.
Grateful for any and all help and advice.
 
have you looked at this Zaph|Audio. Also on that site is a discussion of the filter design for the xt25 with a scanspeak woofer for the zd5 speaker.

There is extensive discussion of the rs180 at htguide although i don't recall what threads. You might look for Jon Marsh's write up of the modula mtm and the Nat P mtm. I think the most significant issue with the rs180 is the resonant peak around 6.5k which will be audible without a steep xo slope and a tweeter that can cross over low.
 
One of our regulars is Michael Chua, who seems to have done quite a few Dayton RS-180s projects. This is the shielded version, but can't be much different:

Raven – Dayton RS-180s with Peerless XT25TG30-04 – AmpsLab

There are two versions of the XT25. The double-magnet and louder 60 is considered better than the 30.

646973d1511252578-suppose-shallow-vs-steep-argument-vifa_xt25_ringradiator-jpg


Michael will send you a schematic if you PM him. I would think the box is a moveable feast.
 

TMM

Member
2007-09-01 8:37 am
Australia
I would get an RS52AN-8 and make a 3-way because the RS180 and XT25 have distortion problems between 800Hz and 2kHz. I like both of those drivers, just not together in a 2-way.

There are two versions of the XT25. The double-magnet and louder 60 is considered better than the 30.
There are some misguided opinions about this. The sensitivity of the BG60 is higher and the Qts is lower when compared to the TG30, otherwise they are identical. When measured without correcting for the difference in sensitivity or roll-off at the low end due to difference in Q, one or the other can appear to perform better. This is not the case. Once you correct for the slight difference in sensitivity and hit the same target slope with a crossover, they perform basically identically. If I weren't following an existing crossover design, I'd just buy whichever one is cheaper.
 
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TBH, I didn't get much out of Wolfie's link to Techtalk, seeing as how I couldn't find a schematic. Maybe I need to be logged in? :eek:

But I picked up the gist of some problems with the smaller Vifa XT25G30-04 tweeter, which incidentally is very similar to the Scan R2604-832000. It struggles with a low-order crossover below 3kHz.

We have had this issue many times before. Ring-radiators don't use ferrofluid and hence often have an alarming Fs peak in resonance, here at about 500Hz and 18 ohms.

John Kreskovsky discussed this issue, but alas, "All those moments will be lost in time... like tears in rain." as Roy Batty said. And the images ARE lost. :confused:

Happily I can fix this. Notch filter design calculator - for speakers | Audio Judgement.

The series tweeter notch, which is an addition after the tweeter filter, is 100uF and 1mH and 4.7R overall. I don't know quite what Michael Chua will come up with for this combination, but am sure it will be good.

AFAIK, any cheap NP 100uF electrolytic will do. Probably 3.9R ceramic resistor and some 1mH coil. I think I'd get an air-coil for linearity, but who knows? Comes out to 500Hz, which is right.

I know these sort of threads often turn into a wish-list for everybody's ideal speaker, but really Mission creep is to be avoided. It's a two way in a box. :)
 

Mayday

Member
2004-03-02 10:43 pm
Sweden
I would get an RS52AN-8 and make a 3-way because the RS180 and XT25 have distortion problems between 800Hz and 2kHz. I like both of those drivers, just not together in a 2-way.


There are some misguided opinions about this. The sensitivity of the BG60 is higher and the Qts is lower when compared to the TG30, otherwise they are identical. When measured without correcting for the difference in sensitivity or roll-off at the low end due to difference in Q, one or the other can appear to perform better. This is not the case. Once you correct for the slight difference in sensitivity and hit the same target slope with a crossover, they perform basically identically. If I weren't following an existing crossover design, I'd just buy whichever one is cheaper.
I can't seem to find that driver from a domestic vendor.
I think they are available in the EU though.
 
I know Michael Chua, with his usual generosity, has sent the RS180s plus XT25 schematic to Mayday. All is generosity at diyaudio! :D

I can't help thinking that a MarkAudio CHN-50 makes an easier near midrange than the overly lively RS52AN-8 metal dome mid:

CHN-50 full range driver | KJF Audio

A little 1L enclosure can't be too hard if you want to creep into a 3 way and use the XT25 very high. But a three way, while simple enough for some of us, is seriously harder than a two way. Even if it's better:

646927d1511229072-suppose-shallow-vs-steep-argument-duelund-2-83-jpg
 
It's all an endlessly interesting hobby. And we are always finding more out about it.

Measuring techniques are getting better. We know have the CSD or waterfall plot derived from impulse response by the mathematical Hilbert and Hilbert-Bode transforms, which is how simulators work.

Marius Tanasescu, who did that Vifa XT25 Fs correction at 500Hz, is very good. Cumulative spectral decay explained - CSD plot using ARTA

Here he looks at a two-way with your XT25 and the SEAS CA18RNX 6" paper woofer.

As usual, the worst thing about 6" woofers is the breakup around 5kHz. But some issues at 800Hz with that peak, which I think is the edge of the cone and surround causing problems.

But what he neatly shows, is how a two way reduces the problems at 5kHz. The 2.2kHz CSD resonance on the XT25 is unexpected, but suggests that low crossover with the XT25 might sound rough.

All this is better with a three-way: SP38/13

That's an expensive mid-dome. I get interested in cheaper ways to get to the same place. You can leave your options open with a removable front panel. Not a bad way to do things. I'm rubbish at woodwork and it holds me up.
 

Mayday

Member
2004-03-02 10:43 pm
Sweden
I had a look at the parts I've got at home (got some PIO caps etc in storage).

2x Dayton RS180-8S
2x XT25 (on the way)

Caps (JFX Premium), 2 of each
68uF/250V
20uF/250V
10uF/250V

Inductors, 2 of each
1.2mH Jantzen Crosscoil
2.4mH Tritherm Intertechnik

So, apart from some filter component etc I may need...this is what I have to work with for now as the suggested midrange was €45/pc plus shipping.

I don't really care if it turns out to be a floorstanding speaker or a "bookshelf" speaker. As long as the width of the footprint isn't too wide.

I'd prefer a narrow floorstanding speaker though.

I'll likely have to have the boxes made if advanced above a carton of milk, I can solder just about anything...can't cut a straight line in wood if my life depended on it.