RS180 or RS225 for midbass in 4-way?

[Paul W]

In an upcoming 4-way, with XOs around 180Hz to an RSS390HF and 800Hz to the RS52, I'm torn between the RS180 and RS225 for midbass.

I have measured the RS180 and am comfortable with performance up to 1k. However, the 225 may provide lower distortion on the bottom end, particularly if I need to need to lower the 180Hz XO for the RSS390. I have no experience with the 225 and have read that it may have energy storage issues beginning near 1k.

Would you choose the 180 or 225?
Thanks,
Paul

[Jed]

For a 4 way, I'd choose the RS180, for a 3 way, the RS225. The RS225 is best below 200hz, but you are going to cross around there, so why not capitalize on the RS180s midrange advantage?

[Undefinition]

For a 4 way, I'd choose the RS180, for a 3 way, the RS225. The RS225 is best below 200hz, but you are going to cross around there, so why not capitalize on the RS180s midrange advantage?

+1
Could not have said it better.

[Mazeroth]

Paul, can you elaborate more on your design? I have all the parts for my 4-way dipoles but don't see myself getting to them for at least 6 months with the unexpected (but exciting!) pregnancy and all the housework I need to accomplish before the baby comes. My plan was to go RS390HF - RS225 - RS52 - Tweeter - RS225, in dipole, with an RS52 in the rear. I decided on RS225s so I could put the RS390 in an H-frame and get lower dipole output and crossing to a pair of RS225s around 100 hz. I'm still a newb when it comes to designing speakers so I could easily be swayed to do the RS180s. Luckily, I have six of them in the basement! :B

In an upcoming 4-way, with XOs around 180Hz to an RSS390HF and 800Hz to the RS52, I'm torn between the RS180 and RS225 for midbass.

I have measured the RS180 and am comfortable with performance up to 1k. However, the 225 may provide lower distortion on the bottom end, particularly if I need to need to lower the 180Hz XO for the RSS390. I have no experience with the 225 and have read that it may have energy storage issues beginning near 1k.

Would you choose the 180 or 225?
Thanks,
Paul

[Jed]

RS225 nearfield response:

Image not available

Maybe this will help you make your choice.

[Paul W]

Mazeroth,
This design will be significantly different from your dipoles...a wide dispersion monopole with a Seas 22TAF/G tweeter above the RS52. The Mathcad worksheets posted by Dennis H (thanks Dennis!) seem to work well for establishing the transfer functions so, although they seem "parts hungry", I may try a Deuland crossover.

Jed,
Yep, the 225 is not nearly as smooth as I've seen from the 180, so I'll take your advice. :T
Paul

[Mazeroth]

RS225 nearfield response:

Image not available

Maybe this will help you make your choice.

Hmmm...I've seen measurements of the RS225 from others and have done some myself and all were much smoother than what you measured. I do respect your designs and measurements but that RS225 you posted isn't what I or others have come to see.

Here, I just cooked up some from augerpro and Mark K. Mark's measurements are from a completed deisgn, but you can probably interpolate the rest:

augerpro RS225 4 ohm



augerpro RS225 8 ohm



Mark K's design

http://www.audioheuristics.org/projects_gallery/RS225_RS28A_updates/dayton_reference_rs225.htm

[Jed]

What gate length did they use Maz? My measurement pictured above was a full gate. If I did a shorter gate it would be smoother like the ones you post- note the rolloff at 100hz vs mine extending to 50hz.

They all show the same energy storage problem of the RS225 at 1.5kish, and then again around 3-4k.

Also, mine is mounted in a sealed box- totally different set of measurement conditions.

Edit: To illustrate my point, here are 2 RS225s in parallel, in a sealed box (this included the drivers interacting in a box with eachother, standing wave influences vs IB or a large open baffle of your examples) with a 8ms gate nearfield and similar resolution settings:

Image not available

Looks a bit smoother but looks are deceiving.

Jed

[augerpro]

Those plots Maz posted are nearfield, about an 1/8" from the cone, and 400ms gate, unsmoothed. The driver is mounted on my big baffle-no enclosure. Because of the nearfield condition the response above 1khz or so is totally worthless IMO. Here is a far field at 1m and 6ms gate:



This response agrees well with the man's info and other measurements I've seen.

[Jed]

Those plots Maz posted are nearfield, about an 1/8" from the cone, and 400ms gate, unsmoothed. The driver is mounted on my big baffle-no enclosure.
.

Totally different setup than what I did: box vs no box, 1 woofer vs 2 woofers in parallel, resolution settings at different scale, etc.

However, despite the differences the energy storage issue in both our measurements is very close. Both show a dip at 1.5k, and 3-4k- which was the point I was trying to make about RS180 midrange versus RS225.

[Mark K]

Yes, there is a null around 1.6k, so you have to work around that. Having said that, the driver is very smooth up to this (too much artifact/background noise in the justMLS measurement).

I would argue that below ~1.2-1.5k, the actual midrange clarity is better for the RS225. Assuming you like to play lound.

PS. nearfield measurements can have value above 1k, but it gets a bit tricky as you have to take the predicted nulls that occur in a nearfield measurement and ferret that out from the real ones...read the original paper from the 70's in AES on the nearfield technique. Sadly, the author's name escapes me...

[Paul W]

Hi Mark,
During an earlier search, I found at least some of your measurements of the 180 and 225 and got the impression there was a significant question about whether the 225 represented current production.

Did I misunderstand or do you have what you consider to be a good apples-apples comparison?
Thanks,
Paul

[Jed]

I would argue that below ~1.2-1.5k, the actual midrange clarity is better for the RS225. Assuming you like to play lound.

.

I wouldn't cross that high with the RS225 presuming Paul wants to use a Duelund filter, like he originally proposed. The energy storage issue and ringing will not be properly attenuated with a Fc at 1.5k.

Jed