Core 2-Way (Dayton RS180 + RS28)

Post date: Dec 24, 2010 8:03:59 AM

This is not a full write-up, however I wanted to post a few details on this recent design I did. It uses the Dayton RS180 midwoofer (shielded or unshielded, doesn't matter) and Dayton RS28 tweeters. There are two versions, one for the silk dome tweeter (RS28F) and one for the aluminum dome (RS28A). It is meant to be a sibling to the "computer" series (Amiga/TRS-80/ZX Spectrum), and was designed for the same tall floorstanding cabinet.

Cabinet plans here: standard or metric.

Here is the crossover for the aluminum-dome tweeter. The crossover for the silk-dome tweeter is exactly the same, except that you omit capacitor C4 from the tweeter circuit.

The crossover point is very low (around 1400 Hz). I did this simply because the drivers were able to, and I figured why not. The advantage of crossing the RS180 so low is that it eliminates the harsh breakup mode--for all practical purposes, anyway. Granted, with the Amiga/TRS-80, I worked very hard to squash the breakup mode, and honestly, I'm not sure it's audible there, either. However, there are some who believe that metal-cone drivers should always be crossed low, period. This design would be more their style.

The above Frequency Response shows a noticeable dip centered around 3 KHz, and this is extremely normal for a tweeter centered on an 8" wide baffle. It goes away when you listen slightly off-axis (ie: speakers pointed straight ahead, not toed-in). Take a look...

I'm very pleased with the sound. It's definitely in the same family as the other RS180 designs I've done; the advantage of the RS28 is that it has the flattest response. As for whether I prefer the RS28A or RS28F; I prefer the aluminum dome (RS28A), hands down. It's a wonderful tweeter, once you raise the top octave a bit with a mild contour filter (C4 + R1). It's super-clean and never sounds splashy or sibilant. However, this may be a matter of personal taste, and some people prefer the sound of silk-dome tweeters because they tend to sound just a bit more "airy." (Some have publicly stated that they prefer the "F" to the "A.") In that case, they should choose the slik version.

So why did I even bother with this design when there's already the amazing Modula TM? Well, let me start by saying that in no way am I trying to "outdo" that speaker--I can hardly even understand the crossover! I've heard it at DIY events, and it is very good. I'd like to think that the two designs can coexist. To my ears, the Modula sound as if they were designed with classical and other top-notch recordings in-mind, and will showcase them in full-detail. As a result, the Modula can be quite revealing of poor-quality recordings. The Core--as with most of my designs--was voiced to play well with normal, everyday recordings (Rock, Pop, etc.), which often times don't have "audiophile-grade" production values. Also, the Core is a taller, narrower speaker, where the Modula is more of a large bookshelf. Please don't think I'm trying to steal any thunder from Jon Marsh and his design.

Anyway, the speaker itself is being built by [MrkCrwly] over at the Parts Express board. I only designed the crossover. Mark has some very stylish touches he will be incorporating into the cabinet design. The build thread is still in progress, so follow along if you'd like.