Jeff Bagby RS180 MTM vs. Campbell Slapshot MTM

[Dougment]

Hello -

I've never built a pair of speakers but am a seasoned woodworker and ready to dive in. My research has lead me to two, well regarded MTM designs: Jeff Bagby's RS180 MTM and Curt Campbell's Slapshot MTM. They both are in the $500 range for two speakers (drivers and crossover only). I'm thinking it's a toss-up but I'd would love to hear your feedback. Here are a couple of pieces of information:

1. Here is the information that I have for JB's RS180 MTM design: https://techtalk.parts-express.com/f...180-mtm-design

2. Mr. Campbell sent me the schematics for the Slapshot MTM's but I am not going to share them because it is proprietary information. Despite what the website says, the kit offered at Rhythm Audio Design is not available.

Thanks for your any advice / feedback you may have to offer!

Doug

[a4eaudio]

Jeff's RS180 MTM use the old Dayton Audio Reference RS28A tweeter. This tweeter was discontinued 4 or 5 years ago and replaced by the RST28A. It is not a drop in replacement, so unless you have the original RS28A tweeters, it's not going to be an option for you.

[rpb]

A long while back, I had my own mtm design with the RS180, and RS28a. I liked it OK, but it had its limitations. More currently, I've used an RS270p. It's a great 10" driver. I assume the smaller RS180p is too, but I've never heard one. I've used Morel tweeters for decades, and prefer them to the RS28a. My biased opinion would be to build the slapshots even if you had parts for the other design.

[Geoff Millar]

Hi Doug

The late Mr Bagby and Curt Campbell are very well respected and regarded designers, I've never read anything but positive comments about their projects. I haven't built any of Jeff's designs, but.

The tweeter supply issue looks like it's going to determine your choice; the Morel is an expensive tweeter (at least, as an import here in Oz) but the Slapshot crossover doesn't have many parts so you will save a few $ there.

Good luck with your build, and remember to use grilles, at least on the tweeters!

Geoff

[djg]

If you can go one size down, the RS150 MTM by cjd is an excellent speaker using one of several Seas tweeters. I built 3 for my HT, very happy.

http://www.eldamar.net/audio/RS150MTM/

[djg]

Another Dayton/Seas MTM. Well known design. I had one as a center with a pair of Schumakubin towers.

http://zaphaudio.com/BAMTM.html

[djg]

I'll throw this one in because it is such a nice speaker, not MTM. Parts kit available at the local Seas dealer. I built a pair, really great sound.

http://zaphaudio.com/SR71.html

[norman bates]

I'm eager to build a slapshot.
I enjoyed the tweeter with the single capacitor recommended on its datasheet.


I don't know much about the woofer.

https://audioxpress.com/article/test-bench-dayton-audio-rs180p-8-7-reference-series-midwoofer

[Geoff Millar]

The RS180P as used in the Slapshots MTM sounds fine to us; looks great, too with the conical metal phase plug. We find the bass response very good and leave the sub off most of the time. The MTMs have no problem filling our large living room.

The 180Ps been used in other projects such as the "Supernova Minimus" in the PE Project Gallery.

https://projectgallery.parts-express.com/speaker-projects/supernova-minimus/

Geoff

[Dougment]

Thanks for everyone's input regarding MTM speakers! I'm wondering if I can get some help choosing appropriate crossover parts for the Slapshots... Mr. Campbell sent me the crossover schematic but there are so many types of inductors, resistors and capacitors that are meet the mh / ohm / uF called for and I don't know what to choose. Out of courtesy, I will not share the schematic but would it be giving away too much information to simply list the parts to get advice from the forum?

Thanks again -

Doug

[a4eaudio]

... but there are so many types of inductors, resistors and capacitors that are meet the mh / ohm / uF called for and I don't know what to choose.

You don't need to list most of the parts.

Assuming you get the parts from Parts Express:
- for all resistors get the Dayton Audio DPR10 10 watt resistors in whatever ohms are required
- for capacitors get the Dayton Audio DMPC or PMPC version or Audyn Q4 brand
- for inductors... Anything below 1.0mH will be an air core, Dayton Audio brand is fine. If the schematic specifies DCR pick the wire guage you need to match, if not specified then the cheapest (smallest guage) is probably fine. 1.5mh and above are probably laminate core inductors.

[Dougment]

Great! I'll take a run at it and post more questions if necessary. Thanks for your help!

Doug

[Geoff Millar]

If you list the parts, people would be easily able to work out the schematic.

For my build I used exactly what a4eaudio indicated, except that I used an air core inductor. I used the PMPC caps, they cost a little more than the DMPC at the time, but only a little. Buying all the bits from the same store will save on post.

At the time I couldn't solder, so my local electronics bloke used a generic circuit board and did them for me. Now I just use masonite or thin scrap wood.

Geoff