Info of my MWAF winners

[Paul K.]

I was very fortunate to have my RS duet design win the Dayton Driver Category at MWAF. This design was based on and an evolution of a design by Mark Krawiec ("markk") from 2005, and Mark revised the crossover to accommodate the current version of the RS225 and RS28F. Mark prepared a write-up on his site that includes both a description of his crossover design process and a link to the write-up I created for these speakers. After his first 6 paragraphs you will find a link to my write-up in PDF format that you can read and download. Following that are details from Mark regarding the crossover. Here's the link:
http://www.audioheuristics.org/markk_wp/?p=376

This is not a particularly costly design to build mostly because the Dayton Reference drivers are so reasonably priced. Based on normal list prices from PE as of June 23, you can buy all the drivers, all of the crossover parts, the ports and the binding posts for ~$420. If you bide your time and get the drivers on sale, you can probably reduce these costs to ~$380.

There is a dimensioned side view drawing of the cabinet in my write-up but it doesn't show that the tweeters' centers are horizontally offset 3/4" from the baffles' centers, built as mirror-image pairs. Also the outer edges of the hardwood bezel where the drivers are mounted are rounded over with a 1/2" radius.

I think you will enjoy reading Mark's write-up, and I hope between that and what I wrote, everyone's interest in this project will be satisfied.

Thanks, again, to PE for hosting MWAF
Paul

Darnit, my title should read Info ON my MWAF winners

[DIYNut42]

Thanks for sharing, and congrats on your win!

[donradick]

Great writeup! Besides your usual thorough explanation of TL design subtleties, I really, really dug into the crossover
explanation.

[Paul K.]

You're welcome and thank you.

Thanks for sharing, and congrats on your win!

[Paul K.]

Thanks. I always enjoy reading Mark's various write-ups. He has a very engaging, pleasant and often humorous writing style. My project would not have been possible without his help. It got pretty close to the deadline for getting them done in time for MWAF because of sending one of my crossovers and tweeter to him for further measurements and crossover tweaking. Living 2000+ miles apart does make it difficult to collaborate on a design/build.
Paul

Great writeup! Besides your usual thorough explanation of TL design subtleties, I really, really dug into the crossover
explanation.

[ttan98]

Hi,

Many thanks to Paul for sharing your design and Mark for sharing your x-over design and excellent write-up.

Cheers...

[fjhuerta]

That's a very interesting build, thanks for posting it! Especially because of the crossover. I wonder why certain designs sound better when they are not "flat". Even MarkK seemed not to be so sure about what was going on.

[markk]

Sorry,
Can't post now. Wife's making me listen to "dancing queen" by ABBA. Aaahh, what we do for love...

[jonpike]

AAhhhh, indeed!! See you back here when you recover...

[jonpike]

And now having had a chance to read over the posts and papers, congrats on a well thought out design, and the catagory first place, Paul and Mark!

[Paul K.]

Hmmm, not a very nice thing to imply about Mark, intentional or not. No matter how a design is voiced, there's not going to be only one correct way to do it, flat or otherwise, because of the differences in preferences between each of us. I, for one, simply do not like a forward-sounding speaker, especially a line array and most MTMs. That's probably because I listen to almost only instrumental symphonic music and expect to hear quite a bit of depth, making it sound much like a live concert in a good concert hall.
Paul

That's a very interesting build, thanks for posting it! Especially because of the crossover. I wonder why certain designs sound better when they are not "flat". Even MarkK seemed not to be so sure about what was going on.

[Paul K.]

Thanks, Jon, always good to hear from you.
Paul

And now having had a chance to read over the posts and papers, congrats on a well thought out design, and the catagory first place, Paul and Mark!

[fjhuerta]

I didn't mean any disrespect to MarkK. I was talking specifically about this paragraph, which he wrote.

I measured the FR of the crossover, as well as the distortion performance of Paul’s RS28F. Both of these measured fine. Although I can’t prove it conclusively, I suspect that the low crossover causes the tweeter power response to bloom quite a bit lower than we are used to.

Hmmm, not a very nice thing to imply about Mark, intentional or not. No matter how a design is voiced, there's not going to be only one correct way to do it, flat or otherwise, because of the differences in preferences between each of us. I, for one, simply do not like a forward-sounding speaker, especially a line array and most MTMs. That's probably because I listen to almost only instrumental symphonic music and expect to hear quite a bit of depth, making it sound much like a live concert in a good concert hall.
Paul

[Paul K.]

The reason Mark wrote that is because of my opinion that the basic sound was a bit too forward or bright for my tastes, yet Mark had designed them for a flat response which most users of the RS28F seem to use and like. Just to be sure I hadn't made any mistakes in building the crossovers or there was something different in my tweeters compared to Mark's, so I sent him one of my crossover assemblies and one tweeter. He found nothing amiss about either and ended up designing in the mild BBC dip and slight upper octave roll off, which sounds much better to my ears. I don't have the knowledge to address his comments about possible blooming from the tweeter's power response actually occurring or if it's even measurable, but I don't consider it particularly onerous that he was unable to offer a concrete reason for what I was hearing.
Paul

I didn't mean any disrespect to MarkK. I was talking specifically about this paragraph, which he wrote.

[fjhuerta]

Me neither, but it'd be interesting to know what's going on, since it's something that I've encountered in the past...

[Thezeek]

I am thinking that the specs for the old RS255-s are close enough to the new RS225 that they could be used in the same mass loaded transmission line box that you used for this project. At a quick glance, is that correct?
old- http://www.parts-express.com/pe/show...number=295-366
new- http://www.parts-express.com/pe/show...number=295-356

[Paul K.]

Probably to very likely, but the T/S values I used to model the ML-TL for the RS duet came from actual measurements from Paul Carmody. I also had two sets of measurements from Curt Campbell, which were similar to those from Paul, and one more set from markk. Plugging into the model any of these fours sets of T/S values gave very similar results. While not quite duplicates, audible differences would be small to inaudible. Please note I'm only talking about how well the RS225s-8 would work in the ML-TL, not about how well it would mate to the crossover Mark designed for the RS duet.
Paul

I am thinking that the specs for the old RS255-s are close enough to the new RS225 that they could be used in the same mass loaded transmission line box that you used for this project. At a quick glance, is that correct?
old- http://www.parts-express.com/pe/show...number=295-366
new- http://www.parts-express.com/pe/show...number=295-356

[Thezeek]

Yep, I was only wondering about how will it would work in the ML-TL. I will build it with a aluminum RS tweeter and Marks crossover design for that tweeter.

Thanks much for the input.

[Paul K.]

Thought you'd like to know that I set up the ML-TL model for the RS duet using the T/S values I used for my design, then replaced those values with the old T/S values for the RS225S-8. The differences were extremely tiny, barely visible on the system bass response graph and not even worth showing you a "before and after" set of graphs. So, you should be able to use Mark's original crossover design for the RS225S-8 and RS28A in my ML-TL cabinet with good success. In case you don't remember, though, Mark's very first design had 6 dB of BSC and a corner at 1200 Hz, but later he developed a revised version having 4 dB of BSC and a corner at 1400 Hz. The bass in his first design might be a bit too much depending on how close the cabinets are located to the walls, and the tweeter will be working a little less hard with the higher corner frequency. Both of those crossovers are shown on Mark's site.
Paul

I am thinking that the specs for the old RS255-s are close enough to the new RS225 that they could be used in the same mass loaded transmission line box that you used for this project. At a quick glance, is that correct?
old- http://www.parts-express.com/pe/show...number=295-366
new- http://www.parts-express.com/pe/show...number=295-356

[Thezeek]

Paul, thanks for your extra work and generosity. (You and Ed have helped me out in the past.)
I will use the updated crossover that Mark posted.