Next project MTM RS225 + RS28a

[Jed]

Hello,

I've been lurking on the pages for awhile now and saw that the new RS28a tweeter is available. I like Jon's 2-way with the RS225 + Hales tweeter but would like to try something easier to build like a convential box version or MTM using the RS28a. My question is will this design be developed soon, or are there box schematics available so I can start building - then implement the developed X-overs later?

Currently I'm working on a 2 way with low crossover point of 1300HZ using eton ER4 tweeter and 8-472 woofer from a published German Magazine called Hobby-Hifi. After I'm finished I want to see if I can build a "budget" dayton design that rivals/ beats a professionally designed kit using hi-end drivers like the etons.

So what do you all have on hand for the future?

[Mark K]

Hi Jed

I don't think Jon has any plans. But I do. Unfortunately, I'm even busier than Jon. (oh yea!). Here's the box.

Image not available

It's a sealed box design. Q of ~.7-.75. It's not up the pooh bah's alley, but, hey, you've got to make some compromises. And, if the ultimate in room curve is good-that's all that matters.

I'm going to try to make some measurements in the next 2 weeks and go from there.

[Jed]

I know what you mean about being busy-- however I'm not in much of a rush considering my eton 2 way isn't done. I'm now intriqued with the new low cost hi-performance drivers offerred by Dayton. How do you plan on using the RS225s/RS28s (X-over type etc) and in what size box? 125liter? Ported?

My single 8-472 eton setup has a 4" diameter port in a 93liter box- so a dual 8 " RS225 MTM in a 125 liter box wouldn't be too much bigger.

[JohnL]

Hello Jed, I'm curious about that Hobby Hi-Fi Design. I really love the sound of the AMT drivers, but I don't know if I'd run the ER-4 that low. I posted the distortion plots of the ER4 below, decide for yourself. I have a pair that I'm probably going to end up crossing to some 7s or 5½s because I don't think I can make them sound good with an 8. Could you post a crossover diagram, I'm interested to see what they are doing?

[JonMarsh]

I know what you mean about being busy-- however I'm not in much of a rush considering my eton 2 way isn't done. I'm now intriqued with the new low cost hi-performance drivers offerred by Dayton. How do you plan on using the RS225s/RS28s (X-over type etc) and in what size box? 125liter? Ported?

My single 8-472 eton setup has a 4" diameter port in a 93liter box- so a dual 8 " RS225 MTM in a 125 liter box wouldn't be too much bigger.

That would result in some prett nice output from dual RS225's- not unlike the dual M8a MTM's that have been built.

To make a two way with the RS225, the only practical approach (IMO) is a steep slope crossover down fairly low- I use a cauer-elliptic design which mimics an LR-8 but doesn't have the same phase shift or group delay- the group delay is more like an LR4.

Look at the M8ta design that' on here- that's a fairly radical design in the case of the seas version, which crosses close to 1 kHz. You could probably get away with the Hales version of the crossover as long as the LCR zoble for the tweeter is update- if that's of interest, once I have measured data of production parts (they're on the way), then I could update that. Wouldn't be hard to do an MTM variant if you're interested, especially since you're not in a hurry... almost NOTHING gets done in a hurry around here, most of us are just too busy juggling day jobs and personal lives.

BTW, I just thing Mark K's baby RS225 is cute as a button! Very curious to see how that one works out...

~Jon

[Jed]

Hello Jed, I'm curious about that Hobby Hi-Fi Design. I really love the sound of the AMT drivers, but I don't know if I'd run the ER-4 that low. I posted the distortion plots of the ER4 below, decide for yourself. I have a pair that I'm probably going to end up crossing to some 7s or 5½s because I don't think I can make them sound good with an 8. Could you post a crossover diagram, I'm interested to see what they are doing?

Hi JohnL,

I tried to attach the image to this message but ran into problems. Here is a link I just found. http://www.dynamik-akustik.de/hh/E-Motion/index.html
The crossover for the eton 2 way is as follows:

For the woofer 8-472 the inductor in parallel is 3.9mh r< .4 ohm and capacitor in series is 22uf. To take care of the cone breakup of the woofer there is a series filter RCL with values R22ohm, C6.8uf, L8.2 (R 1.0-3.0 ohms). This RCL is placed after the 3.9mh inductor ( circuit parallelled to the series cap (22uf)). The woofer is connected in positive phase and the tweeter is hooked up to negative phase. The tweeter has Resistor 2.2 ohm in parallel to cut output level then C15uf in parallel and L0.68 mh in series. Filter on the tweeter RCL from positive to negative (independent circuit) is value R8.2, C47uf, L1.0mh. Feel free to email me and I can give you a diagram if my babbling above doesn't make sense.

[Mark K]

Well, I should pay more attention sometimes.

I was doing some preliminary modeling in lspCAD 6 with a Cauer filter for my two way. Wow! Pretty slick. It didn't occur to me until I was running the sims that you don't need a notch. Well, that makes it simpler than the usual 4LR. Pretty slick.

Hopefully I can get out this weekend and do some more definitive measurements.

[JonMarsh]

You do that, Mark. I think you'll like why this has become my near standard approach for 2 ways needing low crossover frequencies (uh, which ones don't?)

Thinking about an article regarding the details of it, still doing some background research. The problem with doing that, is it's too much like what I do for my day job! I've written a couple of AES papers before, but they WERE for my day job.

The RS28'a have arrived- still interested in QC'ing a few to check parameters, or do you have enough on the way already for that task?

BTW, did a special conference presentation for a headquarters guy today, so he didn't have to come over (also put the presentation together); that coms with a little bonus that will net me after taxes my Praxis setup. Wooo Hoooo!

~Jon

[Jed]

That would result in some prett nice output from dual RS225's- not unlike the dual M8a MTM's that have been built.


Look at the M8ta design that' on here- that's a fairly radical design in the case of the seas version, which crosses close to 1 kHz. You could probably get away with the Hales version of the crossover as long as the LCR zoble for the tweeter is update- if that's of interest, once I have measured data of production parts (they're on the way), then I could update that. Wouldn't be hard to do an MTM variant if you're interested, especially since you're not in a hurry... almost NOTHING gets done in a hurry around here, most of us are just too busy juggling day jobs and personal lives.


~Jon

Jon,

I've been following the old thread for the M8ta design and would consider doing a design based on the components, but building that box is beyond the hours I have available- let alone my current woodworking abilities. I noticed that your design also takes into consideration many variables like driver spacing, slanted baffle, etc. just to name a few. My question for this particular design is if I were to use the crossover schematic you supplied for the M8ta, but changed the driver spacing so that the RS225 woofer is closer to the tweeter with no slanted baffle, would it negate the design altogether in terms of crossover point, phasing, frequency response, etc?

If that is the case, then perhaps I could do a simple box but keep the driver spacing in tact and the proper baffle slant of your design?
Jed

[JonMarsh]

It would be easy to "tweak" the design the slight amount necessary to get the phase response complementary for a vertical baffle- the crososver characteristics, as well as LspCAD's flexiblity makes that pretty easy. Next question for you is are you more intersted in MT or MTM, and if MT, are you thinking in terms of a simliar height, width, and depth, but just a more conventional/rational/easy to build cabinet? In the case of a normal bafffle, I'd do a BDS analysis and probably come up with a mirror image concept similar to the M8 boockshelf, but scaled to the height and listening window issues of the floor tower. I'd like to have measured data on that rough baffle size for the RS28a, but that's the only missing ingredient for proceeding.

Use the search engine to see more about the original bookshelf design with M8a and XT25, which was featured in a three part artlicle series in the fall of 2003 AudioXpress magazine.

~Jon

~Jon

[cjd]

you don't need a notch.

Tis a beautiful thing is it not?

I have found two things I dislike in a filter, and I have absolutely no idea why. But I dislike notch filters, and I dislike parallel resistors in an L-pad. The latter always seems to kill the sound *really* fast. The former, I really can't describe. Having not used them myself makes this harder to quantify I think. It's a lot more parts lying around to experiment with a circuit that uses a notch vs. not.

C

[Jed]

It would be easy to "tweak" the design the slight amount necessary to get the phase response complementary for a vertical baffle- the crososver characteristics, as well as LspCAD's flexiblity makes that pretty easy. Next question for you is are you more intersted in MT or MTM, and if MT, are you thinking in terms of a simliar height, width, and depth, but just a more conventional/rational/easy to build cabinet? In the case of a normal bafffle, I'd do a BDS analysis and probably come up with a mirror image concept similar to the M8 boockshelf, but scaled to the height and listening window issues of the floor tower. I'd like to have measured data on that rough baffle size for the RS28a, but that's the only missing ingredient for proceeding.

Use the search engine to see more about the original bookshelf design with M8a and XT25, which was featured in a three part artlicle series in the fall of 2003 AudioXpress magazine.

~Jon

~Jon

Jon,

First off, thank you for your responses to my questions. It has been a long time since I've been this excited about audio. I've built several odd shaped speakers, but never mastered the crossovers. The results were mediocre at best. Resently I have turned to professionally designed crossovers for my speaker building needs, but obviously there are some limitations to creativity. The design I'm about to complete is fairly unconventional (or so I thought until I stumbled upon your posts at the madisound board guiding others to this forum). It has a low crossover point using Eton ER4 and 8" 8-472 woofer, as I mentioned in a post above. I'm not sure how it will sound but this leads me to your questions- summarized as the reason to create a new speaker and potential configuration of the RS225s and RS28a after researching other setups that have been build already. I've read hundreds of your posts as well as others and I'm most intrigued with dual woofer setups with your custom filters. I've seen the post about the new Peerless drivers as well- again, this is interesting, especially for a price much lower than the eton drivers.

My goals are to create a speaker that sounds better than a professionally designed setup, such as the eton ER4/8-472 (Hobby HIFI) setup at a fraction of the cost. This eton setup cost around $300 for each tweeter and $200 for each woofer alone! The crossovers were about $150 each- this not including wood, ports and dampening materials. Very expensive indeed- worth it?- I want to find out.

Build a narrowish setup that fits into a variety of locations in my smallish house- without the need for a subwoofer (8 inchers should fit nicely!)

Build a box that is challenging to build but not overly complex (in my view) like the M8ta.

Improve the power handling and bass extension of a simple single 8" woofer by making the design MMT or MTM with bass reflex port.

I like the look of a slanted baffle, I think I should try one. However, I will not be able to recreate the Avalon style beveled edges.



I think I'm getting closer- what do you all think? Does anyone have drawings of a design that might work for my above goals? I've seen the M8a MTMs with XT25 tweeter etc. They seem a bit wide, but maybe its just the pics.

[JonMarsh]

Well, no one has tried to do something fully optimized to your criteria, but that's just probably because it's DIY, and everyone has their own preferences and situation to deal with!

Tibor did a sealed MTM (the first in a series of MTM's in various cabinet sizes) which is pretty compact, fairly narrow, too. He went sealed because his plan was to use his TEMPEST sub all along, and making the "mains" compact was import, especially from his spouse's viewpoint. Dual drivers lowers the distortion while allowing a little more impact and power handling.





I could well imagine scaling this up in height and depth a bit; target would be 120-140 liters of net enclosure volume, downward firing 4" port, with the enclosure on spikes like the M8ta. Similar front panel layout. Vertical dispersion is pretty good with this speaker, especially because of the low crossover, so having the tweeter a little above seated ear level shouldn't be a problem.

The RS28A has almost the same impedance curve, similar resonance and efficiency as the original Vifa XT, so it's for all practical purposes a drop in. If you're interested in going this way, I'd probably like to offer to use measured data from the RS28A and tweak the zobels slightly and re-check the crossover design in LspCAD 6, but it would probably be minor changes- the version you've seen posted on the Klone Audio site would be accurate for cost estimation. The only other point in crossover design is that if you say, "OK, I'm going to use an X wide baffle", If it was significantly different from the original M8a or MTM design in width, I'd want to revisit the baffle step compensation in the LF crossover. There are ways I could figure out the changes from modeling, but banging together a quick box would be the "safest" approach. I'm expecting to buy Praxis in May, so I'll be revisiting some measurements for correlation purposes, anyway (I use CLIOWIN Standard right now).

What's your target for width? BTW, these are 12" wide, the same as the original bookshelf version in the AudioXpress article series.

~Jon

[Jed]

Target for width would be around 11". However, if scaling up to make the speakers taller, I would say 12" would be ok. Visually a taller speaker would slim them down some. I would also trim the edges at a 45 degree angle to make them appear slimmer. Drivers = Dual RS225 and RS28a tweeter. Configuration is still undecided MMT or MTM?

I like the idea of the 4" down firing port and slanted front baffle. The rear portion of the box can be 90 degrees (vertical) to make the box appear less deep. However to get the right box volume- that might be a problem in terms of size! Might have to go back to the MT idea.

I read your thread on the M8ta speaker again - it appears that even though there is just one woofer, they have very good power handling because of the Xmax of the RS225. Since my purpose here is for hifi only, not HT- would you recommend an MT design vs MTM? The more I think about a 135 liter box and moving it around, the more the modified M8ta design in a more conventional box appears to be the way to go. Ultimately, in your experience, how much performance is to be gained with the added volume and additional woofer? Do you have drawings with measured dimensions for the M8ta (RS225 version)?

[JonMarsh]

A full size ported MTM with these drivers is not small, as you're starting to see....

The M8a and RS225 versions are the same size and use the same tuning- T/S parameters are quite compatible, it's just that the RS225 has a notch breakup mode around 1.6 kHz, and takes more care to make work. We tuned these to ~ 24 Hz. Slight taper to the response profile, which in room sounds quite deep and controlled, as the boundary load provides about 6 dB of lift below 50 Hz with correct placment.

I've got a modifed crossover worked out for it and the RS28a-4 tweeter- I'll try to find some time tomorrow to post it on the M8ta thread; crossover frequency of 1100Hz.

The MTM version has been popular for those wanting close to reference levels on HT, with or without a sub. Obvously, there's more output capability, or the distortion is lower at more modest levels. However, for a two way, the M8ta really is pretty nice; can shake stuff in the room on low bass, though not at levels above 100-106 dB for a pair. Still, that's not trivial...If you were going to use a sub, then I'd recommend a smaller sealed alignment, say, about 38 liters heavily stuffed per driver. One could do a MMT or MTM in that configuration.

~Jon

[Jed]

A full size ported MTM with these drivers is not small, as you're starting to see....


I've got a modifed crossover worked out for it and the RS28a-4 tweeter- I'll try to find some time tomorrow to post it on the M8ta thread; crossover frequency of 1100Hz.

~Jon

If I went with a dual woofer sealed box (Q.5-.6) setup with the RS225s, what kind of bass extention am I looking at versus a good down firing port setup? Some say quality of bass is improved with sealed setup because of transient characteristics and better control of the woofer. I've also read comments by you stating that often times MTMs are not preferred because they are poorly designed or crossed over too high with low sloped crossovers. Would the properly designed MMT be preferred over a MTM with your crossover? Just a few questions-

Also, when you do add more to the M8ta thread, do you have a drawing with measurements. I have the CAD drawing to study, but not driver spacing, bracing distance etc. Thanks!

Jed

[cjd]

A properly ported box can control the woofer better than a sealed alignment, within a certain realm. There are so many variables.

An MTM would be less suited to a slanted baffle - you have big time alignment issues across the pair of woofers. A TMM with a change in the slant would be better suited. But for a ported alignment, it's not entirely small - take a peek at this thread going for a pair of 3-ways with the RS225/RS150/RS28A (or 27TDFC) for some ideas on box tuning ideas.

FWIW, a ideal sealed alignment with the RS225 (say, 75-80L - depends some on the crossover components and total network impedance) will get you an F3 of near 45Hz - in room it's probably comfortably flat to here. So unless you listen to symphonies with organ music (which I do) or other music with heavy content below 30Hz, this may be everything you need. If you really need the 15Hz extension an organ calls for, it's not happening at any volume level with RS225's anyhow.

C

[JonMarsh]

If I went with a dual woofer sealed box (Q.5-.6) setup with the RS225s, what kind of bass extention am I looking at versus a good down firing port setup? Some say quality of bass is improved with sealed setup because of transient characteristics and better control of the woofer. I've also read comments by you stating that often times MTMs are not preferred because they are poorly designed or crossed over too high with low sloped crossovers. Would the properly designed MMT be preferred over a MTM with your crossover? Just a few questions-

Also, when you do add more to the M8ta thread, do you have a drawing with measurements. I have the CAD drawing to study, but not driver spacing, bracing distance etc. Thanks!

Jed

I have a group of PDF's addressing that, it's not feasible to post, per se, but if you can provide an email address that will accept moderate size attachments, I can mail them to you. Really, though, if you're building a more conventional box, that's soemthing you can plan out- just keep in mind a 12" baffle width (for BSC comp in existing crossover). The height of the M8tas is ~ 40". For an MTM tower, I'd take that up a bit higher- something close to the Arvo size, around 48-50".

~Jon

[Mark K]

It's getting there

This is a preliminary graph of my 2 way LspCAD model. Still a lot of work, but so far, so good.

Image not available

remind me to resize the graph!

[JonMarsh]

Looking pretty nice, Mark. :T I think you've got the hang of it! Dr. K, watch out!

How do you like working with LspCAD6? I went back to 5 to look at someone's files for them last week, and was surprised at how much I'd forgotten since November!

I wonder how similar your network is to my recently tweaked up M8ta Rsi? (all Dayton version). In this one, you don't have to compensate for acoustic center offset, due to the baffle design, as you would for the conventional enclosure.






I'm probably going to go ahead and finalize it with this design, even though I've been toying with waiting for the Peerless midwoofers.

~Jon

[Mark K]

Mine looks alot like yours. I cheated and pulled out the RLC on the tweeter. This is still just prelim. I did some outdoor measurements with about 7ms of meaningful data. (~5 or 6 feet off the ground. My 9 foot stand was a bit unstable.)

These are done with the mic at the same point for both. Usually I measure and model for one target point in space. Less prone to error.

I also did measurements at 39" exactly on each driver's axis, so I can get some meaningful off axis sims. I've not tried it this way, so we'll see how that comes out. More room for error, but a bit more flexible.

BTW, the praxis chirp is great outdoors. Much more LF information in the signal, so pretty reliable measurements, even in the wind. MLS was much more likely to get wind induced LF errors.

I still want a nine foot stand! (steel pipe in concrete?)

[cjd]

9foot will want tethers. A ring halfway up with tension lines to the tip and the mounting in the ground... Or just tethers from the top out to various points (really simple). If you want high strength line that will disappear, check out the Kevlar line used for high power kites (just do NOT leave it out where kids/animals may trip - it can cut, badly!)

250lb test is about as big as a single cat5 wire. Should do what you want.

Mark: I'm intrigued by the circuit to deal with the top end dip. Looking forward to when you share.

C

[Mark K]

Mark: I'm intrigued by the circuit to deal with the top end dip. Looking forward to when you share.

C

It's just a simple shelving circuit. The attenuating resistor is shunted by a cap. It doesn't really fix the dip but it does mitigate it.

[cjd]

It's just a simple shelving circuit. The attenuating resistor is shunted by a cap. It doesn't really fix the dip but it does mitigate it.

Yes, but how does it *sound*? I guess I should have been clear that this was what interested me.

C

[Jed]

Looking pretty nice, Mark. :T I think you've got the hang of it! Dr. K, watch out!


I'm probably going to go ahead and finalize it with this design, even though I've been toying with waiting for the Peerless midwoofers.

~Jon

Have you considered a version of the M8TA with a SEAS W22 woofer & RS28a-4 tweeter? Or are there the same energy storage issues like the RS225, if using the seas woofer in order to accept the additional cost- yet increase the benefit of a low crossover point and lower distortion? In other posts you mentioned the new Peerless should split the difference of cost vs lowest distortion versus the SEAS and RS225- but perhaps not in the M8TA application?

[Mark K]

Have you considered a version of the M8TA with a SEAS W22 woofer & RS28a-4 tweeter? Or are there the same energy storage issues like the RS225, if using the seas woofer in order to accept the additional cost- yet increase the benefit of a low crossover point and lower distortion? In other posts you mentioned the new Peerless should split the difference of cost vs lowest distortion versus the SEAS and RS225- but perhaps not in the M8TA application?

The problem with the W22 is that it isn't that good in the bass department. Performance below 80 isn't nearly as good as the RS225. For a 3 way, the W22 would be hard to beat. As a two way, there are better choices.

[JonMarsh]

What Mark said.... W22 is the best 8" midrange out their- at this time - though it will do best, too, staying arond 1200 and below.

Two way systems are tough... ultimately you have to make a choice about what portion of the spectrum you want to optimize for- it's hard to have it all, though I think the RS225/R28A combo will come as close as any.

[TacoD]

The problem with the W22 is that it isn't that good in the bass department. Performance below 80 isn't nearly as good as the RS225. For a 3 way, the W22 would be hard to beat. As a two way, there are better choices.

I think the performance in the treble department is much better than the lost in the bass. In some way those magnesium cones sound more realistic. I agree with Jon, it's a matter of taste .

[tktran]

I think the performance in the treble department is much better than the lost in the bass. In some way those magnesium cones sound more realistic. I agree with Jon, it's a matter of taste .

It's the tweeter that will be playing almost all treble, since both W22 and RS225 will need a a low crossover point, ~1Khz-1.3KHz (~C6-E6)

But with an 8" driver and relatively wide baffle, most people would expect some balls in the bass department.

In a 2 way, I'd ebay the W22, and buy a handful of RS225...
:-)

[Jed]

I think the performance in the treble department is much better than the lost in the bass. In some way those magnesium cones sound more realistic. I agree with Jon, it's a matter of taste .

Hi TacoD,

I read some of your old posts and you mentioned you worked on an eton 7-372 w/ heatpipe and ER4 2.5 way. I happen to have a few 7-372s laying around and might consider a 2-way using them mated up to a Dayton RS28a tweeter. Any suggestions for box volume and crossover topography? Is the Dayton a plug in for the ER4? I've seen Etona IV crossover, but it is kinda high (2.5k) and was hoping for something lower. Any thoughts?

Jed

[TacoD]

Because of the baffle step compensation by the second woofer (the 0.5 in 2.5 way), a true 2way application will be lean in the bass department. Also the FR and impedance curves of the ER-4 differ from the Dayton tweeter. Therefore plug and play is unfortunate not an option. I'll dig up the XO-design applied on the eton and modify the values to get a bafflestepped (-~4dB) 8th order LR response at ~1100 Hz. Then you can fit Jon's Dayton tweet XO on top. Most probable you can get away with it, because the low XO point and steep XO the topology is quite insensitive for driverspacing and phase anomalies.

In an ideal word you measure the drivers in your own enclosure and hand over the measured response data, but I'm aware that not everyone has a measurement rig.

[TacoD]

It's the tweeter that will be playing almost all treble, since both W22 and RS225 will need a a low crossover point, ~1Khz-1.3KHz (~C6-E6)

But with an 8" driver and relatively wide baffle, most people would expect some balls in the bass department.

In a 2 way, I'd ebay the W22, and buy a handful of RS225...
:-)

The past couple of years I've build a lot of speakers with a dozen of different drivers, Dayton is still on the todo list, until I've heard the Dayton I'll keep saying that Excel is the better choice. Maybe you get 98 % of the performance of the Excel with the Dayton for a lot less money, frankly I don't know yet. One thing I do know is that even the alu cone of Seas doesn't sound the same as the Excel.

[Jed]

I'll dig up the XO-design applied on the eton and modify the values to get a bafflestepped (-~4dB) 8th order LR response at ~1100 Hz. Then you can fit Jon's Dayton tweet XO on top. Most probable you can get away with it, because the low XO point and steep XO the topology is quite insensitive for driverspacing and phase anomalies.

Greatly appreciated TacoD! Just FYI, my target width for the small eton box (7- 372) will be a narrow 7.75 inches. Will the change in baffle width affect the the tweeter response using Jon's crossover for the R28a? Perhaps not because the baffle on the M8TA RSI is beveled around the tweeter? I plan to use them in a tower design with about 22-30 liters depending on what you think the optimal volume would be for the best bass extension. Thank you!

Jed

[TacoD]

I have found the x-over and I've modified it for crossing at 1100Hz, so you can use the high pass section from Jon. My measuring gear isn't as advanced as Jon's (Behringer stuff), so I cannot guarantee that every wrinkle in the FR is treated .

I would suggest to use the Eton in 24 liters with a port length of 14,4 cm and 5 cm in diameter. My cabinet width is 27 cm. Sorry for the SI standard units, as an European I do not understand those Yankee units.

The X-over:

Image not available

Good luck with your project!

[Jed]

I have found the x-over and I've modified it for crossing at 1100Hz
Good luck with your project!

Thank you TacoD! Right now I'm in the design phase of a modified version of Jon's M8taRSi, but using the eton 7-372 woofers I have on hand. It will be a sort of mini version of the cabinet Jon built. I've never built anything this complicated but if I take my time (estimated time of completion = July) then I might be able to pull off something special. It will be interesting to see how well a crossover put together in "theory" will sound versus a fully tweaked and measured one. I'm going to keep driver spacing and baffle size similar to the M8ta but slightly narrower (9" versus the 11.75") and the baffle is going to be tilted back by about 8.5 degrees versus the 10 degrees in Jons design. Hopefully the changes won't affect the tweeter section of the crossover. Your baffle is roughtly 10.5", so an inch or so shouldn't affect the woofer section too much. We'll see! It certainly is hard for me to accept having the tweeter spaced so far from the midwoofer, but the technology of Jon's filter and your info should make an interesting experiment.

Jed

[Mark K]

Yes, I'm still actually working on this. I'm going to try to put together this xover after lot's of emulating. I decided to spend my money, so to speak on two notch filters (MAD has a sale iron core inductor-say what you will but I WILL flatten a small midrange resonance as well as one around 3k and get the power response a bit smoother!!!). Anyway, I'll prototype one and see if the measured response in close to the modeled one.

PS they sound GREAT with the emulator.

Image not available

PS It looks like I stole Jon's xover and made some minor changes... :

[JonMarsh]

You didn't steal, you borrowed and improved on it for your application...

After all, YOU are the Y in DIY. :B


We'll all be interested in seeing the final result!

~Jon

[Mark K]

A little update.RS225 update

[jdybnis]

Wow, I'm impressed by that crossover! The parts cost is only around half as much as the M8ta-RSi's even though the crossover point is only 9% higher.

Edit: The measured off-axis plot is hard to interpret. Could you put up the LspCAD simulation as a reference point?

[Mark K]

Wow, I'm impressed by that crossover! The parts cost is only around half as much as the M8ta-RSi's even though the crossover point is only 9% higher.

Edit: The measured off-axis plot is hard to interpret. Could you put up the LspCAD simulation as a reference point?

Well, I basically cheaped out on the zobel/impedance compensation. Is it necessary? Well, I plan to try it to see how much of a difference it makes. It does add a bit to the cost, and if the difference is only marginal, well...

As far as the off axis-well, like I mentioned, these are "funny" off axis plots because--the way my off axis pivot works for box speakers, as you go further off axis, the measurement distance also increases. (I have the speaker on a pivot, instead of moving the mic.) So it is tough to interpret. However, I've done the same measurement for my Usher 7" two way and SS8545 2 way with very similar plots.

While there's not enough high quality data to have a good look at the off axis performance yet, it does partially answer one of the questions often brought up that there might be a problem with off axis performance.

[JonMarsh]

Well, regarding your plan to lower it a bit in the 1 kHz to 2.5 kHz region, sounds like a classic BBC dip, almost. Sounds like you''re getting pretty close to what you want...

I've got some H1212's on the way to try in my Modulas, and tweak up. And the RS subs I ordered for testing will be here Monday. Finally making a little progress again...

~Jon

[Mark K]

It's good enough for a listen.

After lots of emulating and building prototypes, I'm going to solder a pair up and see how they sound, "in the flesh." It looks smoother and I've managed to make the traps more affordable at the same time.

Mark K's RS225/RS28A prototype version 6

[JonMarsh]

Looking real good, Mark! Hope I get to hear it at the Octobere DIY.

Is there an official date, yet?

~Jon

[Dotay]

It's good enough for a listen.

After lots of emulating and building prototypes, I'm going to solder a pair up and see how they sound, "in the flesh." It looks smoother and I've managed to make the traps more affordable at the same time.

Mark K's RS225/RS28A prototype version 6

Wow, those graphs look really good to my novice not really knowing what to look for eyes. :E Do you have any measurements below 100 and about 10K? Do you have an approximate price with your crossover components and drivers? How would these compare to say the Modula MTM with the RS28A tweeter both in how they sound and price? I'm looking forward to seeing the finished product. :T

[Mark K]

Ahh, the endless two way

Well, I finally have at least one of the units built. There is a brief update on my page.


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