JonMarsh

Notice pricing has increased for all the designs in this section of the forum. People should use the BOM's and check with suppliers for current prices

Modula MTM-1 Design and Construction- Introduction

Last updated 5-03-2005 Updated BOM list- Testing and final crossover design 3-20-2005 Posted Crossover Xfr Function 05-03-2005

This thread is going to detail the driver measurements, contruction details, crossover design, and final performance tuning for the MTM speaker using two Dayton shielded RS180 (p/n 295-364) and a SEAS 27TDFC. This is intended to be a high bang for the buck system, but to get the optimum level of performance from these drivers, a slightly more expensive crossover is usually necesssary. Still, the bottom line looks attractive compared with the performnace. This post will be edited and updated to reflect work in progress as steps are completed.

My personal versions of this design will be built in Parts Express 1 cu. ft enclosures designed for MTM's. This design is also being used in a cabinet based on the Thor design which uses two Seas Excel 7" drivers and the Seas Millenium Excel tweeter.

The long Xmax of the Dayton RS180 and the low non-linear distortion suggests it should provide compeitive performance, as long as a lower crososver point is used.

Measurement show that up to SPL levels in the mid 90s, the 27TDFC offers low non-linear distortion and smooth wide frequency response; it could be justifiably said that it's the closest thing to a poor Man Millenium Excel's.


Drivers - The Dayton Shielded RS180, (p/n 295-364)


The RS180 is a 7" aluminum cone driver using a phase plug, and featuring a relatively long Xmax for a driver of this type. Furthermore, as Mark K and MFK have shown, measured non-linear distortion and ETC tests are very good, competitive with well known drivers costing much more. However, like most metal cone drivers, they have upper range resonances which require more care in crossover design.





Here the Dayton RS180 (single driver) is measured in room in a Woodstyle test enclosure with the same baffle width as the planned enclousres (11"). Little smoothing was used, and the relatively long gating time shows the effects of room reflections.




Shown here is an impedance sweep for the Dayton RS180; especially the impedance curve above the midbass dip is critical information for the crossover design.





SEAS 27TDFC

Here's a pic of the baby SEAS tweeter (on the left) and it's big brother, the Millenium Excel; note this picture was taken under Halogen lighting, which seems to give the dome material a brownish cast; under florescent lighting, they will look more dark gray.





Below is the frequency response of the 27TDFC measured on the same enclosure which the RS180 was tested on; critical factor is baffle loading and how that affects the frequency response below 5 kHz; this must be taken into account in the crossover design, so IEC test baffle data is not usable without modification, such as simulating baffle diffraction effects. In this case, the tweeter mounting is representative of the target enclosure.

The roll off above 16 kHz is a measurement artefact, not inherent to the tweeter; this was measured with my B&K pressure zone mic, which is more designed for near proximity measurents, and for requires a 90 degree incidence angle for far field measurements, which depending on whether it's exactly on or not, shows roll off above 16 kHz.






Shown below is the impedance curve of the 27TDFC; the impedance rise at the LF resonance will require an LCR zobel, as may the inductive voice coil rise. Even the Millenium Excel doesn't use a Faraday ring to lower inductance.




Cabinet Design and Construction

I chose to develop these projects for the PE (Parts Express) cabinets, because for the money, it's very hard to beat the quality and finish considering the time involved.



The cabinets are well braced internally, also.



If you want to go deeper on the enclosure and use a larger port for more bottom end extension, then you may want to build something your self similar to the FP layout of the 1 cu ft enclosure.

Shown below is the front panel layout diagram for the stand up MTM. The tweeter is offset slightly becuase this produces a flattter boundary and diffraction behavior in the 1-3 kHz reigon, according to Baffle Diffraction Simulator.




Here is shown the realization of this layout in the PE front baffle; note that I use tweeter backing plates to isolate the tweeter from the midwoofer pressure wave, and to strengthen the front panel in the weakest area, considering the number of holes.




This close up of the rear of the baffle shows the reinforcement plate and the bevel routing used on the back side to open up the rear radiation window a little; the RS180 has a large shielded magnet assembly which somewhat blocks the rear radiation.






LF Alignment

The PE enclosure will be ported, tuned to about 34 Hz, using a Precision 2" flared port, ~ 9" long, with an alignment in this size box which will permit output to 104 dB per cabinet anechoic down to ~ 30 Hz. The roll off is such that the - 6dB point is about 37 Hz, which should be compensated by correct wall to floor/rearwall/sidewall boundary placement- flat in room to 37 Hz is qutie doable, with strong output to 30 Hz.

Here's a link to the Precision Port website where one can find information about installing their ports
http://www.psp-inc.com/psp-inc.com/...nstructions.htm




I used Precision 2" ports from PE; the center tube will need to be cut to 3-1/4" to 3-1/2"; note that we're both trying to get the correct tuning length AND clear the internal brace baffle (which must have a clearance hole- I used a 3" hole saw), including the distance to the flare. BUT, we also don't want to be too close to the tweeter brace panel, or port Q suffers- this will allow about 3" clearance, while providing the desired tuning. In a pinch, you could use standard 2" PVC tube instead of a flared port, but expect the possibility of chuffing and compressing at higher playback levels. Spend the extra money.

I used a PVC welding cement to first attach the color to the main port flare, then to attach the cut piece of tube. The assembled port is shown below, prior to installation in the cabinet. The cutout hole, which is centered top to bottom, was cut 80% through with a router, after masking with 3M 2070 safe release tape (heavy white stuff, not the blue stuff; you may have to check your local hardware store; not all the big box places carry it. Can be ordered over the net, too).




If you're using the PE piano black enclosures, take some care while working around them! I use a neoprene sheet on the table, and vacuum thoroughly after every operation.

I use slow setting hot glue as the sealent at the inside corner of the port tube baffle; you have to work quickly, seat it firmly, then install theh mounting screws (Grabber fine thread #8 for metal work are my favorite, because of the strength and built in washer like philips head). Drill pilot holes first, of course. I supposed RTV would be OK, too, but it doesn't adhere quite as well to PVC, and has that nasty smell if you get the "strong" stuff.




Next step is to cement the inner port flare in place; in my case, with a 3-1/4" long cut center tube, the back of the port flare sits flush with the inner brace. You'd think I planned it all that way....




OK, here I've slipped the baffles in (cleaned them with Goo Gone to get rid of the residual adhesive from the masking tape- left them sitting up too long), and thought I'd take a quick pic before putting these away to get some other things done. Time to work on those crossovers.







Crossover Design


Top optimize the performance, considering the large distance between the midwoofers and the cone resonances of the midwoofer above 5 kHz, a low, steep crossover point is preferred. The schematic below shows the topology for a cauer-elliptic filter two way crossover, and the component values for these drivers developed from the measured data. The crossover is designed to provide baffle step compensation and an acoustical 8th order Linkwitz-Riley transfer function for the first 48 dB of attenuation. The crossover frequency is nominally 1400 Hz.

These are the release candidate component values being ordered for testing; I spent some time and effort to try to have standard values so that unwinding coils, for example, wouldn't be necessary. The tweeter series caps will have to be made up from paralleled values; the values shown should be used with tolerances of a few percent, no more than 5% deviation.

If I did my work well, the final actual values "should" be pretty much as shown- this worked out pretty well with my last project, the Arvo Part. I really only expect that there might be some change in the tweeter LPAD resistances- I doubt any other component changes will occur. But who knows?



First Crossover BOM from PE part numbers, using Solen and Jantzen inductors, AudioCap Theta and Solen caps, Mills resistors - See update further on in this post:




This last images from LspCAD shows the predicted resonse from the combination of the measured data and crossover design, and the predicted response based on driver cone diameter, positioning, crossover, and off axis behavior expected as a function of cone diameter. Note that the cabinet used was not the final cabinet volume or including the ported system, so resonse below 150 Hz is not as designed or optimized.











Updated tweeter crossover and power response Plot Feb 1, 2005. See simlar dated post











Updated/Alternative Tweeter LPAD Circuit- 2 dB more attenuation

March 1, 2005




Note changes to R2, R3, and R6.


Update March 13, 2005

Crossovers are built; here's some photo's to help with the layout; I'll be preparing an overlay picture set with component designators, too, later this week.

This is the midwoofer LF crossover board.






The tweeter board is shown next, for clarity of the component layout, the attenuation network isn't wired up yet, as it will obscure some other parts.




The center two connections on the terminal block are both ground; the input at the left, the output at the right.

Here's a shot showing the zobel board installed at the top of the enclosure, and the midwoofer board near the binding post inputs.






This next pic shows the LF board mounted near the binding posts, with the Cardas Crosslink for connecting to the two MTM woofers installed; red and yellow are hot, blue and green are ground.



Next will be installing the wall damping material- Whispermat in my case, all around the upper inside of the enclosure near the drivers.


Assembled Measurements and Schematic after minor tweaks


OK, time for another update. It's been a busy weekend, but found some more time for the Modula IV-1. I'm listening to Sonny Landreth- you Zydeco and cajun fans will know who I'm talking about. "Outward Bound" has some pretty punchy guitar parts and nice bass licks, too. These have a pretty nice vertical window for an MTM (standing is still good, even when they're on stands set for listening sitting down), and the lateral window, as expected, is huge- even 60 degrees off axis is very open and clean. Score one for the home team.

After mostly assembling the first one but with the HF crossover board outside, (wires through the port), I gave it a listen, and as good as it sounded I probably could have stopped there. But you guys know me almost as well as Thomas does, so I fired up CLIO, did a little messing around, and tweaked it up just a "teeny" bit more- very minor mods.



Here's the "final" crossover (anyone want anything different, that's cool; you're on your own. Consider it your homework assignment




VERY little difference - C5 is reduced by 1 uF, L6 is out of there, and R6 is increased to 4 ohms.

Plus, if you plan on using these a little further out from the wall, you may want to install the optional C10/R7 zobel; increases BSC by about 1- 1.5 dB; if you do this, also increase R2 to 4 ohms, and knock down the shunt resistor to 6 ohms. See "Final" BOM.




That's all.


Here's what we get for our efforts. This is measured way out in the middle of the room, to cut down on early reflection messing up the purty pictures. That, plus the short windows, cuts the measured bass. Also, as usual, ignore 15 kHz and above. Yeah, Mark, gotta get that Praxis ASAP.



Better'n a poke in the eye with a sharp stick, at least. Stuff below 400 Hz is starting to show some boundary interaction- these would do better on slightly taller stands.

Here's the impedance curve.




And for those pondering an active implementation, here's the crossover transfer function target.



They won't make those receivers that say "8 ohm or higher speakers" happy, but we never thought they would. I forgot to print the phse on the graphic export, but worst case is within about +/- 30 degrees, so any decent solid state amp should have no worries, mate. You'll notice the box tuning is pretty much as planned, at 30 Hz. That doesn't mean they put out lots at 30 Hz, but the woofer is well controlled, and cone movement is reduced. Vary the fiberfill stuffing to tune the low end; these are probably a little overstuffed; I'm probably going to tweak that a little. IF you shorten the port, you could raise the tuning to the high 30's or so; I would'n't go any higher. That would give you a little more on Rock and roll, but they'd tend to unload a bit with HT type material and no sub.

I will prepare a sort of "white paper" for the project, with more background material, maybe more detailed construction material, in PDF format, linked for download. That will also get posted as a locked sticky thread, then we'll allow this one to drift down to it's natural place in the scheme of things at Mission Possible DIY.

People should read this website regarding the placement of inductors prior to building their crossovers.
http://www.troelsgravesen.dk/coils.htm


Here's a Picture Gallery of completed Modual MTM designs. If you've completed your project, email the pictures to me (ttriff at gmail dot com) and I'll put them in the gallery

People wanting a tower version of the design need look no further than these for the NatP. For those than don't know the Modula and NatP are identical with the exception of the crossover design.

Attached Thumbnails

     

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the AudioWorx
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Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Paul H

Jon,

Great post for a thread that will attract a lot of interest.

Just curious about the tweeter - is the 27TDFC maxed out in the mid-90 dB range? Have you done any measurements at higher volumes?

Thanks,

Paul

JonMarsh

If you want to run it down to 1200Hz or so, I'd say mid 90's is a nice conservative place. Now, with real music, you'd rarely get something at 1200 or 1400 Hz at 95dB SPL just from the tweeter.

For higher SPL's with this low a crossover frequency, one would look to the Millenium Excel, which has about double the Xmax. But consider that I've seen mid 90's pretty clean from the 27TDFC at 800 Hz, it's pretty remarkable... just realize, the IM distortion goes up the more you push it.

If one uses higher crossover frequencies than I like to get away with, I'm sure it would be fine to 100 dB and above. Still, you've got to be realistic about what to expect from a single dome tweeter...

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the AudioWorx
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Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Steve Goff

Jon,

Great thread! Were you to apply this sort of design concept to make the best MTM you could make, using available parts, and about the same size cabinet, would this be what you would come up with, or would you use other drivers? In other words, what would a Modula Max look like, and how would you say the performance might differ?

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Steve Goff

JonMarsh

Interesting question, Steve. An obvious upgrade path for the tweeter would be the SEAS Millenium Excel. Lower distortion at the lowest frequencies, plus it shore do look purtty...

A midwoofer upgrade to this concept is trickier than you might expect. An obvious tack would be to use the Excel W18 midwoofers- but does it buy you anything? For good power response and low crossover lobing, one want's as low a crossover freqeuncy as feasible. The main advantage the W18 has over the RS180 is a higher frequency for the top end breakup, and lower rear masking. But the cost difference is enormous. I'd put the money into better tweeter caps myself, such as AudioCap Theta's.

Another 7" midwoofer that measures very well is the Peerless HDS 850439. But they're $75 each. I'm planning on using them in the "high efficiency" version with TC120dx2 Focal tweeters, which will need a little higher crossover point- the Peerless has very good ETC cuves up to 1800 Hz or so. The Modula Maxx I've been planning will be used with dual RS270's in a bass bin on each side, and won't have conventional BSC on the MTM array; that will be filled in by the bass cab.

Now, the other thing to do would be to go with a Thor style TL enclosure- will give deeper bottom end, I expect. The box Fb tuning I'm using is about 32-33 Hz; the -6 dB point, becuase of the smallish enclosure, will be 37 Hz; but with reasonable room placement, for boundary re-inforcement kicking in about the mid 40's, they should be subjectively flat to about that point.

Now, if one is willing to go with larger drivers, bigger enclosure, I'd do an MTM with M8a or maybe even RS225, with the Millenium tweeter. That will be much bigger, and will put more stress on the tweeter if you use the RS225, as it needs a lower crossover frequency.

But I actaully need these in a relatively compact enclosure, which is why the 7's. It's for my new HT setup, since I've moved the projector and separated HT and two channel music, to opposite ends of what is the same living space. An old friend also wants something like these, so I'm probably going to be building a couple more pairs, if he likes them. I offered to let him just take them home, then compare against Polks or whatever he finds at Magnolia HiFi. He's also interested in the center channel design.

I've got all the measured data for that one too, and that thread will be up in a week or two, depending on how crazy work is.

~Jon

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the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Mark K

Ha, you've always got to find a way to stick some really big caps in the xover

It looks great. I happen to think this will be a great combo. Honestly, I don't think you could make a better 7" based MTM without spending a whole lot more money.

I'm looking forward to hearing it sometime.

PS. Steve-the modula max will be the same except have the Dayton RS series tweeter in it

Brian Bunge

Jon,

Great work so far! I can't wait to hear your impressions after an actual listening session or two.

Mark, has PE actually announced an RS tweeter yet?

EDIT: Just found it! Looks like Jon's got more work to do!

http://www.pesupport.com/cgi-bin/config.pl?read=202419

Mark K

What? Where? Who?

I didn't say anything about an RS tweeter. Did anybody hear me say anything?

JonMarsh

Oops!

Well, at least I didn't slip up this week about the Avalanche 12's that aren't available and aren't in production. Jack spilled the beans on that one, and before I even got mine to test!

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

cjd

This looks great! I'm wondering about these RS180's, because it seems to only offer a few more Hz of bass extension over the RS150's (which are also more efficient!). And the RS150's should allow even Jon to play with a higher cross point (I'm using a probably heretic 2200hz or so). Of course, it's shy 2mm of xmax... ahh, the fun of trade-offs.

Jeff B needs better elliptic filter support in his crossover spreadsheet. I don't trust Speaker Workshop (I have found it does not always jive with PDC3.0, sometimes rather dramatically, and with a few checks by someone using LSPCad it appears it's SW that is in error). And I can't justify the expense of LSPCad (well, I can to ME, but that's a lot of shoes and we don't have enough shoe space as it is!).

C

JonMarsh

Ah, isn't that true! Thanks for the kind words.

I looked at the RS150 quite a bit; the problems with it were three fold:

1) Lower Xmax - 2mm, as noted.

2) Smaller Sd - less cone area for pushing the bottom end (I don't generally even work with 7's for that reason!

3) More severe rear masking of the cone by the frame and magnet assembly than even the RS180 . The RS150 is very problematical in that reagard, unless you do what I did once with some seas drivers, and make a 1/4" aluminum face plate with the necessary cut away, and cut back the wood part of the baffel so that the relativley shallow rear opening isn't blocked.

The upper end of the RS150 does seem to be more extended. BUT, that brings us back to the whole issue of MTM's and spacing and wavelength at crossover frequency, by which calculation I'd really rather have a 1200 Hz crossover, but given the driver characteristics, I think the 1400 Hz crossover is a good tradeoff, considering attenuation of the tweeter (-20 dB already at 1 kHz) and trying to get off the upper end of the midwoofers before getting into problematic ETC regions.

It's about balance, and that's where a little artistry and judgement has to come in, and of course, that's subjective; maybe my choices won't be the optimal for everyone. But it's a starting point they can work from.

I'm looking forward to hearing these soon; I'll update the first post soon with a proposed BOM for the crossover.

Yes, an outright purchase of LspCAD 6 has become somewhat pricey, even for the standard version. It is very good, though; a lot of features that make it more of a production environment- that is, with some setup work, you can create customized components and templates and crank out a lot of designs fairly quickly, with good documentation. I like it.

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Steve Goff

That nonexistent RS tweeter sounds very interesting, as does the Excel metal-dome tweeter recently announced by SEAS.

On second thought, and having now looked at the SEAS information, the Excel tweeter doesn't look that wonderful. But who knows?

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Steve Goff

JonMarsh

Yeah, it's puzzling Steve. It's not a replacement for the Millenium, it's more like a different flavor with different tradeoffs. Can't say I'm likely to run right out and buy some...

Mark K has been working with the RS tweeter, and has tipped his hat a little about the test info- it looks quite promising, inclucing for an application like this.

As I've said before many times, it's shaping up to be a very interesting year.

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Steve Goff

Yeah, I thought the jawdropping icon was some sort of clue!

__________________
Steve Goff

Brian Bunge

Jon,

Now you're really killing me! I got my first pay check today and it was almost 50% more than my standard 2 week's pay from my old job! Once I get a few bills back in line I'll be foaming at the mouth to buy some drivers! But now I want Mark to spill the beans about the RS tweeter.

Bent

Brian, that's gonna cost an extra 50% on top of the pre-order price, :ROTF

Mark K

Here it comes...

I'm not at liberty to discuss it.

There. I said it.

Anyway, I don't know about the final details-after all, there is no final product-but so far the tweeter looks very, very promising. Apparently it was shown at CES and Darren at PE has let out some information. When Darren gives the OK, I'll post my test results.

mark

PS You won't go wrong using the Seas 27 series. This is also a suberb tweeter that crosses low.

cjd

I believe, based on some other comments Darren has made, that he expects the price to be in the $50-60 range. So the 27TDFC is still a standout at its price-point. IF the RS tweet has more excursion then it will be a bargain as much as the rest of the RS's, and it seems like that may be the case from the whispers I've heard. No idea.

I have found that I just don't care for the sound of a metal dome tweeter (if it matters, I heard 3 of John Krutke's designs, and the only one I liked the top end on was the one with the 27TDFC - he had one with the TBFC and it was harsh to these ears. No idea how y'all think of his work, but it stood out among the non "kit" works to be sure). So, I may design for it but never use it myself. But, since Darren suggests 1500Hz crossovers are a walk in the park, I wonder if some of Jon's crazy elliptic stuff would drop that significantly. Then again, we only know that Fs is below 1000hz. I also wonder if it would stand some of those tweaks we saw on that LG tweet, since it seems like it may be constructed similarly. . . heh. Speculation on rumors is SO much fun!

C

JonMarsh

I've found that voicing metal dome tweeters is a little more critical, and also the quality of associated sources and electronics- they can be very revealing. OTOH, the only cloth dome tweeters I like sound more like metal dome units than most.

Also, MOST metal dome tweeters come with these goofy diffusor/resonantor assemblies, and it's ALWAYS necessary to get rid of those to get the best and most natural sound. Starting doing that with MB Quart tweeters back in the mid 80's.

An interesting experiment also, is to pick a tweeter with a high twenties to 30's resonance, and design the tweeter crossover as a band pass..., rolling off above about 22 kHz.

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Hank

Jon: great work, as usual! This may be THE high performance value MTM.

Speaking of new PE stuff, did you notice the new Hi-Vi RT1L Round Planar tweeter? 3,500 - 40,000 Hz response, 88 dB. $41.90 regular price. I'm wondering about it as the supertweet in your statement speakers, the Saint-Saens?

JonMarsh

Thanks for the kind words, Hank.

I'm wondering, don't you think it's odd they don't even have an FR graph posted? I saw some data on this once on the Swan's site, but don't remember the details. The other RT-1 types I've seen tested had poor non-linear distortion and pretty high IM.

For about a month there's been a big box in the corner of my dining room with 16 Fountek JP2's. They seem to be made pretty well; quite substantial, and fairly heavy, considering they use neodymium magnets. I haven't run a line source simulation yet using the FRD tools, but with the relatively small gaps between the ribbons vertically, I think they'll hold pretty well. To use domes or round planar devices, the spacing would have to be pretty close to work up to 20 kHz.

I've mad a promise to myself to finish the M8ta's and the Arvo's at home before starting the Saint-Saens in earnest; I also have some driver testing to do, with both the Ascendant Atlas 12 and Avalanche 12 (not yet in production).

It's gonna be a REAL interesting year...

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

MightyM

Long time lurker, first time poster.

I was relatively recently bit by the DIY speaker bug after I decided to build a set of Adire's 281s. Since then I've been trying to learn as much as I can about speaker design as quickly as I can. Now I'm on the hunt for a good, reasonably priced speaker design for my 2 channel system, which is what peaked my interest in this new MTM design. It looks like it's got a high "bang for the buck" quotient.

I see that the initial design uses the PE 1 cu. ft. enclosure, but since I've never bought one of those before, any chance you could give a 2 second rundown on the cabinet design? I'm mostly curious about thing like internal bracing, since the PE website already gives the external dimensions.

Thanks a lot!

JonMarsh

I've got several other projects going that require construction from scratch, and in this size range, I think it's hard to beat what PE offers.






This is one of the piano black cabinets I have a pair of; also have a cherry set for a center channel project.

The cabinet is braced internally mid way front to back with a large panel parallel to the back and front, with two large hole cut outs to facilitate using the acoustical space and wiring/crossovers on the back side if needed. The front panel is 1" MDF. It's removable, shipped held in with screws and embedded pem nuts; I have taken them in and out a couple of times, but what I do when the design is finished is glue them in. The finish on the front panel is a satin black; the main cabinet appears to be a lacquer finish. There are holes in the back which fit some binding posts available from PE, though of course, you could enlarge them and use something else, like the Cardas binding posts I prefer.

Hope this helps...

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

MightyM

Excellent. That's about what I guessed, but it's good to have confirmation. Thanks a lot for the info.

GrahamT

Hey mighty here is a pic of the guts.

JonMarsh

Thanks, Graham! Your picture is worth hundreds of my words!

First post updated again.

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

GrahamT

Is that supposed to be me?

JimRHIT

Jon,
long time lurker .. first time poster on here

Quick question for you....

How will you be dealing with the mutual inductance as a result of using the multiple inductors?

Do you plan on stuffing all these goodies inside this tiny bookshelf?

not being picky here .... just curious

__________________
starting from scratch ... everything but my trusty Marantz was left behind in Indy

JonMarsh

I split the crossover into three boards, usually; Low pass, high pass, and tweeter zobel.

Coupling issues have been a bit blown out of proportion when folks test with a current driven through one inductor, and the other inductor open circuit- almost ANY current coupling will product a moderate voltage under those conditions. To be a valid test, for voltage/signal transfer, the inductor should be loaded into an impedance similar to the working filter circuit.

Of course, that doesn't mean not following good layout practices, keeping the distance, and orienting on different axis in some cases.

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the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

aarondewitt

Jon,
Where does the port to this bad boy go? Are you done updating or do you have more things to add? Thanks! I cannot wait to build a set of these i think i am going to buy the parts today.

JonMarsh

It comes in on the back behind the tweeter. Haven't posted those pics yet; I'm still in Denver and don't have all my data on the laptop. I'll be back in CA later this week.

These are not meant to be put on the wall, but on a shelf or stands; they have full baffle step comp. Obviously, in this size a box, they aren't an optimum bass extension for these driver, though it's fairly good; the inputs I got when starting this design is that most would eventually use a sub at 75 Hz or higher, so they're designed for enough bass extension to be satisfying on a lot of music without a sub, and to blend well with a sub when used with that sort of crossover range,.

There will be additional updates to the main top post as other work is completed and final measurements and tweaks if necessary are done. I could have waited to post everything at once when completed, but it would have been an awful lot of work, and a lot of guys expressed interest in seeing the design as it progressed.

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Stevepaul

I bought 4 of the RS180's from PE when they went on sale for $25/ea (I got lucky and received them 2 days later). I have been following this thread and have already placed an order for the 27TDFC tweeters which should be here in a couple of days. So far so good...

...then it hit me, I had completely forgotten about a set of enclosures I made about 3 years ago but, never finished. I ran (literally) downstairs and measured them. They are 10.5" wide (PERFECT! ) 44" tall and 11" deep. All the walls are 1.5" thick and the baffle boards were never cut (these things are heavy).

I worked up some 'Unibox' numbers on them and with a Net volume of 38liters tuned to 38hz, I get an 40hz f3 and a reasonable port length. PERFECT!!

I am going to build some 5" high boxes to put the crossovers into and use them as bases for these speakers.....which gets the tweeters up to about 39"-40".....PERFECT!!

Jon.......how's this sounding to you? With the baffle width the same as what you are using, everything should be perfect....right!???? (please don't rain on my parade!)

Steve

JonMarsh

You'r on a hot streak, I'd say... Go for it!

You may find that if you can do a slightly lower Fb, that the resonse in room will be smoother- my small boxes are tuned to 38 Hz; with room lift at the low frequencies, it's often better to have a shallow roll off that complements the room gain- say, -6 dB around 38 Hz. Think about it, and try modeling in Unibox.

You might have to run the port out the bottom like I do with the M8ta if you need a longer one- that works well, gives you nice boundary coupling in the low frequencies (when sweep testing the M8ta, it was shaking bits in the room in the lower frequency ranges with a single 8".

~Jon

__________________
the AudioWorx
_______________________________

Modula MT
M8ta
Modula Neo D CC
Ardent
Modula MT XE
Modula Xtreme


still coming in 2010....

Ardent Cxi (updated design, new woofers)
Ardent CCX (Compact Center Xtreme)

Stevepaul

Jon,

I do prefer a tighter, less boomy sound. If I choose an Fb of 28hz, it gives an f3 of 56hz and an f6 of 38hz....which is what you are suggesting. This would give me a port length of 14"....no problem.

My question: I would prefer to put the port on the back of the enclosure, run the port tube 7" into the enclosure and then put a 90 degree turn and run it up the middle, the rest of the 14". This would allow me to keep the crossovers in the separate 'base' of the design.

I have seen many questions regarding 90 degree turns in Ports but, I don't remember any negative comments....

Can I do this...or would you recommend against? (sorry if this is a FAQ)

Best regards and many thanks,
Steve