Modula MT-XE - You didn't ask for it... it's coming anyway

[villastrangiato]

I think I saw a Magico review in Stereophile that mentioned a specific significant resonance (around 400hz )on the back side of the speaker near one of the tensioning rods. I like the laminated bb concept. In fact, I have about 1200lbs of 5 x 5 3/4 BB sitting in my garage for the top secret "Dark Side" design I've been working on for the past year and a half. But the massive aluminum baffle and tensioning rods always seemed to me to be a bit overkill and a likely source for trouble. My design calls for threaded rod clamping the layers together, but certainly not under any great tension. I just don't like relying on glue alone to keep things together over the long haul. My father built a huge butcher block island out of 2x2 maple back in the seventies. After about 12 years, a couple of joints on the end of the 10 foot top began to separate - and this was the only area adjacent to the cooktop that wasn't through bolted. I've never forgotten that - as it was a rather sore issue with my father who was rightly proud of the rest of his work.

I like using MDF strictly as a vibration damper layer. For any bracing that might be subjected to tension in addition to compression - I use low void plywood. Interestingly it costs about the same as MDF but is noticeably lighter (bonus )

[evilskillit]

Yeah after having built a few speakers and several subs from MDF I just got sick of the weight and the dust. I picked up some birchy ply from the local Home Depot. Its not top notch stuff but its so much lighter, so much easier to cut (or it seems that way, maybe just because its lighter) and creates so much less nasty dust. I'm liking it so much more than MDF. I'm having a hard time imagining going back to MDF, tho I wish I had made it to the place around here that has good wood, they had veneer core birch ply for sale for $53 for a 4x8x0.75 sheet. Which sounds pretty good to me, but I got a flu and didn't feel like making the trip before the sale ended.

The bamboo stuff seems really attractive but is completely budget prohibitive for me. I'll just try a few builds using birch and brace the heck out of em, maybe double up on the baffles and add plenty of extra bracing. Given the cost differential of the material I can afford to, even if the enclosure has to be a bit bigger because of it

[Mark K]

Oh, man guys! It's not worth all those disc herniations...let's work on less baffle not more...

don't be asking me to carry your big amps and speakers at the DIY in April!

[cjd]

Mark, you need the forklift to get those drivers up off the ground high enough anyhow... might as well use it to move finished speakers. . .

[villastrangiato]

Yeah after having built a few speakers and several subs from MDF I just got sick of the weight and the dust. I picked up some birchy ply from the local Home Depot. Its not top notch stuff but its so much lighter, so much easier to cut (or it seems that way, maybe just because its lighter) and creates so much less nasty dust. I'm liking it so much more than MDF. I'm having a hard time imagining going back to MDF, tho I wish I had made it to the place around here that has good wood, they had veneer core birch ply for sale for $53 for a 4x8x0.75 sheet. Which sounds pretty good to me, but I got a flu and didn't feel like making the trip before the sale ended.

I got the full crate of 3/4 Russian Birch from a major warehouse - cut out the lumber yard retailers completely. Hey, the retailers don't stock that much of the stuff - some a half dozen crappy little sheets if you're lucky. I forget how many sheets are in the crate - I know from how much it weighed down my Tundra on the 200 mile trip home - and from the invoice, it was well over a thousand pounds. I think the price was somewhere in the vicinity of $30 a per 5x5 sheet - total came to around $600. So if you want real Russian Birch - and you're able to pick up at least a crate in the northeast area - I can hook you up. Otherwise, I prefer the $25/sheet low void A/C plywood at HD. It seems to be denser than the balsa cored birch and oak veneered plywood that HD sells. Trying to get BB from local, "rip you a new #$$" middlemen retailers - you wind up paying $65-90!!! Shipping to you via train or truck might be pricey. And the only other Russian Birch direct importers I'm aware of are in Quebec(or Ontario?) and out in L.A.

[JonMarsh]

Oh, man guys! It's not worth all those disc herniations...let's work on less baffle not more...

don't be asking me to carry your big amps and speakers at the DIY in April!

Yeah, well since LBL is typically lighter, AND much stronger, there's no weight issues compared with MDF.

So does that mean you won't help me unload my 115 lb Ardents at the meeting in April, Mark? Well, don't feel bad, Mark, and I won't worry, since I did it myself when I went to Denver with them. :W The other projects should be significantly lighter. At least a lb. or two...

Maybe you can help with the Mac Mini...

And I won't bring an Aragon to the April meet, I'll bring my traveling amplifier, a Cambridge Audio 840W. It's only 42 lb, so even aging disk hernia survivors like myself can carry them around with impunity. :B

[JonMarsh]

I got the full crate of 3/4 Russian Birch from a major warehouse - cut out the lumber yard retailers completely. Hey, the retailers don't stock that much of the stuff - some a half dozen crappy little sheets if you're lucky. I forget how many sheets are in the crate - I know from how much it weighed down my Tundra on the 200 mile trip home - and from the invoice, it was well over a thousand pounds. I think the price was somewhere in the vicinity of $30 a per 5x5 sheet - total came to around $600. So if you want real Russian Birch - and you're able to pick up at least a crate in the northeast area - I can hook you up. Otherwise, I prefer the $25/sheet low void A/C plywood at HD. It seems to be denser than the balsa cored birch and oak veneered plywood that HD sells. Trying to get BB from local, "rip you a new #$$" middlemen retailers - you wind up paying $65-90!!! Shipping to you via train or truck might be pricey. And the only other Russian Birch direct importers I'm aware of are in Quebec(or Ontario?) and out in L.A.

That's all a bit far for me to drive... ;^) $600 isn't bad, though. I'd have to check with the local stores- I'm in pretty good at the Rockler in Pleasant Hill, they "might" cut me a deal on that kind of volume. Can you imagine the volume of waste material to haul off after all the machining though?

[villastrangiato]

Now you know why I've been in the design phase for a 540 liter 6 driver TL for nearly 12 months. Most of the design work thus far has involved making use of cutout pieces. The Magicos and now the Evolution Acoustics have really inspired me to forge ahead with the laminated concept. With their successes, I don't really feel like the Don Quixote of DIY speaker design......There are solid advantages to the excess - at least a significant number of people seem to think so. If I ever get lucky and start producing speakers in quantity as a real job, you can be sure the 3.25 horse Freud and Porter Cable will be retired to dust collection duty on the shelf - CNC router, baby - all the way!!

[evilskillit]

Hrm, the AC plywood Home Depot sells is priced pretty well. You think it'd be better than the birch ply? I usually avoided it because I figured it was pine, which I'd heard to avoid because it was too soft and light, but if you think its better than their cheap birch ply maybe I'll check some out next time I go. I've just already gotten sick of MDF is all

I got the full crate of 3/4 Russian Birch from a major warehouse - cut out the lumber yard retailers completely. Hey, the retailers don't stock that much of the stuff - some a half dozen crappy little sheets if you're lucky. I forget how many sheets are in the crate - I know from how much it weighed down my Tundra on the 200 mile trip home - and from the invoice, it was well over a thousand pounds. I think the price was somewhere in the vicinity of $30 a per 5x5 sheet - total came to around $600. So if you want real Russian Birch - and you're able to pick up at least a crate in the northeast area - I can hook you up. Otherwise, I prefer the $25/sheet low void A/C plywood at HD. It seems to be denser than the balsa cored birch and oak veneered plywood that HD sells. Trying to get BB from local, "rip you a new #$$" middlemen retailers - you wind up paying $65-90!!! Shipping to you via train or truck might be pricey. And the only other Russian Birch direct importers I'm aware of are in Quebec(or Ontario?) and out in L.A.

[villastrangiato]

I took my secret weapon to HD a while back - my father who has a lot of experience building custom cabinets - also worked at MIT in metallurgy and materials science many years ago. I thought the birch and oak plywood would be better. He pulled me over to the A/C pile and showed me the difference - practically no voids whatsoever. According to him, some pine - particularly southern yellow - is extremely tough and strong. According to him, the A/C is designed primarily for structural purposes where the HD birch plywood was intended for furniture and cabinetry. According to him the core is denser on the A/C and the glue content is higher to produce greater strength between layers. And besides, the speakers I'm now building with the HD A/C plywood and mdf he bought are his - using mostly BG and Dayton stuff. Not that the 75 year old is that much of a fart - he loves bass....I'm now supposed to somehow jam his 240 watt plate amps into an 11.5 inch wide cabinet with 2.25 inch thick walls... :roll: I think we're going to go with external crossovers for this one - I really don't want to go below 115 liters for the RS 315 subs anyway.

Additional note: If you look here:

http://en.wikipedia.org/wiki/Plywood

There's a little blurb about decorative plywood about half way down and there's a picture to the right hand side that looks a lot like the "oak" plywood HD sells. Based on what my father (and brother who works for HD as a kitchen installation contractor for most of the stores in Maine) tell me, the birch and oak plywood at HD are the "decorative" variety. If you want strength, you're better off going with the "A" graded material - of which there obviously are several grades. This leads to eyeing over what's available which varies in quality from manufacturer to manufacturer.

[ergo]

I have used the car audio targeted bitumen damping sheets to a very good result with both plywood and MDF boxes. It takes the resonant frequency down lot and makes the box very dead and heavy without much lost space inside the box.

On my last speaker pair I sandwitched this between the box and the front panel + applied layer to each wall - the "knocking on box" test for the result is very very dead thumps.

I wonder why this technique is not used more as the pads are readily available with glue on back and all - so very easy to apply...

[spadez]

Would someone mind explaining to me what LBL is. Im having a hard time following, im guessing its a general name for A-grade woods in comparison with MDF?

Also Jon if you read this, would you mind telling me briefly what kind of difference would be expected between your proposed modular TMW design and the TMM design?

[5th element]

Would someone mind explaining to me what LBL is. Im having a hard time following, im guessing its a general name for A-grade woods in comparison with MDF?

It stands for Laminated Bamboo Lumber.

[JonMarsh]

Would someone mind explaining to me what LBL is. Im having a hard time following, im guessing its a general name for A-grade woods in comparison with MDF?

Also Jon if you read this, would you mind telling me briefly what kind of difference would be expected between your proposed modular TMW design and the TMM design?

LBL is discussed a lot in the Ardent thread, where I first started using it in a front panel construction.

Ardent



The TMM 2.5 way uses two identical Seas ER18RNX woofers, same total complement as for the Ardent, in a 2.5 way configuration where one woofer carries midrange up to the crossover point and one only handles BSC range and below, not the full midrange.

The TMW will be looking to shoe horn a ScanSpeak 22W/8867T00 in the same 22 liter cabinet volume for the 0.5 driver; this woofer has 9 mm Xmax, very low distortion in the bottom end, and the radiating area of an 8" driver instead of a 6-1/2" woofer (which is almost double the cone surface).

Doing this without a big Qt hump in the response and also extending the bottom end of the system (and being able to tune that extension and response profile) requires using what I call a flux capacitor.

This is a plot of the concept applied to a 10" Scanspeak; I don't have a posted graph handy for the 8" Scanspeak.



Black is driver without flux capacitor, red and green plots are with two different sizes; showing removal of Qtc bump and extension of bottom end, different tunings desired depending on room position requirement (leaner profile better for near wall placement; green for position out in the room with room boundary lift pushed lower in frequency).

You don't get something for nothing; the additional capacitor causing the current phase shift also adds one more roll off pole, so the system is 3rd order instead of 2nd order as a conventional sealed box. Ported systems are 4th order at the least. Hoffman's Iron law is preserved- no fooling father physics. But the tradeoffs are quite useful, I believe. Main point is to be able to get more low frequency output through the use of a larger driver with greater Xmax in a smaller box than normal, and to be able to tune the response to the system placement.

[evilskillit]

Gah, I'm so OCD about some things, I've got most of 1 cabinet done in HD birch for my Zaph Waveguides and now you've got me wanting to start over with better lumber. I really shouldn't tho. I need to just brace it, dampen it and get this project finished. I'm working way too slowly as it is.

There's a little blurb about decorative plywood about half way down and there's a picture to the right hand side that looks a lot like the "oak" plywood HD sells. Based on what my father (and brother who works for HD as a kitchen installation contractor for most of the stores in Maine) tell me, the birch and oak plywood at HD are the "decorative" variety. If you want strength, you're better off going with the "A" graded material - of which there obviously are several grades. This leads to eyeing over what's available which varies in quality from manufacturer to manufacturer.

[dlneubec]

Black is driver without flux capacitor, red and green plots are with two different sizes; showing removal of Qtc bump and extension of bottom end, different tunings desired depending on room position requirement (leaner profile better for near wall placement; green for position out in the room with room boundary lift pushed lower in frequency).

Jon, how are you doing your boundary and room pressurization gain simulations?

If you or others here have not seen it, Jeff Bagby has a cool new (and free) program that combines the ability to model baffle edge diffraction, for monopole and dipole, with room boundary reinforcment (based upon Allison's work) and room pressurization gain. You can study each individually or combine them. It is extremely easy to use, but does require excel (2003 or 2007 versions available). It can be downloaded here for anyone interested:
Jeff Bagby's loudspeaker design software

[JonMarsh]

HI Dan- This is an anechoic nearfield driver/enclosure simulation. For boundary distance studies, I use my own MathCAD tools, developed in the early 90's on the first version of MathCAD for Windows, which are also based on Allison's original papers. For baffle edge diffraction and shape simulation, I prefer EDGE.

In general, though, I find it faster to build and measure comprehensively than to spend too much time simulating, and I have more confidence in the results. :W

The biggest problem in the world with sharing DIY designs and getting the best results out of them is that so few people are in domestic situations where their significant other will permit setting up speakers optimally. Few can/will even do something like the basic Cardas setup.

[oneplustwo]

That's all a bit far for me to drive... ;^) $600 isn't bad, though. I'd have to check with the local stores- I'm in pretty good at the Rockler in Pleasant Hill, they "might" cut me a deal on that kind of volume. Can you imagine the volume of waste material to haul off after all the machining though?

Jon - I'm in SF and might be interested in splitting a part of whatever the minimum volume Rockler might require of you. I wouldn't need much, but thought it might help.

[JonMarsh]

Jon - I'm in SF and might be interested in splitting a part of whatever the minimum volume Rockler might require of you. I wouldn't need much, but thought it might help.

I'll keep that in mind! I wouldn't be doing a big translam project until later in the year.

[JonMarsh]

New VC's came in from Madisound, for the D2608/9130; easy to install.

Also tested an Accuton C13N waveguide combo that I built in 2007. Nice output level, but overall the D2608 cleans it's clock on fidelity parameters: much smoother in the 9-18 kHz area, especially off axis where the inverted cone Accuton can develop dips of 18 dB, and much lower in distortion, as much as 15-18 dB lower in the lower ranges, and a solid 10 dB advantage in the 3-6 kHz area. Was thinking about trying the C30N, but I think it would have the same off axis issues, due to geometry.

Well, I think we have a winnah... let's hope they don't discontinue it on me!! Think I'll stock up a bit next paycheck! The only other unit I've got lying around it might be curious to try is a pair of Millenium Excel- never been that fond of them because of the relatively rough frequency response, but the low range distortion is very low on the set I have- very low. I suspect with their faceplate they may not interface well. It would take a different "cut" and opening than for the D2608. What the heck... the H65 waveguide is cheap...



Imagine how old school that would be!! :rofl:

[numberoneoppa]

Off topic, Jon, but are you using TeX to write your [to be] PDFs?

[JonMarsh]

No- Pages (Mac app- part of iWorks). It can handle equation editing, too, but the PDF is all about documenting how to put it together, and how the crossover works, and how it measures and performs.

iWorks includes Pages, Keynote, and Numbers. I do all my presentation work at work with Keynote, technical papers (like IEEE conference papers, magazine articles) with Pages. I use MathType or MathMagic with iWorks for math typesetting. Occasionally for a real complex piece I use Adobe InDesign still, but mostly I don't need that.

On the PC environment, which I don't use much anymore, I use Framemaker and Ventura Publisher.


iWorks

[numberoneoppa]

I look forward to seeing them once you publish them here.

[JonMarsh]

It's close to being done. By sometime this weekend, certainly.

[spadez]

Really random question Jon, but how did you take the pictures on the first page, specifically the waveguide with the wax paper separator.

Ive been trying to take a picture of a product for a project for uni, but I cant get the light right. Did you just take it in natural light on white paper with a good camera or do you have extra lamps to illuminate what your taking a picture of?

[JonMarsh]

I have halogen lamps, shoot RAW with a Pentax K-7 (mostly these days- I have other good cameras, but this is by far my favorite), process with Adobe Lightroom or Iridient Raw Developer, adjusting white balance, black levels and peak white recovery as needed, and exporting to mid quality JPGs in sRGB. The background is Epson Premium Matte presentation paper, I do a white balance setting on it, then warm it up by about 100 degrees because that will look better over a wider range of displays (many of which are more blue than D6500).

Depending on subject and backgrounds I adust eV up to a stop and a half, because of the influence the subject has on automatic metering, just checking as I shoot with the histogram in the INFO display.

I know when I write this out it sounds complicated, but it really isn't, just a quick basic flow. Complicated is when I have to bring white balance cards and shoot those as well as what I'm shooting to get the white balance right, and have to do HDR bracketing to get the dynamic range covered with wide dynamic range material, then do curves adjustment for the light mapping in development in Lightroom or Aperture (I prefer Aperture, but it doesn't support RAW files from my Pentax K-7).

I really prefer "point and shoot" nature photography over this stuff, but if you want to tell a tech story, I don't like the pictures to look crappy. OCD, you know. :W

[---k---]

Can you bring your gear over and shoot photos of my steel tube speakers when I'm done?
Reflective surfaces suck to photograph.

[numberoneoppa]

Can you bring your gear over and shoot photos of my steel tube speakers when I'm done?
Reflective surfaces suck to photograph.

Just don't use a flash, or make sure you diffuse it well (softbox, umbrella, paper towel, etc). Also, if you can have the flash hitting them from a different angle than the camera, it helps.

-Josh

[Biff]

Can you bring your gear over and shoot photos of my steel tube speakers when I'm done?
Reflective surfaces suck to photograph.

JUst a bit of a different challenge, let me know if you want tips on that. I have shot some really neat glassware and other shiny bits and when you get it right it's dynamite.

[Bear]

I(many of which are more blue than D6500).

Way, way more blue that D65, in fact. I had an LCD that measured 12000K out of the box. Many displays are in the 9000K - 10000K range out of the box.

Also, in photography parlance, you are making it "cooler", rather than "warmer", but that is a different forum...

[cjd]

Can you bring your gear over and shoot photos of my steel tube speakers when I'm done?
Reflective surfaces suck to photograph.

How big are they? I think a bit too big for my light tent but perhaps not if we just ditch the default drop and use the tent part. Bring 'em by. Reflective surfaces are fine - a lot of my portfolio is metal and glass and graphite-on-gesso drawings, all rather reflective. (most of my portfolio is either not reflective or already photography, which I usually don't have to photograph...) Even if the tent doesn't work we can get it worked out.

C

[JonMarsh]

Can you bring your gear over and shoot photos of my steel tube speakers when I'm done?
Reflective surfaces suck to photograph.

Yeah, they do, usually a circular polarizing filter helps with that!

[JonMarsh]

Just don't use a flash, or make sure you diffuse it well (softbox, umbrella, paper towel, etc). Also, if you can have the flash hitting them from a different angle than the camera, it helps.

-Josh

Never, never use flash, except as a last resort to capture fast motion with a separate unit, typically bounced off the ceiling or floor.

[cjd]

Except at ball games, where it's SURE to reach from your nosebleed seats all the way to the ground where the players are...

[JonMarsh]

Way, way more blue that D65, in fact. I had an LCD that measured 12000K out of the box. Many displays are in the 9000K - 10000K range out of the box.

Also, in photography parlance, you are making it "cooler", rather than "warmer", but that is a different forum...

yeah, well, let's not get distracted here... :W

It's just a means to an end. Bad choice of words to talk about "warming up" something by dropping the color temp a 100 degrees, but when something bluish looks too cold, that seems the term to use, subjectively! :W

[JonMarsh]

Except at ball games, where it's SURE to reach from your nosebleed seats all the way to the ground where the players are...

Don't even get me started on all the idiotic things people do with photography in public places!!!!! It's just because they have their digital camera set one way, and always shoot that way (usually with the flash on). I could cry sometimes when I visit friends and see their photo albums of the relatives and grandkids and how bad they look, and what could have been...


So I take it all out on building speakers... and being an audio nazi! :W

[---k---]

Thanks for the tips. My garage just doesn't have the right lighting.

[JonMarsh]

Thanks for the tips. My garage just doesn't have the right lighting.

Get some of those Craftsman Halogen work floods- they'll do wonders.

[numberoneoppa]

Get some of those Craftsman Halogen work floods- they'll do wonders.

YES, they provide light, and lots of it. Might be a little harsh for the metal, so you'll have to diffuse it. In a dark room, they give you a really dramatic lighting/shadows.

[JonMarsh]

Bounced from ceilings or with diffusers they work pretty nice IME.

[---k---]

Get some of those Craftsman Halogen work floods- they'll do wonders.

Actually, I just need to buy new bulbs.

[cjd]

With shiny you may need black and white backdrops placed just so to get reflections to be clean and such...

[numberoneoppa]

Never, never use flash, except as a last resort to capture fast motion with a separate unit, typically bounced off the ceiling or floor.

Haha, there's nothing wrong with using a flash if you're good with them.

[don9146]

Bounced from ceilings or with diffusers they work pretty nice IME.

Since this is a DIY forum, here's a quick one for a making your own cheap camera flash diffuser

http://www.instructables.com/id/DIY-Gary-Fong-Lightsphere/

Later,
Don

[spadez]

Thank you for the info Jon, and I'm sorry to have moved this thread off topic again!