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

[JonMarsh]

Welcome to HT Guide!

Well, a TMM is "officially" in the works, has already been modeled. But you're up against a problem with any 2.5 way TMM with regards to load impedance if your amplifier doesn't like 4 ohm loads.

Speaking of load impedance, hear's the plot on the MT's, taken just before I left for Sacramento yesterday to deliver these:



Red is the impedance curve in ohms, cyan is the phase. These are about as benign a load as you can imagine, even for tube amps. In the upper bass they do dip briefly to the 6 ohm area- this is a function of the driver impedance curve- this would probably be the limit for your Onkyo.

A two driver TMM will have about 1/2 the impedance - i.e, dip to about 3 ohms. Note the tuning on the bottom end- the impedance minima between the porting peaks is at about 36 Hz- this is the point of maximum port output. I normally shoot for an alignment that has an anechoic gradual taper/roll off from 100 Hz to box Fb, down about 6 dB at Fb, so that when people do the usual thing putting them a bit close to the wall than is acoustically ideal, they don't get all boomy and zaftig on you in the bottom end. THAT said, there is a substantial constituency out their that "prefers" zaftig bottom ends (on both speakers and women), and taste is taste, whos to say I'm wrong? Those people will find the bottom end a little light for their taste.

At my relatives, we put them where they wanted, next to the flat panel on a big furniture pieces, and things were just fine- was able to take off the big bass and treble boost their previous speakers had. And they were pretty amazed at how nice these sounded, even way off axis and in the next room. Put some Sting and Level 42 on, cranked it a bit, and big grins all around.

Mission accomplished. (something familiar about that phrase..... gotta figure that out). And Scot now will likely come to the Northern CA DIY in Roseville.

With regards to the TMM, I'm trying to arrange a collaboration between the doc and ET; maybe try something a little more heretical as an additional alternative- say, a 2.5 way with the same upper range drivers as this MT, but a Scanspeak W22 with flux capacitor for the 0.5 speaker, throw in a little more excursion and output capability, but keep the enclosure size down. Would that make it a TMW 2.5 way? Could be a new category....

[spadez]

Thank you for getting back to me. 3Ohm is definitely too much for my amp. I just looked at my dads B&W floorstanding 2.5 way and they are rated at 8Ohm. How did B&W manage that, and why cant I do the same on a DIY build?

[ThomasW]

Because B&W builds their own 16 ohm drivers. There are very few 16 ohm drivers for DIYers

[JonMarsh]

Jantzen has some 12 ohm 6-1/2" drivers, I have two pairs of those, it would be possible to design a TMM with those, but you really probably don't want to go there, as they're about $200 a piece. So, that's $800 for a set. If that interests you and is a better route than upgrading your Onkyo, let me know- would not be that much work to whip up a crossover design for a TMM with them.




These are good drivers, but not as low distortion in the bottom end as the ER18RNX. Not quite as extended in the top end either, they're a bit harder to work with. Low HD2, compared to many other 6-1/2's, a very symmetrical motor structure.

One of the advantages of a TMM with more conventional impedance drivers is the improvement in voltage sensitivity-

Consider an MT made with the Jantzen 12 ohms - nominal sensitivity per driver is 86 dB for 1W (not clear if they mean 1W dissipation, or 2.83VRMS). Put in baffle step compensation, that drops to ~81 dB to 80 dB. Parallel two drivers, and you get a total 6 dB increase in voltage sensitivity, which means you're up to about 86-87 dB for 2.83 VRMS. With the ER18RNX, the base driver sensitivity is 88 dB, so you can wind up with a system sensitivity pushing 88 to 89 dB for only $158 in woofers per side, not $400. But you'll have lower load impedance.

So, if there's interest, I'll post a TMM design with these drivers- but my experience is that most folks on the forum aren't quite as willing as I am to spend on pricey drivers for specific performance advantages like a high impedance/sensitivity product. These will handle some power, too- 3" voice coils on a 7 midwoofer.

Somewhere you have to have balance in the design. One might even argue that the Modula MT MkII is balanced a bit oddly- it has enough refinement and low distortion that it is sufficiently revealing of the differences between 1K DACs and $3K or $5K DACs- driven with a Tascam pro transport, Berkeley Alpha DAC, and Ayre K5 with Cambridge Audio 840W, it sounds QUITE a bit better than with a Technics receiver and CD player (the "target system" they were delivered to). But they even on that older Technics system, they sound way better than what they replaced. And construction cost is, IMO, reasonable for "high end" compact speaker. It's just that if you can upgrade the other bits, you keep getting back more of the music as you do so. That's the kind of thing I like to do- I'm not interested in "cheaper" designs just for being "cheaper". This is about as good a speaker as I know how to design that fits in a 3/4 cu ft enclosure.

[spadez]

Thank you for the reply, and im sorry to have hijacked your thread, I didnt think it was going to be a problem with my amp unfortunately.

I think I may be better off in the long run upgrading my amp though, ive made a post for amplifier recommendations to see how much that would set me back.

[Jonasz]

Why not go with the 16 ohm version of the SS Revelator? They don't come cheap though... :B

http://www.scan-speak.dk/datasheet/pdf/18w_16831g0.pdf

[---k---]

Hey Jon,

Could you maybe educate me why it seems like most of the better drivers and speakers end up being 4 ohm? This seems to be common in the retail world also. It would seem that 8+ ohm would be easier for amps, ect. So, why don't we commonly see 12 as 16 ohm drivers? Is it more costly or difficult to make them?

[spadez]

Why not go with the 16 ohm version of the SS Revelator? They don't come cheap though...

http://www.scan-speak.dk/datasheet/pdf/18w_16831g0.pdf

I couldnt find a price, whats the damage on that?

[Bear]

I couldnt find a price, whats the damage on that?

>$200. However, given that Jon tested a pair of Revelators prior to selecting the ER18NX, I doubt he's looking to swap one 18cm driver for another. The 26cm woofer is >$300 if you buy full retail.

[JonMarsh]

Hey Jon,

Could you maybe educate me why it seems like most of the better drivers and speakers end up being 4 ohm? This seems to be common in the retail world also. It would seem that 8+ ohm would be easier for amps, ect. So, why don't we commonly see 12 as 16 ohm drivers? Is it more costly or difficult to make them?

One of the things affecting driver bandwidth is something as simple as VC inductance. Higher impedance drivers are basically smaller wire with more turns, distributed in about the same VC length. More turns means more inductance, less bandwidth; and it also can alter Qes (electrical damping) in unfavorable ways. Then too, there's the whole sensitivity thing; if you're making an MT, a 4 ohm driver will have higher sensitivity, though not matching two 8 ohm drivers. so, for example, a HiVi M12 is a 4 ohm driver, with about 92-93 dB sensitivity. Done at 8 ohms, might only be around 89-90 dB, maybe even a bit less. BL product is a function of ampere turns in the gap as well as the flux density in the gap. You can certainly connect the dots and see the trendlines emerge when you compare the SS 26W/12867 and 26W/8867 and 26W/4867. (that's if you like entering the delusionary conditions of evaluating or comparing published SS T/S parameters- another topic altogether!!) Wilson and others use the aluminum cone lower impedance woofers in singles to good effect. Because of the coupling effects using multiple woofers, and the special pricing, the 26W/12867 was attractive to me, though you can match the output capability and better the sensitivity with a pair of 8867- but not for $390 a pair!! and not as easy to drive in a passive crossover! You gain about 2 dB sensitivity, but with a lower impedance load. 2dB may not sound like a lot in an offhand fashion, but that's about 2/3 more output. (3 dB being double the output power)

Also, the T/S of the 12867 is EXACTLY what I wanted (no matter that the actual Qts of the 8867 is probably close to that anyway), and the sensitivity difference gives me more options for playing around with the midrange crossover- try some techniques again I used to good effect in the 90s- i.e., using an inductor for the high pass control of a midrange or tweeter.

Scratch your heads over that one for a while. :W :B

As Bear notes, one could do that- but then the net sensitivity would be about the same as for the ER18RNX MT, the LF output would go up by 3 dB, and it would cost over $300 more per cabinet to build... personally, the value proposition is lacking for me, though I can understand it still might be attractive for someone else- say, with a 100W/channel tube amplifier, cause then we'd have plenty of power handling, and a very benign impedance curve. Me, I've got too many amplifiers sitting around that are capable of arc welding for all practical purposes (i.e., 2 ohm stable) to be worrying about a 4 ohm loudspeaker. I realize that's not the case for everyone, but then I don't often hear 8 ohm only solid state amps I like the sound of anyway.

[spadez]

May I ask one more thing before I disappear out of here. This is my situation. I have just brought a 607 onkyo amp. Im being told that it cant handle 4ohm nominal. This pretty much rules out any high end TMM design. These are my options:

1. Would you advice that I sell my amp and upgrade
2. Persue your TM version on here
3. Go for the TMM version, cross it over at 80Hz (I have a sub) and hope my amp can take it

Basically it comes down to, how much difference do the TMM designs really make, and are they worth the extra money? It should be noted that my room size is 5x5m.

[cjd]

The Onkyo 607 should have no trouble with 4ohm speakers though... Who is telling you it can't do 4ohm? In fact, I think it only has 4ohm and 6ohm settings (you set it to 6 for anything 6 and up)

[JonMarsh]

It really depends on how loud you expect to play music, and how low. A conventional TMM will have 3 dB more LF though ~500 Hz output capability. That's not huge, but it is double the acoustic power. In a room 5m X 5m, these will play loud enough that you can't talk over them. Not at 30 Hz of course, but normal music, pretty decent.

Are you going to load all the channels in this unit? a Full surround? or just do front and sub, or front center and sub? If you plan to fill out the configuration and include a sub, I don't think you'd miss anything just going with the TM's.

[spadez]

The people on hometheatureshack said most likely my amp would cut out if I tried to play music loud on my 607 with 4ohms. I would like to hit 100-110db if possible. I have a sub that is crossed over at 80hz which should take some strain off.

My plan was to start with fronts and center and two small surrounds (8ohm) and then add on 8 ohm rears if my amp could take it. What do you recon, is that a bit much for my amp?

It's mostly going to be used for listening to music loudly.

[Face]

Buy a 706/707 and an external amp.

[cjd]

Amp isn't going to be your problem at 110dB entirely, it's going to be the whole mix. You need lots of good clean power and fairly sensitive speakers to hit that level without it just going all to distortion.

[Bear]

The people on hometheatureshack said most likely my amp would cut out if I tried to play music loud on my 607 with 4ohms. I would like to hit 100-110db if possible. I have a sub that is crossed over at 80hz which should take some strain off.

My plan was to start with fronts and center and two small surrounds (8ohm) and then add on 8 ohm rears if my amp could take it. What do you recon, is that a bit much for my amp?

It's mostly going to be used for listening to music loudly.

Going off of published T/S parameters, the ER18 will take 60 watts in a 22 liter box tuned to 45 Hz while producing just shy of 106dB. This is at Xmax (6mm). If you push it out to Xlim/Xmech (11mm), then it takes a ton more power. I think the MT should be fine here if you are really worried.

Amp isn't going to be your problem at 110dB entirely, it's going to be the whole mix. You need lots of good clean power and fairly sensitive speakers to hit that level without it just going all to distortion.

Agreed. This all depends upon the insertion loss of the XO, among other things vs. the Unibox model, above. Realistically, 110dB isn't comfortable for long periods unless you've already done so much damage to your hearing that worrying about low distortion speakers is an exercise in wishful thinking.

For me, I'd want something that can handle dynamic range cleanly into the 100s, but I'd never listen there for long periods.

[JonMarsh]

Then, too, if you have multiple speakers, listening to surround, that adds up to the dB. With a sub cutting in at 80 Hz, the MT's will have plenty of output. This driver combo is so clean you do could have some issues with playing louder than is really "safe" or wise, long term- for the sake of your hearing. They probably won't show strain before you're in the danger zone, as Kenny Loggins might say.

If you had a larger room, I'd consider upgrading speakers and amp, but in the room you have, with the advantage in loading the waveguide gives the tweeter, and with using a good sub from 80 Hz down, I'd worry about other things - like the quality of your sources. The TMW 2.5 way version I'm considering is a bit like putting a small sub in each cabinet, with a 9 mm Xmax Scanspeak 8". It'll still be a mini-monitor by Paul Wright's standard, but in a 15 X 15 room for music, it should be fine.

[---k---]

Jon,
Thanks. That was a helpful answer.

[JonMarsh]

You're welcome, Ryan- I try to provide helpful answers even when it seems like I don't - because I'm trying to provoke independent thought! :W

OK, only task left for this thread is finishing the document for the PDF write up. I hope that will be wrapped up by the end of the week. Then we'll deep six this thread or move it to Missions accomplished, and get back to some other neglected projects, some which may receive substantial refreshes.

The Modula MT MkII are now scheduled to be demo'd at the Northern CA DIY in April 24, after which they'll have fulfilled Ryan's criteria to be added to his list. :W I already have a commitment to borrow them back on that day, and Cheryl's son Scott will most likely attend the DIY meet, too.

And for Hank, I promise to do my best NOT to design another 7" two way for at least another five years!

[parodielin]

Jon,

Cannot wait for your PDF and of course evaluating whether I have the skill and tool to mount the waveguide or wait for the non-wave version.

I caught on your post earlier mentioning this would be "the speaker" you'll bring to the market if it's the dream. Aside from risks and amount of work, just curious, why not other "proven" popular designs like NatP and Modula MT?

Your welcome, Ryan- I try to provide helpful answers even when it seems like I don't - because I'm trying to provoke independent thought! :W

OK, only task left for this thread is finishing the document for the PDF write up. I hope that will be wrapped up by the end of the week. Then we'll deep six this thread or move it to Missions accomplished.

These are scheduled to be demo'd at the Northern CA DIY in April 24, after which they'll have fulfilled Ryan's criteria to be added to his list. :W I already have a commitment to borrow them back on that day, and Cheryl's son Scott will most likely attend the DIY meet, too.

[davey_m]

And for Hank, I promise to do my best NOT to design another 7" two way for at least another five years!

Please don't try too hard to keep that promise, they seem to get better all the time! And new drivers appear all the time.

[cjd]

I happened to notice the Emperor glancing over the Anarchy the other day. . .

[JonMarsh]

Jon,

Cannot wait for your PDF and of course evaluating whether I have the skill and tool to mount the waveguide or wait for the non-wave version.

I caught on your post earlier mentioning this would be "the speaker" you'll bring to the market if it's the dream. Aside from risks and amount of work, just curious, why not other "proven" popular designs like NatP and Modula MT?

Those older designs are good designs, in my opinion, considering the effort and drivers available and type of construction.

BUT, excellent is the enemy of good... and there's always the opportunity for newer designs to stand on the shoulders of what has been learned in the past, and with the right concepts, build on it substantially in new ways.


Here's my take on this with regards to the Modula MT MkII versus the older ones, and the Natlie P.

Design/Performance advances for the Modula MT MkII:

• A carefully implemented waveguide loading improves lower frequency range dynamic capabilities of the tweeter without any side effects reducing fidelity in other regards
• A carefully implemented waveguide/tweeter combination can result in more consistent off axis loading and behavior of the system, including in the frequency range above 10 kHz, due to the direct waveguide/tweeter interaction
• A carefully implemented tweeter/waveguide system appears to substantially reduce early diffraction effects from the cabinet that bear on tonal transparency and imaging in the tweeter's operating range.
• The motor of the ER18RNX, while not "state of the art", offers a good balance of performance and cost with low frequency distortion rivaling drivers costing 2x to 3x.
• The bamboo paper cone of the ER18RNX provides extended well damped performance in the upper ranges, allowing development of a relatively simple crossover with good amplitude and phase matching for the crossover acoustic target all the way out to 10 kHz, minimizing phase error in the primary crossover overlap range (+/1 one octave).
• The Waveguide provides acoustic offset of the tweeter orgin, so that tricks don't need to be played with the transition slopes and phase, as is necessary for baffle mounted tweeters to conventional woofers, which supports hiting an exact acoustic transfer function with little compromise.
• For all of these reasons above, I will not publish a waveguideless version of this design, as I feel there are too many performance shortfalls
• The actual construction of the waveguide version is quite simple as realized, requiring nothing in the way of exotic tools (unless a router or a vegetable paring knife is exotic!)

On the other hand, what are the advantages of the older designs?

• Less expensive drivers
• Can be built without a router with acceptable performance

The NatalieP is in particular a value proposition leader for it's day, with the added output capability from dual midwoofers, relatively modest driver cost, a very balanced presentation and good detail due to the strange series/parallel LR3 crossover (that's the only way it can be called, though Linkwitz never described an LR3 alignment- it's not a B3, though it isn't a "pure" LR3 either, lying in between the two in order to get a taller crossover lobe). NatlieP's have simultaneously won budget class and unlimited class at some DIY meets, which speaks to the integrity and performance of the design.

But it doesn't mean we can't do better in the same general size and price range.... and I mean more than a little bit better, with regards to things that are quite important to me, and may not be so obvious if you're driving with just a budget HT receiver and CD player.

I hope this is clear without being overbearing.

With regards to some "competing DIY designs", I'm hearing scuttlebutt that the reason ET got sent back to the woodshed on the Nascent by the Chancellor is because of the "threat" posed by the Modula MT MkII.

I dunno, seems like that's taking DIY rivalry to an unnecessary level! :roll: :W :rofl:

[---k---]

You're welcome, Ryan- I try to provide helpful answers even when it seems like I don't - because I'm trying to provoke independent thought! :W

I understood about 1/3 of your post above upon first reading. A little thinking about it brought me up to 1/2. Your posts are often ones that when I go back after a few days usually understand most of it. If I didn't have to think about it for a few days, I'm not sure I would understand it as deeply. So, you're doing a good job, Mr. Professor. :T

[parodielin]

So no none-waveguide MKII. h:

I should ask fewer question and read more books before I can understand all responses. It's a pity that the beautiful metal flange of the HDS will be covered by the waveguide.

Off to read Speaker 201 and the cook book...

Those older designs are good designs, in my opinion, considering the effort and drivers available and type of construction.

....

[spadez]

Im am going against advice and im going to return my 607 and purchase a refurbished 807 or 707. From here I can try the 4Ohm speakers, and if there are problems, Ill purchase an additional amp to drive them off the preouts. This may seem like a waste, but ive spent a lot of money on this build and I dont want to be worrying about it shutting off, or limiting my speaker builds (and the volume, for that matter). I hope to move into a bigger house soon and im not sure the smaller MT's will be up to the job of having the "wow" factor in the same way that larger builds might.

Anyway, long story short, I look forward to your PDF's

[JonMarsh]

Well, that's a little pain in the short term, but for the long term that's probably a very good plan.

[evilskillit]

So what mains are you going to end up building Spadez?

If this is what it takes to be able to have your pick of the litter of diy designs I think it'll have been worth it for you.

[spadez]

Hi Evilskillit, I think I will probably be going with Jon Marsh's new Modular TMM design for my fronts (if he has decided these are definitely going to see the light of day?). Im really excited to see how they turn out, and in terms of budget they are right at the top end of what I can afford (especially since im buying a new amp).

For the center and rears im not sure really, but I wont have the time or money to think about it for a little while

[mackintire]

So will we be seeing a Modula MTM MKII tower?

[JonMarsh]

Hi Evilskillit, I think I will probably be going with Jon Marsh's new Modular TMM design for my fronts (if he has decided these are definitely going to see the light of day?). Im really excited to see how they turn out, and in terms of budget they are right at the top end of what I can afford (especially since im buying a new amp).

The PDF in preparation will include a complete crossover design for the TMM, based on the data I've collected- so someone could build it right away - basically, they'd need double the volume, and in fact could even stack two of the PE boxes together! (which I have done for test purposes). This will be a 2.5 way, NOT an MTM or TMM with a straight two way crossover. Costs a bit more in the crossover department, but this way the driver spacing presents no issue with driver blending or power response. Think of it as a close relation to Zaph's TMM, but with different drivers and only perfectionist version of the crossover.

So will we be seeing a Modula MTM MKII tower?

Not exactly. The TMM is probably the closest to that.

I hear the Nascent is being "re-directed" and will remain an MTM, but use a waveguide loading for the tweeter on an LBL baffle. But that's not a Modula MTM, strictly speaking, as it's dual 5", not dual 7".

The reason I won't be building a Modula TMM right away myself is because I'm working on a similar but slightly different concept, a TMW 2.5 way. Yes, asymmetrical woofers- did that originally with the SLAMM clone, for which the Wilson Audio speaker did the same things. Can be good reasons for doing that.

In this case, the intent is for the driver volume to be the same size for both the M driver and the W driver, but different drivers and alignments, and some tricks that allow the smaller enclosure size for the W while being able to use a larger, longer throw woofer capable of more output. I'll be testing part of the concept this weekend, to make a go/no-go decision on that. If it's a go, it should be ready by the Northern CA DIY meet at the outside, as all the drivers and most crossover parts are on hand, and materials for the special front baffles are on the way (yes, more LBL... from a source some may find humorous).

Who knows, someday we may all look back on 2010 and say, "Yeah, that was when Jon was going through his waveguide and LBL phase... remember that?"

There is another higher end version of this concept in development, more a true three way, the Modula Xtreme. It is also targeted for the Northern CA DIY meet in April- all the major parts are on hand for it, too, and a test waveguide is assembled- the head unit will be tested this weekend, too.

[---k---]

Jon,
Why don't you scare everyone and publish a total (estimated) cost for the drivers and crossover for the various projects.

[JonMarsh]

Jon,
Why don't you scare everyone and publish a total (estimated) cost for the drivers and crossover for the various projects.

Oh, that would be truly Evil, wouldn't it, in capital letters? That would more be ET's department.... :P

The PDF due this weekend will include a basic BOM, which of course can be altered by substitutions in the crossover. There's a lot of freedom there, but then you get what you pay for.

Also, some folks will have trouble understanding at first why a cutting board/bread board might go in a speaker, but I suppose I should include that for full BOM disclosure? :rofl:

It's actually a cost saving measure, for those who want to upgrade but don't have the cojones to buy a board- and can spring for a bread board or two at Target or Amazon.

[villastrangiato]

Oh, that would be truly Evil, wouldn't it, in capital letters? That would more be ET's department.... :P

The PDF due this weekend will include a basic BOM, which of course can be altered by substitutions in the crossover. There's a lot of freedom there, but then you get what you pay for.

Also, some folks will have trouble understanding at first why a cutting board/bread board might go in a speaker, but I suppose I should include that for full BOM disclosure? :rofl:

It's actually a cost saving measure, for those who want to upgrade but don't have the cojones to buy a board- and can spring for a bread board or two at Target or Amazon.

Doh.....here I thought that was strictly a slide out Benihana chopping board option for those who like to listen to music while preparing sushi.........ooops...

[JonMarsh]

Well, see, I think some critical parts will work better made with a really strong, stiff material that the fasteners just lock down real tight, and that machines well and would have hardness and stiffness properties better than maple. Maple was good enough for Les Paul, but this is a new century, and Bamboo can be replaced easier and quicker... technically, it's more "eco".

Besides, I like the grain. :W But you are correct CJ, because you can get 5 packs at a good price from Amazon, so you can use two or four in your speakers, and keep one for your kitchen!!



I used some left over scraps for the tweeter mounts in this pair; the next two Modula builds will have full LBL front panels. There's a nice larger one 3/4" thick about 12" X 18" that's perfect for the full Modula MT, and this can be bought online as well as at a local Target store. :B

Very nice material....

BTW, those 1-1/4" Streaker screws are now replaced with 1-1/2" Forum square drive black oxide screws, sourced from Woodcraft.

[savage25xtreme]

count me as 1 looking forward to the AudioWorx webpage and PDF files. :T

[evilskillit]

Color me interested. I saw that you put AudioWorx in your sig, but didn't see a link so I assumed maybe that was just what you were calling your collected works. If you actually throw up a web page hosting all that stuff it will be fantastic.

[igy137]

Lbl

I used some left over scraps for the tweeter mounts in this pair; the next two Modula builds will have full LBL front panels. There's a nice larger one 3/4" thick about 12" X 18" that's perfect for the full Modula MT, and this can be bought online as well as at a local Target store. :B

Very nice material....

Jon, Is this LBL that good? Surprisingly enough for me, I think I found it here in Switzerland (this country is really not a DIY heaven), similarly priced as birch plywood. As I felt it's a bit lighter than birch plywood, though I might be wrong. Maybe some sandwich of these materials would be nice against resonances?

[---k---]

BTW, those 1-1/4" Streaker screws are now replaced with 1-1/2" #2 square drive black oxide screws, sourced from Woodcraft.

I bought some of those myself last Saturday!

[cjd]

LBL is amazingly stable (I have it as flooring, somewhere around here are a couple snapshots) and hard, while also being quite stiff. It is unquestionably good stuff for speakers, but it is still priced rather crazily for lumber dimensions, not to mention sheet goods (you CAN get 4x8 sheets - check out Teragren)

[JonMarsh]

Yeah, no question it is a premium material, but my basic thinking is that it is most critical for the front panel and driver mounting; as you get away to other parts of the cabinet which the drivers don't directly interact with, and as pressures fall off, and likelihood of modulation falls off, not as big a deal.

Jon, Is this LBL that good? Surprisingly enough for me, I think I found it here in Switzerland (this country is really not a DIY heaven), similarly priced as birch plywood. As I felt it's a bit lighter than birch plywood, though I might be wrong. Maybe some sandwich of these materials would be nice against resonances?

It's about 20% harder than maple, is pretty dead itself. I've used it embedded in front panels, and have been experimenting with it for complete front panels. A good hint to the properties, is that when you use a good wood screw or even drywall screw to mount a tweeter, directly threaded in, it locks down more like threading a machine screw into aluminum than a wood screw into MDF, which comes loose and wears pretty quickly if you have to take it in and out a couple of times.

I usually buy it from a specialty wood supply place for larger pieces (like 4' X 1' X 3/4") but 3/4" thick pieces are available as cutting boards in sizes suited for smaller speakers, and while you can buy them in local department shores in the kitchen goods section (Target, for example, as I did last weekend), here you can find the same brand/model discounted online through Amazon, literally in 5 or 6 pack solutions. As it's hard to find in wood shops, this seemed a reasonable alternative for some projects.

So, for example, in a next project, a small size cutting board will become both the waveguide tweeter mount and the cross brace for the front panel. A bit indulgent, I suppose, but not nearly so much as phenolic sheet or aluminum, for example.

[---k---]

Jon,
You got any accelerometer data to back up those claim? It seems like an accelerometer would be right up your testing alley.

[villastrangiato]

Jon,
You got any accelerometer data to back up those claim? It seems like an accelerometer would be right up your testing alley.

If he doesn't, I'll loan him my integrator/disintegrator particle accelerator.....

[JonMarsh]

Wish I did, I have an accelerometer SOMEWHERE in my storage unit, but I could spend a month of weekends looking for it before finding it in all likelihood.

Have you ever listened to a Magico or Rockport or YG Acoustics speaker? They do some audible things that can't be ascribed to the drivers they're using- same with Avalon. Similar thing with the Ardent versus the MDF construction Modula MT versus an Ardent- but the Modula has more of "it" in the upper range than the the bottom, yet it's the same woofer (just one) with the same volume and alignment tuning.

On one level, I don't care about convincing anyone of the value of building front panels this way- heck, if we had competitive DIY meets out here the way they do in most parts of the country, I suppose I'd keep all these ideas, experiences, and beliefs "secret" so I could have a leg up...

ThomasW picked up an accelerometer last year and is supposed to loan it to me. To do a scientific study, I'd have to take the time to build sets of cabinets both ways, you know?

I have a simple evaluation technique. I cut a 1" wide strip of 3/4" MDF 18" long and try breaking it across my knee- it breaks easily, and the material crumbles at the fracture into something of a mess. I try the same thing with LBL, and I just really hurt my knee... a lot... with no damage to the LBL.

MDF is relatively cheap and easy to work, but that's the main thing going for it. I'm not a fan of ply having worked with it a lot, either, though I think BB ply translam is something I want to try. Actually, what I'd like to try sometime, maybe before the end of the year, is a translam enclosure with LBL front panel (1-1/2" thick front). For a box speaker, that might wind up being my preference.

The next two projects will use 1-1/4" front panels from LBL. Come to the Northern CA DIY in April and we can see how that works out. :W