MTMs for my brother this time!

[PMazz]

Here's a sample of cherry veneer using different concentrations of the lye/water solution. The bottom has been clear coated.

I start with a mild solution and work my way up, drying in between samples to let the reaction take place. You apply it like stain, using a rag, and you must wear gloves and eye protection.


Image not available


Pete

[ThomasW]

That's quite interesting Pete, it really does give the appearance of 'aged' Cherry..... :wink:

[Ten 99]

Pete, that's a great illustration above. I was at Lowes last night buying some paint, and I picked up some magazines while waiting on the mixture. The current Fine Woodworking issue has a small article in the back of the magazine (last article) by Jeff Jewitt, going over (timely enough) this same type of thing. It's the Feb '05 edition. Actually, the article covers three seperate techniques:

Ageing - He uses a sodium carbonate mixture (but mentions lye mixture like you did). This mimicks what UV and Oxygen do to wood (darkens the pigments).

Graying - He uses a ferrous sulfate mixture. This gives the wood a weathered look and puts a light gray patina on the wood. (Don't care for this myself).

Blackening - He uses a "Iron Buff" mixture. This turns the wood a darker gray color, turning some species to almost black look. For this he shreds some steel wool into a pint of white vinegar.

Pete, I actually have very little experience with shooting finishes. I recently purchased a top feed HVLP conversion gun. It is a cheapie, since it is my first gun to play with. This gun has actually received many positive feedbacks on woodnet, where several have tried it and said that it's a great gun for the money. It's a Harbor Freight (I know, I know) #43430, and went for about $39 on sale. Eventually I would like to have a gun to shoot some latex, one to shoot lacquers, one for enamels, one for stains or dyes. I am interested in the pressure pots systems. I've seen lots of these on some government auctions before. How do these work? The gun's material feed is hooked to the pot, which is pressurized to feed the materials to the gun, and then you have your normal air supply to the gun as well to atomize the spray?

[Dennis H]

Pete, a question about aging with lye. If you do a medium treatment, will the wood still continue to get darker with age due to UV, O2, etc.? Do the color changes happen more slowly after treatment? I'm trying to figure out the advantage over using a stain. Is it that you get the wood past that first darkening where it can change color with a few hours in the sun?

[Ten 99]

Not Pete here, but from my worthless POV, a stain will lay on top of the wood and have a tendancy to cover up the grain and beauty of the wood. Will the wood continue to get darker with time. Yes, but it will take a long time. If Pete had taken a piece of this veneer and placed it outside in the sunlight, it would have eventually had this effect as well. The process is more quick at first, and then slows down over time. Once a finish is applied, it slows it down some more (less O2 getting to it). There is also the aspect of less UV inside of a house, etc. I much prefer the look of the Cherry darkened with the Lye solution as opposed to a stain. How dark you like depends on the strength of the lye and water solutiton you use, and how many times (coats) you apply the solution.

The darker a stain is, the more it is likely to cover the beauty of the wood's grain. Pete used a stain on the cabinets above, after doing a lye solution on the cabinets. I'm not sure how dark the stain itself would have been without the lye solution. My guess is that it would have been about half as dark. Fortunately, the stain didn't cover up the beautiful grain and figure in the cherry he used on his brother's cabinets. It's always best to test on some scrap first. When appropriate, I like the use of dyes more than stains. A lot has to do with the wood species you are working on to begin with.

[Dennis H]

I guess I should have been more clear. I was referring to transparent penetrating stain - basically dye in some oil - like the Watco Pete used. It enhances the grain rather than obscuring it.

So Pete, since you used both lye and stain, it looks like you were just using the lye to get the wood past the stage where the color changes rapidly so it will stay the color you stain it for much longer. Or is there something else going on?

[PMazz]

The darker the base is, the less you have to add to it to get the desired color you want. With the lye solution, it has to be a pretty strong solution to really get dark, and there's no going back. I usually opt for the conservative approach which can always be made darker, tinted one way or another.

Pete

[PMazz]

A pressure pot system consists of a pressure pot (obviously) with a dual regulator mounted to it. One regulates the pot pressure (fluid feed pressure) and the other the air going to the gun. Usually the pot is run at 10psi and the gun 40 (for low viscosity materials). Using a standard gun, the air pressure into the gun is what comes out the end. With HVLP, this pressure is reduced by the gun to ~10psi, which reduces bounce back and overspray. So far, the only difference from a working point of view is having to move a little slower with the gun and some reduced atomization.

Pete

[PMazz]

I finally got them home! Now I just have the crossovers to install and I'm ready to critique Jon's work .

Man, I really like the look of those HiVi M8s.


M8 MTMs

Pete

[Paul H]

I finally got them home! Now I just have the crossovers to install and I'm ready to critique Jon's work .

Man, I really like the look of those HiVi M8s.


M8 MTMs

Pete

Nice work Pete.

I've never made grills for mine - I think the M8's look fine without them.

Paul

[PMazz]

I do too, but he wants grills. In fact, now that he's seen them, he'd prefer black fabric. I agree.

Pete

[Evil Twin]

Everyone likes black, don't they?

[PMazz]

Well, I got the xovers installed. As usual, I used wire nuts on the Lpad for the inevitable tweaking and measuring to take place. Only 1 speaker, mind you. No sense wasting time doing both til they're right.

Ok. Let's plug it in and give a quick listen while I set up the test gear.....UMMM.....test gear?.....Tweaking?.....I don't think so.

I plunked down in my chair and made sure the sub was off. OK, I guess these do have pretty good bass. Steely Dan- Two Against Nature. Wow, listen to those cymbals. Damn, the sax sounds sweet. Hell, EVERYTHING sounds damn fine!

OK, might as well do the other xover. These aren't getting any better than this. :T

Now they're both running. Damn Jon!!! These are some fine sounding speakers! I don't know how the other tweeters sound with the M8s but the Vifas are very nice. The overall clarity of the system is amazing. Pumping up the volume and no sounds of stress.

I could easily live with these full time. Great work Jon!

Updated with xover.

MTMs


Pete

[ThomasW]

After helping a friend built the M8a-MKIV, I knew that a MTM version would be outstanding. However it took a gun to Jon's head to get the design.

Now it's his 'best selling' product...... :B

[Paul H]

Another satisfied customer for the gurus - they are sweet..

Paul

[PMazz]

Well, to say I'm impressed is an understatement. An incredible 2-way design. I usually don't care for ported speakers but these are fine.

So Jon doesn't care for MTMs or was he just pulling that "I'm too busy" actually working? Either way, an excellent idea on your part.

Pete

[ThomasW]

Pete,

Jon likes MTM's, witness the Arvo, X1-Slamm and other designs.

He just wasn't in the mood when I hit him up to create the original MTM for Tibor. But I knew that they'll be toast no time if we used a single 8" for HT.

Often we fine tune ported designs with a mat of poly behind each woofer. Start with 2" thick, approx 10"-12" square piece (we use the bonded material instead of the loose fill). Place it directly behind the woofer (force it through the hole and making a 'cup' for the magnet to fit in.)

Too much and the bass output drops, too little and it isn't tight. (basically similar tuning technique to adding damping to the subs, except much less material is used.)

[JonMarsh]

Pete, I'm pleased that these are passing review by the Mazzter...

This is a fairly proven design at this point, quite a few sets built, actually.

For the ported version, the key is an alignment that's not tuned "flat" anechoicly, but tunned lower, to achieve a shallow taper so that the room gain lifts it back close to flat. If one tunes for flat anechoicly, say, a standard B4 alignment, then the'll almost always be heavy sounding in room in the 40-50 Hz area, maybe even higher.

The Vifa's are very respectable performers in their price range- there's a number of reasons you see these in quite a few commercial systems. However, the SS9800, plus cap upgrades, takes it to another level in the top end. My own MT MKIV's have the SS9800; I realize they're a little pricey, some would say, but remember the one of the earlier versions (the MKII) used Accuton tweeters and Eton woofers, so I've been trying to mderate the cost issues while improving the performance. (The MKII's are in my HT setup, due to be replaced by the Modula MTM's.)

Doing a good MTM isn't as easy as some folks think, but the special crossover of the M8 series makes it almost a minor upgrade. The Arvo takes it a little further...

[TacoD]

For the ported version, the key is an alignment that's not tuned "flat" anechoicly, but tunned lower, to achieve a shallow taper so that the room gain lifts it back close to flat. If one tunes for flat anechoicly, say, a standard B4 alignment, then the'll almost always be heavy sounding in room in the 40-50 Hz area, maybe even higher.

I read an interview with mr. Wilson (from Wilson Audio, Hifi+ magazine), that he tunes the ports of his speakers differently for the European market, because the different kind of building materials we use in Europe. Have you pointers how to tackle this, my room consists of lots of concrete .

[JonMarsh]

What that means to me, is that there will be rather strong LF room re-inforcement, because the walls and floors won't flex appreciably, and hence, won't absorb the sound as much.

What I would do would be the same tuning approach, regarding box Fb, which can be seen easily in Unibox, for example, but increasing the internal damping to lower output a little more. As Thomas describes above, this can be fine tuned with damping sheets placed behing the woofer (NOT near the port entrance). Unibox only has rather crude steps for modeling this via push button, but at this stage, modeling is probably a moot point, when you're adjusting the final cabinets. I'd probably do that by inserting or removing the damping material in the cabinet, and looking at the LF response from 200 Hz down to 20 Hz in room at the listening position, with a narrow band RTA/FFT setup. The idea is that you want to get the cabinet damped enough that the cabinet roll off and room gain are inverse functions in the lower bass, at least until you reach the shelving frequency for room gain.

Also, LF source localization must be done carefully; typically with golden mean ratios from the nearest adjacent boundaries (floor, rear wall, side wall).




The M8ta reflex design is an example of a tapered response,



And the thread ThomasW started last February 2004 has a lot of good discussion relevant to this topic:

Ported M8a MTM Thread

[TacoD]

Thank you John, I have made some speakers with this overdampened type of alignment. But like you said, sometimes the room is still adding to much LF. I will try some extra wool behind the woofer.

[PMazz]

Jon, I thought you might like to know....

Since setting everything up for my brother, he has called twice and on both occassions, has complimented the sound quality of the speakers. I thought you might like to know. Thanks for the wonderful design and all the help along the way, it is much appreciated.

And damn if I didn't remember to take some pics..... ops:

Pete

[JonMarsh]

Thanks for the kind words, Pete, and I'm glad to hear things worked out smoothly!

No pics? Sigh.... I know the feeling... BT, DT.

~Jon

[PMazz]

I asked my brother to take some pics and send them to me. We'll see if he remembers . I'll keep bugging him if he doesn't.

I was down there working for 5 days to help get him settled in to his new digs. He bought a 36" Sony TV while I was there, along with a new DVD player, as we discovered it had died during the move. He had already picked up a Pioneer 1014 reciever to drive everything. Not a bad deal for an inexpensive piece. I also installed a couple of Dayton coaxial in-ceiling speakers for surround use. I still have to make him a sub using one of my old Tempests and sub amp.

On a side note: He always made fun of my remote clutter..... Now he's paying! I had to leave written instructions on how to operate it all. And he thought I was nuts to spend a couple hundred bucks for a good remote....

Fun, fun, fun!

Pete

[Jam_Master_J]

Hi Pete,
Those are some nice looking speakers you've done up for your brother, he's gotta be thrilled with them

Anyway, just a while ago I planned out the cuts for the set I was going to build. The set will be more or less the same, except I'll use double MDF and might be using that new Dayton tweeter Jon has been testing out.

My question is; is there any particular reason why you had the front baffle flanked by the side and top panels, rather than the front baffle being the only visible piece from the front? I planned my cuts to have the side panels being behind the baffle, with only the front baffle and top/bottom panels being visible from the front. I can still change my cutting plans if this is a bad idea, I'm just wondering if there is some benefit to doing it your way in terms of construction of the cabinets.

-Thanks

[PMazz]

No real reason for doing it one way or the other. One benefit to the front baffle full is you won't have to worry about any mechanical fasteners in the driver cut-outs. I simply marked the baffle to prevent those problems.

It's a great design. I'm sure you'll be thrilled with them.

Pete