Another take on the Avalon Acoustics "Time"

[musiclear]

Here is a version of the "Avalon Acoustics Time" with my own tweaks added. I decided to go bigger and give it a bit of a Tee Pee shape. The final approximate measurements are about 52" tall, swept back 6°, 14.25" wide at the bottom and 10" wide at the top and about 22.5" deep. 1.25" side and back panels, 1.5" top and bottom and 3" a front panel.

I wanted to open up the space behind the woofers so I choose to use cut out panels for my fist two layers of the four front baffle layers. This three inch front baffle depth gave me the depth I needed to cut the side angles, and the cut outs in the first two layers lowered the weight of the baffle and I believe still maintains good panel stiffness.

Keep in mind that some of these measurements have changed by a fraction here and there, so please do not use this as a plan without checking all the measurements for yourself."

The Drivers are Wavecor WF182BD02 woofer, TW022WA05 Tweeter, a pair of Dayton RSS265HF-4 and two Dayton 12" PR's.

[JonMarsh]

This should be an interesting design and build! We look forward to hearing and seeing more about it. :T

[benthe8track]

Very cool. How are you thinking of cutting the facets?

[musiclear]

I've been thinking about this project for a while and read the Ardent posts and saw how others did it and thought....What the heck. I can do that. I'll just build a jig and throw it up on my table saw and slice away to perfection.

I got all the wood, that was a story, my jasper jig, which I will always have in my shop from now on, cut all the holes and glued the multi_layered panels together a little over sized so I could cut everything down to spec.

What I found was that my pitiful little Ridgid table saw was no where near stable enough to handle the weight and size of these panels and maintain a tolerance that would make seams as tight as I would want.

This took me to Jefferson Woodworking in Palm City where I live. They have an amazing saw with a huge table on roller bearings and up to a 20" blade with a master wood worker who agreed to help me out with the project.

Off went all the panels and baffles for tidying up and have the baffle facet cuts done.

What was supposed to happen was the 20" blade would glide through the 5" baffle cuts with ease.

As it turned out, the master wood carver drew some lines on the baffles and belt sanded them to spec. PERFECTLY. Amazing what 30 years of professional woodworking will do for you.

Here is a look at them held together with clamps.

[TEK]

Thats looking great.
It's MDF you'r using as bilding material, right?

How are you planning on doing the inner bracings?

[musiclear]

Thanks for the good looks comment. It is MDF. Yes braces to come. These are them. You can see placment with the dark lines on the drawings above. The drawings say 1/2" MDF, but I went with 3/4" MDF. I don't know what I was thinking.

[TEK]

BTW, I did almost the same with my sub, but used a power planer instead of a belt sander.
Worked out OK that too.
Seems as if there are a lit if ways if getting this facets done!

[musiclear]

I just took a look at your sub. Very nice! I noticed a couple of comments made about material and bracing. Your looking a multiple layers of Baltic birch ply rather than MDF for future projects and I think Jon mentioned in a fun way about bracing, "Too much is just enough".

I wonder about both comments for a couple reasons that I am sure you guys have discussed to infinitum and I know I risk flame, but here goes.

The question for me is "when is enough really enough"? In other words, at what point do panel resonance's become so minute they are inaudible in the room at listening position?


Another question is when do braces start to take away from the appetent volume of the cabinet as a result of low pressure points on the back side of braces. I am pretty sure that braces can if not fully thought out interfere with the back wave of the speaker and create low pressure points behind the braces which may result in the speaker response mimicking a smaller box. True? Not true?

[musiclear]

I modeled the dual woofers in True Audio's WinSpeakers and this is what the plot looks like.

[wkhanna]

What great project, musiclear!
Thanks so much for posting!

[TEK]

I just took a look at your sub. Very nice! I noticed a couple of comments made about material and bracing. Your looking a multiple layers of Baltic birch ply rather than MDF for future projects and I think Jon mentioned in a fun way about bracing, "Too much is just enough".

I wonder about both comments for a couple reasons that I am sure you guys have discussed to infinitum and I know I risk flame, but here goes.

The question for me is "when is enough really enough"? In other words, at what point do panel resonance's become so minute they are inaudible in the room at listening position?


Another question is when do braces start to take away from the appetent volume of the cabinet as a result of low pressure points on the back side of braces. I am pretty sure that braces can if not fully thought out interfere with the back wave of the speaker and create low pressure points behind the braces which may result in the speaker response mimicking a smaller box. True? Not true?

I'm no speaker or subwoofer designer, so I actually dont know. My approach is to build based on what others have designet and is recommending. I do thid by looking on the work done by professional, high valued speaker producers that get good reviews as well as other DIY folks. I then add what those are doing to my own beleaves, experience and capabilities.

However, imagine building the box out of 2mm ply. It would problably just be blown apart... So I'm pritty sure that is not enough. I guess there is some papers and reasearch done on this - maybe someone actally designing stuff here has some links? Could be interesting reading.

BTW: I see some norwegian builders that think that the combination of MDF or ply and aluminium plates laminated together gives a very dead cabinet. Personally I prefer harder wood types before metal, as metal is a bit of a pain to work with.

[wkhanna]

Aluminum.......

Link

[cjd]

I modeled the dual woofers in True Audio's WinSpeakers and this is what the plot looks like.

I'd personally drop the tuning frequency a few Hz. You're well into the range room gain starts to play, so you can squeak out a bit more while still having solid response as a result. It won't hit you quite as hard because it won't be elevated as much, but ... anyhow, not required.

Funny how this box shape gets around.

[musiclear]

I'd personally drop the tuning frequency a few Hz. You're well into the range room gain starts to play, so you can squeak out a bit more while still having solid response as a result. It won't hit you quite as hard because it won't be elevated as much, but ... anyhow, not required.

Funny how this box shape gets around.

It just so happens that the PR's I'm using tune the box to 23hz with no extra weight added. That makes it real easy to throw a little on and see how it sounds. I know if I drop the tuning a little then the delay is moved down also. I wonder how much of an inflance that will have. I think at those frequencies we are not really hearing notes as much as feeling shutter so I wonder how much of a differance it makes.

[musiclear]

I have given that midrange a bunch of thought and I came up with an idea that I hope will work out well.

I have had a love hate relationship with the idea of cabinets at all. They can give you pin point accuracy as the sound wave is well controlled when compared to an infinite baffle, yet inside the cabinet is a LOT of energy bouncing around and creating havoc.

Also, for some music I love the sound of infinite baffle, yet there is definitely a reduction in pin point realism with all the energy from the back of the speaker bouncing around the room.
To get around this, I decided to use a design that will be a compromise between the two. I decided to use a 6" thick wall PVC pipe glued to the front and back cabinet with a Scan Speak vent at the end and 4" of fiber glass board to soak up the back wave.

With this idea, there is virtually no energy bounce off the back wall, because it is open to the room, and there will be virtually no energy going into the room as it will be well damped with the fiber glass board.
I would have liked to have a little more room between the side of midrange tube and cabinet wall, but I figured the total square inches is about the same as the SD of the drivers, so I am hoping that will be enough to take advantage of the volume above the mid tube for total cabinet volume.

Here is the beginning of what that looks like. I guess I will see how it pans out.

[cjd]

You've seen the Statements (and Finalists)? As with those, you'll need to give this plenty of space between the back of the speaker and the wall. Crossover tuning will absolutely require accurate direct measurements and tuning.

I'm not sure how infinite baffle equates to "all the energy from the back of the speaker bouncing around the room." - it sounds like you're confusnig dipole and infinite baffle, which are two VERY different things.

Proper in-wall speakers (flush mounted) would be infinite baffle.

Any open back driver is dipole-ish.

If you've got the "sound bouncing" problem your room is the root cause, and box speakers aren't going to be notably better.

[musiclear]

I can't believe I did that.....You are correct. I used the wrong terminology for what I intended to say.

I did mean dipole. With dipole, the back wave of the speaker interacts with the room.

Thanks for that correction. Feeling like a bit of an idiot now, but thanks.

So to sum up, I was intending to suggest that I would rather side step the potential challenges of all the energy from inside a midrange cabinet causing problems and I would rather not allow a bunch of energy from the back wave to interact within the room, and thought an open back tube that was well damped would take care of the cabinet reflections and reduce the back wave coming out of the tube enough to not substantially interact with the front wave.

Thanks again for that clarification.

[musiclear]

Here is a pic of the fiber glass board in place. If you look down the tube on the right, you can see two cut outs. One for the Scan Speak vent, and the other for the tweeter and mid connection.



Here is a picture of the vent.



Here are the speaker connectors I decided to use.

For Mid and tweeter.



For the dual 10" woofers.



The enclosure mount.

[kevinm]

Just curious, why did you chose SpeakON connectors?

[musiclear]

Just curious, why did you chose Speakon connectors?

I've never used them, but heard good things about them. I like the idea that they are used in pro audio. That means to me a certain consistency and they tend to throw a bunch of power through them, they get banged around and don't get broken and they get constantly good ratings.

In addition, I have pretty thick wire and the push on and banana connectors are sometimes a little finicky if pushed.

Also, and most important, Phil Bamberg loves them. If he says do it.....I'm going to do it. He has been consistently right every time he told me what to do. I am not about to go against that track record. I do look forward to getting them set up in the system.

[kevinm]

Interesting. I've used them for DJ equipment (specifically, a DIY dual driver subwoofer build using 18in Peavy Low Riders) and they were great in that application because it made it much easier for non-audio experienced friends to setup the equipment.

I've just never thought about using them in HiFi. I guess I need more edumacation! :W

[Face]

I also prefer Speakon to traditional cheap binding posts and nanners/spades.

[TEK]

+1
I have in-wall cables for front, side and back speakears. All wall mounted plugs are speakon. Works great! Never a loose connection, in opposit to banan plugs or spades that have a tendency to loosen over time.
(for signal cabels I'm using XLR)

[musiclear]

Phil particularly likes the idea of SpeakerOn connectors for active systems because they are virtually fool proof and helps prevent hooking a tweeter up to a mid range channel. Once set up, you can plug or unplug the speakers at will without potentially frying a tweeter.

[musiclear]

Here are a couple pics of the connectors of the back of the speakers. Each connector caries up to two channels. The tweeter wire is mounted in the cabinet already and will have to be soldered to the open spade connectors when I mount them into the cabinet. I used the second channel on the bass wire to carry an additional set of wires giving it the ability to carry the signal more efficiently. I also have a dual run of the same 14g wire running from the back of the amp to the speaker. Need it....probably not. Will I hear a difference.....probably not. Does it feel good to know that it really will do the job no matter what? Yup.

[musiclear]

Gluing the front baffle.

[Juhazi]

Hi I have been thinking of something like that, but with the mid up and 10" woofers in closed box. Nice to see your box technique!

I have the mids in my shelf and I have a source for second hand tweeters and woofers. A friend might design a passive xo, based on my measurement in the box (with horizontal polars 0-180¤) So far I have measured only the mid in a proto baffle

[musiclear]

Seems like a cool design. What is your reasoning about the mid on top?

[musiclear]

One more step under way. I've changed my mind about the sides and am waiting for more veneer to show up, but I got the fronts glued on.

[JonMarsh]

Curly maple... Nice! One of my favorites! :T

[Juhazi]

Seems like a cool design. What is your reasoning about the mid on top?

(by the way my wish for veneer is curly birch or curly maple, stained to walnut brown)

Several reasons:
- diffraction analysis with Edge
- LR2 topology beam tilt favourable without time alignment im M/T arrangement "old school"
- easier to make mid enclosure
- c-c from mid to woofer will not be a problem if I cross around 500Hz

My version uses 100mm mid which has Fs 252Hz and 8" woofers (but there is room for 10"s) I just happen to have those mids and I think this will be a good way to use them!

The Edge is a neat little diffraction simulator that I like (I have none of do-it-all simulation software) and I just made simulations of M/T and T/M setups. With mid up it's diffractions are above the passband and for tweeter down it's diffractions are minimal!

Attachments of mid up and tweeter up/down and measurement of the mid in a test baffle! I have simmed the woofers too, there should be no problem with vertical lobes either!

This will be a slow project, but I hope to get the tweeters soon so I can run more tests in my proto baffle. I have a minidsp 4x10HD available for protoing, but a friend will try to do passive xo.

[musiclear]

Sweet design. BTW, I am having an abundance of really nice Curly Maple left over I will be offering up for sale. If anyone's interested, they could score this for a reasonable cost.

[Juhazi]

Musiclear, don't worry!

I set up my Fountek NeoCD3 on the test baffle and took sweeps with tweeter up and down at 1m and nearfield at 20cm (8") These show very clearly that tweeter-up gives much smoother response! Nor will the mid suffer from being placed lower.

I have learned to trust Edge simulations, but this time they failed. My test baffle is not the prettiest but it was a quickie:B

[musiclear]

The project has moved forward and here are some pics. I still get to finish the veneer on the sides and apply some finish. My friend Dave and I built the cabinet between the speakers a few years back for another place. I might have to upgrade and build a bigger new one with Curly Maple to match the space and speakers.

[musiclear]

I've had an opportunity to work on the crossover and it is getting pretty well dialed in. Phil Bamberg designed the topography for the crossover between the tweeter and mid. That guy is amazing by the way. You can check out his web site here if your interested. http://bambergaudio.com

It was my job to get the crossover between the mid and sub right. The whole system is working very well. It's all active all channels. These measurements are with the tweeter off as I was dialing in the low end. I'll post complete measurements as I get them.

[wkhanna]

Absolutely Gorgeous!