MTM Build using Tang Band W8-2145 and Aurum Cantus G3 need advice

w2olves

Member
2016-02-23 8:45 pm
I apologize if this is a repost, I am unsure what happened to my original post.

Anyway, I am a long time lurker and first time poster here. Looking for suggestions/advice on a speaker build.

Long story short, my center speaker died a nasty death last night in the hands of our family dog. Instead of buying a new speaker, I am planning to build one using drivers I have on hand.

I have two Tang Band W8-2145 drivers and one Aurum Cantus G3 tweeter.

I am planning to build an MTM with those. I am thinking of running the tang bands full range in parallel and the tweeter in a high pass (1st Order) at 10Khz.

I don't have issues with WAF, she actually likes larger speakers but I do have space constraints and my maximum available space is 28 inches wide, 12 inches tall and 16 inches deep.

I will be about 19 feet away from the center speakers.

Also, I am interested in keeping the aurum cantus tweeters as my main speakers are also Aurum Cantus and I believe this will blend well.

Now my question(s)

1) Is this even a viable idea or am I better off using a different driver ?
2) Should I add a bandpass filter for the Tang Bands ?
3) Any recommendations on cabinet volume, crossover design etc ?
4) Any other recommendation, observations ?

I realize adding two drivers of this diameter will take away the point source nature of the full range drivers.

Thanks in advance
 
Just off the top of my head you'll get combing issue crossing the two tangbands that high up with their centers that far apart.

Options:

You might be better off buying dedicated midwoofers.

Use one tangband with the tweeter.

Make your mtm but use one of the tangbands for baffle step correction, kind of a 2.5 way speaker. More complicated.

Jut some ideas :) Good luck!
 
Tang Band W8-2145 + Aurum G3 ribbon for a center channel.

STRIKE-1
There are well written MTM papers discussing and illustrating why using a midrange larger than 4"-5" will produce a confused sound stage, plus large variations in SPL with listener location. Lobing. Comb Filtering. Nasty Sound. NASTY, NASTY with horizontal MTM using 2300Hz crossover.

Biro Technology
Vertically Symmetric Two-Way Loudspeaker Arrays Reconsidered

STRIKE-2
The Aurum G3 ribbon tweeter datasheet recommended a crossover frequency of 2300Hz, which is much too high to blend with the 8" TangBand W8-2145. The W8 would beam(narrow polar pattern) at 2300Hz, then the G3 would jump in with a wide polar pattern to mess up the soundstage.

STRIKE-3
"my maximum available space is 28 inches wide, 12 inches tall and 16 inches deep"
TM stacking 6.6" tall G3 ribbon on top of 8" W8-2145 > 12" tall. TM with the G3 ribbon located on the side of one W8 with a 2300Hz crossover will have "marginal quality" sound which could detract from the main soundstage.
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You could use just the Tang Band W8-2145 full range (ported box) for a center channel. OR within 12" height you can purchase a physically small dome tweeter which can be mounted above the W8 with a 1600Hz crossover for smooth polar directivity control. Maybe carefully cut off the whizzer cone on one W8 in order to use it more like a true midrange.
 
What you should do is to lay the MTM horizontal with the ribbon arrayed vertical between the two mids. Space the drivers as close as you can get them. Thus you have greatly reduced the spacing between the two mids while reducing the spacing between the mids and tweeter. Cross over at 2300 Hz or lower if you can with likely a 4th order acoustical crossover.

Ribbons and MTMs are not amenable to first order crossovers. Ribbons need to be protected from the lower frequency signals while reduced spacing will help with off axis response dips because of interaction between the two mids.

While using the 8 inch mids isn't great for this application, try it and you may be surprised.
 
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w2olves

Member
2016-02-23 8:45 pm
Yup not a good idea

I am beginning to get the picture. This is probably not a great idea. With not even one enthusiastic thumbs up, I am weary to even experiment with this.

Thank you guys for saving me some headache later on down the line. Maybe this discussion can also help other hobbyists with similar plans.

Now if you were in my shoes and had aurum cantus mains that you were happy with, would you consider keeping the tweeter and buying a different mid or would you build a center using a single w8 driver ?

A side note, a few months ago I heard a line array speaker using Fountek drivers for the first time. It had a sense of music that I have not heard before. I can't even explain it. Anyway are line arrays a possible good choice for a center speaker ? Sorry about the noob question.
 
At 90db/W, the 5" Tang Band W5-2143 is a $52 full range worth your review for a 2,300Hz crossover frequency to a ribbon tweeter. W5-2143 has an underhung motor, very low Le, and a phase plug for some high frequency smoothing help. Mms =6g using Bamboo fiber and paper cone with santoprene surround. Good reviews.

Part of the G3 face plate can overlap the W5 frame to meet the 12" height restriction.

F3= 57Hz in a 0.5cuft ported box. One 2" diameter port, 3.8" long

There are 5" (and "maybe" 6") light-cone speakers which might fit your 12" box limit, which get good reviews with ribbon tweeters.
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Probably 3 reasonable options:
1) Use just a single W8-2145
2) Use a single W8-2145, AND add the Aurum G3 to the left and accept funky sound stage.
3) Put a 5" (maybe 6") light-cone midrange on the bottom which can integrate with the G3 at 2300Hz stacked above it, and still fit into the 12" height limit.
 

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w2olves

Member
2016-02-23 8:45 pm
Another question

I think I will indeed go with #3. Thanks everyone for chiming in. I am curious about one thing.

Why did everyone suggest crossing over low ~ 2300 ? I thought with a full range driver, everyone will suggest using the tweeter more as a "super tweeter". I am curious if anyone wants to elaborate.
 
The standard rule of thumb is to cross over at a frequency so that the center to center spacing of the two drivers is less than a wavelength or less distance. Some designers prefer even closer.

As reported in the Biro Tech paper on MTMs (referenced above) closely spaced mids are needed for those two drivers or else the frequency response suffers off axis dips which would be heard.

The configuration that I suggested earlier (horizontal mids with the ribbon placed vertically between them will address these issues. Bottom line is reduce the driver spacings and lower the crossover frequency is necessary with MTMs.
 
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w2olves

Member
2016-02-23 8:45 pm
I am thinking of laying the center on the side, making two circular cuts on the faceplate of the tweeter, so the two 5 inch mids can sit very close to the tweeter.

I did read the article referenced multiple times, I think each time I understood something new and still have quite a bit left to fully comprehend.
 

mayhem13

Member
2008-09-22 4:37 am
Lots of good advice here.

I reckon option 3 might be the best bet if you're happy with your Aurums?

3) Put a 5" (maybe 6") light-cone midrange on the bottom which can integrate with the G3 at 2300Hz stacked above it, and still fit into the 12" height limit.

If don't agree.......you'll be sacrificing all that great efficiency with a single 5-6" midrange.

Two 5" mids in an MTM with your ribbon would be my approach supported by two 8" woofers below or one top and bottom. MTMs are fantastic when done properly and ribbons just sound so open and revealing when used within their passband properly. I'd cross higher to 3khz with 5" mids and I'd use a truncated frame mid to reduce center to center spacing........the Aurum Cantus AC130 immediately comes to mind as an excellent candidate with no breakup modes and simple crossover.
 

w2olves

Member
2016-02-23 8:45 pm
Laying down the center sideways, the maximum width I have to work with is 28 inches. That wont allow me to put the tweeter, two mids and two woofers. It definitely would look grand. I am torn by different comments on how it would sound. I would probably also need a lot of help in getting the right crossover designed.

But you do have an interesting proposition.
 
Hi w2olves,

That's part of the problem with this excellent hobby, there are often lots of options available to you. All we can do here is suggest things and try keep you from making a fundamental error.

Analysis paralysis is a real thing, I broke out of it this year by actually starting to make some things!
If you have the time and you stop worrying about getting it perfect first time why don't you try a prototype build with some foam core?

xrk is the man in this regard, here is an index of projects.

http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html

My very first step would be to try the tangband run full range by itself.
 
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A 2-minute Xdir horizontal_MTM sim of the W8+G3+W8 crudely illustrates the horizontal comb filtering which can change the soundstage and SPL for listeners over modestly spaced seated positions.
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Baffle Step....If you construct a 12" high [G3 .above. 5"midbass stack] + adjacent port| vertical TM box center channel for under your Flat Panel, your simulations should factor in baffle step effects. If this speaker is placed close to the rear wall, you will gain a few db of low bass extension. If the center channel box is several feet away from the walls, you might consider increasing the horizontal box width to provide cabinet bass extension support.
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If you plan to construct a G3+W8 horizontal TM to enjoy the Aurum G3 plus the efficiency of the in-hand(free) W8, and you accept some sound stage faults from the 2,300Hz crossover, you might consider carefully cutting off the W8 whizzer cone...leaving ~0.1" near the bottom for strength.
---a clever single experimental cabinet supporting alternative screw-in baffles would allow you to test: just W8; G3+W8; W8+small dome; G3+5" midbass.
 

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w2olves

Member
2016-02-23 8:45 pm
Thanks for putting so much time and thought into this. I really appreciate it. I am going to settle for a pair of W5 with the Tweeter but since I have a couple of spare ply sheets, I am thinking of cutting up a couple of experimental baffles. Is it possible to mitigate some of the comb filtering issues if I angle the two W8's inwards around 20 degrees ?
For a small dome, how would the Tymphany NE19VTC-04 3/4" Deep Anodized Aluminum Dome Tweeter work ?
 
FWIW, way back when, we use to 'liberate' old TV, mobile audio oval drivers as an economical way to control directivity to some extent and you could squeeze a stacked pair of modern 6x9" on your 12" baffle, then suspend the G3 in one of them to create your own co-ax. Since these drivers are high Q, they should have plenty of mid-bass 'punch' and a stuffed open back box should be sufficient.

GM
 
Not really, I haven't messed with mobile audio since '90, though at that time the Infinity Kappa co-ax series was by far the best bang/buck to the point where I used them a few times for others HIFI/HT speakers and installed them in an '87 RX7 convertible and '90 SS454 PU where they got lots of compliments and ~15 years of enjoyment before they were stolen.

Nowadays I rarely listen to anything other than news, talk radio in a Toyota PU, which came with a pretty decent system as is for what few old rock, country, jazz CDs I occasionally listen to.

GM