Measurements are the most difficult aspect of speaker design. To do the topic justice would be hours and hours long. Then the software that takes raw calibrated microphone response and allows a person to make meaningful engineering decisions is another set of tasks that need to be completed. If you're serious about acoustic measurements the best way to get up to speed quickly is to have a competent engineer measure some devices in your presence and explain why he/she is doing something in a certain manner and/or sequence. The parts-express forum has lots of engineers that visit, but because they are aware of the issues with measuring, they may not be of much assistance. I happened to have learned from Dr. Joe D'Appolito as he lives only a few miles from me. There is a shortcut but it costs thousands of dollars and still requires knowledge of acoustics and attendant engineering principles. That would be a Klippel analyzer. Another engineer (I am an EE) that I know once said it takes a decade to learn the engineering required to self-validate results. I think that horribly pessimistic, but there are learning curves. I learned enough in two years of study to make good measurements. If you simply want a speaker design tested there are a few acoustic labs that do this in the US, and I personally know one company that provides Klippel analysis at low cost, and professionally another that would almost certainly provide free analyses for non-commercial use. This is not intended to dissuade anyone from performing what are, essentially, formulaic tasks. I just want people to make good measurements is all.

Nonsense, Linkwtiz rules!

Can you recommend decent affordable measurement equipment, software etc? I have a blue blueberry studio condenser mic not sure if it works for this application

Correct

1. To measure accurately below 200Hz, outside of an anechoic chamber, requires being further away without reflections. That is not possible indoors. The low end roll off can be calculated and then confirmed with impedance and nearfield measurements. 2. A T shaped baffle does nothing to separate the front and back waves. It is nothing more than a brace. 3. Flush mounting is best.

@@dannyrichie9743 thank you!

For a first try, go to a thrift store an buy some cheap 2 or 3 way speakers. Take them apart and mount all drivers in a baffle. You will be amazed. I did the same and listen to rhem for months right now. Sounds so much better. Gonna make a second set soon. Philips drivers from the 1970's are great.

Actually they just made a diffuser for cancelling out the back wave. It's not at all new. And it is nothing compared to a tweeter that is completely open to the room.

For a minimalist ( like me)this design is ideal.... Just wondering how to order the wedgie parts?

@@dilbyjones The LGK drivers were sold out. I am trying to have more made though.

@@dannyrichie9743 It doesn't diffuse anything, it absorbs the backwave by an array of 30 Helmholtz resonators and matching impedances from the tweeter to the metamaterial via a conical horn. You should read the AES paper to understand the design. But it only works on the tweeter so only above the crossover point. The rest of the critical midrange is not absorbed. It is for monopole speakers of course. Open baffles have a whole different sound being dipoles and not every person or application is desires that kind of sound.

Stewart Markley - “Meta” is solving a problem unique to coaxial dome tweeters. Every good quality separate dome tweeter I’ve seen lately has a rear damped resonance chamber incorporated in the design.

Actually not all MTM designs have a narrow vertical window. We have quite a few with a really wide window and even vertical off axis that is better than most two driver designs. And the asymmetrical wings will also help maintain a smooth off axis response.

Yeah, an MTM done well sounds great

Hugo Bloemers I imagine these best with the large wings on the outside and toed in to something like 45 degrees. But I admit I’m unsure.

We typically put the long wings to the inside. This minimizes congestion in the front wall reflection and opens up the sound stage width.

@@vessk000 The wings don't cause or create forward or rear reflections. So no problems.

@@dannyrichie9743 Superb. Solves the problem I had with an 8 inch full range drive. Thank you.

That would alter the response and require a crossover change. Right now the crossover is handling what the baffle size is doing.

It absolutely does separate front and back waves, but it has nothing to do with toe in or toe out.

@@dannyrichie9743 In a planar open baffle (no side wings), front and back waves are separated in the virtual plane where these meet in equidistance due to their opposite phase. For a planar open baffle, this virtual plane is obviously the plane of the baffle. By setting the toe-in exactly as indicated by Linkwitz (using his mirror approach), the first reflection side waves that bounce off the side walls of the room can be minimised. By placing a rear wing, the virtual plane in which these front and back waves meet in equidistance no longer coincide with front baffle plane. So, to get the same minimisation of side wave reflections, the toe-in of the speakers must be altered accordingly with this change of virtual plane. That was the point I was trying to make.

They are mirror imaged, and the long wing goes to the inside.

Left and right off axis responses look great. And the sweet spot is really large.

Maybe Clayton and I will do something like that one of these days. And I wouldn't say that there is necessarily a right and a wrong. Objectives can be different and the highest performance or highest attained results based objectives might not have the value of a more marketable and commercially successful design.

It will make it more transparent and remove reflections within a certain range. It won't effect lower wavelengths too much.

Height is not a problem it's the size and width of the baffle that is a problem. Surface reflections and edge diffractions are significant problems with those.

So long as it is open to the top (not boxed in) and has some space behind it (not boxed in on the back) then it will be fine.

Wings would extend the low end cutoff and improve the output capability. But some EQ would be possibly needed to cut a resulting peak.

Apples and oranges comparisons. There are lots of advantages and disadvantages.

@@dannyrichie9743 I guess the short of what I'm asking is why you choose cone drivers instead. Apples and oranges are still dipole open baffle fruit, so I'm trying to understand the choices made.

That said, I've seen your line source vids with new record day, and that's all neo drivers for highs and mids, so it seems you do use those. I'm a new Magnepan user and audiophile newb. Thinking about building my own bookshelf planar magnetic speakers for fun.

@@aweidenhammer The line of woofers will move more air and play down a lot lower. It makes drums hits and such sound very real. The all planar magnetic drivers keep a narrow baffle width and offer high sensitivity. So imaging is much greater than a Maggie and the sweet spot is much larger. Plus you can drive them with low wattage amplifiers.

I don't try to model this stuff. I have done a LOT of this stuff and measured and tested it enough that I know what the results are going to be and where my starting points have to be. So it doesn't take me long to have a working prototype. It is the same for crossover design. I do it all the time. So I don't need to model something to know what will happen. I already know what will happen. I just have to put it together, test it, and fine tune it. Verses what we hear is a different discussion. I have to design based on accuracy. And that means on and off axis and what it is going to do in the room. The how it sounds is altered immensely by a whole different group of variables. But the fundamentals have to be correct to avoid errors and problems.

Danny Richie thanks for the response. Would love a video explaining more of that knowledge but understand if it part of the secret sauce you don’t want to share.

Coming....

Sure, and we do use them in the NX-Otica and NX-Treme models in an open baffle.