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Old 27th May 2007, 11:16 PM   #1
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Talking Calling John *Zaph*... 5.25" midwoofer designed/built from scratch

Well hopefully John sees this because I would like to send him one for his feedback when they finally appear at my door step...

I could use some feedback here as well.
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This FR is just the same cone/surround on a different lower Le, less open motor (no pole venting) in order to get a feel for the FR:
Click the image to open in full size.

It has a stamped frame that allows slightly closer c2c spacing however that makes a home-made jig necessary for routing work instead of the handy jasper jig.

I'm looking at ~60-80W RMS in theory (which still needs bench tested) and 5.5mm of xmax.

The sensitivity and BL are a bit on the low side, however it should do nicely IB or in car. They still do quite well in small sealed if a slight 1-2 dB peak is acceptable and they do rather impressively in a number of ported alignments especially with a bit of EQ. I think I will be working with .3 cuft sealed or .4 cuft @ 50hz with 2dB of cut at 100hz, Q of 1. The extra power handling with the high temp coil makes up for this lack of sensitivity.

I'm working on finding an appropriate cast frame with venting under the spider landing for a future higher end high value unit with nice thick short paths, a phase plug and hopefully a spectra fiber (or any HSHMPE High Strength High Modulus Polyethylene Fiber) cone if I can find a manufacturer that is capable of producing them. If I can't make a cone out of pure fiber in a reasonable time frame at a fair price I will work on a wood pulp mix with this fiber in it. All units are made with 1006 steel as my standard unless a super alloy or pure (99.95%+Iron) is used.

I guess you could call this project extreme DIY. I would like to work some more with other people on future projects but between finals and the current projects I have on my plate I am completely swamped. I'm pressed for time and money to keep doing such insane projects
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Old 28th May 2007, 08:10 AM   #2
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Yes, I'd say that qualifies as extreme DIY. Congratulations -- it looks great!

More info please -- why did you undertake this project? What experience or background do you have? How did you choose the diaphragm material, design the dust cover, etc...? Who built the driver for you? How much did it cost? You mentioned the reduced c2c spacing -- do you envision this driver in a line array or MTM?

I have been waiting for a manufacturer to introduce a 5.5" - 6" driver optimized for open baffle use. I was even considering sending my ideas to the established manufacturers to see if they would be interested. So I would love to know how you got this driver manufactured to your specs.
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Old 28th May 2007, 01:05 PM   #3
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So... you made that driver?

The Four Chairs
DIY Home Theater
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Old 28th May 2007, 11:20 PM   #4
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Originally posted by Javachip

More info please -- why did you undertake this project? What experience or background do you have? How did you choose the diaphragm material, design the dust cover, etc...? Who built the driver for you? How much did it cost? You mentioned the reduced c2c spacing -- do you envision this driver in a line array or MTM?

I have been waiting for a manufacturer to introduce a 5.5" - 6" driver optimized for open baffle use. I was even considering sending my ideas to the established manufacturers to see if they would be interested. So I would love to know how you got this driver manufactured to your specs.

This project is only a small part of the work I've been doing for the past 2-3 years. The point of this particular 5.25" was to have a simple project that could judge the accuracy of the simulations I have been doing and to gauge the quality of the Chinese ceramic magnets and/or the quality of their magnetizing setup. For example, the BL for this unit was about 20-25% lower than calculated (which as you see turned out pretty nicely anyways). In the future, I will be getting some samples made with the following changes:
A. A larger magnet
B. The same magnet but pre-magnetized at the magnet factory.

This will help to determine how accurate the simulations are, as well as make sure that the assembled motors are able to be fully magnetized, which I have a feeling is the weak link in terms of Quality Control.

I have a deep interest in speaker design and I have some ideas on how to push forward the industry in new ways. I also have a reliable friend in China that is connected to the industry over there and can help me overcome the language barrier which is the key to getting anything done. I do have to spend some long hours working on this series of projects way into the early hours of the morning quite frequently, but the reward of seeing your project come to life is more than enough payoff.

FEMM is a powerful free tool to help design motors and I would love to involve the community in the design process. After I'm out of college for the summer, I'll have some more time to dedicate to my projects and try to put together some tutorials for using FEMM to design motors. I have to work on a few patents which will keep me a bit busy, but that's another topic.

I would like to involve the community in the design stages for upcoming projects, since the community will be better served getting drivers that more suit our needs. It should also help keep prices at an absolute minimum, since this is a group DIY project. I started out trying to commission a 6.5" OEM driver with a partner, but that didn't go very smoothly, so I'm working on it all myself. You need truly interested and motivated people working on a project; hopefully there are a few here. If you need any more motivation, I've learned more by jumping into this project head first than I have learned in my 3 years of college so far...

I don't even want to think about how much I've invested in the more esoteric projects that still have a few hiccups to conquer. As for this 5.25", I have about $2800 currently invested in direct costs for 500 units I've designed and I'm estimating about $3500-4300 before it's actually in my hands since this is a LCL cargo load.

As for my background, I first got into DIY audio as a freshman in high school and learned by browsing the forums and reading white papers as well as tinkering.
I went through the FEH (Fundamentals of Engineering for Honors) program at The Ohio State University which helped a bit and have since been learning about the business climate at the OSU Fisher College of Business and when it comes to engineering I am picking up what I can on my own as it is needed.

As for who is making it, even with my buddy in China helping me out, it has taken me over a year to find decent parts suppliers, and still there is room for improvement, so I'll hold onto that bit of info.

Since I don't have any powerful FEA tools that allow me to model the cone breakup modes, I basically have to use common sense, look for high elastic modulus cone materials with lower densities, look at the speed of sound through the material, as well as look at the specific rigidity since as a panel gets thicker, it gets more rigid. Young'sModulus/Density^2 for a factor is a good rule of thumb, but it's a bit more complicated than that since you also have to factor in geometrical stiffness of the cone profile and skin/core interactions in composites. Basically, my line of thought about this cone was to mix in some textiles into a paper pulp and make a very sturdy paper similar to paper money. I was expecting it to have a little better self damping with the textiles but we will see how the linear distortion data looks asap.

There is a relevant white paper that shows some general trends in how the breakup modes behave for different cone profiles that I would have to dig up again...

Basically the short story on how to do this for yourself is to make some good friends in China to help you out, learn to design the motor, make drawings, browse various prior toolings to see if there is anything you can use, tool anything you need to, go over everything about 10x with a fine tooth comb, keep on top of what they are doing in China, and don't forget to sample even the most minor change, because it won't be right the first, second, and likely not even the 3rd time.

I have two different projects in mind for this unit: one consists of a MTMWW with the seas27tbfc/g ;and the peerless XLS 8" discontinued unit with the 8" units acting as powered subwoofers.

I'll make a small ultra budget MTM for my apartment with one of the Dayton neo tweeters.

The other project I have in mind is a MTMMMMM... (or some variant on the theme if someone has input) floor standing unit if I can manage to get that to behave

I would love to make a line array and that was in mind when this was designed but I'm not quite up to that task at the moment.

I also have some 8" speakers laying around that I picked up on ebay awhile ago that were worded as B stock Genesis 501 drivers that might be fun to use that have a fairly high Q as well.

This business model is very closely related to open source movement, the important difference being that the key innovations are to be protected by patents held by the individual. This is to reward the efforts of my future employees or individual contributors to the project to give an incentive and encourage an overall fast pace of innovation in the industry.
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Old 29th May 2007, 02:15 AM   #5
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Matt is that you or is it Dylan?

Nice work BTW, must have been a huge commitment to get those drivers made and shipped. I wish I could be an active part in what your proposing but I suspect I couldn't give it the attention it really deserves.

I'll keep a very close eye on this thread.
The more you know who you are and what you want, the less things will ever be the same.
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Old 29th May 2007, 04:05 AM   #6
Daveis is offline Daveis  United States
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Can you post distortion plots?
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Old 29th May 2007, 05:36 AM   #7
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This is Dylan, Matt is busy and not devoting his all to the project sadly...

There are no short paths in this version since that would have just complicated things even further. I could have placed a copper cap on the pole but that would have necessitated me making the pole less extended to help facilitate assembly. Also Im not a huge fan of caps when used all by themselves. This would benefit the most from a pole sleeve and/or a short path inside the ID of the top plate and/or inside the magnet. A short path disc between the magnet and top plate would also be nice if we had some magnetic energy to spare You can plate or clad copper a part for thin shorts at a fairly high price per unit, or you can get an extrusion mould made for a high startup and a low cost per unit. I tend to opt for the later option but again the point of this unit is to release a fairly nice budget unit that can hold its own IB and hopefully has markedly low distortion in the midbass.
When a higher end 5.25 with shorts is made it will likely be using a different motor topology or just a bit of an increase on the pole diameter to 1.5 possibly 2 or so.

I want to get a hold of John *Zaph* for the distortion measurements as well as a more accurate FR, if he is interested. The DAAS system in question is older and cant run the harmonic distortion sweep like the newer ones can.

Oh and any help on any projects are appreciated, they do indeed sap all of my spare time and energy. I'm sure my girlfriend wants to beat me/my computer sometimes

You can take on a pet project and work on it on and off for 2 years getting feedback I'm sure something good will come of it... The worst that could happen is that it inspires someone or a few new ideas. Or help work on the wiki segment of the webpage which is where Id like to stick the information embedded in the threads.
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Old 29th May 2007, 02:27 PM   #8
PB2 is offline PB2  United States
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Nice work!

Designing a new driver like that brings to mind the KEF B-110 and the LS3-5a. It would be nice to have a new replacement driver, and/or one for clones. I realize that this is not your intent.

A clone of the 6.5" Audax driver in the Spica TC-50 would also be a good one.

The Dynaudio 8" 21W54 was an interesting driver in that it had very large mechanical Xmax, about 14 mm as I recall and a 3mm linear Xmax.

The Ascendant Audio poly 6.5 is another that I'd like to see a second source for.

Just throwing these ideas out as food for thought.

Pete B.
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Old 29th May 2007, 03:10 PM   #9
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Jesse James said that all the knowledge in the world doen't mean crap if you don't get off your *** and do something with it.

Good job. What you have done so far is impressive even if it sounds like crap ... I'm sure it doesn't, I'm just saying is all ...
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Old 29th May 2007, 04:05 PM   #10
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Well I have an assembled unit in front of me with a standard sorry excuse for a motor slapped on it. I was just interested in the cone quality with this sample and the midrange quality is quite impressive if I must say so myself

I would guess that it would do best crossed over under 2-2.2khz but Im sure it can do higher than that without much in the way of compromising. I have a feeling that there could be some DIY tweaks to make this behave a little better at 2.5khz since there appears to be a bit of a larger peak there. This frame is just ever so slightly larger than the Seas MP14/RcY cast frame that I was hoping it would be a drop in replacement for .

My .02 on sound:
The midrange is more transparent than normal, and I'm hoping that my motor will have below normal distortion since that was one of my main goals. The extended pole and increased xmax should do something right? I sure hope people like it so I don't have a pile of 500 midranges cluttering up my garage.

A line array does sound nice if I can manage the time...
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