# Build Log - New 3-way Home Build w/ Processing -



## katodevin (Feb 14, 2008)

This is a build log for a 3-way home system that I am tackling over the next couple of weeks.

First and foremost, 90% of my knowledge I have gained from car audio related research (a lot from this site), so I may be taking a bit of an unorthodox approach at tackling this home audio project. I think that my approach may be a strange hybrid between car audio and home audio, so please feel free to tell me if my ideas are stupid or insane. 

I have built a few home audio projects with good success, following plans by Zaph and others. I decided to make a design of my own to try and hit upon some characteristics that I am looking for, which may not be as commonplace with other designs.

I set out to design a system that has
- good off axis performance - while I'd love to be sitting smack dab in front of my home system all the time, often times I'm unable to and would like to have a bit larger sweet spot
- capabilities offering room correction - for the times when I am able to sit right in front of the system, I'd like to have as best response as possible. I've enjoyed the benefits of flexible per channel EQ and time delay in car audio, and would like to implement that into this system as well.
- is not monstrous - only 1 thing to say about this goal - it is a girlfriend enforced one...

I have had good success with 2-way systems in my past home projects, but wanted to go to a 3-way in an attempt to allow the speakers to play more in the range before they begin to start beaming, therefore improving off axis response. I'm not looking for better on-axis performance, 2-ways in the home do that fine.

to be continued with my driver selection...


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## katodevin (Feb 14, 2008)

Starting at the bottom end, choosing the Exodus Audio Anarchy mids was a no brainer. I've enjoyed these in my car for a few months now, and while I liked my Seas Reeds in the midrange in a 2 way setup, the Anarchy can't be beat down low. I am planning on running these between ~70hz-350hz, so midrange performance isn't as important. I like these because they put out really clean articulate bass, with a very very good price/performance value. They also don't need that huge of an enclosure - the manufacturer recommended a .5cuft box (before driver displacement) with a 8 inch long 2.5 wide port.










For the midrange, I chose the 2.5" mid from Vifa's new NE line. I got a pair a few months ago, and have been fooling around with them as testers. I've used them fullrange and as mids, and they've completely impressed me with a very clean and transparent sound. They play the midrange extremely well, and go pretty high as well. Comparison of these to the Tang Band bamboos @ 3" is no contest, as these sound cleaner and have better bass performance. I decided that a 2.5" mid would have a bit better off axis performance than a 3" mid. I plan on using these from ~350hz-3500hz. 










The tweeter was a bit of a more difficult choice. I know from math, and from experience, that smaller dome tweeters have a bit better dispersion than larger domed tweeters. I did some research for a 3/4th inch tweeter, and didn't have that much luck finding something that was priced well. I then started looking into horn tweeters and waveguides and found some info about DXT technology. DXT Homepage Basically it uses a geometrically designed flange to create early reflections at different frequencies. It uses these to widen the sound field. Sounded a bit gimmicky, but then I noticed that Seas had licensed their technology in one of their tweeters. Decided to give it a shot, as a widened field is exactly what I was looking for. Picked up a pair from Madisound and am eager to try them out.


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## 2500hd (Aug 22, 2009)

What do you plan to use for crossovers?


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## katodevin (Feb 14, 2008)

Here's my crossover plan. more details to come.


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## Austin (Mar 12, 2009)

Subscribed.


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## sinister-kustoms (Jul 22, 2009)

Interesting approch to the crossover idea...me likey! +1 subcribed!


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## katodevin (Feb 14, 2008)

So as I alluded to earlier, I will be using a pair of MiniDSP's for crossover duty. The MiniDSP's (for those of you who don't know) are small boards, as pictured above, that have the capability of loading a variety of different plugins into the memory of the board. From that point, these boards are able to process a maximum of two inputs, and four outputs. Possibilities are stereo EQ'ing. 2-way stereo setups, 4-way mono setups, etc. These are produced by a company located in Asia that operates very un-asian-like. I got my boards shipped to me the same day as my order, and I received them 3 days after. Customer service inquires are answered quickly, and in grammatically correct English. I have the confidence that these boards will be the brains of my home stereo and save me a TON of time.

These will be configured with the advanced 4-way crossover plugin. This plugin allows for a single input to be routed through a 4-way crossover. I got two MiniDSP's, one for left channel, and one for right channel. Additionally, it allows for a parametric EQ to be applied to the signal BEFORE division (channeling), and a parametric EQ to be applied to EACH output channel. That is a total of 5 parametric EQ schemes that can be applied to the signal. The MiniDSP then outputs 4 channels to whatever amps you want.

I am going to be running it in 4-way mode. I will have channels dedicated to tweeters, midrange, midbass, and subwoofer. I will be using a single subwoofer, so I will be mixing the subwoofer outputs from each MiniDSP into a mono signal for my subwoofer amplifier.

As far as the MiniDSP, I have been fooling around with it for several nights. Basically it can be powered by ANY power source between 5 volts and 24 (I think). It can be powered AND interface via a USB cable with a PC. One of the awesome benefits of this is that I am able to hook the MiniDSP up to my computer, plug it into an amp, and immediately tweak crossover settings and EQ settings - seeing and hearing the results in real time. 

For example here's a scenario/workflow... I set my tweeter to handle 4k - 20k. I am able to define a slope of my choice for each crossover point. I define a 24db Linkwitz Riley slope for the bottom, and a 48db Butterworth slope for the top (Bessel is an option too). These are implemented in real time! I then take an acoustic measurement using a microphone of the tweeter playing pink noise. I see a spike at 8k. I hop into the tweeter channel specific parametric EQ, and define a narrow dip at 8k of a specific Q, and a specific DB drop. I then remeasure and see a flat response. Tweeter setting is done  Move onto midrange... It is that easy! I can define up to 6 parametric curves per channel, including peak/lowshelf/highshelf. This is an incredible amount of tuning per driver. 

Crossover network definition (tweeter specific)









Parametric EQ (tweeter specific)









The features of this are absolutely awesome. When combined with a calibrated mic, and patience, I have no doubt that I will be able to achieve very very good tuning. I realize that passive crossover design is an absolute art that is left to the gifted and inspired. I do not think I have this talent, but I do have the ability and patience to measure, adjust, measure, adjust, and repeat. After adjusting the speakers for flat response in near field, I want to take a room measurement from my seating position, and apply an inverse curve to achieve as flat of a response as possible. 

Another feature that I plan on taking advantage of is that each channel is capable of time delay. After final installation and nearfield tuning, I want to pulse each set of drivers (tweet/mid, etc), with a short signal, and measure the time delay in arrival of the pulse at my main seating location. From that point, I plan on adjusting the time delay until pulses from all drivers arrive at my seating position in the same time.

Let me know if you have any other questions on my planned application of the MiniDSP. I am pretty familiar with it at this point, and can answer questions regarding its setup.

Next - Baffle construction!


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## Cruzer (Jul 16, 2010)

looks sweet.

after i finish my truck, ill probably be looking into doing something like this.


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## katodevin (Feb 14, 2008)

So here is my baffle design.










I contracted some guy recommended in the fabrication forums to cut these for me. Unfortunately his work sucked.

I sent him the below communication and have yet to hear back from him.

"Thanks for checking in. Unfortunately they didn't come out as I planned. 

- Overall dimensions are off by 1/8th of an inch
- Machining marks on inside of cutouts
- Cutouts show bit plunge marks as "dents" in the contour of the circles
- Roundover is uneven, and not 1/2 inch 

I realize that your pricing is very low, and I guess the adage of "Cheap, fast, good quality - choose two" came true. I'm a bit disappointed, and will find some shop time to knock these out myself.

Once again, thank you for your customer service and prompt communications, I'm sure that most of your other products - I.e. sub rings are up to par. I think that this project may have been a bit more difficult and required more attention."

So I guess if you want something done right, you simply have to do it yourself. I'm in the middle of moving, so it'll be another week before I'm able to start making sawdust again. My router and Jasper jig are tucked away in a box.


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## wdemetrius1 (Aug 16, 2007)

Updates?


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## katodevin (Feb 14, 2008)

Finally moving on this project after getting some baffles from the great Mr. Marv.

Exodus Audio told me that they like to see the Anarchys in a .5 cu box with a ~ 8 inch port. I took their advice and I'm running that now, but first listening impressions is that it is a bit boomy. Modeled the mid up, and its asking for quite a bit less volume. I'll have to bust the RTA out and see if I can get that tamed.

Anyone have any suggestions on ways to tune this? Simply keep adding some mass inside of the enclosure and check it on the RTA until I get a flat response? 

Also, am I right in tweaking the physical design of the enclosure before I start with the processing? Or should I try processing before making design changes?

I'm tempted to give up on the port and seal it up.


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## Fast1one (Apr 6, 2007)

I think you should have chosen a larger mid to go with the waveguide loaded tweeter and gone with a lower crossover point for the benefits of directivity control. In fact, running the anarchy along with the DXT tweeter would have allowed for a smoother power response transition at the crossover point, likely somewhere around 2khz. 

As it sits now, you are going to have a poor power response whether you cross over low or high. Crossing over low will help with the ctc spacing between the vifa and the tweeter, but the polar response will be rather atrocious since the vifa would still be omni-directional at that point while the DXT will start to taper off. 

Crossing over high, where the the vifa begins to beam will net a very small window ( on axis) due to the large ctc distance. Small deviations in the vertical axis will contribute to large variations in off axis response. Head in a vice comes to mind.

You can by all means continue and net a decent sounding speaker (as long as you stay completely motionless). But to do it right I would recommend one of two options:

1. Ditch the DXT and go with a small 3/4" tweeter crossed over around 3-4khz. Aura NT1 comes to mind. 

2. Ditch the vifa and go 2-way with the Anarchy, start with an acoustic crossover around 2khz. Due to the loss in response you may want to start with a first order electrical on the DXT around 5khz or higher and a 2nd or 3rd order electrical on the Anarchy around 2khz. This link is a very good reference for that application: The Seas ER18DXT ported two way


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## katodevin (Feb 14, 2008)

Firstly, you have a million thanks for responding with your advice. I really appreciate the learning opportunity. I did have a few questions/points for you to elaborate on if you havetime time.



Fast1one said:


> I think you should have chosen a larger mid to go with the waveguide loaded tweeter and gone with a lower crossover point for the benefits of directivity control. In fact, running the anarchy along with the DXT tweeter would have allowed for a smoother power response transition at the crossover point, likely somewhere around 2khz.


I agree, looking back, I would have gone with a bit larger mid, maybe one of the H-Audio guys. I was very impressed with the Viva's though, even when running them full range on my test bench. Also, I'm not married to a specific crossover point, so I plan on experimenting.



Fast1one said:


> As it sits now, you are going to have a poor power response whether you cross over low or high.


Is the poor power response you are referring to going to be caused by the smaller mid? In my testing, the mid got more than loud enough for my application/liking and stayed very smooth throughout my test band of 400hz - 4000hz. I do not have a full grasp of what contributes to poor power response in this case, so if you could shed a bit of light, I'd really appreciate it.



Fast1one said:


> But to do it right I would recommend one of two options:
> 
> 1. Ditch the DXT and go with a small 3/4" tweeter crossed over around 3-4khz. Aura NT1 comes to mind.


I have a spare set of L1V2's to try this out with. If you don't mind me asking, why would the change to a 1/4" smaller tweeter dome help? I understand that they'll stay omnidirectional until ~ 18khz instead of ~ 14khz, but is there another benefit other than this?



Fast1one said:


> 2. Ditch the vifa and go 2-way with the Anarchy, start with an acoustic crossover around 2khz. Due to the loss in response you may want to start with a first order electrical on the DXT around 5khz or higher and a 2nd or 3rd order electrical on the Anarchy around 2khz. This link is a very good reference for that application: The Seas ER18DXT ported two way


I'll give this a shot as well, do you feel that the CTC is too far between the tweeter/woofer in my current cabinet to try this out?

Thanks so much again, I value your knowledge and advice a ton.


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## Fast1one (Apr 6, 2007)

katodevin said:


> Firstly, you have a million thanks for responding with your advice. I really appreciate the learning opportunity. I did have a few questions/points for you to elaborate on if you havetime time.


Sure, I would love to help.



katodevin said:


> I agree, looking back, I would have gone with a bit larger mid, maybe one of the H-Audio guys. I was very impressed with the Viva's though, even when running them full range on my test bench. Also, I'm not married to a specific crossover point, so I plan on experimenting.


First of all thanks for giving your impressions on the vifa full ranges. I've been wanting to try those as a set of low power computer speakers for a while.


katodevin said:


> Is the poor power response you are referring to going to be caused by the smaller mid? In my testing, the mid got more than loud enough for my application/liking and stayed very smooth throughout my test band of 400hz - 4000hz. I do not have a full grasp of what contributes to poor power response in this case, so if you could shed a bit of light, I'd really appreciate it.


Poor power response does not have anything to do with the performance of the mid itself. It has everything to do with the geometry of the mid. What I mean by power response is the frequency response if you were to average the on AND off axis response. In other words, averaging measurements at 0 degrees, 10, 20 ,30 40, etc. 

If you recall, the point where a speaker begins to beam has everything to do with the diameter of the piston and NOTHING to do with the performance characteristics of the driver itself. You can get a rough idea by dividing the speed of sound (1118 feet/s) by the effective piston diameter (convert to feet)*2. This corresponds to the half wavelength cancellation frequency. In your case with a 2.25 inch cutout:

Fbeam=1118[feet/s]/(2.25[in]/12*2)=~3000hz 

I haven't confirmed this, but I believe the data sheets for the 2" and 2.5" were switched. You know why? The larger driver beams at a HIGHER frequency and has LESS low end response, which doesn't make sense. I believe this is the correct data sheet for the 2.5": http://www.parts-express.com/pdf/264-1046s.pdf

Ignore the dimensions and the fact that it says 2 inch. Now notice something interesting around 3khz? The OFF AXIS response begins to taper off due to the inherent cancellation of the cone itself. If you imagine a cone made of thousands of little cones, you can imagine if you begin to move off axis this cancellation occurs. The larger the diameter, the lower in frequency that this begins to occur.

The idea of constant directivity waveguides is to MATCH this off axis response with the driver for a smooth polar (or power) response that tapers off uniformly with frequency. So if a driver is 6db down at 30 degrees at the crossover point, the waveguide is ALSO down by the same amount at the crossover point. 

Here is an example of a Behringer 2031P studio monitor which uses an 8 inch woofer with a 1 inch tweeter mounted on a waveguide a bit larger than the DXT:










Notice how the off axis response is very uniform? Its almost as if there isn't any crossover action going on its that good. The crossover point is a bit below 2khz. 

What happens when you go off axis towards the woofer?










Ouch, the most severe cancellation shown is at 22.5 degrees off axis in the vertical direction. This has everything to do with the ctc between the woofer and waveguide. This is inevitable no matter what, but you can do a better job at it with a smaller tweeter without a waveguide crossed over low. The response will be more polar (i.e. equal level as you move off axis) but there will be a larger sweet spot in the VERTICAL direction. 

It all depends on what you want. Constant directivity speakers reduce the amount of reflections in a room and INCREASE the sweetspot in the horizontal axis. Traditional systems with a proper crossover sacrifice a horizontal sweetspot (in regards to proper staging) for a uniform polar response in horizontal AND vertical response. If you move side to side with traditional 2-way, the image moves with you. Do that with a proper large constant directivity speaker and the image remains pretty centered.



katodevin said:


> I have a spare set of L1V2's to try this out with. If you don't mind me asking, why would the change to a 1/4" smaller tweeter dome help? I understand that they'll stay omnidirectional until ~ 18khz instead of ~ 14khz, but is there another benefit other than this?
> 
> 
> I'll give this a shot as well, do you feel that the CTC is too far between the tweeter/woofer in my current cabinet to try this out?
> ...


I posted my opinion in the post prior. Use a smaller tweeter so that you can get it CLOSER if you want to use the vifa. Use the DXT in a 2-way app with the Anarchy. Good luck!


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