|26th March 2017, 09:07 PM||#1|
Join Date: Feb 2014
Location: Indianapolis, IN
Custom MinDSP 2x4 enclosure build
This thread is fairly lengthy, but I wanted to take the time to explain the decisions that led up to the need for this build. Stay with me as I promise it’s worth the read, or at least I hope it is. I have done my best to document AND link to the parts used for this project, but over time some links may become broken. Please refer to the item numbers and google them to find additional suppliers if needed.
I have tried to break this thread up into sections. The Backstory & Problem, Solution & Project design, and then Build pictures. Jump to the last post if all you care about is the pics.
“Call me Ishmael”. Lets start with a quick introduction about me. I’m a *bit* of an OCD person, who works in IT for a living (go figure right).
*Edit* Ok, I’m let’s be honest, I’m a MASSIVELY OCD guy who overthinks everything to the chagrin and annoyance at times of friends and family. I don’t start a project or buy anything without researching it till I drive myself batty, and then sit indecisive wondering if I am making the right decision. I’m sure reading this thread in its entirety you will come to the same conclusion.
*Back on topic*
I have been slowly acquiring DIY subs with the goal of increasing the ULF in my large room. I’m a basshead at heart and have always appreciated tight musical deep bass.
Problem: Need MOAR ULF!!!!!
Research: How do I get more ULF
In order to increase the ULF in my room I realized that I either need large ported boxes tuned low (10-15 Hz), or sealed boxes and a TON of power. The pro’s and con’s of Ported v Sealed sub were researched ad nauseum and eventually a consensus was reached. Mainly it was based on the fact that my wife isn’t a fan of large ported boxes, I didn’t have a ton of room to build one even if I wanted too, and if I did build one it would have to be smaller than I wanted resulting in a compromise in performance which I couldn’t accept (see there’s that OCD coming out). That left me to look at sealed subs of a large cone size with a ton of power thrown at them.
Sub Build: Determining the right sub and enclosure size
Looking at subs, it was fairly easy to see, given my research, that a lot of cone surface was needed to get where I was hoping to go. 12 and 15 inch subs weren’t going to cut it without 4 or more drivers, which was cost prohibitive. 18, 21 & 24 inch subs were viable options, with 2 likely getting me “close” to what I wanted. 21 & 24 inch subs would require large boxes, even sealed, given their circumference. Additionally the cost for them tends to be somewhat steep for the obvious reason that most are in the “made to order” category.
Another factor is that I lacked the woodworking tools to build a box, so ordering a flatpack, or buying a custom made one was a MUST. The largest kit available at an affordable (to me) price was only available for an 18 inch driver, which made the 21 and 24 inch subs not a viable option IMHO.
That led me to look at 18 inch, and after again a ton of research in WinISD (again there is that OCD) it was determined the best driver option was the Dayton Ultimax 18. It also helped to know that someone like Mark Seaton was using the same stock driver in his builds in a similarly sized box.
At the time of purchase the intent was to buy 2 of these kits total, however for reasons I won’t get into that didn’t happen. I bought a single Dayton Ultimax 18 flatpack kit from parts express and got it built with the help of a friend. A second one of these never materialized, but what did happen is that at a later date an additionally DIY sub box was purchased which consists of 4 x 12 inch Infinity drivers. When these drivers as a single system, wired for 4 ohms were modeled in WinISD, they had simulated performance very similar to the Dayton Ultimax that was already in use.
That left finding the right amp.
Researching the “right” amp FOR ME:
In researching amp options, it was quickly apparent that the most used option was a pro amp as opposed to a plate amp. The benefits of this are that more powerful amps can be purchased in the future without any modifications to the sub itself. So plate amps were out.
In reading up on pro amps in DIY builds, lots of folks were very happy with DIY subs paired with nuke DSP model amps. The issue’s I saw with the iNukes were largely the fact that they are IMHO ugly as heck, and the fans are loud enough to almost necessitate replacing the stock fan. Realizing that there were mainly issues for me, and not ones most people encountered as the iNukes are intended for pro use. In the pro audio realm the super bright LED’s make it easy to see the display at night, and the fan noise is minimal as they are normally placed far away from the people and speakers. There are always problems when you take an item not intended for a consumer HT setting and attempt to make it work in one. For 99% of folks replacing the stock fan, spray painting the front and covering the lights with tint would have solved those problems. But again my OCD kicked in. Not a fan of modifications that void warranties, and not trusting myself to do a decent enough job (for me) on painting it a different color, that left both QSC and Crown amps as possible options. QSC was eliminated due to again high fan noise, leaving just the Crown.
Crown amps had a very good reputation, overall and had a fairly decent aesthetic to them. They also allowed for RCA OR XLR connectors to be used, as well as speakon AND regular speaker wire. To me this was a big plus, giving me lots of options. They had just released the Gen 2 models, and being budget minded, after seeing that the differences were small and IMHO not worth opting for the newer model, the decision was made to go with a XLS Series 1 amp. Additionally, after seeing the XLS2500 bench tested, its specs were fairly inline with the manufactures published specs. This put to rest the main unknown about Crown amps in a HT setting, which was if they had implemented a 12db per octave filter in the amp starting at 20 Hz. You could read responses online from folks stating one way or the other, and I even contacted Crown myself and was told there was one there. The bench tests proved otherwise.
Problem: no programmable DSP in the Crown XLS
The problem with the Crown XLS series was that it was missing the ONE feature the iNuke DSP line had that I considered of value, and that was a programmable software based DSP. While XT32 in my Denon did a decent job of calibrating subs, The OCD basshead tweaker in me, wanted to install some shelf filters to attempt to lower the F3 of my boxes, or just add some sub 20 Hz boost. Neither of which the Crown had by default.
Solution: Aftermarket DSP, which to choose
That flaw lead me to look at existing options to add DSP to the equation for not a lot of money. The options I saw were the Antimode, SMS-1, MiniDSP and AS-EQ1. The Antimode and AS-EQ1 were removed from the running as they are mainly automatic EQ’s and wouldn’t not allow much customization. The SMS-1 lost out in that it just didn’t have nearly the feature set that the MiniDSP had.
The MiniDSP I needed was the 2x4 balanced. The Mini-DSP is the REAL reason for this thread.
__________________________________________________ __________________________________________________ ____
Research: MiniDSP 2x4 balanced
The MiniDSP 2x4 balanced in and of itself was a great product. It allowed me to add custom EQ to my setup, I’d used the 2x4 regular RCA version previously for subs and it worked quite well. The problems I have with the Balanced 2x4 are things I’m sure were intentional on the part of the designers in order to drive the cost of the unit down to a reasonable rate.
Problems: Exposed wiring + kids + dogs + cats = no joy.
I am on the whole NOT a fan of phoenix connectors. As a dad with 2 small kids, 3 dogs and a cat, it was just ASKING for trouble to have any type of exposed wiring. Additionally due to the small size and weight of the unit, it’s hard to place in a normal rack and not have it move around a ton when plugging in cables, etc. Additionally the board layout isn’t the best with the inputs, power and USB on one side and the outputs on the other.
In looking around for solutions to these design problems, I found a build on AVSForum in which a person build a custom enclosure to allow them to use regular XLR cables and keep any exposed wiring hidden. So I decided to do a very similar build.
I began researching what I would need for the build and decided I wanted the option of using either RCA or XLR connectors on the inputs, and then just regular XLR’s on the outputs. I looked around and read that everyone seems to love nuetrick connectors on the whole. Since I’d used them for the speakon connectors and also was impressed with their quality, I decided to try and keep everything nuetrick, which would ensure the look and finish of each connector was consistent.
In evaluating the weaknesses of the MiniDSP, and how I would have addressed them, the decision was made to try to find a chassis that was around 17-19 inches wide and at least 10 inches deep. This the width would allow it to not stand out near other gear as most equipment seems to be about 17 inches wide. The depth was to have some extra space for cable routing, and the option of adding additional pieces in later on if needed. Since my Crown amp is silver, the decision was made to continue that color with the enclosure chassis.
Finding a chassis that met this requirement was the hardest part, until I posted on diyaudio and within a few minutes had some contenders. After making a Visio schematic (I told you I’m OCD and I plan everything to the hilt) to ensure everything would fit, it was decided that the best option for a case would be the 1U chassis that was 270mm deep.
All the input, output and power connectors were moved to the back of the unit. Additionally a ground lift switch was determined to be something that would be nice, so it was added to the back panel. The front panel would consist of the power on/off button as well as a recessed connector for the USB connection to allow for easy access to the software.
I decided to do something that I hadn’t seen done before as well. The MiniDSP user manual (Section 4.3.1 – Wiring Tips) mentions you can wire RCA or XLR on the input side, so I decided to have the inputs on the chassis allow for both connection types, and have them each wired to a phoenix connector, of which only one would be in use at a given time. This allows a very easy switch later on if I move from using the RCA outputs on my Denon to say XLR outputs on a dedicated pre. All that I would need to do is pop the top, and switch which set of phoenix connectors were being used on the input side.
The following was the resulting parts list for this build.
2 x Neutrik NC3FD-L-1 "D" Series Panel Mount XLR Connector Female Nickel Part # 092-036
1 x Neutrik NF2D-9 RCA Jack Connector D-Series White/Nickel Part # 092-229
1 x Neutrik NF2D-2 RCA Jack Connector D-Series Red/Nickel Part # 092-222
1 x Neutrik NAUSB-W Feed-thru Reversible USB A/B Adapter D Panel Mount Nickel Part # 092-278
4 x Neutrik NC3MD-L-1 XLR "D" Series Panel Mount Male Nickel Part # 092-034
1 x Phoenix Type Connector 6-Pole 5mm Pitch 4-Pack Part # 091-374
1 x Slimline 1U chassis
1 x Balanced MiniDSP 2x4 w 12v PSU
15 ft Furez FZ162AA Analog Interconnect Cable Raw
TE Connectivity ALCOSWITCH Switches AV1911P712Q04 Part # 450-2271-ND - power button
Parts Express SPST Automotive Round Rocker Switch Black Part # 060-776 - ground lift switch (not sure if its this exact one we are using, but its close)
Parts Express IEC AC Power Jack Chassis Mount Part # 090-442
USB 2.0 Cable A to B Black 1m (3.3 ft.) Part # 130-040
I realized EARLY on that I lacked the skills to get this build going, so I asked my friend SCompRacer if he wouldn’t mind helping. He has built many projects and they have always turned out looking top notch. To my delight he obliged and has been slowly checking off the project punch list.
*Aside on the builder* To give a brief backstory on Rich to highlight just a few of his achievements, he’s built a DIY DAC built around the Buffalo kits that is second to none, in both fit and finish IMHO, as well as a tubed phono bottlehead kit. Now yes, it is a kit, but what makes his stand alone is the finish work. It’s beautiful finished in all its tubed glory. I imagine many a night is spent listening to it on his system in the dark with nothing but the dim amber hue of those sexy tubes as an indication anyone is in the listening room.
__________________________________________________ __________________________________________________ __
Below are pictures, in sequence of how the build proceeded:
Chassis holes milled out
Rear panel partially assembled and color coded:
From left to right: RCA & XLR Inputs (only one set used at a time) | XLR Outputs | Ground lift switch | IEC plug
From left to right: Blue LED backlit Power Button (not in this picture) | USB programming connection
MiniDSP 2x4 balanced in a box:
*Update* (Also added to the top section)
When Rich started to get ready to install the MiniDSP in the enclosure we spotted a problem.... Can you guess what it might be....
The solution was to remove the plug part and solder directly to the connections. We also decided to strip out the stock connector and use the included adapter to allow for easier install and wiring of the backlit LED in the powerbutton.
Then it was time to remove the MiniDSP board from its enclosure. 4 screws and a push later and we started to expose the board.
As a sidenote, the enclosure itself is VERY NICE and made of good quality stuff. I'd highly recommend purchasing the enclosed kit, even if you only need the board.
The wiring is starting to get there....
Pretty much done
And we have POWER!
The BEAST LIVES!!!!!!
Now we just need to do 1 thing.
Last edited by EndersShadow; 2nd April 2017 at 09:54 PM.
|2nd April 2017, 05:52 PM||#2|
Join Date: Feb 2014
Location: Indianapolis, IN
I'm 100% NOT SURE how to ground the board. We stumbled across this thread on the MiniDSP site which seemed to indicate we should use brass standoffs rather than nylon ones.
Any thoughts appreciated....
I think the plan right now is to use nylon standoffs and then connect a ground wire to the chassis..... but any help or thoughts on this greatly appreciated
Please note: We did not ground the XLR's to the chassis.
Last edited by EndersShadow; 2nd April 2017 at 06:03 PM.
|5th April 2017, 05:01 PM||#3|
Join Date: Feb 2014
Location: Indianapolis, IN
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