Tolerances

[jonedd]

In retrospect, this query may sound like that of a troll...but maybe some good will come out of any discussion.

I just built my first pairs (2 designs) of speakers. I did the best I could with unit conversions and best substituted materials. I also hired out the designs to be made exactly as specified, for 4 pair total. After listening to each of the end products, I can't really hear any difference ('though the difference is quite visible).

So, I'd like to ask those who have heard experimental designs and drivers placed in cabinets originally made for other T/S drivers, what they think the tolerance of a particular speaker design specification is.

I was pretty careful. My build was probably within a few percent of the calculated design. If that's good enough, then DIY speaker building is well within reach of even the novice, and some of the very specific suggestions on this board should indicate that "hey, this is me just trying to be perfect..." Otherwise, maybe I need to focus more on my source, my room, or get better drivers before trying to perfect woodwork.

[rjbond3rd]

Hi jonedd,

What do you mean that you can't hear any difference? Between what? Most designs are not that tolerant -- you get okay results initially but over time, the deficiencies become more obvious.

[Conrad Hoffman]

I'm not sure I fully understand the question, but in general this isn't a "few percent" business. IMHO, it's desirable for channels to match to that level, but we're working with parameters that simply aren't known to that level, or even if measured with extreme care, aren't that stable over time and with varying power levels. As far as woodworking, if you can hit 1/16" tolerances of panel dimensions, that seems plenty close enough. What's more important is the shape of the box.

CH

[jonedd]

Sorry for the unclear question. I definitely can hear a difference between the two different box designs. I was just in the midst of trying to cut wood for a new project. I was spending an awful lot of time trying to get the dimensions exact due to unit conversion from metric to English units, and trying to predict movements due to glue etc... I just started thinking that I was being too anal retentive for what was needed. Obviously blemishes would be visible, but for a prototype, I just wanted to see if others thought minor errors would audibly change the sound enough to turn one off of a particular design.

It also occurred to me that maybe my middle-Fi electronics were just making subtle differences harder to perceive. I don't have a lot to compare to, so I don't know.

I should probably have just let the idea drop, but I'm always thinking that I could have done things better.

[madtecchy]

Hi Jonedd

Stick in there this is the first set's of speakers you have built. Stick at it and over time and with help from the members of this forum you will gain knolage and expirience. If that is what you want to do of course .
Best Regards Mad Mark

[jonedd]

I'm not getting discouraged--I'm actually having a lot of fun just playing around. I'm just trying to temper my compulsion to compete with computer controlled machinery.

I promised my wife I wouldn't bring anything shabby looking into the house, so until I can veneer well I'm doomed to lose to the cabinetmaker. I'd like to say at least my work sounds as good...if I can keep myself from getting too much testing equipment.

[planet10]

How well a design tolerates changes in T/S parameters depends on the design. I tend towards making my designs fairly tolerant, since drivers of the same type can have quite a spread (+/- 20% on some is not unusual), and then there is the situation that an individual drivers parameters change depending on the drive. Not only where you have the volume set, but also, with the dynamics of the music.

dave

[jonedd]

Sometimes I can be a bit silly. I actually adjusted one of your (P10) designs' vent widths, because 1/4" spacers are a bit thinner than the 7mm you specify...only to find after the glue was added it would have been nearly perfect. Then when I put the box together I found gaps and proud ends and all that stuff one would expect on a first project, which made me feel terrible about the build quality. In the end, they sound OK, so I'm going to move on building my little speaker army.

[bentoronto]

Hear differences? Speakers next to one another? Blind test? Microphone? Same feed?

Move your speakers (or your head) a few inches and the sound changes.

Repeat any listening test with the identical set-up and your "impressions" change.

So first, make sure you are measuring/listening correctly. Piece of cake, if you understand the challenges. And you don't need a lab.

Footnote: here's a pretty good test for matching - listen to the speakers kind of like headphones at 18 inches from each ear. Localizations shifting?

[Squeak]

About the finish: Just wrap them in felt. Buy some spray-on glue or put a very thin layer on with a brush and wrap the felt around the cap before you put in the drivers. There are various ways to finish the top, but that's the tricky part. You can use a back-painted glass plate as the easy option, or you can make diagonal triangles that you felt together after gluing.

Why felt? In no particular order: 1. Because you don't need to use 80% of your building time to sand off and finish the cap to super anal degrees before painting. 2. It improves the sound. It attenuates vibrations and surface waves. 3. It's a very resistant finish. It won't get scratches or get nicked easily. If you should get a tear or a small slit it's easy to felt over by using a small piece of spare felt and a bit of soapy water to re-full the felt. 4. It looks damn good. Find a nice colour of real sheep wool felt and you get a speaker that really feels much more like a piece of furniture and blends with a normal living room.