Want cheap? Want easy? New ultra-budget desktop monitors.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Johnny,

What are you using to draw your crossover schematics? I use MS Visio at work, but have nothing here at home :(

ExpressPCB. Click the download button at the top and install it. You will want to run the "ExpressSCH" version from your start menu.

I will send you a generic file, if you like - it can be a pain starting from scratch trying to find the various symbols for components.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Attached is the generic file I use to build my schematics. Right click context menu is pretty helpful. Double-clicking an item opens up an editor where you can change properties etc. Actually, it is a very nifty little cad program.

You will have delete the ".txt" off the end of the file.

[PWR RYD]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Awesome! Thanks Johnny!

[hipcheck]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Johnny,

Thats just a 2ohm to pad, and 3.3uf to cross over 6db. Do you have a freq resp plot of just the tweeter?

Tweeter:
4.7uf box type MKP, and 0.37mh 18g, and 1.5ohm to pad (this is installed on axis in the A-piller of my wifes car) 3000-3500hz I guess?

Woofer:
WAY off axis in the door, I tried the following:

1mh crossed over I guess 1000-1200hz or so 6db
and also 0.25mh, and 6uf poly-cap 3000hz maybe?

I would like to see what you think, I know that you have both speakers. I think you have also measured both. I just dont think the tweeter is right at that 12db setting. I will measure soon, but I just dont have the measurement system done yet. I have all the parts and software set-up, just no time yet.


Thanks for your time,

Steve

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Johnny,

Thats just a 2ohm to pad, and 3.3uf to cross over 6db. Do you have a freq resp plot of just the tweeter?

Tweeter:
4.7uf box type MKP, and 0.37mh 18g, and 1.5ohm to pad (this is installed on axis in the A-piller of my wifes car) 3000-3500hz I guess?

Woofer:
WAY off axis in the door, I tried the following:

1mh crossed over I guess 1000-1200hz or so 6db
and also 0.25mh, and 6uf poly-cap 3000hz maybe?

I would like to see what you think, I know that you have both speakers. I think you have also measured both. I just dont think the tweeter is right at that 12db setting. I will measure soon, but I just dont have the measurement system done yet. I have all the parts and software set-up, just no time yet.


Thanks for your time,

Steve

I started off with a variety of 2nd order electrical filters, and until I got to about where you are at they all had a major resonance in the 3-7k area. Switching to a simple 1st order electrical smoothed everything out. You are on the right track with the (relatively) high value inductor - anything under ).30 mH that I tried created that nasty resonance.

Being as this is as budget a project as even I am willing to undertake, that ruled out anything other than a 1st order electrical.

If you are using that little woofer that far away and that far off axis, I would try running it full range and see what happens. My measurements showed it to be relatively smooth in the upper end, and (now is when I wish I would have saved the plots) under ~3kHz, you had to get pretty much 90 degrees off before it started dipping below 3db from reference. Nice little driver as long as you do not expect to rattle windows with it.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Front view of the baffle:

Rear view of the baffle:

Finished product:


I have decided, after three or four projects, that the PE buyout "Beech" vinyl is purt' near worthless. Maybe have to re-wrap these and use some glue in addition to the peel and stick adhesive.

These are destined for my home office, and will probably live out their days playing the type of music my nine year old daughter listens to. Too bad, they sound pretty decent.

[mintos]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Those tweets are out of stock now... too bad I didn't buy more. Still need to find spl and zma files though.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Those tweets are out of stock now... too bad I didn't buy more. Still need to find spl and zma files though.

I don't really have those files. On this project, I just started building it lol. Hook stuff up until it sounded good, more or less.

[mintos]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

agreed, don't particularly need to be exact with cheap projects. Maybe I'll try one of those stock XOs on PE

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

agreed, don't particularly need to be exact with cheap projects. Maybe I'll try one of those stock XOs on PE

I would honestly try running the woofer full range and use a 2-4 uF cap on the tweeter and tweak with a resistor.

[benhinkle711]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

I have decided, after three or four projects, that the PE buyout "Beech" vinyl is purt' near worthless. Maybe have to re-wrap these and use some glue in addition to the peel and stick adhesive.

Johnny I have used the Beech a couple of times. A piece of advice I would offer is to do a 3/8 roundover on the corners. The adhesive isn't really strong and has a tendency to peel on hard corners; with the roundover however I've had no issues. Besides the adhesive issue I really like the Beech.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Day two of listening, and I am really liking them. They get a little strained at higher volumes, but that is very likely my simple high-pass crossover. If a guy was willing to spend 3x as much on caps and coils than the tweeter cost, I believe the tweeter would take quite a bit of power. As it is, they were too cheap to spend a ton of money on components, so I did what I did.

The little woofers really shine as more of a midrange with some bass duties, rather than as a "woofer" per se. Then again, I have not really been impressed with the bass out of anything under 5" before so maybe I am just nit-picking. With the 100uF series cap on the woofer circuit, they still have reasonable output to 150 Hz, and they seem to be pretty clean to that point as well. If a guy wanted to build these into a bigger box, say around 0.15 cubic feet I think they would be more satisfying. I was targeting as small as possible for use in my home office - unlike my desk, they have to share space with the scanner, printer etc. Small was priority one.

A shame about the tweets being sold out! The Vifa OX would be a natural replacement, but then the project cost almost doubles
For the curious:



My TechTalk album.

[robwest]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Nice! I don't think you could have bought comparable from BB at the investment cost. Seems to be getting harder to do. I like your drawing BTW, what did you do it on?

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Nice! I don't think you could have bought comparable from BB at the investment cost. Seems to be getting harder to do. I like your drawing BTW, what did you do it on?

AutoCAD 2002 for the dimensional drawings, and ExpressPCB for the schematic drawings.

Thanks for the kind words, and no - I don't think I could have gotten this at Best Buy. Anymore though, it seems you have to browse the buyouts/clearance/DOTD to compete in the under $100 category.

[johnnyrichards]

Re: Want cheap? Want easy? New ultra-budget desktop monitors.

Added a write-up to my website.