Bookshelf speaker mod

[lontas]

Hi all,

I'm brand new here and am totally new to all this. I've been browsing the forum for a few days and have found a lot of helpful answers. I thought I'd start off by showing you my first project: Converting my cheap Sony bookshelf speakers into something much better sounding. I have some pics and some questions.

First the pics:


The original speaker. Cheap plasticky woofer, cheap styrofoamy tweeter. First, I must replace the drivers with something better.


Old drivers removed. Hmm, there isn't much damping material in there. Perhaps I will add some at a later time. As for the crossover, looks like the woofer connects directly to the amp, and there is a single 1.5 uF capacitor on the tweeter.


Uhhhh, looks like someone ordered the wrong size tweeter! D'oh! Not to worry, Dremel to the rescue!


I sawed out a larger hole for the tweeter. It might not look beautiful, but looks were never the point of this project.


New drivers installed. The aluminum woofer is the 5-inch MCM 55-1855, and the titanium tweeter is the MCM 53-572. Again, I know it looks impatient but I really don't care about the looks in this case. For now, I kept the same capacitor as the crossover.

The sound is already 10 times better, but still needs some work. The tweeter is 5 dB more sensitive than the woofer, making the speaker sound too bright. I will install an L-pad and cut it back by 3 dB. Also, the 1.5 uF capacitor is cutting out too much of the high-mids for my taste. I will replace it with a 4.7 uF capacitor, which should cutoff at around 4000 Hz. That might seem low for a tweeter, but I'm trying that because that is where the woofer begins to naturally roll off, so it seems like a good fit.

Now the questions:

1. Damping material. In an enclosure of this size, will adding it make any meaningful difference? It appears that this enclosure is not built to the golden ratio and lacks the proper cabinet depth. I might add a layer of damping material onto the back, to acoustically increase the apparent depth of the cabinet. Does this reasoning sound okay?

2. What about ditching the single capacitor and designing a proper crossover network? Will there be any meaningful benefit to adding an inductor coil or a Zobel filter to the woofer? The woofer seems to have a natural rolloff as is so I'm just curious about whether I even need these things in this case.

Thanks,

Chris

[owdi]

The best advise I can give you is dump the high endurance and upgrade to red zone, it's worth it.

Dan

[idaho]

I would have to say...have fun while doing this but I think that if you really want to do this as a DIY project, then DIY your own cabinets specific to the woofer you have using WINISD or some box modeling program. Try to build your crossovers on your own using whatever you learn online and from audio forums such as these. If you don't get disappointed. Good! Just keep learning and having fun. If you get frustrated about your build's sonic quality, build a proven design. Gets you motivated to keep learning. Learning curve is pretty steep but you will get there if you hang around and have patiencw. I laugh at my first attempts to build speakers. I am not there yet but I laugh less at my efforts now! It's an addicting hobby.

Good luck!

[idaho]

Here's a tool for you to play around with too for you crossovers!

http://audio.claub.net/software/jbagby.html

Here's a sample of a box modeling program.

http://www.linearteam.dk/default.aspx?pageid=winisd

And oh! Read some books too! For example:
Loudspeaker Building 201
Loudspeaker Cookbook

I am done posting for the year! Maybe!

[Shaun]

Hi lontas

Your efforts remind me of how I used to do things when I first started DIYing. Even today I still buy old loudspeakers just for the cabinets, for housing my own drivers. Needless to say, they are rarely the right size! Here's one such effort: Tripoly

Suggestion: Model your mid/bass in both your present enclosure and the ideal enclosure (using WinISD as recommended above) and compare. Then decide if it's a good idea to keep your present enclosure.

Good going...

[lontas]

Dan, I thought of trying that, but in a recent double blind test very few participants were able to smell any difference.

Chris

[Thawach]

The best advise I can give you is dump the high endurance and upgrade to red zone, it's worth it.

yes, i believe because he begin to come in to hi-fi world. he must spend a little time for each day to learn. if that anyone suggest him with the program. i will say that's not red zone but it's dangerous zone.lol dan i find a lot like this in thailand website. they ask...ask=a lot ask how to use every program but don't know about basic design.


Shaun u bring me to Africa website. now i fill that i want to drink a water.lol


regards all guy

TW

[lontas]

Hey, those are some handy programs, idaho! Thanks for the links.

I just installed 4.7 uF Dayton capacitors on the tweeters. With the tweeters now covering a wider frequency range, the need for attenuation is all the more apparent. I've got 4 resistors coming in the mail that will become L-pads to reduce the tweeters by 5 dB.

That said, the sound is surprisingly good as is! Bass sounds quite accurate down to about 60 Hz. I don't care if these speakers aren't perfectly flat. The idea was that I wanted better bookshelf speakers without doing major woodwork (and hopefully without frying my amp). I figure I'll eventually build a pair from scratch and then keep these as surround speakers.

Thanks for the tips,

Chris

[Ron E]

Those Sony speakers aren't that bad, but there are sample-sample variations that lead me to believe there is no quality control program in place. I bought some for computer speaker thinking they would be better than the plastic cabinet usual junk - and they were.

One of mine has a dip at ~3k and the other is actually pretty flat.

I like playing around with cheap speakers - here is a site that may have some speakers in your means - our local audio club had a speaker design contest using inexpensive drivers: http://www.audiomn.org/2008diyloudsp...esignchallenge

[owdi]

Originally posted by lontas
Hey, those are some handy programs, idaho! Thanks for the links.

I just installed 4.7 uF Dayton capacitors on the tweeters. With the tweeters now covering a wider frequency range, the need for attenuation is all the more apparent. I've got 4 resistors coming in the mail that will become L-pads to reduce the tweeters by 5 dB.

That said, the sound is surprisingly good as is! Bass sounds quite accurate down to about 60 Hz. I don't care if these speakers aren't perfectly flat. The idea was that I wanted better bookshelf speakers without doing major woodwork (and hopefully without frying my amp). I figure I'll eventually build a pair from scratch and then keep these as surround speakers.

Thanks for the tips,

Chris

In addition to the lpad, you could try adding a parallel inductor to the tweeter. A small gauge air coil around .4 - .8 mH will help.

Flying blind can be fun but you have a much better chance of building something decent if you start with a proven design. Some places with very well documented projects are:

www.rjbaudio.com
www.zaphaudio.com

Dan