DIY Speakers

Sam Denith Silver Member Username: Shaftofair Post Number: 117 Registered: Jan-07	Posted on Monday, March 26, 2007 - 23:53 GMT I intend to build a small pair of speakers for my computer to put by the monitor and just want to get as much as I can out of a system about the size of what you could buy from the store, but sounds better and can get louder. From what I know, I need good amplification, a crossover, some drivers, and building skills. My design goal is to achieve low distortion and high volume with crystal clear highs and deep bass with minimum size, maybe with speakers about the heigth of my monitor. http://www.bestbuy.com/site/olspage.jsp?skuId=8268475&type=product&productCatego ryId=pcmcat104900050012&id=1170290375980 I can use a sub if I really have to. Thanks for your help in advance. -Sam
Timn8ter Gold Member Username: Timn8ter Seattle, WA USA Post Number: 1205 Registered: Dec-03	Posted on Tuesday, March 27, 2007 - 00:09 GMT Take a trip over to DIYAudio. http://www.diyaudio.com/forums/forumdisplay.php?forumid=22 To prep you a bit; 1) Do you have any experience with electronic circuits? 2) Do you have audio measurement equipment? 3) Have you ever built speakers before? If you answer no to all those questions you should look for a good speaker kit or build an existing design.
Sam Denith Silver Member Username: Shaftofair Post Number: 118 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 01:20 GMT 1. No 2. Only SPL meter and tone generator 3. Only 2 8" drivers and a tweeter crossed over at 2khz - sounds OK, but not good, it's being powered by a cheap PA amp I bought at RadioShack. I want to do it up right this time. I've looked at that site and it seems 2 good 4-inch drivers and a tweeter with crossover in each speaker would do a good job paired with a subwoofer module behind the monitor. I may be leaping too far ahead though and I still need to look at existing designs and speaker kits first. In the meantime I'll look for drivers and things that fit that description. What are some sites that sell some speaker kits or show some existing designs? Thanks in advance. -Sam
Sam Denith Silver Member Username: Shaftofair Post Number: 119 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 01:50 GMT I think maybe going the bi-amp route on the speaks and actively equalizing might be an easier route? Here's what I have thought might work well. http://www.madisound.com/cgi-bin/index.cgi?cart_id=2723600.7674&pid=1707 4 in each speaker, 2 top, 2 bottom http://www.madisound.com/cgi-bin/index.cgi?cart_id=2723600.7674&pid=1005 2 in each speaker, in middle between woofers That would be crossed at 3khz. I'll get back to you on that. -Sam
Bytesiz Bronze Member Username: Bytesiz Bangor, Maine USA Post Number: 34 Registered: Jan-06	Posted on Tuesday, March 27, 2007 - 02:05 GMT Good DIY speaker designs can be found here http://www.zaphaudio.com/ In particular, you might consider these http://www.zaphaudio.com/audio-speaker18.html and a small sub.
Sam Denith Silver Member Username: Shaftofair Post Number: 120 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 03:04 GMT Bytesiz, I like the design, and think it'd do well if I didn't need high output, but I think I could get away with a variation on that design using the drivers I showed. I'm using a design program to compare drivers.
Sam Denith Silver Member Username: Shaftofair Post Number: 121 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 03:55 GMT Based on the graphs, I need a 5x12x20 in. sealed enclosure. Here are the calculated specs of that. 120w RMS Power Handling (<3khz) @ LF terminals 100w RMS Power Handling (>3khz) @ HF terminals Sensitivity (1w/1m) 95dB HF, 93dB LF -3dB down points: 55hz, 22khz 3-ohm HF, 4-ohm LF Max Calculated SPL: 110dB Does that look promising? It looks like it'll do well to me. I'm going to look at the subwoofer now. It's time to learn a bit about possibilities in that area to get the deepest bass and enough volume to match the speakers in the smallest enclosure possible. Input Appreciated -Sam
Nuck Gold Member Username: Nuck Post Number: 6496 Registered: Dec-04	Posted on Tuesday, March 27, 2007 - 04:05 GMT Sam, rated impedence of 3ohm and 4 ohm are taxing on an amplifier. Getting it up to 6-8 would make things easier.
Sam Denith Silver Member Username: Shaftofair Post Number: 122 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 04:17 GMT I can just rearrange the wiring to make it 6-8 like you suggested Nuck, along with a doubling of damping factor -Sam
Sam Denith Silver Member Username: Shaftofair Post Number: 123 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 05:56 GMT It took me a while to find a suitable driver for minimum box size, maximum output, but I found one. The speaker surface area would suggest a single 12" subwoofer, but since I can't do that for space reasons, I decided to use 4 8" drivers in a dual isobaric configuration to achieve the same box size as a single 8", but the output of 2 8" in a box twice the size, so it'll fit behind the monitor, and have the output of a 12". It'll quadruple the power handling using the TB 16mm Xmax 8" TB drivers I chose ($70 each). The box should come out to be 9x20x9 which should fit perfectly behind the speakers and monitor at the 80hz crossover I plan on. Here are the calculated specs. 2000w RMS Power Handling Sensitivity (1w/1m) 81dB -3dB down points: 25hz, 1khz Max Calculated SPL @Xmax (30hz):109dB Peak Calculated SPL: 120dB The possible impedances could be 1-ohm, 4-ohm, or 8-ohm. Re .8ohm, 3.2ohm, and 6.4ohm, respectively. Including construction materials, the sub and speakers combined come to around 1 grand. I'd say that's pretty good considering the specs and size for $250/speaker and $500 on the sub. It looks like it'll do a great job if I can supply the power. Speaking of power, can you recommend me some amplifiers for the sub and speakers? You've seen the specs and hopefully you can recommend some amplifiers so I can get the best out of this system when it's all together. I don't think pro amps are the way to go here. I just need to try and make the budget of $500 for amplification...unless I have to spend more for better built amps or the power I need or something. I just don't want to completely overdo things. I've kept it small enough to fit around my monitor, but in order to do that without losing SPL or SQ capability I had to make it inefficient. Thanks for help on this dilemma of finding enough power without going bankrupt. -Sam
Sam Denith Silver Member Username: Shaftofair Post Number: 124 Registered: Jan-07	Posted on Tuesday, March 27, 2007 - 09:28 GMT I've done a lot of searching and can get a Rane active equalizer which controls crossover frequencies, HF, LF, and Sub level and all the cables needed to connect between computer and amps for $300. All I need now are some power amps and then I can order all the stuff and put it together. I was looking at these. Rotel RB-1070 (on woofers) Rotel RB-1050 (on tweets) If you took the subwoofer out of the equation, then it's $1800 for the 80hz+ region. The sub will add 500 on and all I need is a powerful amp. I probably don't need high-end for driving <80hz so a pro amp should do fine. I was thinking 2 Behringer EP-2500s would do nicely amplifying the subwoofer channel (1 on each isobaric) giving a total price under $3k for a very nice computer audio system which will satisfy on movies and music, even at very high levels. Unless anyone has any reasonable objections, I'll be ordering all the parts sometime in the next week. It's going to be fun playing some computer games now that were worthless on this monitor's speakers. -Sam
Andre Money (---None of it) Gold Member Username: Arande2 Extreme SQ FTW Post Number: 2042 Registered: Dec-06	Posted on Tuesday, March 27, 2007 - 14:17 GMT 109dB output at 30hz with a computer system? Dude that's twice as loud as my sub I blew could get, but yours also costs $300 more than mine did. You better use good wiring and connectors internally on the speaks and sub haha. Can I have that RadioShack PA amp? Ok I probably don't deserve it.
Sam Denith Silver Member Username: Shaftofair Post Number: 125 Registered: Jan-07	Posted on Wednesday, March 28, 2007 - 05:05 GMT It's all on order and should be on the way along with an upgraded sound card. Andre, check your messages. -Sam

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