Impulse Purchase/Design

[mpotoka]

Well I will be picking up a new soundcard for making measurements with, and I just felt the need to pick up some drivers to test. No idea how this will go, since it is only my 2nd design. This time I'm going to try to do a simple 2-way. I also haven't seen anyone use the Dayton DC25TS-8 yet, so I figured I'd give it a go. I then ordered a couple of buyout 6" shielded cast frame woofers. Part Number 299-818. My wife is absolutely going to punish me for this, since I am *supposed* to be getting our house ready to sell. I'll fit it all in somewhere. I will tell her they are a present for some of our friends we are going to leave....

I have a pile of XO parts in a box from working on my previous design, I will attempt to use parts from there only. The DC28F-8 would match from a sensitivity standpoint (at least from published specs) but that has been widely used, and if nothing else getting some data on the DC25 will be interesting.

BOM so far: Prices Each

2 Dayton DC25TS-8 (shielded) 275-055 $10.00 x2 = 20.00
2 Buyout 6" Cast Woofer (shielded) 299-818 $17.63 x2 = 35.26
2 Dayton 5.5uF Poly Caps 027-425 $2.27 x2 = 4.54
2 Dayton 1.0uF Poly Caps 027-410 $1.06 x2 = 2.12
2 Dayton 10uF Poly Caps 027-428 $3.75 x2 = 7.50
2 Jantzen .55mH 20g Inductor 255-038 $4.32 x2 = 8.64
2 Jantzen .85mH 18g Inductor 255-244 $6.95 x2 = 13.90
2 Dayton 10 Ohm Resistor 004-10 $1.25 x2 = 2.50


Total = $94.46 + shipping

Crossover Schematic. Just a note, this is not the "ideal" crossover, it was modified to deal with the leftover parts I had.



And this is the simulated response, along with what was actually measured. Blue is simulated, Red is measured (gated at 1m) Note I removed the Lpad I thought I needed.



Estimated Delivery for Friday. I should have a good weekend

[mpotoka]

Got the M-Audio Solo up and running, got the drivers from UPS this afternoon. Here's what I'm looking at so far:

DC25TS-8 Impedance



PE Buyout 6" Cast Fram Woofer Impedance



Changed design to a sealed box, to have a smaller speaker. It is 9" wide, 12.5" tall, and 12.25" deep (with a 1 1/2" front baffle)

Now to make some MDF dust!

[TacoD]

Did you get your delivery? Good luck with building .

[Gir]

Got the M-Audio Solo up and running, got the drivers from UPS this afternoon. Here's what I'm looking at so far:

I'm going with a yes

This looks like an interesting project, can't wait to see some FR plots.

[TacoD]

I'm going with a yes

This looks like an interesting project, can't wait to see some FR plots.

Thanks, you can see that English is not my first language

[mpotoka]

Well Sunday is my day to not work, and to play. That includes making some boxes and taking some measurements. Should have something to post tomorrow.

Does anyone know, can I do distortion tests with Speaker Workshop? Yes--sorry I was too lazy to google.

[mpotoka]

Well I made it. Speakers in a day, well almost. I had some more issues with Speaker Workshop and my new soundcard, but I think I have it worked out now. Well I finally got started making my dust about 2:00 PM, and I'm sitting here listening to the finished products (almost) at 2:30 AM. I need to voice the speakers with my Lpad yet, but with the family sleeping I can't do too much listening right now. I altered my design a bit. I wanted a small baffle, so I went with a 9" wide, 12.5" tall, and 12.25" deep sealed cabinet. The woofer should be seeing about .5 cu ft. After installed, I ended up with an Fc of 60hz.

The box was *very* tight to get the two drivers on and my 1.25" roundover. The drivers are all flush mounted, the tweeters are 5/8" offset from center to help with diffraction.

Tomorrow I will figure out my lpad, and take some pictures. For now here is a couple of graphs. First, the axis measurements for the woofer and tweeter. I must have had some goofy reflections on the tweeter 60 degree. For the most part, I was pretty happy with what I had to work with.






I chose to cross over at 2200hz, 4th order LR, 2nd order electrical. This graph shows my intended slopes. This is also a picture of the merged nearfield/farfield. The amplitudes are not a direct comparison, the tweeter is actually more sensitive, and needs to be attenuated.



You can see the big hump around 2k, which was expected from the baffle simulations.

[mpotoka]

I just had to put in a preliminary thought that I really like how they sound. Considering I had design my xo around parts I had around the house, I am quite enjoying this DC25T Tweeter....

[Gir]

How's that peak at 2kHz? Maybe a notch filter is in order. Looks pretty good, though. Nice job at getting it done in a day!

[mpotoka]

How's that peak at 2kHz? Maybe a notch filter is in order. Looks pretty good, though. Nice job at getting it done in a day!

Well I think I have taken care of it most of the way--can anyone steer me to a good notch filter calculator? The one I tried to use seemed to give some outrageous values.

Here's a couple of pictures... With the Lpad attached it is still a pretty minimal crossover. I will put a BOM together after I measure and make sure the values are correct for the lpad.







The more I listed, the more I am really enjoying the sound. I am seriously tempted to pick up another 4 woofers and 2 tweeters and make a vented MTM version. Running them in series should make them a little more amp friendly, and increase the power handling as well. I still need to take an impedance measurement with the XO in place...

[mpotoka]

Well I took an impedance measurement and some FR measurements at the listening position. Could I really have this much low end gain going on in this room??? It just doesn't seem right to me.

It is 1/10th octave smoothed, no gating.



And the impedance curve of both speakers, I feel they are quite close to one another.



I guess these are pretty amplifier friendly as it is. Perhaps I should test the sensitivity as well. All I have is a radioshack meter, will that work? I know I need to measure 2.83 volts at the amp, what type of signal should I do? MLS at 1000 hz

[Gir]

Heh, I doubt you're hitting 10Hz with that little guy 8O

Looks like you could bump the woofer down 3-5 dB. That peak at 2kHz didn't really show through too much, not too bad for the price!

[mpotoka]

Heh, I doubt you're hitting 10Hz with that little guy 8O

Looks like you could bump the woofer down 3-5 dB. That peak at 2kHz didn't really show through too much, not too bad for the price!

DOH! I just packed up all my gear. I just finished putting about 3-4 db attenuation on the tweeter Pretty easy to pull that Lpad off, but I'm not getting all the stuff out again right now.

I actually may have a misleading graph there. As I'm sitting here listening to some music, something doesn't sound right at all. I take a look, and the jumper cable hooked up to the tweeter on the left speaker came loose. I don't know if this happened before/during/after measurements Another day, just going to sit and listen for right now.

I did attenuate the tweeters a bit too much I'm sure, but I was supposed to have about a 2 and 20 ohm resistor. In my box, I only had some 2s and 16s. It looks like on my simulations that having a 20 there would be more appropriate, just didn't have it. Considering I'm out of pocket only about $70 for these, since I had MDF and all the XO parts sitting around, I think they turned out fantastic.

[mpotoka]

Well just added this information to my first post. I looked at these measurements again and removed the Lpad. Not sure what made me think I needed it...



Blue is the sim, Red is the measure. This is the XO I am using.

[Gir]

Wow, that looks great! How much smoothing did you use?

[mpotoka]

Wow, that looks great! How much smoothing did you use?

That is an on-axis gated measurement, spliced with a nearfield measurement, with 1/10th octave smoothing. Here is the raw nearfield + on axis measurements.



They are spliced at 750 hz