more DIY

jcaut

A work in progress, of course. What do you think?

Remind you of a classic Polk model?

BobMcG

Looking good!

Is this the reconstruction of a beat but complete pair or a build up from parts you've gatherd?

gatemplin

Nice JIG Jason.

jcaut

Thanks!

This is a from-scratch design, using some parts I had lying around. The midwoofs are Def Tech 5.25", and the tweeter is an Audax textile dome. At the bottom is a 10" passive radiator (thanks to RuSsMaN).

It's kind-of an experiment, obviously taking some design cues from the Monitor 10. The little 5.25's actually model better with a port, but I wanted to try the PR. Cabinets are actually some of the first ones I ever built, just with a new front baffle to accomodate these drivers instead of the Radio Shack drivers I used 10 years ago. They're veneered in cherry and after I refinish them I think they'll look nice.

I've still got to do some measurements and work up a real crossover, as well as tune the PR. At this point it sounds promising though.

Jason

VR3

Those arnt the drivers you saw in my speakers on my website.

Those are actually of better quality.

Those are the Vifa midbasses that DT used in the older BP8 models back in the early 90's. Def Tech did not manufacture those, pretty sure on that one. But I may be wrong, but I don't think they started manufacturing their own drivers until the BP10B line...

But anyway, awesome project!

Cabs look great!

Side Note -
Here is a center channel that uses those drivers.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=14992&item=5773030165&rd=1

Now, by the aluminum dome, which DT did manufacture, they may of infact actually manufactured the midbass as well. Maybe they modeled their midbass off the Vifa used in the line before it - I could see that I guess. But anyways, just thought you might like a bit more history on the drivers in your speakers there

jcaut

You're right, they're not the ones I saw on your site, but.... I'm fairly certain they're not Vifa's either. I think they're DT-manufactured. Someone on the PE board said they were used in the Mythos line. I know nothing about it really.

I know thery're pretty nice little drivers--- a little hard to work with as far as a crossover--- but nice overall. They're 4 Ohm, so I'm running them in series. It looks like it's going to result in a very easy to drive speaker.

jcaut

I just thought I'd bring this back up and give an update.

These cabinets are some I built years ago and covered with cherry veneer. I didn't do a good job finishing them back then, so I sanded them down and re-coated them with polyurethane. I cut the old particle board front baffles out and added a new MDF front, to accomodate the new drivers. The finish on the baffle is truck bed liner. I haven't decided yet if I'm going to bother making grilles.

I think I mentioned above that these were really an experiment, and I had no idea if they would actually sound good. The little Def Tech midwoofers have a dip in their frequency response centered at about 1500 Hz, followed by a rather pronounced peak at about 3000 Hz. This makes them a little hard to deal with in the crossover. To make matters worse, I paired them up with a little Audax TM025F1 textile dome tweeter that generally needs a steep crossover slope at 2700Hz or greater-- So I'd need to cross those midwoofers right there in their "problem" area. The passives ended up needing about 50 grams of weight added, to tune the box to about 50Hz. The predicted F3 is 47Hz, and they'll pump out pretty decent bass for their size. Once I get the cabinets fully sealed up, that should be even better. With the midwoofs in series, they don't work too awfully hard and these speakers will play pretty loud.

They suffer from some weird, off-axis lobing, probably the result of having the midwoofs side by side horizontally. They're a little on the bright side and could possibly use a bit more tweeter padding. Overall though I'm pretty happy with their sound. I'll have to listen to them longer to get a better feel for what they do right or wrong.

Here's a new "almost finished" picture.

Jason

jcaut

And here's a gated, "on-axis" frequency response measurement I took right after I hooked up the initial prototype crossover. The amplitude scale isn't calibrated, so the level doesn't mean anything really. I've tweaked it a little by ear since then, but I haven't re-measured to see what it did to the response.

Jason

jcaut

Just for the sake of comparison, here's an LSi7 measured in the same manner, just a few minutes after I did the other one. You can see that the overall sensitivity is pretty comparable. LSi7 is nice and flat. I'm not sure if the rising response at the high end is my mic.. It could be as it seems to be there, to some extent, in all my measurements.

ND13

That's pretty enough to market, if they sound as good as they look?

chenj16

wow, that's a beautiful piece of speaker! wonderful job!

steveinaz

Awesome buddy! I love this DIY'er stuff. Very cool.

PolkThug

NICE WORK!

michael_w

Is there a specific truck bed liner that you used? The finish is obviously not smooth but is it pretty bumpy? (picturing an actual bed of truck) From that picture it looks really really good and now I'm contemplating covering my sub with it...

ND13

Originally posted by michael_w
Is there a specific truck bed liner that you used? The finish is obviously not smooth but is it pretty bumpy? (picturing an actual bed of truck) From that picture it looks really really good and now I'm contemplating covering my sub with it...

I'm not sure which brand he used, but I would use Line-X, it has the best looking texture, IMHO, and I deal with sprayliners almost daily.

michael_w

The closest dealer of Line-X to me is about a one and a half hour drive each way... How do you apply the stuff? I see that you can bring in your truck and have them do it but not quite sure how to get it on a sub.

ND13

Originally posted by michael_w
The closest dealer of Line-X to me is about a one and a half hour drive each way... How do you apply the stuff? I see that you can bring in your truck and have them do it but not quite sure how to get it on a sub.

I would think that if you took your enclosure to them they would spray for you. I have no clue what they would charge, but seeing that most of what they charge for a bedliner is labor, I couldn't see it getting ridiculous. They wouldn't have to prep a bed or anything like that. I would call ahead and ask what they suggest to prep the enclosure with to make sure it adheres to the surface correctly.

jcaut

Thanks for the nice comments!

The bedliner I used was just the spraycan Duplicolor stuff from Walmart. About $7/can. Adheres great to lightly sanded MDF and even seals the cut edges in one coat, if they're sanded lightly.

Once you get used to how to spray it, it gives a nice finish. Here's a picture of it that I've posted before

ND13

That texture is pretty close to line-x and a ****-load less expensive, also.

michael_w

That looks pretty nice. I think I'll have to pop by the local hardware store and see if they carry it (if not I'll make a trip to home depot). It is almost like a black granite in the left side of that pic and would definatly null out any imperfections that would be clearly shown if I were to paint it with normal piant. Thanks for the info

I am going to the Northwest Audio Review on Saturday so maybe I'll see a finish there that I fall in love with

disneyjoe7

Nice work

BTW you can build a speaker for me any day

Shizelbs

Very nice quality work. Looks incredible. We'll have to exchange notes once I get my house and some woodworking tools.

organ

Excellent work, Jason. Beautiful speakers!

Maurice