Reengineer What I Already Have?

[Jack Tupp]

I have a set of BIC America DV62si speakers. Walmart type speakers that are about 110/pr. They obviously don't send shivers down your back with their sound but the tweeter is atrocious.

I am wondering if re-engineering the crossover might make it work better. The crossover looks like they cut more than few corners.

I don't know exactly what the drivers are. I think this is the tweeter:

Vifa D19TD-05 3/4" Poly Dome Tweeter | Parts-Express.com

I have no idea about the woofer. It's OD is 6.5" and it looks to be a poly cone. Maybe some one recognizes it.

Pictures:
imgur: The Simple Image Sharer

 

[prickears]

G'day Jack,

That woofer looks similar to Jaycar units sold downunder, but i'm not sure who actually breeds them, (HiVi?).

How far do want to go with this re-engineering exactly?

Mick.

 

[planet10]

SEAS also made/makes a version of the tweeter. Used in PSBs, Missions and a range of other boxes.

Can uou post pics of XO?

The back of the woofer cutout needs champhering and the box could use some bracing.

dave

 

[Jack Tupp]

I'd be willing to completely rebuild the crossover with good parts and even replace the tweeter if necessary.

Hi dave...theres 7 pictures on the link to the pictures.

 

[infinia]

How far do want to go with this re-engineering exactly?

Yup the $10K Q , ... it is what it is.


Or how much money and time do you want to invest this project vs how much satifaction you will get in return.
This stuff is a real time and money sink, but fun!

 

[planet10]

Hi dave...theres 7 pictures on the link to the pictures.

I can only see 5.

dave

 

[Jack Tupp]

I don't think any work on the boxes is in order as they are covered with vinyl.

I know there was a guy, Ed Frias, who did crossover mods on these for like 20 bucks. I contacted him a couple years ago to no avail.

The bottom end isn't a problem at all. The highs suck donkey balls.

Modifying the crossover. Rebuilding the crossover. Replacing the tweeter with something not expensive and rebuilding the crossover. I'm open to all that.

If you need info let me know what. If you need more pictures than the 7 I already posted above let me know.

I have no sound measurement equipment but a little electronics knowledge. Soldering components is no problem whatsoever.

 

[Jack Tupp]

Is this good enough?

imgur: The Simple Image Sharer

 

[prickears]

The back of the woofer cutout needs champhering and the box could use some bracing.

dave

These can be done simply with no ill effect on the vinyl covering, but a positive effect on sound quality.😉

Can you show how these xo components are wired?

Mick.

 

[Jack Tupp]

Crossover pics.

http://imgur.com/sS9by&XcY8T&n7Al4&1iVSW&lpXuX&BhsyC&fNKDk&KTZqB

Looks like a 3.3 uF EL
275 uF film cap
.5 mH inductor and another inductor with no marking whatsoever. I dont have a DCR meter.

I measured the resistor without pulling a leg up and get about 2 ohms.

The wiring on the bottom is woofer -pos-neg tweeter pos-neg.

 

[planet10]

Here is what we have from the info at hand (the lable on the LF inductor looks like 1.5 in the pic, but if you think it 0.5 just verify that (one of the XO guys can tell what value makes sense)

Resistor is labeled 1.5 ohm. A realistic value of the plastic cap is 2.75 uF.

Knowing DCR of the drivers wouldn't hurt (specs say 8 ohm nominal)

dave

 

[Jack Tupp]

It does look like a 1 in the picture but it's definitely .5.

DC ohms on both right around 8.

 

[planet10]

The text-book XO calculator indicates an XO 4.2-4.2 kHz.

dave

 

[Jack Tupp]

What do I need to do to tame this thing?

 

[prickears]

Resistor is labeled 1.5 ohm. A realistic value of the plastic cap is 2.75 uF.

dave

*My best GUESS*, if cap is 2.75 then L maybe .56mH, for XO around 4k.
.5 mH with c=3.3, Woofer low Q crossed around 3.5k.(?).

Again XO guys could verify, but it seemed logical at the time!😕

Mick.

Could the problem be woofer cone break up? 4k could be a bit high for this woofer, no?

Mick.

 

[Jack Tupp]

Here's the box dimensions if you need them:

5/8" MDF

Inside dimension

7 3/4" wide
7" deep
13" high

The port is a funky oval with a bar 1/2 way across inside the opening. It's like a rounded hump. You can see it in the pictures if you look closely. It is also cut at an angle inside

Port Dimension

2 1/4" wide
1 1/2" high
4 1/2" total length


Pictures:

imgur: The Simple Image Sharer

 

[planet10]

What do I need to do to tame this thing?

unbraced 5/8" MDF -- you might want to glue some edge on 0.75"x1.5" battens (vertical) on the 3 largest surfaces & then coat the inside with some sort of fiberglass/epoxy resin.

Perhaps a bit more radical (but also a nod to Mick's comment about the mid-bass) is an approach i've taken a number of times... toss the tweeter, run a 4" chunk of PVC from the tweeter cut-out to the back, grab a reasonable 3" out of the drawer, slap it into the tweeter hole and move the XO down to 300-400 Hz.

dave

 

[prickears]

Ok, with an fs of 1700 that tweeter is less than ideal.

I'd bet a pretty penny they don't like being driven hard. What you are probably hearing is cone breakup from the midwoofer and the tweeter is probably still getting too much grunt at fs, both of which can give a very nasty harsh sound, among other things.
How to fix it?
As Dave has already pointed out bracing them can't hurt. You could use a better matched tweeter (lower fs), and lower the xo frequency to more like 2.5K. That will help, but, at the end of the day, those loudspeakers are still built to a price, (more background music, than party). As such, just don't ask too much of them!

Mick.🙂

 

[kevinkr]

You might want to try a felt diffraction ring around that tweeter particularly since it is not flush mounted. Walmart sells felt in the craft section for <$1 a sheet that would work..

Also I noted that two out of the three mounting screws on that driver are missing - that's not going to help at all as I would expect the tweeter mounting flange to buzz/rattle against the baffle board.

How about a picture of the components on the X-O as well, this would give us a clue as to the quality of the parts used. FWIW I was surprised to see an X-O pcb in such a low cost speaker, it looks like there is a little pretense at quality at least.

An inexpensive multimeter that can do LCR measurements would be very useful. You can pick these up on eBay for as little as $30 - and it would allow you to figure out the values of all of the components in the X-O.

What are you driving these speakers with - are you certain that the amplifier's HF performance is not contributing to the problem? I will admit it is not a particularly inspiring looking tweeter, so perhaps replacement will net you an improvement.

 

[Jack Tupp]

You might want to try a felt diffraction ring around that tweeter particularly since it is not flush mounted. Walmart sells felt in the craft section for <$1 a sheet that would work..

Worth a shot. I'll try that out.

How about a picture of the components on the X-O as well, this would give us a clue as to the quality of the parts used. FWIW I was surprised to see an X-O pcb in such a low cost speaker, it looks like there is a little pretense at quality at least.

I've already posted a picture of each component in the threads above. Are you guys not able to see all the pictures? Maybe it's a browser issue with their cookies or something at imgur.

What are you driving these speakers with - are you certain that the amplifier's HF performance is not contributing to the problem? I will admit it is not a particularly inspiring looking tweeter, so perhaps replacement will net you an improvement.

I've have a Mini Aleph and a Kingrex T20. The source is flacs through an AMB labs Gamma2 DAC.


Would these tweeters be an improvement?

Vifa BC25TG19-04 1" Textile Dome Tweeter 4 Ohm | Parts-Express.com