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Playing around, the cheap way. (pics) (Read 16967 times)
Bart_West-VL.
Ex Member



Playing around, the cheap way. (pics)
08/06/07 at 22:41:03
 
The weather was not to good, so dug up the DB10".
I removed the isobaric loaded Bose drivers (8" 8 ohm)
And replaced them with one 8" 4 ohm Pioneer driver, the only survivor from a set of three-way car speakers.
Very cheap, it's true I admit it.  ::)
I have proof here:  :D

The driver had a hole in the center, because there was a small tube coming out of it, fixed to the magnet, that held the mid an tweeter driver, also broke off in the car-crash (don't worrie, that was about 12 years ago)


That hole needed to be sealed.
Just used an old CD, cut a disc out near 1" diameter, glued it on with super glue, fast and dirty.
Then I melted a little dampening material for car doors on that (black tar?), so it wouldn't vibrate and it lowers the fs a tiny bit aswell


This driver is designed to be built in, but I wanted to attach it with the front on the baffle, so it needed two rounds of weatherstrip.


old Bose-driver out:


Pioneer driver in:


There's a lot of filling in this box, full of it!:


I tryed to measure the resonance frequency and it seems to be at 45hz, the baffle sits flush with the opening.
This was all tested in the middle of the room, on a table, so the resonance freq might change when put in the corner on the floor, faced backwards. But I doubt it.
After that, i'll see if I can tune it better/lower with the baffle moving in front of the hole.

At first it sounded very quiet, really disappointing, then I knew...
The resistor was still in there, to measure the resonance freq. phew! Wink
I used a 25W rms stereo receiver Shocked and NO filtering at all.
The little speakers that played the rest of the spectrum also had no filter at all!
I had the luck of loaning an old scope from a friend, it revealed that there was distortion from 2.5W up at 45hz  :o

But I must say, for an old 8" driver ... it didn't sound bad at all!
I hope to play more tomorrow, prediction says 'bad weather' Wink

Bart

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Gexter
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Re: Playing around, the cheap way. (pics)
Reply #1 - 08/07/07 at 02:20:50
 
Your my kinda guy.
lots of playtime with stuff laying around!
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #2 - 08/07/07 at 19:14:24
 
Update and two questions:

I moved the DB10" to the place where I (some day) want to put the HouseWrecker.
The resonance didn't change, as I expected.
When I wanted to push the baffle down, it was not moving.
Out came two pieces of wood and a third one across them on top.
Then came the 4 pound hammer.
Even now I had to hit several times, quite hard!
OK, suddenly it moved about a half an inch, woohoo!
New test signal, what the f...hell!?!...
almost no sound and not really bass at all.
A quick look at the scope showed nothing like a sine wave at all!
The basket had deformed and it was ready for the junk yard.
Being a cheap bastard, tried to REform it, he he ! lol!
took a thick piece of wood, smacked at the basket on the side I thought it was 'needed' and yes! it worked!
unbelievable...
Re soldered the wires, replaced in the DB, put a 10 Hz tone to it...aaah no noise, for once that's a good thing. Smiley
Back in business:

with the baffle down in front of the partial moon about a good half inch (14mm) it had a resonance of 42 Hz.
More down and leaving about 33 mm free of the partial moon (about 1"andą1/4") it resonated at 40 Hz.
I stopped there for now, because of the questions I have (at the end of this post)

for fun I turned the frequency up and it resonated again at about 120 Hz in the last setting, so a cross over of 120 Hz is too high for this sub! Use 80 Hz max or it will give a louder peak around 120 Hz.

Another fun thing to know:
Without the lid on, it resonated at 27 Hz!!
Don't do this with high power, I think it would kill the driver!

I have two questions for the experienced DB-builders:
1. What do you use to seal the baffle after tuning, so that it easily is removable afterward, because I didn't like when the driver coil rubbed against the magnetic gap!

2. How much space is needed minimum between the baffle and the end of the partial moon?
At this stage I have 33 mm. If it can be tuned to 35 Hz without compromising the air flow, that's what it will be tuned at.

One thing that didn't work out good is, that the bass is not loud where I sit in the sofa to watch the TV.
I know that turning the DB facing the wall is better, is this also true for the HWK? Bottom ports facing the wall?
oops, that's three questions, sorry!

B.
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #3 - 08/07/07 at 21:50:53
 
I did it!! I f'n fried the sucker, hahaa!!  ;D

turned it up to hear any distortion (no scoop this time)
there was no distortion audible!
so the volume stayed on -0db (full open)
there was wind a feet away from the box, no I didn't fart!
But only for half an hour.  :(
wow, all that from a 8" cheap driver

What will I fry tomorrow?...

to be continued...  ::)

edit: that wasn't with the 25Wrms receiver, it was a 140W amplifier.
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« Last Edit: 08/08/07 at 09:32:07 by Bart_West-VL. »  
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #4 - 08/08/07 at 19:57:47
 
If you all don't like the reports and pictures, no problem, I'll stop right now.
But could anyone answer the questions that I asked, please?

1. What do you use to seal the baffle after tuning, so that it easily is removable afterward, because I didn't like when the driver coil rubbed against the magnetic gap!

2. How much space is needed minimum between the baffle and the end of the partial moon?
At this stage I have 33 mm. If it can be tuned to 35 Hz without compromising the air flow, that's what it will be tuned at.

One thing that didn't work out good is, that the bass is not loud where I sit in the sofa to watch the TV.
I know that turning the DB facing the wall is better, is this also true for the HWK? Bottom ports facing the wall?

B.
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Adrian
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Formerly known as
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Re: Playing around, the cheap way. (pics)
Reply #5 - 08/09/07 at 06:26:16
 
1. i covered mine in leather and had a lot of extra strips which i glued on the seam between the outer box and the insert. silicone could be better to use if you're not sealeing it permanently.
2. not sure how much is minimun. maybe go as low as you wish untill it start to sound muddy
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« Last Edit: 08/09/07 at 06:31:32 by Adrian »  

Too much bass never hurts, or does it ?
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #6 - 08/09/07 at 10:06:53
 
thanks Adrian
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60_and_up
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kids should live.

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Re: Playing around, the cheap way. (pics)
Reply #7 - 08/09/07 at 15:21:01
 
i use caulk to seal. its can be removed if i have to.

i have used a db with the insert 1.5" from the end with almost all the half moon coverd.

dont be afraid to pust it all the way to the end, it might work.and if you dont try, youll never know.
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #8 - 08/09/07 at 15:45:33
 
Now it's at 1.3" so that's even less space.
I first will get a woofer somewhere, instead of these cheap 8" one's I'm trying, I'll go for a 10".
If they have a 12" that can get in there, I might even try that.
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« Last Edit: 08/09/07 at 15:46:06 by Bart_West-VL. »  
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dalfe5
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Re: Playing around, the cheap way. (pics)
Reply #9 - 08/09/07 at 19:40:04
 
to seal the baffle i something i bought at lowe's.  it's like caulk in a roll.  i think it is actually called a cord.  it soft enough to push into the cracks and seal it off but does not dry and get hard or stick to the wood.  never had a problem with air leaks.  when you remove it you can roll it back out and reuse it.  almost like play-dough.  very cheap, maybe $3.00. i have the box at home if you want me to get the actual name and part number.  it was in the section with the foam seal/tape.
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #10 - 08/10/07 at 10:55:09
 
That's good news, I'll have to check the stores if they have something like that.

I went to the audio store yesterday and brought a 10" woofer back, didn't have to pay it yet, so I can try it out and bring it back if it doesn't work.
Did a simulation in WinISD and it spit it back out as being to high tuned. -3dB point was at 43Hz in a 4th order band pass Sad

Now I'll put it in the DB10" and see what it gives.

If anyone is willing to have a look at the parameters and tell me what's wrong with what parameter, I'll be very glad.
http://www.monacor.de/int/en/produktseite_suche.php?artid=2005&spr=EN&typ=fu...
What are the determining factors anyway? Vas? Xmax?
This way I can look for a real candidate for the DB10"

All suggestions are welcome!  :)
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #11 - 08/13/07 at 13:30:26
 
The 10" Monacor sounds very good, didn't expect that at all! Shocked
I can get two of these drivers for a good price and so I will clamshell them in the box.
- Can anyone confirm that this would lower the fs or not?

One thing that is a pity, it sounds hard pounding when standing in front of it, but when I'm moving around the house, the bass is not loud.
Is there a reason for this, is it just the box?
I was hoping to use it for HT at the moment, until the HWK is built.

Does anyone have the DB and the HW compared, in the house? What are the thoughts on this?
The room here is 36'x12'x7.8'

Thanks!
B.
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Bart_West-VL.
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Re: Playing around, the cheap way. (pics)
Reply #12 - 08/20/07 at 19:07:29
 
Tomorrow I'll have the second woofer.
I hope to find some time, this week, to complete the install and make everything leakproof.

If someone is willing to give my previous post a look, I'll be glad to get some answers to those question.

Thanks, B.
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60_and_up
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kids should live.

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Re: Playing around, the cheap way. (pics)
Reply #13 - 08/20/07 at 21:00:59
 
Bart_West-VL. wrote on 08/13/07 at 13:30:26:
The 10" Monacor sounds very good, didn't expect that at all! Shocked
I can get two of these drivers for a good price and so I will clamshell them in the box.
- Can anyone confirm that this would lower the fs or not?

One thing that is a pity, it sounds hard pounding when standing in front of it, but when I'm moving around the house, the bass is not loud.
Is there a reason for this, is it just the box?
I was hoping to use it for HT at the moment, until the HWK is built.

Does anyone have the DB and the HW compared, in the house? What are the thoughts on this?
The room here is 36'x12'x7.8'

Thanks!
B.


1.clamshelled plays lower in smaller box
2.its about locating the sub in the right place(in the right place you get bass almost eveywhere, try MANY different locations for it)
3.hwk provides a lot more bass in a house but db sounds better in a car.
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« Last Edit: 08/20/07 at 21:09:56 by 60_and_up »  

Peace hath higher tests of manhood than battle ever knew. ...
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Bart_West-VL.
Ex Member



Re: Playing around, the cheap way. (pics)
Reply #14 - 08/21/07 at 20:08:50
 
Thanks!  :)

Didn't do anything this evening, was hanging in the bar, drinking beer with the seller of the woofer.
Maybe tommorow.

B.
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