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!
I used a 25W rms stereo receiver 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'

Bart

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.
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"and±1/4") 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.

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.

thanks Adrian

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.

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

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!  :)

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.

Thanks!  :)

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

B.

looks good, should get way lower than 38?

Nice work man
i think you can determine the f3 point either by ear (not accurate) or by expensive measuring equipment.

Thanks Adrian.

60, nice page, I'll have some tunes going tomorrow, if I find some time.

B.

here is a link I found tone generator software Bart : http://www.nch.com.au/tonegen/index.html
allows sweeps, volume levels, waveforms and single tones all at the touch of buttons.

I found your measurement levels from your db interesting - similar to mine in fact.
using the software mentioned above, I listened and determined

below 12Hz nothing

12 - 23 Hz very low volume but solid waveform (cant hear the low stuff - but can feel the air pressure and hear the house shake and rattle)

23 - 26 Hz -  significant not large peak (coincides with Fs of Driver?)

27 - 35 Hz Consistent volume throughout

35 - 70 Hz tuned peak of 4th Order Bandpass (highest volume)

70 - 110 Hz consistent flat solid lower volume than tuned

110 - 140 (depending on tuning of throat) resonance - nasty box ringing cutout by crossocer at 60 - 80 Hz


Thanks for all your help with achieving my end result - I love it...

My ears where not lying ♪♫
I just discovered this web page and maybe this will let you think twice before using a woofer horizontally.
http://www.subwoofertools.com/forum/sag.htm

I didn't shorten the rear chamber yet, so nothing new at the moment.
(It calculates in WinISD as needing 15.6l or 952inch³ or 0.551feet³
for the rear chamber in a 4th order bandpass box)

To be continued...
B.

Hello!

I've been gone too long and I registered with the same name as a few years back.

So here is an update about the DB10.
I left the DB 6½" longer then what the plans said. So now, finally, I have cut it off!
I get the impression that the sound is the same, maybe a little tighter but I'm not sure.
A nice DVD will reveal that. (suggestions?)

Pics of the cutoff will follow soon.

Bart