GRS 15PF-8 subwoofer not sounding the way i thought it would

Hello,

I have built a subwoofer box for the budget subwoofer "GRS 15PF-8" and it didn't turn out the way i wanted/expected it to, let me explain. I have installed winisd to do some calculations on what box/port size ect. I have watched some tutorials from "Diy Audio Guy" on what parameters I should look at and what they should be. And I came to the conclusion that a box of 50x50x50 cm =125L or a little over 4 cuft minus the subwoofer air replacement is about 4 cuft and a port of 4x50 cm of 50 cm long gets the tuning frequency's matched up pretty well. This configuration gives a Transfer function magnitude graph that looks like this
1691996514087.png

with almost an 16 db gain at 29 hertz. Now here's the problem: I built this subwoofer box and it does not sound like this AT ALL!! It more sounds/feels like the 16 db gain is at 60 hertz instead of 29 hertz. I have taken it outside to ensure it is not something with my room and it shows the same results outside. I don't know what i did wrong here and i would really appreciate any answers to what it possibly could be.

Nanno Haasjes

ps. the amplifier i'm using is the skytek spl 500 (a little overpowering it i know)
 
Ouch.
With Qts=1,39 this driver if hardly suitable for good sounding vented box.

The result is different beacuse 50cm long vent has theoretic fundamental resonance at 172Hz. Thats too close to Fb and will cause inerference.
In practice, vent resonance will be even lower for two reasons. First, end-correction makes its effective lenght longer. Second, due to interaction with air in the box.

In simple words, you made chambered transmission line, not vented box. No wonder you got weird results. If you model your box in Hornresp it will show you.
The only thing I can recommend is to try to put some stuffing in box and vent.
Sorry for bad news.
 
Hi Davor,
I'm really sorry to hurt your fealings, but i might hurt your feelings even more by asking what theoretic fundemental resonance is. Is there a video findable online that explains this in a clear way? Or is this the frequency of sound you hear when you blow over a tube or bottle? Again i'm sorry to hurt your feelings by beeing some noob in diy audio.

Another question: is wool a good stuffing in any way?

Thanks for your reaction!
 
This is one of those woofers that one wonders what the hell they were aiming for?
High Qts, very low xmax and also not great efficiency for a 15 inch woofer.
So pure a a PA mid, it's also not gonna do much.

I think there a much better options for around 40 euro or a budget subwoofer.

The only way to make this work somehow, is just active EQ'ing.
But don't expect much from it either.
Adding a bucking magnet would probably help a little bit as well.
 
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Again i'm sorry to hurt your feelings by beeing some noob in diy audio.

I have nothing against you, its just my way of communication. What I mean is what I say.

I simulated your box in Hornresp as chambered TL and unfortunately it shows what you can hear. Big bump 50-60Hz.
Than I made second simulation as vented box and results below 200Hz are very similar. Again big bump 50-60Hz.

Long vent dont have big effect below 200Hz so my quick explanation about chambered TL isnt correct in this case. The bump is drivers high-Q resonance in the box. I can post the sims if you want.
It looks like your simulation is made with wrong drivers data which, of course, gave wrong result.
I took the data from this site:
https://www.parts-express.com/GRS-15PF-8-15-Paper-Cone-Foam-Surround-Woofer-292-415
 
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Errr. are you sure that your ears are calibrated in frequency and level?
Then there's also the room influence which can (and often does) attenuate LF.
The only intelligent way to make sure what the woofer actually does is hitch a mike to your PC or soundcard and run REW or ARTA or any of the usual suspects.
You could be on a totally wrong path.

Jan
 
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to davor: i have gotten the data from this site https://www.soundimports.eu/nl/grs-15pf-8.html and it seems to be the same

to jan: as i said earlier i have taken it outside to eliminate room issues and it is such a big difference that any body could feel it. at 60 hertz i can hardly sit in front of it and it feels weird if i talk while at 30 hertz i need to put my head in the cone to even hear or feel it.
 
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to davor: i have gotten the data from this site https://www.soundimports.eu/nl/grs-15pf-8.html and it seems to be the same

to jan: as i said earlier i have taken it outside to eliminate room issues and it is such a big difference that any body could feel it. at 60 hertz i can hardly sit in front of it and it feels weird if i talk while at 30 hertz i need to put my head in the cone to even hear or feel it.
Are you saying that you hear the lows outside and not inside?
Does that not mean you have a room issue? If so, that will not change with a different driver/speaker.
Unless I misunderstand what you say.

Jan
 
60 hertz i can hardly sit in front of it and it feels weird if i talk while at 30 hertz i need to put my head in the cone to even hear or feel it.
These are Hornresp sims. They show the same.

1. Black line as vented box, gray line as chambered TL.
Almost identical below 200Hz. So, my first assumption was wrong. Long vent isnt the cause for 60Hz bump.
GRS sim1.jpg


2. As vented box.
Black is driver output, gray is vent output.
Dip in driver response shows tuning frequency. Its 27Hz beacuse vent effective lenght is longer due "end correction".
Peak in drivers output at 50-60Hz is clearly visible and thats the main problem.
GRS sim2.jpg


I tried to replicate the result from your simulation in #1. The box has to be at least 10 times bigger, 1250 Liters and more.
 
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I think there a much better options for around 40 euro or a budget subwoofer.

If you have a reference of a 12" in more or less this price range which is ok to take a Linkwitz transform ( sealed so a bit of xmax) and ok quality/price ratio i will happily take advice!

Except for some car dedicated subwoofer ( more than double the price Alpine or Focal bugdet ) i've not found many possible options in EU. There is one STX model but nobody seems to have used it and can give advice about it in here...