Subwoofer - Replacement Drivers

[Fatmarley]

Actually looks pretty good with two ports blocked. Port tuning frequency is 21hz and as a result, you get a flatter frequency response down to 20hz, and cone excursion is way down even with 150w. With the low port tuning frequency, port chuff isn't a problem either.

 

[JazzyG]

The single driver measures 8.6 ohms. 

The last graph you posted, with 2 ports blocked, something can't be right on that one.  Maybe I am misreading it, but how can that driver and amp combo possibly produce that 107 dB bump at 16-17 Hz?  Would be cool if it did!  Otherwise, that chart looks really good!  Would you remove the ports or just put a bung in them?  I suppose if I used bungs, I could experiment a bit with the 3 ports.

What software are you using?  Is there decent free software I can start to play around with some of this stuff on?

I see now how difficult it is to retrofit something like this, it would much easier from a design standpoint to choose a driver and build a cabinet around it.  Thank you for your patience in helping teach a noob how to go about a project like this!

 

[Fatmarley]

The single driver measures 8.6 ohms. 

The last graph you posted, with 2 ports blocked, something can't be right on that one.  Maybe I am misreading it, but how can that driver and amp combo possibly produce that 107 dB bump at 16-17 Hz?  Would be cool if it did!  Otherwise, that chart looks really good!  Would you remove the ports or just put a bung in them?  I suppose if I used bungs, I could experiment a bit with the 3 ports.

What software are you using?  Is there decent free software I can start to play around with some of this stuff on?

I see now how difficult it is to retrofit something like this, it would much easier from a design standpoint to choose a driver and build a cabinet around it.  Thank you for your patience in helping teach a noob how to go about a project like this!

The resistance of 8ohm woofers is usually around 5 to 7ohm, so they can't be 8ohm woofers. Probably more like 12ohm.

The 16 to 17hz bump is caused by a combination of the artificial room gain that I added (Just a guess based on my room dimensions) and the very low (21hz) port tuning frequency.

The software I use is free but you need Microsoft Excel to use it. It's Jeff Bagby (Rip) Woofer Box Model and Circuit Designer.

 

[JazzyG]

Awesome, thanks for the tip on Jeff Bagby's tools, I found them and downloaded to my PC.  I do have Excel, so I am good to go, other than it will take some time to learn, but should be fun!  I think I am just going to table the project for the time being.  Maybe the best thing I could do is just order the new foam surrounds and get them repaired, they don't appear to be otherwise damaged.  I will need to fix one grill and build a second one, to fully restore it. 

 

[JazzyG]

I tried modeling one myself, can you check my work?  Driver I used was the Dayton DSC205-4 wired in series.  Would you be concerned about the Xmax in the low 20 Hz range?

 

[Fatmarley]

I'm on my phone, so can't check properly.

Ql, I use 40 because I build my enclosures air-tight and Qa 120 because you shouldn't need stuffing in a small subwoofer enclosure.

Your ports are 16" long, so you'll need to tune higher until they're 11" unless you plan on extending them?

You may want to Google series vs parallel because some say series doesn't sound as good. I've also read that the signal isn't distributed evenly with a series connection, but I don't know how true either of those statements are.

 

[JazzyG]

Gotcha, thanks of the tips.  I wondered why it wouldn't let me set the port length, I have to manipulate the other inputs to get to the right length.  So, I ended up have to tweak a few setting to hit 11" on the dot, primarily the Fb.  I am not going to actually use these woofers, but I do like Dayton drivers, price is good, and they are only offered in 4 ohm so that is where the idea came from.  After the changes the frequency response looks a lot worse and it hits Xmax even sooner, not a good match.

I went ahead and ordered the new foam surrounds from Springfield Speaker Repair and a Subdude HT from Crutchfield for the Mirage.  Going to build a set of good quality RCA cables to go to the sub and try them out with my 'new' RCA LX-50's that I modded out in my bedroom system.  I think it will be a good match as I have the 'lil speakers sounding great, just lacking the weight a sub will add.

Thanks again for all your help!

 

[JazzyG]

My sub project is now complete, it looks and sounds great!  I had to build a replica grill as one was missing and also repair the one I had.  Foam surrounds installed and turned out great. I did some placement and tune dem tricks to dial in the balance with the RCA's and the room.  That said, this sub excited less nodes than usual, surprisingly flat in room response!  I kind of wonder if it being "bi-polar" smooths out the response similar to how 2 subs is better than one?

In short, the system sounds great!  Nice solid, tuneful, bass extension to around 25 Hz and blends in beautifully now.  So glad I didn't replace the drivers, they are really good.   I did cover the stamped steel baskets with Dynamat and did some custom bracing work.  I will post some more pics.

 

[JazzyG]

A couple more pics...  The metal brace I came up with really works, I can play Pop Smoke's 'Shake the Room' and I can't feel any vibration on the sides of the cabinet--solid!  I also added some good diamond foam I had leftover from my Classix II build.  

 

[JazzyG]

The diamond foam in its natural habitat...I went this route instead of adding any wool or fiber fill stuffing. 

 

[MF 1000]

I like the innovative use of a pair of turnbuckles as cabinet braces to make a constrained damping setup.

you could also experiment with a piece of ply etc attached to the turnbuckle to brace the rear of the driver, which would also be beneficial,

great work