[evilskillit]

I just rememberd yesterday I have some speakers laying around from a year or 2 ago when I tried to ressurrect some old Translinear Systems speakers and it went badly. I put the speakers upstairs but last night I realised that I put some perfectly good 12" drivers in them, so I went up in the attic, got them out, brought them downstairs and googled the part number.

I'm going to build a serious seb or several serious subs next year but I would like a woodworking/speaker building project in the mean time to keep me busy but my budget is basically nothing for the rest of the year. The speakers are Goldwood GW-1244 speakers, 12" 4ohms. I have 2 of them and I want to make some subs to go with the bookshelf speakers I'm building. The bookshelves will be finished this week and I would like to get started on these subs to go with them. I know these speakers arent ideal but they're laying around so I dont have to buy them or pay shipping for them.

So the goal of this project is to build a pair of subs out of these GW-1244s for bottom dollar. Plate amps are pretty much out of the question because they can't be had for under $100 each, which is way too much for this project. I'm sure I can get a cheap amp and hook them up to that from somewhere, I can probably get one for free or next to nothing from a friend. But then I need a Low Pass Filter, either a crossover style to go between the amp and the sub or an active one to go between the pre-amp and the amp. Whichever is cheaper or easier to use.

My bookshelves are 8ohm speakers so I could wire each one of the subs in parallel with my bookshelves and my Parasound HCA-1000 would see them as a 6ohm load and that would be fine, then ofcourse a passive x-o would be required. Hrm, actually that would be 2.6666 Ohms wouldnt it. I'm still learning some things so someone tell me which one is correct.

Lastly I don't have enough info on the TS Parameters to get a good box design from WinISD. Partsexpress has some TS parameters posted but not enough. I'm going to shoot an e-mail off to Goldwood but I don't really expect to get any more info so if someone could help with box sugguestions it would be much appreciated. Here's what PE has for this speaker.

Specifications: *Power handling: 100 watts RMS/140 watts max *VCdia: 2" *Le: .60 mH *Impedance: 4 ohms *Re: 3.6 ohms *Frequency response: 30-1,500 Hz *Fs: 30 Hz *SPL: 90.9 dB 2.83V/1m *Vas: 4.22 cu. ft. *Qms: 3.30 *Qes: .86 *Qts: .68 *Xmax: 5.0mm *Dimensions: A: 12", B: 11", C: 5-3/16".

To see the most complete TS Parameters I can find just search partsexpress for GW-1244. I would post the link but I dont have enough posts to be allowed to post links yet. Also if you want to see what bookshelf speakers I'm paring them up with they're the Vifa Tweeter version Microbes from RJB Aduio. You can see the origional Microbes at RJB Aduo web page and the Vifa Tweeter version by googling "Vifa Microbe" and following the first link from "somethingawful" web page.

Thanks in advance for any help.

 

[thxgoon]

Re: Need advice on how to use speakers I have laying around.

I don't have the means to model anything for you at the momemt. From initial inspection 5mm xmax and a 30hz Fs won't get you earth shaking bass but I definitelly understand using what you have! It's very possible for you to get some great sounding bass out of this project. I would recommend another amp to drive the subs. Running them parallel with the bookshelves puts you in dangerous impedence territory and won't give you any control of the level of the sub relative to the bookshelves.

 

[evilskillit]

Re: Need advice on how to use speakers I have laying around.

Getting another amp wouldnt be a real problem. I could either DIY one, Ive been considering that anyways because I like to build things. Or I could get something cheap from ebay or a local pawn shop or maybe a friend. I dont expect earth shattering bass out of this, what I'm looking for is something to keep me busy for a few days and give me some good musical bass to get me by till next spring when I'll probably get an ep-2500 and some shiva-x or something.

 

[evilskillit]

Re: Need advice on how to use speakers I have laying around.

I just tried modeling an enclosure for the speaker using the resources from this web page.
http://www.ajdesigner.com/speaker/index.php
And for a ported enclosure it recommends a 550 litre enclosure and for sealed it recommends likea 2000litre enclosure. I dont know much about speaker building yet without the aid of a programm but those numbers seem odd to me.

 

[Mike P.]

Re: Need advice on how to use speakers I have laying around.

The best you can expext from this sub is 4 cu.ft. tuned to 20 hz. It might handle 50 watts, probably less. SPL will peak at 107 db at 50 hz, and drop to 101 db at 30 hz and 96 db at 20 hz.

 

[evilskillit]

Re: Need advice on how to use speakers I have laying around.

So ported then? I could give that a shot. What would be the best way to impliment a low pass filter on these things?

 

[thxgoon]

Re: Need advice on how to use speakers I have laying around.

The best you can expext from this sub is 4 cu.ft. tuned to 20 hz. It might handle 50 watts, probably less. SPL will peak at 107 db at 50 hz, and drop to 101 db at 30 hz and 96 db at 20 hz.

101+6 at 30hz if he were to build two and co-locate them. Not too shabby!

 

[evilskillit]

Box Size

Ok I punched everything into Winisd and checked 4cu-ft tuned to 20hz and then tinkered with it. The sub seems to gain alot from going with a bigger box. However due probably to not having enough parameters to plug in I can not get a graph for the cone excursion. So do you recommend 4cu-ft because the sub would exceed its max excursion trying to play below 40-30hz? Or to keep the lumber cost down or what?

 

[Mike P.]

Re: Need advice on how to use speakers I have laying around.

The bigger the box the less power it takes to reach Xmax, thus less overall SPL. At 10 cu.ft. Xmax is at 20 watts. In 4 cu.ft. Xmax is at 50 watts.

 

[evilskillit]

Re: Need advice on how to use speakers I have laying around.

Ok thanks for explaining that. How about sealed, the response falls off fairly quickly but having 2 of them would probably make them loud enough and I could EQ them a bit. The sound should be very tight and musical. But would you recommend against that because of the low power handling of the speakers since sealed enclosures tend to be much less efficient. Since these things are so weak I'm not even really concerned about having super low bass but just making them more musical. The bookshelves I built start dropping of at 100hz and will play to 50 but not very well. So having sealed subs EQd and playing from maby 35-40hz to 100 or something might sound pretty good. I guess unless someone says that sounds like a good idea I'll buy some lumber tomorrow and start on a pair of slot ported 4 cu-ft boxes.

 

[Mike P.]

Re: Need advice on how to use speakers I have laying around.

In 7 cu.ft. sealed the sub is at Xmax with 20 watts, there is no room to EQ the low end.

the goal of this project is to build a pair of subs out of these GW-1244s for bottom dollar.

Go with 4 cu.ft. tuned to 20 hz. Let us know how it turns out.

 

[thxgoon]

Re: Need advice on how to use speakers I have laying around.

If you're worried that a ported design would sound less musical, don't be. As long as you design it and construct it properly it should have less distortion then a sealed design. You can always plug the ports if you decide you don't like how it sounds.

Power handling is 100 watts, as Mike says you hit xmax at 20 watts sealed, so not only are you losing output from ports, you are limiting the potential of even higher output.

 

[evilskillit]

Re: Need advice on how to use speakers I have laying around.

Allright, thanks for all the help I'll probably get started on them this week and see if I can get some pictures posted.

Btw can you guys tell me how you were figuring when this thing would exceed xmax? I put all the TS parameters I had into WinISD and it would not give me the excursion graph. I assumed this was because I was missing a TS parameter that would be required to figure this out. Were you figuring it out manually or are you using a different piece of software?

 

[evilskillit]

New Development

Got an e-mail from Goldwood today, and attached was a document with the complete TS parameters. Very helpful of them to respond so promptly with the requested information. For this Goldwood is aces in my book.


Parameter Value Unit / Notes
Effective Piston Area (Sd) 525.88 cm2
Free Air Resonance (Fs) 29.7 Hz
DC Resistance (Re) 3.6 Ω
Mechanical Q Factor (Qms) 3.301
Electrical Q Factor (Qes) 0.863
Total Q Factor (Qts) 0.684
Voice Coil Inductance (Le) 0.6 mH/milli-Henrys
Equivalent Air Volume ( Vas) 119.6 Liters
Moving Mass (Mms) 93.2 Grams/Mmd + air load mass
Suspension Compliance (Cms) 307.85 µM/N/micro-Meters per Newton
Force Factor (Bl) 8.477 Tm / Tesla-Meters
Sensitivity (SPLref) 90.9 dB/Reference 8Ω/2.83Vrms
X-Max 3.0 mm

So now I can punch everything into WinISD. Awesome, however the X-Max is now only listed a 3mm which means the speaker exceeds this at a mere 12 watts of input in any type of enclosure. So at this point who knows what will happen, I might not be able to do anything at all with these speakers. But I have them laying around I'm going to build them and use them and they'll either work or blow up, at least they won't have gone to waste.

 

[Mike P.]

Re: Need advice on how to use speakers I have laying around.

They should be able to handle double that Xmax before any chance of damage.

 

[evilskillit]

Re: New Devlopment

Ah so speakers just get distorted when exceeding their x-max by a little bit?

 

[thxgoon]

Re: Need advice on how to use speakers I have laying around.

Yes, xmax is a measurement of cone excursion while the coil is still in the gap. Sometimes manufacturers will state an 'xmech' which is the maximum total excursion of the driver.