Replacing a manufacturer's driver

[goodsound]

Ok, so I'm intrigued by the idea of making my own sub, but I'm not sure my current tool set-up is sufficient to accomplish the finished product I'd like to produce. Also, I need more cabinetry practice; much more.

However, I do have an old Definitive sub cabinet, which coincidently has a broke driver. Would it be feasible to replace the old driver with an after-market version, i.e. a driver supplied from somewhere other than the original sub manufacturer? And if so, what factors would be important in determining which driver would be the best fit? If not, could you provide some insight as to why my "Frankenstein" sub isn't necessarily advisable?

Thx all!

[mayhem13]

You will need to calculate the internal volume of your existing deftech sub.Is it ported or sealed?
What is the existing driver size and amplifier power available. Once these parameters are known, you can use any freeware subwoofer design program and plug in the theille/small parameters into the program to determine performance based on your enclosure. Or you can post the enclosure paramaters and for help on the forum. To answer your question, yes it can be done and sometimes actually improve the originals performance with a 'better?' driver or speaker. To calcualte the internal volume you will need to know it's inside dimensions minus any bracing/ports/etc. This should be done with the driver removed. Another way would be to fill the cabinet with a non-compressing dry fill and remove and measure what ever you filled it with in say a known measuring container preferably liters. I don't suggest using a liguid although it seems easier for it may contaminate or damage the cabinet. If you do this, you will have to remove any insulation/stuffing as well. Hope this helps

[Mike P.]

It would help if you posted the model number of the sub, especially if it's a powered sub. The amp would have been designed to work with the specific driver, and may not be the best choice for powering a different driver.

[goodsound]

The model in question is a PowerField 1500. It includes a 250W amplifier and the original driver is rated at 4ohms. I was told by a DF representative there are three models of this particular set, mine is distinguished by having two line-level inputs (or at least that was the information I was requested to provide them in identifying the exact model). It is a sealed enclosure.

I'm going to have a little difficulty calculating the volume as the amplifier is sealed off from the driver space. I requested the specifics (volume and measured dimentions), but the DF representative said the information was still considered proprietary (even though they've already provided me with the amplifier's schematic plan ). Also, I'm concerned about how a different driver would attach (i.e. same screw points or other). And I'm not positive, but the current driver may attach to metal binders set in the MDF. It seems likely any after market item will not fit nearly as well.

[ccdoggy]

Well first step is to get the dimensions of the box. just measure it up and see what it comes out to. Then measure the amp section from inside the box and then remove that cu.ft. from the total of the box.

Mounting wise you may hit a few bumps as the holes might not line up. not a big issue, just drill out the new holes and get some T nuts and pound them into the holes (from the inside of the box) and get some bolts to screw the sub into the T-nuts. sounds more complicated then it is.

I would do it if i had a broken sub laying around. you dont need a heavy duty sub at all for those 250 watts so you may be able to get out with a cheaper driver.

I am assuming the 1500 means 15" correct?

[goodsound]

Yup, its a 15" driver. I got a quote of $120 from DF for a new driver as a replacement. After looking around, that looks about mid price for a 15" driver. How do you think the OEM parts compare to stuff I can get from say "parts express" (or elsewhere)?

Good idea on the t-nuts, I hadn't thought of them.

[Warmon]

If the box is unlined on the interior, you can use "play sand" to fill it with, then scoop it out with a cup of known volume. Another consideration:, not all cut out hole sizes are gonna be the same from one driver to the next - not a huge problem if the new driver is bigger, but what are you gonna do if it's smaller? Cheap option; get a replacement DF. Next best option; get a new driver, build a new box and reuse the amp. Are you sure it's the driver and not the amp that's broke?

[goodsound]

Ouch, hadn't thought of that either!

And Yes, I'm sure its the driver in this case. Their price quote even includes tax and shipping. Pretty tempting...

[ccdoggy]

Personally i would just go with their driver. thats a pretty good price, and you know you are getting exactly the driver that works in there. you could get another driver but you would have to spend quite a bit of time playing with models and graphs to figure out which driver you wanted. then that driver may be more expencive and want more then 250 watts.

If you liked it the way it was before the driver died then i would jsut get a new replacement driver.

[goodsound]

Yes, I think thats what I'm going to end up doing. Mostly, I don't have much of a budget to throw at upgrading the unit right now. I'd much rather spend a bit now so I have the sub working and save money for a new sub, possibly even building my own.

The PF1500 is decent, but I've seen some other products on the market I think would put it to shame. That, and with the flourishing market for DIY subs, I think I can do better with a reasonable budget. I've read some of the IB post, but I think thats a bit outside my league now.