Is this a good deal?

zingo

I've decided that it is a good deal. Edit: Saturday 14:51.

It seems like a good way to get a almost completed DIY subwoofer project.

http://seattle.craigslist.org/est/ele/527671782.html

zingo

He says they don't come with x-overs and the drivers are in good condition. It sounds like the drivers were back-stock from when NHT discontinued the 3.3 and they were just mounted in some custom boxes. Could be a nice pair of stereo subs. Any thoughts?

Systems

Those drivers were highly regarded and that seems a very reasonable price for the pair and enclosures.

zingo

I think I might go for it if it works out. Finishing the boxes could be fun!

What would be the best way to put a crossover on these things? A passive or active coupled to the amp?

Systems

zingo wrote: »

What would be the best way to put a crossover on these things? A passive or active coupled to the amp?

Active is definately the way to go as it will allow for easy changing of the crossover frequency.The least expensive route would be a plate amp (or 2 if you want to run them stereo) with integral xover,Parts Express has some good choices or get a Behringer CX2310 and an inexpensive Pro amp.

zingo

I am looking at a few passives on PE because I already have some amps that would work, and that would be the cheapest way to do it. If it sould bad, than the worst I am out is $30. I also found these RCA level low pass filters. Is it to good to be true?

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-256

zingo

Well I went and picked up the subs, and it is the deal of the year! He gave them to me for $100 and initial impression are great. I will post pictures later tonight, and I haven't heard them yet, but here is my first look:
A pair of 12" drivers that were originally made for the NHT 3.3. They are each in a DIY, sealed box made of 1" MDF, internally braced, and acusta-stuffed. They also have 5-way binding posts, but no internal crossovers. (Will be fixed shortly) They are finished with a black acoustic cloth over the whole thing, classic Vandersteen style. The tops are unfinished, but I think I might use a stained, solid wood cap SDA style and see how that turns out. I'll post more tonight when I get the chance.

Systems

zingo wrote: »

I am looking at a few passives on PE because I already have some amps that would work, and that would be the cheapest way to do it. If it sould bad, than the worst I am out is $30. I also found these RCA level low pass filters. Is it to good to be true?

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-256

Are other xover frequencies available?150hz would be much to high unless you have tiny bookshelf speakers.Ideally you want the low pass filter on the sub to start rolling off at approximately the same point where the bass
response of the main speakers begin to naturally rolloff. (ofcoarse this is assuming no hi pass filter is being used).Otherwise you will have considerable overlap with both the mains and subs reproducing the same range.This will adversly affect the mid and upper bass.

BTW,Nice score on the woofers and cabinets.The NHT 3.3 garnered lots of praise for its excellent bass response.If I remember correctly the best results from that woofer were obtained when used in a sealed enclosure of about 2-3 cubic feet.

zingo

These subs are better than I could have imagined, and sadly, I can't find my camera... Pictures still to come. The cabs are heavy, and rightly so. The 1" mdf cabs that measure 27h x 22w x 11.5d, are internally braced on all four sides by circular cut-outs. All edges were caulked, the walls of the cab were then covered in 1" foam, then the entire enclosure stuffed with fiberglass fill. The black cloth covers go on easily and look really good. Once I can fab up two top pieces, they are going to look pro.
I measured the impedance at the driver at got 3.7 ohms, then measured the impedance at the binding posts and it was 4.4. Baffeled, I started digging around in the stuffing, and found a crossover! After hooking the sub up to a tiny 75w Denon receiver, I tried it out. The crossover works well, but I am not sure where it is crossed at. It's probably around 150hz, but I can try to check that later if I drag my adjustable sub out of storage. Well the sub sounds great! (Even with the low power) The sound is crisp and clear, and I even got it to go down to 22hz. Once I can find a powerful amp, and run both of them in stereo, look out...

Systems

zingo wrote: »

The crossover works well, but I am not sure where it is crossed at.

It may be a 6db per octave xover with just an inductor in series with the woofer,or a 12db with an inductor and a capacitor.Either way you can estimate the xover frequency if you know the values of the components.The inductor may have a sticker that indictes its value and the cap will have the value printed on it.

zingo

I saw a cap and an inductor in there, but I will check to see what all is in there and look for values when I get the chance. Thanks for all the help with with this stuff. It's my first DIY subwoofer, well kind of mine I guess.

zingo

So help me out GV#27, I took a look at the x-over again. There are three componets; a inductor labeled 7.00MH, and cap labeled 200 MFD 100V, and another smaller cap that is about an inch long, black with white ends, and unlabeled. It was wired in parallel with the other cap. Any idea of the x-over point? I was also impressed because the while thing is wire with 12g wire, so it is nice and meaty for a subwoofer.
Also, I finally weighed the whole enclosure, and it weights a nice 53lbs. Sorry, I still can't find my camera, but I'll keep looking.

zingo

Using this website The 12 Volt I think I calulated that the x-over is a 12db per octive at about 140Hz, and the two caps are being used to get a final value of about 186 ufd. What do you think?

Systems

zingo wrote: »

Using this website The 12 Volt I think I calulated that the x-over is a 12db per octive at about 140Hz, and the two caps are being used to get a final value of about 186 ufd. What do you think?

Yep I think you would be correct.;)Except the capacitance is the sum of the two parralleled so if one is 200uf you will have more than 186uf.

Systems

What are you using for mains?That xover point is on the high side so may want to experiment with some hi pass filtering on the mains.This is so that both the sub and mains don't have a large overlap in the frequency range they are both operational.You could simply add a capacitor of appropriate value in series with the mains to rolloff their bass output.

zingo

Thanks for the correction. I need to work on my EE side. Right now, the sub is hooked up with my B&W 602S3 which really makes them sing. The high x-over takes off a bit of their metal dome tweeter edge and warms them up. However, I plan on using the pair of subs with my SDA 2A. What do you think?

Systems

zingo wrote: »

I plan on using the pair of subs with my SDA 2A. What do you think?

Sorry my bad Im on the Polk site but I have NO expierience with SDA's.:eek:But as I mentioned previous IMO I think running the mains (SDA's or others) and subs so that they overlap over such a large frequency range is sonically not a good idea.

zingo

Ya. I''l just have to try it, and then make arrangements from there. If I wanted to lower the x-over, would I just add another cap in parallel, or would have have to redo the entire thing?

Systems

zingo wrote: »

If I wanted to lower the x-over, would I just add another cap in parallel, or would have have to redo the entire thing?

The coil and cap would both have to be larger values.The coils would be large and therefore very expensive.The best solution would be to not use the passive xover and add an active low pass filter before the sub amp.This unit would likely do the trick nicely and it is inexpensive and versatile. http://www.creativesound.ca/details.php?model=F-1http://www.reckhorn.com/index.php?ln=en&prod=f1

zingo

Well, one I already bought them and I'll be finishing them today. And two, why would I buy a Polk sub over these? Riddle me that...

zingo

Oh, sweet GV#27! That is cheap. Let me take a look at that and I'll get back to you. I'm still waiting to see why Polk subs are better. (But I don't think I'll get a response)

zingo

What about the Reckhorn B1? It seems to be just a subwoofer controller without the hi-pass outputs.

http://www.reckhorn.com/index.php?ln=en&prod=b1

Systems

zingo wrote: »

I'm still waiting to see why Polk subs are better. (But I don't think I'll get a response)

Let me see,you have 2 very good 12" drivers,a pair of seriously well built enclosures and paid next to nothing for them....Yep he is right get rid of this stuff,and I being in a helpful mood will gladly relieve you of these nuisance subs so you will have room for your new Polk.;)

SLOCOOKN

zingo wrote: »

Thanks for the correction. I need to work on my EE side. Right now, the sub is hooked up with my B&W 602S3 which really makes them sing. The high x-over takes off a bit of their metal dome tweeter edge and warms them up. However, I plan on using the pair of subs with my SDA 2A. What do you think?

I have a set of 3.1's cut off at 80 hertz by my pre. I use a VMPS sub powered by a Carver tfm55x with pleasing results.

Systems

zingo wrote: »

What about the Reckhorn B1? It seems to be just a subwoofer controller without the hi-pass outputs.

http://www.reckhorn.com/index.php?ln=en&prod=b1

Yes this would work as well and it also will alow you to add a bit of boost to extend the bass response not that you will need it.50hz appears to be the lowest point for the lowpass setting and they don't state the rolloff rate but it is likely 12db or 24 db.A nice versatile unit considering the price.

zingo

I'll think about that deal GV. As long as you pay shipping on the 110lbs worth of woofer.

Thanks for the notes SLOCOOKN. I'll have to play around with the x-overs, but 80Hz is a good place to start. I'm excited to get all of this finished. I won't have the room to set it up until I move, but the rig will end up being:

modded Polk SDA 2A (until I get the chance to get a big-boy pair of SDAs)
Stereo, custom subwoofers with NHT 3.3 woofers
Soundstage tube preamp
custom Carver 600x2 for the Polks
Audiometric 225x2 for the subs
Reckhorn B-1
iPod HiFi dock with lossless albums

What can I say, I'm excited.

PS. I should be finishing the subs tonight, so I'll look for my camera again and see if I can finally get some pics on here.

dorokusai

That's a terrible deal.

Systems

zingo wrote: »

I'll think about that deal GV. As long as you pay shipping on the 110lbs worth of woofer.

To save on shipping I was thinking about driving out and picking them up.If I leave tonight I should be there around about Sunday so please have them finished.:D


Oh this maybe of interest to you.Madisound sold those woofers for $150 a piece. http://www.madisound.com/catalog/product_info.php?products_id=1402

zingo

Thanks for that. Those look like they are just about the same woofer. I haven't seen a facts sheet on them yet, but that seems about right from the electrical measurements I made, and it's nice to see some of that other info. You have been a huge help on this project oh DIY woofer guru.

zingo

Well, here they are. Finished and all. They are set-up in the pictures with my B&Ws and a small Denon receiver for demo. (Read previous for final set-up) The combo sounds pretty good because of the bottom end roll off of the bookshelves. Running all four speakers off the Denon was not an ideal situation. Not only are the subs less efficient than the B&Ws, so they are quieter. They really need that Reckhorn B-1 so optimize them; bring up the volume, set the x-over, boost certain frequencies.

nms

yeah, I'll bet you're straining that little receiver a bit!