Tempest Questions

[jbandpc]

For those of you who have built a Tempest:

Did you guys coutersink the driver? If so, how much? Is the cardboard-type stuff around the edge for internal mounting only? Can I rip it off if I mount externally, so I don't have to countersink as deep?

The Technical Data sheet for the Tempest from Adireaudio.com has a section called "Applications" in which it list performance for a sealed box size of 4 cubic feet (net) with 48 ounces of polyfill. Elsewhere on their site, in the Reference Designs page, the "Mid-Q" design is 4.6 cubic feet, but calls for only 32 ounces of polyfill. Of course, after factoring in the displacement of the driver and braces, it's probably around 4 cubic feet net too.
Why does the "Technical Data" example call for 50% more polyfill than the "Reference Design" example for the same size box?

[grampi]

Getting any info about the Tempest in this forum is like pulling teeth. I've been trying to get people to give me their opinions comparing the Tempest to the Dayton DVC 15, and so far one person has given his opinion. I don't know why this forum is so dead and nobody seems interested in talking about these subs.

[grampi]

Why am I not suprised that you and I are the only two who have posted here?

[grampi]

I don't know when jbandpc and I will ever have time to read all the replies in this topic. There's just so many it's overwelming! I will have my Tempest sub project done in a coulpe weeks and will post a full review. I hope there will be room in here for my post!

[This Guy]

why you didn't try other forums. I gave you quite a few links and you didnt even try. it's not their fault that they didn't build the Tempest sub and can't give you answers. Not everyone did or is trying to do what you're trying to do. go to diysubwoofers.org they have a great forum and those guys tried pretty much every subwoofer driver out there.

[grampi]

I did try the other forums and there isn't much in there either. It seems strange that there's more info available in the car audio forums about the Tempest than there is in home audio forums.

In case anyone's reading, I started my Tempest project yesterday. I got all the peices cut, including the internal braces, and the driver cutout. I'll be finishing the legs today. The Tempest is scheduled to arrive Monday, according UPS. Then I can drill the mounting holes and install the "T" nuts. The biggest trick is going to be gluing all 4 sides together. With all the corners cut at 45 deg angles, all 4 sides will have to be put together at the same timeOnce assembled, then comes the staining, sealing, and final coat. I should have it done in a week or so. I'll stay posted, in case anyone's reading.

[grampi]

I figured as much.

[MCH]

On my octagon Tempest sub (downfiring) I used 2 3/4" pieces for my baffle. The sub is fully inset into the first baffle thickness. As for the glue up on my octagon shape I used strap clamps which worked great. I've used the strap clamps for other box assemby projects, easy to use and gives even pressure on all sides.
good luck

[karl k]

Got a camera? I for one would like to see some pics!(of the sub I mean) I like the idea of straps as posted above. Squaring clamps should also be benificial. I'm not sure why you chose miter edges unless your working with ply-veneer. Your deal I guess.

[grampi]

I will be using the the straps as well to hold the enclosure together until the glue sets. I'd take pics, but I don't have a digital cam. The reason for the mitered corners is because I'm working with veneered ply. My original plan was to finish the box with perfectly square, sharp corners. However, after cutting the pieces and handling them a few times, I've realized these sharp corners would be very vunerable to damage, as they are very fragile. One small bump by a vacuum cleaner could cause some pretty serious cosmetic damage. I have since decided to cover each corner with 1" X 3" trim pieces, not unlike the pieces you'd see on a wooden crate. I also purchased my stain and sealer today. I'm at a holding point right now waiting for my Tempest to arrive. It's scheduled for delivery on Monday. I need it to drill the mounting holes and install the "T" nuts before I start gluing things together. Just from the way things have gone so far, this thing should look and sound pretty good by the time I'm done.

[karl k]

Here's a thought for the 1X3's you are using. I kinda like what ACI did on their subwoofer. Although it's downfiring, you may take advantage of the looks anyway.

Cheers!

[grampi]

That does look nice, but did I mention that I'm a novice with woodworking? That might be a bit beyond my woodworking abilities.

[karl k]

You'd be suprised what a guy can do with a jig saw, sander, ans a skill saw! It's a matter of time and determination. You will be keeping this sub around for awhile no?

[grampi]

I finished the Tempest enclosure last night. It looks and sounds great! If anyone's intersted in the details, let me know, I'll post a more elaborate message.

[jbandpc]

Yes. Do it.

[karl k]

What... you ain't elaborated yet?

You have curiosity seekers in your midst!

[grampi]

Here goes. The project started with a 4 X 8 ft sheet of 3/4" birch ply. I was going to use oak veneered MDF, but it was almost $60 a sheet, and I got the ply for less than $30. It's a very good, void-free, 7 ply plywood that Home Depot had on sale. It also has a very nice looking grain to it. I not only wanted a nice sounding sub, but a good looking piece of furnature as well.

I chose Adire's recommended mid "Q" sealed enclosure design, which was supposed to be 4.6 c.f. I say supposed to be because when I cut all the corners at 45 degree angles, I apparently don't know how to measure correctly because I ended up with about 4.4 c.f. Good thing sealed enclosures are more forgiving than some of the other enclosure types when it comes to size.

With the exception of the lid, the entire enclosure was assembled using no nails or screws. It's held together entirely by yellow wood glue. Getting all 4 sides together at one time was a bit tricky, but with a little help, we got it together and held it in place with a strap and a tightening aparatus. It actually worked very well. The driver hole was cut out and the "T" nuts installed in the bottom piece previously. Next the internal braces were installed, then the lid was tacked on using finishing nails and yellow glue. Every joint on the inside was then sealed using caulking. The outside was sanded using 220 grit sandpaper, and the hole was cut for the plate amp.

Next it was time to make the table top and the trim pieces. The top was made from 1 X 8 birch stock. It was plained, sanded, the edges were squared and glued together using biscuits. The edges were rounded using a router. The top ended up being about 5/8" thick, and it overhangs the enclosure on all sides by about 1 1/2". The effect I was going for was to make it look somewhat like a lamp table. For the enclosure's vertical corners, I cut 3/4" square pieces, then cut a 1/2" square out of that to form perfect 90 degree, 1/4" thick "L" shaped corner pieces. The table saw really makes this an easy task. The other trim pieces were 1/4" X 3/4" that mounted horizontally just below the table top, in between the corner pieces.

On with the stain and sealer. I used Minwax #230 stain, which I think is Old American Oak. It ended up being almost the perfect match with our oak living room furnature. The sealer was a spray laquer in a satin finish. At this point I knew my wife would want to keep this thing regardless of what it sounded like. It turned out to be a damn nice looking piece of furnature! I was shocked because this was my first time ever at REAL woodworking. Of course I had a lot of help from the folks at the wood shop. Sure I've built lots of enclosures before, but they were all made out of MDF, and I never did any finish work to any of them.

Time to take it home and install the driver and amp. It didn't turn out as heavy as I expected it to be. I'd say it weighs right around 80 lbs. Keep in mind the only sub I've personally had to comapre this one to in my living room was also a DIY sub I built out of MDF. It was a 2.5 c.f. sealed enclosure using an MTX series 4000 15" car audio driver and the same PE plate amp I'm using on the Tempest. The first thing I noticed was I had to turn the amp's volume control up slightly higher (from about 1/3 to just under 1/2) than where I had it set for the MTX to obtain the same volume level. I've got to admit, there isn't a lot of difference between the Tempest and the MTX. At low to moderate volume levels, there doesn't seem to be much difference in sound at all. At high volume levels the Tempest seems to maintain its composure a bit better, and I'm not even sure the difference here is in the drivers. When I built the enclosure for the MTX, I fukced up by not adding any internal bracing. As a result, you could literally watch the sides and top of the enclosure bow out during heavy huffing and puffing. So I don't know if at high volume levels the MTX driver is actually being pushed beyond its limits, or if the flimsy enclosure is the cause of the not so perfect sound. Both seem to handle music and HT duties equally well. I was expecting the Tempest to blow the MTX away because so many people had said the Tempest is a far superior driver. Not that the Tempest isn't a stout performer, because it is, it's just that MTX must have not been as much of a slouch as many have claimed. The Tempest absolutely gives me more flexibility than the MTX though. The MTX was pretty much at its power limit with this amp, whereas the Tempest can handle a lot more power should I decide to upgrade to something like the PE 500 or 1000 watt plate amp. Would I recommend a Tempest? Yes, especially considering its $125 price. I'm tempted to say this driver/enclosure combination's performance rivals, or even exceeds that of manufactured HT subs costing well over $1000, but I've only heard them in audio shops, not in my living room. At any rate, even if the sub blows, I've still got a nice piece of furnature!

[MCH]

Congratulations on a satisfying job.
As for the bass compared to the MTX I don't know as I never heard an MTX. But I find to get a sense of a quality sub preformance, is to play good recordings with a solo stint of double upright bass. I have Patricia Barber 'Modern Cool' in SACD and the bass lines on my Tempest sound like a realistic performance. The bass is very defined and rich. Another good selection is 'Moby Dick' from Led Zepplins DVD. The drumming realism in this selection is utterly fantastic.
I love my Tempest!

[grampi]

I'm now in the process of trying to figure out if the Tempest's slight loss of compsure at higher volume levels is due to the driver bottoming out, or the amp clipping. Some have said the most likely culprit is the driver bottoming out. I was, and may still be inclined to believe the driver may require more power than the PE 250 watt amp can deliver. How can you tell what's causing the problem? I'm wondering if the Tempest would sound better using a more powerful amp, something in the 500-1000 watt range.

[karl k]

You might be right about the amp lacking in some fasion. I won't tell you it's the lack of power(although it may indeed help) as it could also be a lack of damping ability of the amp. I can't tell you what the damping factor of the amp is but I'm pretty sure it's nothing to brag about. You might consider using a pro-sound amp instead of a plate. Maybe a Crown, Carver, Mackie, Numark, ect. will have enough of a damping factor to prevent the loss of control. I've driven my plate(same as yours) pretty hard and only had probs with peaks at or above 250wts. You may also have these probs if you have bass boost dialed in on the receiver via DSP's, Bass/tone adj, Active Eq/Speaker Eq settings or the plate itself. Check with PE on the boost option for that amp and see if had it or not. Look in the ext. specs on the web for identifying resistor values for location and degree of boost if at all. I've had alot of amps clip and drivers bottom due to this.

Over all, sounds like a well planned and executed project. Ya gotta luv it when a plan comes together!

[grampi]

The PE amp I have doesn't have the bass boost. I sent PE's technical dept. an email asking them if they could tell me what the dampening factor of this amp is. Where is a good place to look online for the amps you mentioned? Which one is likely to provide the best quality bang for the buck?

[grampi]

After doing some quick searches, I'm finding these amps are quite a bit more expensive than the plate amps, but they also have much better specs. I guess you get what you pay for. The only thing I don't like about these amps is the fact they're located in the entertainment rack with the other HT equipment, which means having to run long sections of large gauge speaker wire to the sub. This wire also is very expensive. That's what's so nice about the plate amps. They're directly mounted to the sub, eliminating the need to run long, expensive amounts of speaker wire. Doesn't anybody make high quality plate amps?

[Dave Bullet]

jbandpc,

I did what MCH did for my Shiva. (I believe they both have the same "rim / flange" height). I jigsaw'ed another 3/4" MDF piece to flushmount my Shiva by laminating it to the baffle. (My baffle was already 1.5" thick and braced :-) Now it is a real dead weight :-)

I wouldn't rip off any cardboard. Besides, if you want to put a metal grille over the driver for protection (as I did), the cardboard on the driver allows you to mount the grille without rattles.

Dave.

[karl k]

Good luck with your request from PE...

I asked them about the damping factor and the slew rate and got nothing. They explained that it didn't matter and that was the end of my search for that info. For the money, my guess would be a DF of about 30 or 40 but we'll never know. The examples of amps I sited may be a little pricey but there are some others I couldn't think of their names of the top of my head. Some more moderately priced(in the $200-$300 range) are American DJ, Gemini, Pyle, and Samson. As you said, you mostly get what you pay for. As I was told by an old friend(remember Steve W) these amps are built for commercial use and will take quite alot of punishment ie. last a long time. Look for something in a DF of 100 or more and a SN ratio of 95db or better as well as mono(bridge) capability and you'll do alright. Search for Pro Sound and there's alot of retailers out there.

I agree about the convenience of plates as well as the bang for the buck, but don't believe you have to mount the "DJ amp" in the rack. Yopu can conceil it just about anywhere in the room and run your long cables as low level RCA for less cost. Besides, when you start talking about that 500wt or the 1000wt amp from PE, you're talking about the same or more money as with the others.

Just something to think about.

[grampi]

It's been my experience that amps with a DF of 200 or more sound the best. If the PE amps are only 30 or 40, that's horrible! I've heard amps that had a DF of between 100-200 that didn't sound good to me.

The Mackie 1400i looks pretty decent. There's a couple of them on ebay for a not too bad price. I'd have to run it in stereo as it makes way too much power for one Tempest in bridged mono (well in excess of 1000 watts). It puts out 250 X 2 in stereo into 8 ohms. I think its DF is over 300. I will also look at some of the others you mentioned and see what's out there.