Davids for Tom

[Oscillate]

Well done sir

[Grant Bunter]

Thanks for a very informative, detailed thread.

It's been great watching progress (we all have hiccups of some description it seems, just part of the process?) and learning some new techniques along the way.
Especially the finishing.

What a great result for you and your boy!
I'm sure he's loving them

[Tom Smit]

Good job! Thanks for sharing in the venture.
(Waiting for the rest of the review.)

[subharmonic]

Can we get a moms reaction video?

[publicIdaho]

We have been listening to the new speakers quite a bit the last couple days and they sound great. They are more efficient than my big old speakers, but it is really hard to tell much difference between the two. Maybe the Davids are a tad bit brighter on top and the very bottom seems to have more punch, but it is hard to say how much that is due to the slight volume jump when switching between the speakers. They really are very similar. That is good because once I made the old speakers 20 years ago, I have never been very tempted to try to improve upon them, never heard anything I liked better.

The speaker location is not optimal for super critical listening, but provides dramatic sound for our epic ping pong battles. Tom hit a smash way high, it hit the 45° angle front just right to ricochet off and smack his other speaker as well. Then he cries, "Dad, why didn't you sacrifice your body for the speakers!!!"

Today, in an effort to get the lazy bones out of bed (and to try out the new SPL meter that came in the mail) I cranked up the volume knob up almost 3/4 of the way up on some rock and roll and hit a little over 105db at the back end of the ping pong table. I turn it down and start listening to my old Stereophile test CD and notice a strange sound coming out of the right speaker. Get close and the top mid driver is not right. Take it out because I was a bit concerned about a loose wire, but the connections are good. Then push in the cone; it does not want to move. Push in the lower mid cone and it moves freely.

So I have to explain to Tom that I blew up his speakers when he gets out of the shower. We listen a little closer and it sounds like the top mid driver in the left speaker is also wrecked. I also switched to the old speakers and cranked up the volume knob to where it was when I blew the new speakers and everything sounded fine.

So what is the expert opinion out there - did dear old dad get to be the guinea pig on seeing what the speakers could take? I imagine it was the amp giving up - it is an old 90 watt Denon amp and might have been to the point where it was starting to clip. I actually walked around the house when I had it cranked up to see how loud it was upstairs. I don't have much experience cranking up this amp, I found a good deal on some Carver separates shortly after building my first set of speakers 20 years ago and I need hearing protection to get the volume knob past half way on that set up.

More excitement on the new speaker front...

[mr.lussier]

I find it very surprising that a driver blew both sides at the same time, while cranking the volume for only a brief period. Moreover, out of 4 drivers per box, it's the exact same one thats problematic. I'd suspect a wiring problem. Also, did you verify every driver's polarity with a 9-volt battery before installing them ? Sometimes you get a driver with reverse polarity right out the box. A driver out of phase can cause major cancellations that can lead you to crank up the volume way more than necessary. Don't ask me how I know this lol....

[Bill Fitzmaurice]

I find it very surprising that a driver blew both sides at the same time,

I agree, I've never been shy with the volume with mine, and the midbasses are $14.95 20 watt Pioneers (no longer in production).

[publicIdaho]

I find it very surprising that a driver blew both sides at the same time, while cranking the volume for only a brief period. Moreover, out of 4 drivers per box, it's the exact same one thats problematic. I'd suspect a wiring problem. Also, did you verify every driver's polarity with a 9-volt battery before installing them ? Sometimes you get a driver with reverse polarity right out the box. A driver out of phase can cause major cancellations that can lead you to crank up the volume way more than necessary. Don't ask me how I know this lol....

I did not consider that there might be a problem with the polarity of the drivers - they have different size spades for the positive and negative connections and I made sure to put appropriate spade connectors for the plus and minus.

I contacted GR Research and they said that those drivers have not had a problem with high power amps with plenty of head room, but when connected to cheaper equipment and the amp begins to clip... They also said that 90% of blown drivers have been connected to Denon amps.

I will have to check the polarity of the drivers I guess, never thought there would be a problem if they were so clearly marked.

[mr.lussier]

After building a DIY speaker kit some time ago, I was testing the speakers and I quickly found out that the two didn't sound exactly the same, but I had a hard time describing the difference. While doing some A-B listening, I came to realize that the bass response was better with one speaker than with 2. After a little research on the net, I uninstalled the drivers and checked the polarity using a 9-volt battery. I directly touched the positive lead of the battery to the positive lead of the driver, same for the negative. One speaker cone moved out, the other sucked in. I was amazed to say the least... Don't know how this can happen and don't know if this is a common occurrence or not. I don't know if this is the solution to your problem but you can bet I will check this beforehand on every future projects. On that exact same project, I had a tweeter that wasn't working. After a little troubleshooting via a 3'' 1/2 hole in the baffle, I managed to reheat a solder joint that looked perfectly fine and then the tweeter started to work. That was with the one crossover that I didn't test before installing it

Quite funny that 90% of blown gr-research drivers occur with denon amplifiers... How different are they from other amplifiers ? Don't own them but aren't they decent stuff ?

[Bill Fitzmaurice]

I contacted GR Research and they said that those drivers have not had a problem with high power amps with plenty of head room, but when connected to cheaper equipment and the amp begins to clip... They also said that 90% of blown drivers have been connected to Denon amps.

I'd blame the amp too, as those drivers are made to run to a full octave lower than what they're crossed over at in the David.

[publicIdaho]

New drivers on order. Getting them delivered to California. Now we have to get the speakers down there - fun little thousand mile ride.

Well, hopefully my son might save his hearing by worrying about blowing his speakers. Of course these speakers are so efficient, he will be wrecking his hearing with the volume knob at 1/4.

Just wrapped the speakers up for the trip and I am very satisfied with the finish we eventually got on them. They look so nice.

[AntonZ]

Drive carefully. What a waste it would be to damage these beauties on the trip