making cabinets match hornresp

[owen]

I filled it with open cell high density foam

There's your answer. The foam makes the chamber appear larger, not smaller!




Have fun


Owen

[jbell]

Originally posted by owen


There's your answer. The foam makes the chamber appear larger, not smaller!




Have fun


Owen

owen:
actually I think the chamber is smaller, not larger. The foam I'm referring to, is the kind of foam that makes your formed packing around electronics. It's a very dense open cell, but I don't think it has any properties other than taking up space... at least in terms of the chamber. I used it because it was light, and because I was hoping it wouldn't cause 'bounce back' issues with standing waves between the driver and the chamber wall. With speaker breakin, fixing leaks, and measuring at 28v, not 2.8v, I now get pretty close to hornresp predictions -- so I'm happier. I think break-in made the most difference... (again, with the mcm spider.... I think I forgot first test, that I hadn't broke those drivers in.)


Oliver, yes 8:1 seems to work well on the MCM. Any tough cone 8" driver (like the TB) would probably work similarly. However I wouldn't go 8:1 on a 10" or 12" driver, and I'm pretty sure that I want to be on the safe side of 3:1 or max 4:1 on a 15" driver..

With the specs of the MCM, I just can't seem to get anything respectable in terms of flat response, until 8:1.

So, you think I should be happy with 120-122 outdoors at 28v for a pair of 8" drivers? There isn't any more I can wring out of them?

[littlemike]

Wow - look away for a few days and look at all the action....

I can't get much more out of them either. I get similar response with a 5:1 ratio, so you may not need to go all the way to 8:1. My hornresp stuff is not on this PC or on my thumbdrive today, so I can not check the actual sims right now.

If you look at Oliver's proposed fold for the throat area earlier in this thread (sort of turn my last TH fold inside out - split the horn with the throat) you can mount the drivers face to face for a smaller throat chamber.

If you wanted to run 4 drivers per cabinet - you could make a common throat and split back chambers in the base of the horn and do the same style of fold. Cabinet width would be similar, but you'd need a little more depth to fit the drivers, then adjust the height to get the length and volume you want.

[GM]

Originally posted by jbell
The coil lives, but the spider -- not so lucky.

I know I'll get flak for saying 8:1, but hey, I've built them, and they live. Kinda hard to argue with that.

Also, when doing 'PA on the cheap' it's not unheard of be lacking in the dsp department, and 40hz HP may be unavailable.

Ah! So the spider actually tears? Never seen that without the VC being spit out through the dust cap.

Nope, I experimented with up to 10:1 on a BLH and if you can get the horn to be acoustically damped enough, then it boils down to whether the motor's strong enough to tear the diaphragm.

GM