1003b versus 311-90...?

[sunnysal]

311-90s are SO darn expensive now, I have seen 1003Bs selling for less...my question is; are they fairly equivalent? what would be the stregths and weaknesses of each? can the 1003b be crossed over as low as the 311? drviers? 290? 291? thanks, tony

[GM]

311-90 is 90 x 40, 1003/90 x 35. Both use 300Hz/2nd order XOs. Unless tar filled, I imagine the 311 will be better damped and the 1003 will have a better off axis HF power response, but will be less clear on-axis in the HF for the same reason. Factor in that the multi-cells have a longer throw and the 311 is my preference of the two for a HI-FI app in a typical size room.

299A, otherwise 288H.

GM

[sunnysal]

Thanks, though I would have thought if I wanted to go down to 300hz I would have to go with 290 drivers...no? tony

[GM]

Since this isn't a prosound forum I make the assumption that it's a Hi-Fi app unless stated otherwise, so I see no reason to use lower SQ drivers. Regardless, both are rated for 300Hz in a prosound app, just at a lower power, and the main difference between models is the diaphragm, just like the 802 Vs 808, etc..

GM

[djnagle]

Hi GM, I have 288C with 1505. How does the 288C stack up with the other drivers for these horns. I am also using a Beyma super tweet crossed at 5000hz. Thanks.

[GM]

Greets!

Hmm, didn't I respond to this on the HE forum recently? Anyway, it's a cheaper made version of the 'B' with no Faraday ring so needs more HF EQ, though using a supertweeter as you've done is the best option for a Hi-Fi app, with either 14kHz/1st or 7kHz/2nd being the preferred points IIRC.

I haven't messed with these older large format drivers since the early '70s so my memory's really dim now, but now that I think about it, all the later models must be updates to the 'C' model since the later ones I've used don't have Faraday rings either, relying instead primarily on VC materials refinements and closing/maintaining tight gap tolerances through improved manufacturing techniques to increase performance. And of course switching to a radial phase plug.

So, what tweeter XO point/slope is working for you?

GM

[GM]

Oops! That should be ".....what slope....."? I'm so used to writing the two together, it's habit.
GM

[djnagle]

Hi GM, as I was writting that note, I got a sense of dajavu so you probably did answer it in the HE forum, sorry about that. I am running the Beyma CP25 crossed at 5000 through the Rane AC23. Cheers and thanks.

[sunnysal]

Thanks for the driver information, I was simply going by the altec specs listings, the only driver I could find spec'd down to 300hz was the 290, the 299 and 288 said "smooth repsonse down to 500hz"...regards, tony

[GM]

Understood. With the advent of the high amp power 'race' in recent decades, the manufacturers have had to assume a 'worst case' power rating for warranty considerations. For a Hi-Fi app though, it's mostly academic.

Indeed, when using a typical SS amp, you really need to use some form of series resistance to load the amp enough to bring it up to its linear/low distortion BW, otherwise it's just idling along most of the time when hooked up to a really sensitive system.

GM