802 vs 902: sensitivity

[aeyb701]

Hi again all:
I have both the 802-8T (made into a "G" by removing the loading cap) and 902-8A's. When I compare them the 902 is a much better match loudness or sensitivity-wise than the 802, in combination with Altec 416's or 515's.
The data sheets bear this out too-citing a 111 or so dB efficiency for the 802 and 106 or so for the 902.
I recall the 515-8g is 101 dB and the 416-8B is 98 dB, or so.
I want to know how the Model 19 sounds as good as it does with a 416 and 802-8g. Does the M19 Xover compensate and "pad down" the 802?
If that were so then did Altec have to alter the Xover when they changed from the 802 to 902 driver, in order to keep the same overall sound?
I'm really curious as that 802 is one overpowering driver.
Thanks,
Jon Archibald

[gamalot]

Wish I had the knowledge to provide a good answer here.

One thing I do pick up on, if you are asking when Altec changed over the Model 19 from the 802 HF driver to the 902 HF driver, they also changed the LF driver from 416-8B to the 416-8C.

From what I have read here and at the LH site there appears to be quite a difference all the way around from the original 19s to the last versions produced.

I am sure there is compensation in the model 19/1201 XO in the form of a zobel filter that others here can explain much better then me.

Does the 802-T driver have a tangerine Phase plug and alnico magnet structure so it can truely be made into an 802-8G?

Gary

[bfish]

Originally posted by aeyb701:
Does the M19 Xover compensate and "pad down" the 802?...

<font size="2" face="Verdana, Helvetica, sans-serif">Hi Jon,

Yes, as do most Altec 2-ways employing a compression driver/horn over a single reflex-loaded direct radiator.

As to spec'd ratings, you have to compare apples to apples. On a 811 horn, the 902 is listed at 104dB, 1W/4ft, as is the 802. The only rating I could find for an 802 at 111dB was on a "30 inch trumpet", which obviously provided more gain than the much smaller 811. Apples to apples sensitivity ratings for several 800 series units can be found in TL220.

I can't say conclusively that the M19 XO wasn't modified for the ferrite drivers, as I've never been into one, but given the widely adjustable MF/HF attenuation range (~14dB), it's unlikely.

If you have some 800s/900s with a signifigant difference in sensitivity when identically configured, loaded and tested, something's wrong.

[whitebroncoii]

I agree with bfish, there should be very lttle difference in sensitivity between an 802 and a 902 driver when tested on the same horn.

[aeyb701]

Thanks Gary, bfish, and Gamalot.
I got the 111dB figure rightly or wrongly from the data sheet on this site for the 802D driver-which although it lacks the tangerine phase plug is the same alnico magnet, but correct me if I'm wrong.
Gamalot-yes it's both Alnico and has the tangerine (the 802-8T).
My next job will be to sub out the 902 and try the 802 with the N1201-8A/511B/828/416-8B.
I'm using a C-J PV-7 and rebuilt Dynakit ST-70 as electronics. I'll let you all know if it's much different-sounding.
Jon

[bfish]

Yeah Jon, that's the same sheet I mentioned, which, in the footnote mentions the test was on the 30" trumpet. The D sensitivity should be ~the same as the Gs, so it's good data, but only if considered in context. While they didn't detail the horn used, a "trumpet" insinuates a true exponential curve (max gain), and a 30" version would certainly add several dB gain in its' BW.

What interests me is what 30" trumpet they really used...a single section of a 203? an old Racon etc horn?

Sounds like a fun project. Your 416/828 will further be a closer sensitivity match to the HF than the papers would indicate, from the 828 horn's gain. You'll only need a few dB pad.

[ZilchLab]

Linked here by others previously, here's what the Model 19 crossover does, and how:

N1201-8A EXPOSED