Porting Altec Santiago's (878B)

[Don McRitchie]

The Santiago has roughly the same interior volume as the L300 and may even be a bit larger. As a former Santiago owner, I think I know what wlk is getting at. The 411 bass driver always struck me as underdamped with a somewhat bloated character. It definitely played lower than the similar 416 based Valencia. However, in my opinion it did not have anywhere near the same level of bass articulation and definition.

I have been told that porting the 411 does not work well due to the underdamped suspension, but I am not aware of anyone that tried it. Replacing the 411 with a 2235 would be an interesting experiment. They are very close in sensitivity such that the 801 cross-over could likely still be used. You would have to calculate the exact interior volume (making sure you subtract the fairly substantial horn/driver volume) and then design an appropriate tuning and port design. I would port it out the back just in case you decided you wanted to resell the system at some point with the original components. It would be cosmetically easier to fix in the back.

[edgewound]

I'm not familiar with the Santiago and how much damping material is in the enclosure...but maybe try this. Before porting the cabinet and changing the driver, add more stuffing to the cabinet to dampen the woofer suspension. A sealed enclosure usually calls for a driver with a Qts of greater than .5, so altering the acoustic compliance of the air spring in the enclosure might yield satisfactory results for you. It's probably worth a try....fiberglass or dacron batting is cheap and you won't alter the cosmetics of the box. Don't be afraid to stuff it full....you can always take it out. Two things you'll notice when you try it. The woofer will seem less compliant...or tighter if you will....and the virtual volume of the box will increase up to 20% resulting in lower bass extension. Of course....you might not like it....lol.

You might also want to try a different amp...one that has a damping factor of greater than 500 with lots of power reserve...it's quite ear opening...that is if you haven't already tried that.

Thanks,

Edgewound

[Lancer]

I'm not going to quote anyone. Instead I'm going to be REALLY lazy and let Wayne explain his perspective with respect to damping

http://www.audioroundtable.com/PiSpe...ages/2062.html










BTW we need to get some better parameters on some of these drivers...

[wlk]

Thanks to everybody for all the excellent information and suggestions.

Please keep the information and suggestions coming.

My desire to improve the bass output and speed of the Altecs is based upon comparissons with several pairs of JBL's that I own including L220s, L100Ts and L112s. The comparrison may be a bit unfair but the Altecs have a magical midrange and I would like to improve them.

Last night after my post I thought I would take a closer look at the Altecs and see if I could spot any potential areas to upgrade in order to improve the bass. These were some of the things that I noticed:

The two inductors in the Xover are ferrite core and use small wire.
All capacitors are original and in questionable condition.
The internal wiring is original and small gauge.
The seal around the LF driver is questionable.
There is no seal around the HF horn.
All drivers look great.
LF drivers have been refoamed - job is excellent

Another thing that I notice was when I played the Altecs with the Xover connected but unscrewed from the cabinet (sitting on top the cabinet) the bass became extremely unfocused and flabby. Granted the opening for the Xover is not a tuned port but it may give some indication of how the LF driver would sound in a ported cabinet. Maybe the 411-8A cannot be used in a ported cabinet.

To answer the question regarding the amp that I am using, it is a JBL MPX 300 (made by QSC) which is rated at 200 watts at 8 ohms with a damping factor of greater than 200.

Thanks
WLK

[clmrt]

I had 847A's, and sealed the horn opening with plumber's putty and ensured the rest of the cabinet was air-tight. Port was a factory 2x3x.75" hole in the baffle. Based on WinISD, it's tuned to about 40Hz.


They were always a bit thin on bass for me, but fiddling with polarity actually made it better when "wrong". I verified it twice. Maybe they were wired in reverse at the factory?

The new owner hooked them into Mac gear with a 5-band rotary EQ equipped pre. He was heavy handed until he got it trimmed up and they rocked with nice thick bass, very quick and clean. So maybe you just need to use the tone controls?

[Don McRitchie]

Regarding amplifier damping factor, you may want to read the following:

http://www.lansingheritage.org/html/...ing-factor.htm

According to this, your amp's rated damping factor should not be an issue.

As further background on the 411, Altec's literature of the time states that it was only intended for sealed enclosures. Altec never developed a ported design for the 411 in either their.finished systems or enclosure plans and specifcally recommended against that approach.

[Lancer]

Maybe the 411-8A cannot be used in a ported cabinet.

As further background on the 411, Altec's literature of the time states that it was only intended for sealed enclosures. Altec never used it in a ported enclosure.

Doesn't anyone have a pair they can get the TS parameters ran on?

Or do we care?

[Don McRitchie]

T/S parameters do exist here:

http://alteclansingunofficial.nlenet...ele-Small.html

I might as well lay all of the cards on the table. From the information given to me by a senior Altec manager of the era, the 411-8A is a flawed design that cannot be fixed by enclosure tuning. It was designed by a loudspeaker novice whose prior work at Altec was designing microphones.

The most significant issue is how the driver employs a ferrite motor. A loudspeaker that uses a ferrite motor in the exact same topology as an Alnico motor will have very audible levels of distortion in comparison to the original Alnico. It is due to ferrite magnets' much greater susceptibility to flux modulation which results in 2nd order harmonic distortion. This distortion is one of the major culprits in robbing the 411 of bass detail. These motors are also much more susceptible to power compression since ferrite magnets temporarily lose energy at a greater rate than Alnico with rising temperature. At higher temperatures, the response becomes quite non linear with even further levels of distortion

These distortion products can be engineered out and are by most modern quality manufacturers with the use of shorting rings in the magnetic circuit, motor venting, and technologies such as JBL's SFG. However, the Altec 411 was one of the first large magnet ferrite drivers, and like the saying goes "you can tell the pioneers by the arrows sticking out of their backs."

When Altec developed this driver in the late 60's the issues with ferrite magnets were unknown and thus there was no effort made to compensate for the deficiencies. It is one of the reasons that the driver was not long lived, disappearing from Altec's catalog by the late 70's.

Don

[edgewound]

Regarding amplifier damping factor, you may want to read the following:

http://www.lansingheritage.org/html/...ing-factor.htm

According to this, your amp's rated damping factor should not be an issue.

As further background on the 411, Altec's literature of the time states that it was only intended for sealed enclosures. Altec never developed a ported design for the 411 in either their.finished systems or enclosure plans and specifcally recommended against that approach.

This might belong in another thread, but here is a good link to discuss damping factor...and it's now a Harman Co.

http://www.crownaudio.com/pdf/amps/damping_factor.pdf

Thanks for you indulgence...
Edgewound

[wlk]

Once again thanks to everyone for the excellent information. Keep it coming.

Extremely interesting information on the 411-8A.

I have a few questions based upon the information provided:

1. What is the polarity of the terminals on the 806-8B HF drivers? Mine have no markings of any kind (including numbers) around the terminals.

2. What is the correct wiring hookup for the 806-8B? Someone may have been playing with the wiring in the last thirty years.

3. Can the 411-8A be improved? For example, mass rings, dopping surround, etc.

4. Can we further explore the possibility of using a JBL 15" LF driver and porting the Altec cabinet? Any suggestions for the model of JBL driver, the port size and the port location.

Regards
WLK