Altec Model 19 - New Owner, need some experienced advice, thanks!

[SansuiFlorida]

I just acquired a nice set of the Altec Model 19s. I'm the third owner of this set but for some unknown reason the first owner sealed the port with a block of wood on the inside. The wood appears to be glued to the inside back wall. I'll have to pull the 416 B and take a closer look before I attempt to knock out the block of wood which is painted flat black. Sounds fine (I haven't run any high volume yet) but just wondering if anyone heard of running these with the port opening purposely sealed. Any advice from the experienced Model 19 folks would be appreciated. Thanks

[fpitas]

There's a strong contingent of "audiophiles" who are sure that vented cabinets can only give boomy, one-note bass. That's not true, of course. Then there are those that simply like the tighter bass of a sealed cabinet, and are willing to give up bass extension and live with the higher distortion.

[Fort Knox]

There's a strong contingent of "audiophiles" who are sure that vented cabinets can only give boomy, one-note bass. That's not true, of course. Then there are those that simply like the tighter bass of a sealed cabinet, and are willing to give up bass extension and live with the higher distortion.

I don't see where higher distortion fits into that

[fpitas]

I don't see where higher distortion fits into that

The same driver in a sealed cabinet will have considerably more cone movement than in a ported cabinet, especially near the port tuning frequency, where the cone motion becomes very small. That will not only increase distortion of the bass frequencies, but also will cause more phase modulation (so-called "Doppler distorton") of higher frequencies being reproduced simultaneously.

[Fort Knox]

The same driver in a sealed cabinet will have considerably more cone movement than in a ported cabinet, especially near the port tuning frequency, where the cone motion becomes very small. That will not only increase distortion of the bass frequencies, but also will cause more phase modulation (so-called "Doppler distorton") of higher frequencies being reproduced simultaneously.

When the model 19 hit the stereo shops in the mid 70's it blew everything else way
thats when I ranout and bought my first set of 811/808's from Venimann Music, Rockville, MD

[AS-21]

The same driver in a sealed cabinet will have considerably more cone movement than in a ported cabinet, especially near the port tuning frequency, where the cone motion becomes very small. That will not only increase distortion of the bass frequencies, but also will cause more phase modulation (so-called "Doppler distorton") of higher frequencies being reproduced simultaneously.

The same driver in a sealed cabinet will have more cone movement than the same in a ported cabinet?

I tread lightly here but whenever I was able to use my hand to seal a port up, woofer cone movement decreased...considerably.

[fpitas]

The same driver in a sealed cabinet will have more cone movement than the same in a ported cabinet?

I tread lightly here but whenever I was able to use my hand to seal a port up, woofer cone movement decreased...considerably.

Above the port tuning, and for the same acoustic output at a given frequency; yes. At the port tuning frequency, the woofer cone has minimum motion. Simply stopping up the port is a very uncontrolled experiment. Now, below the port tuning, the woofer in a ported cabinet becomes unloaded, and you can get a considerable amount of motion, with little net acoustic output.

This article seems valid on brief inspection:

http://en.wikipedia.org/wiki/Bass_reflex

Someone here may have a better one, but the basics are there.

[AS-21]

Above the port tuning, and for the same acoustic output at a given frequency; yes. At the port tuning frequency, the woofer cone has minimum motion. Simply stopping up the port is a very uncontrolled experiment. Now, below the port tuning, the woofer in a ported cabinet becomes unloaded, and you can get a considerable amount of motion, with little net acoustic output.

This article seems valid on brief inspection:

http://en.wikipedia.org/wiki/Bass_reflex

Someone here may have a better one, but the basics are there.

Thanks for the clarification. It just seems to defy logic, nontheless - (to my simple mind anyway LOL!).

*My "experiment" came about as a result of noticing air pulsating from the rear port of a small pair of bookshelves as a result of a warped LP. There was really no audible sound - as the frequency is well below the response limits of the speaker - but there was tremendous excursion. Sealing the port lessened woofer movement considerably.

[fpitas]

Thanks for the clarification. It just seems to defy logic, nontheless - (to my simple mind anyway LOL!).

*My "experiment" came about as a result of noticing air pulsating from the rear port of a small pair of bookshelves as a result of a warped LP. There was really no audible sound - as the frequency is well below the response limits of the speaker - but there was tremendous excursion. Sealing the port lessened woofer movement considerably.

It certainly will if the drive signal frequency is below the port tuning. Basically, below that frequency the cone becomes unloaded.