Altec Lansing 920-8B speaker cabinet size.

[DahaiTX]

Hello everyone,

I need some help with some confirmation on a speaker cabinet size which I am going to build for the pair of 920-8B.

I did some calculation and it seems that it would be ideal to build a box that is somewhere around 3 cubic feet with a port for some extra bass. I also thought about building something similar without the port but add another 12" passive radiator instead.

From my research online, I also saw the open baffle design which is too wide of a panel, I am wondering whether it'd be just as good to build something that is in the shape of a tall rectangle without the lean.

What is your opinion? Which design do you think that would sound better?

Here is a video of the speakers in action:

Thanks,

Jimmy

 

[bowtie427ss]

It might be a good idea to first understand the design goal, capabilities, and limitations of the 920.

It was a popular, medium cost, extended range, public address/paging/distributed sound speaker. Low frequency roll-off starts around ~100hz and has pretty well fallen off a cliff by 60hz. I believe the LF section is largely based on the ER-12.

ER-12 and 920 were both made in large quantities by Altec, and Electrovoice. Electrovoice marketed them under the Bosch brand in Europe.

Large quantities of these speakers become available at low or no cost from time to time as large distributed sound systems are de-commissioned and replaced in places like schools, hospitals, factories etc..

 

[DahaiTX]

It might be a good idea to first understand the design goal, capabilities, and limitations of the 920.

It was a popular, medium cost, extended range, public address/paging/distributed sound speaker. Low frequency roll-off starts around ~100hz and has pretty well fallen off a cliff by 60hz. I believe the LF section is largely based on the ER-12.

ER-12 and 920 were both made in large quantities by Altec, and Electrovoice. Electrovoice marketed them under the Bosch brand in Europe.

Large quantities of these speakers become available at low or no cost from time to time as large distributed sound systems are de-commissioned and replaced in places like schools, hospitals, factories etc..

I am aware of what you mentioned, my design goal is to simply build something that I can get better bass performance using only these drivers themselves.

 

[EarlK]

I am aware of what you mentioned, my design goal is to simply build something that I can get better bass performance using only these drivers themselves.

The TS parameters of a driver ( woofer ) dictate how much bass will be produced when that woofer is working//aligned with a Bass Reflex box.

From your posts I'm not really sure that you understand that principle\\limitation of alignments.

IOW, It's not as simple as just increasing box size to get more bass output.

Have you modeled this woofer/box combo with something like WinISD ?

If I was going to make a shot-in-the-dark suggestion ( that has some percentage of working out ) it would be to build a pair of Back-Loaded-Horns ( BLH ) for those drivers.

With a bass horn, at least one is generally assured that going bigger gets one more bass output.

From Wilberforce's excellent thread, which is located HERE!

 

[DahaiTX]

The TS parameters of a driver ( woofer ) dictate how much bass will be produced when that woofer is working/aligned within a Bass Reflex box.

From your posts I'm not really sure that you understand that principle\\limitation.

IOW, It's not as simple as just increasing box size to get more bass output.

Have you modeled this woofer/box combo with something like WinISD ?

If I was going to make a shot-in-the-dark suggestion ( that has some percentage of working out ) it would be to build a pair of Back-Loaded-Horns ( BLH ) for those drivers.

With a bass horn, at least one is generally assured that going bigger gets one more bass output.

From Wilberforce's excellent thread located which is located HERE!

I'm afraid this design is way out of my league at this time. I am new at this but I am aware of the lack of bass for this particular duplex speaker. From my research and calculation, building a cabinet for a single speaker can range between 1.8 and 3.5 cubic feet. My other search in reading someone else's posts stated that Altec speakers tend to like bigger speaker boxes rather than the smaller sized ones. Running Winisd it tells me the proper box should be 1.88 cubic feet, so I am here asking to see if anyone had any experience with this particular driver. The design of bass horn looks amazing, but I don't think I am knowledgeable enough to understand how this works, I will read it up though. Thank you very much.