Altec 806A + 511B Horn + Beyma 12"

Altec 806A + 511B horn + Beyma 12"

This is an quick and dirty digital active system consisting of an Altec 806A + 811B horn + Beyma 12" in a ported cabinet. I put something very similar together almost ten years ago using JBL 4" compression drivers and CD horns. I sold off the parts to this when I moved to SoCal from the Bay Area, and this is ONE speaker that I regret selling the parts to. These ones based on the Altecs are better. Smoother sounding than the JBLs. The multi-cell horn doesn't need the EQ of CD horns.

A 12" in a ported box = win. You can slap an two pairs of of 8-10" drivers together in a sexy narrow tall speaker, and you still will not get the tactile sense of bass drums, bass lines, and oooh, that thump right before the creaky door in MJ's Thriller. And these woofers don't even go that low either. Zero congestion of anything. I need to be careful with volume because I take can the block down with these.

There's also something super special with compression drivers / horns and how they form an effective impedance transformer from driver to air. Super efficiency, super macrodynamics (lack of compression is even evident when playing music at low levels), super low distortion.

 

Which beyma woofers? And what is your port tune? 99% of the time I prefer a sealed enclosure. Would be curious to pop the beyma numbers into winisd and see what the enclosures look like.

 

Beyma 12BR70. I'm a cheapskate. I also didn't want to go for drivers with 400 watts power handling as the surrounds are too stiff for home SPL purposes, and likely impact plankton. They are in a 2.0 ft3 box with multi-layered foam of different densities on the inside walls and very lightly stuffed, which probably equates to 2.2 ft3 effective volume. The box is too small, so bass extension suffers big time, but it's what I had sitting around from prior projects. Ports are tuned to 33Hz to make the best of the situation.

Here's the predictive model


Here's an FFT at the listening position in the garage. The compression drivers are tired. One driver is about 7db down at the high end compared to the other. I used +4db on EQ to compensate. No other EQ was applied. Drivers are crossed over at 560Hz LR12. The 550Hz dip is probably caused by the floor.


Next steps will be passive xover which should be super easy, especially with the multi-cell horns. Haha, the FR is actually less screwy than the Fostex 6" Sigma widerbander drivers.

 

Neeeeed that rack !

 

24" from horn mouth. Not really anechoic as likely some significant floor bounce and cabinets.

 

I'll get some Radian diaphragms with Mylar surrounds. The problem with most of these compression drivers is that they are all metal, including surrounds, and they tend to age badly. I haven't opened them up yet, but I wouldn't be surprised if they were the original drivers from 1963.

 

You can use it as a center channel.

Make sure 1"+ baffle and/or multi material damping inside enclosure walls. Internal bracing is a must. Also what's the port tuned to? Finally make sure they are few feet from the walls.

 

Here is a result from lining the mouth of the horn with felt (from 500Hz up)

No felt, stock.


With thin strips of felt at the mouth of the horn.


Focal Utopia for comparison: