Genesis II - Rebuild - Design Comments

[Pete B]

I always liked the EPI-100/Genesis 1 speakers and thought how much better they would

be with bass comparable to the Large Advent. The EPI-100/Genesis 1

were simple 2-way designs with an 8" woofer and a 1" inverted dome

tweeter.

The Genesis II took this simple design and added a 10" passive radiator in a much bigger box.

The result was better bass, deeper and more powerful than the Large Advent as I recall, they

are very close in the bass. Here's a picture:

http://www.humanspeakers.com/genesis/images/gen2a.jpg

I heard them often in show rooms, one shop liked to compare them to the B&O systems using

the filler driver idea. There was no comparison in my opinion, the Genesis IIs were far superior

at about $320 to $400 a pair, a fraction of the B&O price. They sound best

with the tweeter level control set for some attenuation.

I probably would have bought these speakers if I didn't build my own at the time and

considered them to be the best at this price point. I compared them

to my reference after restoring them which confirmed my old

impression. Very natural tonal balance with the tweeter control

down. Intermodulation can be heard when they're pushed

hard to the Xmax limit, which is loud!

I often suggested them to friends and my sister-in-law chose them.

Her's have needed refoaming for some time now and I offered to repair them.

I used standard PE refoaming kits that my brother had already purchased for the 8" woofer

and 10" passive. The 8" measured close to specs listed at the human site, Fs was slightly high.

A mechanical drawing of the EPI/Genesis driver can be seen at the Human site:

http://www.humanspeakers.com/diy/parts/001.htm

This 8" has a one way Xmax of .25" or about 6mm which is twice the

very common 3mm seen in the older high quality European 8" drivers.

It also had a very high mechanical Xmax limit as a result of the tall

double stack 10 oz magnets.

Here's a picture of the back of the 1978 Genesis II woofer next to

one of my favorite low cost 8" drivers the 8" Eclipse:

http://members.aol.com/basconsultants/GENWOF-B.jpg

The 10" passive radiator is robust, very large spider, slightly

larger than that used in the large Advent. The foam limited Xmax

slightly, and I measured the one way mechanical limit at about .8"

I measured Fs, by hitting the cone with a pulse (my finger) and

measured the natural resonance with a microphone and PC based

storage scope at 17.2 Hz. This is somewhat high, the lower the

better with a PR, and I'd probably use the RSSOUND Advent foam if

I were to ever do another pair. The PR is tuned to 32 Hz in system,

a sensible choice, but I'd probably tune a bit higher for better

power handling. I'd choose 35-38 Hz.

The enclosure is stuffed with fiberglass, 6 strips running top to

bottom, which is not what is traditionally suggested for a vented

system. It helps with the slightly high Q woofer, and helps to

reduce midbass cavity modes in the box.

The driver layout with woofer over tweeter helps to advance the

woofer in time relative to the tweeter and this is the first

implementation of this layout that I've seen. It can be seen

today in PSB and NHT speakers.

Getting late, I'll have to continue this another time ...

[dynaco_dan]

Hi Pete;

An excellent and very detailed write-up from you, as usual, thank you.

[Pete B]

Thank you Vern, nice to hear from you as usual.

[Pete B]

I forgot to mention that very cheap spring loaded push terminals are used in Genesis speakers, and it's hard to describe how much I dislike these. I was tempted to replace them but my brother likes things original so I left them.

I checked and measured all of the crossover components both DC resistance and impedance. Everything was fine, one of the caps was leaky at rated voltage and I had planned to replace them anyway.

I disconnected the original 10 uF NPE crossover caps and they were glued in so strongly that I just left them in place.

I used 10 uF GE poly caps from Madisound with .37 ohm 5W resistors in series to emulate the ESR of the original caps.

Reflowed all of the solder joints.

The tweeter terminal lugs are riveted in place and the signal passes through the rivet joint. These looked to be made of brass and were somewhat tarnished, so I cleaned and soldered this mechanical joint.

I left the original wiring and cleaned and soldered all of the speaker lug connections.

That's it for this rebuild.

Additional repairs that I'd do if these were my speakers, and for a

stock rebuild:

New input posts, low cost gold plate types.

Replace the driver screws with machine type and steel inserts.

New internal wiring.

[Pete B]

A few suggestions, just in case anyone would like to experiment.

I had wanted to experiment with better placement of the internal fiberglass. There are 6 pieces running front to back. I'd staple one on each side wall, three on the rear wall, and put one folded behind the 8" woofer only. This should leave some empty space behind the passive radiator which usually offers the best performance.

I'd experiment with higher passive radiator tuning which is probably not possible with the current PR since mass must be removed. A replacement PR could be used.

The 8" woofer and 10" PR remind me of the Vandersteen 2C which uses a driven "passive" radiator. A real woofer driven through a large inductor could be tried in place of the PR. The Eclipse 10" comes to mind.

The original 8" woofer produces high levels of IM at long excursions and I'd be curious to try the Eclipse 8" in this system.

A 3 or 5 position tweeter control would offer more flexibility as I prefer 1 or 2 dB less than the lower tweeter setting.

Once again this is an excellent speaker even in stock form.

[Pete B]

I did some quick frequency response measurements, nearfield below about 200 Hz and MLS above. I noticed a very narrow notch between 1 and 2 kHz and thought that it seems more like a destructive reflection than a crossover issue. I did not notice it in listening tests and wondered if it was a measurement issue. There was mention of it in another forum, I'll try to find it.

I did not find this to be audible in my listening tests.

[Pete B]

I wondered years ago if Genesis had licensed the EPI design or simply copied it. I do remember hearing the story that while they obviously taylored their speakers after EPI, they did their own design work at Genesis.

It is clear that the Genesis and EPI tweeters are different. The EPIs have a paper dome, and a soft cloth suspension whereas the Genesis have what seems to be a heavier, phenolic impregnated cloth and the suspension seems to be stiffer.

There is a fellow (Brian Levy) on the Audio Asylum board who worked at Genesis as the companies controller and he confirms this story:

Posted by Brian Levy on January 07, 2005 at 10:16:25

In Reply to: Re: Huw worked at Genesis, not EPI posted by DavidLD on January 7, 2005 at 09:46:14:

Actually, the companies did not share componnts as they were separate and distinct with seperate development departments. The inverted dome tweeter was developed by EPI and later Genesis sort of borrowed the design and made their own version. In the beginning some of the EPI investors backed Genesis but by the early 70s George Samuels was in control and there was no love between the companies. Genesis went out of business in the 80s and the name was bought by another company and sold Genesis speakers but these had no technology relationship with the originals.

I would connect them only in the fact that they used the inverted dome technology and both were in NH. Other than that not really connected.

Here's the post where Brian Levy states that he was controller for Genesis Physics:

Re: Brian, a little off topic... - Brian Levy 18:30:19 04/13/04 (3)

In Reply to: Brian, a little off topic... posted by rodney on April 13, 2004 at 10:22:18:

Started in electtonics in my father's store in 3rd grade- 1953. Touched the HV on a picture tube standing in a puddle of water in his repair shop. From there learned the trade, weekly member of the local ham radio club, held several tickets before a teenager. Rebuilt from scratch a Motorola console tv/radio/phono. Weekly trips to Boston where I met some of the "founders" who knew my uncle, a sales rep for electronic tubes and parts. Started hussling, running with the crowd, a couple of years in NYC at RCA tech and learning interesting things about direct drive 8 track motors produced by Lear Jet. Moved on to sales and management at Cramer Electronics in the Boston area that eventualy was bought out by Olson Electroncis, then a short stint in Boston as a manager for Tech Hi-Fi, bought 4 Tech franchises, sold them went on to finish A.Sc. in Business Management, B.Sc. in Accounting. Controller for a couple of companies including Genesis Physics in Newington; them to Florida and law school and an interesting case involving a Japanese patent suit against British companies related to the bi-amp internal crossover which sort of brought my interests back into audio as a hobby. Teen years were great since I kicked around between Boston through NY corridor with some great older friends who are now the legends so often spoken of here. Sadly, as I found out during the Japanese law suit, all were dead or just shy of it.

That's it in a nutshell.

[peter99]

I rebuilt my 320's and the human site did not match my crossovers at all. I suggest numerous pics to be able to redo caps like I did.. Esr meter to match caps values and specs... Nice solder gun, lots of how to solder i=on interweb.. A hot glue gun which you will use a lot.. Ebay has parts like tweeters if you blew yours.. Mine still crank away on my 7.1 system...  use a paradigm  center..