Can you turn a woofer into a full range driver?

[kach22i]

Ignorance is bliss, so I must be in bliss.

I will attempt to turn a 4" and a 8" carbon fiber woofer into a 4" and 8" full range drivers.

Gjee Whizzers.

Almost reaching as high as 10khz, they just have another 10 to go.

I expect what ever I do shall suffer beaming or shouting issues, so I also plan to incorporate some sort of blocker/diffuser into the final design. I imagine a sphere or half-sphere hovering over the cone/whizzer area.

Much to my surprise the CF drivers are very dry and paper-like. There is very little resin on them. So little resin in fact that part of my design may be to add epoxy resin to either the front or back and stiffen it up. Which in turn should raise the frequency response, be it at perhaps a more jagged or peaky level.

If you want to hold your opinion until after I do things, that is fine. I do plan to experiment on a big cardboard box full of spare drivers before touching the CF drivers I actually spent money on and not found on the curb when the college students moved out of town last spring.

Anyway here is the MCM 4" and 8" carbon fiber drivers selling for what I think is a fair price. All I can say about MCM is that one of my $6 back-up tweeters I bought in case I fail at producing a super whizzer came in damaged from shipping. I called them and they are mailing me a new one - just like that.

Pictures: Yes that is a vented pole piece on the 8" driver, just like the big boys have.

8"


4"


Both



Poor little tweeter.................



I'm not sure, but I think that the light coming through the drivers is actual air hole openings in the CF weave, and not just translucent resin. I will take a close look when I have more time. Somehow this just feels wrong, I'm open to hearing your opinions on this as it could be not normal.

I hooked them up and they play, only did low levels for a few short minutes but already have some first impressions "in free air".

1. The 8" driver has a rich deep sound and nice fast bass, but I will be hard pressed into converting this into a full-range unit. Vocals are good, bass has depth, just no zing at the top end "as is".

2. The 4" driver lacks the large uncongested openness of the 8" driver but should be a breeze to convert the upper frequencies. Vocals are there, not as rich as the larger driver though.

3. I also hooked up the tweeters to test them, they are not very efficient compared to the sound levels at the same location on the volume control. It will be interesting trying to match sound levels with the mid-woofers, if I go that route as a last resort.

Link to CF drivers below (the top two), PDF's in link provide frequency response charts.

Search results for "mcm die cast woofer 55-3*"

That is all, except you might want to see the Whizzer Thread where I posted some research images and links.
Whizzer Thread

[David Pinnegar]

Hi!

Does that woofer have a hole in the middle?

Then remove the dustcap and poke a tweeter behind down the hole . . . and put two 3.3uF capacitors in parallel in series with the tweeter, possibly antiphase electrically to the woofer . . . and you might be surprised at the result.

Provided the crossover is gentle then you can get the sound from the two units really to coalesce in a way that's near impossible with two separate units. Two units giving same frequencies give interference patterns - but coaxially, no interference and the tweeter can simply add to the woofer and take over where the woofer falls off mechanically.

Best wishes

David P

[kach22i]

Originally Posted by David Pinnegar

Provided the crossover is gentle

I've seen the tiny Piezo tweeter modification in the middle of the woofer hole. I thought they used a "choke".

I'm not sure what this "choke" really is but assumed it was some sort of frequency filter filtering out the lows and not a full blown crossover.

I do not know what is behind the dust cover of either woffer driver.

I want to play with the super whizzer concept because I don't think anybody has done it with a beam blocker type diffuser in mind from the start.

[kevinkr]

I'm wondering if the voice coil inductance on the 8" driver would attenuate HF response significantly in addition to the other problems you may encounter..

As to those light spots take a small pin and use it to see if there is resin there or not, if not it will go right through, if there is it won't unless you deliberately force it. Don't..

[kach22i]

Maybe the annular ring on this vintage Goodman diffused a hot spot from the lip of that horn-like throat.
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[IG81]

Fun project, even if it does not end-up working, it'll be educative at least.

The coaxial tweeter trick solves the point-source problem, but then time-alignement become more important IMHO. I guess I shall see, as I'm also experimenting with drivers, putting together some coax units.

Good luck and keep us posted!

IG

[FullRangeMan]

Hi
Nice experiment. FR drivers needs very light cones and loose suspensions, and woofers usually needs the opposite, seems you will need to lighten the cones and soften the suspensions and spiders.

AudioNirvana are very sensible prices, but would be interesting see a 15 inches woofer as the Eminence Alpha15A or Elegance DIPOLE-15 turn into a FR.
Good Luck, Gustavo

[Pano]

That Axiom was an expensive driver! Likely $400-$500 in today's cash.

[j.michael droke]

Hi there: Have you considered that the designer of the 8-inch MCM 55-3550 carbon fiber cone speaker has used the perforated cone as a compromise to provide a suspension system with complience that varies with frequency. If so, altering (closing) the preforations may adversly affect the existing extended response of the driver. This extended range driver may respond in HF range to the addition of a wizzer and phase plug/difussor as other have done, however it does not seem to be a canidate for full range. (what is your definition of full range). ... hpoe you keep is posted, and provide listening experience....regards, Michael

[kach22i]

Originally Posted by j.michael droke

designer.....(may have)..... used the perforated cone as a compromise to provide a suspension system with complience that varies with frequency.

Excellent point, when you change one thing it is bound to affect other things - it all works together as a system. You insights are appreciated. This is not my area of study, I'm just jumping in and having some fun.