Mystery bookshelf speakers - with pics
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RTally
Speaker addict
Quick update: I cut open the back of one cabinet to inspect the crossover to order new caps. There is a 2 uF and a 5 uF cap behind the speaker terminals.
I ordered caps and put them in the one speaker that was cut open. Damn they sound good - at least the high end does. The box is not sealed because I have not yet added a shoulder for attaching the cut back. The bass is very muddy. The high end, though, sounds good. I have them next to my Rectilinear III Lowboys (which have not been recapped) and the two together sound good. The Goodmans have the highs and the Lowboys have the lows.
I am refinishing the cabinets. After I get both cabinets done I will post a thread showing details.
I ordered caps and put them in the one speaker that was cut open. Damn they sound good - at least the high end does. The box is not sealed because I have not yet added a shoulder for attaching the cut back. The bass is very muddy. The high end, though, sounds good. I have them next to my Rectilinear III Lowboys (which have not been recapped) and the two together sound good. The Goodmans have the highs and the Lowboys have the lows.
I am refinishing the cabinets. After I get both cabinets done I will post a thread showing details.
Retrovert
Addicted Member
Goodmans made really nice drivers. Glad the purchase worked out for you. I passed on a pair of these because I didn't have the space. I have too many speakers, as it is. 
The issue here is that the EE line followed the Goodmans practice of omitting inductors for the woofer and midrange as a cost-savings measure. The EE line was less expensive than some of the earlier units so this makes sense. With a small amount of expense you can make a kick-ass speaker.
You didn't include a crossover diagram, but the two values you listed suggest a crossover of:
You might consider a few modifications:
(1) Adding inductors to the midrange and woofer. The problem is the midrange and woofer will overlap and create all sorts of mess. The woofer should be limited with an inductor to remove the overlap with the midrange. Instead of relying on the mechanical limit, the woofer driver will have lower distortion with an inductor. The woofer is mechanically limited, of course, but it still has distortion out of band since it lacks any annular rings the way a coaxial (woofer plus tweeter) normally has. The midrange's surround could have (but unlikely) been tinkered with to reduce the low end but unlikely. This is just a cost-savings measure which should be fixed.
(2) Add bypass capacitors. Adding (0.1 uF and 0.01 uF) to each capacitor improves its performance. Speeds up response time with higher frequencies.
(3) Add the flowerpot to the midrange. This prevents cross-modulation, which will be a big issue since the midrange back is not sealed. I've elsewhere explained for the Bozak.
(4) Add Bozak cotton batting and a hanging curtain. Since these are infinite baffle, the more backwave you can absorb the better and cleaner your bass will be. So I think adding the hanging curtain will be a dramatic improvement. So will replacing the fiberglass with thick cotton batting.
The issue here is that the EE line followed the Goodmans practice of omitting inductors for the woofer and midrange as a cost-savings measure. The EE line was less expensive than some of the earlier units so this makes sense. With a small amount of expense you can make a kick-ass speaker.
You didn't include a crossover diagram, but the two values you listed suggest a crossover of:
5 uF = 3,979 Hz. Call it 4,000 Hz. So midrange runs 4k Hz to infinity.
2 uF = 9,947 Hz. Call it 10,000 Hz. SO tweeter runs 10k Hz toi infinity.
So it's a two-way with a tweeter for the high-end?2 uF = 9,947 Hz. Call it 10,000 Hz. SO tweeter runs 10k Hz toi infinity.
You might consider a few modifications:
(1) Adding inductors to the midrange and woofer. The problem is the midrange and woofer will overlap and create all sorts of mess. The woofer should be limited with an inductor to remove the overlap with the midrange. Instead of relying on the mechanical limit, the woofer driver will have lower distortion with an inductor. The woofer is mechanically limited, of course, but it still has distortion out of band since it lacks any annular rings the way a coaxial (woofer plus tweeter) normally has. The midrange's surround could have (but unlikely) been tinkered with to reduce the low end but unlikely. This is just a cost-savings measure which should be fixed.
(2) Add bypass capacitors. Adding (0.1 uF and 0.01 uF) to each capacitor improves its performance. Speeds up response time with higher frequencies.
(3) Add the flowerpot to the midrange. This prevents cross-modulation, which will be a big issue since the midrange back is not sealed. I've elsewhere explained for the Bozak.
(4) Add Bozak cotton batting and a hanging curtain. Since these are infinite baffle, the more backwave you can absorb the better and cleaner your bass will be. So I think adding the hanging curtain will be a dramatic improvement. So will replacing the fiberglass with thick cotton batting.
RTally
Speaker addict
Goodmans made really nice drivers. Glad the purchase worked out for you. I passed on a pair of these because I didn't have the space. I have too many speakers, as it is.
The issue here is that the EE line followed the Goodmans practice of omitting inductors for the woofer and midrange as a cost-savings measure. The EE line was less expensive than some of the earlier units so this makes sense. With a small amount of expense you can make a kick-ass speaker.
You didn't include a crossover diagram, but the two values you listed suggest a crossover of:
5 uF = 3,979 Hz. Call it 4,000 Hz. So midrange runs 4k Hz to infinity.So it's a two-way with a tweeter for the high-end?
2 uF = 9,947 Hz. Call it 10,000 Hz. SO tweeter runs 10k Hz toi infinity.
You might consider a few modifications:
(1) Adding inductors to the midrange and woofer. The problem is the midrange and woofer will overlap and create all sorts of mess. The woofer should be limited with an inductor to remove the overlap with the midrange. Instead of relying on the mechanical limit, the woofer driver will have lower distortion with an inductor. The woofer is mechanically limited, of course, but it still has distortion out of band since it lacks any annular rings the way a coaxial (woofer plus tweeter) normally has. The midrange's surround could have (but unlikely) been tinkered with to reduce the low end but unlikely. This is just a cost-savings measure which should be fixed.
(2) Add bypass capacitors. Adding (0.1 uF and 0.01 uF) to each capacitor improves its performance. Speeds up response time with higher frequencies.
(3) Add the flowerpot to the midrange. This prevents cross-modulation, which will be a big issue since the midrange back is not sealed. I've elsewhere explained for the Bozak.
(4) Add Bozak cotton batting and a hanging curtain. Since these are infinite baffle, the more backwave you can absorb the better and cleaner your bass will be. So I think adding the hanging curtain will be a dramatic improvement. So will replacing the fiberglass with thick cotton batting.
Thanks for the suggestions. It does have a simple crossover. As I found them, they sounded like a blanket was thrown over the speakers, although the bass was good. With new caps, they really opened up except the blanket now covers the woofer (muddy bass due to the unsealed box). If I keep them, I may experiment with the crossover. I replaced the 2 uF with a film and the 5 uF with electrolytics. I have some 5.1 uF films I may use instead of the NPE. Another speaker nut in town said he wants these, so I may let him spend the bucks on getting the most out of them. I am just playing with them to see what they can do.
According to the specs I found at hifiengine, the crossover frequencies are 3kHz and 8kHz. I assume the actual impedance at the crossover point is different than the nominal impedance, thereby accounting for the difference in your calculations.
As for 3), the 6" mid has a sealed back. The flower pot seems unnecessary.
Ignore the sawdust. I took the pic before vacuuming. The 6" mid appears to be a CTS (137 code). The back side of the mid has a solid, enclosed frame. The 3-1/2" tweeter has no markings that I could see.
As for 4), replacing the fiberglass with cotton batting seems to be in order. I've bookmarked your posts about the curtain.
Retrovert
Addicted Member
Ok. My EE 10's are 8 Ω, and as the specifications show.
But the numbers do not work. Again, f = 1 / (2pi x R x C)
At 8 Ω we have the numbers I set forth.
BUT, if the speakers are 10 Ω the numbers match. Given 10 Ω:
Which raises the question: what is the nominal impedance of those drivers?
But the numbers do not work. Again, f = 1 / (2pi x R x C)
At 8 Ω we have the numbers I set forth.
BUT, if the speakers are 10 Ω the numbers match. Given 10 Ω:
5 uF crosses at 3,183 which is 3,000 Hz.
2 uF crosses at 7,962 which is 8,000 Hz.
2 uF crosses at 7,962 which is 8,000 Hz.
Which raises the question: what is the nominal impedance of those drivers?
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Retrovert
Addicted Member
Ahhhh, I see the magic. The flyer to which you linked states at the very bottom:
So this maybe was a Goodman's design and fabricated in Long Island using US components?
Interesting.
Who made the woofer?
A Design Product of ELITE/GOODMANS OF ENGLAND, Farmingdale, L.I., New York 11735
So this maybe was a Goodman's design and fabricated in Long Island using US components?
Interesting.
Who made the woofer?
Freds.Bands
Live Music Listener
I don't like the way the mid and tweeter are mounted to back of baffle; this tends to beam their response.
RTally
Speaker addict
The 12" woofer is another CTS driver. It has a cloth surround that is inverted.
I need to take pictures after I vacuum the sawdust.
RTally
Speaker addict
I played the speakers upside-down yesterday as I waited for the oil to dry on the speaker bottoms. I put the speakers right-side up today and the base is much improved. Not perfect, but better.
PS: I am not doing any critical listening. These things are in my cluttered office.
RTally
Speaker addict
If I keep these speakers, one mod I would do is to chamfer the driver openings in the baffle. The baffle is 3/4" MDF with straight-cut openings.
Retrovert
Addicted Member
Yes, baffle chamfering (which I suggested in #13) is a good idea. Inexpensive, too.
So it looks like the US Goodmans sourced some CTS drivers and built an infinite baffle cabinet matching specs created by UK Goodmans. Interesting.
I think if you line the interior with thick cotton batting the sound will greatly improve. Same for the curtain to avoid the woofer strangling itself. It is an inexpensive experiment and will demonstrate why infinite baffle is such a nice technique, as long as one has the room to hold the larger cabinet.
So it looks like the US Goodmans sourced some CTS drivers and built an infinite baffle cabinet matching specs created by UK Goodmans. Interesting.
I think if you line the interior with thick cotton batting the sound will greatly improve. Same for the curtain to avoid the woofer strangling itself. It is an inexpensive experiment and will demonstrate why infinite baffle is such a nice technique, as long as one has the room to hold the larger cabinet.
