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50% off to take Betsy where she's never been!

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Hey thanks Tbag, I was surprised by just how darn good it looks. I was a perfectionist when building but now I realize there's not much I could do to make it look bad. I was worried about the speakers being so low. I wanted to put them higher but decided against it.

I was sort of worried about the stereo separation. I would have made the whole thing larger if my room wasn't so small. I haven't tried putting damping behind the speakers yet. I was thinking of stretching a couple layers of soft towels over the back of them. With my head near the back of the baffle next to the wall, I can detect a few small peaks when doing a frequency sweep.

Actually the bass still seems a little minimal, but perhaps it only seems that way since the bass no longer distorts so badly and I'm used to my old speakers.

- keantoken
 
The response is actually amazingly flat compared to my old speakers. I've been doing some more controlled tests and I think what I detect for the treble and highs is resonance and reflections and phase stuff from my small room. I don't think there is much difference at all for pure response.

The bass begins to become audible at 52Hz. You are right, any peaking is somewhere around 120Hz, but it seems more like a phase difference between the sides of my head than anything (I sit at a right angle to the speakers on my computer...). The rectification frequency in any amp is at precisely this frequency, so the amp may have some affect too. (wait, I think my car amp uses a switching supply...)

- keantoken
 
music soothes the savage beast
Joined 2004
Paid Member
this fr response is what I got on betsy-wow
 

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Is this strange?

As I increase the series resistor, the response around 174Hz dips, instead of peaking. This is a spread out dip, between C3 and C4 (130Hz to 261Hz). This has the effect of seeming to drain the life out of music if it's strong with a large series resistor, since it cuts out the lower midrange. From here it gets louder rather steadily with increasing frequency. Shouldn't the response peak instead of dip?

- keantoken
 
I'm not sure what to do now:

Was expecting low QTS suitable for Karlson loaded project...
Might have received open baffle Betsy (without the K)?
Its a nice speaker. Can still use for something, I suppose...
Just maybe not for same plan as I had originally posted.

Sais "Betsy" on both the box and the magnet...
And QTS measures 0.8 as-if optimized for an open baffle.

Kean said something about adding a series resistor before
his open baffle sounded right? Maybe he got my low QTS
K's? They were both ordered and paid on the same check.

Kean, what yours say on the magnet? Was there a sticker?

This was after about 10 min breakin at very low volume...
Just using WT3 tester itself to play some music in Mono.
Measurements made in fee air (very hot and humid), and
with 20g non-magnetic weight added (4 US Nickle coins).
 

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I got OB Betsy with thin magnet, bumped back plate, and vent hole.
Fairly sure of it now... Though I still wonder which type Kean got?
Can't fathom Kean's preference for series resistor if his OB Betsy has
the same curves as what I just measured? If BetsyK, would explain.
I suspect shipments (I ordered and paid for both) got wires crossed.

Not certain I can use 0.8Qts for my 3rdK12 project? Unless I don't
use fullrange, but cross down to 1955RE Karlson K15 (overstuffed
with SigmaPro18) at some frequency well above Betsy's Q peak.

Even then, I doubt 90db sensitivity is useful matched against 97db.
How much could I boost Betsy's effective sensitivity, tightly cupping
the back? I mean, if I was to intentionally cut off all the low end and
send Fs and Q skyrocketing, but cross to 18 well above that mess...

Compare Alpha-8 against Alpha-8MRA, I think the closed basket is the
only major difference? But the sensitivity went way up as the low end
of useful bandwidth got whacked... Would it be the same on Betsy?
 
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I got BetsyK's, that's what the labels say. Both you and Paul suggested to get them, so I thought "it's got a whizzer cone anyway, those are cool".

I'm currently happy with a 25 ohm series resistor. It's really strange, they suddenly sound really nice now, they sounded a bit unnatural before. Either my ears have adjusted, or they've hit some sort of break-in point.

- keantoken
 
re:3rd K12 - I picked up a set of 4-slit vent factory K12 with ~30 degree baffles and IIRC (?) they're about 24.75" tall and built like John's X15 as far as using 3/4" veneered particleboard and would think the Tannoy set of 3rd K12 we saw on auction to be built using the same stuff (Novaply?) You need at least the BetsyK - FE206E aren't too strong for K12
http://img535.imageshack.us/img535/6747/jekk124vent.jpg
 
I hope I've not done something wrong. I surely got BetsyK's, and I asked for them when offered. Ken, you surely got the Betsys. Don't feel too bad, one of mine were damaged in shipping (damaged a speaker in shipping! WHAT do those guys do with the boxes?). It's still listenable, I'm waiting a few weeks before Paul can replace it. I looked at the box today, this must have been what did it.

- keantoken
 

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I'll just send you these Betsys. If they sound better without resistor,
then you can trade me the K's. If K usable, I won't care a slight ding.
Parts express sent me THREE times a Dayton loudspeaker (for Tritrix)
with seriously bent frames. Even one with no external box damage,
except that it had obviously been opened, and re-taped several times
before... Warpage far too severe to consider fixing with a mallet, as
coil felt like it might have a rub. Some of the lower end Daytons got
real wimpy thin steel frames. Betsy frame feels much more substantial.

Paul shipped my boxes taped together, probably a good idea. But even
better if you can figure which end is magnet and orient magnets toward
outside. Frames fronts toward center, where they are better protected.
The outside corners and edges of a heavy box can really take a beating...
Best that nothing delicate occupies the zone of maximum risk. Even then,
shippers will find some way to destroy 10%, what can you do?

Both my boxes look fine, I've only opened one. There is a staple in the
inner cardboard that slightly tore the front gasket. You really can't see
the small tear, and won't be cause for return. I'm just noting there is a
heavy staple needs to be relocated to a safer location, or curled more
fully into itself, that sharp points can't rip gasket...
 
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Ken,

I was thinking you wanted the Betsys, but now I remember the Karlson project. I'm sure I just goofed up. You indeed did get the Betsys, so the Qts you measured is dead on. If you and Keantoken want to trade, I sure wouldn't complain. Otherwise, email me and we'll work something out. I've got K's I could send you ASAP. Either way, I owe one of you a new BetsyK. I'm not sure what happened to that one in shipping. The cone shows a little damage, and I'm not incredibly comfortable with that. I've never lost one in shipping before. My packaging isn't fancy, but it has proven to be highly cost effective. Let me know where to ship the replacement BetsyK.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
 
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