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Old 12th July 2012, 05:46 PM   #1
opa1 is offline opa1  United States
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Default Sealed FR with Betsy K

This is my first post. I've been lurking here for about a year. I'm wanting to try FR. My system consists of a magnavox pp tube amp at about 10 watts el84, Pro-ject 1 tt and Bx 1001 Corals that need help.
The room size is 9x12x8 tall. I dont listen at high volumes. Music I like are Steely dan, early jefferson airlpane, Beethoven etc.

I have some Coral bx 300 cabs with about 1.31 cu ft inside volume. I want to put the Betsy K's in them. They will be sealed boxes. I can aperiodic them or port also if needed. Cabs measure outside 13w 21.25 h 11.5 d. There built out of 3/4 wood ply of some type.

Other drivers might be better. But Betsy K's are within my budget range

Does this sound like something that would work? Heavy bass not needed.
Thanks.
Mark
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Old 12th July 2012, 06:21 PM   #2
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Assuming ~1 ohm of series resistance, a max flat alignment would be around 2.45 ft^3, so a bit small at ~1.3 ft^3, though you can add stuffing if it sounds 'boomy'/'loose'.

At this size, reflex venting gains you some mid-bass peaking and more power handling down around Fb, so a Fonken style cab may be best compromise.

Overall, looks good for a sub/Sat. system, but would be way too lean below 100 Hz for some of us except in a near-field app.

GM
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Old 12th July 2012, 07:46 PM   #3
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Thanks GM,
So the 1.31 box would be almost bassless. Your dimensions on the mltl tower would work better in the bass dept.? I think they were aroud 38.5t 8.5w 13.5d. With a small port at the bottom. What hz would this go down to?
I dont have room for a sub.
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Old 12th July 2012, 09:26 PM   #4
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You're welcome!

Well, with a simmed half space F3/F6 = ~ 73/57 Hz, it would be severely bass challenged in room by some of us. Your call, of course.

Hmm, these dims are for Ken R, the smallest MLTL I have a record of for this driver, but 'oldtimers' being what it is, don't remember if it's his design or one I did for him. I should have posted the sim.

Anyway, its F3/F6 = ~ 45/40 Hz, so low enough to cover most music before any room gain is factored in and of course can be tuned higher/lower if need be.

Of course, if you can tolerate a larger footprint, then more bottom end is available as well as a bit smoother response, though doubtful the latter would be audible except on some musical passages and even then probably only in an A-B comparison.

GM
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File Type: gif WBAL Betsy-K 40 Hz 'small' MLTL.gif (6.7 KB, 322 views)
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Old 12th July 2012, 09:35 PM   #5
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Thanks, I just noticed that the betsy has its own page here. So a bigger mltl would be even better? What dims do you have on file?
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Old 12th July 2012, 09:47 PM   #6
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Mark,

I'm sure I would prefer the MLTL Gm is recommending over a sealed box. However, I'm not sure how low you'll get with that amp anyway. As nice as those Magnavox units sound, those output transformers will not be bass monsters. You could consider connecting to a sub amp somewhere upstream of the output stage.

At least the cabinets you have know would give you a start, and your impressions could guide your next step.

Paul
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Old 12th July 2012, 09:49 PM   #7
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I just saw your reply. How big can you go? Its tough to beat BIBs, and I can't imagine a better match for that amp. But they are BIG.

Paul
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Old 12th July 2012, 10:06 PM   #8
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I have room for two tall speaks. My maggie has enough bass with the coral's. The coral's are not known for great bass. lol.
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Old 13th July 2012, 04:17 PM   #9
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Quote:
Originally Posted by opa1 View Post
Thanks, I just noticed that the betsy has its own page here. So a bigger mltl would be even better? What dims do you have on file?
Sure! Up to a point of diminishing returns, more Vb = more acoustical efficiency and if nothing else, allows more in room tuning flexibility, so 'BIB' [bigger is better] rules.

A bunch, but around 6.226 ft^3 for a MLTL is probably the point of diminishing returns for your app, so...........

GM
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Old 13th July 2012, 04:19 PM   #10
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Quote:
Originally Posted by opa1 View Post
I have room for two tall speaks. My maggie has enough bass with the coral's. The coral's are not known for great bass. lol.
Again, 'BIB' rules, so if full size BIB pipe horns will fit your room layout, budget.........

GM
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