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Forgive me for repeating myself. This is a revival of the "add a ported low box to a La Scala" thread from a while back.

http://forums.klipsch.com/forums/t/104516.aspx?PageIndex=1

So, as I said, I built one. Opinions are on the tail end of the other thread but tonight I put the eating into the pudding. 'Scuse me while I whips this out! Time to drag the interface, calibrated mic & Spectra-Foo to the party.

Picture below is Pink Noise at 1M, mic is on the floor (less muddying results from 1st reflections). Green trace shows La Scala without the Bass Port, Blue is with.

porttest1.png

Not too impressive I have to sayand not totally correlating with what I heard.

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So, as the old adage goes; if you can hear it and not measure it then you're measuring the wrong thing. This time I set a 20 second sweep from 20Hz to 100Hz and captured the peaks.

Once again, Green is sansBass Port, Blue is with.

porttest2.png

Now isn't that a lot more fun? Even allowing for measurement errors I think we do see a subtle lift at the low end (the dip at around 58Hz is probably a room node cancellation).

As I said in the other thread, if you're looking to throw away your HT subs this is not going to do it for you. However, sonically my first impressions are favorable.

Let me know if your mileage has varied.

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Edit : after re-reading your post. Don't pay too much attention to anything above 100Hz, I had the analyzer bandwidth cut-off set pretty low plus the mic is on the floor in front of the bass horn. The advantage to this is less problems from 1st reflections, the disadvantage in La Scalas is you're not looking at the horns even with an Omni.

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This was the data by one of the guys (Thermio if I am correct):

HZ 200 160 125 100 80 63 50 40 31.5 25 20
--- --- --- --- -- -- -- -- ---- -- --
dB 77 80 79 73 72 78 68 60 61 52 51 Stock w/sides braced
76 78 78 73 69 75 65 60 66 56 52 4.5 cuft, no ports
76 78 77 75 74 80 70 60 68 54 54 2 ports 4"dia 10"
76 79 78 76 75 80 71 60 68 54 53 Ports cut to 7"


As you can see the numbers don't change much but you were right: the sound does. Much faster and distinct. I am guessing this is a good stopping point with this driver (K33E). It is the best sound of the expansion/port series to my ears but I have only listened a little bit.
------------------------------------------------
As you can see, tuning ports at 7" boosts the 100 to 50Hz range where most of the slam and punch of percieved bass resides, yet the lower bass still has significant gain at 31Hz. A win-win solution.

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Thanks for posting these numbers, I hadn't seen them before.

Looks like he has a null at around 40Hz which repeats itself as a harmonic at 80Hz? Without knowing if this was done with Pink or Sweeps, averages or peaks make it hard to compare with my results. A 7dB difference at 31.5Hz seems too good to be true but his plots do show (like mine) that above about 55Hz the curves basically combine.

Certainly, for a $26 piece of MDF & $10 worth of 4" pipe it's a bargain however you look at it. I'll hopefully report back with a pair plus better construction (I'll rebuild numero uno) and sealing tomorrow.

How confident are you in the side bracing? It seems that it would have occured to PJK and been there if he thought it warranted.

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ok, thanks for the clarification on measuring technique. the lift of 4-6 db from 30 Hz and down is probably quite audible although there aren't many fundamentals down there, boosting the sub frequencies should give more authority to the punch of the LS bass around 80 Hz.

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How confident are you in the side bracing? It seems that it would have occured to PJK and been there if he thought it warranted.

Klipsch actually did the side bracing on some of the pro models (I've got a pic or two showing them), however, they didn't have CNC and these were all more hand assembled, so you had to custom fit the braces. This wouldn't be very cost effective from a manufacturing standpoint.

The LSII uses 1 inch sidewalls to stop the resonance.

post-7149-13819454587202_thumb.jpg

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...however, they didn't have CNC and these were all more hand assembled, so you had to custom fit the braces. This wouldn't be very cost effective from a manufacturing standpoint.

I find that hard to believe from a company that cranks out Klipschorns?

So, court is back in session. Box #2 is complete, here they are prior to finishing -

portboxes.jpg

And with the La Scala (ports are backfiring) -
DSCF3670.jpg

So far my impressions are that 2 is better than 1. Once again, the lift is subtle but very pleasant. This is not pants-leg flapping low end but it is very articulate and musical. I am planning to strip & re-oil the LS's, once I get on that I will laminate & match the bases.

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I find that hard to believe from a company that cranks out Klipschorns?

They do now, but a lot of it was hand work. Maybe Roy would see this and tell us when they started using CNC in Hope. I only know that people have mentioned that they had to hand fit the braces when they added them later.

Here's a built from scratch LS clone with the ports. This one, obviously, is on its side, with an Oris horn on top.

Bruce

post-7149-13819454601526_thumb.jpg

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