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KLF tweak....


moray james

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I just spent twenty minutes doing a very simple upgrade and a half hour to listen. This is something that I meant to do over a year ago but some how just never got around to because I gave Klipsch the benefit of the doubt. My mistake. What I did was a very simple experiment and I did not so much as turn on my calculator. I extended the twin vents using some light cardboard. I started with double the stock vent length (2.5") and made up the new vents with a little scotch tape at 5 inches long gave them a listen. then I went up to 12 inch long vents which was the length of the cardboard which I had on hand. The cardboard was simply rolled up and inserted into the existing vent back twisted to make the fit snug and then taped together. This is so simple that anybody who can read this post can do this mod. I can tell you that the 12 inch vents are much better than the 5 inch ones. I can also tell you that the 12 inch ones could easily be longer but you are going to have to get a little creative as you will be running out of cabinet length so maybe an elbow inside or outside makes little difference. External vents would not eat up cabinet volume but then they will be visible from the back side of the cabinet. That may or may not be an issue for you, this is after all just an experiment but I will say that I cannot imagine any of you not keeping the new longer vents. I would guess that the vents could be about 16 inches maybe longer I have not tried this yet. These are no where near tuned as low as my Quartet's which are fitted with KLF20 woofers. I know that these woofers can drop lower than what the present 12 inch vents are allowing. Give this simple mod a try.
For those who are too lazy to try this and just want to know what the new vents sound like well the single thing which will jump out at you will be the substantial increase in low mid clarity and control then of course there will be the bass which did not exist prior to the new vents. Have fun and report back with your findings. Best regards Moray James.

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I just taped the 5 inch ducts onto the 12 inch ones for a total of about 16 inches Things sound better now but they still are not performing at the same level that I achieved runing one of the same woofers in my Quartets. So I am thinking the KLF20may require 18 - 20 inches (or more?) and it would be easier to install external vents with 90 degree elbows.Will follow up later when I get some materials to do this. Best regards Moray James.

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The last pair of KLF20 I modified were a total rebuild with all four baffles removed and reinstalled. I installed extensive internal brace work and at the same time swapped the reflex vents from the rear baffle to the front. This might be an opportunity to route long reflex vents forward to the front side of the cabinet. I have run out of suitable material for longer ventsright now so I will likely pick sone up on the weekend. As it stands I am expecting the vent length to be at least 20 inches best guess perhaps longer. I may use the same test tone that I used too tune my Quartets and simply adjust vent length until the woofer stops moving. Test tone was 31.5 Hz.. Best regards Moray James.

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This is interesting Moray, I found the bass in the 20's kind of resonant and non distinct (atually slightly plastic sounding to me) and set them aside. I have been thinking of them as a upgrade/renewal project but the bass issue haunts me....maybe this is the answer.

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I can say that I have not got these dialed in yet. I mentioned that I dropped a pair of these woofers into my Quarters (one per cabinet) to replace the stock ten inch woofers. I retuned the passive using a 31.5 Hz test tone. The result was deep articulate bass which was in every way shy of level superior to using two HSU VTF2 Mkll subs which are supposed to drop down to 25 Hz. The KLF20 woofer in the Quartet were as extended as the subs but they were far more controled and articulate. So I expect that running a pair will easily surpass a single pair. I would agree with you that the factory tuning of the KLF20 leaves much to be desired and is a shame that they were detuned so much. Why bother with the great woofers in the first place? Well I am glad they did use these woofers as they are very fine drivers. Best regards Moray James.

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definitely will be moving the 20's out and playing with them in the near future after reading this. Moray you bought ti mids from me a while back...were they for your klfs?...not to get off subject but before I start modding the 20's would like to hear feedback on your experience with these.

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I am probably listening to your mids now. I do like to use fiberglass or felt damping pads behind the diaphragms others here may not but I do on tweeters and mids. I love the ti diaphragms and feel they take the speakers to a whole other level of performance which is only hinted at with the stock phenolic diaphragms. If your KLF20 have the stock poly tweeter diaphragms loose them right away as they are hands down the poorest sounding diaphragms I have heard from Klipsch. Replace them with Bob's ti tweeter diaphragms. If you want to get the max sound you might consider a rework on your networks. Hope this helps. Best regards Moray James.

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I also think damping behind the diaphragms is an improvement and have done that with my fortes with stock phenolic mids. All drivers in my 20's are stock so if your port experiment works out for me I'll move forward and change diaphragms...guess I shoulda kept those ti's, but I glad to hear your enjoying them. I am in the process of working over some LaScalas now and am very excited about them, but always need to have the next project planned. Thanks Moray and best of luck.

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You can borrow the phenolic tweeter diaphragms from your Forte's or just swap out the whole tweeter as they are identical to the units in your KLF20 except for the diaphragms. I think a pair of La Scalla's would be a fun project rip snortin fun. Thanks and have fun with your projects too, please keep us posted as to your progress. Best regards Moray James.

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  • 3 weeks later...

I would be just as good with that as you. I will keep you posted. Best regards Moray James.

Did you get more results on the
length of the ports yet. I still did not glue my ports yet so I can
still change them. I also have to paint and assemble the second KLF 30
before I can start testing. I will need to order more pipe and a test CD
too. With my left over pipe I can get the length up to 8 inches, maybe
that would do? Any suggestions on a test CD (for beginners)?

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I have been dealing with distractions which have put my stereo play on hold. You have the KLF30 and I have KLF20 so the vent lengths I find won't suit you. What you want to do is fairly simple. You will need a constant test tone. I think that thirty hertz for your tuning frequency is fine. Play the tone as a reasonable level do that you get the woofer cones moving. Increase the length of the vents untill you get the woofers to stop moving and the vents are doing all the work at that frequency. That will get you there. Hope that this helps you. Best regards Moray James.

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