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KLF-30 Redesign

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Came across a set of 30's for the right price so I decided to attempt a ground up re- design in an attempt to finally squeeze from this speaker the bass it SHOULD be producing. Although I currently own a pair of KLF 20's and a pair of KLF 30's, I couldn't pass these up at the price point I STOLE them at. Planning to reinforce the cabinet to the tune of 1.5" mdf ( box-in-box) with all the proper dampening, insulation, bracing, etc. Cabinet re-tune, correct those useless ports, and in all likelihood will try a non-crites crossover custom built by Norman Cerveny Pro Audio. Will refinish the outer cabinet as well with unfinished wood veneer with many coats of Hi Gloss lacquer, haven't decided on a stain color yet. Although KLF 30 mods are fairly standard these days, Norm Cerveny will be doing these from start to finish since this will be more than a simple modification.

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Hmmm, I'm probably clueless but who is Norm Cerveny and why would his crossovers be better than others?

 

BTW, the ports aren't useless though you might not like them, they are for specific tuning and angling out the back to likely avoid mid-range bleed through.  What size internal enclosure volume are you intending on using and what cabinet tuning frequency along with size of port(s)?

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correct those useless ports

 

I'll be following this thread as I have two pairs of 30's.

 

As far as the ports....I modified mine (super easy) after extensive experimenting with lengths varying from 5" all the way up to 18". I settled on 18" ports.....10" sticking inside the cabinet and 8" sticking out. Probably sounds strange and I was hoping something like 5" or so would be what I would settle on but the best results kept going back to the 18" port (10" in 8" out of the cabinet). Maybe it's a room thing...distance from the wall etc. but it was easy and fun to experiment with. Not to mention it improved the overall sound of the speaker.

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Use pvc and make right angle ports inside the cabinet. Or use what I did on my CF-3's...cardboard carpet roll tube. You can cut either for a right angle but pvc let's you use pvc cement, obviously. :D Cardboard can be done with silicone or gorilla glue. Did that for 25 years in car audio sub cabinets.

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Or use what I did on my CF-3's...cardboard carpet roll tube.

 

How much longer did you make the ports?

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Remember, when they are inside the speaker, the ports use up cabinet volume so the sound will not match if they are outside of the cabinet now.  Purchase one of the Parts Express analyzers for impedance and you will be able to see how the tuning affects the woofers based on port size, length and cabinet volume.

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Factoring in how much the port displacement is, is pretty neglible. It's no worse than adding in all the bracing that gets done. But I agree in that an 18" port inside is pretty extreme. That comes out to .165 cu/ft port volume displacement if 4.5" o.d. with a 4" i.d. 18" long. And isn't there 2 per cabinet?

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Or use what I did on my CF-3's...cardboard carpet roll tube.

 

How much longer did you make the ports?

They are 5.5" in length from from edge of stock plastic port to back edge of port, if I remember correctly. Maybe 6 at most.

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Hmmm, I'm probably clueless but who is Norm Cerveny and why would his crossovers be better than others?

 

BTW, the ports aren't useless though you might not like them, they are for specific tuning and angling out the back to likely avoid mid-range bleed through.  What size internal enclosure volume are you intending on using and what cabinet tuning frequency along with size of port(s)?

Norm Cerveny is a custom speaker designer whose designs have won several national competitions, your ears will tell you why his crossovers are so acclaimed. Never had a problem with bleed thru even when I experimented with closing the ports all together the k-52 really pushes hard. Enclosure will be 3/4" smaller, haven't gotten to the tuning yet but we are getting close still working on the cabinet. Definitely will post when tuning is complete.

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correct those useless ports

 

I'll be following this thread as I have two pairs of 30's.

 

As far as the ports....I modified mine (super easy) after extensive experimenting with lengths varying from 5" all the way up to 18". I settled on 18" ports.....10" sticking inside the cabinet and 8" sticking out. Probably sounds strange and I was hoping something like 5" or so would be what I would settle on but the best results kept going back to the 18" port (10" in 8" out of the cabinet). Maybe it's a room thing...distance from the wall etc. but it was easy and fun to experiment with. Not to mention it improved the overall sound of the speaker.

Norm is considering down firing the ports since I have carpet in my listening room. Not sure what the distance from the floor will eventually be. Gonna post some pics this weekend.

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Good luck on the design.  

 

I would be considering adding some volume to a KLF 30 vs removing.  Since the ports are to the rear, you wouldn't notice the mid-range bleed through unless you specifically tested for it with everything else turned off.  The fact that they are in the back and minimal enclosure stuffing will tell you right there though sometimes that bleed through can make the speaker more appealing.

 

If you are dropping the size, you will be dropping the port size or making them longer.  If the ports are facing the floor then that will be helpful in removing any unwanted wind noise or mid output.  

 

You must be going to use these with a sub, correct?  The 30s don't get super deep as it is with their small enclosure.

 

I would be looking at larger enclosure with somewhat lowered tuning, and if you are doing a crossover, adding an 8" mid bass or possibly 2 6" to clean up the discontinuity between the mid horn and the woofers.  That would address the KLF 30's weak points.

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Good luck on the design.  

 

I would be considering adding some volume to a KLF 30 vs removing.  Since the ports are to the rear, you wouldn't notice the mid-range bleed through unless you specifically tested for it with everything else turned off.  The fact that they are in the back and minimal enclosure stuffing will tell you right there though sometimes that bleed through can make the speaker more appealing.

 

If you are dropping the size, you will be dropping the port size or making them longer.  If the ports are facing the floor then that will be helpful in removing any unwanted wind noise or mid output.  

 

You must be going to use these with a sub, correct?  The 30s don't get super deep as it is with their small enclosure.

 

I would be looking at larger enclosure with somewhat lowered tuning, and if you are doing a crossover, adding an 8" mid bass or possibly 2 6" to clean up the discontinuity between the mid horn and the woofers.  That would address the KLF 30's weak points.

Thanks for the tips. Was hoping that a major dose of acoustic dampening will address the slightly smaller enclosure issue. With regards to bass, this whole re-design is an effort to squeeze out a bit more bottom end thump. Will coat the spiders and anything else we can come up with. Last resort will be replacing or adding drivers.

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correct those useless ports

 

I'll be following this thread as I have two pairs of 30's.

 

As far as the ports....I modified mine (super easy) after extensive experimenting with lengths varying from 5" all the way up to 18". I settled on 18" ports.....10" sticking inside the cabinet and 8" sticking out. Probably sounds strange and I was hoping something like 5" or so would be what I would settle on but the best results kept going back to the 18" port (10" in 8" out of the cabinet). Maybe it's a room thing...distance from the wall etc. but it was easy and fun to experiment with. Not to mention it improved the overall sound of the speaker.

Did the longer tubes effect the bass response?

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Shrinking the cabinet will raise the cabinet tuning.  Those 2 x 12" need a fair amount of volume air otherwise you will trade bass extension for a bump higher up.  You can lower the tuning with smaller/longer ports but then you are getting into a trade off of likely having noisy ports.

 

The (considered) minor trade offs of the slightly smaller cabinet volume for the ports being internal with the current volume might not sound like much but every little bit you take off the volume that is already in my thoughts too small, will raise the tuning and affect the bump you will create in the lower/midbass.

 

Adding a lot of dampening in the cabinet seemed to make the bass (to me) less punchy and more woolly.  May have been the tube amp at the time but that's when I realized the woofers need air volume.

 

If you are using several subs that can match those multi 12" in output down low and you aren't asking for low bass from the KLFs, then it won't hurt to tighten it down.

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Did the longer tubes effect the bass response?

 

Yes. The bass plays deeper. How much deeper I don't know but it makes the speaker sound cleaner. Like I said...it could very well be a room thing I don't know for sure but it's easy and super cheap to experiment with. I used poster board 99 cents per sheet....four sheets for four ports....four bucks. Cardboard works too but the poster board rolled up tight and then 'unrolled' after it's in the existing port makes a tight fit.

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Adding a lot of dampening in the cabinet seemed to make the bass (to me) less punchy and more woolly.
My experience as well.
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Remember, when they are inside the speaker, the ports use up cabinet volume so the sound will not match if they are outside of the cabinet now.  Purchase one of the Parts Express analyzers for impedance and you will be able to see how the tuning affects the woofers based on port size, length and cabinet volume.

So your saying do a impedance sweep and then adjust the ports until both humps in the sweep are the same height.

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Good luck on the design.  

 

I would be considering adding some volume to a KLF 30 vs removing.  Since the ports are to the rear, you wouldn't notice the mid-range bleed through unless you specifically tested for it with everything else turned off.  The fact that they are in the back and minimal enclosure stuffing will tell you right there though sometimes that bleed through can make the speaker more appealing.

 

If you are dropping the size, you will be dropping the port size or making them longer.  If the ports are facing the floor then that will be helpful in removing any unwanted wind noise or mid output.  

 

You must be going to use these with a sub, correct?  The 30s don't get super deep as it is with their small enclosure.

 

I would be looking at larger enclosure with somewhat lowered tuning, and if you are doing a crossover, adding an 8" mid bass or possibly 2 6" to clean up the discontinuity between the mid horn and the woofers.  That would address the KLF 30's weak points.

They get a lot deeper if you remove the feet and put the cabinet directly on the floor.

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