Need advice rebuilding Klipsch KF28

[Zedisdead]

I'm going to be rebuilding a set of Klipsch KF28 towers with quality drivers, I just need to know if these will work. The crossover point will be at 1800 hz. My main concern is how the Ωs will stack. I'm using a Integra DTR 30.4 which will work down to 3 Ω, 240W Channel 3 Ω, 210W Channel 4 Ω, 120W Channel 8 Ω, I'm wanting to get 4-6 Ω so I can easily resale these later down the road when I plunge deeper into the rabbit hole. Also any recommendations on a reputable 3d printing site as I will need to have a plate made with mount holes and a recessed cutout for the tweeter, I plan to sand and epoxy the plate to give it the appearance of a injection molded plastic piece.

Dayton Audio RS225-8 8" Reference Woofer

Nominal Diameter
8"

Power Handling (RMS)
80 Watts

Power Handling (max)
160 Watts

Impedance
8 ohms

Frequency Response
28 to 2,400 Hz

Sensitivity
86.8 dB 2.83V/1m

Voice Coil Diameter
1.5"

Sealed Volume
0.45 ft.³
Sealed F3
63 Hz

Vented Volume
1.26 ft.³

Vented F3
36 Hz

Peerless DA25TX00-08 1" Corundum Dome Tweeter

Tweeter Type
Corundum Dome
Cone / Dome Diameter
1"

Impedance
8 ohms

Power Handling (RMS)
100 Watts

Frequency Response
1,000 to 40,000 Hz

Sensitivity
88.7 dB 1W/1m

 

[Swerd]

The short answer to your question is "No, don't try that". It is highly unlikely to work.

Your post does deserve a longer and more detailed answer. I'll try a brief outline.

1. If I read you correctly, you want to use a Klipsch KF28 cabinet and replace the drivers and crossovers. Correct? Replacing the Klipsch woofer with most any other 8" woofer will probably not work in that cabinet unless it happens to require the same volume and port size to have a good bass response. The chances of that happening are slim to none. The way DIY speaker building is done is to choose the woofer first, and then calculate the dimensions of a suitable cabinet. You're proposing to do this backwards.
   
   Parts Express claims this woofer can go as low as 28 Hz. They also say the optimum cabinet size (determined using BassBox 6 Pro High Fidelity) is with a sealed cabinet of 0.45 ft.³, with an F3 of 63 Hz. In a vented cabinet of 1.26 ft.³ volume, the F3 would be 36 Hz. What is the interior volume of your KF28 cabinet?
   
   Explaining this in enough detail to allow you to understand it is not easy to do on a forum like this. Buy or borrow Speaker Building 201 by Ray Alden and read the first three chapters.
   
   
2. Your idea of combining an 8" woofer with a 1" dome tweeter could result in a speaker that has a gaping hole in it's mid-range sound. That woofer, in theory can produce a flat frequency response as high as 2,000 Hz. See this graph. But that is an upper limit. PE does show off-axis measurements, where the microphone was moved off to the side, away from directly in front of the driver. To have a better idea of what crossover frequency to choose, you must also know how well that woofer disperses sound off-axis while in your cabinet. PE doesn't tell you this because it must be measured in the cabinet you intend to use. Their graph tells me that a crossover frequency of 1800 Hz could easily be too high for that woofer.
   
   Parts Express says it has a usable frequency range as high as 2400 Hz, but I wouldn't try running it as a 2-way with a typical 1" dome tweeter crossed any where near that high. Choose a crossover frequency based on where the woofer can produce sound that falls about 3 dB lower that it does at lower frequencies. Larger woofers, loose their off-axis response at lower frequencies than smaller woofers. At 1800 Hz this otherwise good woofer is probably beaming – producing useful sound only on-axis, directly in front of the speaker. When combined with a 1" dome tweeter, this speaker will, at best, have a noticeably narrow sweet spot.
   
   Also, that graph might be much too optimistic. That woofer has an aluminum cone. The graph shows only some mild looking break-up peaks at very high frequencies, beginning at 3 kHz and higher. That is unlike any other 8" aluminum woofer I've known. Compare it's frequency response curve to that of a good aluminum 8" Seas woofer, the L22RN4X/P. I wouldn't plan on using that woofer above 600 to 800 Hz. It doesn't make sense that the Dayton woofer could be that different. If you cross that woofer at 1800 Hz, you run the risk of hearing harsh and ugly sounding break-up noise unless it's played at low volume.
   
   
3. The Peerless tweeter you chose looks good on paper. It's sensitivity of 88.7 dB is close to that of the woofer, 86.8 dB. The tweeter's resonance frequency (Fs) is 633 Hz. A simple rule of thumb has it that if you triple this value, it probably can be a useful crossover frequency. That's 1900 Hz, not bad. But you also have to measure this tweeter when mounted in your cabinet, as cabinet width and tweeter manufacturing variations can and do make big differences.

I think I'll stop here.

 

[Pogre]

I would think an 8 ohm speaker would be easier to sell than 4 or 6...

 

[Zedisdead]

Swerd thanks for the write up I appreciate it. The interior volume is 2.79 so that's pretty close considering there'll be two of them in there right or am i missing something? I was planning on using the existing crossover which is at 1800hz. I would of imagined that would of worked good for this combo considering it's 600 hz below what the woofer is rated for and 800 above what the tweeter is rated for. I thought that might have been a safe buffer to allow the woofers and tweeters to blend together without v shaped sound.

What makes you think those will break up bad at 1800hz. One of the things I thought of when I saw that woofer you posted was that it was made for a 3 way speaker. The biggest concern I have atm is how to calculate what my final ohms will be.

I do intend to abuse this setup and having the woofers breaking up during songs doesn't sound too pleasurable. Before the tweeters started to show signs of wear I would crank them to their limit regularly for the past 3 years, it's actually amazing they lasted this long.

Pogre, I meant as that's what I would be willing to live with, with a decent chance of a somewhat quick resale later down the road.

 

[Swerd]

The interior volume is 2.79 so that's pretty close considering there'll be two of them in there right or am i missing something?

That volume of 2.79 ft³ is what works for the Klipsch 8" woofers that were in there. Two Dayton RS-225 woofers need 2.52 ft³. Not close enough. It will sound, but won't sound good. You never mentioned the diameter and length of the KF28 port. That matters too. Getting the cabinet volume and port dimensions right are what make a speaker's bass sound good. Why bother doing a rebuild when you're only guessing that it might be good enough?

I was planning on using the existing crossover which is at 1800hz. I would of imagined that would of worked good for this combo considering it's 600 hz below what the woofer is rated for and 800 above what the tweeter is rated for. I thought that might have been a safe buffer to allow the woofers and tweeters to blend together without v shaped sound.

What makes you think those will break up bad at 1800hz. One of the things I thought of when I saw that woofer you posted was that it was made for a 3 way speaker.

I'd bet the mortgage that those RS-225 woofers can't produce listenable sound at 2400 Hz or even 1800 Hz. I can't think of a metal 8" woofer that can. Let's say the frequency response info published by Parts Express is highly optimistic. It's simply too smooth looking to be true. Parts Express isn't the only company that does this. I linked that 8" Seas woofer because their products are very good, and they are known to publish honest data.

The biggest concern I have atm is how to calculate what my final ohms will be.

You don't calculate a speaker's impedance, you measure it.

Two Dayton RS-225s wired in parallel with each other will have a nominal impedance of 4 ohms. But as you can see with the blue trace below, impedance of one RS-225 changes with frequency.

When you mount a woofer inside a cabinet, with a port vent, this also changes impedance. The overall interior volume can alter the impedance in the bass frequencies. Is it still OK? Who knows? That's why we measure these things.

As an example, below is a measured impedance curve of a 2-way tower speaker, with two smaller woofers and a dome tweeter, a B&W 684 S2. There is no way to calculate that. It has to be measured.

 

[Zedisdead]

Well it's appearing as if these woofers are going to be a no go. Would it be a bad idea to epoxy pieces of mdf into the enclosure to get it to match which ever drivers I end up getting? Any recommendations on some woofers that I could use if shrinking the internal volume idea works out, no more than a 100 a piece.

I like the idea of building a enclosure but I also know I would end up obsessing over the final look of it thus I'd wind up using 2 part automotive ultra high gloss clear coat on top of a pearl black and mindlessly sand for hours and hours till I got a orange peel free mirror finish. Hell that'd be something I might do but only when I get some serious money for top of the line drivers.

 

[TLS Guy]

What I don't understand is why you want to change the drivers.

In any event your plan is doomed to total failure. Reverse engineering a speaker as you propose invariably results in audio cacophony.

You certainly can never use a crossover except for the drivers it was specifically designed for.

Crossovers have to be designed with great skill for the impedance, acoustic responses and sensitivity of the drivers.

Cabinet volume and port tuning, have to precisely match the Thiel/Small parameters of the drivers.

By all means get into DIY speaker building but not this way.

Learn how to model boxes and tuning. Learn the art of driver selection and then probably the most difficult of all the art of crossover design.

So if you want to learn this art, there are no short cuts. It is very rewarding and many DIY enthusiasts have designed and built fine speakers.

Unfortunately you are stating off completely on the wrong foot.

I have taken a look at your driver combination, and there is NO passive crossover solution for the combination of drivers you have selected. The sensitivity of those two drivers will be 93 db, as you gain 3 db for there being two drivers, and another 3 db because you have halved the impedance. Your tweeter has fairly low sensitivity at 88 db. You can not pad down woofers.

 

[Zedisdead]

The tweeters are starting to go so I figured might as well upgrade everything but it's becoming apparent this is a bad idea that's probably going to lead to regret and grief.

 

[-Jim-]

I'd try to source new tweeters and back off on the volume knob to prevent clipping so the woofers remain viable.

 

[TLS Guy]

The tweeters are starting to go so I figured might as well upgrade everything but it's becoming apparent this is a bad idea that's probably going to lead to regret and grief.

New tweeters for your speakers are widely available.

 

[Pogre]

Well it's appearing as if these woofers are going to be a no go. Would it be a bad idea to epoxy pieces of mdf into the enclosure to get it to match which ever drivers I end up getting? Any recommendations on some woofers that I could use if shrinking the internal volume idea works out, no more than a 100 a piece.

I like the idea of building a enclosure but I also know I would end up obsessing over the final look of it thus I'd wind up using 2 part automotive ultra high gloss clear coat on top of a pearl black and mindlessly sand for hours and hours till I got a orange peel free mirror finish. Hell that'd be something I might do but only when I get some serious money for top of the line drivers.

Sounds like you have some good finishing skills. I learned a lot posting over here and one of the biggest rules of thumb when it comes to speakers is "if it works, leave it alone". A lot of science and artistry goes into designing speakers. Every part, cabinet, crossover and drivers are all carefully selected, modeled and tested to work together. Changing one parameter in anything usually results in crap performance

One thing that has piqued my interest are transmission line speakers. These kits, TriTrix and Solstice look intriguing to me (thanks @lovinthehd for the links) and someone with your finishing skills could really produce a beautiful end product that sounds incredible. If you're interested in building a set of speakers I think cutting your teeth on a proven design would be a great learning experience.

 

[highfigh]

I'm going to be rebuilding a set of Klipsch KF28 towers with quality drivers, I just need to know if these will work. The crossover point will be at 1800 hz. My main concern is how the Ωs will stack. I'm using a Integra DTR 30.4 which will work down to 3 Ω, 240W Channel 3 Ω, 210W Channel 4 Ω, 120W Channel 8 Ω, I'm wanting to get 4-6 Ω so I can easily resale these later down the road when I plunge deeper into the rabbit hole. Also any recommendations on a reputable 3d printing site as I will need to have a plate made with mount holes and a recessed cutout for the tweeter, I plan to sand and epoxy the plate to give it the appearance of a injection molded plastic piece.

Think about what you're proposing- whatever it is that you liked about the Klipsch speakers, you won't have that if you replace everything. It's not possible, unless by coincidence. Changing from a wave guide to a dome tweeter will never sound the same. I googled that model and found them on ebay- $160.

 

[Kvn_Walker]

OP, I had similar questions a while back (bought a pair of Advent Heritage towers that didn't have woofers) and the consensus was the same... build or buy. Putting drivers that aren't made for the enclosure might give you a particular sound, but it won't be optimal.

 

[Zedisdead]

Sounds like you have some good finishing skills. I learned a lot posting over here and one of the biggest rules of thumb when it comes to speakers is "if it works, leave it alone". A lot of science and artistry goes into designing speakers. Every part, cabinet, crossover and drivers are all carefully selected, modeled and tested to work together. Changing one parameter in anything usually results in crap performance

One thing that has piqued my interest are transmission line speakers. These kits, TriTrix and Solstice look intriguing to me (thanks @lovinthehd for the links) and someone with your finishing skills could really produce a beautiful end product that sounds incredible. If you're interested in building a set of speakers I think cutting your teeth on a proven design would be a great learning experience.

I learned to do body work growing up around some old mechanics who liked cheap labor, 5$ a hour to do body work and other odds n ends, back in the mid to late 2000s was a hell of a deal for them and actually for me in a sense learning some skills. I intended to use that knowledge to get into a high end body shop but my interest changed.

Transmission line designs have always been pretty interesting to me but I never actually took the time to learn the mechanics of them.

i think I might pull the trigger on a kit in the not to distant future and just use OEM replacement tweeter's for now.

Think about what you're proposing- whatever it is that you liked about the Klipsch speakers, you won't have that if you replace everything. It's not possible, unless by coincidence. Changing from a wave guide to a dome tweeter will never sound the same. I googled that model and found them on ebay- $160.

I really like the forwardness, high efficiency, and high output of the klipsch. I wasn't looking to replicate the sound but have overall improved sound