Ever re-engineer a consumer level loudspeaker?

[KenM10759]

I had a thought (rare) and was wondering if this would be stupid or just plain crazy, or both.

Assume for a moment that I had bought a pair of KEF Q500 floor standing speakers for about 30% off list price. They're a 2-1/2 way crossover with a Uni-Q tweeter/midrange, one 5-1/4" woofer and two "Acoustic Bass Resonator" of that same size. No ports, just the 2 passive radiators.

Now one of the weaker areas of the Q series is the rather pedestrian quality crossover. My understanding is that it's a 1st order Linkwitz-Riley design, but I know absolutely nothing about crossovers. I own the KEF R500, which is a true 3-way with the same size drivers. It has two 5-1/4" woofers and is rear ported and I like them enough that I'm not messing with those.

What if I were to buy a pair of the same woofer used in the Q500 and replace one ABR in each with an actual woofer, and also upgrade the crossover to a 4th order LR? That would leave one ABR, or I could remove it and turn that into a port.

Would this require all kinds of testing equipment that I don't have to make it work? Is the potential there for a much improved speaker, or is it a waste of time? I have no interest in starting a complete DYI build, I'm just wondering if I could swap out a passive radiator for an actual woofer, put in a better crossover and have a better speaker.

A nuts idea or not?

 

[Dennis Murphy]

I had a thought (rare) and was wondering if this would be stupid or just plain crazy, or both.

Assume for a moment that I had bought a pair of KEF Q500 floor standing speakers for about 30% off list price. They're a 2-1/2 way crossover with a Uni-Q tweeter/midrange, one 5-1/4" woofer and two "Acoustic Bass Resonator" of that same size. No ports, just the 2 passive radiators.

Now one of the weaker areas of the Q series is the rather pedestrian quality crossover. My understanding is that it's a 1st order Linkwitz-Riley design, but I know absolutely nothing about crossovers. I own the KEF R500, which is a true 3-way with the same size drivers. It has two 5-1/4" woofers and is rear ported and I like them enough that I'm not messing with those.

What if I were to buy a pair of the same woofer used in the Q500 and replace one ABR in each with an actual woofer, and also upgrade the crossover to a 4th order LR? That would leave one ABR, or I could remove it and turn that into a port.

Would this require all kinds of testing equipment that I don't have to make it work? Is the potential there for a much improved speaker, or is it a waste of time? I have no interest in starting a complete DYI build, I'm just wondering if I could swap out a passive radiator for an actual woofer, put in a better crossover and have a better speaker.

A nuts idea or not?

Hmmmmmm I'm not following why you would want to mess up the bass tuning by eliminating one of the passive radiators and replacing it with a port. Not only wouldn't you get the tuning to match, but there wouldn't be any advantage even if you did. Linkwitz-Riley crossovers are even-order acoustic, where the drivers are all in phase with each other at the crossover frequency. It's hard to say what the KEF"s are. If they are like the R-100's, which just use a cap and a coil, then the resulting acoustical slopes could be most anything from 2nd order to 4th order depending on the natural roll-off characteristics of the drivers. But the bottom line is that redesigning a 2.5 speaker would be a bear, and would certainly require measuring equipment, design software, and a good bit of experience with both.

 

[KenM10759]

I was hoping you'd educate me Mr. Murphy!

I no NOTHING about crossovers and the only thing I know about assembled speakers is if I like the way the sound or not. In this case, I was just thinking there might be some way to make the Q500's I bought for my son sound a little closer to my own R500's. No surprise that it's not easy...or cheap.

Thanks for the reality check. I do appreciate it.

 

[Dennis Murphy]

I was hoping you'd educate me Mr. Murphy!

I no NOTHING about crossovers and the only thing I know about assembled speakers is if I like the way the sound or not. In this case, I was just thinking there might be some way to make the Q500's I bought for my son sound a little closer to my own R500's. No surprise that it's not easy...or cheap.

Thanks for the reality check. I do appreciate it.

I messed up my Q's and R's. I meant to say the Q100 used a cap and a coil. I don't know what the R series uses. Which is to say I don't know whether the differences you're hearing between the R500's and Q500's are due to the crossover, driver quality and driver configuration, or bass tuning. All I know is that 2.5's are really hard, and re-engineering any speaker would be a total crap shoot without the proper software and experience.

 

[KenM10759]

All I know about the crossover on the R500 is that it's a true 3-way and somewhere in a review I had read where the reviewer had peered inside it's a 4th order LR.

KEF has said the Q and R is priced so differently because the Uni-Q drivers have different surrounds and "other components". Obviously they sound different because of that, but also the cabinet size is slightly bigger in the R500 (taller) and is rear ported, no passive radiators, and the crossovers.

Yeah, I figured it would be a crap shoot to get a better crossover for the Q500, and add a woofer. Can I send the Q500's to you with a blank check? His birthday is Halloween, I just need them back by then.

 

[lovinthehd]

When I saw the title my first thought was what would Dennis say....lol. Lot of work to redesign a crossover or even remove and replace them with active components. You think you can out-do KEF with the same component/construction doesn't sound like a good bet.

 

[KenM10759]

LOL...no I don't think for one minute I could outdo KEF with the same components and construction. I *did* think for minute that since they cut costs with the Q500 by making it a 2-1/2 way that at the very least I might be able to improve it with a 3-way crossover of higher quality components.

Or Dennis could. I know, probably a waste of money. Better to just buy him a used pair of R500 but all his other speakers are Q series including Q300, Q200c and soon Q500. His rear speakers are the older gen iQ10, so the R300 will move to the back and replace those in his 7.1 system.

 

[lovinthehd]

LOL...no I don't think for one minute I could outdo KEF with the same components and construction. I *did* think for minute that since they cut costs with the Q500 by making it a 2-1/2 way that at the very least I might be able to improve it with a 3-way crossover of higher quality components.

Or Dennis could. I know, probably a waste of money. Better to just buy him a used pair of R500 but all his other speakers are Q series including Q300, Q200c and soon Q500. His rear speakers are the older gen iQ10, so the R300 will move to the back and replace those in his 7.1 system.

How about just upgrading your own stuff, then letting nature take its course and he upgrades his own setup trying to keep up with dad?

 

[KenM10759]

I've been planning to upgrade mine someday but I've only had it for about 10 months. During this time (spent reading and participating here and elsewhere) I've learned a fair bit, but also been to area hi-fi shops and heard so many better systems that I know what I have isn't the "end game."

My son (the younger one of two) has inherited much of what I upgraded from that ten months ago. Being that he's renovating his paternal grandparents home that he & his fiancé bought, money is tight for them and there are things he can't justify buying...so I do. He's NOT trying to keep up with me, he has a different focus: home theater. I'm more music/hi-fi oriented. I just want him to be happy with his surround system while he's busting his butt on the house and property. His fiancé is big on World Of Warcraft and also enjoys their system. Being motivated to buy a house (at market value) at age 25 is evidence to me that he's far more motivated than his two older siblings, as is his fiancé.

I love my children and will go to the ends of the earth to do things to make their lives happier. This is just a small part of it. We're in this together. He may get my R series stuff someday, no telling.

 

[PENG]

Ken, if you are curious enough, you could just try replacing the uniQ/mid range driver to find out if it sounds better already. If you do one speaker first, and it does not work out, at least you will end up with a spare driver for your 500s.

 

[Swerd]

Your idea of re-engineering your KEF speakers reminds me what I did about 10 years ago with some old JBL L-100 speakers. Fortunately, I live not too far away from Dennis Murphy, and he was interested in trying his hand with those speakers. Read about it here:
http://forums.audioholics.com/forums/threads/the-vintage-jbl-west-coast-sound-becomes-the….25014/

I learned two lessons from that. The first is what a big difference a well designed crossover makes. Of course, I was taking a large step going from early 1970s design methods to modern ones. Your KEFs might not be as bad to start with.

The second lesson was once you fix one problem, you identify another. The JBL 12" woofer used in those smallish ported cabinets really should be in much larger sealed cabinets. It created a large bass hump in the 60-80 Hz range that became much more noticeable once the new crossovers were in place. Only new cabinets can fix that, something I never did.

 

[KenM10759]

I believe the Uni-Q drivers in the R500 and Q500 are close enough to each other that swapping the cheaper one for the pricier one wouldn't improve the speaker nearly as much as it would to jump from a 2-1/2 to a 3 way crossover.

I'd love to have Dennis work on that, but don't think I could afford to have him do it unless there were such a good improvement that other Q500 owners would buy a crossover from him.

 

[Dennis Murphy]

I believe the Uni-Q drivers in the R500 and Q500 are close enough to each other that swapping the cheaper one for the pricier one wouldn't improve the speaker nearly as much as it would to jump from a 2-1/2 to a 3 way crossover.

I'd love to have Dennis work on that, but don't think I could afford to have him do it unless there were such a good improvement that other Q500 owners would buy a crossover from him.

I don't charge for work like that (except for parts if you have me build the boards). But it usually isn't logistically practical because I need to have one of the speakers here, and if they're large and you're far away from Washington, D.C., shipping can mount up. And most people don't have the original boxes or a safe substitute.