I live in the USA, the land of plenty. An occurrence such as Martin Logans at the local Goodwill is not unheard of; people here just throw away what has expired in their minds for whatever reason. A built cabinet can be a useful find, IF there's a way to "reverse engineer" it to suit a new and different driver set.
I put this here in Multi-Way because those are the most likely cabinets to be discarded. Infinitys by the side of the road...
Example #1. A pair of KEF Q floorstanders were picked up at a yard sale for $20. $20 is nothing compared to materials costs for wood, binding posts, grilles and fabrication thereof. Let's say both tweeters are out, it's a 6.5" driver - and I'd like to drop in a Tang Band or Mark Audio full range in place. What would be the assessment steps to verify if such drivers would "sound good" in the existing cabinet?
Example #2. A pair of Polk towers were picked up at a yard sale for $2. Likewise, $2 is nothing compared to materials costs for wood, etc etc. Let's say both tweeters are out, it's two 6.5" drivers - and I'd like to build a plate covering one driver cutout , again to drop in a Dayton or Audio Nirvana full range in place. What would be the assessment steps - this cab has multiple internal chambers with the reflex port firing downward at a plate which forms the base of the speaker.
I think it's just as skillful to successfully select a driver or drivers to match an existing cabinet, as it is to select a cabinet design to match an existing driver. Plus, this is a truly conservative approach, as sometimes such cabinets are in fine shape, but destined for the trash heap only because it's difficult to deal with the present situation - blown speaker, no replacement available.
Example #3, Radio Shack Linaium (?) speakers, $5 at a Goodwill outlet. Tweeters OK, woofers bad surrounds. Pretty sure can do better on the woofers than stock. Steps to assess such a metal cabinet to a current, for sale, quality driver?
Thanks for any discussion on this topic. Can involve measurement equipment.
I put this here in Multi-Way because those are the most likely cabinets to be discarded. Infinitys by the side of the road...
Example #1. A pair of KEF Q floorstanders were picked up at a yard sale for $20. $20 is nothing compared to materials costs for wood, binding posts, grilles and fabrication thereof. Let's say both tweeters are out, it's a 6.5" driver - and I'd like to drop in a Tang Band or Mark Audio full range in place. What would be the assessment steps to verify if such drivers would "sound good" in the existing cabinet?
Example #2. A pair of Polk towers were picked up at a yard sale for $2. Likewise, $2 is nothing compared to materials costs for wood, etc etc. Let's say both tweeters are out, it's two 6.5" drivers - and I'd like to build a plate covering one driver cutout , again to drop in a Dayton or Audio Nirvana full range in place. What would be the assessment steps - this cab has multiple internal chambers with the reflex port firing downward at a plate which forms the base of the speaker.
I think it's just as skillful to successfully select a driver or drivers to match an existing cabinet, as it is to select a cabinet design to match an existing driver. Plus, this is a truly conservative approach, as sometimes such cabinets are in fine shape, but destined for the trash heap only because it's difficult to deal with the present situation - blown speaker, no replacement available.
Example #3, Radio Shack Linaium (?) speakers, $5 at a Goodwill outlet. Tweeters OK, woofers bad surrounds. Pretty sure can do better on the woofers than stock. Steps to assess such a metal cabinet to a current, for sale, quality driver?
Thanks for any discussion on this topic. Can involve measurement equipment.
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There is not much to get philosophical about in repurposing a cabinet to a different speaker unit. To make it sound good you have the problem of creating a crossover filter which you can probably achieve by modifying an existing one with a couple of parts added to or subtracted from the original one. Then you need the information on what kind of an enclosure and what volume your new driver needs to be placed in to take the advantage of its bass potential. Knowing that you will immediately realize what to do with your "good find" cabinets. Any excess chambers should be sealed off and any lacking should be created.
There is always a way to a solution, we just may not be aware of it.
There is always a way to a solution, we just may not be aware of it.
I tried doing this with a set of Infinity PF-Rs.
Restoring Infinity Preludes
IMHO, it was a waste of time and money.
The main problem that I had, was that it's impossible to get replacement drivers to fit properly. For instance, I invested around 4-8 hours doing the following:
1) removing the existing drivers
2) measuring the drivers
3) finding similar replacements from Parts Express
4) waiting a week for them to arrive
5) Only to find that there's no practical way to get them to fit in the cabinet.
Basically a difference of five millimeters is going to torpedo the project. If the holes are too big, you have to come up with some kind of baffle to fix that, which will look terrible. If the holes are too small you might be able to make it look OK by routing out bigger holes.
Time is money; even if I value my time at $20 an hour, that's still about $100-$200 in time spent.
For that much money, you can get a Behringer B2030A that outperforms all those speakers listed, for about that much money.
I like to DIY stuff that's unobtanium. For instance, nobody is selling a small inexpensive Unity horn: Metlako: A Small, Affordable Two-Way Unity Waveguide
On a side note, I *highly* recommend buying rotted out speakers and removing the crossovers. For instance, I paid something like $100-$200 for the Infinity PF-Rs. I wound up throwing everything away, but the crossovers alone have about $100 worth of parts in them. Inductors in particular.
Restoring Infinity Preludes
IMHO, it was a waste of time and money.
The main problem that I had, was that it's impossible to get replacement drivers to fit properly. For instance, I invested around 4-8 hours doing the following:
1) removing the existing drivers
2) measuring the drivers
3) finding similar replacements from Parts Express
4) waiting a week for them to arrive
5) Only to find that there's no practical way to get them to fit in the cabinet.
Basically a difference of five millimeters is going to torpedo the project. If the holes are too big, you have to come up with some kind of baffle to fix that, which will look terrible. If the holes are too small you might be able to make it look OK by routing out bigger holes.
Time is money; even if I value my time at $20 an hour, that's still about $100-$200 in time spent.
For that much money, you can get a Behringer B2030A that outperforms all those speakers listed, for about that much money.
I like to DIY stuff that's unobtanium. For instance, nobody is selling a small inexpensive Unity horn: Metlako: A Small, Affordable Two-Way Unity Waveguide
On a side note, I *highly* recommend buying rotted out speakers and removing the crossovers. For instance, I paid something like $100-$200 for the Infinity PF-Rs. I wound up throwing everything away, but the crossovers alone have about $100 worth of parts in them. Inductors in particular.
@Lojzek; Yeah, my proposal was to use some full range driver in place of, which would eliminate the crossover re-engineering part of the idea. But point taken in a multiway - to - multiway cabinet repurpose.
@ Patrick, Certainly some projects I see here end up being a waste of time and money, what with folks putting their hand-built cabinet failures on the burn pile! (I never heard of a Behringer B2030A until reading your post(s) - thanks for that suggestion)
I'm thinking of what would you do in more detail in your step 2) Measure the drivers; assuming there's at least one functional, as is the case in my current situation. Ascertain Fs, try to match at least that parameter? Force Fs to be lower by adding weight - to match a candidate driver - see what that does regarding a measured acoustic output before purchase? Force Fs to be higher by stiffening the suspension (with a coating) - again to match a candidate driver - see what that does before purchase? See what various levels of cabinet stuffing does to help match it to the driver Fs (force cabinet volume smaller)?
I realize this is quite simplistic, but there has to be some point to start up any knowledge of what to do. Thanks.
@ Patrick, Certainly some projects I see here end up being a waste of time and money, what with folks putting their hand-built cabinet failures on the burn pile! (I never heard of a Behringer B2030A until reading your post(s) - thanks for that suggestion)
I'm thinking of what would you do in more detail in your step 2) Measure the drivers; assuming there's at least one functional, as is the case in my current situation. Ascertain Fs, try to match at least that parameter? Force Fs to be lower by adding weight - to match a candidate driver - see what that does regarding a measured acoustic output before purchase? Force Fs to be higher by stiffening the suspension (with a coating) - again to match a candidate driver - see what that does before purchase? See what various levels of cabinet stuffing does to help match it to the driver Fs (force cabinet volume smaller)?
I realize this is quite simplistic, but there has to be some point to start up any knowledge of what to do. Thanks.
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There is, to the first approximation: when Vb = Vas and Fb = Fs, then Qts' is ~0.403 and F3 = Fb, i.e. max flat vented alignment.
Fs range where Fs = Fb = F3 can be found based on box efficiency [attached].
A reasonable vent area [Av] is effective piston area [Sd]/3 and use an on-line calculator or simming program to find its length for an Fs/whatever tuning.
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
GM
Fs range where Fs = Fb = F3 can be found based on box efficiency [attached].
A reasonable vent area [Av] is effective piston area [Sd]/3 and use an on-line calculator or simming program to find its length for an Fs/whatever tuning.
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
GM
Attachments
Quite a few times I have just glued/screwed on a new front baffle. Much easier than dealing with the existing holes.
100%
I picked up some old large technics speakers recently just for the enclosure because at $10 that was much cheaper than it would cost to make from scratch myself, they could be easily improved with bracing and stuffing.
Turned out they'd had a modern 10" replacement woofer installed, so with a little tlc and dsp they are now providing an excellent platform for experiments.
I've got a few old cabs now, bargains for us diyers, especially the large ones, stuff the port, dsp, done.
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