JVC SK15A 15" 3 way box rebuild/redesign (questions)

[AddamR]

I have a pair of vintage JVC SK15A speakers that I picked up for $20. I was using them for about a year, 2 years ago, but the boxes are a little swollen from moisture damage, they were previously mothballed in someone's garage for a couple of decades.

The drivers are fine and perform exceptionally well, hence my idea to rebuild the boxes, into a more modern design.

I've had experience in past of building and designing speakers from driver values. This project won't require any of those calculations.

I have two options, rebuild same spec (volume and dimensions), so they are close as possible to the original, with a modern touch.

Or, my preference is to have a narrow/deep enclosure, with a side firing woofer and have the mid tweeter array flipped to the vertical.

Questions to the folk with much more knowledge than me - will this affect the original design at all? Will crossovers need to be redone? Baffle considerations?

Boxes are currently ~600x420x290 (external).
I want to rotate that to ~250x450x1200 (external)

Keeping the original box volume and mid tweeter placement as is, just vertical. Extra height will be used for a base filled with weight.

I'll be using 25mm MDF, as I have 3 sheets of 900x1800 on hand (office partitions, repurposed, they cost me $5 each and weight a ton)

Thoughts/advice?

Cheers

Adam

 

[thewas]

I will be frank with you, from acoustic point of view such "Kabuki" loudspeakers are a mess so even with a better crossover they will never become great, but since you like their sound I would just keep the original crossover, maybe replacing the electrolytic capacitors with fresh ones, everything else would be just too much effort for a questionable result.

 

[AddamR]

That's the type of response I like. How about I change my mind to a vifa 6.5" 3 way ground up design. I'm trying to do stuff with stock on hand and not go out and buy *more stuff*

 

[fpitas]

The usual advice is to build a kit and get some experience that way before you dive into speaker design. There's a lot to it, especially if you aren't already an engineer.

 

[AddamR]

I've built a Jaycar (Australia) MTM 5" kit a few decades ago. Have built and designed a 10" sub from ground up.

The Vifas I picked up in an old speaker cabinet at second hand shop, someone had an idea just to shove drivers in a box and at the time, the Vifas where still worth something, so I got an absolute bargain, with 4 x PJ-W17s and 4 x D25 tweeters.

The 5" MTM and Sub were onsold years ago.

Thanks for the term 'kabuki', just reading up on that now. Not a whole lotta love going on there.

I'm not an engineer, I'm autistic, so behave like one LOL.

I do have knowledge though and a couple of quite technical books on box design and implementation.

I'm a DIYer (mostly) and prefer the 'build yourself model', not just for HiFi projects.

Currently don't have a decent set of speakers (apart from a small set of Krix Brix and the Vifa 6.5s I've just shoved into a 1 cu ft ported box from the rear set of a Pye4 set of speakers, as the cutout/port where about right and the do OK as a below 120hz sub, for the time being)

 

[AddamR]

The usual advice is to build a kit and get some experience that way before you dive into speaker design. There's a lot to it, especially if you aren't already an engineer.

FWIW, I used these SK15s with a JVC VR5515X amplifier (no longer with us, sadly) and the match seemed appropriate. I've never tested these 'kabuki' speakers with any other type of amplification.

 

[fpitas]

FWIW, I used these SK15s with a JVC VR5515X amplifier (no longer with us, sadly) and the match seemed appropriate. I've never tested these 'kabuki' speakers with any other type of amplification.

I hope I'm not ruffling any feathers, but that "design" of speaker was only meant for visual impression. No acoustic science was involved, and the cheapest drivers were used.

 

[AddamR]

I hope I'm not ruffling any feathers, but that "design" of speaker was only meant for visual impression. No acoustic science was involved, and the cheapest drivers were used.

Not at all ruffled. These are the answers I'm seeking. It's already a dead project. I've just done a quick read up on kabuki speakers. Since I was running them with a JVC amp of the period, I must have been fooled into the marketing hype of the 70s. My room is also not the best, in terms of size and shape.

 

[fpitas]

Not at all ruffled. These are the answers I'm seeking. It's already a dead project. I've just done a quick read up on kabuki speakers. Since I was running them with a JVC amp of the period, I must have been fooled into the marketing hype of the 70s. My room is also not the best, in terms of size and shape.

The good news is, the amp is probably just fine.

 

[AddamR]

The good news is, the amp is probably just fine.

Umm, no. Radio section failed (no big deal) then everything else, including channels went. Last straw was puffs of cap smoke and it's now in a crate with another vintage amp, in pieces. I'll maybe look at it later...it was a good unit until it wasn't.

 

[fpitas]

Umm, no. Radio section failed (no big deal) then everything else, including channels went. Last straw was puffs of cap smoke and it's now in a crate with another vintage amp, in pieces. I'll maybe look at it later...it was a good unit until it wasn't.

Well then, the good news is that amps are better and cheaper these days.

 

[fpitas]

You may be interested in this thread: https://www.audiosciencereview.com/forum/index.php?threads/end-game-diy-loudspeakers.40519/

One big takeaway is that DIY seldom saves money, and takes a lot of time. Doing it right takes most people years. But if you want to learn a lot of engineering, including math, it's a great hobby.

 

[AddamR]

Well then, the good news is that amps are better and cheaper these days.

You may be interested in this thread: https://www.audiosciencereview.com/forum/index.php?threads/end-game-diy-loudspeakers.40519/

One big takeaway is that DIY seldom saves money, and takes a lot of time. Doing it right takes most people years. But if you want to learn a lot of engineering, including math, it's a great hobby.

Regarding DIY, I've just ejected myself from that nightmare, regarding Amps and surround systems. Spent a year shopping, designing, buying, building and ultimately pulling my hair out, before buying ready made amps and just staying with stereo, as I don't do a whole lot that needs surround sound.

 

[AddamR]

You may be interested in this thread: https://www.audiosciencereview.com/forum/index.php?threads/end-game-diy-loudspeakers.40519/

One big takeaway is that DIY seldom saves money, and takes a lot of time. Doing it right takes most people years. But if you want to learn a lot of engineering, including math, it's a great hobby.

I'm in my 50s, DIY has been a part of me forever, not just speakers and electronics, it's been a way of life, sort of. But lately, I'm slowly turning to ready made gear. Have had really good experience with ChiFi amps and spent time researching chips/brands and suitable units.

Settled on TIs TPA3255 and Fosi Audio's implementation in thier products. Sound is very good, I'm just lacking the right pair of speakers to exploit that sound to the max.

 

[AddamR]

Well then, the good news is that amps are better and cheaper these days.

I'm also running an SMSL D-6 DAC, first time using a DAC and I can say, I was missing out on a whole lot.

 

[fpitas]

I'm also running an SMSL D-6 DAC, first time using a DAC and I can say, I was missing out on a whole lot.

Yeah, around here we consider electronics to be a solved problem. Speakers are the tough and expensive part.

 

[AddamR]

Well, good news is, that I've got at least a dozen pair or more of vintage Magnavox drivers (Aussie made) of various sizes and they sell for a decent penny online.

As for the chipboard boxes they came in...easily deconstructed to fit in the bin.

 

[DVDdoug]

The new build should sound very similar as along as the box volume and port dimensions are the same.

Something you might consider - Get a Speaker Tester to measure the Theile/Small parameters of the woofer. Then with speaker design software (I use WinISD) you can model bass performance and possibly change/improve the tuning. Since the speaker is "old" it may not have been "computer optimized" or the manufacturer's idea of "optimum" may be different from yours, or they may have made different compromises. You may end-up wanting a bigger box and/or a sealed box, or maybe just different port dimensions.

And although you probably have no intention of replacing the woofers, you can also model the performance with a different woofers. (And of course you can look-up the Theile/Small parameters for a new woofer so you don't have to have it in your hands to test it.)

 

[AddamR]

The new build should sound very similar as along as the box volume and port dimensions are the same.

Something you might consider - Get a Speaker Tester to measure the Theile/Small parameters of the woofer. Then with speaker design software (I use WinISD) you can model bass performance and possibly change/improve the tuning. Since the speaker is "old" it may not have been "computer optimized" or the manufacturer's idea of "optimum" may be different from yours, or they may have made different compromises. You may end-up wanting a bigger box and/or a sealed box, or maybe just different port dimensions.

And although you probably have no intention of replacing the woofers, you can also model the performance with a different woofers. (And of course you can look-up the Theile/Small parameters for a new woofer so you don't have to have it in your hands to test it.)

Thanks for the link, that speaker tester looks interesting and not a bad price. Would be a good investment, as I've got a lot of speakers floating about, most with no box/home and unknown characteristics.

I think the 'issue' with these kabuki speakers, is the over use of the mids and tweeters, as described here and elsewhere online.

That 15" woofer, in a box that small, albeit ported, mustn't get below 70-80hz, still have an idea to use just the woofer, in a new designed 3 or 4 way.

As well as the Vifas I have, also have a couple pairs of 4" Wharfdale and Jensen drivers I could repurpose.

In line with diy and *trying* to keep costs low, I'm reusing what I've got on hand and avoiding buying more of the same/similar I've already on hand.

 

[AddamR]

The new build should sound very similar as along as the box volume and port dimensions are the same.

Something you might consider - Get a Speaker Tester to measure the Theile/Small parameters of the woofer. Then with speaker design software (I use WinISD) you can model bass performance and possibly change/improve the tuning. Since the speaker is "old" it may not have been "computer optimized" or the manufacturer's idea of "optimum" may be different from yours, or they may have made different compromises. You may end-up wanting a bigger box and/or a sealed box, or maybe just different port dimensions.

And although you probably have no intention of replacing the woofers, you can also model the performance with a different woofers. (And of course you can look-up the Theile/Small parameters for a new woofer so you don't have to have it in your hands to test it.)

As far as sound goes, I realise they are not considered 'great' speakers, if I did pursue a rebuild. Box volume and ports would be identical, the question was 'if' I changed the geometry to side firing woofer and vertical mid/tweeter array, to reduce the front facing footprint, would that mess it all up or is it as has already been said - 'there's no science that went into these designs' and therefore it wouldn't make a difference?