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Multi-Way Conventional loudspeakers with crossovers

DIY speaker upgrade suggestions
DIY speaker upgrade suggestions
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Old 13th February 2006, 01:28 AM   #1
Sparhawk is offline Sparhawk
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Question DIY speaker upgrade suggestions

I've been away from the forum for a couple years, so this is my first post in quite a while.

I have a pair of speakers that I built when I was about 12 or 13 years old, which I'm thinking about upgrading. I had stored them at my parents' house for many years, and now that I have them back, I've realized a couple things:

1) They sound horrible!
2) I'm reluctant to get rid of them, since they have some nostalgic value.

The parts are all vintage Radio Shack: 12" poly woofers, 2" (approx) soft-dome midranges, and Motorola piezo horn tweeters. The crossovers are Radio Shack "universal" first-order, 3-way units. The cabinets are 3/4" MDF with a nice red oak veneer.

The soft-dome midrange is actually not too bad, but the piezo tweeters are terrible.

The main problem is the crossover. Due to the limited LF extension on the midrange, the crossover frequency is way too high. That fact, combined with the 6dB/oct slope, results in the 12" woofers having significant output up to approx. 1.6KHz! They also have a peak around 125Hz which I think may be due to the fact that the cabinet doesn't have enough damping material.

My plan is to replace the midranges with 5.5" paper cone drivers, and the tweeters with 1" textile domes.

I'm thinking of going to a biamped setup using a 4th-order LR electronic crossover around 250Hz, and then using a 2nd-order passive crossover between the midrange and tweeter.

I've been looking at two possibilites for the replacement drivers:

1) Vifa PL14WJ09 5.25" midrange and PL27TG05 1" tweeter
2) Seas H1262 5" midrange and H1318 tweeter

I'm not sure whether to attempt the passive crossover design myself, or have Madisound do it.

Any opinions on the choice of drivers, or whether this is even a worthwhile project? Are there other inherent flaws that I'm missing, like time alignment, or diffraction effects?

BTW, I'm also planning to add significant internal bracing and additional damping to the cabinets.

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Old 13th February 2006, 08:23 AM   #2
Curmudgeon is offline Curmudgeon  United States
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Based solely on the curves, and not personal experience, I'd choose the Seas units.

I've had Madisound do 2 crossovers, for projects for friends. Both turned out well, with a little value tweaking for final voicing.

I don't think you need a 4th order between the woofer and the mid; depending on how well the woofer behaves, you might do fine with 2nd order. That's usually the easier crossover.

If you have the second amp already biamping is fine; if not, I'd try a passive crossover first; significantly less expensive, and can be all that you need in terms of quality.

I'd suggest Mills resistors, and sonic craft polypropylenes, or Relcap Multi caps polypopylenes.
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Old 13th February 2006, 05:26 PM   #3
Sparhawk is offline Sparhawk
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Thanks for the suggestions.

I was originally looking at the Seas H522, but it is discontinued, and apparently now sold out at Madisound.

The idea for the active crossover is mainly just because I'd like to build one anyway. I've been meaning to build Joe's tube-buffered gainclone since he first introduced it, so I thought I would just add a couple more channels. It might actually be cheaper than buying high quality parts (and maybe a design) for a passive crossover, since I have most of the parts on hand already.
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Old 17th February 2006, 12:15 AM   #4
Sparhawk is offline Sparhawk
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Any more comments on these two sets of drivers? Or whether this upgrade is worthwhile?



Another post also led me to the Peerless 830882 5.5" midrange, which looks like another good possibility in the same price range. But it looks like the crossover could be interesting, with that HF rise that starts around 2K.
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