Installing Crossover for Pioneer S-HF21-LR

[bennattj]

I'll put my question up front and backstory is below the schematic.

Do you think I'd get an improvement if I were to install a proper crossover into all eight of these speakers? (not really asking about is it "worth it" since I think I know the answer to that based on the cost and labor)

There was a previous thread on this back in 2008: pioneer s-hf21-lr crossover mod? which I believe was simply asking about the varistor in the "crossover". Which someone finally concluded "We might know what it is, but we don't currently know what it does."

Well the schematic answers the question: it's a varistor--basically a circuit breaker for the driver (when it gets too much current the temperature rises and the resistance spikes to effectively cutoff the driver). In other words there is no low-pass filter for the woofer. So the woofer is full range with a super tweeter crossed over at ~13kHz (the near inaudible range).

Looking at Parts Express, and my need for 8 of these, I'm basically pinned to a combination of: 3.3 micro-farad cap (~6kHz) and 0.20 mH inductor (closer to 6.5kHz).

Questions:
1. Can these tweeters, originally crossed over at 13kHz, even handle that low of frequencies?
2. How might that change the impedance of the speaker? (could it drop to 4-ohms, which would be a problem for me)
3. Could this improve sound clarity?
4. Any measurements I could (try to) take to quantify the change before and after if I do try?


Back story:

I recently got a really wild idea when I got my two pairs of Pioneer HF21's back from a friend who couldn't use them (turns out two had the tweeter broken off, two cabinets weren't in great shape, and one woofer was dead).

After pairing up two of them with some old (super cheap) Aiwa speakers from a 90s stereo and being super impressed with the sound, I decided to at least try two pairs of the Pioneers. That was actually quite impressive on its own so naturally, I thought to myself, what if I could double it?

So here it is, doubled (took me a bit to find all of these on ebay, but was able to keep the total speaker cost under $200):

right set, then another set of 4 on the left
two pairs, each pair wired in parallel (theoretically making a 4-ohm load) <-- with my custom made speaker wire
Fosi P4 into an RCA splitter, then each amp handles two of each channel

 

[leesonic]

Do you think I'd get an improvement if I were to install a proper crossover into all eight of these speakers?

It all depends on how you define a "proper crossover"? One might argue, a single 1.5uF cap for the tweeter, and running the woofer full range might not be considered a "proper crossover". However, without even having to think hard about it, two of my own speakers have exactly the same simple crossovers, namely my Infinity 3000 and JBL-L100. Even though these are both 3-way speakers, they still have a woofer running full range, and just a single cap for the midrange and tweeter.

Since you are experimenting, I would suggest getting a pair of generic 2-way crossovers, something like some Radio Shack Realistic 40-1296A. These have different taps to choose different crossover frequencies. You can play around with these and see if the sound improves or not. I would also get some stuffing to put inside the cabinets, somewhere like your local hobby store should have some cushion padding that would be cheaper than getting it from a speaker supplier.

Hope this helps.

 

[bennattj]

Thanks--yeah I'm thinking adding more/replacing insulation will give a pretty cheap and noticeable improvement as well. There's a small amount inside, but I would imagine more would help a lot. I'm somewhat thinking there's some cabinet resonance going on at some frequencies but not sure if it's just the woofer's response.

 

[Dave1027]

I think before you begin throwing money into mods, you need to figure out why. What is it you don't like about the sound as is? Also, do they have any clarity? If the answer is no then it may not be worth it.

The varistor is like a circuit breaker but once it is activated, it never fully restores. It stays a little resistive. You might think about removing those. Maybe it's the cause of one dead woofer? And why only put varistors on the woofer? Is it because of the low cap on the tweeter?

 

[Nat]

More damping isn't necessarily better - too much and everything sounds dead. And optimizing damping is very complicated because what sounds best on one song or type of music may not sound best with a different song or type.
But it might be fun to experiment. But do one speaker and compare with an original over a period of days.

 

[bennattj]

Actually the more I think about it, I think the room is my biggest problem here (and that's not going to be fixed). I definitely hear things off although can't quite say exactly what it is. It's easier to notice during the frequency sweeps and you hear the up-and-down (kind of whomp-wha-wha, instead of a flat up signal). But based on trying a few different toe-ins, I'm dealing with a lot of problems and the setup itself is likely introducing some (or a lot) of comb filtering.

Currently there is a small amount of batting along the back wall of the cabinet. Gemini suggested lining one of the sidewalls (not both) and maybe the top or bottom. So I might play around with that.

 

[Nat]

I think damping three of the six sides does a good job on internal reflections without overdamping and without making the box act as if it bigger than it is and upsetting the alignment.