• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Apparently, I suck at math + need advice

Wigwam Jones

Wigwam Jones

Caesar non supra grammati
I have a pair of The Fisher XP56b speakers. I'd like to 'modernize' them, but I haven't yet decided how to do that.

The cabs are in excellent condition. Good wood veneer, wouldn't need much more than a nice refurb, no need to even strip/refinish; probably just some steel wool and minwax.

The cabs measure 21" tall x 11.5" wide x 9" deep. The cabs appear to be constructed of 1/2" MDF; the back is flush-mounted and the front is mounted in about 1/2". The speaker board appears to be 1" thick.

The speakers are a sealed two-way design. 8" woofer, rubber surrounds which appear to be in excellent condition. Cone moves freely, no rubbing, sound fine. The mid/tweet appears to be about 4", paper cone, has some mild rippling distortion to the paper cone, as if it had gotten wet at one point. Pulled the tweeter, no sign of any damage, though. Manufacturer code on the magnet of the tweeter is 137 / something (can't read). The cab appears to be stuffed with fiberglass. I haven't pulled it out, nor have I pulled the woofers yet to see what lurks beneath.

My first thought was to simply check out the crossover and see if a cheap recap might not do wonders for this little set of speakers. If that doesn't bring them into shape, then perhaps replace the tweets.

However, that brought me to trying to figure out the volume of the cabs. I tried, I really did. But I keep coming up with silly numbers for the volume, like 1.25 cubic feet / 25 liters. That can't be right, can it?

So, first things first; can someone tell me what the volume of these cabs happens to be?

Second, what are your thoughts on simply recapping these?

Third, if you were going to replace the tweets, what would you be looking at in the way of low-buck replacements? Would you replace just the tweets, or go for the full monte and do the woofers too? Remember these are sealed cabs, not vented. I'm looking to keep them that way - high efficiency - want to use them with my new Squidward-built tube amp.

Any and all suggestions welcome, including 'throw them in the trash and start over'! Although that would be less fun.
 
Register to hide this ad
OK, I get about .9 ft3. but who cares as you're just going to look at a new tweeter and fresh caps. Get the value off the cap and work it backwards in a simple crossover calculator to get the crossover point. You can use that to see if there's any common tweeters you can swap in.
A bigger issue is probably efficiency as a lower efficiency tweeter will be muted which is harder to deal with than tossing a resistor in to quiet a more efficent louder one.

Get the cap value and let's go from there....If it's 8-10 uf maybe some of these EPI tweeters I have would be a nice place to start.
 
Andyman said:
OK, I get about .9 ft3. but who cares as you're just going to look at a new tweeter and fresh caps. Get the value off the cap and work it backwards in a simple crossover calculator to get the crossover point. You can use that to see if there's any common tweeters you can swap in.
A bigger issue is probably efficiency as a lower efficiency tweeter will be muted which is harder to deal with than tossing a resistor in to quiet a more efficent louder one.

Get the cap value and let's go from there....
Click to expand...

OK, so the caps/crossover will most likely be mounted on the back panel inside the speaker near the speaker wire inputs, yes? Tell me (yes, stupid question) are capacitors color-coded or do they have their value written on them. 'Cause you know...I'm color blind. Sigh.
 
Wigwam Jones said:
I have a pair of The Fisher XP56b speakers. I'd like to 'modernize' them, but I haven't yet decided how to do that.

The cabs are in excellent condition. Good wood veneer, wouldn't need much more than a nice refurb, no need to even strip/refinish; probably just some steel wool and minwax.

The cabs measure 21" tall x 11.5" wide x 9" deep. The cabs appear to be constructed of 1/2" MDF; the back is flush-mounted and the front is mounted in about 1/2". The speaker board appears to be 1" thick.

The speakers are a sealed two-way design. 8" woofer, rubber surrounds which appear to be in excellent condition. Cone moves freely, no rubbing, sound fine. The mid/tweet appears to be about 4", paper cone, has some mild rippling distortion to the paper cone, as if it had gotten wet at one point. Pulled the tweeter, no sign of any damage, though. Manufacturer code on the magnet of the tweeter is 137 / something (can't read). The cab appears to be stuffed with fiberglass. I haven't pulled it out, nor have I pulled the woofers yet to see what lurks beneath.

My first thought was to simply check out the crossover and see if a cheap recap might not do wonders for this little set of speakers. If that doesn't bring them into shape, then perhaps replace the tweets.

However, that brought me to trying to figure out the volume of the cabs. I tried, I really did. But I keep coming up with silly numbers for the volume, like 1.25 cubic feet / 25 liters. That can't be right, can it?

So, first things first; can someone tell me what the volume of these cabs happens to be?

Second, what are your thoughts on simply recapping these?

Third, if you were going to replace the tweets, what would you be looking at in the way of low-buck replacements? Would you replace just the tweets, or go for the full monte and do the woofers too? Remember these are sealed cabs, not vented. I'm looking to keep them that way - high efficiency - want to use them with my new Squidward-built tube amp.

Any and all suggestions welcome, including 'throw them in the trash and start over'! Although that would be less fun.
Click to expand...

1.25 cubic feet is what you get by multiplying the exterior dimensions in your case. It will be less when removing wall thickness; according to your dimensions, about 0.85 cubic feet. Remove a bit to account for volume of the drivers, but then you can add some because the fiberglass makes the box seem bigger, but how much is hard to tell. In aperiodic boxes I built, adding the ammount of stuffing that I did to the 28 liters box made it seem to be about 36 liters, so about a 29% increase.

az
 
20*10.5*8=1680

1680/1728 = 0.97 ft^3

As for how to upgrade them, well, how do they sound now? See which of the three drivers, if any, sound good?
 
dumptruck said:
20*10.5*8=1680

1680/1728 = 0.97 ft^3

As for how to upgrade them, well, how do they sound now? See which of the three drivers, if any, sound good?
Click to expand...

Thanks! They sound muddy. Like the highs are all rolled off. And they're two-ways, so only a woofer and a mid/tweet.
 
Might as well try the recap first, since it's probably a single cap like andy said. Value will hopefully be written on them. Awww, I double suck at reading. Scuzzer wins the internal volume calculation.
 
To answer your last question, though caps may come in different colours, the value is printed on each one. I like the 1% Daytons, from Parts Express. Even the 5% are pretty good, and much less money.

Andy has a pretty good suggestion, if the existing cap is the right value. Those EPI tweeters are a cut above.
 
Andyman said:
OK, I get about .9 ft3.
Click to expand...

+1 on that. That's about the estimate I'd make too.

Replacement tweeter? The Dayton Classic DC28F from Parts Express. No question. It should work with simple (i.e, just a cap) crossovers OK. Might need some resistor for an L-pad, but I doubt even that. For less than $20 each, they're pretty darn good!

EDIT: The EPI/Genesis type inverted-dome that Andy suggested should also work well. They'll definitely play well down to below 2000 Hz. The factory 10uf cap is about 1800 Hz, IIRC...

Regards,
Gordon.
 
Last edited:
luvvinvinyl said:
To answer your last question, though caps may come in different colours, the value is printed on each one. I like the 1% Daytons, from Parts Express. Even the 5% are pretty good, and much less money.

Andy has a pretty good suggestion, if the existing cap is the right value. Those EPI tweeters are a cut above.
Click to expand...

Cool, thanks! What do you think about retaining the existing woofers? They look like they're in good shape, they sound fine, but I notice that compared to modern woofers, they're shallower. Thoughts?
 
The values are written on the cap and there are usually 3 sets of numbers. 2 for sure.

Capacitance, voltage and maybe tolerance. What we're looking for is the capacitance and it should be from say 5-15uf.
 
Andyman said:
The values are written on the cap and there are usually 3 sets of numbers. 2 for sure.

Capacitance, voltage and maybe tolerance. What we're looking for is the capacitance and it should be from say 5-15uf.
Click to expand...

Thanks, Andy. I will try to get the value later on tonight. At the moment, I have to run - time for getting hit on the head lessons.
 
No need to change the woofers if a) they sound good b) they work well in the box and c) they're not broken. Usually, they're not the weak link in speakers like these (you've already identified the most common weak link- the tweeter...).

Regards,
Gordon.
 
Wigwam Jones said:
Cool, thanks! What do you think about retaining the existing woofers? They look like they're in good shape, they sound fine, but I notice that compared to modern woofers, they're shallower. Thoughts?
Click to expand...
One step at a time, Grasshopper :)

If you are serious about swapping woofers, just build some new cabs for some woofers you like rather than trying to retro fit an old box with something that works.

And that's a whole 'nuther thread....
 
Wigwam Jones said:
Cool, thanks! What do you think about retaining the existing woofers? They look like they're in good shape, they sound fine, but I notice that compared to modern woofers, they're shallower. Thoughts?
Click to expand...

There are some really shallow modern woofers, too. Dynaudio springs to mind, first, as an example. Not suggesting you use those ($$$$$), just saying that there is nothing wrong with your woofers, if the only thing you can key on is that they are shallow.

I'd keep 'em, and see what the existing xo has to say. If there is more parts than just a cap, try to post a schematic. That info will go a long way in the decision-making process for tweeter selection.
 
You must log in or register to reply here.
Back
Top Bottom