Speaker Rebuild - Radio Shack 40-1271 and 40-1024

[davidallancole]

Radio Shack 40-1024
http://support.radioshack.com/suppor...oc15/15880.htm

Radio Shack 40-1271
http://diyaudioprojects.com/Drivers/40-1271/40-1271.htm

Hi guys (and gals),

You may have remember me posting things about me building speakers using these drivers previously, but I am hoping to find a setup suitable for them with a little help.

I like the idea of an OB along the lines of what Scottmoose has mentioned in this thread:
Bush & Bass OB (advice?)

But I thought my room may be better suited to running the subs in sealed boxes and putting the "fullrangers" into aperiodic boxes.

Anybody with more knowledge have some suggestions?

I plan on using a bi-amp setup. I haven't built the amps or crossover yet, so that is all variable. I planned on using LM3886 for the subs (have two subs per speaker, thus 4 subs and 2 fullrangers for a stereo set) and LM1875 for the fullrangers. Then I can add an active crossover.

I have attached the layout of my livingroom.

[gmilitano]

I never tried the 40-1271 in an aperiodic enclosure, but given the ultra high Q, you will not want much vent resistance.

Open baffle they worked pretty good.

The 40-1024 won't go too low in a sealed enclosure. Below is a very quick sim for the 1024 using ISD online. Perhaps someone could comment on how much room gain you could expect.

[davidallancole]

I have been using them in Open Baffle for the last little while and I like them. I have the two subs close to the floor and the fullranger around ear level. The main baffle is 12 inches and the wings are 12 inches and 13 inches. They sound all right but are nothing special. That could be because they are cheap speakers. I can only keep them ~1-2 feet away from the wall.

Right now the speakers are all run in parallel. The subs, you can clearly hear voice out of, so maybe it will be cleaner sounding if I use a seperate amp and crossover for the subs.

I should say the kind of music I listen to as well. Its metal, punk, but I also like things like the Slackers which is basically and R&B band I guess, with horns and clean guitars and what not.

[GM]

Originally posted by davidallancole
You may have remember me posting things about me building speakers using these drivers previously, but I am hoping to find a setup suitable for them with a little help.

But I thought my room may be better suited to running the subs in sealed boxes and putting the "fullrangers" into aperiodic boxes.

Anybody with more knowledge have some suggestions?

Greets!

Not really , but I don't get to browse as much as I once did . Anyway, to truly aperiodically damp this driver requires a ~141"^2 x 96" long end loaded pipe stuffed with ~1.5 lbs/ft^3 of polyfil. Shorten the pipe and its CSA must rise to maintain the same total amount of stuffing. Considering the diaphragm's construction though, it may sound very smooth, yet dull/lifeless/excessively compressed, so a folded open baffle seems a better choice overall. Only one way to know for sure though.

WRT the 40-1024, I'm in the build for max gain BW and roll it off as required if need be 'camp', so considering it has enough excursion to tune it low, a ~3.75 ft^3/20 Hz MLTL gets my vote and a worst case scenario is you wind up plugging the vent for a ~critically damped sealed alignment.

GM

[GM]

Originally posted by davidallancole
Right now the speakers are all run in parallel. The subs, you can clearly hear voice out of, so maybe it will be cleaner sounding if I use a seperate amp and crossover for the subs.

Greets, part deux!

Well, the MLTL cab could be configured to get the sub drivers up near the mains so that they don't sound 'phasey'/disconnected, though bi-amping with steep slopes is still a good plan.

GM

[davidallancole]

Thanks for the responses guys. I am getting the opinion that I should leave these in open baffle form. At the bottom is attached the proposed drawing of what I want to build.

I am not sure what I should do exactly for the croosover point with the subs. If I build the main baffle 15 inches wide (using the chart from http://melhuish.org/audio/baffle.html), I should have a roll of at around 200 Hz? Would I then build a crossover to cross at 200 Hz for the sub? Would it be 12, 24, 48 db/octave? or can I cross lower or should the crossover point actually be higher than 200 Hz?

Thanks for your help everyone.

[gmilitano]

Originally posted by davidallancole
...
They sound all right but are nothing special. That could be because they are cheap speakers. I can only keep them ~1-2 feet away from the wall. ...

I should say the kind of music I listen to as well. Its metal, punk, but I also like things like the Slackers which is basically and R&B band I guess, with horns and clean guitars and what not.

That is pretty much the conclusion I came to, they are ok. I never got a chance to mod the drivers, but perhaps that could add quite a bit. For hard music like that, you will likely want to keep the bass notes away.

OB with the LF driver, you should be able to get a pretty good system. Like GM said, keep the drivers close. As for the XO, if you have an adjustable active, you could try different values and slopes till you find a combo that works well.

[Geoff H]

Hi David, your plan is very similar to something I have just thrown together.

If you have access to a second amp, use that to drive the bass. Bass control to near max. Quick and dirty way to hear results. I discovered the sensitivities at the desired crossover were very similar, so I could try a passive xo.

My preference is to crossover at about 100Hz. I find that provides the sound of a single driver. Using a series type xo, I broke a few rules. The bass (4 ohm 6x9, fs 50Hz) is shunted with a 470 mf bipolar elect. and the wide range (8 ohm 6") is shunted with the 8.5 v tap on a 30VA transformer.

Like I said, quick n dirty, but it works. I was planning a 20w/60w bi-amp. It only needs a few db compensation from 40-70 hz.

Geoff.

[davidallancole]

Thanks guys.

When you are saying keep the drivers close, are you reffering to the just the subs, or are you saying keep the subs close to the fullranger, like in the following picture.

[gmilitano]

You will want to keep them close to the fullrange unit.