tresch said:
You have the idea... it is why i suggested 4 drivers for the bottom. Paralleling 2 bass driver sto get 2 ohms will be hell on any amplifier (and remember, as a generalization, that every time you halve the impedance you double the amps distoryion), and you don't want to try attenuating a bass driver.
dave
Okay I gotta order some stuff and experiment...
If two drivers in serial configuration produce approximately the same sound (half energy to each speaker, but twice the surface area,) and two drivers in parallel produce MORE output (same energy to each speaker, twice the surface area, but more current through the amp,) would not, then, four speakers in a series/parallel configuration still produce significantly more volume, thus still require attenuation?
There are plenty of posts out there about how different wiring affects resistance, and affects the amp, but little that I have found that actually describes the acoustic results of various configurations, at least with any depth. Add to that the fact that there are so many myths and misconceptions and so much subjectivity about, it makes it hard to find anything concrete! I guess that's why this whole speaker design thing is such an attractive challenge!
If two drivers in serial configuration produce approximately the same sound (half energy to each speaker, but twice the surface area,) and two drivers in parallel produce MORE output (same energy to each speaker, twice the surface area, but more current through the amp,) would not, then, four speakers in a series/parallel configuration still produce significantly more volume, thus still require attenuation?
There are plenty of posts out there about how different wiring affects resistance, and affects the amp, but little that I have found that actually describes the acoustic results of various configurations, at least with any depth. Add to that the fact that there are so many myths and misconceptions and so much subjectivity about, it makes it hard to find anything concrete! I guess that's why this whole speaker design thing is such an attractive challenge!
Yep, one driver with twice the power is as loud as two drivers with half the power. But, as dave mentioned, cutting the impedance in half doubles the distortion. So I'd think you'd be better off with running two drivers to double the resistance to keep distortion low and still attain the same output.
And a quick picture of the progress. I need to go ahead and finish them up. I've been slacking.
tresch said:
Everytime you double the number of drivers you get 3 dB more efficiency. So 2 drivers gives you 3 dB more, 4 6 dB more.
But to wire them up you change the impedance... if we assume a perfect voltage source (many amps are not, especially when considering impedances below 6 ohms)... then wiring 2 in parallel, gives 1/2 the impedance or 2 times the power for an extra 3 dB, wiring in series doubles the impedance which halves the power, - 3dB. Series/pararllel 4 drivers and you are back at the same impedance, so the same power.
2 CHR in series gives 8 ohms, same levels as a single at 4 ohms
2 CHR in parallel gives 2 ohms, 6dB more level than a single at 4 ohms (but not really because your amp is likely going to be current limited if it doesn't just go up in smoke)
4 CHR in series-parallel gives 4 ohms, 6dB more level than a single at 4 ohms
dave
Okay yeah, that's about what I was thinking. Looks like I'll just be playing with quieting down the mid-tweet.
Then the big question is: How much will removing the bass output from the CHR70 affect its ability to handle power without distortion? Or rather: If I'm using multiple bass drivers to double my power handling on the low end, will the single mid-tweet be able to keep up?
We'll find out soon enough, I suppose!
Power handling is rarely so much about ultimate SPLs as dynamic BW, the demands of which are always most severe in the LF regions. In a domestic environment, you're unlikely to have much of an issue.
tresch said:
I think this depends on two factors, xover freq and if you're bi-amping. Any frequency >250Hz should greatly increase the mechanical power handling, but then you have to consider thermal power handling (I have no idea what that might be). If you're bi-amping, the relative output shouldn't be a concern as you should be able to control their relative outputs. If you're not bi-amping, have a couple of resistors at the ready to pad the "woofers". If you're expecting to use the full 20W capability of the CHR, you'll need paralleled 10W resistors. Frankly, my single CHR got so loud that my wife, 2 floors down, was prompted to ask if I knew how loud I had it.
🙄
planet10 said:
I agree but it is an option if the mid-tweeter is too low and you've only got one amp. And for a few (insert local monetary units), it's an option that can be evaluated to determine which is better, too much midbass or degraded woofer performance. And it's not permanent.
Version 2.0 with the modification that Dave suggested. With the top ballast removed they become a lot less top heavy and I don't know if they will even need a base. I've got some sanding to do today and I'll test their stability later as well.
Your making me jealous Italianstylion, with my current project load of 4 LM3875 monoblocks and 2 F5 amps I'm likely to get these cabinets started in I don't know, never LOL.
I think I'll omit the second driver in mine at first to see what we get, then if I feel I need better power handling I'll add the second. I have visions of building my mother a pair of these as a gift, so the extra two drivers could come in handy yah dig....
They are kinda cute don't you think? LOL...
Good job ItalianStylion I look forward to your review after a full breaking in... Peace and keep well.
I think I'll omit the second driver in mine at first to see what we get, then if I feel I need better power handling I'll add the second. I have visions of building my mother a pair of these as a gift, so the extra two drivers could come in handy yah dig....
They are kinda cute don't you think? LOL...
Good job ItalianStylion I look forward to your review after a full breaking in... Peace and keep well.
Even with sand or other heavy ballast material in the lower cavity, these will still be very tippy - I'd suggest a base plate at least 10" wide.
If you can find a local countertop shop that works with granite or synthetic quartz, it shouldn't be too hard to talk them out of a sink cut-out (amazing what a case of brew can get you on a sunny Friday afternoon)
If you can find a local countertop shop that works with granite or synthetic quartz, it shouldn't be too hard to talk them out of a sink cut-out (amazing what a case of brew can get you on a sunny Friday afternoon)
chrisb said:
What a fantastic idea! I'll see what i can find locally. Immediately I'm having trouble coming up with ideas about how to attach that to the bottom of the cabinet but I'm sure I could come up with something.
chrisb said:
If you have a cat around this is especially true. It's amazing how much tipping force they can generate when they launch themselves from the top of a speaker, or stretch up and lean on one. I had to patch a 1/4" deep dent when my (tiny) cat jumped off a Bose cabinet and launched it into the wall.
Cheers
John
italynstylion said:
Careful when you come up for a VI diyFEST. One of our 10 cats may lunch on you.
dave
italynstylion said:
Funny- Dave, Scott Dunn & I were discussing this just yesterday afternoon. It might take a 2-4 (aka 2 dozen box), but the same shop should be able to drill a few through holes, and you'd attach to the enclosure with either a KD furniture assembly bolt, or even truss head wood screws. Don't worry about counterboring in the stone - PSA felt or rubber feet will raise the base plate higher than the head of the screws.
Now, if you wanted to get carried away and install spikes of some type, then things get a bit more interesting. In which case Corian or similar solid surface material ( also likely to be available from many countertop shops) can re relatively easily worked with using carbide woodwork tooling, and for non-structural work, can be glued with either white PVA or standard epoxy resins, as opposed to the proprietary adhesives that require special mixing/application guns. A few years ago, I made some Corian platters for my Rega turntable - all the machining was with hand rounters and a simple circle jig.
And depending on which gets to your lap first, Dave & Ruth's cats might well launch and lunch on you. They're a bit schizophrenic - can't decide if they're feral or domesticated (the cats that is)
ROFL at the cats comment....
How heavy is corian? Do you think that would work well? I have a friend on another forum that might be able to get some. He recently posted a thread about it. I might have to hit him up.
How heavy is corian? Do you think that would work well? I have a friend on another forum that might be able to get some. He recently posted a thread about it. I might have to hit him up.
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