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-   -   design extremely low SPL coroporate america 1-way speakers (http://www.diyaudio.com/forums/full-range/85752-design-extremely-low-spl-coroporate-america-1-speakers.html)

phorensic 1st September 2006 10:24 PM

design extremely low SPL coroporate america 1-way speakers
 
I had a wild idea yesterday, design some 1 driver fullrange speakers for my desk in Corporate America. This presents some opportunities, namely major compromises in the design. Normally you have to design an enclosure to make sure the speakers can handle enough power without bottoming out, make sure they have flat response, adequate SPL given a low efficiency, etc.

Well, we are talking LOW low level listening. Without having a perfect grasp of relative dB and not having my meter at work, I would say the office is roughly at 60dB and I'm playing my speakers at *maybe* 65dB, certainly well under 70dB. Does this not make design much easier?? I also don't care about perfectly flat response, notch filters, tight bass, etc, I mean this is 65dB we are talking about, KISS.

Driver chosen = Hi-Vi B3S. It's small, it looks cool, it performs well, and other people seem to like it...and it's CHEAP.

So anyway, I need to design an enclosure. Currently, I've been playing around with WinISD and have come up with the following numbers. I can afford a tall skinny box of about 3.2L, with a port totally guessed up of 0.50" dia and 2" long. This supposedly gets me an F3 of 62Hz. I guess at this point I should say that I would like a vented design with the lowest frequency response possible in an enclosure approximately 3L. The peaky response around 100Hz in my simulation is OK, because at low volume levels, as I understand it, the bass can be boosted to make the music sound OK, kind of like what the "loudness" button does. Now I've also heard from this Zaph dude that this B3S shouldn't be used full range at all, that it should be crossed over at 150Hz, etc. Again, 65dB with perfect freq resp. not being important is the goal here. The cone is not going to bottom out either, my power calculations say I should be well under 0.25W. Shouldn't this afford me a lower F3? WinISD shows the cone hitting 3mm well before normal at home listening levels of like 85dB or so unless you design for I guess ~100Hz F3, another perk of listening at 65dB!

Am I being unrealistic? What can we do to tweak this further? What should my highpass filter be set to? Ideal port dimensions are a mystery to me. Any glaring faults of this setup? What characteristic of the sound is going to be the worst? Any other ideas are appreciated also.

Nanook 2nd September 2006 05:18 AM

check out ..
 
Zaph Audio. good design perfect for your needs

phorensic 2nd September 2006 05:31 AM

This was my inspiration for this post: http://www.zaphaudio.com/audio-speaker18.html

The problems I have is that every design I see for fullrange speakers using one driver is that they are optimized for 80-100dB (pulled that out of my butt) listening. I have a unique requirement/opportunity of never getting that loud and thus need guidance on enclosure design to suit it.

Nanook 2nd September 2006 09:57 AM

oops...the scourge of forums: I almost always scan the posts . So of course I restated (as I often do) something that has already been posted. Sorry.

If you can manage a little more $$ The TB 1052 would be very nice and a lot more efficient. (and therefore perhaps a little more useable in other situations..)
You do not state what you will use as an amplifier. If cosmetics are important it looks the part.

AFAIK, it won't matter much about how the speakers measure, but you should consider the
equal loudness contour while designing your loudspeakers. I am pretty sure that is the reasoning behind Zaph's suggestion regarding a sub (and that the bass gets muddy fast--from Zaph's site)

Dumbass 2nd September 2006 10:39 AM

Get a bass shaker from partsexpress, and mount it on the underside of your chair.

phorensic 2nd September 2006 09:19 PM

Haha, bass shaker to my chair. That's funny.

Nanook, the amplifier design is the second design project. I haven't posted in the forums on that, yet. My goal is to design the most simple sub 1W amplifier possible. I have a power supply for it already, from a failed gainclone project. I hope to be able to come up with something that uses just a single transistor (FET, JFET, MOSFET, bi-polar) per channel. No need to ultra-filter the ripple, constant current source this and that, or make the distortion .000001 with massive feeback, have a high gain with multiple stages to get there, etc. Maybe you can suggest something along these lines?

Also, it's entirely possible that the PC's soundcard has enough gain, but I need a current buffer. Does that sound right? Again, more fuzzy logic from what I've soaked up on the net: the soundcard doesn't have the right output impedance to be hooked directly up to 8ohm speakers, so instead of hooking up a high gain amp, I can do a current buffer of sorts (with obviously the right output impedance), right?

You suggested the TangBand driver because it is more efficient. It may sound stupid, but I fail to see why efficiency is important in this design. Please explain.

phorensic 2nd September 2006 09:38 PM

Amplifier design thread - http://www.diyaudio.com/forums/showt...threadid=85809

Nanook 2nd September 2006 10:00 PM

bass shaker..
 
isn't that bad of an idea. It will certainly give you a "tactile " bass , usually cheap at parts express.

I asked if a different driver could be chosen (under $20 each), so that perhaps a more usefull speaker could be produced (you may not be in corporate america forever). Some mini-autographs would be SO cool :-)

hmm. for an amp, maybe a 6BM8 SE design, lucky to get 1.5-2 watts


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