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Old 18th November 2010, 04:04 AM   #21
GM is offline GM  United States
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.......I'll need an L-pad to go with that?

I have pretty severe tinitus..........

I'd say I listen at a level where it would be quite hard to communicate with someone else in the room, 100-105 dB or more?
Depends on the XO and what, if any, driver tweaks are done, but wouldn't hurt to have some just in case.

Sounds like the super tweeter would be wasted on you same as me, but if others with decent hearing will be listening, best to use them.

Sounds like these won't play loud enough for you, but at the price, worth the gamble to find out.

GM
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Old 18th November 2010, 05:22 AM   #22
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Originally Posted by Cascadie View Post
I have a couple of problems though. I have pretty severe tinitus, which is so loud that I can hear it at highway speeds with the windows down. This is combined with a large dropout in my hearing from the high midrange and trebles (which I why I'm heading straight for a tweeter in the package). So, I like to listen on the loud side to get over my built-in noise floor. I don't have any gear for measuring, but I'd say I listen at a level where it would be quite hard to communicate with someone else in the room, 100-105 dB or more?
I have tinnitus too + a large upper midrange suckout. Doctor told me its up there with the worst but not like u describe it. My hearing chart (if thats the phrase?) has a 15-20 dB suck out at around 2.5 kHz on both ears. Funnily enough I can hear stuff others cant hear but that comes from years of training.

Dont turn the volume up unless u really have too. Use ear plugs if theres prolonged exposure even to low levels of background noise. Time exposed to noise is a bigger factor than level. Try listening to classical music at low volume. I read that Pete Townshends was advised to do that, I tried it and it helps for me. Theres also certain foods and beverages that aggravates it. Caffeine for example.

Regards /Bo
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Old 18th November 2010, 05:41 AM   #23
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Perhaps I should rephrase. 100-105 dB is where I can no longer perceive my tinitus, but I really do like it when I can't "hear" it. I'll have to try the classical music thing, that's interesting.

One of my very early jobs was working in a wire manufacturing plant, where it was just shy of painful without ear protection. That's where I lost my hearing, but the tinitus I believe is congenital. My dad used to complain about all the same stuff I do now.

I've been beating my head against WinISD Pro tonight with some (very) limited success. I think I've got the parameters that it likes for the B20FU20-51FW, mostly from the chart at PE. From that point on things quickly turn south for me. So:

1. Which alignment should I use?
2. I'm unclear as the the tuning. 43Hz? Dave's comment about 170Hz threw me a little curve. (ok, it went right by me, let's be honest)

Kurt
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Old 18th November 2010, 06:15 AM   #24
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......otherwise the vent will be too long and in some cases too small in area, mis-tuning the cab.
For instance, using the MathCad software, it takes a 3" dia. x 3" long vent to tune your pipe (Fb) to ~ the published 43.25 Hz Fs while WinISD Pro calculates a 5.61" long vent which will in theory lower Fb to ~35 Hz. Due to the physics of the situation though (the pipe is acoustically too small for the driver's specs), it's doubtful that it would make an audible difference except possibly on tracks with low organ or synth music, so just putting some numbers on it for example.

GM
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Old 18th November 2010, 06:25 AM   #25
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Hard to put an 8" driver in a box 5" wide
This went right by me, too. I was thinking of doing it with one of the drivers you mentioned, or even the cheap Tang Band. Maybe that could be my second project. They just look so cool.

Kurt
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Old 18th November 2010, 07:43 AM   #26
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Quote:
Originally Posted by Cascadie View Post
100-105 dB is where I can no longer perceive my tinitus...........

I've been beating my head against WinISD Pro tonight with some (very) limited success.

1. Which alignment should I use?
2. I'm unclear as the the tuning. 43Hz? Dave's comment about 170Hz threw me a little curve.
With tinnitus from age 3 due to medical problems combined with lots of >120 dB peak SPL events in my life, I'm the same way and I know from experience that no single driver speaker I've built or auditioned will drown mine out except at high enough distortion to make me leave the room. To achieve it at low distortion, it takes a small cinema sound/PA system (large HF horn/dual 15" HE woofers) which I gather will be well beyond your current budget.

WRT WinISD Pro, inputting driver specs can be frustrating even following its instructions since published specs often have enough anomalies to keep it from being able to resolve them all without your help, but for quick sims you only need to load Fs, Vas, Qts, same as any on-line or similar basic simulator, it just won't give you as much design data without the extra specs. You can always call it up later in the 'editor', change the data and re-save it for a more detailed set of plots.

I haven't read it, but here's a tutorial that may be of help along the way:
WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com

Library of mostly (sub) woofer driver files you can DL/save in the Pro's 'driver' folder:
Downloadable WinISD Pro Files - Home Theater Forum and Systems - HomeTheaterShack.com

What alignment to use is a room modes and personal sonic preference dominated decision, so about all I can say is that the typical default T/S maximally flat vented alignment will tend to sound 'boomy' in-room due to the room's gain curve boosting the speaker's lower output if positioned anywhere near a wall, and especially near/at a corner.

Since your cab is acoustically too small for such an alignment though, tuning probably won't be too critical, with 35-40 Hz being what I'd try first if vented. Anyway, lots of posts on this subject over the years, so plenty of data/opinions available in a search.

The 170 Hz reference is about the big phase flip with its mid-bass suck-out shown in the sim I posted due to the driver being near the end of your sealed pipe, i.e. its half WL open pipe harmonics modulates the driver's output, so best performance comes from proper driver position along its length: Resonances of open air columns

The pipe itself is tuned (Fp) based on its net volume (Vb) and line length or ~60 Hz in this case.

And since I forgot to load/attach them earlier, my two B20 .wkr files: Downloadable WinISD Pro Files - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

GM
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Old 18th November 2010, 05:47 PM   #27
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Time exposed to noise is a bigger factor than level.
Yes, I've read studies and for the amount of time I have to sit and listen is far less than would damage my hearing, even up at my 100dB+ levels. I have to wait until the wife and daughter are gone to do that. Man, I wish I knew then what I know now. I would have taken far better care of my ears, but I was young, and indestructible.

GM, wow, thanks for all that info. You guys are really giving me the bug, dang you! I got your Bofu (measured) model up and from what I can determine in WinISD there won't be a huge diff in SPL between a sealed cab this size and a vented one. But I figure that "what I can determine" may mean very little at this point.

Parts should show up early next week, and I'll try and post some pics. Fun stuff! I'm already thinking about what I could try next.
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Old 18th June 2011, 09:18 PM   #28
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I thought I'd poke my head back in here long enough to say that I finally put some cabinets together for my bofu's. School calmed down enough for me to slap them together and get them in the living room and I'm pleased as punch with them. Are they spectacular? No. But, like everyone has noted, they are very easy to listen to, and they achieve surprising lows. I don't have measuring equipment, but a test file that sweeps from 10hz - 200hz sounds pretty steady from just below 30hz but does peak a bit at 200hz, which is probably more due to my hearing anomalies.

The cabinets were squeezed into a sheet of 4x8 3/4" birch ply and the measurements came from Ed LaFontaine in another post here regarding the bofu. Thanks, Ed!
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Old 19th June 2011, 03:09 AM   #29
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Love it! Many will not get to hear this bargain of a driver anymore since it's been discontinued. Drat!

Enjoy them!
Zilla
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Old 1st January 2013, 12:57 AM   #30
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Originally Posted by Cascadie View Post
I thought I'd poke my head back in here long enough to say that I finally put some cabinets together for my bofu's. School calmed down enough for me to slap them together and get them in the living room and I'm pleased as punch with them. Are they spectacular? No. But, like everyone has noted, they are very easy to listen to, and they achieve surprising lows. I don't have measuring equipment, but a test file that sweeps from 10hz - 200hz sounds pretty steady from just below 30hz but does peak a bit at 200hz, which is probably more due to my hearing anomalies.

The cabinets were squeezed into a sheet of 4x8 3/4" birch ply and the measurements came from Ed LaFontaine in another post here regarding the bofu. Thanks, Ed!
I have B20s laying around and want to try this or sealed cabinet. I have piezo tweeter with Lpad setup ready to go.

I am wondering sealed (zillaspeak) vs your design, wonder what the differences maybe.

Is there an exact dimensions for the box somewhere?

gychang
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