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Old 22nd February 2013, 04:58 AM   #21
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wallygoots,

Many people would say (perhaps correctly) that the response is too wavy, but I would say go ahead and build it. The curve is not completely out of control or anything, and it looks like your F10 (point at which bass drops to -10 dB) is about 42Hz. If you are lucky, you'll get all kinds of room gain around 40Hz and the bass will be fuller than that graph looks.

Looks like you are going to need a port diameter of 1.5 inches by about 5.5 inches for the 53Hz tuning. Dimensions of the box can be changed considerably, as long as you maintain the volume.

For the build, you have a few options:

1) Build a prototype out of foam core (lots of info in the foam core threads) to see how they sound, then build a proper pair if you like the prototype.

2) Build them out of standard 1/2" ply to keep costs down and hope for the best.

3) Build them out of 3/4 Baltic Birch ply, assuming they are going to be perfect and worth the money.

When I built the nanoTowers I went with option 2, and I have no regrets. Sure, there may be voids in the ply but not that I can hear. After all, these little drivers aren't putting very much pressure into the cabinets...

Last edited by cogitech; 22nd February 2013 at 05:01 AM.
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Old 22nd February 2013, 05:30 AM   #22
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Look at excursion for that sim. Try 90hz and 3L.
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Old 22nd February 2013, 09:27 AM   #23
xrk971 is offline xrk971  United States
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I think tuning at 53 Hz is too low for this driver, as Tuxedocivic pointed out, look at max excursion as 883si xmax is listed as 0.5 mm. The only way a driver like this can reach down to 53 to 55 Hz is as a mass loaded transmission line. You can duplicate the design that Cogitech came upon by accident as that seems to work as documented by many who have tried, or use the TABAQ design which is basically a 20 square in cross sectional area (say 4x5 in) x 30 in long with a port at the end of about 2.5 square in cross sectional area x 3.8 in long with the driver mounted about 10 in down from closed end and stuffing filling first 20 in of the line. This can be folded into a smaller box of course. The plans can be found on Bjorn Johanessen's website http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf If you want to make a pure bass reflex, you should stick close to the automatic tuning that WinISD finds which is probably close to 70 Hz and the shape doesn't matter but the longer and skinnier you make it, the more it will tend to behave like a transmission line.
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Old 22nd February 2013, 03:30 PM   #24
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This reveals how much I have yet to understand, but truthfully I don't really know what 53hz versus 90hz means. With a little google help, is it a good working understanding to say that Hz is the bass cut off for a speaker design? If that is so, I can see why 53hz would be way too low because this is only a 3" Tang Band. Is it the xMax that you mention, xrk971, that gives that data?

I tried to follow you on the mass loaded transmission line idea you mentioned. Are you meaning that this speaker can achieve deeper bass if the box is constructed in such a way as the TABAQ? Does the stuffing as well as the volume (and length of the cab) help achieve a deeper bass response from the same speaker? So much to learn. Thanks for your patience folks. I must say, this is an interesting and curious project.

I did try a sim with 90hz and 3L like you mention Tuxedocivic. Would this be a better design? Cogitech, I have 3/4" ply laying around and I'm used to working with wood. I'd have to buy foam board. Yeah, it's cheap, but the ply was free and I think would last better.

Here's the graph:
3.0 L
90hz
W 5.2" x H 12" x D 6.2"
Single 1.125" circular vent that is 2.25" long (I'm thinking extending the sides by 4 inches like a built in stand and putting the vent on the bottom). Bad idea?
Click the image to open in full size.

I have some wiring questions for you all too. I have no idea on how wiring works in these. Is it as easy as straight run from the speaker to the speaker terminal on the back of the cab? Or do I have to put in other electronics inside the cab? I'd be running these out to a small amp then to my TV via SPDIF or MP3 player via SPDIF to 3.5mm jack.

Another question about wiring. Let's say I get into this and want to make a 2.1 set for my computer. I noticed that Subwoofer amps like the Dayton SA series have speaker outs on them. Would the Subwoofer amp run these Tang Band speakers I'm working on too? If so it's almost as reasonable an idea to build a small sub with amp as it is to buy a dedicated amp for these Tang Band speakers. Maybe I'm oversimplifying it though.
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Old 22nd February 2013, 03:36 PM   #25
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Quote:
Originally Posted by xrk971 View Post
I think tuning at 53 Hz is too low for this driver, as Tuxedocivic pointed out, look at max excursion as 883si xmax is listed as 0.5 mm. The only way a driver like this can reach down to 53 to 55 Hz is as a mass loaded transmission line. You can duplicate the design that Cogitech came upon by accident as that seems to work as documented by many who have tried, or use the TABAQ design which is basically a 20 square in cross sectional area (say 4x5 in) x 30 in long with a port at the end of about 2.5 square in cross sectional area x 3.8 in long with the driver mounted about 10 in down from closed end and stuffing filling first 20 in of the line. This can be folded into a smaller box of course. The plans can be found on Bjorn Johanessen's website http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf If you want to make a pure bass reflex, you should stick close to the automatic tuning that WinISD finds which is probably close to 70 Hz and the shape doesn't matter but the longer and skinnier you make it, the more it will tend to behave like a transmission line.
In my experience, the xmax of this driver is closer to 5mm than it is to .5mm.

.5mm is basically no excursion. It is ridiculous. The pair I have continue to sound great with considerable cone movement. Way, way more than .5mm. I honestly think Tang Band made a typo on the data sheet.
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Old 22nd February 2013, 03:55 PM   #26
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Quote:
Originally Posted by wallygoots View Post
This reveals how much I have yet to understand, but truthfully I don't really know what 53hz versus 90hz means. With a little google help, is it a good working understanding to say that Hz is the bass cut off for a speaker design?
Sub-Bass (16 Hz to 60 Hz). These very low bass frequencies are felt, rather than heard, as with freeway rumbling or an earthquake. These frequencies give your mix a sense of power, even when they only occur occasionally. However, overemphasizing frequencies in this range will result in a muddy mix.
Bass (60 Hz to 250 Hz). Because this range contains the fundamental notes of the rhythm section, any EQ changes will affect the balance of your mix, making it fat or thin. Too much emphasis will make for a boomy mix.
Low Mids (250 Hz to 2 kHz). In general, you will want to emphasize the lower portion of this range and deemphasize the upper portion. Boosting the range from 250 Hz to 500 Hz will accent ambience in the studio and will add clarity to bass and lower frequency instruments. The range between 500 Hz and 2 kHz can make midrange instruments (guitar, snare, saxophone, etc.) “honky,” and too much boost between 1 kHz and 2 kHz can make your mix sound thin or “tinny.”
High Mids (2 kHz to 4 kHz). The attack portion of percussive and rhythm instruments occurs in this range. High mids are also responsible for the projection of midrange instruments.
Presence (4 kHz to 6 kHz). This frequency range is partly responsible for the clarity of a mix and provides a measure of control over the perception of distance. If you boost this frequency range, the mix will be perceived as closer to the listener. Attenuating around 5 kHz will make the mix sound further away but also more transparent.
Brilliance (6 kHz to 16 kHz). While this range controls the brilliance and clarity of your mix, boosting it too much can cause some clipping, so keep an eye on your main meter.

( quoted from PreSonus | Learn - Equalizer Terms and Tips )

Quote:
If that is so, I can see why 53hz would be way too low because this is only a 3" Tang Band. Is it the xMax that you mention, xrk971, that gives that data?
Xmax = maximum cone excursion (movement). Typically listed in one direction (which means the total travel of the cone can be 2x Xmax). The Xmax for the 881SI is listed as .5mm. I think it is closer to 10x that value.

Quote:
I tried to follow you on the mass loaded transmission line idea you mentioned. Are you meaning that this speaker can achieve deeper bass if the box is constructed in such a way as the TABAQ? Does the stuffing as well as the volume (and length of the cab) help achieve a deeper bass response from the same speaker? So much to learn. Thanks for your patience folks. I must say, this is an interesting and curious project.
MLTL is a special cabinet design which can get a lot more out of a driver than a simple bass-reflex design, but the knowledge and tools required to design one properly are an order of magnitude more complex than a simple BR. I designed my nanoTower as a simple BR in WinISD, but since I designed the cabinet to be so long and narrow, I ended up with an "accidental MLTL" which sounds far better than it should, based on my (nearly complete lack of) design knowledge. The TABAQ, on the other hand, was designed from the ground up as a MLTL and probably sounds better than nanoTower. I just needed nanoTower to be quite a bit taller than TABAQ, otherwise I would have built TABAQ.

Quote:
I did try a sim with 90hz and 3L like you mention Tuxedocivic. Would this be a better design?
In theory, yes, but without a sub-woofer filling in all the missing low end, it'll sound like crap. If you plan to only run the Tang Bands, then go with your first design (or, better yet, TABAQ!). For the record, I disagree completely with the opinions that 53Hz is too low. Those opinions are far more educated than mine, but I have direct experience with these drivers and I know they are far more capable than the spec sheet indicates. The grain of salt here is: low to moderate volume. If you plan to run these speakers LOUD, then ignore what I am saying. Also, I should note that people around here also told me that my tuning was too low when I was designing nanoTower. I am glad I decided to proceed anyway.

Quote:
Cogitech, I have 3/4" ply laying around and I'm used to working with wood. I'd have to buy foam board. Yeah, it's cheap, but the ply was free and I think would last better.
Absolutely.

Quote:
Here's the graph:
Yuck.

Quote:
I have some wiring questions for you all too. I have no idea on how wiring works in these. Is it as easy as straight run from the speaker to the speaker terminal on the back of the cab? Or do I have to put in other electronics inside the cab? I'd be running these out to a small amp then to my TV via SPDIF or MP3 player via SPDIF to 3.5mm jack.
Direct wire from the driver terminals to the amp terminals. That is one of the many beauties of using full rangers.

Quote:
Another question about wiring. Let's say I get into this and want to make a 2.1 set for my computer. I noticed that Subwoofer amps like the Dayton SA series have speaker outs on them. Would the Subwoofer amp run these Tang Band speakers I'm working on too? If so it's almost as reasonable an idea to build a small sub with amp as it is to buy a dedicated amp for these Tang Band speakers. Maybe I'm oversimplifying it though.
I don't think the sub amp will power the speakers. I think they are more likely a pass-through for an external amp connected via the sub's "high level" inputs.

Last edited by cogitech; 22nd February 2013 at 04:11 PM.
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Old 22nd February 2013, 05:20 PM   #27
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Quote:
Originally Posted by cogitech View Post
The Xmax for the 881SI is listed as .5mm. I think it is closer to 10x that value.

This is funny Good one.


Quote:
Originally Posted by cogitech View Post




In theory, yes, but without a sub-woofer filling in all the missing low end, it'll sound like crap. If you plan to only run the Tang Bands, then go with your first design

I was shooting in the dark based on experience, just had a look in unibox and I'd maybe try 80hz instead. WinISD doesn't account for stuffing. Once there's a little stuff in there it's pretty flat with a downward taper to 70hz and rapidly falling below 70hz. Not bad sound for a 3L box at low SPL.


Quote:
Originally Posted by cogitech View Post
For the record, I disagree completely with the opinions that 53Hz is too low. Those opinions are far more educated than mine, but I have direct experience with these drivers and I know they are far more capable than the spec sheet indicates.


I would assert I have more experience with this driver than you. I've run it ported 90hz and stuffed well. Sealed of various sizes. A heavy hitting FAST. Even boxless. And I plan on more. Plus I've measure the semi-anechoic frequency response, the nearfield response, the impedance, and even the xmech (in an unscientific way).

xmech was about 2mm by the way. I was able to push it past 2mm but the suspension was tight and I risked damaging things. So watch out if you're actually pushing yours to 5mm.

Quote:
Originally Posted by cogitech View Post

Yuck.
Actually it's not bad for a first try. Again, try 80hz with some stuffing. It's about the only way to get down to 70hz with this driver on it's own. WinISD can't show this properly. Unibox can do a so-so job of showing it.
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Old 22nd February 2013, 05:32 PM   #28
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tuxedocivic,

I have gathered from so many discussions about this driver that you like to listen at considerably high SPL. I have always, on the other hand, qualified my evaluation of these drivers by saying that my application of them does not require high SPL.

This is the source of discord, in my opinion.

Anyway, I maintain that Xmax (and Xmech) on the pair I have is much, much greater than .5mm. and that at moderate listening levels (80-ish dB) they can easily handle the entire frequency range and sound very pleasant while doing so. Perhaps mine are broken in considerably more than others'. I intentionally ran them harder than they like while breaking them in. Heck, they're dirt cheap. Why not find their limits? I'm pretty sure I have, and with no consequence other than - now I know what they can do.

Last edited by cogitech; 22nd February 2013 at 05:37 PM.
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Old 22nd February 2013, 05:41 PM   #29
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I've always said I'm ok with the low SPL argument. I've used them in the same way in my livingroom for a couple days. They were laughable in the bass department. We literally laughed at them. The only time I've beat the crap out of them was in a FAST when they were high passed at 300hz LR4. And yes, I did beat the crap out of them. KyleInCowichan can attest. But without woofer support, they obviously can't do high or even moderate SPL. This is exactly how I get bass out of my desktop system. I relax the SPL requirement to about 70db max. So I do understand this.


It doesn't change the fact that a low tune with this driver will run it out and will have flabby bass. I've always said you may have had a good experience with your tuning because of what ever TL oopsies you made and your room modes. Given the room description I've heard from you, it makes sense the modes in your room could be helping things out. The OP has mentioned using these at his computer. A 53hz tune is going to be awful, yet an 80hz tune will actually be fairly satisfying. I'd personally go sealed at a desktop.
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Old 22nd February 2013, 05:44 PM   #30
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Wally,
Glad to see your enthusiasm and willingness to sponge up info! The graph shows an overshoot in response at the bottom end. This means you can adjust the tuning freq lower than the 90 Hz you set it at. The goal is to get as low as you can in frequency and have the response as flat as practical. A little overshoot is OK.

The TABAQ MLTL achieves its low frequency through "mass loading" which comes from a mechanical tuning fork analogy whereby if you add mass to the end of a tuning fork, its resonant frequency drops. In a "mass loaded" TL, you "add mass" by plugging up or restricting the output terminus (or vent). It really should be called a "Vent Constricted Transmission Line" or VCTL, but hey, I did not coin the word first so whomever did it, it stuck. If you wanted to achieve the same resonant freq in a straight TL with no constriction, it would be much longer. You can calculate the length required based on the speed of sound which is about 342 m/sec and how long a quarter-wave of sound moving at the speed of sound is at the frequency of interest. For example, a 55 Hz sound wave has a length of (1 sec/55)*(342 m/s)=6.22 m and 1/4 of that is 1.55 m or 61 inches. So you see that by constricting the vent output, can cut the length by a factor of two. Of course, decreased bass output efficiency is the trade-off. The stuffing is used to smooth out the peaks and valleys of the response due to the resonances in the TL. It also impacts efficiency so needs to be used sparingly, which is why the last 10 inches has no stuffing so that the sound pressure can travel unimpeded.

Hope this helps answer some of your questions, many of which Cogitech answered already.
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