Tang Band W5-704D + Dayton PT2C

Referene Thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=96352

I finally ordered by W5-704D's from Parts Express. I caught them on sale as the Deal of the Day.

I have measured them with Speaker Workshop. I think it went well, except for I could not get VAS on the second driver, just came up blank or a really low number that rounded to zero.

Attached are the results. My Fs came out a little higher then Zaph's and Tang Band's.

I plan on doing the design with FRC tools, except for the woofer measurements (complete) and the inbox impedance/phase (which will be done with Speaker Workshop). I will start the design "from scratch", again.
 

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Plan is a ported enclosure, 20-Liters, Fb = 45 Hz w/ (2) 1.5" ports that I hope to fit on the front baffle. Assuming 3 dB of BSC since these will be a bureau.

In my reference thread, someone mentioned that even though the response looks flat, it will be boomy. Any comments on this design? Still a concern?

Max. excursion is hit with only 5-watts. I am assuming about 3 db of boundary gain, so approx. 90-dB of output @ 1 meter.
 

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I quickly modeled a low pass filter for a single TB W5-704---the old 704S version has the same response as the new 704D. I used an in-box modeled response that was used for my 2.5-way design:

http://www.diyaudio.com/forums/showthread.php?postid=1422714#post1422714

Your baffle will be different from this, but the effect due to different baffles should be minimal. Mine is a sealed design. So, ignore the response below 200 Hz.

The target is LR4 4 kHz.
 

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Thanks Jay- the LR4 @ 4k Hz looks promising. I am surprised you got full BSC without a LR filter. My original attempts failed at this....encouraging.

I want to cross over to the Daytons high to avoid some of the distortion issues below 4 kHz.

I agree, a sealed version crossed to sub would be a nice design. Mine are slated for a bedroom...no subs allowed.

P.S.- The lower tuning also moves the sub-Fb over excursion below 40-Hz, which i like.
 
Hi,

20L box with driver of Vas = 8L, Fs = 62Hz, and Qts = 0.6 ?

It will work but this is no way to extract the best performance out
of a box that size, a bigger driver is required. Whenever the box size
exceeds 200% of the driver Vas you are usually wasting your time.

Sealed is the obvious way to go, 7L to 10L well stuffed.
Comparatively no bass, but it will not overload easily.

If you must reflex, probably 13L tuned to 40Hz is about right.
Tight bass you will not get, 20L will probably sound even looser.

Allegedly higher Qts drivers can be made to work in stuffed TL's,
but MJK's worksheets I've not got into and got to grips with.

:)/sreten.
 
Yes, no doubt power handling will be an issue. When we consider BSC, a single speaker's max SPL will be 88-89 dB at 1 m. This limitation won't improve much even when a 13-14 liter (.5 cu ft) box is used for a single driver. In fact, the idea of using a single TB W5-704 for full range, whether vented or sealed, will result in having this problem, though sealed is better, of course.

So, the bottom line is 1) use it in sealed with HP filter and a subwoofer or 2) admit this limitation and use it only for moderate level listeninig. Or use multiple drivers. IIRC, he already admitted the limitation. So, it's up to him.
 

augerpro

Member
2006-08-27 11:02 am
Sreten just FYI: most of us have being measuring about 11-13L Vas and .45 Qts

It's very important with this driver to consider it's final use, whether HT, music, maybe music with pipe organs etc. If you can cross to a sub then no worries. With a 80 Hz crossover you can run 32 watts at Xmax, with a 60 Hz you can run 16 watts at xmax. You could also run without a sub if your receiver has a very low XO setting, say <40 Hz. That way you could get mostly the same bass response >50 Hz where the music is, but still protect from over excursion down low.

If you are using these for music with no sub I don't think you will need to tune too low and reduce power handling. Personally I'm going to use 15L tuned to 50 Hz. Higher power handling and excursion is lower above 45 Hz. Below 45 Hz it's worse, but most music doesn't have much info that low. I think the 20L tuned to 45 Hz would also be a decent alignment. I'm using pre made 15L boxes so I didn't choose that one.
 
augerpro said:
If you are using these for music with no sub I don't think you will need to tune too low and reduce power handling.

As you can see in the above sims, there's no significant difference in power handling between 39 and 45 Hz tuning. So, the tuning freq choice should depend on personal preference, not much on power handling (very low in both cases).
 

augerpro

Member
2006-08-27 11:02 am
At the same volume a 5 Hz difference won't make much difference, you're right. I was comparing two alignments that were a bit more different though. Here is a comparison between 15L @ 50Hz (black) and 20L @ 40Hz (red), both at 8 watts input:


equalpower.jpg



As you can see the smaller/higher tune is actually moving 1-2mm less from 50Hz to 65Hz, not insignificant considering xmax is rated at 3mm. And that's the meat of music based bass. Actually the larger/lower tune is slightly past xmax. Here is with xmax equal, which required dropping input to the larger/lower tune box to 6 watts:

6watt_8watt.jpg



Below 45Hz is where the smaller/higher tune box falls behind. If that's not problem due to how the speaker is used, I think the smaller/higher tuned box has the advantage.Now I'm making two big assumptions here: that the smaller/higher tune box won't sound boomy (and vice versa for the larger box) and that there isn't much music content below 45 hz. So that's the big dilemma 69stingray has to answer for himself. The lower tune may very well sound better in his room, and using it for HT or orchestras without a sub would probably require a lower tune also. This is a tough one since you need all the power handling you can get, considering sensitivity after BSC.
 
Of course, there should be some difference in power handling if you compared 40 Hz Fb in 20 liters to 50 Hz Fb in 14 liters. But as your sim shows, in this case, there should also be a significant difference in the bass rolloff. Depending on the speaker placement, 50 Hz Fb in a 14 liter box can sound boomy due to the midbass peak. Using a Zobel circuit and a lower DCR iron core will mitigate the problem a bit. My sim assumed .4 ohm series resistance and Zaph's T/S measurements were used.
 

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So that's the big dilemma 69stingray

Yup. No HT or loud orchestras passages ;) Bedroom bookshelf speaker. They will be on a bureau, right up against a wall.

Thanks for all of the options, I will have to ponder this some more.

In regards o BSC, I was thinking 3 dB, but since they will be sitting on a bureaus, next to a wall, would no BSC be appropriate?
 
Hi,

According to Zaph no BSC is hardely ever appropriate, usually this
means corner or corner & ceiling placement and you have thrown
away most of the the ability for the speaker to sound good.

Zaph's reduced BSC versions do not reduce it by much.

Also FWIW I'd say maximum tuning frequency of a vented box should
be around 44Hz, bottom E on a bass, but the lower the better IMO,
around 31Hz, bottom B on a piano is preferable, if possible IMO.

Another FWIW is that Vas is a small signal phenomena and for large
signals it is anything but linear, causing odd harmonic distortion, any
assymetry causes even harmonic distortion. There are other issues
e.g. voice coil offset etc. to also consider......
Conversely the air in the box is comparatively extremely linear and
the more this dominates the more linear the speaker is by default.
A 15L vented box should have a suitable driver with a Vas of around
30L for clean bass, such a driver (usually 6.5") will be far superior
in the bass end than a lower Vas driver, for the reasons given.

Vas = 12L and Qts = 0.45 is more workable than 8L and 0.6.
Fs ? lower due to higher Vas ? guesstimate = 45Hz.
for 15L best tuning frequency = 33Hz IM0, max IM0 37Hz.

(Using WinISDbeta, not as accurate as Unibox)

:)/sreten.