Tang Band Full Range Tuning Frustrations! - diyAudio
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Old 1st March 2013, 07:50 AM   #1
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Default Tang Band Full Range Tuning Frustrations!

Hey!

I felt that this topic would be better suited to the full range sub-forum since I decided to use a full-range home speaker, even though this is a car application. Additionally, I have been conducting extensive tests with a calibrated measurement microphone since first connecting my speaker to my Crown amplifier. If anyone thinks it should be in the car section though, you are welcome to move it.

Anyway, my Nissan 300zx originally came with four Bose speakers in special enclosures. The main defect here is that the individual amplifiers that power each speaker often fail and new speakers are usually cheaper than repairing the amplifiers. I had an expert on the Z forum install some Audax VP100z2 coaxial full range speakers in these enclosures, however I was never satisfied with the sound (these drivers break up at around 10khz and have a resonance frequency of around 100hz).

While my car was down for some work, I decided to replace a couple of the speakers with new Tang-Band W4-1052SDF's. I thought it best to test the first speaker in my room with my test equipment to reveal any problems. Although the speaker has not finished breaking in yet, I am rather dissatisfied with fidelity. Highs seem to roll off soon, however there is a nasty resonance at around 150hz. I took a screen shot of the last SPL sweep and RTA test that I conducted.

The port in this enclosure was approximately 12cm long when I checked last (along with a 90 degree bend) as well as 2.7cm wide. WinISD indicates that the port should be about this long in a rectangular box, however I do not know enough about this shape enclosure to make any conclusions. The enclosure appears to be about 2.5 liters in volume and I added a large amount of acousta-stuf. Also, I had to add a few layers of speaker gasket to the box and driver back to keep it from bottoming out.

What if anything should I try adjusting to remedy these problems? I'm most bothered by the peak at around 150hz and would love to move the boost to around 80hz. I am planning to add a subwoofer to take care of frequencies below 80hz, but I would like flat response from these speakers as far down as possible.

Here is a link to the driver that I am using:

Tang Band W4-1052SDF 4" Full Range Speaker 264-913

Attached are the screen shots!

Click the image to open in full size.

Click the image to open in full size.

Thanks very much for your help!
Attached Images
File Type: jpg tang-band 3-1-13.jpg (330.5 KB, 266 views)
File Type: jpg 2013-03-01 03.30.37.jpg (465.1 KB, 258 views)
File Type: jpg 2013-03-01 03.30.37resize.jpg (295.7 KB, 539 views)
File Type: jpg tang-band 3-1-13 resize.jpg (176.0 KB, 298 views)
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Last edited by techbiker; 1st March 2013 at 07:58 AM.
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Old 1st March 2013, 08:02 AM   #2
xrk971 is online now xrk971  United States
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What is the tuning freq in WinISD? The response doesn't seem to go very low considering the fs of the driver is 70 hz. On bass reflex enclosures, you want to line the walls with damping material, like a half in thick layer of carpet padding, felt, or polyfill but formed into a sheet batting and glued to walls avoiding blocking of ports. A 12 cm long port sounds awfully long. Did you measure the actual volume by water or displacement or is it estimated? It makes a big difference when total vol is 2.5 liters - kind of small. Ideal volume is much bigger - that's probably the main problem.

Edit: I just checked WinISD, the ideal volume is 6.5 liters with 3.4 cm long port if port is 2.7 cm. This will get you a nice flat response down to 70 or 80 Hz. If you stuff this driver into a 2.5 liter enclosure with the port you have it rolls off at 170 Hz. That peak you see at 150 Hz is the overshoot of a non ideal alignment of an undersized box. The shape of the box should not matter. Do you have room to mod the box to triple its volume and cut the port length down? It just looks like driver is mismatched to enclosure. This driver appears to measure quite flat and nice as Tang Bands mostly do in this category.

Last edited by xrk971; 1st March 2013 at 08:13 AM.
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Old 1st March 2013, 08:08 AM   #3
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Quote:
Originally Posted by xrk971 View Post
What is the tuning freq in WinISD? The response doesn't seem to go very low considering the fs of the driver is 70 hz. On bass reflex enclosures, you want to line the walls with damping material, like a half in thick layer of carpet padding, felt, or polyfill but formed into a sheet batting and glued to walls avoiding blocking of ports. A 12 cm long port sounds awfully long. Did you measure the actual volume by water or displacement or is it estimated? It makes a big difference when total vol is 2.5 liters - kind of small. Ideal volume is much bigger - that's probably the main problem.
The tuning frequency in WinISD is 67.17hz. I just stuffed the entire thing with polyfill, so I am most likely blocking the port. I will take the box apart tomorrow and try gluing all of the polyfill to the walls.

I also only estimated the displacement. I can remove the driver, fill it up with water, and see the exact volume. I will also measure the exact length of the port.

I agree with you that the box is quite small. Unfortunately though, until I can find away to build a larger enclosure, this is what I am stuck with. :/ I'm just trying to optimize performance without replacing the enclosure.

Thanks!

Edit: I could probably add another 2 liters to the box through modifications. I might have to glue on a cut plastic box? Do you think that this would get me close enough to a reasonable response?
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Last edited by techbiker; 1st March 2013 at 08:19 AM.
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Old 1st March 2013, 08:20 AM   #4
xrk971 is online now xrk971  United States
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Try this simple fix: seal the port as that would match ideal vol of 2.8 liters for this driver. It will tame that peak but you won't have any bass to speak of, fine if you have woofer to augment. Use stuffing in a sealed box. It's reversible and an easy check.
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Old 1st March 2013, 08:24 AM   #5
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I'll give that a shot!

Thanks again
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Old 1st March 2013, 08:30 AM   #6
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I would decouple ( = firmly couple ) the speaker with a 5mm aluminum baffle.
Plastic is something frustating, in audio.
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Old 1st March 2013, 08:43 AM   #7
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Pico, I'll definitely look at grabbing baffles! That should also help offset my speaker from the rear wall.

xrk- I stuffed a large amount of closed cell foam 2.5 inches deep into the port. I'm guessing that the port was already mostly blocked internally by the polyfill because I only saw a small reduction in that peak. The peak did fall by 2-3 db though and I cannot hear much of a resonance anymore.

I'm guessing that there is no way to keep this as a bass reflex enclosure without suffering from a large peak at around 150hz?

Thanks again

Click the image to open in full size.
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File Type: jpg port blockedcomparisonresize.jpg (118.1 KB, 288 views)
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Old 1st March 2013, 08:54 AM   #8
xrk971 is online now xrk971  United States
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That's not much of a difference which means your stuffing was blocking ports earlier. That box is probably resonating and mic is picking of secondary radiated sound from box walls. When mounted in car that will all be blocked. Try covering box surface with something to simulate car panels or dashboard. You can also try smaller driver like 3 in instead of 4. May need cutout adaptor.
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Old 1st March 2013, 03:47 PM   #9
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Well, that's not how you measure a speaker. It is neither anechoic / reflection free, nor is it in it's intended position (the car). That 150hz peak could very well be related to a number of reflective surfaces surrounding the speaker in its current position.
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Old 1st March 2013, 04:05 PM   #10
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Also the box: is that needed ?
Since the purpose of a box is to separate the front wave from the back wave, by removing it you just let the sound escape in all directions. You can control it by adding some stuffing behind, but pricipally you have to take care of all the resonances of all the
different panels & different materials. I think that the purpose of a plastic box is mainly to prevent moisture attack to the metallic parts of the speaker .
I frequently use tar+waste foils from automotive shops to 'damp' the internals of a cabinet
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