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Midwest Audio Fest

It’s that time audio enthusiasts!

Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project.
We are excited to see all returning participants, and look forward to meeting some new designers this year, as well!

Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans.

We hope to see you this summer!

Vivian and Jill
2 of 2 < >

Midwest Audio Fest

It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Dayton DS90-8 driver does not measure up

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  • Dayton DS90-8 driver does not measure up

    I have a problem with the portable Bluetooth speaker I am building at the moment. I have measured the speakers and that endeavour has been documented in another thread. However, I feel the problem I am having now is too far removed from the initial problems I have documented in the other thread an that they warrant a new one.

    To describe my problem. I have build a Bluetooth speaker using the Dayton DS90-8 and the Dayton ND16FA. I have just started doing measurements of frequency response and impedance response. From my measured responses I have found a quite large discrepancy from my simulated response for the DS90-8 in VituixCAD and my actual measurements.

    I have made a bass reflex enclosure, and to add more confusion Parts Express recommends two different enclosure volumes for the DS90-8. One of the recommended volumes is 3.39 l (0.12 ft3) and a port of diameter 2.54 cm (1 in) and length of 15.2 cm (6 in). This is supposed to give an f3 of 73 hz. On the other hand, a volume of 1.41 l (0.05 ft3) with a f3 of 80 hz is also recommended. Port diameter and length is not specified for this enclosure volume.

    My Bluetooth speakers is made of two separate chambers with a volume of 1.56 l (0.055 ft3) and with a port each with a diameter of 2.4 cm (0.95 in) and length 11 cm (4.3 in). The simulated response of this enclose gives is:
    • fb = 82 hz
    • f3 = 80 hz
    However, my measured response of the driver in this enclosure gives:
    • fb = 113 hz
    • f3 = 115 hz
    This is far from the measured response. So I though that since the product information page gave two different recommended enclosure volumes, then perhaps the T/S parameters on the product page was wrong and the driver had been updated without updating the information. So I measured the T/S parameters of the DS90-8, but they were quite similar to the product specs. Of note is that I have not broken in the driver.
    Parameter Manufacturer Measured
    Sensitivity 84.1 dB @ 2.83V/1m 82.9 @ dB 1W/1m
    DC Resistance (Re) 6.3 ohms 7.35 ohms
    Voice Coil Inductance (Le) 0.56 mH @ 1000 hz 0.312 mH @ 2643 hz
    Resonant Frequency (Fs) 81.4 hz 79.2 hz
    Mechanical Q (Qms) 2.19 2.78
    Electromagnetic Q (Qes) 0.53 0.58
    Total Q (Qts) 0.43 0.48
    Diaphragm Mass Inc. Airload (Mms) 3.8 g 3.96 g
    Mechanical Compliance of Suspension (Cms) 1.02 mm/N 1.018 mm/N
    Surface Area Of Cone (Sd) 31.2 cm² 31.2 cm²
    BL Product (BL) 4.76 Tm 5.01 Tm
    Compliance Equivalent Volume (Vas) 1.31 l 1.43 l
    Driver's Mechanical Losses (Rms) -- 0.709 kg/s
    Here are some pictures of the enclosure I have build from the front and the back.

    Click image for larger version  Name:	image_79000.jpg Views:	1 Size:	85.8 KB ID:	1409450Click image for larger version  Name:	image_78999.jpg Views:	1 Size:	80.3 KB ID:	1409451

    Here is a graph of the simulated and measured impedance of the DS90-8.

    Click image for larger version  Name:	Dayton_Audio_DS90-8_Impedance.png Views:	1 Size:	25.0 KB ID:	1409453Click image for larger version  Name:	impedance_ds90-8_ported.jpg Views:	1 Size:	57.9 KB ID:	1409452

    The discrepancy between the simulated and the measured responses I find very frustrating. For the past year I have been reading up on the theory behind loudspeaker construction. It is one of the hardest subjects I have tried to teach myself. And it is made even more frustrating if I can't trust my simulations to give me a design which will perform similar to my simulations in real life. Any input or suggestions to solve this is much appreciated. If you need ny more info I will gladly supply it if you ask me in a post.
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