U frame woofers for TD15S? - diyAudio
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Old 18th November 2010, 07:40 PM   #1
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Default U frame woofers for TD15S?

I keep reading posts about U frame woofers and wondering if I can implement such a design with my drivers. And, if so, what steps do I take to implement the design. I currently have them sealed so I want to simulate the outcome rather than build new cabinets as a trial.

The drivers I have are the TD15S. Specs as follows. I want to run them from 60-70Hz up to 300-320Hz. I want to run a pair a side. Is this only practical in a U frame if I have them vertically stacked or can they be horizontally stacked? How do I know what difference this will make? Should the U frames be separate for each driver? How will I know in advance what response I can achieve? Also, how do I know whether the drivers themselves are suitable for a U frame? How do I know the size of the U frame?

I figure there are a lot more questions I need to ask but this is it in a nutshell. Many thanks in advance for advice.

TD15S- 8ohm
Fs 22.8 Hz
Qms 3.87
Qes 0.41
Qts 0.37
Vas 467 Liters
Cms 0.45 mm/N
Mms 108 grams
Sd 855 cm2
Rms 4.0 Kg/S
Bl 14.1 T/m
Re 5.3 ohms
Z 8 ohms
Le 0.3 mH
Pe (max) 500 Watts
Pe (transient) 1000 Watts
"no" 1.31 %
1WSpl 93.4 dB
Linear Xmax 14 mm (peak)
Mech Xsus 20 mm (peak)
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Old 18th November 2010, 10:54 PM   #2
djn is offline djn  United States
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The Qts on those is only.37. That is a bit low for OB. These sound great in a ported box though. For "U" or "H" frames, look at something that has a higher Qts like the Alpha 15a.
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Old 18th November 2010, 11:03 PM   #3
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See these pages


Gradient woofeer equalization
NaO U-frame
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Old 19th November 2010, 01:19 AM   #4
CLS is offline CLS  Taiwan
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Low Qts is not a problem for OB, if you're willing to change the Qes by increasing the output impedance of the amp.

Search "driven by current source", "transconductance amp"... etc.

TD woofers got very good reputation, with plenty of Xmax, no reason to avoid using it on OB. There're solutions.
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Old 19th November 2010, 09:21 AM   #5
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Low Qts is not a problem with that low Fs either. Note that Linkwitz chose Peerless woofers with Qts as low as 0.17 in the Orion dipole speaker.
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Old 19th November 2010, 10:55 AM   #6
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Quote:
Originally Posted by CLS View Post
Low Qts is not a problem for OB, if you're willing to change the Qes by increasing the output impedance of the amp.

Search "driven by current source", "transconductance amp"... etc.
.
I am investigating driving a woofer in this way and have a few questions. How much effect can we have on the response of the woofer by changing the Qes. What effect will this have on spl level and Qts. Is it possible to get a reponse level that would alleviate the need for a second woofer in a dipole setup? If possible could you give examples. I am building an F2 amp that i plan on converting to F2J, for the purpose of driving both a fullrange set of speakers as well as possibly biamping a dipole setup.
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Old 19th November 2010, 11:12 AM   #7
CLS is offline CLS  Taiwan
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For your reference: Low Q Woofer in OB with High Zo Amp

I wrote all I know about this in that thread. And there's a spread sheet for calculating (forecasting) the result. Might be useful.

This is just a method to tune the system Q. And system Q is only one of the factors for designing an OB bass. How it perform at extention or SPL is still directly connected to the baffle size and total displacement of the woofer(s).

Low Q woofer driven by amps with high output impedance is out of the 2 major camps in OB system designs (high Q woofer or low Q woofer + EQ). It's a pitty not many have tried this and I got very few feedbacks.
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Old 19th November 2010, 12:15 PM   #8
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Low Qts or High Qts, the SPL capability is dependent on excursion and area. Qts basically represents the efficiency of the woofer around Fs compare to the efficiency in the mass controlled region. A dipole response simply superimposes a 6dB/octave roll off on the woofer's nominal monopole response.
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Old 19th November 2010, 02:40 PM   #9
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Looking to do a current driven OB experiment soon with woofer/fullrange combo. Although I will be able to compensate for baffle rolloff, will there be phase alignment issues? Forgive all the questions bit I am a been.
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Old 19th November 2010, 02:42 PM   #10
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Newbie! Not been.
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