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)
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)
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.
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.
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.
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.
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.
For your reference: http://www.diyaudio.com/forums/multi-way/155022-low-q-woofer-ob-high-zo-amp.html
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.
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.
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.
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.
John,
I nioticed something interesting while reading on your site. The spl response of your NaO Notes is more similar to a typical musical response than those of many speaker sytems which try to create a perfectly flat response. I assume this was intentional. I wish I could buy your sytem just as a reference point. What is too small a room for your setup? My room dimensions are 16 x 14.
I nioticed something interesting while reading on your site. The spl response of your NaO Notes is more similar to a typical musical response than those of many speaker sytems which try to create a perfectly flat response. I assume this was intentional. I wish I could buy your sytem just as a reference point. What is too small a room for your setup? My room dimensions are 16 x 14.
16 x 14 would be acceptable. You have enough width to keep the speakers 2 to 3 feet from side walls and 3 to 4 feet from the wall behind them. If you figure an equilateral triangle set up with the speakers 8 feet apart the listening distance would be 7 feet which would still allow sufficient distance behind the listener. If the speaker were 10 feet apart the listening distance would be about 9 feet. This would still leave sufficient room behind the speakers and listener.
Thanks John, I have been trying to make meaning out of all of those equations, and thanks CLS. I will give the spreadsheet a go! I have a WT3 so I can use actual data. I'm not going to change my amp but I will see what I can learn. I feel like it would be great if there was a 'super' spreadsheet to crunch all the data and spit out the answers. Maybe that's MJKs worksheets 😀
For both the woofers and the panels I recommend 100W/8ohms. The panel amps should be comfortable with a 4 ohm load.
I have powered them with a variety of amplifiers including my older Threshold 400A (100W/8, class A), some Adcom 125W/8 (class A/B) and just this morning I have been listening to them using a pair of amplifiers from Class D Audio (125/8 class D) I just assembled. All seem to work just fine.
John,
does your software allow for phase and power alignment? I know you speak extensively about both in your articles. I guess i am asking if the modeling of those parameters is included or is this something you did independently in another program.
does your software allow for phase and power alignment? I know you speak extensively about both in your articles. I guess i am asking if the modeling of those parameters is included or is this something you did independently in another program.
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