Jordan JX92S questions? [message #14672] |
Wed, 11 August 2004 20:13 |
Norris Wilson
Messages: 361 Registered: May 2009
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Grand Master |
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Hi everyone, I have been looking at the Jordan JX92S transmission line project on the Jordan website. The only damping material shown to be used on their site, is felt behind the driver. I have not built a transmission line speaker before, but I thought that stuffing the line is important. Has anyone here built this Jordan design? If so, could you help with the proper stuffing material and quanity? Also, has anyone experimented or built a speaker system using mutiple Jordan JX92S drivers in an array or multiples of two or more? Possibly used multiple drivers with a modified varient of the transmission line project? And finally, has anyone been able to integrate a subwoofer successfully with the Jordan JX92S speaker? If so, what model or specific design worked well, DIY or commercial units, self powered or drone with active or passive crossover ect? The Seas 10" aluminum woofer looks like it could be a good match with the Jordan. Any and all help and sugestions will be greatly appreciated. Thanks Norris Wilson
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Re: Stuffing thickness [message #14677 is a reply to message #14676] |
Thu, 12 August 2004 06:35 |
Bill Fitzmaurice
Messages: 335 Registered: May 2009
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Grand Master |
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If the line is not completely stuffed throughout its length it will not perform as a transmission line; I'm not familiar with the design in question, but the lack of full stuffing makes me question it. A transmission line by dint of its design will develop a number of resonant modes throughout its length; it is critical that those modes be damped with stuffing or the response curve will be quite erratic. When properly stuffed a transmission line will have a smooth frequency response with no internal reflective modes and an impedance sweep will show a single impedance peak at the line frequency with no peaks anywhere else. Without adequate stiuffing it will exhibit numerous impedance peaks and the response will also be marred by a series of peaks and dips.
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Re: Jordan JX92S - I'm going to take a wild guess here... [message #14680 is a reply to message #14672] |
Fri, 13 August 2004 05:01 |
wunhuanglo
Messages: 912 Registered: May 2009
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Illuminati (2nd Degree) |
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After looking at the plans, I think it's a matter of "completeness". The plan says that the vented version is depicted. It also shows what changes to make to the woodwork to convert it into a transmission line. In the other plans shown, they talk about using long fiber wool compressed to half-volume. I think that what they neglected to say is that you need the same thing if you elect to go with the transmission line configuration in the cabinet you're looking at.
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Re: Stuffing thickness [message #14682 is a reply to message #14678] |
Fri, 13 August 2004 11:24 |
Bill Fitzmaurice
Messages: 335 Registered: May 2009
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Grand Master |
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There are some formulas for the amount of stuffing, according to the material, F3 and other considerations, but they aren't terribly precise. The best way to do it is to run an impedance plot. With no stuffing or insufficient stuffing you'll have one large peak at the Fo and a number of smaller ones above it, as I noted before. When a sufficient stuffing density is reached only the high spike will remain, with the rest suppressed, along with the resonances that caused them. With polyester pillow stuffing you'll usually find that sufficient stuffing to throughly fill the line without compresssing it is sufficient. A line with inadequate stuffing has not only ragged response but the roll off below Fo is at 12dB, the same as a vented box. Properly stuffed a line rolls off below Fo at 6dB, so you have the bass response at Fo of a vented box but the slower rolloff and cone control of a sealed box below that.
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