Some basic questions about Pi web site and speakers: [message #49847] |
Thu, 10 August 2006 16:41 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Greggo
Messages: 36 Registered: May 2009
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Baron |
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1) Are the prices per pair or per speaker, couldn't find any reference on the web pages? 2) Is there a way to convert box volumes for an aperiodic or sealed alignment that would only affect the lower end roll off of the woofer but not disturb the midrange and transition to tweeter that your crossover is designed for? 3) Do your speaker plans, such as the Pro 3, include crossover designs and if so, do you sell any of the components or recommend a source for such? Thanks, and I promise not post any more questions for at least 48 hours. Greggo Asheville, NC
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Re: Some basic questions about Pi web site and speakers: [message #49850 is a reply to message #49849] |
Fri, 11 August 2006 11:21 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Bill Wassilak
Messages: 402 Registered: May 2009
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Illuminati (1st Degree) |
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Let's see if I can explain this right. Lets say you have a long excursion 15" woofer operating in a range of 50 to 1Khz with flat response. Then you drop the frequency down to say 25hz well the IMD will go up in the frequency range of 500-1Khz because the lower frequency will start modulating the upper octaves of that operating range. Hence higher intermodulation distortion from 500-1k. Simple explanation, it's like when you yell into a fan it modulates your voice. Bill W.
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Intermodulation, phase and Doppler distortion [message #49852 is a reply to message #49851] |
Fri, 11 August 2006 16:59 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18756 Registered: January 2001
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Illuminati (33rd Degree) |
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Intermodulation distortion is actually caused by two things, each being somewhat related and both involving excursion. One is Doppler distortion, where the cone is moving back and forth from a low frequency tone so a higher frequency cone movement must ride upon this shift, which causes a phase shift. The other is a non-linearity caused when the driver is pushed nearing or exceeding Xmax, where the voice coil has less drive force because it partially moves out of the gap. This causes it to become non-linear at high drive levels.One way to reduce IMD is to reduce bandwidth, so if you crossover the woofer to mid at a lower frequency, you'll reduce IMD. I don't really notice it unless excursion is high, so if you're not pushing a midwoofer too hard, it isn't generally a problem. But if you are pushing a subsystem far enough that IMD becomes noticeable, the best way to solve it is by reducing bandwidth. Either crossover the lower point higher or the higher point lower, or both.
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Re: Intermodulation, phase and Doppler distortion, and then some [message #49855 is a reply to message #49852] |
Sat, 12 August 2006 01:02 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Bill Wassilak
Messages: 402 Registered: May 2009
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Illuminati (1st Degree) |
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Wayne, I don't agree with the phase shift theory's because you can't hear phase shift unless there's significant time delay's involved,so I don't agree with this: ::a low frequency tone so a higher frequency cone movement must ride upon this shift, which causes a phase shift. At a certain point the higher frequencies depending what they are, are ethier going to add,subtract or cancel(within the harmonics of the lows, at certain frequencies and x-over points) causing peaks or notches in the overall operating band width of the response. Isn't this modulating (the highs am style, aka IMD) In a limited bandwith the response with respect to the lows?? This statement I some what agree with: ::The other is a non-linearity caused when the driver is pushed nearing or (not really) exceeding Xmax, :: where the voice coil has less drive force because it partially "moves out of the gap.(bad news unless your hitting the bottom plate and/or sliding V.C.back into the front of the gap) This causes it to become non-linear at high drive levels.(TRUE). Dont, worry because power compression will set in long before hand which will reduce your output 3-7 db because of voice-coil heating. Even though your amps are at full power and not clipping, so don't boost your lows if you think there lacking. Time to get off of here,Mr.Seagrams is calling(so I maybe full of s__t) Not sure though.
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Crosspost (from diyaudio.com) you may find interesting... [message #49862 is a reply to message #49852] |
Sun, 13 August 2006 11:59 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) |
Greggo
Messages: 36 Registered: May 2009
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Baron |
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Regarding the sub design, have any of you guys looked at these commercial designs and attempted to think through if there is something of merit here or not. The first one is Zu Cable's Definition, which seems to follow the "keep cone resonance above pass band" philosophy for there integrated subwoofer, though the use a small sealed chamber for all 4 of those Eminence drivers... http://www.6moons.com/audioreviews/zu2/definition.html The second one that I find even more interesting is the Escalante, which uses compound loading and staggered crossover points, low passing the rear (internal to the cabinet) driver around 80hz and then letting the front driver run well up into the midrange... and claiming that this creates an environment for the front driver to have a controlled resonance of sorts and thus lower distortion and dramatically improve the rise time of the drivers response: http://www.positive-feedback.com/Is...nte_fremont.htm I normally don't pay much attention to the HiFi press or commercial markets as I am slowly moving towards a mostly DIY system, but these two systems really got my curiousity up and the reviews are both a fun read. So the last one got me thinking, instead of taking on the whole mid dome instead of whizzer engineering for super extended range from the woofer, is it possible to take the framework of Scott's design, and compound load a second B&C 12TBX100 in front of it and run it all the way up to 90hz or even up to 3-600Hz depending on your overall system design goals and the other drivers involved. Thinking about Scotts take on the frequency ranges that constitute hall valume, slam, punch, etc... wouldn't it be nice to have a stereo pair of bass towers that cover it all before handing off to an upper-bass/lower-mid driver in another cabinet that starts the final stage of the journey to a full range system. Of course, that's if there is something to Tierry's patents worth cloning (for our own, non-commercial use of course). Anyways, these two products and their accompaning reviews/descriptions/patents go into territory I have not seen discussed on the various diy forums before, most of the time these things are a big yawn for me and I much prefer the forums, these two struck as worth looking at as closely as possible. Regards, Greg Jensen Asheville, NC
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