Re: answers to question and such
Where do you put the stuffing? And is it necessary to use eggcrate foam (or a similar stuffing) behind the driver in the upper part of the TL?
The TL that is described on the Jordan site, they only put damping material behind the driver. The transmission line itself is empty.
I am not very familiar with loudspeakers working on the TL principle...
Marc
stokessd said:
Where do you put the stuffing? And is it necessary to use eggcrate foam (or a similar stuffing) behind the driver in the upper part of the TL?
The TL that is described on the Jordan site, they only put damping material behind the driver. The transmission line itself is empty.
I am not very familiar with loudspeakers working on the TL principle...
Marc
Dave,
Rumor has it that you have a D'Appolito Jx-92 design. Time to come clean.
Jam😉
P.S. JasonL and I want to know...
Rumor has it that you have a D'Appolito Jx-92 design. Time to come clean.
Jam😉
P.S. JasonL and I want to know...
jam said:
Not MTM, but bipoler (or bipolar 0.5 way). The recipe can be applied to almost any enclosure where you have a well sorted single driver box.
Double the volume appropriately (in a quarterwave design this means doubling the cross section), do any gymnastics necessary to mount the drivers so you can pysically couple them, and mod any vents as necessary.
With JasonL we never got down to discussing the particulars. In the case of the Jordan i'd use something like BrianGT's ML-TQWT or a TL if i needed max bass extension or a leaky sealed box (aperiodic) if it was being used with stereo woofers.
Some examples of a specific bipolar ML-TQWT convesion -- the dimensions would need adjustment for the JX92.
An externally hosted image should be here but it was not working when we last tested it.
or you could just do the trick shown below.
dave
Attachments
Re: Re: answers to question and such
I used a total of 6 oz of polyfill, about one ounce or so went in the cavity behind the driver. After stuffing that cavity, I scientifically talked into the cavity and made sounds with my mouth (I'm glad the dogs were the only ones there to observe that portion of speaker enclosure design) until I was satisfied that it was reasonably dead back there.
Sheldon
zeno said:
I used a total of 6 oz of polyfill, about one ounce or so went in the cavity behind the driver. After stuffing that cavity, I scientifically talked into the cavity and made sounds with my mouth (I'm glad the dogs were the only ones there to observe that portion of speaker enclosure design) until I was satisfied that it was reasonably dead back there.
Sheldon
Re: Re: Re: answers to question and such
I was talking to my professor today at school, and he had a student do testing with different stuffing materials for a special topics course. He tested egg crate foam from PE, acoustic-stuff from PE, polyfil, pink panther insulation and a couple other types. The end conclusion was that pink panther insulation worked the best... I have never tried it. The Acoustic-stuff was next, followed by regular polyfil. The egg crate foam was last. I didn't get the exact details of the test. They also tested the effects of stuffing making a smaller box seem larger, which the conclusion was that yes, it does make the box appear larger, but not substantially.
I also tested the response of my ported jordan JX92s speakers, and without the shelving filter (i shorted it out), they measured perfectly flat (microphone 1" from speaker). With the filter attached, the bass region was boosted (actually, above the region was attenuated). Dr. Leach thought that the bass was too boomy with the filter attached, and preferred it without it. He also felt that the highs were quite lacking in the JX92s driver, and comparing it to his speakers, it was noticible. I pulled the speakers farther from the outside walls, and the bass was a bit better. I think that I will reduce the shelving effect on my Jordan JX92s. After more playing, the bass almost has too much presence for my tastes. I might rework my baffle step compensation again. I wonder if the 1 1/2" roundover has any effect on this.
I am going to try stuffing a speaker with pink panther insulation and compare it to polyfil 🙂
--
Brian
stokessd said:
I was talking to my professor today at school, and he had a student do testing with different stuffing materials for a special topics course. He tested egg crate foam from PE, acoustic-stuff from PE, polyfil, pink panther insulation and a couple other types. The end conclusion was that pink panther insulation worked the best... I have never tried it. The Acoustic-stuff was next, followed by regular polyfil. The egg crate foam was last. I didn't get the exact details of the test. They also tested the effects of stuffing making a smaller box seem larger, which the conclusion was that yes, it does make the box appear larger, but not substantially.
I also tested the response of my ported jordan JX92s speakers, and without the shelving filter (i shorted it out), they measured perfectly flat (microphone 1" from speaker). With the filter attached, the bass region was boosted (actually, above the region was attenuated). Dr. Leach thought that the bass was too boomy with the filter attached, and preferred it without it. He also felt that the highs were quite lacking in the JX92s driver, and comparing it to his speakers, it was noticible. I pulled the speakers farther from the outside walls, and the bass was a bit better. I think that I will reduce the shelving effect on my Jordan JX92s. After more playing, the bass almost has too much presence for my tastes. I might rework my baffle step compensation again. I wonder if the 1 1/2" roundover has any effect on this.
I am going to try stuffing a speaker with pink panther insulation and compare it to polyfil 🙂
--
Brian
Member
Joined 2002
Brian-
what does Prof Leach use for speakers?
I agree that the top two octaves or so of the JX-92 aren't the best, the FR plots look more like Colorado than Iowa. I'm still working on my minimite design which mates the Jordan in a TL with a small ESL panel which will take care of that upper octave problem nicely. I might even try to make the ESL play down to 250 Hz or so.
WRT the baffle step compensation filter. I made mine variable VIA my stepped inductor so I could turn it off or slowly add it in as necessary. I doubt that your roundover has a lot to do with it, it's mainly a function of your smallest front baffle dimension. I leave mine off when the TL's are a foot from the back wall, and put it at 1.5 mH when they are 4ft into the room. the TL's are at a friends house, and I have to listen to my SWEET electrostatic speakers instead...Oh the pain. 🙂
Sheldon
what does Prof Leach use for speakers?
I agree that the top two octaves or so of the JX-92 aren't the best, the FR plots look more like Colorado than Iowa. I'm still working on my minimite design which mates the Jordan in a TL with a small ESL panel which will take care of that upper octave problem nicely. I might even try to make the ESL play down to 250 Hz or so.
WRT the baffle step compensation filter. I made mine variable VIA my stepped inductor so I could turn it off or slowly add it in as necessary. I doubt that your roundover has a lot to do with it, it's mainly a function of your smallest front baffle dimension. I leave mine off when the TL's are a foot from the back wall, and put it at 1.5 mH when they are 4ft into the room. the TL's are at a friends house, and I have to listen to my SWEET electrostatic speakers instead...Oh the pain. 🙂
Sheldon
stokessd said:
He has these
http://users.ece.gatech.edu/~mleach/labsp/
that he uses in the Audiolab, and he has a different pair of smaller 3 ways with Vifa components in his office that he uses all day.
--
Brian
Re: Re: Re: answers to question and such
Sheldon, do you 'spread' the stuffing throughout the whole transmission line? Or do you put most of the fiber in the front part of the TL?
My prototype of your design is ready and I tried it without any stuffing and the baffle not glued yet. Boomy thing with bad highs... of course!
Thanx!
Marc
stokessd said:
Sheldon, do you 'spread' the stuffing throughout the whole transmission line? Or do you put most of the fiber in the front part of the TL?
My prototype of your design is ready and I tried it without any stuffing and the baffle not glued yet. Boomy thing with bad highs... of course!
Thanx!
Marc
stokessd said:
It sounds like a very interesting design although I wonder if you'd be better off taking the strain off the ESL panels by taking the JX-92s up to about 5kHz or 6kHz. You'd still have the crossover frequency out of the "danger zone".
Sheldon, I think that the great, unanswered question here is: how big are the dogs? If they're large dogs with a deep bark, can you train them to 'scientifically talk into the cavity'? They may go lower than you can.
I think you've hit upon a fundamental principle of speaker design here ... cats for listening, dogs for testing.🙂
Steve
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