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Topic: Jeffrey Jackson

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Posted by Romy the Cat on 09-19-2005

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In reference to:

http://www.goodsoundclub.com/TreeItem.aspx?PostID=1414

I had recently a guy in my listening room and he asked me if it would be possible to get the 300Hz range in the way how it sounds in my room but without using those larger upper bass horns.

I was laughing and replayed that THAT was what the whole game all about. I do not know any ways to reduce upper-bass, or what Clark called “the melody range”, properly besides a straight radiation horn with a small throat when the horn do not load as a direct radiator even an octave or two before the “the melody range”. Still…, the narrow throated, straight, upper-bass is a big and in many instances not manageable. So, if anything out there could compete with what a horns does with upper bass? Let pretend that the horn loading does not exist, then what would be the next in succession line?

Ironically, among all enclosures and topologies that I have heard I found that a properly done bass-reflex enclosures can do the  “the melody range” quite adequately. What, the ported speakers? Are you out of your mind, Romy? This what you are proposing after the years of bitching about the “ported sound”? Yes, I do. Here is what I mean….

If a port is properly implemented then the port might do a phenomenally good upper-bass, almost as good as a “horn-loaded” upper-bass horn. The problem is that NO ONE uses the ported design properly. If do not let the ported design to go all the way down and to cut off the channel very slightly lower then the port begin to EQ the bass then it is possible to get a very-very good Sound using the bass-reflex enclosure. Paradoxically the driver in this case should be not really “ported” and an extra one or two LF channels would be mandatory for the lower octaves but with all those incontinences we gain “quality” of sound… using a port. A typical cut off of a bass-reflex enclosure in order to work properly should be somewhere around 110Hz-180 Hz and it done so then the “ported sound” does not manifest itself at all. Quite in contrary, the properly done bass-reflex might be very live, very dynamic and very musical.  Listen for instance the Wilson Alexandria’s high- passed upper bass – it absolutely extraordinary but let the speaker run full-range and the Alexandria’s ported lower and mid-bass will screw everything up. The only one problem that I can see with properly done port channels that they are effective only in a VERY narrow bandwidth. Bring frequencies too low and the noise form the port compromises the entire “melody range”. Bring it too high that the driver being to sound like an open baffle….

I did not see anyone even tried to do what I proposed above commercially. There was an old model of Kharma Audiocratique that had two bass sections; one of them was sealed another was ported:

audiocratique.jpg

The Kharma sentiment was correct but it unfortunately was not done properly: the ported channel went too low and the sealed channel was too week – a wrong driver and not enough volume of enclosure. Still it is the only one known to me commercial attempt to deal with the ported upper bass in more sensible way then it done usually.

Rgs,
Romy the Cat


Posted by mats on 10-02-2005

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Trying to explore the upper bass channel reaching up to a Victor Sierra 360 Hz horn with an Altec 804 with a 4 uF oilcap, I first used my OB Supravox 215, then a B&C 8" woofer in a large BR originally used with EV 15"  (the latter not good) and finally an Oris 150 with either B&C or my preferrence today: the Supravox field coil.

I ended up liking a 1,6mH coil on the upper bass drivers, making for  long knees.  There are obviously way too many variables here, and I am aware of the limitations of the 21" OB bass channels.  Still, with a separate volume control for the 360 Hz horn and its T90A with 0,3uF cap tweeter and volume and crossover freq. control on the bass channels I was able to "dial in" a reasonably interesting sound.  I have yet to try the proper implementation of "BR melody range" as described above. 

Mats


Posted by Romy the Cat on 10-02-2005

Mats,

Actually I do not exactly understand what you are trying to accomplish. The Altec midrange after 4uF will roll at 3.5kHz-5.0kHz, depending of the type of coil you use. If you cut the MF channel so high then I would ask why you do so and why you in this case use so deep horn for the Altec?  I personally can see in you installation two extra channels that I can’t figure out what they do. You might eliminate for this setup two horns and you will have multiple benefits if you do so. BTW, the eliminate of the horizontal bias between the drivers will be quite important one…

Rgs,
Romy the Cat


Posted by mats on 10-02-2005

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Hi Romy,
 
I think my post is a little confusing.
The picture shows all the different drivers
used in these experiments.  The Altec in wood
horn is the constant with the
the 21" bass channel. Then I bridged the
bass to the Altec using the four different
setups: 
1: Supravox on open baffle  (placed near the Altec)
2. B&C in large BR
3  B&C in Oris 150
4.  Supravox in Oris 150
 
I could certainly lower the crossover point on the Altec.
The horizontal bias too is a problem,
The Oris 150 gives perhaps
a little taste of upper bass.

Mats
 

Posted by Romy the Cat on 10-03-2005
I never was fan of the Oris 150. They meant be used with Lowther type of drivers, that never worked properly. The Oris 150’s upper bass is not really the bass that might be obtained form the Oris’ mouth. Should this Oris has twice smaller throat and be twice deeper then it would EQ the lower knee and will be able to produce some kind of loading effect, although then the Oris should have 4 time thinker walls…  Sure, in that case the folks who punch Oris’ would not be able to sell them to thier customers those Lowthers and AESs, that would defeat the peruse of the Oris from thier perspective… Try to drop the Altec in 400Hz horn down to 1000 Hz -700Hz and arm your Oris with a MD driver with a good lover midrange driver (B&C of whatever you use) You will be able to go away with 4 channels… You have a lot of nice horns… It should be fan to play with them….

The Cat

Posted by mats on 10-04-2005

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 Romy the Cat wrote:
Try to drop the Altec in 400Hz horn down to 1000 Hz -700Hz and arm your Oris with a MD driver with a good lover midrange driver (B&C of whatever you use) You will be able to go away with 4 channels… You have a lot of nice horns… It should be fan to play with them….

The Cat



OK, I got 'em lined up a little better, tried  10uF and 16uF on the Altecs ( 12 or 14 might be about right),  I loaded the Oris 150 with B&C 8PS21 woofer and yes, this is very fun.  Thanks for the direction and inspiration.  Still, this is really just antics while waiting for the big boys to turn their lathes.  Now that will be FUN!!!!  Jeffrey, you out there?
:-)
Mats

Posted by Romy the Cat on 10-04-2005

Mats, I do not know who is Jeffrey is, anyhow, your horns look nicer this time. You need to figure out now what would sound more interesting: the 8PS21 at its higher knee or the Altec at it’s lower knee. The important would be that beside thier absolute quality of sound the both drivers should have the same tonal, dynamic and the same tension characteristics after own crossover points. Use the “vertical split” techniques that I’ve descried early on somewhere within my site to mach the channels. It would be also beneficial if you reduce the size of the Altec horn to the minimum permeated by the found crossover point of the driver (usually 60% or wherever the honk despairs). Generally the 804 is quite mellow and none-demanding driver and you should not have any problems to integrate is with anything….

Rgs,
The Cat


Posted by mats on 10-04-2005

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 Romy the Cat wrote:

Mats, I do not know who is Jeffrey is,

Rgs,
The Cat


Jeffrey as in Jeffrey Jackson:

http://www.goodsoundclub.com/TreeItem.aspx?postID=1301#1301


The "Vertical Split" exploration sounds very interesting.
Thanks again,

Mats

Posted by haralanov on 06-26-2008

I’m new to this outstanding website and I found it has really educational value and antimoronizating information Smile

I’m still in the world of direct radiators and I’m looking for the ultimate midbass channel solution. At this time it’s still impossible to build a horn of this size so my purpose is to find the next most good sounding solution. Some time ago I found very appropriate driver for upperbass reproduction – ScanSpeak 18W/8535. It has smaller magnet system (and little lower efficiency) compared to 8545. The cone material is the same as the famous 25W/8565-00 bass drivers and it has very good tone up to 600-650Hz. But then I read this:

 Romy  the Cat wrote:
  Ironically, among all enclosures and topologies that I have heard I found that a properly done bass-reflex enclosures can do the  “the melody range” quite adequately. What, the ported speakers? Are you out of your mind, Romy? This what you are proposing after the years of bitching about the “ported sound”? Yes, I do. Here is what I mean….

If a port is properly implemented then the port might do a phenomenally good upper-bass, almost as good as a “horn-loaded” upper-bass horn. The problem is that NO ONE uses the ported design properly. If do not let the ported design to go all the way down and to cut off the channel very slightly lower then the port begin to EQ the bass then it is possible to get a very-very good Sound using the bass-reflex enclosure. Paradoxically the driver in this case should be not really “ported” and an extra one or two LF channels would be mandatory for the lower octaves but with all those incontinences we gain “quality” of sound… using a port. A typical cut off of a bass-reflex enclosure in order to work properly should be somewhere around 110Hz-180 Hz and it done so then the “ported sound” does not manifest itself at all. Quite in contrary, the properly done bass-reflex might be very live, very dynamic and very musical.

It’s a quite interesting idea and I’m going to try this type of midbass loading very soon with SS 18W/8531 driver I don’t own yet.

 Romy the Cat wrote:
  The only one problem that I can see with properly done port channels that they are effective only in a VERY narrow bandwidth. Bring frequencies too low and the noise form the port compromises the entire “melody range”. Bring it too high that the driver being to sound like an open baffle….

I absolute agree with that statement! I made experimental enclosure for SS 18W/8545 tuned to 36Hz line high passed at 140Hz first order. The problem is that it sounded like open baffle even filtered at 300Hz…. And still it’d just one octave operation bandwith. If I lower the upper frequency point to 220Hz this effect evaporate but effective radiation is only 140-220Hz and it sounds like a little peak in the frequency response.

But later you said

 Romy  the Cat wrote:
  “Commandments of Mandatory Middbas Compliance”:

1) A middbas driver shell handle at least one octave below it lower cut off frequency
2) A dipoleness shell not be used anywhere near a middbas channel

The next candidate for middbas reproduction would be all versions of the box-reflex design.  Everything in ported sound is wonderful accept the fact that the ported enclosures kill all sound under 700Hz -800Hz. The third rule of “Commandments of Mandatory Middbas Compliance” said:

3) You shell run away from a speaker if you see a port

Romy, is there something you have found about ported enclosures and rejected the idea above?

Posted by Romy the Cat on 06-26-2008
 haralanov wrote:
I’m still in the world of direct radiators and I’m looking for the ultimate midbass channel solution. At this time it’s still impossible to build a horn of this size so my purpose is to find the next most good sounding solution. Some time ago I found very appropriate driver for upperbass reproduction – ScanSpeak 18W/8535. It has smaller magnet system (and little lower efficiency) compared to 8545. The cone material is the same as the famous 25W/8565-00 bass drivers and it has very good tone up to 600-650Hz.
Yes, I do know the ScanSpeak 18W/8535 driver, it is a good driver. If use it then I would have a concert about is about its suspension. For lower frequencies driver the ScanSpeak own low-resonance rubber surround (that feel more like foam) is OK but if you wish to starch it to 650Hz then it need to be re-evaluated. It might be OK, I just do not know, those I personally my prefer papers, cloth of lather suspension. The driver that will be 6dB closed at 650Hz will have a lot of put at 1000 and 2000Hz, so you need the “ringy” tail capable of transients. Most of the rubber-suspended driver has horrible transients at HF and rubber sucks HF like a vacuum cleaner. So it is all how the mass/material/structure of the cone “talk” with It’s suspension. Here are no measurements or any other abstractions would show nothing – you need to listen the thing to decide for yourself. It is very possible that ScanSpeak did a fine job with it. I think this driver is used in by Wilson extensively and the Wilson’s upperbass is extremely good (down to the point where the port ‘noise kick in and screw everything up)
 haralanov wrote:
Romy, is there something you have found about ported enclosures and rejected the idea above?
Well, I think that if to use port but do not USE the port’s output for sound shaping then it might be useful. I know it sound as a contradiction but it is not. I feel that the definition of port success would be in VERY judgmental point where the output from the post shell be stopped. If port gives for instance + 8dB at 40Hz then it is possible that at +3dB it still would be OK sonically where port would not sound like port. How to make those decisions during a design stage I have no idea as there are many other variables involved into the decisions process.

The caT

Posted by Paul S on 06-26-2008

Being +/- resigned to using BR myself right now, I concur with the idea of "not using" the bin and/or port for significant gain, and especially not to push a driver down to Fs.

I don't know the driver being referred to here, but I would recommend taking another look at whether you want 650 Hz or, say, 40 Hz, because I seriously doubt you can get that sort of range with harmonic and/or dynamic continuity.  Basically, the bin/port will affect the character of the sound differently as frequency rises.

I chose to go low-ish and wound up using very thick plywood and I coated the inside of the bins with acrylic-modified stone veneer mortar as part of my efforts to get the box out of the sonic equation.  I tried using felt inside and wound up with alternate inside faces only felted.  The port came out very close to the computer simulations, but any variation is ultimately audible.


Best regards,
Paul S


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