Another one of the Bucket List.

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JohnG
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#1 Another one of the Bucket List.

Post by JohnG »

I did not manage to produce my OB Baffle for the Xmas Break.
What I did achieve though, was that on Xmas Eve, after a fair old period of non use, I finally got all the HiFi moved into the HiFi Room once again, following a stint of decorating and major heavy duty sodding around.
I was so motivated to achieve a long term goal 'Bucket List', I even assembled my prototype Quad 57 Stacked Stands, and got the Stacked Array up and running with the 57's.

I am gob smacked at the integration of the four units, seeing as two are OTA Refurbished with OTEC R Treble Panels, these are said to be 3db gain over the Standard Quad Treble Panel.

On each channel there is 2014 OTA Refurb obove a Standard Quad, that was Quad rebuilt in the early 2000's.
I have a option to balance the Amps Volume per channel, via a Balance Control built into the 845 Monoblocks, as well as using the Slagle AVC Dual Channel Volume Control.

I can't detect any imbalances between either channel or either stacked array, when one channel is turned down.
I have also got them in a position now, that when the listener stands in the sweet spot, and slowly ascends to being seated, there is no change in the perceived volume or delivery of performance :D , yes this does make me happy.

What make me even more happy, is the noticeable improvement in the performance of the Speaker, it is thoroughly addictive, almost like the very first time I got the 57's nearly 20 years ago.
I am also setting the Slagle at between five to seven clicks, where 8-9 clicks was the minimum previously.
I've hit 8-11 clicks on the stacked array, well Dave Brubeck made me do it.

Now for the technical query, if stacking two standard Quad 57's is said to give a 3db increase in gain, what does the gain add up to if one set of speakers in the stacked array, is said to already have a 3db over the standard 57 ?
My guess would be 4.5 db, but as always I'm happy to be the one supplying the entertainment and be corrected.
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rowuk
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#2 Re: Another one of the Bucket List.

Post by rowuk »

The gain will NOT be uniform over the whole range and cannot be added like 2 smaller drivers. I think that any guess whether 3, 6 or 4.5 dB is faulty.

The issue is that for bass and lower midrange <1000 Hz, the stacked Quad works more as a line array than a couple of drivers.
With a line array (cylindrical propagation of the waveform), the sound level decreases only by 3dB when doubling the distance from the speaker. Non line array speakers lose 6dB when doubling the distance.

Due to the HF panels not being close enough to one another, there will be some comb filtering which may or may not be a serious issue. It was a reason originally on the Levinson stacked Quad array to use a single Decca/Kelly ribbon tweeter however.

For the Quads we can never forget the backwave which only causes the null at the sides. The large surfaces react far differently to room modes than small OB types.

So, your gain will be different based on distance and frequency. I would expect around 3dB below 1K and essentially no additional gain above 1K. I would expect relatively deep drops above 5K due to comb filtering. Remember that what we measure is not what we hear. The Quads perform magic in spite of the measurements - which only means that we are measuring the wrong things.

Do your valve amps bypass the transformers and feed the electrostatic panels directly?
Whenever I feel blue, I start breathing again.
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pre65
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#3 Re: Another one of the Bucket List.

Post by pre65 »

rowuk wrote: Sat Dec 28, 2019 11:29 am
Do your valve amps bypass the transformers and feed the electrostatic panels directl
I doubt it.

Our Nick had started an amp to do such but I don't think it ever got finished. Based on 813 valves from memory.

Now that Nick has a pair of 57s perhaps it's on the "to do" list ?
The only thing necessary for the triumph of evil is for good men to do nothing.

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JohnG
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#4 Re: Another one of the Bucket List.

Post by JohnG »

Thank you for the reply and technical description of what I have produced by stacking the Panels.
I have had a very long day, and will ponder the content tomorrow with a coffee as company.
The Quads are not bypassed, but it was this version that got me involved with the 57's, as I heard EAR' Tim Di Par' direct driven 57's at a Ramada show in the late 90's.
My recollection was that it was a 845 being used, but I can only ever find references to 519's.
If anybody could clear that one up, I would like the info.
My 845's were designed and built with the 57's in mind, and there is definitely a made for each other presentation, that captures the listeners attention.
A few on here heard the arrangement at the Kegworth Show.
JohnG
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#5 Re: Another one of the Bucket List.

Post by JohnG »

I have read the description, and appreciate the Technical input.
I have been sitting on a Pair of Audax HD-3P Gold Dome Piezzo Tweeters, awaiting this day, when I got the Stacked 57 set up produced.
It is looking like with these tweeters added, this will be a version of the Kelly Ribbon introduced array.
That will be the Bucket List Stacked 'Part a'
When I get around to the OB's and the separate OB Bass Units, are set up to work with the 57's,
that will be Bucket List Stacked 'Part b'

I am keen to get the OB Project underway in early 2020, so on basic completion that will be my Speaker Bucket List ticked off.
I am sure the OB Journey will be long, and to get the best out of the array will not come in a few efforts, but from many learning experiences.
JohnG
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#6 Re: Another one of the Bucket List.

Post by JohnG »

I have read the description, and appreciate the Technical input.
I have been sitting on a Pair of Audax HD-3P Gold Dome Piezzo Tweeters, awaiting this day, when I got the Stacked 57 set up produced.
It is looking like with these tweeters added, this will be a version of the Kelly Ribbon introduced array.
That will be the Bucket List Stacked 'Part a'
When I get around to the OB's and the separate OB Bass Units, are set up to work with the 57's,
that will be Bucket List Stacked 'Part b'

I am keen to get the OB Project underway in early 2020, so on basic completion that will be my Speaker Bucket List ticked off.
I am sure the OB Journey will be long, and to get the best out of the array will not come in a few efforts, but from many learning experiences.
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rowuk
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#7 Re: Another one of the Bucket List.

Post by rowuk »

Fortunately the 57s are mesmerizing - even with minor effort. Stacking them adds authority to the midbass - where they were “only” adequate” before. A solution is required for <80 Hz and >13K. The most convincing bass with the stacked 57s that I have ever heard was 2x infinite baffle 18” ( I think McCauley) located behind the Quads. The owner simply cut holes in the wall between the sitting room and his office. There was no integration issues. The top end was another story. He had the Decca tweeters that I did not like at all. As he had separate amplifiers, we exchanged the Deccas for several other solutions. I liked ElectroVoice T35s especially well as they are very soft sounding. He wanted something more spectacular and ended up with Fostex something.
Whenever I feel blue, I start breathing again.
JohnG
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#8 Re: Another one of the Bucket List.

Post by JohnG »

Thank you for the further input.
I have been attempting to put produce a functioning room mode treatment, at present it is produced in a unmeasured formulation.
I was going to wait for the OB's to be put into service before I went down this road.
At present, I have a 600mm Equilateral Triangular formed, Dense Fire Batt Rockwool set in the Room Corners, that are covering from the floor to the ceiling, the Rockwool Structure is then covered with a Strong Anti Rip Paper, for aesthetics.
In front of the Paper is a Dense Foam 500mm x 30mm x 2000mm.

The Stacked Array is positioned approximately 850mm to the Grill Face in front of these Corner Treatments, at a slightly different angle, as a parallel alignment would be too much 'toe in' for the listening position.
Between the two corner traps and spanning from either speakers support framing is a diffusion panel, that is about 2400mm x 1200mm that is sitting 600mm above the floor .
Along both side walls and starting at the speakers support frame are two more of the same diffusion panels, set at about 1000mm above the floor.
On the rear wall, there is in one corner trap built to the same design, minus the foam.
In the over corner is the rooms Door, so I have a Flat Rockwool Batt against the rear wall.

I ran out of time playing with the producing the 'yet to be proven' room mode treatment, as I was determined to be using the HiFi system in the newly decorated room for the Xmas break, which finally become a working system again on Xmas Eve.
The outstanding Jobs are to mount a Rockwool Batt on the inner face of the Door, to make a side for a triangular corner assembly, whether I go the full hog and put a removable fascia Rockwool Batt into use is yet to be decided.
I also intend on doing a set up for rear wall Diffusion, but this will be set up to suit the ears of the listener, as I have had success with this method in the past.

I also have a ceiling diffusion panel, that is purpose made for auditoriums, it is in 1200mm x 600mm, I plan on cutting this in to smaller dimensions and securing it to the ceiling.
The floor has a medium dense carpet, so maybe only a rug for room decor purposes might prove ample.
I have disliked a room in the past where trials with absorption were being over used, so I know some of the pit falls to be met, catching the corners and diffusion are Best Practice, and the most affordable to carry out.

Having a room, that I am the only one with a interest in how it looks aesthetically helps a lot.
I am hoping that if the OB's get the room mode treatment, that some of the used materials used for the treatment can be reduced, releasing a little more floor space, as I am a compulsive hoarder, and floor space is such a luxury.

Especially now Wifey, was thinking on her feet, over the few days running up to Xmas, and demanded, I cleared another room of my HiFi Collections, and consolidated 'all of it' into the New HiFi Room, 'she pulled a blinder there',
we've only just started talking again :D
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