[kyrill]

I started full of hope making an OB based U frame on the info in this forum


dimensions: width 16 inch x length 43,3 inch U frame is 6 inches deep, the other plank 7 inches

the 2 woofers are Gr-research servo powered woofers
the mid range a 6" not for OB desighed Focal Audiom midrange which i hoped could do the work between 100 hz and 2 khz, [Xmas 2.1 mm, Fs 117 hz, Qts 0,49]
the tweeter the Peerless HDS 810921 tweeter ( not on picture yet)

I use active tri amping ( incl the servo amps) tubes for mid and high
the matter of Xovers i left to the DEQX.
The DEQX measured the woofers over 300 hz
the midrange driver fell gradually off after 200 hz and DEQX suggested a Xover of 210 hz, i used still 200 hz with a slope of 48 dB

The problem is it sounded awful, the worst part is the lack of transparency and much too much bass and midbass

With speakers in box the DEQX is a dream. it creates linear filters with choosable slopes, flattens the freq.response within 1/10th of a decibel  and corrects the phase through out the whole spectrum

I assume that the measurements do not take into account that the drivers are dipole or in an OB fashion. Is it possible that the phase correction will be distorted by the back waves of the OB setup? Also the system is 6db more efficient? DEQX manual explicitly warns to avoid as much as possible  room interaction and wall reflections. It measures best in an professional anechoic chamber or outside in the open air

I read here in this OB forum that mic. measurements are (easily) made of OB setups but is it possible to gather data of an OB system which can be reliably used to correct phase?

I would hate to omit the phase correction of the DEQX, one of its "crown jewels"
kyrill

[jlharden]

Hi Kyrill,

Are the woofers/ plate amps exhibiting some rising response contributing to a excessive bump in the midbass that wouldn't occur with a lower xo point? Does the plate amp do crossover function or is it defeatable? Do you have multiple woofer lp filters in place? Can you set the filter points and slopes manually, maybe experimenting with something that *should* produce acceptable results? Perhaps Linwitz-Riley 4th order for midrange hp and lp and tweeter hp. Does the xo allow gain setting for each output? You should be able to get something decent going on. I know nothing about your selected midrange and hf parts, but I would be conscious of using a midrange/midwoofer that will perform low enough to allow a seemless transition where both drivers are still linear. Have fun with it!

Jerrod

[D OB G]

Hi kyrill,

I use a DEQX HDP3 for my OBs with great results.

What measurement procedure are you using?

Mid/tweeter should be done at about 2m as a biamp measurement with lots of absorbent material on the floor between speakers and mic (pile of pillows, blankets, doona e.t.c.).  You can get away with including the floor bounce if the padding is good enough, which gives more detail in the lower freq measurement of the midrange. Tick time align (of course  ).

Take the woofers as a subwoofer measurement from your listening position.  This makes allowance for all room effects.  Tick step response.  All drivers are now time aligned and corrected for phase. 

The only decision now is how to cross from woofers to mid/tweeter, and with the 3 profiles you can compare different configurations on the fly.  (200 Hz seems sensible).  You don't need linear phase at his crossover if you don't want it.  You can chosse Butterworth and Linkwitz-Riley as well, down to 6dB per octave.  I use linear phase though at 48 dB per octave.

What crossover freq did you choose to the tweeter and what slope?

David

[D OB G]

P.S.

When you do the check measurements (room measurement) procedure, do it from the seating position.  If everything has been done correctly, you will have a flat reponse.  (The 2m biamp measurement should also be on the listening axis).

David

[kyrill]

hi David, Jerrod
thx for yr advise I searched old data at the DEQX forum but could not find consensus on how to measure OB

I did a tri amp measuring. The plate amp of the servo woofers has a built in slope of 12db ( HT setup when bass management is expected to be done by the Home theater receiver) and choose-able filter points next to two steeper slopes. The EQ part of the amp with a lot of possibilities i put on "off" as i want the DEQX to do that. SO i let the DEQX "think" that combi of woofers and amp was an integrated part of the speaker

I measured all drivers at a fixed distance of 1 mtr

So David i will try yr suggestion bi-amp and subwoofer combi but i dont understand ( never worked before that way) the "step response" I just tick it and then i have time aligned? I thought the automatic phase correction would do this too? If you dont tick "step response" you cancel the TA and phase correction of the DEQX?

I used 48dB at 200 hz and 60db/oct at 2 khz

[kyrill]

P.S.

When you do the check measurements (room measurement) procedure, do it from the seating position.  If everything has been done correctly, you will have a flat reponse. (The 2m biamp measurement should also be on the listening axis)

David

How can i measure the mid and tweeter in the listening axis? Because the spot where my speakers stand is 5 feet from the back wall and 3 feet from the sidewalls.
Following instructions i put the speakers in the middle of the room in the middle between floor and ceiling, completely not my listening axis.

[D OB G]

Hi kyrill,

The step response option is the way DEQX time aligns (for the seating position) for subwoofers that are not located near the main speakers, but in your case you still tick it even though your woofers are part of the speakers.

Taking triamp OB measurements definitely won't work.

By the way, when you are in Control Panel and go to Filters, you can choose to check freq. response, phase, group delay, and ! step response, to confirm that DEQX has implemented it correctly (which it always will this way).

David

[D OB G]

It's OK to measure the speakers in the middle of the room for biamp, as long as any toe-in in the actual final position of the speakers is replicated in your measurement axis. (you need to correct for the same angle of edge diffraction, polar resoponses, and if you use lots of absorbent stuff, you'll get just as good a measurement leaving the speakers where they're going to live. (i.e  gate the measurement before any reflection, except the highly attenuated floor bounce).

[D OB G]

P.S.

I just noticed 3 feet from side wall.  i.e. 2m of first non-floor reflection.  So you will need to measure just a bit closer tjhan 2m to gate that out.

[kyrill]

thx
I start today

[kyrill]

hi
Well it was no so "doable" as i thought or hoped it would be.

I use the beta software vs 2.58 and with measuring you cannot choose biamp with sub woofers only bi amp

So i measure and calibrate mid and tweeter the way you suggested. No problem

then i measure the woofer. you say:
"Take the woofers as a subwoofer measurement from your listening position.  This makes allowance for all room effects.  Tick step response.  All drivers are now time aligned and corrected for phase. "

but DEQX does not know when measuring my subwoofers as a separate measurement ( apart form mid and high) that other drivers are involved? Only in the tab "configuration" when i assign the filters to the biamp speaker i get a choice to add subwoofers and limit filters. In this tab there is no TA option or step response, only in the window of the measurements. In the case of measuring two drivers ( mid and tweeter) step response or TA choice makes sense.
In the apart measurement of the woofer there is no other driver to TA to? or it should be "horizontally" between R and L woofer. But i see no option to TA between Sub and  mid/high speaker combo.

my mid and high are much better  but overall sound is not high end.. I seek further

[pedroskova]

My two cents on your exaggerated bass/midbass...

Floor bounce - this is a function of the distance of the driver to the floor, the distance of the mic to the driver, and the angle of the floor reflection.  It's not unusual to see very large dips in the measured response between ~150 - 300Hz as a result of destructive interference between the reflected sound and the sound coming straight from the driver.  The exaggerated bass problem arises when your DEQX "sees" this null and tries to fill it in.  It's a problem because that null is not found uniformly around your room...even a meter away from your listening position, so you end up with far too much energy in that part of the frequency range for the room as a whole. If your DEQX were truly "smart", it wouldn't be "suckered" by floor bounce. 

As somebody has already mentioned, you can combat this (to a degree) by putting down a very thick pile of pillows and quilts between speaker and mic to absorb the energy before it has time to reflect.  Another way to get around this is to put your microphone on the floor.  This may have the opposite effect, since your DEQX may subtract bass because your floor is a boundary and may be reinforcing your bass...causing your DEQX (let's call him HAL  ) to subtract bass that won't be at the listening position. 

I take it that HAL has options for manual EQ.  I would take him (HAL) out of the bass chain, take a series of measurements in an arc around your listening position with something like ARTA, RoomEQWizard, or an RTA, and manually EQ your bass according to the trends you see.

On a separate issue, you may want to look into mounting your bass drivers on a smaller subassembly behind your main baffle, and sealing the space between the two with something pliable, like foam or even duct tape.  With a baffle that large, the energy those drivers sink into it are going to cause it to begin acting like a driver itself...albeit a very bad one. 

p.s. - those are some serious looking drivers!   

[kyrill]

Welcome Pedro to the Circle, i hope you will continue contributing and enjoying the diverse Circles
I am from Holland but this forum is my number one choice : )

My two cents on your exaggerated bass/midbass...

Floor bounce - this is a function of the distance of the driver to the floor, the distance of the mic to the driver, and the angle of the floor reflection.  It's not unusual to see very large dips in the measured response between ~150 - 300Hz as a result of destructive interference between the reflected sound and the sound coming straight from the driver.  The exaggerated bass problem arises when your DEQX "sees" this null and tries to fill it in.  It's a problem because that null is not found uniformly around your room...even a meter away from your listening position, so you end up with far too much energy in that part of the frequency range for the room as a whole. If your DEQX were truly "smart", it wouldn't be "suckered" by floor bounce.  Yes it is a complex given, when it is not so cold anymore outside now it is winter, i will measure the speakers outside in open space 10 feet above ground on the edge of the flat roof of my outbuilding
I will try also measuring 2 inches from the upper woofer

As somebody has already mentioned, you can combat this (to a degree) by putting down a very thick pile of pillows and quilts between speaker and mic to absorb the energy before it has time to reflect.  Another way to get around this is to put your microphone on the floor.  This may have the opposite effect, since your DEQX may subtract bass because your floor is a boundary and may be reinforcing your bass...causing your DEQX (let's call him HAL  ) to subtract bass that won't be at the listening position. 

I take it that HAL has options for manual EQ.YEs, 10 variable band of sophisticated ( variable Q) parametric EQ. I would take him (HAL) out of the bass chain, Yes good idea, dont't apply an automatic  filter to the bass units take a series of measurements in an arc around your listening position with something like ARTA, RoomEQWizard, or an RTA, and manually EQ your bass according to the trends you see. The "HAL"can do room measurements  itself

On a separate issue, you may want to look into mounting your bass drivers on a smaller subassembly behind your main baffle, and sealing the space between the two with something pliable, like foam or even duct tape.  With a baffle that large, the energy those drivers sink into it are going to cause it to begin acting like a driver itself...albeit a very bad one.  Nah will look terrible

p.s. - those are some serious looking drivers!     those are GR research servo drivers, ( http://www.gr-research.com/index.asp?PageAction=VIEWPROD&ProdID=141) maybe the servo part FB will cause HAL to miscalculate phase response and TA correction. FB will eat milliseconds from the impulse response and may have other side effects. I will experiment now with HAL only taking care of mid and high and with TA on or off with respect to the sub as soon as i discover how to tick it on or off

[D OB G]

Hi kyrill,

I too have V2.58.

When you take a measurement, choose biamp and tick 96 kHz.

After you've done all that stuff, where the word biamp appeared, it's a drop down menu, and then you can choose subwoofer. Don't tick 96 kHz.

After you have done the calibration and you go to configure, choose "biamp and subwoofer".  Then choose the correction filter for biamp for each of left and right, and then choose the correction filter for subwoofer for each of l and r.

You then need to choose the limit filters for the crossover.

DEQX will time align, because it knows the time of flight for both biamp and subwoofer (including any electronically induced delay).

Not only will the measure function  of DEQX show that the "null" doesn't exist, but you can use other measurement techniques to verify that DEQX is "clever" enough to get it right.  You can use Real Time Analysis (I use TrueRTA) and I also use Praxis, both of which will show that you get a truly flat on listening axis freq response.  The way you design the speaker will determine the polar response.

You won't be able to EQ (and I'm not and advocate of doing it at all) until after you have a subwoofer measurement, configure, and measure the system as a whole.

I second the idea of a separate woofer baffle, which I use myself, which DEQX will time align.

Kyrill, DEQX will get you optimum, very high end results, but it may take a while to learn the ins and outs.  Just perservere.  I hope I can answer questions for you.  You can also email (being in Australia I was able to ring in the early stages) Alan at DEQX.  He is very helpful, and will be able to clarify points if I am not clear enough.

David

[D OB G]

P.S.

The tweeter and the midrange must be measured together at a distance where vertical lobing "integrates", using biamp (i.e. the further away, within reason, the better) so measuring outside should be good (just make sure there is no floor bounce).

If you measure the woofer at 2" you are effectively measuring the infinite baffle response, not the dipole response- won't work.

Just as a side issue, I belive imaging would improve if the tweeter was above the midrange, rather than out at an angle.

Another thing, I would suggest doing a search in Lynn Olson's enormous "Beyond the Ariel" thread to find where he explains how to take an impulse measurement with MLSSA, because that is what DEQX want's too-  the cleanest impulse measurement possible, with the longest gating, to get meaningful freq response measurements as low down on the midrange as possible.

[kyrill]

ok

I try again

I must do it right, any abbreviation form "right" and the sound will sound reproduced.
Doing it right, and the whole system disappears. this is my ultimate goal.

I have found "flawless" reproducing Jadis tube amps after heavy modification. I even send a 23 kg Jadis to Joe Rasmussen in Australië ( http://www.customanalogue.com/jlti_el34.htm ) to do his super triode mod to transform the original PP mode, this way  negative feedback can be completely eschewed. The amp is also fitted with a module  called  "L.E.M"., Linearity Enhancement Module, and the result is to induce Permeability in the output transformers. The other mod is Menno van der Veen's mod to have automatic bias for the 4 end tubes in a "superb" way see: http://www.mennovanderveen.nl/eng/autobias.html and lastly a "normal"mod to replace coupling caps for Jensen Copper Foil Paper-In-Oil I preferred VH or Sonicap Platinum, but that is what in the end Peter ( did the cap mods on both amps) had in the house. Both amps have those Jensens in place.

The other amp stayed in Holland  but Joe "instructed" Peter v Wijngaarden ( colleague from Guido Tent and Menno) to do his mods alongside Menno's mod. The mods transform the original already musical sounding Jadis amps.

Would I urge all tube PP owners to these mods? YES YES and another YES. No hum at all even with my ears almost touching the 95 db sensitivity drivers I hardly hear hum. on the tweeter it (hiss) is even more difficult to hear 
The amps sound very very transparent, but i will in due time put a review in the tubes section

So I really want the OB to sound right

Thanks  David

PS "I believe imaging would improve if the tweeter was above the midrange, rather than out at an angle"

on top of the midrange the tweeter would be way too high above listening  position. But my "concept" baffle was not designed to have the tweeter  between mid and woofer. Also i notice the woofers resonate the baffle rather hard I will find a way to decouple the vibs form mid and high and  a yes, a seperate baffle willl do that or what i was originally thinking the two baffles ( mid/high and woofer) dont touch each other. Not yet implemented in the proto design

[kyrill]

I notice in this thread my picture of my OB setup linked from my gallery suddenly is replaced by the audiocircle's logo? I also notice in a quite different forum, ( DEQX private forum)  that I cannot post a picture coming from Audiocircle gallery. How come?
 

[D OB G]

Hi kyrill,

Just touching base.

How are things going with the DEQX?

David

[kyrill]

Hi David

the Focal Audiom 6w ( although it sounds pristine) is not up to the task to get to 100 hz.
I dont want (yet) the big 12 inch woofers to go to 200 hz.

SO i am replacing it with what eventually i dont know yet.
I have bought on Ebay a pair of SABA Greencone's ( alnico magnet) 8 inch all rounders ( 60-10 khz) out of the '50 ( 1950-1957) They seem to sound very very musical with tubes in OB fashion but hate Metallica i hear

If these will not sound the way i like them to be, i will follow Danny ( from GR-Research) newest Paudio project

Danny's rig
the 12 inch mid has an internal tweeter which fires through (!) the dustcap but it seems to sound extremely well
http://www.audiocircle.com/index.php?topic=61023.20
My DEQX will in Januari go back to AU to have a very important mod ( which was partly in the design of the DEQX III,  but at the last moment canceled) the replacement of the crystal for a much better ( Guido Tent clock) I take the plunge to choose a super stable pws +clock from Joe Rasmussen
The TERRA FIRMA Clock

http://www.customanalogue.com/terra_firma.htm

[kyrill]

Well the Saba green cones was a dead end for me although i am very impressed by its wonderful musical nature, maybe for my HT setup.
I put my new findings in the thread Recommendations for 8 inch driver High Eff to 2000hz http://www.audiocircle.com/index.php?topic=62520.0