Now a Soviet Era Drivers for the Mets

Hari, if you are willing to take a chance and experiment, this design may well click with your driver:

http://www.decware.com/newsite/ZOB.html

Its single driver design, very interesting with kind of indirect BLH. You may compare the specs of the driver used with your own driver TSP after it arrives.
I did a quick math and designed an Helmholtz Resonator using the formula to tune at 50Hz. I am not sure of the implementation though as this will require to channel the low frequency to the mouth of the pipe for it to resonate at 50Hz. I can imagine channeling of the air, but again this could hamper with the mid-range too. I think a TL-sub will be a better option for the low end as i will be venturing into an unknown territory with limited budgets.
 
I finally received the drivers today morning. Immediately did a small break-in for around 30 minutes as the drivers were sparingly used. This driver is a low stiffness and high compliance type. Measured the TS parameters of one driver as below,
Fs= 37Hz
Qms = 9.56
Qts = 0.856
Qes = 0.94
Mms = 12.48 gram
Cms = 1.431 mm/N
Re=4.86
Rms = 0.309 kg/s
Vas = 83.64 liters
BI = 3.907
Lp = 88.83dB
Sd = 203 sq.cm

Also listened the speakers for around 15 minutes and found them to be sweet sounding without any harshness or compression. Will definetly not require a tweeter with my initial listening. Cannot judge about the BSC now as the driver was not mounted on a baffle.

I have now asked the carpenter to built my OB with this driver after simulation with the above parameters. Attached is its simulated response with the BSC adjusting for the Room gain. The roll-of is around 50Hz, with an F3 of 39Hz and F10 of 26Hz. Hope i get this response in practice.
 

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Specs wise it looks awesome. Congrats ! I am very curious on its HF response. Does this guy make these in 12” ? Sensitivity is on the lower side but I still believe it will sound very sweet with tube power.

Awaiting your sonic impressions in the OB. Good Luck with your first OB ever.

Where do we stand with current customs duty on drivers after GST ?

I am listening this driver now free air and the HF response is full till 20KHz or probably more. No need for any tweeter help for sure. I am playing with my Sony TA-AX44 IC vintage amplifier. The response in 300B will be great for sure. Also the bass is quite tight even though they cancel out due to free air operation. But there is no blurring of the lows nor any compression of the mids or highs. The HF is very very sweet sounding, nothing harsh but very pleasing to the ears unlike the Fostex. The Fostex was a more technical speaker and the shout at the mid-range was phenomenal needing some serious correction. In this broad band, i am at ease and till now there was no fatigue or felt the need for any correction. Now after building the OB, the bottom end will dictate the final sound stage. Till now, i am happy with the outcome, but will wait till the weekend for the sonic impression comments.

I am not sure about the custom duty, i did not pay any custom duty on this one. The ebay figure is the final figure paid in $$$
 
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Yep, I saw this driver on eBay a few days back. Your initial impression is quite tempting.....

Awaiting your OB impression.
Grab it till its available. You will not regret for sure.

Subjectively i will not be able to explain them properly. I will invite FM Prem, Jousha and Sumanta and ask them to pen a few wrords after listen.
 
If you see my simulation, the baffle gain is around 6dB from 300Hz onward contributing to the overall output. Since the freq below 300Hz will not benefit from this baffle gain due to their larger wavelength will sound thinner than freq above 300Hz. To compensate this, the freq above 300Hz need to be tamed by atleast 3dB to give some level to the rest of the Freq. Resp.

This will again depend upon how far the baffle is from the front wall. If you are keeping the baffle around 3 feet from the front wall, then probably you wont need a BSC, but if you intend to keep around 5 to 6 feet away, then the lows can diminish by 6dB. There is also a room-gain of around 10dB to 5dB from freq 10Hz to 70Hz seen in the simulation. So the hole can be between 100Hz to 300Hz where the mid-bass lies unless compensated. If by intelligent speaker placement, if you can remove this hole then it will dictate a win or loose speaker system imo.
 
Here are some images to feast the eyes. Could not wait till the weekend for the outcome and hence did the cardboard trick to check out what the fuss is all about this driver and OB. Was blown away by the dynamics of this broad band. Nothing even come close to compare - well atleast known to me. Its even without following the Basta dimension an placing them on the cardboard. I will stop commenting further and will like other FMs to listen and then comment about them.
 

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Yes you, Prem and Sumanta certainly deserve a Candie for sure. The Basta simulator was crucial to swing my decision to OB. I usually don't venture into unknown territory and follow a systematic approach as far as possible. After measuring I was even more convinced about the dynamics of this driver. Today I was fully amazed by its dynamics , uncompressed open sound. Everything else till date sounded so boring and unconvincing even in shorooms and shows. Also was at the whathifi show. Setups 100 times more expensive than this will have their run for their money.
 
OB is all about relaxed, uncompressed sound. Just find a right driver for OB and let it sing all by itself and you will be amazed what all it does, making music the way you never heard before. And a midrange to die for.

This Soviet driver is 4 ohms. Will it be alright to use it on a tube amp with 8 ohm speaker output given the midrange HF duty it will do ? The impedance will not dip.
My 300 B tube amp has 4 ohm and 8 ohm taps. The VC resistance is 3.9 ohms and impedance is 5.7 ohms till 10khz and rise only till 10 ohms @ 20khz. The inductance @ 1khz is 0.17mH.

Currently not using any BSC and enjoying the organic mids and highs.
 
Do not add any passive components to the driver as far as possible.

I presume your 300B does 7wpc. The driver is around 89dB. Does it go sufficiently loud with still some volume margin left ?

Did you so far at any time had a feeling of rolled off highs and need of a super tweeter ?

What’s your opinion, is it safe to play this FRD with a tube amp with only 8 ohms output tap ? Given, it won’t do duty lower than 100hz.
Yes, the rated power output of this amp is 9 Watts, but definetly can give 7 wpc. With the Basta i get a calculated SPL of 91.5dB which looks real. I am currently running them with 10 o-clock volume position with plenty of margin and is more than sufficient for 90% of my music collection.

Highs are flat till 20KHz, will not require any super tweeter - 100% confirmed. The highs are sweet sounding, detailed, mellow and no harshness. For the first time flute sounded like flute, Piano and violin like real instruments. No requirement for either a sub-woofer or a large 15"+ woofer too. That will ruin the smooth crossover-less sound of this dynamic. Also the horror story of phase matching the driver, crossover will be a challenge. Just use this broad band in simple FR mode, sit back and relax with a cup of coffee with nothing coming in between the performance and you.

You can play this dynamic with the 8 ohm output tap. If you see the impedance plot, the impedance phase is safe and the phase angle at resonance is just 45 deg and later it goes inductive till 20KHz with only 10 deg phase. Hence 100% safe load for the amplifier. No worries.
 
Thanks Hari. I might as well take a plunge. Black surrounds for me instead of white. Did you ask the seller to customise or just a choice of white surrounds and rest everything as stock ?

I await what other FM have to say about the sonic impressions of this Driver after they visit you.
There is a you tube video of this driver hanger customisation. With different hangers you get different Qts, Qms and Fs values. I preferred white as they gave Qts published 0.7 and measured 0.85 which is cool. I am not sure what if for black hangers. You may need to check that video before deciding. Go for something nearing Qts 1.0.
 
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What is your source when you are playing these FR drivers ?
1. Marantz CD player used as a transport connected to DIY PCM1794 Burrbrown DAC.
2. Technics SL-23 TT, with Ortofon cartridge, connected to DIY FET input, CCS Phono preamp.
3. Aiwa FD-660 3 head tape deck

All the above connected to DCB1 preamp ànd them to 300 B monoblocks.

IC are stock or DIY, speaker cables are - 18 swg polycab cables currently.

Have used a Japanese high grade RF, EMI Spike supressor at AC input.
 
@ Yogibear.
I plan to experiment with a bypass type BSC to take affect from around 200Hz. I will be using a 30 ohm resistance in series with a 7uf cap and put them across the driver termina. It helps to make the impedance phase fully resistive load. Also dynamics will improve as low end will open up even more with this. Will post impression after listening.
 
Sure. Looking forward to your impressions. I am not conversant with passive components. Would try to learn and understand.

When you play through CDP, does this Soviet Driver sound bright or forward in mid or Hf ?[/QUOTE

Yesterday evening received the raw OB module and assembled them in 30 minutes flat. After some carefully planned placement made them to sing.
Initial impressions are quite encouraging and the dynamics and imaging are perfect. The sound stage is wide and the midrange presence awesome. The mids and highs are very much balanced with the lows and they don't sound harsh or beamy. Don't require any phase plugs too.

I tried my BSC, but that reduced the dynamics of the sound stage and later removed them. This broad bander is designed to play direct with nothing in-between. Add anything and the midrange gets clutterd. Also tried adding additional magnet, even that cluttered the midrange. This is a true FR driver and does not require a helper woofer or tweeter to argument the lows or highs.

Imo, the Fostex is not a FR driver as thought so, it definitely requires support at bottom and top and they may excel in midrange and require plenty of effort in getting them to sound right. In contrast this broad bander is plug and play.
 
I was fully engaged with my new OB speakers for the past 2 days and did not find time to post update. Yesterday did some objective measurements and posting my findings,
SPL
https://ibb.co/ioCOFS

The SPL range is from 40Hz to 20KHz and if you look at the minimum phase, @ 20Hz its at +90 deg and at 20KHz its at -90 deg and the transition @ 0 deg is at 1KHz. This gives a very good octave to octave balance for the entire 10 octaves.

The SPL is flat and the high and low peak and dips are within +/- 2.5 dB which gives excellent dynamics to this speaker.

STEP:
https://ibb.co/cDor27

The Step Response show Coherent behaviour for the lows, highs and mids. The whizzer cone ripple is also seen here and the decay is quite smooth.

Impulse:
https://ibb.co/ehqSaS

The rise time and fall time of the impulse response is 100% of full scale and the corresponding decay is very linear and smooth without any overshoot or dips.

Decay:
https://ibb.co/i8eW27

The decay in my room is well controlled and there is no clutter in the mids with very minimal stored energy to be released later

Waterfall:
https://ibb.co/iH0AvS

The waterfall plot shows the dynamic nature of the driver with full control on the peak response giving this speaker a lively and sweet presentation.

Spectogram:
https://ibb.co/jxMTh7

Shows well controlled response with no major response anomalies. The low end response extends till 40Hz and the highs even beyond 20KHz.


This is one of those speaker which measures equally well as it sounds. I will say, its one HECK of a speaker.

@ yogi bear , @ Jousha

For a comparision, i have also posted the link of the much acclaimed Beethoven OB speaker for your objective analysis and draw your parallels

https://www.stereophile.com/content/audio-artistry-beethoven-loudspeaker-system-measurements

https://www.stereophile.com/content/audio-artistry-beethoven-loudspeaker-system-measurements-part-2

https://www.stereophile.com/content/audio-artistry-beethoven-loudspeaker-system-measurements-part-3
 

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