Ali Bastanis OB testing & results

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Nick
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Re: Ali Bastanis OB testing & results

Post by Nick » Fri Feb 07, 2020 10:12 am

What I am unsure of is the eq. I don't see how you can get a flat response without bass boost which I assume there is given the size of the amps. Ali's ob's are in effect baffle-less, but I do wonder if the lossy suspension is playing a big part.
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 10:14 am

Yes, was awaiting Vic's answer on that, my impression was that there wasn't, but then his previous post seemed to indicate there was, unless he was referring to the 10db boost to match sensitivities.
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Re: Ali Bastanis OB testing & results

Post by Nick » Fri Feb 07, 2020 10:36 am

Well, the one I saw, suggested that there was a bass boost at lower volume levels, sounding a bit like loudness curves.
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Re: Ali Bastanis OB testing & results

Post by Nick » Fri Feb 07, 2020 10:42 am

What were the upper frequencies like, as the curves above 13kHz look horrible for 5MR450-NDY (not that my ears go much above that, but I think Ali's do).
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Re: Ali Bastanis OB testing & results

Post by chris661 » Fri Feb 07, 2020 11:02 am

Vangelo wrote:
Thu Feb 06, 2020 5:10 pm

I could buy 22 x NX6000D's for the price of a single Powersoft X8. Not a direction I am prepared to head in. I like to keep my hifi real!
Fair enough. I use the T-series, which can be had a good deal cheaper. I can't say what I paid for the amps, but it was considerably less than the RRP. My PA system (which can sound rather HiFi, if I do say so myself) uses a T604 to bi-amp the main speakers, and a T602 for subwoofer duties.

Nick wrote:
Thu Feb 06, 2020 6:13 pm
Remember the drivers are out of phase and facing in the opposite direction, so in theory there should just be a moving column of air between the two drivers and no pressure. People who understand the physics may have a view if that air mass has any effect but I know not.
Well, the slug of air will add a small amount of moving mass. I'd expect a slight drop in Fs (probably no greater than unit-to-unit production variations) when comparing the two drivers like this to a single free-air driver.
You also gain a bit of path length (offsetting dipole losses a little) by mounting in this way, too. I do wonder if putting a single driver in a short cylinder would give similar results.

Chris

PS - FWIW, a gentle crossover slope (Bessel, for instance) might end up looking similar to the required EQ curve.

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Re: Ali Bastanis OB testing & results

Post by Nick » Fri Feb 07, 2020 11:18 am

There is a thought, would putting the two drivers at the end of a 30cm tube give the same effect as a 15cm baffle, and would you need to have a tube to get that effect below a certain distance, and what would that distance be?
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Re: Ali Bastanis OB testing & results

Post by Vangelo » Fri Feb 07, 2020 11:32 am

Nick wrote:
Fri Feb 07, 2020 10:12 am
What I am unsure of is the eq. I don't see how you can get a flat response without bass boost which I assume there is given the size of the amps. Ali's ob's are in effect baffle-less, but I do wonder if the lossy suspension is playing a big part.
Yes, there is bass boost applied on the dynamics eq page of the NX.
I have tailored to taste so I have more bass at low volume. As the volume increases it diminishes.
The boost in my case represents a gentle curve from around 200Hz rising to 15db @ 20hz @ -50db gradually reducing to 0db @ 0db.....max vol.
I would say at normal listening levels this represents a 5db boost.

The parametric page is flat, apart from notch at 50hz for room resonance.

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Re: Ali Bastanis OB testing & results

Post by Johnj » Fri Feb 07, 2020 12:02 pm

My own take on the PRV drivers is they excel in mid end punch. No treble nasties. Perhaps not the last word in treble detail but using multiple drivers helps with this

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Re: Ali Bastanis OB testing & results

Post by chris661 » Fri Feb 07, 2020 12:33 pm

Vangelo wrote:
Fri Feb 07, 2020 11:32 am
Nick wrote:
Fri Feb 07, 2020 10:12 am
What I am unsure of is the eq. I don't see how you can get a flat response without bass boost which I assume there is given the size of the amps. Ali's ob's are in effect baffle-less, but I do wonder if the lossy suspension is playing a big part.
Yes, there is bass boost applied on the dynamics eq page of the NX.
I have tailored to taste so I have more bass at low volume. As the volume increases it diminishes.
The boost in my case represents a gentle curve from around 200Hz rising to 15db @ 20hz @ -50db gradually reducing to 0db @ 0db.....max vol.
I would say at normal listening levels this represents a 5db boost.

The parametric page is flat, apart from notch at 50hz for room resonance.
... Doesn't that mean the LF response changes as the program material shifts in level?
ie, press Play on the CD player (or whatever) and a quiet intro has more LF than when the big chorus comes in.

Chris

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Re: Ali Bastanis OB testing & results

Post by Johnj » Fri Feb 07, 2020 12:48 pm

On Vic system it works without any issues in sound levels during quiet or loud moments.
In my room I use no extra gain but have different bass drivers at a higher crossover 340 and completely flat throughout.

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Re: Ali Bastanis OB testing & results

Post by Wolfgang » Fri Feb 07, 2020 4:13 pm

Well the price of the drivers is what it is, I’d say an NX 3000 could be used instead which is a good bit cheaper. How much were your Lowthers?
Vic commented that he’d tried a lot of bass drivers, it was these particular ones that give these very good results.
The Lowthers DX4 were almost the same price ($2400) but there were no risks involved. I know how they sound and what I can expect.
The bass drivers in OBs and the comments, explanations, and tutorials regarding OB in general which I have read/seen in the meantime are highly controversial and don't have a clear message. Only way to find out is to buy stuff and test it for yourself.
Not sure expense was where Wolfgang was coming from Ali, just commenting that the price point is similar to the servo-equipped bass he's been looking at following the SLOB bass loading discussion.
That's right. It's not the expense per se but to get the best results for the money. The point is that I cannot use the low x-over point of 120Hz of the servo controlled OB subs without another driver in order to fill the gap between sub and Lowther BLH mid horn or La Scala front loaded horns. The Lowther horns simply don't sound as fast and airy anymore if I couple them at 120Hz (now at 210Hz ). This is a picture of those horns in combination with the La Scala bass (PM6A now with DX4 phase equalizers- great improvement!):
LSPM6A.jpg
I use the Behringer Ultradrive as active x-over and the dynamic EQ works seemlessly and is a must in my case for making everything sound right for al kind of music styles and at all loudness levels. It's really a wonderful tool. The servo controlled subs would add a few more options for fine tuning which the Behringer doesn't have. I just don't know if it would be worth adding another amp/driver for getting those options.

I was thinking - also after getting a better understanding of what Vic was doing with the cables looking at the pic he has posted at parts-express - that I would first try to mount the bass drivers with springs to the frame. Springs can be tuned to a certain frequency and don't transmit low frequency vibrations. Maybe even a wooden frame would work?
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 4:38 pm

I’ve seen on Vic’s Lencoheaven thread that there is no movement of the drivers’ baskets until he feeds them a 5hz tone. I can certainly vouch for there being no movement whilst I was listening- and some of that was at high SPL’s, certainly a fair bit higher than I would normally listen.

There are some pictures of an earlier version which used a wooden cradle, which the driver magnets rested directly on.
Last edited by Ali Tait on Fri Feb 07, 2020 4:44 pm, edited 1 time in total.
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 4:42 pm

Nick wrote:
Fri Feb 07, 2020 10:42 am
What were the upper frequencies like, as the curves above 13kHz look horrible for 5MR450-NDY (not that my ears go much above that, but I think Ali's do).
I would say they are on the lively side up top to my ears, but I didn’t detect any nasties subjectively, and they did very well on imaging and soundstaging, better than some drivers I’ve heard costing considerably more.

Of course this again could be down to the mounting method.
Last edited by Ali Tait on Fri Feb 07, 2020 4:46 pm, edited 1 time in total.
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 4:44 pm

Vangelo wrote:
Fri Feb 07, 2020 11:32 am
Nick wrote:
Fri Feb 07, 2020 10:12 am
What I am unsure of is the eq. I don't see how you can get a flat response without bass boost which I assume there is given the size of the amps. Ali's ob's are in effect baffle-less, but I do wonder if the lossy suspension is playing a big part.
Yes, there is bass boost applied on the dynamics eq page of the NX.
I have tailored to taste so I have more bass at low volume. As the volume increases it diminishes.
The boost in my case represents a gentle curve from around 200Hz rising to 15db @ 20hz @ -50db gradually reducing to 0db @ 0db.....max vol.
I would say at normal listening levels this represents a 5db boost.

The parametric page is flat, apart from notch at 50hz for room resonance.
Thanks for the clarification Vic.
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Re: Ali Bastanis OB testing & results

Post by simon » Fri Feb 07, 2020 5:08 pm

Ali Tait wrote:
Fri Feb 07, 2020 4:38 pm
I’ve seen on Vic’s Lencoheaven thread that there is no movement of the drivers’ baskets until he feeds them a 5hz tone. I can certainly vouch for there being no movement whilst I was listening- and some of that was at high SPL’s, certainly a fair bit higher than I would normally listen.
With the drivers being out of phase I would expect there to be minimal movement. But I still haven't got my head round where the sound comes from - the backs of the cones???

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