open baffled all over again

[wunhuanglo]

Hi

The upper baffle was sized using "The Edge"

http://www.tolvan.com/edge/help.htm

The system is all active: tri=amped, 24 dB/oct LR 23-way crossover, 31=band EQ.

XO points are 125 Hz and 3800 Hz.

The tweeter is ear-level, above the Fostex, placed asymmetrically.

Flat to 35 Hz (measured, in-room)

I don't feel that the 18" driver, given the low excursions and extremely open back, really requires a push-pull to cancel distortions.

 

[Saurav]

Thanks. So you didn't include the baffle area of the lower box when using the Edge simulation program... is that correct?

 

[RR]

Spanish 15" woofers

Hello Nuuk,

I think you are talking about the OB of my friend Mentero, where he used two 15" per side, isn't it?

Brand is ARP, model LM 1552.

Datasheet: http://www.musicson.com/htmlin/LM1552.htm

I have a couple at home, BTW, testing on open back boxes.

 

[then_dude]

maybe he's talking about that one, but i'm not

i'm looking for a 15 inch driver model RSW 1535; the conus is yellow, but that doesn't mean it is in fiber; i saw it on ebay; i thought maybe somebody could tell me what it is, because the seller isn't answering my questions

 

[Hans L]

But what if you wanna use "home" woofers; i have looked at gradient, because they are cheap, the have an 12 inch driver for 40 euro, it has an FS 32, allright not that deep, but i don't need anything lower.
...
i know it isn't an xls 12 peerless with 40mm lineair excursion, no it's one with 4mm lineair excursion, but since it has more sensitivity and most of all more Qts i doesn't need to be driven so hard. personaly i think an home-woofer will sound better, but wil it be enough?

The gradient is cheaper, but I doubt its price/quality ratio is any higher than the XLS12". The Peerless is supposed to be a brilliant driver according to many.

thanx guys for the information.

that's what i thought, Xmax isn't everything. If the cone is big enoug, it doesn't matter anymore. certainly if the Q is high enoug. Look at the XLS : only 12 inch; you would need only in surface more than two of them for an 18 inch;

but more important the Q is only 0.2; and with the drivers reported in the previous reply they are 0.8; so off course they need an Xmax of 25mm, because they have to be EQ like hell

You seem to think that Q is somehow related to the required excursion capability. In a sense they are, but differently from the way you're pointing at.

If you EQ a driver like the XLS towards a flatter response, the excursion will go up. However, if you compare the XLS to another 12" driver with the same freq response (obtained without EQ, because Q is much higher), the excursion will be exactly the same, because the only thing that matter is how much air is moved. The max lineair air displacement is Vd (Sd * Xmax). You need 6 Gradient 12" drivers to obtain the same Vd as a single XLS 12" for 1,5 times the cost of the Peerless. In return you get (much) more sensitivity depending on the electrical connection between the units (so you can potentially save a bit on amplification costs). It's also huge... Minimal baffle would be 2m * 0.35m.

It would be interesting to see which one would sounds the best. Both options have their merits. In this case my bet is on the Peerless, because the Gradient doesn't do very well on distortion measurememts.

 

[wunhuanglo]

Hi Saurav

No, I did not include the fact that the sub-baffle is resting on the woofer.

 

[Nuuk]

Thanks RR. It was Mentero that I was thinking of, probably because his woofers are made by somebody with three a name made up from three letters, albeit the wrong ones!

Re the Peerless XLS12. I know this is a good driver but do compare it against the Max Pentivent 1550 for spec, build quality and price. You may be pleasently surprised.

 

[Rudolf]

So you didn't include the baffle area of the lower box when using the Edge simulation program

If a baffle edge is far away from the driver in a OB, it´s influence on the driver response is diminishing. At least in the "Edge". So when I tried to "resimulate" wunhuanglo´s OB, the response didn´t look very different, whether I included the baffle area of the lower box or not.

This makes me believe that Svante didn´t factor in any "on floor" correction, but that his baffles are "floating in the air". Any opinions about that?

Rudolf

 

[wunhuanglo]

I think you're quite correct.

Linkwitz's suggestions for placement of the Phoenix mid-panel (on a stand or suspended from the ceiling) seem to confirm a lack of concern for the effects of additional baffle distance contributed by other boundaries.

 

[Nuuk]

This makes me believe that Svante didn´t factor in any "on floor" correction, but that his baffles are "floating in the air". Any opinions about that?

Open baffle theory - good starting point

Empircal method - only way to get it right!

 

[Saurav]

Thanks guys.

 

[then_dude]

at this moment i'm emailing with the guys from http://www.pa-direct.co.uk/Drivers/b&c%20loudspeaker%20drivers.htm

Nuuk told us that there were nice drivers for little money, and it is true. When i got all the information, i will post his answers on my questions. it's a damn friendly guy who indeed knows what he is talking about.
So within a day or two i'll be wiser and maybe everone else also

greetings filip

ps: Mr tube, aka frank: i have received the cd's yesterday, i will send them to you at friday,

greetings

 

[reins]

JX92S and Gradient 12"

Hi all,

I reached good results with the Gradient 12", its cheap and gives increadible bass compared to boxes or TML. I'm crossing at 160 Hz between the Jordan fullrange and the woofer. Bafflesize ist at the moment 60cm wide and 80cm high. The active crossover has a bassboost from 100Hz down to 30 Hz and an addition 6dB lowpass at 100Hz. The last eliminates the booming in the crossover area. I'm very impressed from the sonic quality of the system.

I have good expirences with using simulation tools from FRD consortium. The predicted results always seem to meet the real live experiments. Unfortunatly I'm not able to measure my system at the moment.

WHat I should mention, I have an addition supertweeter with an 6dB highpass at araound 18kHz to address some shortcommings of the Jordan in the highest hights.


Regards
Stephan

 

[then_dude]

hello,

thanx very much, but probably i'm gonna buy an 15 inch forte if italiavox, the guy says that one 15 inch is more than enough to fill a normal listing room. But he sugest not to use baffle step EQ,
i will try it first, it has an Qts of 0.98 and a fs around 25 i think. We'll see what happes, if it hit 40hz good i'm happy.

But what kind of supertweeter do you have.

I'm looking for a ribbon tweeter, not to expensive and one you can buy in europe.

But has it to be dipole, or doesn't that matter ?

what would you guys advice me ?

thanx a lot

 

[reins]

hello,

thanx very much, but probably i'm gonna buy an 15 inch forte if italiavox, the guy says that one 15 inch is more than enough to fill a normal listing room.

For my room (24 m2) 1 gradient per channel is enouph.

But he sugest not to use baffle step EQ,

i will try it first, it has an Qts of 0.98 and a fs around 25 i think. We'll see what happes, if it hit 40hz good i'm happy.

With a baffle size as mine, the baffle step frequency is near the crossover frequency. The gradient goes down to 30 Hz (Fs) then its over.

But what kind of supertweeter do you have.

In my setup, the tweeter plays a minor role, so it's a cheaper dome tweeter and it isn't a dipole.
I thought of experminting with a crossover frequenzy of about 6 or 8 kHz, but then, triamping is maybe a over-kill there.

Regards
stephan

 

[then_dude]

hello

thanx a lot for the information reins, what do you have for midrange and so ?

you just put the woofer in the bafflie ? can you make some pictures?

maybe i'm gonna make an H enclosure of wide : 55 , hight 60, depth : 50 cm, so i have 100cm wide baffle, so i will have to use baffle step correction if i look at your system.

i have just orderd a full range; a visaton, but it has the conus of coral, i will take picture of it, when i get it. (visaton bought coral, they say, maybe, but it looks like a coral to me, its 16 cm and i wanna put a ribbon on it.

i'm not gonna tri-amp, i don't need much power, and i have only one tube amp( which is broken at this moment) so that i'm gonna use to power the mids and high.

oh yeah what filter and EQ do you use ?
thanx a lot

 

[fdegrove]

Hi,

its 16 cm and i wanna put a ribbon on it.

Visaton also carry a nice little magnetostat tweeter.

It isn't a dipole but SD Acoustics managed to integrate it nicely with an open baffle using an Audax midrange and bass-reflex loaded Vifa woofer in their OBS design.

The tweeter was crossed over using a first order filter at about 12 KHz.

Cheers,

 

[johninCR]

maybe i'm gonna make an H enclosure of wide : 55 , hight 60, depth : 50 cm, so i have 100cm wide baffle.......

I believe that gives you an effective baffle width of 155cm.

Regarding a dipole tweeter; having more HF energy bounce off the back wall would probably do more harm than good.

 

[Rudolf]

H-baffle and baffle step??

maybe i'm gonna make an H enclosure of wide : 55 , hight 60, depth : 50 cm, so i have 100cm wide baffle, so i will have to use baffle step correction if i look at your system.

Sorry, but I can´t follow you guys with this.
If you are doing a H-baffle as I understand it, the (almost) only relevant size is depth. At 50 cm depth this equals (theoretically) a flat circular baffle of 100 cm dia. That means, you need to equalize down from approx. 100 Hz to compensate for the 6 dB dipole roll-off. But there is - by definition - no baffle step in a dipole you have to compensate for.

It might help the discussion if you did differentiate between dipole roll-off and baffle step more clearly.

Rudolf

 

[wunhuanglo]

It's somewhat the same concept, isn't it?

I mean by that, you have something of the same effect. Once the wavelength is long enough to "sneak around the edge" of the baffle you have diminished response.

It's not a traditional use of the term, but is reasonably descriptive, no?