Hornresp & WinISD, xmax difference
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Topic: Hornresp & WinISD, xmax difference
Posted By: Calitri
Subject: Hornresp & WinISD, xmax difference
Date Posted: 21 July 2006 at 4:28am
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Does anybody know, how accurate the Hornresp's diaphragm displacement is? I have an example of the model I've been working at. They both have the same enclosure volumes and tunings but there's HUGE difference between how Hornresp and WinISD models it. I'd be more willing to buy the WinISD's story but I'm not 100% sure.
See for your self: ( 1000 W in both ) http://www2.lut.fi/~kulmala/stuff/xmax_comp.jpg and here's a comparison between 1 bin and 4 bins: http://www2.lut.fi/~kulmala/stuff/1vs4.jpg The design is a bandpass type horn with a 102-105 cm of horn path, so basically 4th order bandpass with a flared port. Now what I'm interested about, is just would I be needing a reflex ports in that design, tuned to around 30-38 Hz. I'm not going to make that design in very long time but I'd like know if anyone has measured the REAL displacement of same kinds of designs so that would the driver bottom out with that power. I know, that the suspension will become much stiffer when going over the xmax but does the Hornresp or WinISD calculate that? I'm aware, that most manufacturers rate they're bass horns a lot lower than the drivers AES rating. For example the Martin WSX is only 600 W where the driver is the RCF L18P300 which has a 1000 W rating. I'd like to know, is that the way they compensate for the lack of xmax? |
Replies:
Posted By: Centauri
Date Posted: 21 July 2006 at 10:35am
| So how did you manage to model any sort of short horn / flared port in WinISD ?? |
Posted By: Calitri
Date Posted: 21 July 2006 at 10:47am
| The front port in WinISD gives a totally different result, so I didn't actually model the same thing. The responces are totally different, I was just interested about the diaphragm excursion. I was just wondering, if the horn/port difference gives the reason for the excursion difference, 'cause it's totally different story to have an excurion of 12-15 mm one way than 18-22 mm! The reason why I used WinISD as comparison is to see if it's really possible to get the driver's cone to bounce to mechanical limit in a small rear enclosure. Logic would say that it's not possible but I'd rather have some first hand experience... |
Posted By: Centauri
Date Posted: 21 July 2006 at 11:03am
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Once you start getting past Xmax, as well as the suspension getting non-linear, there will be proportionately less magnetic force due to less of the coil in the gap. Neither of the simulators would be capable of accounting for that, and I only take notice of Xmax. With a very low frequency (way below box tuning where the air has little cushioning effect) or DC surge / spike, it does seem easy to slam the voice coil into the back plate (or jump it completely out of the gap as I have seen with some JBLs) on some speakers. Some tests a while back by Tamas Tako on the Labsub seemed to show a lower actual excursion than Hornresp predicted for this box - not sure what the general conscensus was with this, or if anyone had tried to do any follow up measurements. At least, if Hornresp's results are very conservative, then designs based on it should be pretty robust. Cheers Graeme |
Posted By: Timber_MG
Date Posted: 24 July 2006 at 4:12am
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WinISD doesn't take some resonant effects into considderation and sees the port as only a mass-spring system (i.e. no acoustical length). However there is definitely a resonant-pipe system in play here and hornresp takes account of this. @Centauri: a pipe resonant system doesnt' care about the position of the vc in the gap and thus whatever "reflected energy" (horrible word) in the system ends up exerting a force in the same direction as the cone travel can make a woofer move further than it would unaided. If the opposite is the case you have large radiation impedance (which hornresp plots btw) and a resultant excursion minimum. I know that hornresp indicates peak excursion and AJHorn RMS excursion, but iirc WinISD also indicates peak excursion. |
Posted By: Calitri
Date Posted: 24 July 2006 at 10:34am
| Well, not yet The Answer I'm waiting. What I'd like to know, if you look at the excursion graph, is that IS IT possible to have so high excursion right below the horns loading. It just seems so surreal, that the excursion is at it's highest at 37 Hz and much smaller at 20 Hz, when in practice it's the opposite. I've never ever EVER seen my entire life, that cone excurions would so spiky. Like the way Hornresp models it, minimum at 65-66 Hz and 5 Hz lower it's already 12 mm one way. That's the problem, what I'm trying to find out. Is the excursion really that spiky & huge, which I doubt it, or is the horns cutoff point so drastic. I'd be more willing to belive the WinISD prediction, 'cause that's the way I've always seen it to behave: below tuning frequency you lose smoothly the control, not like on/off type of way. |
Posted By: Timber_MG
Date Posted: 24 July 2006 at 2:48pm
| Read up on the bahaviour of a pipe that is open on one end and imagine the pressure exerted at the driver end and it's relative phase to driver movement. This is an exersise that aids tremendously in undertanding of how most (undersized) horns load a driver at the botom end of their bandwidth. |
Posted By: Contour
Date Posted: 24 July 2006 at 5:37pm
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Hello Timber,
I remember myself comparing cone excursions from AJ and Hornresp. It amazed me how much they agreed. But that has been some time ago and it may be true that one of these programs has changed so that they now differ in this aspect.
Best regards,
Walt
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Posted By: JD01
Date Posted: 24 July 2006 at 6:01pm
| It's a simple thing: If the response is different, because the design is different, the excursion values will be different too. Excursion does heavily depend on the cabinet. |
Posted By: Jay Lawless
Date Posted: 25 July 2006 at 3:13am
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also take into concideration, whats the driver's FS?...
ever think that just maybe hornresp is taking into account that the driver will move out of control below it's FS? concidering it does ask for it specificaly for atleast one of the inputs. just imagen for a moment a nice highpass at atleast 35hz, a big drop and with no more worries. ------------- Previously known as NeverWinter Background: Automotive, Live and Home Custom Design. mid/high level based design and feild experience. Bass specialist |
Posted By: Calitri
Date Posted: 25 July 2006 at 6:04am
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NevewWinter: The design is based on RCF L18G400/P300 drivers, so the Fs are 28 Hz for the G400 and 33 Hz for P300. I know there has to be a highpass, that's natural of course but that 35 Hz highpass wouldn't do the trick, 'cause then the lowest EQ point would be around 50-60 Hz. What's the point of making 18" horn, if it can't go lower than 60 Hz?
I appreciate all your answers but STILL, there's something missing. Let's take another example: has anyone seen or found out the excursions of Turbosound TSW-218 or Funktion One F218 or horns of the same kind? I haven't personally seen or experienced neither but a friend of mine has. He's been working with F1s and he said that the drivers don't bottom out even with double power compared to the cabinets RMS power. And the thing is, that the highpass for F1s is 24 Hz and they use lowest EQs around 30-40 Hz. So that would indicate, that the Hornresp exaggerates the horn's cutoff point in terms of cone excursion. So that's what I'm interested. If I someday get enough money/time to start making them, I wouldn't want to find out how much they can take a beating by trial and error. Does anybody have a clue of the cone excursion for this design? http://www.speakerstore.nl/index.php?l=en&pg=11&c=16 My plan is kind of same type, just a little longer path. |
Posted By: JD01
Date Posted: 25 July 2006 at 8:03am
| @ Calitri: Could you explain what you mean by 'lowest EQ'? I don't understand what you mean. If I set a highpass at 35Hz I still can use EQs at 20Hz..... |
Posted By: Jay Lawless
Date Posted: 25 July 2006 at 11:57pm
ahh see now i don't know much about many of the RCF drivers so...
but also, don't go by what winISD says for Xmax modeling, it's ok to a point, but Hornresp will give you a more accurate model.
but at the same time, this is why i mention the crossover comment. whats the point of worrieing about those low ends when you'll be crossing them out anyway...? unless you're trying to design one REALLY long horn to get some subsonics going on in an install system, then theres no need to worry about the Xmax smikes that Hornresp is giving you at such low points...
this is just my own personal opinion. i know that you still want to find out about this, but it just seems pointless to me...
------------- Previously known as NeverWinter Background: Automotive, Live and Home Custom Design. mid/high level based design and feild experience. Bass specialist |
Calitri wrote:Posted By: Calitri
Date Posted: 26 July 2006 at 3:45am
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JD01: My bad, a bit of a wrong word for the point. I mean, that F1 recommends for the EQ points to be in the region of 30-40, depending on the size of the stack. Of course you can have what ever EQ points in your system but that's the reasonable point, below which there's no point of EQing.
I'm trying to get the system to reach 40 Hz maybe around -3 to -5 dB range in a stack of 4 w/o EQ and with EQ 0 to -3 dB. But I can't do that if the tweaking causes the voice coil to hit the back plate at full power. Of course there would be a highpass of 4th order BW around 35-40 Hz. Neverwinter: Thanks for the information I've been trying to get. So the Hornresp IS quite accurate. I have experience of RCF drivers and they are awesome. We have in our universitys rig, which we built some time ago. They are reliable drivers which can take a helluva beating. I recommend them. I can post my "Great" plans, if somebody's interested and has enough money/time to build them. |
Posted By: JD01
Date Posted: 26 July 2006 at 12:20pm
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WinISD pro doesn't take all the dampening effects of the enclosure in account. So the excursion displayed by WinISD pro will be a bit higher than in real world. Close enough to get the point, but not fully accurate.
Hornresp uses physical modelling of the 'mechanics' going on, so the result will be as good as the physical model used. As far as I know it's pretty accurate with HornResp or AJhorn.
What F1 does is rely on the technician to keep an eye on everything. If the highpass is set for 24Hz and someone plays a very loud 30Hz signal, it WILL bottom out. They rely on the fact, that usual music won't have such content on high intensity....
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Posted By: Jay Lawless
Date Posted: 26 July 2006 at 5:33pm
i would recommend PMing the plans to whom may be interested, just incase it does actualy work very well, you can still have some ability of copyrights before some Rep of some company gets the idea to copy it and call it their own.
i my self would like to see this cab you'r designing, PM it this way! ------------- Previously known as NeverWinter Background: Automotive, Live and Home Custom Design. mid/high level based design and feild experience. Bass specialist |