WinISD reduce my SPL every time

[oaristys]

Hello,

I try to find what is the best driver for my enclosure. I found many spec sheet and "recommended" enclosure dimension with port size and frequency response on many website.

If i put the specs in WinISD beta, i got a enthusiast curve every-time.

But when i try with WinISD Alpha, the more elaborate, i get about 3 db less efficiency than shpecsheet almost every time. Almost every recommended enclosure is different plot than promised.

Now i have to take an important decision in my project. I have a small thin enclosure and the driver selection will make me decide between one (or two) mini woofer on the back or one bigger woofer on the side. And one woofer will be order over the sea and the other will be buy at few kilometer of my home !

The woofer i'm interested is Silver Flûte W14RC25s04, his 17cm brother and the Monacor SP-60.

The lautsprechershop website have many recommended enclosure with specs and few of them satisfied my need :

490CuIn enclosure if woofer is side mount.
574CuIn enclosure if woofer is back mount. (because i don't need ¾"thick MDF on side.)

Monacor SP-60 is interesting but i got a gigantic difference between the two winISD version. In elaborate version, i need to use two of them to recover the efficiency loss. But the lower bass gone...

Help ! Thank's !

[chris661]

Sounds like you're going to have to ignore efficiency for now.

Use winISD to make a nice response curve, then make sure your amp is powerful enough - you can simply turn it up a bit to counteract the -3dB efficiency.

Chris

[Ron E]

Originally posted by oaristys
Now i have to take an important decision in my project.

WinISD beta basically uses simple equations like you might find at www.diysubwoofers.org WinISD alpha appears to use more complex equations, but I found it slightly different from my reference.

Usually there shouldn't be much difference between the two. Two things that can make a drastic difference are series resistance and VC inductance, because alpha models their effect and beta doesn't. Alpha also actually checks the parameters for consistency where Beta accepts whatever you throw at it.

I'd say try Unibox, but I feel the UI would be somewhat daunting to most newbies. The trouble with all black boxes is that if you don't understand all the knobs and buttons you can get garbage output.

If you want someone to run models for you, you should post parameters or links to them. Preferred parameters would be Fs, Qes, Qms, Vas, Sd, Re, Xmax, Pe, Le

[infinia]

WinISD beta uses what sensitivity you give it ie from the data sheet, so if you use vendor data from 2.83 V/m and then compare it to 1W/m it will be a bit optimistic at low frequencies. I would compare the calculated sens. from the alpha version to Unibox and use those. They will be lower using 1W/m at frequencies where the driver impedance is at minima.

[oaristys]

Originally posted by chris661
Sounds like you're going to have to ignore efficiency for now.

Use winISD to make a nice response curve, then make sure your amp is powerful enough - you can simply turn it up a bit to counteract the -3dB efficiency.

Chris

I understand and thank you for the trick but i have two reason to search another solution.

1. My tube amp is only 35Watt (workin about 20 watts for good sound ?)
2. This driver should be same efficiency as the other in the speaker box. I use a fullrange and search for a woofer to extend the low frequencies in a small 8L stand box.

[oaristys]

Originally posted by Ron E


...

If you want someone to run models for you, you should post parameters or links to them. Preferred parameters would be Fs, Qes, Qms, Vas, Sd, Re, Xmax, Pe, Le

Hô ! you are generous

This is my "finalist" drivers (but probably lot of other can do the job but disqualified because my problem with winISD) I'm open to suggestion here

This speaker is woofer stand enclosure to use with little monitor with Fostex Fe107e (90db)
spec sheet at http://www.solen.ca/pdf/fostex/fe107e.pdf

I will cross over somewhere between 150 and 225hz. The higher is better for power handlinkg but the lower is better for coherency and flatness (i think).


Silver Flûte W14RC25-04 5.5" spec-sheet at http://www.solen.ca/pdf/silver/w14rc2504.pdf

Fs 42.5 Hz
Qes 0.31
Qms 3.70
Vas 19 L
Sd 0.0087 M²
Re (i just have Znom 4 Ohm)
Xmax 3.5 mm
Pe (i just have Power) 60W
Le .52 mH (@ 1khz)

Silver Flûte W17RC38-04 6.5" spec-sheet at http://www.solen.ca/pdf/silver/w17rc3804.pdf

Fs 37.5 Hz
Qes 0.28
Qms 1.52
Vas 25.6 L
Sd 0.0132 M²
Re (i just have Znom 4 Ohm)
Xmax 5 mm
Pe (i just have Power) 60W
Le .53 mH (@ 1khz)

Monacor SP-60/8 ou 4 10cm spec-sheet at http://www.audiophonics.fr/monacor-sp608-p-1197.html

The 8Ohm and 4 Ohm version are identical in specs. I don't know why... And note the SPL is 1w 1m in specsheet instead of 2.88v but WinISD reduce it anyway.

So, when a look to the graph, this driver seems to lost SPL just where i need to cross over it.

Fs 65 Hz
Qes 0.64
Qms 2.10
Vas 6 L
Sd 55cm²
Re 6.5Ohm
Xmax 2 mm
Pe 30W
Le .3 mH

Enclosure
490CuIn enclosure if woofer is side mount.
574CuIn enclosure if woofer is back mount. (because i don't need ¾"thick MDF on side.)

Thank you very much !

[infinia]

Don't forget using BSC, the (combined) woofer response will need to be at least 3~5 dB more sensitive unless you want to pad down the FR driver. Compare the sensitivities using the same method near the crossover frequency. Using normal small bass drivers plan on doubling up and the 4 ohms tap on your amp.

[infinia]

The 8Ohm and 4 Ohm version are identical in specs. I don't know why... And note the SPL is 1w 1m in specsheet instead of 2.88v but WinISD reduce it anyway.

You need to wrap your head around this concept using ohms law.

[oaristys]

Originally posted by infinia



You need to wrap your head around this concept using ohms law.

Sory, i don't understand. I'm french person and i think your phrase use expression we don't use in french

Your precedent message too.

Talk to me like you talk to a 2 years old children and everything will be fine lol


Thank's for your help.

[infinia]

Sorry I don't know your experience
do you know Ohm's law ? http://www.the12volt.com/ohm/ohmslaw.asp


Work through some examples converting 1W/m to voltage when the speakers impedance goes from 8 (Re~6.6) to 4 (Re~ 3.3) ohms.
The constances of (Volt/m<=>Watt/m) as a function in change of resistance.

Using constant voltage (ie.).(2.83V/m=1Watt@ 8 ohms) the sensitivity goes to 2X (double) when speaker goes down to 4 ohms. But using constant power 1W/m the sensitivity stays the same (the voltage is reduced to keep the same power).

You really need to get this idea in your head=mind (brain).