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Discussion Starter · #1 ·
Hey folks!

I am a pretty perfectionist Guy, and this is kind of my Problem with this DIY approach i guess :poop: like in: I know i don't have the best Material to begin with, want to make the best out of it, but learning more and more about it, i feel like i know less and less o_O

Currently using a Klipsch R-120 SW and although thats... okayish.... i am not happy with it for the money.

Speakers are DIY too out of some Focal 165 K2 which also were in that Car back in the good old times.They ended up in a pretty huge enclosure (~40 litres) and i love them!

To the Subs:

Since i am pretty confused about how all the Theory will sound and feel in Real-Life and the obvious gains and losses depending on the design, i was thinking of building both a closed and a vented Enclosure.

I can use them both on a MiniDSP 2x4HD and switch between them for either HT or Music so i get the best out of both worlds (so far my mind construct...)

HOWEVER: When trying to Design those in WinISD, things get a little confusing. For the Enclosed one, the Programm suggests a 27l Enclosure at a Q of 0.707, with a non changeable Tuning Frequency of 49.84 Hz (which is crazy high in my understanding) , but increasing Volume leads to results which i can only interprete as "worse" and tuning freq. is fixed. Am i doing something wrong here? Or am i reading the infos (i.e Transfer Function) wrong?

Vented: Using Chebychev Alignment this looks not bad! With a Volume of suggested 53,67 litres and a Tuning Frequency of 27,03 Hz (matches the Fs of the Speaker even) i am at almost 23 Hz at -6dB.
Is that low enough for Home Theater use? Not sure, but increasingVolume (my max is 120litres) gives me shelv like dips and not really much more in the lows.

I fiddled in a HPF between 19-21 Hz to keep the Cone Excursion in check, but below 20 it still goes a bit over max.
Also i would like to built the Enclosure with a width matching slot port, and it seems impossible to simulate this in WinISD, i am afraid of just calculating the port area and volume and translate that to a diy vent because of the port resonance frequency and other unknowns!?


So, what am i trying to do: I have 2 Alpine SWR-1221D Subs which i used in my Car a long long time ago. Since i am a student again and don't have money for anything, and like fiddling around, i wanted to give those a new Life.

Then there's the Plate Amp Question: there does not seem to be much available. The Subs were driven in the past by a High-End Car Amplifier with plenty of Power - due to Budget i see nothing bigger around the 300Watts Amp Region here though. Phase Control would be nice, LFE/RCE Inputs a must. There are super expensive and relatively cheap ones i saw and i am not sure about amplifiers in the Sub Department tbh as in what to look for etc. I already figured that some are HPFiltered too high for my liking and that some have internal Gain in the Low-End - i don't like it when those components fiddle with that. (Based in Europe/Germany, so availability IS an issue).


Phew, that was a lot and most likely not all, but in short, could somebody be so kind and simulate this too, to nudge me in the right direction or give me some ideas?

i will try to attach some info and could even provide my WinISD file of the Driver, but apparantly only picturework here.

If you need more Pictures of something, let me know =)

Excuse my english btw, i am not a native speaker :alien:
 

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First step is to either get more complete T/S parameters or test the drivers to get those specifications. The above table is missing a lot of data. Example is missing BL which is a measure on how strong the magnet structure is in the driver.

See attached document from dayton audio....
 

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Discussion Starter · #3 ·
I agree that this would be great, unfortunately, there is nothing to be found. The Manual just doesn't have them, and even though the Driver is pretty old i could not find any after Factory Measurements of them! Testint the Drivers sounds great, although i don't know how or where to measure that. Measuring the Magnetic Strength does not sound like my measuring Equippment at home could do ^^
I have a couple of Lab and Handheld Multimeters, a china mini LCR Meter, some Lab Power Supplies and thats about it.:rolleyes:
 

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A quick google search :

Not very precise but get you some numbers to based the simulation on.

I do not know where you are located however maybe some forum member is near you that could test it for small signal response.

Good luck
 

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Discussion Starter · #5 ·
Alright, thanks for the Info, i not would've thought it would be that easy - and honestly, i don't think it is. After watching this the first thing i have to ask: which Parameters do you want me to give you? Because Bl is not covered in the Video (and Tesla per meter will not be a Multi Meter trick either i'd say :confused:) . Secondly: his measurement techniques are more than questionable. even a decent Multimeter has certain reference points of accuracy. Like AC Frequency Measurement at 1kHz with a given Errorfactor etc., and i get the feeling he is measuring a lot of things in a ballpark aka soccer stadium...
I know not that much about measurement tech so i could be wrong though.

Alos, the Subs are not were i live atm, but quite a distance away. I will get there when i have holidays and wanted to have my stuff together to tackle the cabinet building there. That's just for info whough, if i don't have enough infos to do this properly, i just have to do this differently.

Thanks for the help so far =)
 

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My thoughts are that a largish sealed box is quite forgiving. Their VAS is 58L per woofer, and you say you have a 120L max so it would work pretty well to put each of them in a 50 to 60L sealed enclosure and not spend to much time overthinking this. The large enclosure won't absorb huge amounts of power, but you don't have huge amounts of power. It's simple and effective. I wouldn't build one of each type of enclosure. Pick one and build them both the same, you will be happier that way. You have a nice DSP and can tune the system however you want once it's built and put in place in the room.

Also on the amp side, have you considered using a stand alone amp instead of a plate amp? Are Behringer products available at a reasonable price in your area? They are pretty cheap here.
How about used professional amps like Crown, or QSC? Professional amps are a good way to get lots of power for a little money, and doubly so if they are used. Most pro amps are full range, so if you decide you want to use one to drive full range speakers, you can! There are plenty of ways to play with audio but a plate amp can only do one thing where a pro amp can do almost anything.
 

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Discussion Starter · #7 ·
The 120 litres were for for a single box, but you're right, i can't put two super huge enclosures under my Desk while two of 60 litres will fit XD According to WinISD with my current Data i will already hit -3dB at 52 Hz with a painful -16.5 dB at 20 Hz. I can get Cone Excursion under control easily with a 20 Hz 2nd Order High pass though, which is nice. (still -13.5 dB at 20 Hz without that, but since the Speaker will have blown itself to smithereens that does not matter i guess :p )

Can i speculate that room gain or anything else will get those lows up? Because i don't really see a point putting two Subs in my room if they already fall of that much at 50 Hz - this could be the typical theory and practical difference ofc.

With the Amps you're absolutely right. I am already using a PA Amp for my Speakers, and after checking on the availability and quality for the prices given i think i will go the same route here. I wanted them to be Active so i could more easily swap them around (maybe give one to my mom etc.) but given the circumstances that can happen at a later point still if necessary. And yeah, the DSP saves me a lot of headaches in that Departement truly!

Thanks for the help, i am making progress here =)
 

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I don't trust a lot of data from supplier. Most of the actual parameters modeling you will need can be determined by method above and the published data(most of the mass data usually is accurate).

The equations to get all the other parameters is here : Thiele/Small parameters - Wikipedia

Good luck
 

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There are enough parameters to model. I'd put them in roughly 85 liters (3 cuft) or a little bigger and tune to 20hz range. You can go smaller and/or raise the tune a little, it'll sound fine for more HT purposes but won't be a bottom dweller. I wouldn't tune above about 25hz. Use the minidsp to control excursion below tune.
 

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Discussion Starter · #10 ·
Hey! Thanks for the Answer! Are you talking about a closed or vented enclosure with those 85 litres?
 
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