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Old 29th April 2004, 09:27 AM   #21
daniels is offline daniels  Denmark
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I think the problem is my LR circuit. It sounds as if there is a huge drop in dB under 50 Hz. I have not got measurement equipment so I have to rely on listening tests. But my small 2-way loudspeaker with a Scan Speak 9700 and a Scan Speak 8546 seems to go deeper.

When I tested a Scan Speak 8545 it played at very deep levels and I am planning on trading all my 8546 drivers in to some 8545. I would possible get a better result with two 8545 per side in two seperate subwoofers.

By "punch" I was talking about sound pressure. They can give a huge SPL but not as deep as I hoped for. It should be possible to make them go deep by correcting my LR circuit, but I would think it would take a much more complex circuit if not an active one.

I am just not too kean on getting myself into complex/advanced circuits - I want to keep my circuits as simple as possible.
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Old 29th April 2004, 09:44 AM   #22
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Quote:
It should be possible to make them go deep by correcting my LR circuit, but I would think it would take a much more complex circuit if not an active one.
This statement makes me assume that you don't use an LTF at all but a simple shelving filter like 5th element does (a so called lag filter). Am I right with my assumption ?

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Old 29th April 2004, 09:45 AM   #23
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OK well dont give up hope to soon, when I get home Ill have a play with the scan drivers and active filters to and see what I can come up with. LSPcad makes this easy work, what volume of box are you using with the two scans? so i can model correctly. It may be that you dont actually require the whole Linkwitz transform to get the desired result, my XLS have EQ but not a linkwitz on it.

I'd suggest givin it a try if I can get something useful because if all it involves is altering a few resistors or capacitors then you'd rather do that I would have thought then trade em all and build a brand new set of boxes.

Oh and with regards to circuit complexity vs degredation of sound, yes I would agree that the simpler the better, but one transform on the bass section is not going to impinge in any way on the sound quality at all, unless its not working correctly.

So hang in there give my circuit a bash if it works then you have saved yourself a lot more work, and if it doesnt then at least you tried.
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Old 29th April 2004, 09:50 AM   #24
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I wouldnt trade your kevlar ones for the carbonpapers. This is a mistake, both the drivers are high xmax devices and two kevs will have twice the radiating area then one Carbpap. Yes the QTS of the carb is higher then the kev so in suitable boxes for both the carb would play a bit lower, but this is what you are using the active circuit for. Hang in there!
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Old 29th April 2004, 10:10 AM   #25
daniels is offline daniels  Denmark
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I have used a 38,5 litres closed cabinet made from 22mm MDF (57x25x38) but it is propably closer to 35 litres with the internal matrix construction substracted. The volume was a suggestion from another hifi-guru.

I could of course add an acoustic valve or perhaps a port but if I add a port I propably need more volume.

I am using a simple filter without LR gainer - I do not know how to calculate the gainer circuit. I have tried but it sounds really weird...

I have a test CD I use for testing with sinus waves in different frequenzies. At 20 Hz and 30 Hz there is virtually no SPL but the drivers are "pumping". At 40 Hz I can begin to hear something but it is at a low SPL.
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Old 29th April 2004, 03:21 PM   #26
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Well these are two circuits I have come up with they are both optomised linkwitz at 20hz, so have and f6 of 20 and have a Q of linkwitz which is 0.5 i think if i remember correctly, it is entirely possible that i dont remember correctly though.

Give em a blast and see what happens, also what values are you using at the moment??
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Old 29th April 2004, 03:51 PM   #27
daniels is offline daniels  Denmark
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I will have to get back to you tomorrow. I have to order some new components.

But I will try it out as soon as possible.
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Old 29th April 2004, 04:00 PM   #28
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Okedoke, one thing to watch out for is excursion at low frequencies it is going to be quite high to get that kind of extension so just watch out where you set that volume.
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Old 29th April 2004, 04:01 PM   #29
Mudge is offline Mudge  United Kingdom
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I was thinking about using the exact same driver in a >80Hz line array, because I didn't like the way it modelled when trying to produce 'real' bass.
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Old 2nd May 2004, 11:16 PM   #30
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I read this thread, as im considering the 18W as my midrange in a 35 L cabinet!

If you want output below 40 hz , you need a 80 L cabinet and a 10-12 " driver minimum. (otherwise excursion goes balistic) and to use a closed cabinet as a sub, you need 200 liters and x-max of 20 mm!!, if you want to have real output (<100db) below 40 hz...

but thats just my opinion... anyways the point being that a wented solution, and some larger drivers is the way to go (and do yourself a favor and build the cabinets larger)

those scanspeak is to nice to use as a sub, but good (the best?) for midbass (60-500) from what my experience tells me.

(my own bass cabinets is 185 L with sand and JBL 2226H drivers)
works like a charm. only problem is they need a room of more than 8 x 12 meters to have any justification at all. consider that when you build your subs for below 40Hz. And stereo is the only way to go for subs, in my opinion as well.)

good luck (and let me know if you have 2 18W drivers for sale!) i live in Herlev! i can buy for you a LARGE range of (bass) speakers direct via Monacor as a trade in, if you want... they have some nice 'blue line' pro speakers (~ JBL 2226) and some hi tech kevlar as well... PP sucks as a material for bass speakers!)

Anders
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