Linkwitz transform considerations

[sobazz]

First: I am not planning a loudspeaker at the moment. These considerations and question are for the fun only.

I was thinking about implementing several Linkwitz transform alignments into one speaker/subwoofer - that is having the oppotunity to switch between different alignments according to the listening situation.

Situation one: critical listening - orchestral or organ music. An alignment giving an f3 of 25hz (preferably lower, depending on which driver is used). With Lambda Acoustics SB10 in a 22L box I should be able to output 98db at 25hz, which is suffient for serious listening purposes.

Situation two: Party time. Higher SPL and less need for LF reproduction. An f3 at 40hz would be appropriate, which would give greater output capability in the midbas region and generally allow for higher SPL without the LF stuff. A Q > 0.707 could be desireable. Using the SB10 in a 22L box would give a Q of 1.022 and a maximum ouput of 108-109db (continuous) above 45hz, so an option could be simply to bypass the Linkwitz transform. Listening test will help decide what value of q is desireable.

Hometheater could be somewhere in between... or maybe you would use situation one for hometheater and have a setting in between for orchestral music... I don't know.


But my question is: How could this be done easiest (maybe also cheapest)? For switching I would prefer relais over a mechanical switch, but that is of course not the easiest way to do it.

I suppose you would need several circuits. Switching component values is far too bothersome.

It would also be nice if you could implement an output limiter with different properties for each circuit. Any suggestions?

[tiroth]

I was very interested in LT. When I sat down and measured my sub, though (Shiva, ~2.5 ft^3, Q=0.7, room ~11'x22') I realized that room effects dominated box rolloff even down to 18Hz. If I applied LT not only would I get too much gain about 20-24Hz but the overall response would still be a rollercoaster. I decided what I really needed was a good parametric EQ, not LT. YMMV.

I am currently using a Behringer DEQ2496 for parametric and graphic EQ. My F3 is about 19Hz. One of the benefits is that it is very easy to save multiple curves. I've thought about doing just this but haven't experimented with it as yet.

[sobazz]

Yes, you're perfectly right. It will take time to adjust Linkwitz transform to the room. But I tried to start a thread about the possibility of switching between different alignments - which I do see some use for - and not the LT in general.

It is possible to diy such a circuit. But diy'ing a parametric EQ with the ability to set and save several different sets of values is a h*ll of a lot more difficult.

I'm not too friendly with DSPs... are you?

[tiroth]

I had at one time the necessary hardware and software but with the advent of some of the recent commercial offerings I don't think it is worth it, at least not for IIR transforms.

[sobazz]

No, you're probably right. The Behringer mentionened retails for around 300-400$. I think you would have a hard time actually making one with same features, and it would be expensive too.

But this can't be true! Doesn't anyone have answers for my questions?

[leadbelly]

Originally posted by sobazz
Doesn't anyone have answers for my questions?

But what are you asking? It seems like you are stating what you think is the solution (making multiple LT circuits, and switching them in and out of the live circuit).

[sobazz]

Sorry, if my question was not clear enough.

I asking more specificly about how to make the switch. Will I need to disconnect/connect both input and output of each circuit? Can you do that with two multiplexers? Or would another solution be better?

[Hybrid fourdoor]

What about this simple idea? A DPDT relay that normally is on the "music" circuit, but when a switch sends power to the relay it activates the "party" circuit. You'll still need too seperate linkwitz circuits, but that should only be a couple bucks for opamps and resistors and stuff, plus a switch and relay are relatively cheap.

[sobazz]

Wow.. that's actually quite simple. Thanks. There are many relay types, however. Which type should I use? Some people here on the board have mentioned that certain relay types may degrade sound quality rather significantly.

[Hybrid fourdoor]

Well my take is that a relay is pretty much like a mechanical switch (moot point), but then again some poeple here will tell you rubber feet on the bottom of an amp will raise the "distortion" to unbearable levels

Anyways with the way its connected, the relay will not have any power going through the coil when your doing your real listening, so its setup to be as clean as possible. But we welcome others opinions around here

The only reason I recommend this is becuase its super simple and any cheap switch will suffice.

I would recommend ones that don't "look" cheap...like some of the cheap chinese relays, that look like superglue is holding them together, but anything out of Digikey or Mouser should do fine.

Also one advantage with this circuit is that if the relay fails, nothing gets messed up, you are just stuck on one setting.