Something Stirs in the Workshop

[pre65]

"Man on the Moon" with numerous references to Andy Kaufman and his Elvis impersonation.

[iansr]

Well that’s probably better than what I had in mind Which was simply that the early stuff was the best in both cases . . .

[simon]

Well yes, that's a little random, but I do agree

[IslandPink]

Well I don't agree with REM, but that's typical with me, hey ho !

[pre65]

I much prefer early Elvis.

[simon]

The early IRS years were quite different from the later Warner years, but any band that makes albums across nearly 30 years will have variety and change. I really like some of the Warner-era albums, but think the really creative era was the indie IRS years. I don't necessarily listen to them that often though.

[vinylnvalves]

Getting back on topic, after Phil takes us off down a rabbit hole.

Connecting a single sub driver up this evening, helps balance things. Have more promise today.

Question. I have got 2 drivers per channel to use. My first thought was I feed each driver independently. Means cramming my spare amp module in the chassis. Am I being OTT and should just wire two drivers to one channel ( 500w). I know in the LX521 the proposal was for to drive each driver independently.

The drivers are the seas http://www.seas.no/index.php?option=com ... Itemid=506
I need to add about 10db of bottom end compensation in on the DSP.

I know Grimm use the same driver for the LS1 DMF sub - driving it with a 700w amp. Contouring it flat to 20hz, which I reckon, needs another 6db. So me settling for 30hz should need less power.

[IslandPink]

Sounds like one for Chris .

[vinylnvalves]

I noticed that the kingro4y speaker designed by seas, uses the xm004-04 driver which I am proposing to use. http://www.seas.no/index.php?option=com ... Itemid=250
They seem to cram it into a 15 ltr box. My calculations were a 36 ltr box for a Q of 0.5, which I think is most appropriate, to then add a linkwitz transform to. What am I missing/doing wrong?

[Scottmoose]

Nothing as far as I can see, other than difference of approach. I assume that since Seas are using DSP, they simply decided that targeting a given 'natural' system Q wasn't a priority / very important.

[vinylnvalves]

Won’t a big box result in less compression, when I force the driver with the Linkwitz transform?

[Scottmoose]

Depends in what context you're referring to compression & how far you're pushing things; as far as I can see you're still not missing anything though since Seas were trying to keep box size down:

One of the design goals of this system is to make the enclosure as small as possible

...while you're presumably not as concerned about that. Just a difference in priorities.

[vinylnvalves]

A morning of messing and listening to the two options, I am considering for the WAM show.
New creation in Dave’s words “sounds like a very revealing studio monitor”. Where as the horns with the planar drivers, more engaging. We were comparing mono v stereo, so it looks like the studio monitor deserves a play mate - so we can have stereo.
The subwoofer, seems to measure very similar if closed box or OB, with similar SQ. Going closed box as I haven’t the room to let the, breathe. Was nervous about running two drivers in parallel, with an impedance of 1.9 ohms, but it was fine.

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Need some assistance from Chris with final voicing, as I get different answers from Holmimpulse and REW..

[vinylnvalves]

The Dayton DATS turned up i ordered...

Impedance check carried out in the leaky cabinet - vents equal to Sd, resistance is 12mm wool felt. The resonance seems to be around 65 hz, up from the free driver at 48 hz. The peak impedance is about a 1/3 of the free driver. I experimented at closing off some of the vents, the frequency goes up, and the impedance drops slightly. A closed box results in a impedance peak of around 80 ohms, with a freq of 77 hz.
Not sure how i achieve an aperiodic loading, but as i am crossing this driver at 100Hz, don't want to raise the resonance to much. Any guidance? Was thinking of increasing the vent size, and making the resistance greater next, as bigger vents will lower the resonance. More resistance should damp better.

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I have some melamine foam to play with too, technically has a better NRC than foam or BAF, i am sceptical, as its pores are very small, that it will work sub 1000Hz

[Scottmoose]

You'll never achieve a flat-line with this sort of box unfortunately, just move somewhat in that direction. The nearest it's possible to get is a max-flat impedance TL, and even those are rarely completely flattened. A couple of general pointers:

• All other things being equal, by blocking some of the vents, you're reducing the damped leakage (moving it closer to being a regular sealed box) so you can expect Fb to rise, along with the Q at resonance

• You can to a point help damp things down by increasing the amount of damping in the vents. However, at very high densities it will eventually act as a solid & move you back toward sealed box loading, so this only goes so far. Vent damping is the 'go-to' initial means of tweaking a leaky sealed box like these though, so use a double-layer of the wool felt you're currently using & see how that goes. If it heads in the desired direction (or doesn't change), add another layer & so on until you reach a point where it starts becoming counter-productive, then back off slightly. At that point, you may want to look at blocking some of the vents again.

• A larger vent CSA in itself = a higher box resonant frequency, although depending on the Qt/Vas/Vb ratio, the total size of the venting & the amount of damping applied, you may (may ) find this cancels out as far as the impedance goes due to the higher resistive losses