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In the Forum: Horn-Loaded Speakers
In the Thread: Jessie Dazzle Project
Post Subject: Getting loadedPosted by jessie.dazzle on: 1/26/2010
Romy wrote:

"...You are complaining that you have not enough gain in upperbass..."

It is also possible that I'm reacting to a lack of true dedicated mid-bass. As previously mentioned, while the pair of 40Hz horns are under constructon, I compensate for their absence by making the "neighboring" channels (115Hz horn and lower-bass enclosures) work beyond their intended range, which they sort of do.

The room measures about 65-70M², open on one side to another 15M² area; everwhere there are 3M-high ceilings. It is clear that the lower-bass channels can more than load this room in the range for which they were designed (below 60Hz).

"...In your case you run your bass channels from a separate amp and the horn channels from Lamm ML2, right?.."

Correct (M1.1s for the lower-bass, and ML2s for the horns).

"...What you need to go is to find how much gain you need. I do know what preamp you use..."
Currently using an L1, but normally use an L2 (I'm repairing the L2; a tube socket failed and resulted in damage to some capacitors; Lamm sent new parts). I made a voltage divider (attenuator) to place before the input of each ML2, which attenuate either 14 or 16 dB; its been a while since I made them.

"...but as a rule- connect it to the less sensitive horn channel – let pretend that it will be your upperbass..."

It is.

"...Run the channels at it max out and to see how loud it gets. You need to be able to play very loud with your volume control set at 60-70% of the full gain. After you find this configuration then begin to roll off your MF and HF channels until they match your upperbass. I do feel that you will attenuate your S2 quite aggressively. You might even put some 16R LPAD before S2 and to use it for estimates, determining how much you need to attenuate it (do not use it for listening as the LPAD inductance will kill HF). So connect your wide open upperbass and your MF behind the LPAD. Then run a 20-20000Hz sweep and adjust the LPAD until your upperbass will have the same out as your MF..."

This is more or less what I did, though I did it by ear, while listening to music (I have not yet used test equipment to measure the results).

"...Then measured the LPAD’s impedance to one and another side and you will have your resistors for your voltage divider.  Replace the LPAD’s with non-inactive fixed restores of 1W-5W and your will be all set..."

Though I have not yet done it, taking into account the destructive effects of the L-Pads (see previous posts), this was going to be my next step. I may first try using 8 Ohm versions of the drivers in the upper-bass horns.

I'm currently back to using L-Pads only on the lower-mid horns (S2 into 180Hz horns).

"...Where is the volume control setting in your preamp when you run your playback too loud? I presume that it at 20-30% of the full scale…"

Using the L2 with afore-mentioned voltage dividers/attenuators (before the ML2s), the volume setting is usually pointed up around 12 o'clock (50%); a bit more during the day, if the gf is not around. More than that starts to be too loud.

Thanks for your comments,


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