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Recommendations for balancing gain in bi-amp setup

I've been trying to calibrate my setup where I have
PS PWD Dac-> Joules Electra LA150 MKII pre -> Celestion 6000 crossover (treble, mids)-> Ampzilla 2000 MKII -> Celestion sl600 monitor ; Celestion 6000 crossover (bass) -> Mccormick DNA 500 ->Celestion 6000 subs.

The Celestion 6000 is a monitor/sub configuration and requires bi-amping. Both the monitor and sub have low sensitivity, ~84db and power handling up to 100W@8ohm. These are hard speakers to drive but I felt my Ampzilla and Mccormick combo should be up to the task.

My challenge right now is that even though the Mccormick DNA 500 which I'm using to drive the bass is rated at 500w@8ohm output and the Ampzilla is rated at 300W@8ohm. I'm still finding the bass playback from this setup is light and thin
or put it another way that the highs/mids are too bright.

My theory for now is that this may be due to the different sensitivity of the amps and I'm trying to avoid throwing another component in the mix like a equalizer to sync this.

Would like recommendations from anyone who has face such gain/sensitivity challenges before when bi-amping.

Gerald
geraldedison
11 responses Add your response
kr4's avatar
kr4
3,678 posts
 
The output power (real or advertised) has nothing to do with the sensitivity or gain of the amps. There are really only three ways to deal with it:
1. Use identical amps (or ones of identical sensitivity)
2. Use amps which have gain or input sensitivity controls
3. Insert voltage attenuators at the input of the more sensitive amps. (In your case, that seems to be the Ampzilla)

You might also consider getting an AC voltmeter and/or a sound level meter to measure the actual outputs.
almarg's avatar
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almarg
9,670 posts
 
I second all of Kal's comments, except that according to this review the crossover unit includes a level adjustment provision, at least for the subwoofer. Won't that enable you to equalize the gains?

Regards,
-- Al
marakanetz's avatar
marakanetz
5,473 posts
 
I'm lost here since having crossover should give you an ultimate controll over the gain of your amplification devices. You have to get manual on proper setup or get some troubleshooting from the manufacturer itself that is still in the business to help you.
jeffreybehr's avatar
jeffreybehr
805 posts
 
I certainly agree with the question--doesn't the crossover have have gain controls? If so, turn the upper-freq. level down or the lower-freq. level up.

Kr4, re your #1, what the OP might need are amps with equal VOLTAGE GAIN and not equal sensitivity. The latter is almost always stated as Voltage required for rated output. One can calculate Voltage gain from stated sensitivity, but the 2 sensitivity numbers aren't usable by themselves.
.
almarg's avatar
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almarg
9,670 posts
 
Kr4, re your #1, what the OP might need are amps with equal VOLTAGE GAIN and not equal sensitivity.
+1. Should have spotted that myself.

If BOTH sensitivity and rated maximum power are the same for the two amps, then gains will be equal, to a reasonable approximation (assuming the specs are accurate and are defined in the usual manner). If those numbers are not both the same, gains may or may not be equal, and most likely will be different. Gain can be calculated from the other parameters, to a reasonable approximation, as described in my last post in this thread.

Regards,
-- Al
geraldedison OP
36 posts
 
Thanks for the suggestions posted.

The crossover does have a gain control but at peak it offers 3db from what I've read. However, at the settings of 9 or above, the tight bass which makes these speakers great become boomy and clearly not flat. So I keep it at settings of 8 or below. I believe gain at that setting is 2db or less. Thus the resulting gain imbalance...

I have many amps but none of the same brand or model.

I have a multimeter, but would need tips on how to measure volt gain/sensitivity of my amp with this.

Looks like the simplest route for now is to look into attenuation. Is there a formula for calculating the attenuation I will need to balance the voltage gains?

Gerald
geraldedison OP
36 posts
 
I looked up the input sensitivity of my two amps:
Ampzilla 2000 = 1 volt R.M.S. across 50kohms for 300 watts into 8 ohms on the unbalanced input.

Mccormack DNA 500 = Input Impedance: 10 kOhms
Input Sensitivity: 2.25 volt rms

So it seems the mccormack is less sensitive than the Ampzilla and if I am concluding properly, the Ampzilla @300W will have more gain than the Maccormack @500W.

totally not what would have expected, but this would explain what I'm hearing.

I will try to switch it up and use the Maccormack to drive the monitors and see if I can balance out the gain by lower the crossover setting.
geraldedison OP
36 posts
 
that seem to have done it.

I switch the 300W ampzilla to drive my bass and use the 500w Mccormack DNA 500 to drive the monitors.

Instantly, the missing bass appeared in spades to the point I now set my crossover gain to just between 5-6 and all the mid-bass and bottom end is solid and tight.

I just need to find a good way to tweak the crossover gain to balance the output of the monitor vs the subs.

Thanks Al for the thread that help clarify for me the difference between input sensitivity and output gain.

Gerald
almarg's avatar
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almarg
9,670 posts
 
Glad there was a simple solution. As you've probably already calculated, based on the methodology presented in the post I linked to the gain of the Ampzilla is about 33.8 db, while the gain of the McCormack is about 29.0 db.

Enjoy!
-- Al
ngjockey
1,042 posts
 
http://www.goldpt.com/bal_amps.html

Goldpoint used to carry a limited range, mono, 10K, high precision (1 or 1/2 dB step, if I remember correctly) that would be ideal for this purpose but I can't seem to find it listed now.

If you do go this way, they should be close to the amps.
geraldedison OP
36 posts
 
Thanks Ngjockey, I'll keep that in mind and research what the goldpt offeres.

Gerald
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