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-   -   Running an A7.3 at full power (http://www.diyaudio.com/forums/markaudio/213566-running-a7-3-full-power.html)

Bob Brines 30th May 2012 12:49 PM

Running an A7.3 at full power
 
Running Alpair drivers at full excursion has been discussed here at length. However, nothing has been said about running them at full power when not excursion limited. I am contemplating a speaker that will use two 8" drivers for bass and an Alpair 7.3 as the mid-tweet. The speaker will be bi-amped, so balance is not a problem. The cross-over will be in the 200Hz range, so excursion on the A7 will be well less than 1mm at the full rated 20W.

At 20W, the A7 should be putting out a bit better than 95dB/w/m. I assume that this is an RMS long-term power rating and that there is some headroom for transients.

So, I ask: Is the A7.3 up to this kind of abuse, or do I need to look elsewhere?

Bob

markaudio 30th May 2012 05:34 PM

Hi Bob,
We've ran Alp 7's on signal generators @ 400Hz to +94 dB (1m) with no physical damage to their power-trains in 100 hours lab tests. My suggestion is to trial run a driver measuring at 1 metre with music that peaks around 95dB. Let your ears decide.

Personally, may I ask why drive a low mass unit to emit +95dB? From the many multiway systems I've seen/heard in test labs, their designers won't push vanilla production mid drivers beyond 90dB (ish), even those with fibreglass or kevlar cones. They usually don't sound nice at such elevated levels.

Cheers
Mark

Rullknufs 30th May 2012 06:18 PM

I ask the same question as Bob but about the EL70.
I've been pushing my EL70eN quite far recently but since I have no idea how many dB I am playing I have no idea how much watts I use either since my amp is far from bottlenecking.
How loud can I play them? 4th order XO at ~85Hz and for some music it hits about 3-4mm of excursion (not very often though).

zman01 30th May 2012 06:58 PM

Quote:

Originally Posted by Rullknufs (Post 3042682)
I've been pushing my EL70eN quite far recently but since I have no idea how many dB I am playing

Maybe time to get an SPL meter? Don't risk your hearing young man!

Rullknufs 30th May 2012 07:03 PM

Quote:

Originally Posted by zman01 (Post 3042731)
Maybe time to get an SPL meter? Don't risk your hearing young man!

I did see a digital radioshack SPL-meter for sale for 300SEK a few days ago. Should I buy it?

tuxedocivic 30th May 2012 07:04 PM

Rullknufs, I had an accident while testing my EL70s a while ago. I had the volume up way higher than I thought and ran a full range sweep. I'm not kidding when I say the magnetic grill was either blown or bumped off of the speaker. It made some nasty sounds too. I thought it was gonna be destroyed it sounded so bad. Thankfully it held up. I can't tell that anything is wrong with it.

As for steady state power, I'm not sure. I've never really hammered on them with too high of levels. I played some Santana very loud a while ago. I could audibly hear the drivers struggling. I think you'll hear they're in trouble before you cause trouble. But that might now always hold true :o

planet10 30th May 2012 07:09 PM

Nicklas... do you have an iPhone or Android? My SPL meter is software i got for iPhone (AudioTools from http://www.studiosixdigital.com/audiotools.html), there will be similar for Android no dount.

dave

Rullknufs 30th May 2012 07:11 PM

I do have an Android phone (HTC (Bravo) Desire running Sandvold ICS 0.81 Beta) and I used to have an SPL-meter for it but it proved to be quite inaccurate I think. I tried running it at the post terminal I used to work at and at the loudest place I measured ~86dB peak levels and at that place it's so loud that you can't even talk to somebody standing one meter away from you. I don't trust my phone's microphone.

The Radioshack meter seems to be sold already. But I could make always see if there's anybody else selling one cheap...

chrisb 30th May 2012 07:31 PM

Quote:

Originally Posted by tuxedocivic (Post 3042739)
Rullknufs, I had an accident while testing my EL70s a while ago. I had the volume up way higher than I thought and ran a full range sweep. I'm not kidding when I say the magnetic grill was either blown or bumped off of the speaker. It made some nasty sounds too. I thought it was gonna be destroyed it sounded so bad. Thankfully it held up. I can't tell that anything is wrong with it.

As for steady state power, I'm not sure. I've never really hammered on them with too high of levels. I played some Santana very loud a while ago. I could audibly hear the drivers struggling. I think you'll hear they're in trouble before you cause trouble. But that might now always hold true :o


While we've managed to wrinkle a cone by mishandling, we've not yet proven by destructive testing, but I'd imagine the EL70 to be far more tolerant of this type of accidental or intentional flogging than the multi-form metal coned Alpair7s.

Bob Brines 30th May 2012 09:28 PM

Quote:

Originally Posted by markaudio (Post 3042608)
....Personally, may I ask why drive a low mass unit to emit +95dB?

I am looking at a FAST speaker on steroids.

First, I personally, and most of my customers use an average listening level of 70-75dB, which is going to equate to ~80dB/w/m. While very little is the jazz/easy listening genre has anywhere near 15dB dynamic range, classical music can easily have a 30dB dynamic range. So, it's a matter of headroom.

Second, the bass produced by a large driver feels different from the bass produced by a small driver. I found this out in spades while playing with an 18" h-frame. Therefore, I chose a pair of 8" for the bass. This will provides an Sd of nearly a 12" driver but allows a cabinet width on less than 12". The two 8's will provide 105dB in room at 40Hz. That should be enough to start rearranging the furniture.

I would like to use the A7.3 rather than the A10.2 because it sounds better to me in the treble. Perhaps I need to rethink and go with the A10.2 as it is slightly more efficient and probably more robust.

Bob


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