New main speakers - Infinity IRS Gamma/Delta

My "new to me" Infinity IRS Gamma/Delta's arrived today from Ft Lauderdale. The speakers were very well packed and strapped to a pallet.

The speakers didn't come with the woofer servo control which makes them the Delta version. They're hooked up in my main system being driven full range by a Yamaha MX-10000 amp. Playing a CD of John Williams classic guitar. They sound really good.

It's been suggested that I bi-amp these, running the low-end with the PC5002M and the top-end with the MX-10000. I doubt that bi-amping could improve anything over the MX-10000 driving the speakers full range. The amps damping factor of 1000 and huge amounts of current (500V µsec) handles the low-end superbly, and it's overall refinement makes it unmatched in my opinion on the top-end. But for grins I'll probably try bi-amping them at some point.



This post has been edited by Mark B on December 06, 2008 01:30 am

you dog. nice score!

as long as you arent bi-amping them, might as well use the PC5002M on the old pair of Quantum II's.

they look prustine. I used a u because I am jealous.

elroy

VERY NICE!

BTW, I have a copy of the technical manual for Gamma/Delta if you need it. According to the crossover schematic it looks like the woofers are driven without any passive crossover circuitry when the servo is used. Without the servo the passive crossover circuit is basically identical to the 9 Kappa (not surprising as the 9 Kappa is basically the same concept with a different mid and mid-bass). This also means that the Gamma/Delta is the same kind of "amp-killer" as the 9 Kappa, especially when in "extended" mode. In fact. the impedance can drop as low as 0.8 ohms at some bass frequencies.

Due to this similarity to the 9 Kappa, I would recommend you give serious consideration to bi-amping. The real benefit of bi-amping is that the current draw required of the woofers, won't place stress on the amp that adversely effects the quality of the mid-bass and higher. At lower listening levels you may be fine with just the MX-10000, as I am with my Adcom GFA-5802 on the 9 Kappas. However, when you really push the volume up, I think you will notice the difference when bi-amped and when not. The difference should be noticable in "normal" or "extended", but most notable in "extended".

Either way, I am interested to hear what you discover.

Rob

Smashing speakers.
Congrats.

Here's a few links:

http://www.bobbyshred.com/infinity/Infinity_IRS_Gamma.html

http://www.bobbyshred.com/infinity/IRS_Gam...nical_sheet.pdf

After playing a couple of CD's it was pretty obvious that the bass level was much lower than the top-end. Setting the crossover pots for the EMIT's, EMIM's, and L-EMIM's to MIN and the woofers to MAX and extended mode still didn't balance the bass & the top-end. The imbalance wasn't due to a lack of power, but simply an inbalance between the power needed to drive the top-end and the low-end. Somehow I needed to reduce the power going to the top-end.

My 1st attempt at reaching that balance was to bi-amp the IRS Delta's with the MX-10000 (250wpc) on the top-end and the PC5002M (500wpc) on the low-end. It was readily apparent that the levels were still unbalanced. The MX-10000 doesn't have gain controls while the PC5002M does, so I switched the speaker connections and tried the PC5002M on the top-end, and the MX-10000 on the low-end. After some experimentation I was able to achieve a good balance with the gain on the PC5002M set to about 40%. The crossover pots are set to the MID point for everything but the woofers which are set at MAX and extended mode. The MX-10000 is easily handling the bass. Not surprising since it pushes a huge amount of current (500V µsec) and is rated at 1200wpc of dynamic power into a 1 ohm load.

These speakers sound great!

Thanks for sharing your Yamaha amp collection. Your large Yammie amp collection is the best!! I can see several hundred pounds of serious iron!!

Thanks Alvaro.

It's my pleasure Sam. It's amusing how small the PC4002M (all 94 lbs of it) looks next to the PC5002M. It's literally dwarfed by it.

Mark: What's sucking up all that power? Is it the electrostatic mid and tweeters? Might be time to double up on either the MX-10000 or PC5002M.

BTW, I'm angling in on my fourth pair of NS-1000M's to complete my "Wall of Sound." The NS-1000M is not as demanding as your Infinities so the humble PC2002M serves me well. I'll finally have all four of my amps running.

Mark, now you know why I needed your other mx2000, so I could biamp my vandies. its all about power baby.

elroy

It's the bass that is sucking up all the power. An AK'er who has IRS Delta's said the speakers should work well being driven full range by the MX-10000. Something isn't right, and it's just a matter of tracking it down. Fortunately the speakers sound great with the set-up I've got.

It's the bass that is sucking up all the power. An AK'er who has IRS Delta's said the speakers should work well being driven full range by the MX-10000. Something isn't right, and it's just a matter of tracking it down. Fortunately the speakers sound great with the set-up I've got.

So you think something is amiss with your Delta's? How about trying the PC5002M on the pair? Perhaps try bi-amping a single speaker with the PC5002M? Could tell you if the x-over needs attention or maybe a re-cap??

When you say "MAIN SPEAKERS", that means they must be impressive, Mark.
Congrats.

dennis

Thanks Dennis, they are impressive and beautiful.

It's the bass that is sucking up all the power. An AK'er who has IRS Delta's said the speakers should work well being driven full range by the MX-10000. Something isn't right, and it's just a matter of tracking it down. Fortunately the speakers sound great with the set-up I've got.

So you think something is amiss with your Delta's? How about trying the PC5002M on the pair? Perhaps try bi-amping a single speaker with the PC5002M? Could tell you if the x-over needs attention or maybe a re-cap??

I don't have proof that there's something wrong, but it seems odd that the bass is so muted compared to the top-end. The low-frequency is there, but the bass sounds like it's running through a -20dB muting circuit. AK'er Numbdiver has IRS Delta's and he says they should not be bass shy being driven full range by the MX-10000. I'm able to compensate for the lower output level of the bass by cutting the gain on the amp running the top-end. When I have some time and the inclination, I'll open up the Delta's and see how the wiring and crossovers look.

Before arriving at the current set-up I tried the PC5002M on the bass and the MX-10000 on the top-end. The bass was overwhelmed by the top-end. There's no point hooking them up to run full range with the PC5002M.

This post has been edited by Mark B on December 10, 2008 01:23 am