Infinity QRS - Inspired Building These Speakers

[MagicMarksy]

INFINITY RS 2.5 Upgrade In Progress

Hi,

I am in the process of upgrading my Infinity 2.5 loudspeaker system. This is a no holds barred approach that uses all my latest upgrades and I have done so, reguardless of cost.

The upgrade is not completed yet but anyone looking at this can clearly see where I am going. As the upgrade progresses I will upload additional pictures.

I am using 4 MONSOON EMIRM DIPOLAR Midranges per side
and
I use 4 of my special INFINITY DIPOLAR EMIT tweeters ( built from 8 Infinity EMIT tweeters as it takes 2 original monopolar EMITS to make 1 of my special modified dipolar ones).

Here is what I have done so far, starting with the original non-modified speakers for reference.

The panels I am making will replace the original upper portion of the RS 2.5's.

Woofer will remain the same and will cross over to the midrange at 200 Hz.
Midranges will cross over to the tweeters at 8,000 Hz.
You will be able to run them off of one amplifier, or bi-amp them or even tri-amp them if you like.

My completed set will likely be finished by the end of the weekend if you are interested.

 

[buzato]

hello, can you give me all the informations than you can fot the crossover best frequency and slopes for the active filter for the qrs and t3B magneplanar

i use a accuphase f15 with 100HZ and 1500hz but i'm not sure it's the best


best regards

dominique

 

[MagicMarksy]

Cossover Frequencies and slopes

From the Tympani Woofer to the Strathern Midrange theory says 100 Hz should be the target crossover frequency because below this the woofer is omnidirrectional. However, this does not work all that well in real life. The combination of 3 Stratherns together has no problem going down to 200Hz but once you go below this it is streatching it. Also the lower you go the wider the wings have to be to block the rear out of phase wave of the Strathern's from interfering and canceling out the front wave of the ribbon dipole speaker. Consequently a crossover point between 120 Hz and 160 Hz often works best. In most cases I end up tuing the system once it is installed but my most common crossover frequency almost always falls between 150-160 Hz between whatever I am using for the woofer and whatever I am using as the midrange ribbon. So I think your choice of 100 Hz is theoretically O.K. but too low in real life. You will have a dip in the frequency response and also increased distortion in the 100 Hz - 200 Hz band.

From the ribbon midrange to ribbon tweeter I think the best choice is a low of 4500 Hz and a high of 8000Hz. The ribbons all have an excellent frequency resonse up into the 16,000 -18,000 Hz range. Where they are deficient is in their dispersion. The wider the ribbon the poorer it's high frequency dispersion. It is just physics. So a good tweeter is a small tweeter. Many find that they do not need any tweeters at all with most ribbons. Bob Carver Never used any. Bohlenger-Graebner often does not require them in most circumstances. All the tweeter does in almost all these cases is improve the dispersion characteristics of the speaker at the very highest frequencies. They can be very costly (often the most expensive part of the system...if you make a large line source out of multiple of them....and especially is you do my trick of making 2 normal ones into a DIPOLE before you start building your array. At $50 a pop you can go through $4000 worth of tweeters in no short order.....24 Dipole half line source EMITS per side....48 total....would require 96 to start and at $50 each this would be $4800). So your choosing 1500 Hz to crossover the ribbon midrange to the tweeter is much too low in my opinion. You want to move the crossover point as far from 1000Hz as possible as that is where the ear is most sensitive and you don't want a crossover in this range if you can help it. Use 4500-8000Hz as described above and you will be much happier with the sound.

Slopes:

My preference is 24 dB/Octave whenever possible. I often use 48 dB/Octave if I have it available. Occasionally I use 18 dB/Octave, or 6 dB/Octave high pass with a 18 dB/Octave low pass (don't forget the reverse phase of the drivers with these ODD ORDER slopes) when I am forced to, but I much prefer the higher EVEN ORDER slopes when ever they are available to me.

My crossever choices are:
Krell KBX, Bryston 10B-LR (not the other Bryston models...I only recommend the LR ), Peavey CEX4L and PC4XL(a), Yamaha D1030 and Yamaha D2040 in that order.

Hope this helps.

Michael

 

[buzato]

thank you for your experience Michael,

for the tweeters emits for for each panel , there's 13 on the front and 7 for the rear it's the original mogamy wood panel

I will try to find the good cards with the frequencies best adapted

And for the apogee diva have you an experience too?

best regards

dominique

 

[buzato]

thank you for your experience Michael,

for the tweeters emits for for each panel , there's 13 on the front and 7 for the rear it's the original mogamy wood panel

I will try to find the good cards with the frequencies best adapted

And for the apogee diva have you an experience too?

best regards

dominique

you can see my speakers

 

[buzato]

hello, can you give me all the informations than you can fot the crossover best frequency and slopes for the active filter for the qrs and t3B magneplanar

sory i do an error
the good frequencie for the higher is 5000 HZ and not

i use a accuphase f15 with 100HZ and 1500hz but i'm not sure it's the best


regards
dominique


best regards

dominique

 

[buzato]

good evening, I wish to make or to make make an analog filter of very high quality, just for the section acute medium, I do not have any more a filter
it is intended for my acute column media infinity qrs 3 stratem 21 emit
I will use my active filter for the low register

regards
dominique

 

[kcaudio]

another variant of the qrs

Sir, really enjoyed your informative web site. I have a set of home built qrs's utilizing the 3- stratherns and 24- ribbon tweeters in each of the main panels and 9 10" woofers in each of the bass cabs. I did not build them and would like to pick your brain re; problems of speaker loads and amp problems that I am having. Also I have 2 extra stratherns that the builder gave me when one of the original got a tear in it's film, is there an informative site as to the repair of these rare speakers. I love the sound these spkrs present, the soundstage,imaging etc. If you are interested in these as an addition to your site, I will take some pics, thanks ken cochran

 

[buzato]

hello kcaudio, are you use an actif or passif filter with your qrs?

regards

dominique

 

[kcaudio]

dominique, this must be the longest time frame between message and reply that exists! Sorry but I went into hybernation since posting my ??? I am using an active crossover and I am presently not using the system because it has problems with it, if you are still out there I will elaborate upon hearing from you. kc

 

[MagicMarksy]

Just woke up and realized I have not been here for a long time.

Just wanted to say "Hi" again and wish everyone a good holiday season.
Also to let you all know I am still alive and well and as always, building new speakers.

Anyone who wants to contact me can do so at:

MichaelAlanMarks@aol.com (931) 801-2367

If you need any help with your project or repairs just let me know.

I have always been a good free resource.

Michael

 

[BrocLuno]

Thanks for the best wishes Doc, and a happy new year to you as well. We'll be seeing you around the threads

 

[Inspiribomb]

I read this thread with great interest, thank you to all for the very imformative posts. Makes me wonder if I could tweak the crossover on my Infinity Modulus monitors to help open up the midrange.

 

[krokavadet]

Nice reading! Is Michael Marks still around?


Roger Gustavsson

 

[MagicMarksy]

Yes I am here.
Anyone need my help or advice.
I can be reached at:
Michael A. Marks, MD
539 Briarwood Drive
Clarksville, TN 37040
(931) 561-1668 iPhone
(931) 801-2367 Sprint

Hope this helps anyone trying to find me.
Michael

 

[SleeperSupra]

Good job Mark!!!

Thanks for a great thread and for keeping all the very unique projects and imformative posts going!!!

 

[MagicMarksy]

I am still building new speaker projects. [Mod Edit: Removed marketing hype for poster's own products] Hope I can help many of you out too some day. Just get in touch with me at: MichaelAlanMarks@aol.com (931) 561-1668 For now: Michael

 

[elnaldo]

Very interesting reading !:thmbsp:

I'm thinking to build or "re-create" a home made version of Quantum 3, using replacement parts.
I don' t know if this is the right place to ask about that.
Is it possible? What sound quality could I get? Should I go for new replacements, or is better get used infinity drivers?

 

[jimreeves]

Elnaldo, you'll get better response if you start a new thread. But to answer your questions:
Yes, it's possible.
With proper components, cabinet design and construction you'll get excellent sound quality.
In order to get the authentic Quantum sound, you'll at least need Watkins dual-drive woofers, available new from the original designer, Bill Watkins, through his website...
http://www.watkinsstereo.com/
and the associated crossover components, some of which are very hard to find. Sometimes available on ebay used.
You'd also need the Philips mid-bass couplers, the quantum mid-domes and several Infinity EMIT's, also sometimes available on ebay.
The alternative would be something similar to the Q3's with alternate drivers, but to me it isn't a Quantum at all without the Watkins and the EMIT's.
You should be expecting to have approx. $1000 US invested when you're done, none of these parts goes cheap.
Perhaps you could find a used set that can be shipped to you?

Like I said before, start a thread and the rest can join in.

Jim

 

[teknofossil]

Infinity QRS active crossover

Thought some of you may be interested in these 2 schematics of the QRS active crossover. If I were to scratch build this unit I think I'd recommend regulating the +40 vdc and also increase the pre and post regulator capacitance. FYI this schematic is drawn from a Infinity QRS schematic faxed to me from Infinity Systems about 19 years ago. Since the image quality was lacking I redrafted it for clarity. It has been checked for errors so it should be good to go. It has been suggested to me that the E211 JFet may be replaced with the more common 2N5457 JFet but I have not tried it, so proceed with caution. (I believe the originals are Siliconix devices). Anyone considering building this may want to check a good cross reference guide before buying parts. Just a guess most parts could be purchased from Digi Key or Mouser for less than $100 to build this project unless you are after really high end parts.

-Tom