DIY tri-amped 2226 2445 2405 system update

I figured it was time to do an update on my system in a new thread, since I've made considerable changes. It's still in a state of flux, but I believe moving in the right direction.

The system is comprised of JBL 2226J, 2445J and 2405Js. Previous set up was to run everything through a MiniDSP 2x4 with a passive 8 kHz crossover to the 2405.

Added a new DSP to the system: Xilica XP 4080. I had gone back and forth on what DSP to use. I ended up with the Xilica has I found one on eBay for the same price as a MiniDSP 4x10, and I think the Xilica is in another league. Setup of the Xilica was not as easy as the MiniDSP (software is not as nice), but once it's up and running having the metering on the front and the mutes on inputs and outputs are really nice.

Previously I had been running my 300B mono blocks for the 2405/2445 and a Rotel RB1050. I am now running a Pioneer VSX-D912 after getting some pretty stellar recommendations to do so from AudioCircle. I do consider it a temporary solution, but it is working OK. It's nice to have 6 channels of application in a single device. (My 300Bs need some repairs done to them -- I will likely have them back powering the 2445Js when I get them back).

Once it gets a bit nicer outside, I need to get this out and measure them and tweak the crossover. Right now I am running the following:

2226: LP 500 Hz 24 dB/Octave; +8 @ 35 Hz, Q 1.1 (Thanks, Lee).
2445: 47 uF Dayton Protection Cap, HP 500 Hz 12 dB/Octave; LP 8000 Hz 24 dB/Octave; - Polarity (In Xilica) -- -20 dB Gain
2405: 2.2 uF Dayton Precision Audio Cap, HP 8000 Hz 24 dB/Octave. -15 dB Gain

I have the 2226 delayed by .6 ms and the 2405 delayed by .8 ms.

Next step is to find a better audio rack, get the tube amps fixed, get my turntable hooked back up and figure out more permanent amplification (any suggestions?).

The Xilica has balanced outputs, so I was considering just running 3 power amps -- I had been looking at the Behringer Reference A500.
The balanced outputs and a potential negative of the Xilica in a home system, it would also be nice if it had a digital input. Right now I am running the output of my Apogee Duet into Analog input 1/2 of the Xilica. The Turntable will be in 3/4.

Anyways, would appreciate some thoughts and comments.

Attachment 64808
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I encourage you to go to a full 3-way system with tweeters on their own amp. When you do so, I recommend either an amp with low power if it has output relays (20 watts?). Or any amp will do if it has no output relays. My experience with amps running output relays is that the power required to run those 2405 is so small that it tends to damage the relays. They kinda stick shut. No output unless you really crank the amp to unstick the relays, then reduce volume.

On the woofer, I suggest you test different Q values. Could be anything from 0.8 to 1.1 and it is a matter of taste. For a more natural sound, I recommend crossing to the mid at 12db or 18db per octave. I find that 24db sounds less natural. Especially when crossing at a "low" 500Hz. The Linkwitz-Riley mode has some advantages as the end result remains flat.

And your 2405 deserve better stands. Check my avatar ;-)

http://upload.wikimedia.org/wikipedi...rworth.svg.png

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The balanced outputs and a potential negative of the Xilica in a home system

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No problem at all. You just need XLR/RCA adapters or cables with the right plugs fitted on each end.

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it would also be nice if it had a digital input

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Essential in terms of quality. Adding a completely unnecessary D/A-, followed by an A/D conversion isn't a good idea at all.

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Originally Posted by Lee in Montreal

....... For a more natural sound, I recommend crossing to the mid at 12db or 18db per octave. I find that 24db sounds less natural. Especially when crossing at a "low" 500Hz. The Linkwitz-Riley mode has some advantages as the end result remains flat.
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Hi Lee,

Interesting observation. May be using compression driver with the horn around so low frequency ( 500Hz), driver&horn 12dB hi-pass characteristics 'interfere with' the network 24dB hi-pass characteristics, resulting in such not natural reproduction.
From your large experience, is it the same behavior recognizable if say over 1kHz, 24dB L-R crossover frequency filter is applied.

What about around 10kHz ?

Reagrds
Ivica

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Originally Posted by ivica

Hi Lee,

Interesting observation. May be using compression driver with the horn around so low frequency ( 500Hz), driver&horn 12dB hi-pass characteristics 'interfere with' the network 24dB hi-pass characteristics, resulting in such not natural reproduction.
From your large experience, is it the same behavior recognizable if say over 1kHz, 24dB L-R crossover frequency filter is applied.

What about around 10kHz ?

Reagrds
Ivica

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You are flattering me too much ;-) I don't have a large experience. Just a few observations. I think that at such low frequency (500Hz is maybe low for a comp driver) trying to extend down to 500Hz with a 24db slope is maybe taking the risk of loosing a few dbs down there. While with a 12db slope, you get some content from the woofer. I don't think 24db is a problem at higher frequencies.

As for L-R vs Butterworth, the diagram I posted explains clearly the benefit of L-R's flat response instead of getting a slight bump at separation frequency such as is the case with Butterworth.

BTW our hobby is great as it allow us to try so many options, and what could be heresy for somebody might end up being heaven for another. Give a man (or a woman) a couple of drivers and amps, and he will keep busy all his life... ;-)

Lee

The reason I use 24 dB/octave on the woofer and 12 dB/octave on the midrange CD is because it's already falling off pretty steep below 500 Hz (about another 12 dB/octave). The combined result is a 24 dB/octave slope on both. If I wanted a 12 dB/octave, I'd have to move the crossover frequency up -- perhaps up to 750 Hz. But as you said: give a man a few drivers, amps and DSPs and you can keep him busy for a lifetime.

BTW, I decided to return the Xilica XP-4080 and stick get the MiniDSP 4x10 HD instead. This will let me run full digital in and avoid an extra A/D D/A in my signal path. And I still have an extra pair of analog inputs for my turntable and a volume control should I want to explore some different power amps.

Re: 2405 stands. Lee, do you want to make me some :)?

I really really really need to get these outside and do some quasi-anechoic measurement. Because right now I am just guess or relying on in-room measurements in my relatively small room and I can only learn so much from that.

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Originally Posted by danvprod

Re: 2405 stands. Lee, do you want to make me some :)?

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I have two dozen units on the shelves. They are stainless steel. PM me if you want a set.

Lee

Couple of updates on the system -- the MiniDSP 4x10 HD is working well. I've ordered a pair of aluminum stands for my CDs and some stainless steel stands for the 2405s from Lee. Thanks Lee! They should be here soon.

This weekend I purchased a new amplifier on eBay -- it's a JBL AVA7. Should be perfect for this setup. This is the same unit as the Lexicon LX7 amplifier which is manufactured in the USA by ATI, so I figured that can't be bad.

This will replace my Pioneer VSX D-912 receiver. Currently also trying to sell my 300B tubes amps, although I may test how they sound coupled to the 2445s with the AVA7 powering the 2226s.

Very cool metal stands thanks to Lee:
Attachment 65092

I just received the JBL AVA7 that I purchased off of eBay, but I am a bit disappointed with the amount of hiss that is being put through the CDs and Super Tweeters. Even with nothing plugged into the input, there is a very audible hiss that can be heard at the listening position.

There are no level controls on the amp, so I have to trim the 2" CDs by 18 dB in miniDSP and the STs by 12 dB.

I would assume that this is causing the unwanted noise floor to be heard.

This amp is likely not the best choice for home for the CDs and STs, even though it is a really nice amp. I am bummed.

Would it be stupid to put an l-pad on the horns to act as an output attenuator on the amps?

The more I read, the more I think it was a bad decision to buy this.

Seems like people have had good luck power these types of systems with Crown D-45/D-75a (20/25 watts/channel into 16 ohms), Crown D-660 (25 watts/channel into 16 ohms). Both have attenuators on each channel, which would likely help.

Any advice would be appreciated.

Greg Timbers recommends a 6 to 10 dB resistor pad between the driving amp and the compression driver.

Thank you for the suggestion. I tried a L-pad network on the 2445 this evening (10 Ohm parallel/10 Ohm series) for about 8 dB of attenuation. It definitely helped.

I think the AVA7 is just way overpowering the 2445/2405. Would you agree.

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Originally Posted by danvprod

I think the AVA7 is just way overpowering the 2445/2405. Would you agree.

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2 x 10 watts would probably be enough. Solid state amp on bass and tubes on top. ;)

PS Did you find the enveloppe with the stickers in the box?

Yes I found the stickers :) I still need to put them on.

Yea small tube amp is the right idea for the 2445/2405s. Ordered the parts for the crossover (mills resistors for the l-pads and protection caps for the 2445/2405s).

Is there anything detrimental about using l-pads to improve the noise floor on the amps? e.g. 10 dB l-pad brings my 100 watt amp down to 10 watts (equiv) and drops the noise floor by 10 dB.

I also saw these little tube amps on amazon (3w x 2):
http://www.amazon.com/gp/product/B00...A1V0149CC6WCAD

Might be good to power the 2405s? Or get 2 and power the 2445s with 1 and 2405s with the other. I'd replace the tubes immediately, but seems to be reviewed favorably.

Other option is a d-45 crown amp for the 2405s. I'd prob. still end up using the pad, I would think?