Is my amp the problem?

My guess is that the Crown amp is going to be really weak in regards to controlling the speaker (even though it’s rated at a higher power) -- Class D circuits can have a problem with weak bass when driving woofers. The Modwright amp is probably going to have a much better overall power supply and current delivery. One quick experiment you can try is to switch around the amps so that the Modwright is powering the woofer and the Crown is powering the mids/highs. If you get strong bass with the Modwright, you’ll know that the Crown is severely lacking. I’m going to guess that the Crown is going to sound weak when driving the mids/highs as well.

If the Modwright does sound better than the Crown when driving the woofer and you still want to bi-amp, you will want to look for a really strong high-current amp. Some thoughts would be to look for a pair of Emotiva XPA-1 monoblocks. For slightly less, you could try a pair of XPA-1L monoblocks (smaller) and then run them in Class A mode. They will still give a smooth/full midbass but they won’t have quite as much weight in the bass (though this difference is very very small).

If you want to spend more, I have heard that Parasound A21 has very strong bass. It may be sweeter/nicer sounding than the Emotiva’s.

Anything less is likely not going to be able to match the Modwright.

@almarg - You are totally correct.  I didn't even think about the miniDSP.  In addition to the input impedance issue, all the miniDSP devices will convert the analog input to digital before doing the crossover processing - then converting back to analog.  These conversion steps as well as the very poor power supply section of the miniDSP will just kill any sound quality benefit you would be getting from the Modwright preamp or audio source.  You would do better to look for an analog-only crossover.  There are a couple of Bryston 10B crossovers for sale on Audiogon.  They have input impedance of 15k ohms, much better than miniDSP.  Also, completely analog and much superior power supply.

That being said, I did think of one more thing.  You should consider any built-in passive crossover inside your speaker.  Are you using a manufactured speaker?  Or something you built yourself (DIY).  The internal crossovers of the speaker will conflict with any active crossover. While you could potentially set the active crossover above/below the internal crossover points, you are just wasting a step.  If you do have internal crossovers in your speakers, you are just better off using a Y-splitter cable to go to two separate amps and take the active crossover out of the system completely.  On a 2-way speaker, you could potentially just bypass any crossover wiring internally and wire directly to the speakers.  If it is a 3-way (or higher), this becomes more complicated because you'll need to have some sort of internal speaker crossover to separate between mid/tweeter.  The internal crossover will have this, but it will also have a high-pass section to rolloff the woofer frequencies.

If you can't control this and it's a manufactured speaker, an idea would be to connect the Modwright amp to the mid/high binding posts and not use an active crossover for this at all.  For the woofer, you could use an active crossover to the Crown amp, but then wire the crown amp directly to the woofer (do not use the internal woofer crossover).  All this will require some DIY work on the speaker to accomplish.

Let me know if I haven't explained these ideas correctly.

Actually, looking at the Crown XLS 1002, it has a built-in low pass crossover as part of its DSP.  You can setup a Linkwitz-Riley 24dB/octave low-pass crossover point anywhere from 30 Hz and 3,000 Hz.  See page 8-9 of the manual.  It does not publish the input impedance, but it -might- be better than using the miniDSP.

http://rdn.harmanpro.com/product_documents/documents/2554_1431029566/5055568_XLSDC2_MNL_PRINT_050615_original.pdf

Taking almarg’s comments...

Emotiva XPA-1 unbalanced input impedance: 23.5k ohms -- means (23k x 23.5k) / (23k + 23.5k) = 11.6k ohms combined.

Parasound A21 unbalanced input impedance: 33k ohms -- means (23k x 33k) / (23k + 33k) = 13.5k ohms combined.

So, comparitively speaking, the increase of impedance when using these amps directly instead of using the miniDSP for low-end will significantely improve the impedance load on the Modwright preamp. That and the fact that these amps are just stronger in controlling the woofer in general would lead me to think that it’s better just to drop the miniDSP out of the mix. I would just use the passive crossovers in the speakers unless you wanted to use something like the Bryston 10B to do BOTH the high and low amplifiers.

Agreed, if you are using active crossover, especially with two different types of amps, you really need to get actual speaker response measurements. This does become more difficult in your own home, unless you build some sort of sound absorbing tunnel (or do something outside aiming the speaker up with an infinite baffle type of area. You’ll need some sort of gain adjustment if you use different amps, or you will have to put in some sort of level adjustment in the passive crossover.  Generally, people who bi-amp will use the exact same amp for highs/lows, but it may be a waste of expense to buy a second Modwright amp. I guess the pro audio amps are good because they do come with a gain adjustment.

You could change to a QSC amp if you wanted to if you look for a Class A/AB.  Pro audio amplifiers are designed to work in extreme environments, push a lot of -general- power to speakers that are extremely efficient (i.e. 98db/watt) and be as efficient with the A/C power as possible. Hence, more Class D/H/I style amps with switching power supplies and fans.  What you want is more of a linear power supply with huge amounts of power supply capacitance and lots of output transistor devices. Usually, this does mean looking for an amp that has a lot more watts (since you need that bigger power supply to be able to push the watts), but it does not mean you have to use all the power. It just means that you have enough brute force from the power supply to drive speakers with low or radical impedance curves.

I have used a Crown CTS600 and a Crown CTS2000. The CTS 600 was a Class AB amp. The sound quality was okay, but somewhat dry. The CTS2000 was definitely stronger and better for woofers, but it was a Class I (Class D variation) and it definitely had some tube-like overtones/colorations in the sound. The Emotiva XPA-1 monoblock was significantly better than either of these Crown amps. Emotiva was totally stronger than either and just sounded better overall. Much more current on tap.

As far as I remember, a Zobel will not change the basic impedance of the speaker. It will still be 4 ohms. A Zobel is to control the rising impedence as the woofer tracks towards the higher frequencies. It’s good to put in a Zobel for the woofer anyways. See this:

https://trueaudio.com/st_zobel.htm

The Modwright is an excellent amp. My suggestions of the Emotiva XPA-1/1L and the Parasound A21 was to try to get a good enough amp to match the resolution/fidelity of the Modwright for the lower woofer registers. You don’t have to spend as much if you don’t want to. You could even go with a single Emotiva XPA-2 (2 channel), or other alternative. In the end, you get what you pay for. Actually, the Parasound A21 has a gain adjustment on the back, so it may work well unless the internal gain of the Modwright is so much higher.

Yes, I would agree that the HCA 1000 would have better current capability than the Crown.  Looks like it has 48,000 uf total capacitance (24,000uf per channel).  Not a huge amount, but the amp is only 100w/8ohm.

http://cd8ba0b44a15c10065fd-24461f391e20b7336331d5789078af53.r23.cf1.rackcdn.com/polkaudio.vanillaforums.com/editor/vg/enhutqtd31pz.jpg

Crown XLS:

http://s290.photobucket.com/user/iso_da_baric/media/IMG_3047.jpg.html

Keep us posted how things work out!

Yep, saw that one.  There's a B4 on audiogon/reno-hi-fi for $995.  I didn't mention it because it actually has a lower input impedance of 10k ohms.  Also, I'm highly suspect about the power supply -- it looks like a basic laptop power supply, so you may have to buy/build a high-quality high-current linear DC power supply to get any sort of performance out of it.    I also read that is uses bare JFET transistors with zero feedback instead of full op-amp circuits.  The JFETS are biased into Class A, so this crossover will definitely draw some power supply current.  I can't comment on the performance of this specific device, but I have seen instances where a bare JFET will sound nice but not have enough brute force to provide enough gain for bass/midbass punch, especially without negative feedback.  JFETs in preamp circuits can sound nice - they tend to have a nice rich/lush type of sonic signature, but they are not as crisp/clear as bipolar devices (this is largely a personal preference on sound signature here).

The Bryston power supply provides +/-24V (for a total of 48 volts), so the analog circuits definitely have a lot of current to play with for good bass/midbass power.  And I confirmed that the circuits are all Class A discrete and use bipolar devices instead of FET based.

There's always the Pass XVR-1, which is probably the best of the best, but at $5k+, I suspect it is out of range here.

The Bryston 10B (that I mentioned above) is likely your best choice for active analog crossover to keep the resolution of your preamp. It has fully discrete analog circuits (probably running in Class A mode) and an excellent power supply. Input impedance is 15k. There’s one on audiogon for $995. They typically sell for well over a thousand.

There’s a Krell KBX for $1360 on ebay. It will probably sound more relaxed than the Bryston, but would probably need to be recapped. Also, the front dials do not show crossover frequency steps, so it will be impossible to determine actual crossover frequency without some sort of mic or line measurement device.

If you want to go cheaper, you could look at a new Ashly XR-1001, but you’d have to use some special cables (either XLR or 1/4" TRS). It is a pro audio crossover, but it is still fully analog (as opposed to digital/dsp like most of the pro audio crossovers nowadays). Input impedance is 20k ohms balanced (this is probably 10k ohms single ended as I can see a 10k ohm resistor on the input of each XLR leg). You can pick it up for $250 at many musician websites (sweetwater, parts express, etc.).

http://s298.photobucket.com/user/maryna1109/media/music/DSCN8468.jpg.html?t=1254515907

The Ashly is not going to be anywhere near the resolution/quality of the Bryston. If I did the Ashly, I would be making significant mods to it. First, Ashly likes to supply power at +/-18V, which is on the high side for normal op amp circuits, but they use normal 7818/7918 regulators. I would be doing the following:

- replace the 7818/7918 monolithic regulators with Sparkos Labs discrete regulators and drop the voltage down to +/-15V.

- Put in the largest power supply capacitors I could fit in the board/chassis (currently they are only 2 x 1000uf).

- Swap out all the op amps with AD797 on dual-channel DIP8 adapters.

- Solder 47uf Muse + 0.01uf metallized poly directly to the power pins on each op amp.

- Replace all the op amp negative feedback caps with film/foil or silver mica.

This is probably $450 worth of components (not including labor).

I’ve seen dbx, Ashly and other analog pro audio crossovers.

Looking at the specs, the gain on these Emotiva amps is 29db, where the gain on your modwright is 26db. If you don’t use an active crossover, you’ll probably want to use a speaker LPAD attenuator (parts express) on the woofers to bring down the level. Or spend more and use a passive preamp before the woofer amplifier.

If you can swing a couple hundred bucks more, there's a pair of New-in-box Emotiva XPA-100 monoblocks over at the Emotiva lounge "Emporium" forum for $550 + shipping + paypal.  These would do better than the XPA-200.  The title is "XPA-100 GEN 2 PAIR BNIB".

Good luck on your amp hunt.

Wow, yeah the HCA1000 could be as old as 1999. Time for a re-cap job! I’ll hang on til the end, lol!

There’s a Emotiva XPA-200 on audiogon for $399. That’s $100 off retail, but amp is probably going to be 3-4 years old max. It has more power supply capacitor bank than the HCA 1000, but transformer is smaller. It’s not going to have the brute force of the larger monoblocks, but it’s definitely cheaper, and I’m sure it will be competitive with the HCA 1000.

Wow, I thought we were looking at cheaper alternatives, lol.  I would avoid the Adcom.  I had an Adcom GFA-545.  It was on the warm/slow side and sounded dirty/smeared when compared to other better amps.

The Emotiva XPA-2 is definitely a contender if you are considering this and definitely better than the XPA-100 monoblocks.  Very strong amp.

I do not have any direct experience with the Wyred 4 Sound (or any other ICE based Class D amp).  Eric Squires likes the w4s, but I cannot give you an opinion on how well it will control the woofer.  It does have a radical 100k ohms input impedance!

Emporium:

- Go to Emotiva’s main website http://emotiva.com/

- Click on "Community" in the menu bar at the top

- Scroll all the way almost to the end. There should be a forum call "The Emporium"

- Scroll down. The topic/listing should still be on the first page and titled "XPA-100 GEN 2 PAIR BNIB".

The Parasound amps are the only stereo audiophile amps I have seen that have a volume/level control.  The older THX certified multi-channel amps all had level controls, and pro audio amps have level controls.  There's a Parasound A23 on Audiogon for $699, but honestly I think you'll get better control with the two XPA-100 monoblocks (and cheaper).  You could always wire an Alps potentiometer directly into your RCA interconnect for the woofer amp.  It looks like there are cheap passive volume preamp for like $50-60 available.

I haven't used ART stuff, but I kind of view them as a lower end item, like Behringer.  Not bad, per say, but definitely inexpensive, with Crown and QSC being better quality (but more expensive also).

Which crossover are you using? minDSP or Antimode 2.0? The Antimode is probably a much better unit then the miniDSP (as it’s 6 times as expensive, lol.), but keep in mind it is still a DSP (which means A/D -> DSP crossover -> D/A). If you like the way it sounds, I’m sure it will benefit strongly from a hefty 12V linear power supply such as this:

http://www.ebay.com/itm/121970182193?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Or many others that are available.  It's hard to say if this will be better than a Bryston crossover, but I know you're trying less expensive options first.