How to: active bass section

[R1200CL]

I replaced both front and rear woofers on my Odysseys when I I went to active crossover on them. On the 8”fronts I went with Seas replacements, and on the rears I went with Dayton

I assume you’re still using the passive crossover between them, meaning you feed both from the binding posts?

Same amp as Brandon ?

 

[Brandon Hartwick]

I assume you’re still using the passive crossover between them, meaning you feed both from the binding posts?

Same amp as Brandon ?

No, the entire point of doing this is to NOT use the passive crossover. The passive bass crossovers in most ML speakers are crap, that's why we go digital.

 

[R1200CL]

No, the entire point of doing this is to NOT use the passive crossover. The passive bass crossovers in most ML speakers are crap, that's why we go digital.

So you parallel connect the woofers then ? No matter the impedance

 

[DanR]

No, I have 1 amp to power the two front woofers (behringer KM750)and another amp to power the rear woofers (Crown XLi 800). You can match the gain on the woofers with the gain controls on the 2 amps and also using the DSP processor Behringer DCX-2496. So on the back of the Odysseys I have 3 pairs of binding posts 1pair for the front woofers, 1 pair for the rear woofers, and another pair for the panel. The woofers are completely out of the crossover circuit, that is all handled by the DCX-2496. The sound improvement and adjustability is not a small improvement it is major, Brandon is correct the factory woofer(bass) crossovers are just plain awful. I’ve attached pics of the amps and DSP unit

 

[DanR]

A couple other things. You don’t have to remove anything from the factory crossover when you do this. I just disconnected the crossover wires from the bass factory pair of binding post and isolated them in the enclosure. Then added another pair of quality binding posts, then wired the front woofers to one pair of posts and the rear woofers to the other pair of posts. The signal comes from the line stage preamp to the DSP 2496, then to the woofer amps, then to the woofers. The two amps are both pro class A/B amps that run nice and cool. I use 8ohm rear woofers and 4ohm front woofers the amps both put out 200watts per channel one at 4 ohms and the other at 8 ohms, which matches my main Krell amp for the panels that puts out 200 watts per channel @4ohms

 

[DanR]

And as you can see I do not use the same amp as Brandon, but the amp he uses is really nice in that it eliminates the need for the dsp unit. That is all handled within that amp, it simplifies things a lot

 

[Brandon Hartwick]

And as you can see I do not use the same amp as Brandon, but the amp he uses is really nice in that it eliminates the need for the dsp unit. That is all handled within that amp, it simplifies things a lot

I actually really wanted that same Behringer DSP unit but it was made of unobtainium when I was shopping and I couldn't buy one anywhere! Dayton then released there 4X8 DSP unit in a nice format factor and for under $300 so I ended up with one of those.

 

[DanR]

It’s crazy how some things just disappeared for a while there, I had the same problem when I went to get the second amp for the woofers I had a Behringer KM750 so I figured I’d just get another so they matched but nope no way couldn’t get one anywhere so I bought the Crown. Now the DCX-2496 I’ve had that since I bought it new in June of 2010 when I set up my multiple sub system, I love the thing!

 

[Asepguy]

Anyone done a mod like this for the ReQuest model? Only a single front firing woofer on each cabinet so just the amp should be all that’s needed. Manual says the factory crossover frequency is 180hz. Are the other models that much higher that you are setting it to 450?

 

[Russr]

Hi AG. The OP on this Thread (@Brandon Hartwick) originally started this thread describing how he "ACTIVated his Aerius speakers... they are similar (but smaller) than your ReQuests. He has quite a bit of good info in this thread & others. Don't despair - I think you will find the answers you need on here, and hopefully just have to tweak the active crossover points for your speakers.

Good luck!

 

[JonFo]

Manual says the factory crossover frequency is 180hz. Are the other models that much higher that you are setting it to 450?

When adjusting the settings for panels, it is often necessary to use values higher than the factory settings. This is because the original settings are usually set at a level that is not realistic, and actual measurements often show that the panels, even those that are large, tend to roll off sooner than expected.
For a ReQuest, a setting of 250Hz with steep slopes is recommended, although it may be worth experimenting with a setting of 300Hz to determine which sounds better.

 

[Brandon Hartwick]

Just buy a Crown amp of basically any size with active crossovers and you're golden. You could do it with external active crossovers and seperate amps but that's really just adding complexity for no reason.

The thread has lots of info so you should find everything you need here.

 

[Zwick]

Just buy a Crown amp of basically any size with active crossovers and you're golden. You could do it with external active crossovers and seperate amps but that's really just adding complexity for no reason.

The thread has lots of info so you should find everything you need here.

Finally passively biamped my QuestZ with a Crown XLS 1502. Still subject to the stock 125 hz crossover that causes the upper bass suckout and contributes to QuestZ lean sound (per Stereophile) but otherwise pleased. Next step to bypass the bass crossover and rewire binding posts direct to woofers. Great advice and info from a number of members. Thanks.

 

[JonFo]

Finally passively biamped my QuestZ with a Crown XLS 1502. Still subject to the stock 125 hz crossover that causes the upper bass suckout and contributes to QuestZ lean sound (per Stereophile) but otherwise pleased. Next step to bypass the bass crossover and rewire binding posts direct to woofers. Great advice and info from a number of members. Thanks.

Awesome, glad to hear that's making progress. You will be amazed at the difference once that bass XO is removed.

 

[Zwick]

Completed the bass XO bypass and added new binding posts for the direct woofer connection leaving original XO wiring in place. Set the Crown XO at 200hz and really pleased with the improved bass and meat on the bone sound. Will experiment with the XO and gain but so far big improvement. Earlier tip using a hammer and box cutter blade to help remove the back panel was key. Obtaining insulated binding posts for the metal back was also a necessary element.

 

[Brandon Hartwick]

@Zwick I'm glad you found this guide helpful and are enjoying the sound, it really does make a substantial difference. I'm glad more people are breathing new life into these older but still fantastic speakers.

 

[wensean]

Yes, ESL is perfect to go Active Crossover IMO.

 

[Dobbler]

Anyone with experience doing active crossover on the low end on a set of reQuests? Any gotchas or things to look for? How does one determine if the bass drivers are still "good"? I've owned my set since the first month they were available in 1996! What are the crossover settings if I were to use a Crown XLS amp for the low end?

 

[Brandon Hartwick]

Anyone with experience doing active crossover on the low end on a set of reQuests? Any gotchas or things to look for? How does one determine if the bass drivers are still "good"? I've owned my set since the first month they were available in 1996! What are the crossover settings if I were to use a Crown XLS amp for the low end?

Any single bass driver Martin Logan will follow the same steps as what I originally detailed. I believe the owners manual has the factory crosso specs listed so I'd use that as a good starting point and you can tweak it from there.

If the woofers still play as they should then there's nothing to worry about, don't mess with them. They will automatically sound much better after implementing the active crossover anyway, the speaker does what it's told.

 

[Fredrik Kansbod]

First post here in this forum. I have lurked around for some weeks after purchasing a used set of ML reQuest's.
My first impression when hooking them up to my old system (Yamaha Home Theater gear as a pre and a Quad 405 II to drive the ML's) was disappointing. I know the ML's need another amplification so I'm not that worried. But, what should I invest in?

This thread gave me valuable info on the passive crossovers in reQuest speakers and inspiration to move to active crossover and bi-amping!

Since a few years I'm mostly using digital media but occasionally also use vinyl or other analogue sources.
As far as I understand the desribed method with a Crown amplifier with DSP will introduce two additional signal conversions (by having active crossover in the same unit as the power amplifier). I mean, the power amplifier is fed with an analogue signal (at least if a Crown amplifier is used) and the crossover needs digital signal to "work with". So a conversion to digital, processing the filter settings and then conversion back to analogue will be required.

I do believe that the improvement in sound quality still will be noticeable but wouldn't it be even better to have the active crossover while still in the digital domain?