Plugging CMT 340 Ports for better Sub Integration

[sonicboom]

Hi everyone.

Is it a good idea to plug the ports of the CMT-340s in order to achieve better integration with my subs?

Will plugging the ports of the CMT do any harm to the speakers?

Please advise. Thanks.

Daniel

[Dark Ranger]

Hi Daniel,

It sounds like you're looking for the 12 dB/octave slope for smoother integration. However, plugging your 340s is not a good idea.

Here's the reason why, quoted from the Q-Plug thread:



Simply plugging the port of a properly designed ported loudspeaker is generally a bad idea. A woofer that is designed for a ported enclosure will act differently when installed in a sealed enclosure. The compliance of the woofer is not designed to see the internal pressures created by a sealed enclosure and the speaker then becomes overdamped, subjecting the woofer to greater excursions (often exceeding its mechanical limits) and pre-mature bass roll-off. You can also end up with a higher than normal impedance peak at system resonance.


Just curious, what subwoofer do you have?

[sonicboom]

Hi DR,

I have a pair of sealed Emotiva Ultra 12-inch subs. Placement options in my listening area (living room) are extremely limited as a result of a move, so they are actually serving as stands for the CMTs. The speakers are placed on the subs, which are themselves elevated to achieve a "stand" height of 24 inches. I use cut out exercise foam to decouple the speakers from the subs.

My stereo receiver (Sherwood RX-4503) does not provide bass management, so the CMTs are run full range. The subs are connected to the pre-out/sub-out (which I presume sends out full range signal).

For bass management I am using the subs' crossover adjustments, but I am having a difficult time integrating them with the CMTs. I get this muddy and loose bass.

I know it has a lot to do with my room too. I'm looking for tight and punchy bass, so for music I just turn off my subs. Alas, the CMTs don't really dig that low.

I will appreciate all the advise I can get.

Thanks,
Daniel

[RicardoJoa]

You can try and see if itnis integrate better. I have sealed two of my ported and TL speakers with no problema. One thing to be caution is hos loud you listen.
Also, having the avbility to adjust sub distance from receiver works wonder in integrating with a sub, otherwise you will have to look for a right placement.

[scape]

what do you cross your sub over at? try something low like 30 or 40 which the cmt might not play too loudly at. you should consider an equalizer for the cmts, or perhaps it's time for something with more control than your sherwood.

also you might want to try and listen to just your subs, no cmt's, and see how they play on their own in your room at their location. moving and angling subs makes a big impact sometimes.

[davef]

My stereo receiver (Sherwood RX-4503) does not provide bass management, so the CMTs are run full range. The subs are connected to the pre-out/sub-out (which I presume sends out full range signal).

For bass management I am using the subs' crossover adjustments, but I am having a difficult time integrating them with the CMTs. I get this muddy and loose bass.

Hi Daniel,

In your current setup, you are not actually providing any bass management at all because the 340's are being run full range and you are going to have plenty of "double bass" -- which I suspect is causing you some of the issues you are hearing with regard to muddy bass.

Have you considered upgrading your receiver to one with bass management?

Try running the subwoofers by themselves, does the bass still sound muddy to you? If it does, I would suggest trying different locations for the subwoofers or using some form of bass equalization. If the bass sounds nice and tight on the subs without the 340's running, try reversing the phase on both subwoofers and then have a listen...

[Dark Ranger]

Hi Daniel,

Thanks for the additional info on your setup. I completely agree with Dave F. here. I am confident the "double bass" configuration is causing the sound quality issues you spoke of.

I looked up the user manual for your RX-4503. There is little information about the subwoofer pre-out, it simply says: To emphasize the deep bass sounds, connect a powered subwoofer.

I used an old Onkyo 2.1 receiver (now retired) in my bedroom for a few years that created the same issue as your Sherwood receiver. The unit did not provide any bass management control, so I was stuck with "double bass" if I wanted to use the subwoofer pre-out. Of course, I could route speaker level signal through the subwoofer, and then to the speakers, but my subwoofer at the time did not support high-level input. I decided to remove the sub and go "full range" until I could upgrade my electronics.

So, if the CMT-340s sound good by themselves (no sub), and the Ultra Sub 12s sound good by themselves (no 340s), then I would strongly suggest you upgrade your receiver to support true bass management. There are many decent receivers nowadays that can be had without much coin.

In my opinion, no amount of placement, repositioning, decoupling, or room treatment is going to completely solve the issue until the real problem is addressed. You need to have a true low pass filter for proper hand-off to your Ultra subs.

Good luck! :)

[sonicboom]

Guys, you know what? We are in the process of collecting stuff for a garage sale to raise funds to help a friend who's just gone through a kidney transplant. The family is in need of financial assistance so our church came up with a garage sale as one of the many efforts to raise money.

Our house happens to be the dropping zone for stuff, and to my surprise, somebody came to drop a Harman Kardon AVR 110 yesterday. I immediately grabbed it and bought it at garage sale price.

I know it's an old model, but being a 5.1 AV receiver, it has some sort of bass management, that is, being able to set the CMTs to either small or large. My question is, how will I set the CMTs? Small or large? I assume, if my problem is double bass, then I should set the CMTs to small. But isn't this wasting what the speakers are capable of doing?

There appears to be no crossover settings for the sub, so do I use my subs' low pass filter?

Thanks for all the advice. Really appreciate it.

Daniel

[curtis]

Set the speakers to small. The crossover is probably just not adjustable in that model/vintage, so it is probably hard set at 80hz. No need to use the sub's crossover/low pass.

You will need to set the levels correctly for the sub and speakers though by using test tones and a SPL meter.

It is not wasting what the speaker is capable of doing....it is integrating them properly. Think of it as relieving the speakers of some work.

[Dark Ranger]

Since the receiver was pre-owned, it's very likely it's not running with factory defaults. Most receivers have some type of memory backup that allows settings to be saved in the event of a power outage. Typically these stored values will last several weeks, perhaps more.

Regardless, I'd recommend resetting the unit to factory defaults. Here's how:

- Make sure the unit is plugged in, but powered off.
- Press the Tone Mode button and the FM Mode Selector together for three seconds.

You'll see the unit turn on automatically and you should see RESET on the front display. Now you are good to go with factory defaults. Any changes made by the previous owner are now erased.



My question is, how will I set the CMTs? Small or large? I assume, if my problem is double bass, then I should set the CMTs to small. But isn't this wasting what the speakers are capable of doing?

Set the 340s to SMALL since you want to use a subwoofer. The LARGE/SMALL thing can be a bit confusing since it doesn't actually refer to the physical size of the speaker. Whoever came up with that nomenclature must not have slept for a few days. :p

- Use the LARGE setting if you don't have a subwoofer (or if you want double bass).

- Use the SMALL setting if you have a subwoofer and want to redirect low frequencies from the speakers to the subwoofer. So in your case, you want to set the 340s to SMALL so you can low-pass the bass frequencies to your Ultra subs.


Now that the receiver knows to redirect the bass to the sub, the next thing to do is choose the crossover frequency. Most receivers allow the crossover to range from 40 to 250 Hz in either 5 Hz or 10 Hz increments. I'd recommend you start with 80 Hz and work downward depending on how it sounds in your room.

For your Ultra subs, you'll want to set the crossover dial to maximum (e.g. 250 Hz) or just disable the on-board low-pass filter. The receiver will be handling the low-pass job, so the sub will only see frequencies around and below the crossover point.



There appears to be no crossover settings for the sub, so do I use my subs' low pass filter?

Let us know if you still don't see an adjustable crossover after the reset. If so, then it's probably an internal (non-adjustable) crossover. That could pose problems depending what it's set to. The majority are adjustable.


EDIT: D'oh! Curtis posted while I was writing.



EDIT 2: OK, I did some research on the AVR 110, including having a gander at the owner's manual. This model does indeed have a non-adjustable, internal crossover set to 100 Hz. I also dug up the frequency response specs for your Ultra subs. They are good to about 200 Hz, so no worries there.

Even with the non-adjustable 100 Hz crossover, give it a try and see how it sounds. I would not be surprised if it's not as bloated as before since only your Ultras are reproducing the bass.

[curtis]

Jacob is much more thorough than me! :)

[sonicboom]

Happy to hear that David's family is safe in the East Coast after Sandy.

I almost feel guilty having a problem as small as integrating my speakers with my subs. :o

Well, I have set the CMTs to small. All I can say is "WOW!" The clarity and the effortlessness of the speakers are very evident. You guys are right about relieving the speakers of some load.

However, because the AVR110 does not really have good bass management, I am still struggling with my subs' muddy and boomy sound. It seems to me that after I set the speakers to small, there's too much bass frequencies sent through the sub-out.

I'm still trying out all my options, like disabling the subs' built-in crossover; then enabling it and using different crossover points and sub levels. Still I cannot achieve the tight bass I am looking for. I know it has a lot to do with my room and very limited placement options. Sometimes I am thinking that perhaps for my listening area, I might be better off with a smaller sub, like an 8-inch one.

Yes, I am considering getting a better receiver. But in the meantime, I want to get an equalizer for my sub. Can you please recommend a good one? I read about the Behringer Feedback Destroyer DSP-1124P. They say it works well as a sub equalizer.

As usual, your wise advice is very much appreciated. Thanks very much.

[curtis]

Is the sub level matched with the speakers?

It isn't bass management or what is coming out of the sub out that will help with the muddiness or boominess.

[sonicboom]

May I ask how I can listen to the subs only? Do I just disconnect my speakers from the receiver while music plays?

[davef]

May I ask how I can listen to the subs only? Do I just disconnect my speakers from the receiver while music plays?

Correct, simply disconnect one end of the speaker cable going to each speaker (either the positive or negative).

Since you have set the 340's to small and are still getting muddy bass, the issue is really with your subwoofers. This can be room related or it could be the subs themselves. I am not familiar with your subwoofers so I am not able to comment on their performance. Not that I am trying to offload assisting you, but you might try contacting Emotiva directly as they might have a quick fix. I am just not familiar with your subwoofers :(

[sonicboom]

Hi Dave and everyone,

Thank you very much for all the SOUND advice. Everything in your posts have helped me approach the sound that I'm looking for in my system.

I am trying out all of your recommendations, and things are getting better as I tweak.

Again, thank you.

[sonicboom]

Hi Daniel,

Try running the subwoofers by themselves, does the bass still sound muddy to you? If it does, I would suggest trying different locations for the subwoofers or using some form of bass equalization.

Hi Dave,

I would like to try bass equalization. Is there a sub equalizer out there that you can recommend?

[hearing specialist]

What kind of Emotiva sub do you have and have you contacted them? Seems to me that you may benefit from (A) a more advanced receiver where you could reap the benefits all over the spectrum and (B) after checking out their current line of subs and past models all had a crossover control on the back of the sub where you could lower it to remove the room node your experiencing. I would contact Emotiva and get their opinion, they built it and will help you, imo.

[Gov]

Hi Dave,

I would like to try bass equalization. Is there a sub equalizer out there that you can recommend?

Audyssey XT32 or Anti-mode

[sonicboom]

I have come to the conclusion that the weak link in my system chain is my garage-sale-derived receiver.

My next upgrade will be towards getting a new one.
The question will be: what price range of receiver will provide the must-have features in so far as in-room sound quality is concerned?

[natetg57]

I would recommend something like this. http://www.accessories4less.com/make-a-store/item/DENAVR3312CI/DENON-AVR-3312CI-7.2-Integrated-Network-A/V-Surround-Receiver-w/AirPlay/1.html

[DougMac]

The question will be: what price range of receiver will provide the must-have features in so far as in-room sound quality is concerned?
Here's some features I think are essential when looking at a new AVR:
1) Audyssey Multi-EQ or equivalent. Audyssey Multi-EQ offers a better job of EQ'ing, including LFE adjustment. Lower levels of Audyssey have fewer test points and no LFE EQ.

2) Pre-outs. Even if you don't plan to use separate amps immediately, having the option to do so in the future is worth it.

3) Plenty of HDMI inputs. Most newer models have five or more inputs. More and more devices are HDMI, think about your needs.

4) Decent power. This is hard to define, but the more power the better.

5) 7.1 or better. More movies have 7.1 instead of 5.1 soundtracks. I'd love to add another sub, I can do it with my 7.1, but 7.2 would be easier.

Here are some nice to haves, depending on your situation:

1)Phono input. Few AVR's have them and if you have a turntable, there may be better and even cheaper ways to go.
2) Netflix or other streaming connection. I'm double covered. My PS3 as well as my AVR can stream Netflix.

3) Multiple HDMI outs - I only need one, but your needs may be different.

Expect to pay $700-$1000 for a good mainstream AVR. If you go for something more esoteric, like NAD or Lexicon, you can spend anywhere from $2500-$7000 or more.

[sonicboom]

Thanks very much for all the advice and recommendations. Really appreciate Ascend friends here in the community.

BTW, does Audyssey XT provide sub equalization? I'm asking because this is actually my primary problem (muddy and loose bass).

Also, is it necessary to go for the XT32? Or will the XT be good enough?

[kinggimp82]

Here is a link that explains the differences in the different versions of audyssey. The explanation is near the bottom of the page

http://www.audyssey.com/audio-technology/multeq#multeq-solutions

[nzone]

Thanks very much for all the advice and recommendations. Really appreciate Ascend friends here in the community.

BTW, does Audyssey XT provide sub equalization? I'm asking because this is actually my primary problem (muddy and loose bass).

Also, is it necessary to go for the XT32? Or will the XT be good enough?

Not sure if you're still looking to buy a new receiver. I suggest you go browse Magnolia @ Best Buy. They have last year displayed/demo model such as Denon 4311CI for $799 w/10% discount or Yamaha RX-3010BL for $915. You can browse the listings on bestbuy dot com too under "Location". However, some stores don't list opened items online. Excellent deals for these AVR.