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Truth in monitoring -Bass reflex vs. closed cabinet designs
Old 14th February 2003
  #1
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Deadly's Avatar
 

Truth in monitoring -Bass reflex vs. closed cabinet designs

I have been recently testing the quality of certain types of digital to analog convertors, aside from the width of the stereo, and overall clarity, one key element is the "tightness" of the bass signals.
Which raised another another little problem when listening for this aspect in the recordings I monitored.
I had a hard time with this when using a bass reflex design because I had the impression the ports on a well-known pair of monitors we skewing the bass frequencies, which was confirmed when I plugged in a pair of closed closed cabinet monitors.
Switching from an internal clock to an external clock of a more expensive convertor set, gave a "tighter bass" that was more evident on the closed cabinet design and not to the same extent on the others.

Most speaker designers will swear that the ports are in phase with the woofer(s) but my experience here says otherwise as I heard the "smearing" .

Is it true that closed cabinet designs need up to twice the power from an amp to get the same SPLs of a bass-refllex design? Is this why we now have a ton of ported designs on the market?

What is our guarantee that the ports are in phase with the woofers?

Isn't it inherently better to monitor on closed (non-ported designs)?

I recently saw and heard a pair where the port was rear-facing, it was awful.

Any comments?
Old 14th February 2003
  #2
Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by Deadly

Is it true that closed cabinet designs need up to twice the power from an amp to get the same SPLs of a bass-refllex design? Is this why we now have a ton of ported designs on the market?

What is our guarantee that the ports are in phase with the woofers?

Isn't it inherently better to monitor on closed (non-ported designs)?

I recently saw and heard a pair where the port was rear-facing, it was awful.

Any comments?
I've posted on this topic in the past.

Here are some of my opinions.

First of all, if the closed cabinet is designed correctly(and there are different designs) than the SPL shouldn't be a problem.

Bass reflex is employed because small nearfield monitors in theory cannot put out low frequency information. It also skewers the bass some what(based on reflections around the cabinet which can if not setup right create standing waves around the listening area). It has almost become the norm in modern small/midfield studio monitoring because people want more "bass" when they are are producing their records. Instead of using a sub(which is a tricky setup in itself. Most times to get a true bass wave you need a double sub).

I've always prefered non ported designs for mixing(NS10's and Dunlavy SM1). My favorite powered monitors were also non ported(the older ATC SCM20P and 50), but on the above monitors(with the exception of the Dunlavy which is a D'Appolito design) I always heard from people who listened to them that they wanted more bass(go figure, that is why the new ATC's are all ported or dual ported. Sounds totally different).

Rear ports work off the reflections from the back and side walls(which by the way is a common thing). The best rear port designs lets you rotate the bass(or sub) so you can put them out of phase if you like and tone down the bass frequencies.
Old 14th February 2003
  #3
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Roland's Avatar
There are always compromises in all speaker designs, it could be you have a very well designed IB and a not so well designed reflex cab. I've heard great designs from all camps.

Only problem I have with IB's is the way they can "knock" when driven hard. A lot of designers will talk about how inert they make their cabinets to stop resonance, but then the weakest point of any cab is the driver cone itself.

Go figure?

Regards


Roland
Old 14th February 2003
  #4
Gear Nut
 
sounddevisor's Avatar
 

Thrillfactor -

Just wanted to point out that the new ATC SCM20 powered monitors (SCM20ASL) are not ported - and man do they sound great!

The ATC T-16 looks to be a similar design - same Space1999 style cast cabinet - but ported, and with a 200-watt bass amp vs. 250 in the SCM20ASL.

Did I mention that I really, really love my ATCs?

- ds
Old 14th February 2003
  #5
Quote:
Originally posted by sounddevisor
Thrillfactor -

Just wanted to point out that the new ATC SCM20 powered monitors (SCM20ASL) are not ported - and man do they sound great!

The ATC T-16 looks to be a similar design - same Space1999 style cast cabinet - but ported, and with a 200-watt bass amp vs. 250 in the SCM20ASL.

Did I mention that I really, really love my ATCs?

- ds
The SCM20A(with SL) were the powered one's that I liked(and yeah I know they are not ported, unless you wanted a ported pair which they did make on special order).

The ATC 16 double ported speakers were the one's that I didn't.

ATC's were some of my favorite monitors for mixing pop music(it changed when i started using the Dunlavy SM1). The best one is the SCM50. It has a lower bass frequency and the famous ATC midfield(ATC designs the best midfield drivers out there).
Old 14th February 2003
  #6
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Roland's Avatar
I like the SCM20 Actives, but find them a tad forward in the midrange for my taste. I really like the SCM 50's, prefer them to the 100's wich I find a little muddy sounding.

I agree with Thrillfactor about the mid units. Have a couple in boxes upstairs that I planned to incorperate into an active custom box.

Regards


Roland
Old 15th February 2003
  #7
Gear Nut
 

ports ARE out-of phase with the bass driver; being at lower frequencies the designers hope you won't notice.

ported designs also exhibit a sharper bass roll-off, often this is engineered to have a slight hump above the cut-off frequency to compensate (easily achieved by calculating the ideal port length, then shortening it)

closed box designs have a much smoother and natural roll-off.
Old 16th February 2003
  #8
Motown legend
 
Bob Olhsson's Avatar
 

It's an interesting question.

My experience has been that it's a lot easier to find and fix problems in the low-end with closed cabinet designs but it's also easy to wind up with more low-end than you expect even when the speakers are flat down into the 20s. Ported speakers also seem subject to far greater changes in the low-end as you move them around a room.
Old 17th February 2003
  #9
Quote:
Originally posted by Bob Olhsson
It's an interesting question.

Ported speakers also seem subject to far greater changes in the low-end as you move them around a room.
Bob,

That's because they work off the reflections around the speakers, which introduce standing waves around the listening area.

The biggest innovation in speaker design I've seen to combat this, is the "cabinet-less" speakers by Gradient Revolution SR1. The speakers are suspended within a frame with no cabinet(its the weirdest looking thing). But they are effective, probably one of the best integrations between drivers. And as i posted earlier, you can move the subs out of phase from each other to "tone"down excited bass waves.

Its a full range speaker(and light weight because of the lack of the cabinet). Even though there is no cabinet they go down very low.
Old 17th February 2003
  #10
Quote:
Originally posted by thethrillfactor
Bob,
The biggest innovation in speaker design I've seen to combat this, is the "cabinet-less" speakers by Gradient Revolution SR1.

For those who want to read more:

http://www.ampspeaker.com/speakers/revolution.htm

Check this link out.

I've heard these speakers(my partner uses them as a mastering speaker) and they are wonderful.
Old 17th February 2003
  #11
Quote:
Originally posted by 2busdriver
Hmmm, what if said speaker was soffit mounted, asked the curious budding acoustician - I mean I dont know
Well one of the best persons to ask on that subject is John Sayers(he lurks around here sometimes).

I read somewhere him speaking out on this very subject.

If my memory serves me correctly. I think he mentioned its the only way to get a true accurate bass response from a speaker. Again i am sure I am paraphrasing it, but I am sure if we asked him, he would glady chime in on this very subject.
Old 17th February 2003
  #12
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Roland's Avatar
Quote:
Originally posted by crispy
ports ARE out-of phase with the bass driver; being at lower frequencies the designers hope you won't notice.

ported designs also exhibit a sharper bass roll-off, often this is engineered to have a slight hump above the cut-off frequency to compensate (easily achieved by calculating the ideal port length, then shortening it)

closed box designs have a much smoother and natural roll-off.
The "hump" can be obtained on both sealed and ported enclosures, it is dependent on the "Q" of the cabinet chosen by the designer. Classic example of a ported cab that doesn't exhibit the hump is the ATC's. They deliberately engineer their cabs to have a lower "Q" than the normally accepted 0.7. The trade off is in their words that the speakers can sound bass light, but they go lower and roll off more gently.

Regards


Roland
Old 17th February 2003
  #13
Motown legend
 
Bob Olhsson's Avatar
 

Quote:
Originally posted by 2busdriver
Hmmm, what if said speaker was soffit mounted, asked the curious budding acoustician - I mean I dont know
My very best eperiences with ported speakers have been with them soffit mounted. Of course I've hardly played with every ported speaker, mostly just Altecs, JBLs, Tannoys and Meyers. Using speakers in the position the designer intended is probably far more important than any generalization. (I do love sweeping generalizations but I always take them with a large block of salt.)
Old 24th February 2003
  #14
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Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by thethrillfactor
I've posted on this topic in the past.

Here are some of my opinions.

<SNIP>
My favorite powered monitors were also non ported(the older ATC SCM20P and 50), but on the above monitors(with the exception of the Dunlavy which is a D'Appolito design) I always heard from people who listened to them that they wanted more bass(go figure, that is why the new ATC's are all ported or dual ported. Sounds totally different).

<SNIP
Thrillfactor:
I'm not sure what "new" ATC's you saw...maybe the T16?. The entire ATC line is sealed boxes EXCEPT one, the ATC T16, which was created just for folks who want ATC's mid/top but more bass. The T16 is also the lowest cost ATC powered speaker at $3,100 or so a pr. Knowing how ATC feels about it, they would be quite put off that folks think they are all ported speakers!
Brad
Old 24th February 2003
  #15
Re: Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by Brad Lunde
Thrillfactor:
I'm not sure what "new" ATC's you saw...maybe the T16?. The entire ATC line is sealed boxes EXCEPT one, the ATC T16, which was created just for folks who want ATC's mid/top but more bass. The T16 is also the lowest cost ATC powered speaker at $3,100 or so a pr. Knowing how ATC feels about it, they would be quite put off that folks think they are all ported speakers!
Brad
Hey Brad,

I posted that it was the T16(or the ATC "dance monitor").
Old 1st March 2003
  #16
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Yannick's Avatar
 

I recently switched from bass reflex speakers to closed box.
I never want to go back.
I had Harbeth BBC LS5/12A.
Now I have Link K50.
It's Belgian (www.link-audio.be)
They're great and not expensive.
I hooked up a Bryston 3BSST, and a sub because my room is has a lot of bass absortion.

It is true that I hear every little change in the bass register a lot more clearly, I also tend to change less in that region (in the mix), ie I used to compensate for bass overhang, phase problems of the bass reflex/room combination.

Yannick
Old 1st March 2003
  #17
Lives for gear
 

Deadly,

"Most speaker designers will swear that the ports are in phase with the woofer(s) but my experience here says otherwise as I heard the "smearing" .

They can have the port's tuned frequency in phase with the driver, but unfortunately all the other frequencies come out the same port comb-filtered.
The tuned-frequency will be the loudest coming out of the port, but there is still a problem. However, because LF waves are so long, the problem is minimal, and the poted design can (obviously) work quite well.


"Is it true that closed cabinet designs need up to twice the power from an amp to get the same SPLs of a bass-refllex design?"

Yes, in my experience. I have used a few different brands of sealed subs over the years. There is a trade-off between efficiency and top-end response. In the case of an ELF design, especially, the cabinets must be kept fairly small. This adds a lot of damping to the drivers. I currently use the Bag End ELF system as my main monitors. In my 300 sq ft control room, it takes four dual-ten subs, driven by two Bryston 4BST's, to give the kind of thump that R&B guys require. -But it sounds GREAT, and it's a main system that's accurate for mixing. Well worth it.



"Isn't it inherently better to monitor on closed (non-ported designs)? "

Not necessarily:

1: They do sound different. Most people listen on ported speakers, and want to hear that "thump." You won't get that on non-ported designs. You can learn to mix well with a non-ported sub, I have and love them, but visiting producers can be thrown off badly.

2: Non-ported designs can go to VERY low frequencies. the Bag Ends are flat to 8 HZ. You cannot imagine the number of acoustical problems that can crop up when you have that kind of bandwidth at high volume.

3: As you alluded to, it's hard to get a huge amount of chest-thump from them. Some might find this problematic.

for me, the benefits (which are many) FAR outweigh the problems. Of course, I also have very good ported speakers (KRK E8t's) and wouldn't dare mix without both.
Old 5th March 2003
  #18
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Deadly's Avatar
 

QUOTE
1: They do sound different. Most people listen on ported speakers, and want to hear that "thump." You won't get that on non-ported designs. You can learn to mix well with a non-ported sub, I have and love them, but visiting producers can be thrown off badly.

2: Non-ported designs can go to VERY low frequencies. the Bag Ends are flat to 8 HZ. You cannot imagine the number of acoustical problems that can crop up when you have that kind of bandwidth at high volume.

3: As you alluded to, it's hard to get a huge amount of chest-thump from them. Some might find this problematic.

for me, the benefits (which are many) FAR outweigh the problems. Of course, I also have very good ported speakers (KRK E8t's) and wouldn't dare mix without both.

1. I agree, but isn't the trade-off the smearing of the phase as you have a port which is several degrees or in some cases 90° out. Thump is nice but not at the expenses of clear defined attack.

2. Yes, it depends on the level you monitoring at, the percentage of direct sound from the speakers vs. the reflections of the room. I try to keep the levels low to shift the balance in favour of the direct sound and to ensure I can live without a hearing aid in my "twilight" years.

3. If the clients need their chests thumped, a pretty nurse is a better option as it again it saves on wear and taer on the ears, unless she likes to yell while performing this task.

I find the KRKs bass-heavy and can give me an exaggerated feel for the bass frequencies, that can tend to give me a bass-light mix when Mr. Normal plays it over his hi-fi.
I used to do my mixing with the little 2way speakers from Auratone, not the cubes, and when I listened on larger monitors or at a friends the bass was proportionately correct, not too little, and not too much.
I am looking for a set of small monitors with closed cabinets, but there isn't a hell of lot out there right now. Else I am going with my good ol' NS-10s.
Old 5th March 2003
  #19
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dave-G's Avatar
Re: Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by Brad Lunde
Thrillfactor:
I'm not sure what "new" ATC's you saw...maybe the T16?. The entire ATC line is sealed boxes EXCEPT one, the ATC T16, which was created just for folks who want ATC's mid/top but more bass. The T16 is also the lowest cost ATC powered speaker at $3,100 or so a pr. Knowing how ATC feels about it, they would be quite put off that folks think they are all ported speakers!
Brad
Huh? Brad, I thought the 20 was the only sealed one, no? (3rd from the left)



Not that this is a bad thing; in my limited experience with them, the ATCs have been very impressive, but ... well... aren't those ports?

-dave
Old 5th March 2003
  #20
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Roland's Avatar
Whether it is true these days, but ATC used to state that their speakers sometimes sounded a little lean in the bass as they used a lower "Q" than usual which gave them a longer, more gentle, roll off, however the roll off starts at a higher frequency.

Regards

Roland
Old 5th March 2003
  #21
Re: Re: Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by dave-G
Huh? Brad, I thought the 20 was the only sealed one, no? (3rd from the left)



Not that this is a bad thing; in my limited experience with them, the ATCs have been very impressive, but ... well... aren't those ports?

-dave
Hi Dave,

Brad will probably PM you personally about this post.heh

And yes those are ports.

An excellent speaker design is an excellent speaker design ports or no ports.

ATC's are great speakers.

Maybe not for everyone, but they are gret speakers.
Old 5th March 2003
  #22
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dave-G's Avatar
Re: Re: Re: Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by thethrillfactor
Hi Dave,

Brad will probably PM you personally about this post.heh

And yes those are ports.

An excellent speaker design is an excellent speaker design ports or no ports.

ATC's are great speakers.

Maybe not for everyone, but they are gret speakers.

Oh, I agree that they're excellent.

For the record, I wasn't trying to make a critical point of any kind, but Brad's post made me wonder if I was misinformed about the 'portedness' of the line.

-dave
Old 5th March 2003
  #23
Re: Re: Re: Re: Re: Re: Truth in monitoring -Bass reflex vs. closed cabinet designs

Quote:
Originally posted by dave-G
Oh, I agree that they're excellent.

For the record, I wasn't trying to make a critical point of any kind, but Brad's post made me wonder if I was misinformed about the 'portedness' of the line.

-dave
Dave,

Brad post was a test to see who here was paying attention(or knows what they are talking about).

Obviously you were.
Old 7th March 2003
  #24
Here for the gear
 
Deadly's Avatar
 

For those of you who are (un)lucky enough to live in Europe, there is a great article on "getting the bass right" in the March 2003 issue of Resolution Magazine, which is published in the UK.
It deals primarily with the rules of good bass reporduction in stereo and surround and is written by Mr. John Watkinson. One of the many points made is about phase distortion from "ported" designs.
Good reading for those of you who are thinking of getting or replacing monitors in your studio(s)
Old 9th March 2003
  #25
Gear Head
 

Hey Deadly, will fax all of us a copy of the article. heh

Lee
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