340SE with ports blocked?

[GirgleMirt]

Alright, yet another twisted idea by the Mirt man :p

So would blocking the port the the 340SE be a good or a bad idea?

I'm asking because, when integrated with a subwoofer, I'm guessing that there would be less frequency overlap between both and that could result with a better integration.

I know the recommended frequency of the subwoofer is 80hz, but after calibrating everything, seems that the best setting for me is lower than that, maybe 60hz? 65? Even if my sub amp has a high pass filter at 80hz, and a 24dB/oct sub rolloff, it seems to be the optimal crossover point... :confused:

Maybe its room interactions factors in, but if I set it higher, seems I get some bumps in the 60-100 hz region... (sub still plays some 80+ frequencies and mains 80- so ends up in bump in FR from overlap)

Anyhow, by blocking the 340SE ports, my guess is that their sensitivity would go down a little, and it would significantly attenuate the low end response of the 340SE. (probably kill frequencies below like... 70hz? 60hz?) If that happened, I'm guessing I should be able to put the crossover point of the sub higher, would get less bass from the mains, and so it should sound better?

I haven't tried it with the Ascends and sub, anyone has any thoughts or experience in the matter?

Some also praise acoustical suspension (sealed) designs, so I'm wondering if by blocking the port you could somehow get a little acoustical suspension and therefore improve the 80+hz freqs...

[Jorge_Burrito]

I would think this to be a real bad idea. It is not just the frequency response of your absolute lowest frequencies that will be killed but pretty much all the base response....I imagine you would be completely killing your linearity on your frequency response. I also believe (although not positive) that the drivers themselves are designed with a port in mind and that there is somewhat different driver design for a sealed port driver. You may end up doing damage to your speakers.

If you like the lower crossover, then by all means use the lower crossover. Theoretically you should not be getting frequency bumps as while both the sub and speakers are playing in these sections they are rolled off so the total volume together should equal the individual volume of one of your components. Of course room interactions and various other problems will not make the theoretical actual. Buying your speakers is only part of the equation, the rest is trying to figure out where and how they sound best in your room. Have you tried placing your sub in a different location? You might also want to try some bass traps in the corners of your rooms.

[audibleconnoisseur]

The ports are there for a reason! Since they need clearance to breath, I would say no. Since the crossovers inside are taking into consideration the port, I would say no. Since the bass response is also reliant on the port, I would say no (although you did address this in your post). Since the port may also be a conduit for the spot on midrange, I would say that you would lose depth there as well with a blocked port.

I would say it is not a good idea. Now, I am no Dave or speaker expert, but I did stay at a Holiday Inn Express last night :p ~

[GirgleMirt]

Sure the port is there for a reason. Its for low end response! :p

Take a look here for example: http://www.stereophile.com/floorloudspeakers/378/index5.html

You have measurements of a speaker, where the port/woofer/tweeter have been measured individually. As you can see from the port, its mainly at 50hz (its port tuning) and has very little effect above 80hz. If in that case you'd block the port, you'd get the FR of the woofer and tweeter without the port...

Bu I mentioned efficiency, I wonder if it would go down by a lot...and that might have some effect of the balance of the tweeter/woofer.... "I imagine you would be completely killing your linearity on your frequency response." I don't think it would... maybe concerning the low end response, but since its done via sub anyhow, it wouldn't be an issue.

"clearance to breath"
"crossovers inside are taking into consideration the port"
"be a conduit for the spot on midrange"

I don't think either of those 3 are correct. But actually, "clearance to breathe" would be akin to internal cabinet volume. Its possible that the internal volume would affect the low end response (FR slope in the low end; extension). But since again, the low end is taken care by the sub, it should be a non-issue.

The crossover doesn't take into consideration the port. Crossover is simply for woofer/tweeter integration, it does nothing for the bottom end. Conduit for midrange, again negligible, the port tuning is very low (48hz), so there's no significant midrange coming from there.


Also it doesn't really turn the ported design into sealed... Somewhat of a 'damped' design... My port plug method of choice in the past was the sock method. (roll up a sock, and place into port) Never seemed to have really good results with it though :p (though I wasn't using a sub at thte time!!!)

[audibleconnoisseur]

As I said, I am no speaker expert. I guess I must not have slept as well at the Holiday Inn Express as I thought I did ;)

Keep the ports open... Dave would have closed them if he felt they should have been. The HTM200's are sealed, ask him why they are and not the 340SE's!!!

[GirgleMirt]

As I said the ports are there for the low end response!!! :eek:

Read here for example: http://www.ishtek.com/spkr_basics.htm. Obviously, for stand alone speakers, low end response/extension is desired and so a ported design makes a better choice than sealed design.

In a setup with a sub, the low end response of the main stops being important. And actually, I'd even say that the LACK of bottom end would be an advantage since there's going to be less overlap in the crossover frequencies of mains & sub, so it should make for a smoother transition and better performance.

[bikeman]

Dave F. usually post after 9 p.m. PCT, so I'd expect we'll be hearing something on this. The port is an intregal part of the system. It is not there just for low end response. I'll wait till morning and if we don't hear from the man himself, I'll try to dig something up.
I should have the day off tomorrow. We're expecting two to three feet of new snow by this time tomorrow.

David

[davef]

Dave F. usually post after 9 p.m. PCT, so I'd expect we'll be hearing something on this. The port is an intregal part of the system. It is not there just for low end response.

Almost right on time :D

Kids are asleep (well, except for little Nicole -- who NEVER sleeps :o )

The port is indeed an integral part of the overall design of the speaker. Blocking the port changes quite a few performance characteristics of the loudspeaker and I generally do not recommend it.

First off -- and perhaps of most importance, in a ported speaker, as you approach the port tune, the woofer itself moves less as frequency decreases (until you reach the port tune). For example, in a ported speaker where the port tune is 50Hz -- at 50Hz and above, the woofer will exhibit less movement when compared to a sealed enclosure (everything else being equal). At 50Hz, the woofer exhibits the least amount of movement. Below 50Hz, the woofer will exhibit more movement. Less movement = lower distortion, higher power handling and less intermodulation distortion which can and will affect the midrange performance of the woofer.

Additionally, the design parameters for a woofer that will be used in a vented (ported) enclosure compared to a sealed enclosure are very different. A woofer designed for a vented enclosure will not perform optimally in a sealed enclosure and vice versa.
Plugging the port in a "properly" designed loudspeaker can (and in most cases, will) result in the following:

* Considerably less output near the port tune frequency of the enclosure

* Higher distortion (both harmonic and intermodulated) across several octaves of the woofer's frequency range

* A considerable "bump" in the response (could also be a dip) usually at the point where the woofer just begins to roll-off. That speaker that was once ruler flat no longer is.

What is most critical to understand is that a properly designed vented enclosure will use components that have been specifically designed for this type of enclosure. A vented enclosure presents an entirely different compliance to the woofer when compared to a sealed enclosure, thus resulting in VERY different design parameters.

For a better understanding of a Helmoltz Resonator: http://en.wikipedia.org/wiki/Helmholtz_resonance


Can you plug the port? Sure, absolutely... But you WILL sacrifice more than just bass..

Hope this helps!

[bikeman]

I should have the day off tomorrow. We're expecting two to three feet of new snow by this time tomorrow.
Well, I just got done shoveling the first foot with another foot due by 3 p.m. The University decided that's just too little snow to shut things down so off to work I go. :(

David

[audibleconnoisseur]

Sweet, I am going to stay at a Holiday Inn Express more often (or at least when I really need to know something) :p

[GirgleMirt]

Hehe!

Thx Dave :) I see that its a little different than for subs. Most subs drivers seem to work equally well in sealed/ported designs, looks like its a different matter for midranges.

I might try it to see if I can tell the difference (with sub), but I don't think I'll leave them ported, thanks for the info! :D

[audibleconnoisseur]

Dave just said it was a bad idea... are you saying you aren't going to leave them ported still? Or are you saying that about your sub?

[GirgleMirt]

I meant that subwoofer drivers seem to be equally fine in a sealed enclosure and ported enclosure, which seems to be different for midrange drivers. My sub is already a sealed design so nothing to plug.

I'm curious to see what the effects will be if you plug the 340SE ports, so I will probably try it to see if I can hear the differences, and if I can, see what differences are exactly. But since it all seems to be negative effects, I'm not going to leave them plugged.

For subs, it might also vary depending on the woofer, but you could plug the port of a ported sub and would end up with a sealed sub equivalent... As such, you'd lose some efficiency, some low end response, but you might get some improvement in transients. The problem is that the internal volume of the cabinet plays a role in the sub's FR response, so the performance would depend on the ported sub's internal volume... I believe HSU has design with pluggable ports.

[curtis]

I meant that subwoofer drivers seem to be equally fine in a sealed enclosure and ported enclosure....
That isn't entirely true. While some sub drivers can be used in sealed or ported enclosures, the internal volume of those enclosures are VERY different, as is the amp power. It isn't just the difference of vented or not vented...there are other important factors as well.
edit: I see you sort of mention that.


I believe HSU has design with pluggable ports.
Yes...but not sealed. Some people have run a Hsu sub sealed, but it is not a documented configuration.

[GirgleMirt]

That isn't entirely true. While some sub drivers can be used in sealed or ported enclosures, the internal volume of those enclosures are VERY different, as is the amp power. It isn't just the difference of vented or not vented...there are other important factors as well.

yeah I somewhat covered that in my last paragraph. I meant the same woofers can be used in sealed/ported enclosures, there doesn't seem to be models for sealed designs only and another model for vented designs. Sounds like for midranges they are much less interchangeable.

But of course, like I said, the internal volume is important (determines the system qtc), so qtc will vary depending on the internal cabinet volume, so if you can't control the internal volume, you end up with the qtc of the box and thats it... Vented subs are usually larger than sealed subs, so at least you should still get decent power handling. But its really not optimal to turn a ported sub into a 'sealed' sub...