Sealed versus ported boxes in a 2-way speaker?

[tuga]

I now own Hedd actives and you can choose ported or sealed (there are bungs and DSP settings to accommodate both). I’ve tried both. I prefer sealed.

The PSB Imagine T2s I owned previously came with rubber bungs for the 3 ports (like the PSB whose FR plot I posted earlier). I also preferred the sound with the ports closed but it sounded constrained at higher volumes.

I ended up closing just two of the ports becase this produced the flatest bass response.

 

[MartinC]

The PSB Imagine T2s I owned previously came with rubber bungs for the 3 ports (like the PSB whose FR plot I posted earlier). I also preferred the sound with the ports closed but it sounded constrained at higher volumes.

I ended up closing just two of the ports becase this produced the flatest bass response.

For info. the Hedd's are 'smarter' than simply plugging the ports - there are DSP adjustments specific to each configuration too. 

 

[Lawrence001]

I assume it a speaker is optimised for a reflex cabinet then sticking bungs in the ports is a suboptimal solution for bass issues ie. something would probably be different if it was designed as an infinite baffle?

 

[tuga]

I assume it a speaker is optimised for a reflex cabinet then sticking bungs in the ports is a suboptimal solution for bass issues ie. something would probably be different if it was designed as an infinite baffle?
 

I would say so too.

 

[tuga]

Kef's approach is interesting though as it allows the user to adjust the bass reflex system tuning to the room (and, if you're into that sort of thing, personal taste):

.

Note: this info is not original, it's 100% recycled from the internet. :hash:

 

[Fatmarley]

Kef's approach is interesting though as it allows the user to adjust the bass reflex system tuning to the room (and, if you're into that sort of thing, personal taste):



.

Note: this info is not original, it's 100% recycled from the internet. :hash:

Years ago, someone on here had bass problems with their rear ported speakers, so they fixed a 90 degree bend to the port and extended it down the back of the speakers with plumbing waste pipe. This lowered the port tuning frequency and fixed the bass boom.

When you have two ports plugging one does the same thing (lowers port tuning frequency), but there's more risk of port chuff with one plugged. 

 

[Motortown review]

Ports are the devils work and anyone that praises at the alter of are devil worshiper’s.

 

[zeta4]

It's all a compromise, I agree. But some topologies are more compromised.

With a closed box the amplifier is controlling the woofer, with bass reflex the box "farts" at a give tuning frequency. Ultimately it depends on implementation and also listener expectation/preference.

I think thats true. Ive just come across an interesting post ( in 2010) from Lynn Olson on another forum. I dont know if Im allowed to show it but he begins by saying " Some loudspeakers are more sensitive to variations in source impedance (damping factor) than others. Any speaker using passive 4th order crossover filters, or the acoustic version, which is a vented box, is going to be more sensitive to source impedance than a speaker using low Q alignments (closed box) "

He goes on to explain that its because a 4th order filter needs the damping the amplifier must provide. This could help explain why some amp/reflex speaker combinations dont seem to work well together.

Providing some acoustic resistance (drinking straws) in the port like for a QB3 will provide this damping. I seem to remember this technique being used in the past but not recently.

 

[Fergus]

That is what matter most. :^

(and now you're free to worry about the important things, such network switches and USB cables )

Or else... ‘if these speakers, that I’m 100% happy with, sound so good then what would these more expensive ones be like’

 

[Lawrence001]

I think thats true. Ive just come across an interesting post ( in 2010) from Lynn Olson on another forum. I dont know if Im allowed to show it but he begins by saying " Some loudspeakers are more sensitive to variations in source impedance (damping factor) than others. Any speaker using passive 4th order crossover filters, or the acoustic version, which is a vented box, is going to be more sensitive to source impedance than a speaker using low Q alignments (closed box) "
He goes on to explain that its because a 4th order filter needs the damping the amplifier must provide. This could help explain why some amp/reflex speaker combinations dont seem to work well together.
Providing some acoustic resistance (drinking straws) in the port like for a QB3 will provide this damping. I seem to remember this technique being used in the past but not recently.

This is interesting because the usual measure of damping factor is the speaker (input) impedance to the amplifier output impedance. You can get nominal 8 ohm reflex and sealed box speakers which damping factor would imply should be driven as well in both cases, but the above implies that the reflex would be harder to drive

This issue could be explained if the impedance of the ported speaker fell significantly at the port frequency, which I've seen in impedance plots I'm sure. So maybe this is partly what explains the issue with ported speakers and bass boom. It would also explain why my Yamaha studio amp (nominal damping factor 200 or something like that) sounded very tight, even lean, in the bass compared to most others I've tried.

 

[Lawrence001]

This explains it quite well, but it misses out one factor that I think it's important, and that it the ability of an amp with a high damping factor to reduce room resonance.

I have had room nodes excited by speaker/amp combos that then disappear when I play the same music at the same volume with an amp with a higher damping factor. I initially thought this was odd, as once the bass note is "in the room" then I thought that was the cause of the resonance, but it couldn't explain why different amps could control it better.

It's my theory that the standing wave gets back to the speaker and excites it even more. If an amp can't control this then it makes the boom worse. But if it has tight control of the induced back current then it can control it and reduce the resonance.

Not sure if anyone else thinks this can happen?

 

[Nativebon]

Who cares what the measurements say. I was on a journey for just over a year looking for the right speakers for me in my room to my ears. 

The best performance speakers were ported and sealed. Totem tribe Towers and KLH models5s.

Totems were a bit rolled off at the top end. Bass was so satisfying and goes very deep, on the other hand the KLH models 5s to me does every thing better than the Totems except dept of bass.

The KLH model 5s betters the bass of the ATC SCM 40s in every department, IMO of course. Compromises always made, implementation matters most.

Now I'm a happy owner of the Model 5s

 

[Andrew_C]

No, standing waves are just the result of the rooms dimensions,   

 

[Andrew_C]

You can use any speaker any reaction with the room ( standing waves) can be fixed with EQ see Flak Monkeys measurements, which of course show you the frequency of the peaks.

 

[Nativebon]

Something I'll like to know for sure is if people can listen to speakers and can tell the speakers will measure well and generally behave well in most rooms. Why would 2 way speakers matter most.

 

[tuga]

Something I'll like to know for sure is if people can listen to speakers and can tell the speakers will measure well and generally behave well in most rooms. Why would 2 way speakers matter most.

In the USB Cables thread I posted the link to a paper titled "Differences in Performance and Preference of Trained versus Untrained Listeners in Loudspeaker Tests".

It shows that trained listeners can tell which speakers measure well.

 

[DomT]

You can use any speaker any reaction with the room ( standing waves) can be fixed with EQ see Flak Monkeys measurements, which of course show you the frequency of the peaks.

Not entirely 

 

[DomT]

In the USB Cables thread I posted the link to a paper titled "Differences in Performance and Preference of Trained versus Untrained Listeners in Loudspeaker Tests".

It shows that trained listeners can tell which speakers measure well.

It’s like training people to identify added salt in meals and then asking them which meal has added salt; it’s obvious that a well trained person will spot what they were trained for. But we’re these people asked to identify which speakers they preferred? People buy based on their subjective tastes including people who subjectively prefer well measuring speakers. 

 

[Andrew_C]

Not entirely 

Yes entirely

 

[MartinC]

Yes entirely

What precisely are you suggesting? 

(I'm minded to agree with @DomT but let's see...)