Can someone Pls explain this to me...

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Hello all ...
Some users have reported that the Bentley Floorstanders when pushed too hard the drivers will touch the grills
I use a Krell amp on the FS150's and could never get them to touch the grills at even very loud levels , the amp is at least 150w/rms and have sufficient Bass when i listen to them with this amp
Krell is also known to add some bass as well
Recently i connected a much lower wattage Emotiva amp with the same setup and even at moderately low volume i could hear the drivers touching the grills / it was not played into distortion
I know it's not a achievement or something to let the drivers touch the grills but it was just weird
Could it be that everyone that experience this excursion is that the amplifiers are distorting ??
Why is it not happening on a much stronger amplifier ??
Thanks
 

Stereosane

Where Music & Emotions Meet
Joined
Aug 10, 2013
Messages
2,110
Reaction score
236
Location
Garden Route
Maybe the dampning factor is higher on the one amp, although I'm not sure how much dampning factor affects cone excursion vs bringing the cone to start and stop on the beat.
 

Baseline

AVForums Veteran
Joined
Nov 22, 2012
Messages
774
Reaction score
222
Location
Cape Town. South Africa
If my cones were making such massive excursions as to touch the front grills, I would be very concerned and have my amplifier and speakers professionally checked out. Why you would even consider trying to replicate this with your speakers is quite frankly beyond comprehension.
 

Shonver

AVForums Grandmaster
Joined
Dec 18, 2005
Messages
11,784
Reaction score
513
Location
Cape Town, South Africa
I believe the Bentleys use a ported enclosure. The difference between a ported box and a sealed box as regards cone excursion is that the woofer (cone) in a sealed enclosure is fully damped by the sealed volume throughout its operating bandwidth, while the box in the ported enclosure only does this down to the tuning frequency of the port. The port extends the low frequency response of the speaker to below what a sealed enclosure can do. However, the woofer unloads acoustically below the port resonance frequency and acts as if it is operating in free air, without box damping. Energy received by the speaker that is below port tuning frequency will cause the cone to excurse more than with signals at or above port resonance.

All things being equal, it can be deduced from the info given that the Krell has a higher low-frequency cut-off than the Emotiva, so the Emotiva is passing (amplifying) low frequency info that the Krell does not.

Ideally, a speaker should only be fed signals within its designed capability. There is no benefit in sending very low frequency info to the speaker that it may not be able to handle. This applies to all speakers. However, most users do not have such an option available to them. Your Krell is doing you a favour, but not the kind that is often assumed.
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Thanks it is not that i want to Replicate it....
Just thought my stuff is not being played that loud compared to other people saying that they are removing the grills because the woofer is touching the grill
Allways thought jeez how loud do those people listen to their stuff that the woofer is touching the grill
and then you connect a much weaker amp and all of the sudden it happens ??
I Do not play my stuff with any EQ only coming from a network player straight into a power amp , i am not a bass freak ,, only listening 2 ch stereo
Thanks
 

chrisc

AVForums Grandmaster
Joined
Dec 24, 2008
Messages
14,251
Reaction score
1,323
Location
Cape Town
Possibly some DC offset is creating the excessive cone excursion

Check the cone as you turn on the amp.  If the cone moves out and stays in that position, then yes
 

roddy100

AVForums Member
Joined
Nov 21, 2016
Messages
58
Reaction score
26
Location
Stanford
You don?t mention the source. If it?s vinyl the Krell amplifier may have a filter on the phono. Filter what: record warp, and or low frequency rumble. These low frequencies added to low frequency signal may cause excessive cone excursion.
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Thanks but i did mention it's a media player playing Spotify
Denon Dnp 800 Ne
 

Trompie67

AVForums Grandmaster
Joined
Dec 28, 2014
Messages
6,766
Reaction score
1,166
Location
Johannesburg
Baseline said:
If my cones were making such massive excursions as to touch the front grills, I would be very concerned and have my amplifier and speakers professionally checked out. Why you would even consider trying to replicate this with your speakers is quite frankly beyond comprehension.

It was a design error on some of the first series of the Bentley speakers. The original design was for no grills. Just before production a decision was taken to included grills, however the mounting system/method meant that the grills were very close to the front baffle. So when driven at medium to high levels the cone excursion can cause it to touch the grill.

As such no need to panic and have anything checked out, just need to get the newer design grills from the manufacturer which eliminates the problem.
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Hi yes thanks Trompie, i dont think anything is faulty i just noticed it,, i know about the grills that's why some people just keep them off
 

Ingvar Ahlberg

AVForums Super Veteran
Joined
Jan 16, 2014
Messages
1,899
Reaction score
693
Location
The Swedish westcoast
This is clealy an example of serious amplifier/speaker missmatch, the Emotiva amplifier has to high output impedance and to poor power supply to control the 4-6 ohm impedance of the Bentley speakers.

All things being equal, it can be deduced from the info given that the Krell has a higher low-frequency cut-off than the Emotiva, so the Emotiva is passing (amplifying) low frequency info that the Krell does not.

Wrong, the Krell most likely is linear to DC, I cant imagine that You experience lacking low frequency response using the Krell?

This just an example of poor synnergy, the Emotiva amp (if not faulty) is not suitable for driving this Bentley speaker, zero control of the voice coils/cones.

Ingvar
 

Shonver

AVForums Grandmaster
Joined
Dec 18, 2005
Messages
11,784
Reaction score
513
Location
Cape Town, South Africa
Ingvar Ahlberg said:
Wrong, the Krell most likely is linear to DC, I cant imagine that You experience lacking low frequency response using the Krell?

It's easy to check up on this. [member=18307]Anton[/member] can you please give us the model numbers for these amps?
 

Crafter

New member
Joined
Jan 14, 2014
Messages
39
Reaction score
8
Location
Durban
I can make no comments on the amplification side of your query.

However, Vaughan Bentley has made some comments regarding the rattling grills (see link below).
https://www.avforums.co.za/index.php/topic,96681.msg1077453.html#msg1077453

To my understanding and observations, the drivers are not actually touching the grills, but rather the airflow through the port is causing the cloth to vibrate against the grill structure, thereby causing a rattle sound.

I actually just bought a new set of the upgraded grills this week for my FS-150s. The latest iteration are full length grilles (unlike in the above links photo) with a new more open weave material allowing more airflow so as to cause less vibration.

I must say, the new grills are a definite step up and a lot quieter. However, when I tested them by playing bassy tracks at serious window rattling volume (think party or showing of to a mate type volumes), I can still hear some grill rattle. I'm running my set with an 1980's NAD 3400 amp which is conservatively rated at 100w - 8Ohm.

I don't think that the rattle sound will easily be overcome, just put you hand in front of the port when playing low frequencies and feel just how much airflow is being generated.

BTW, can you hear any difference in the low frequencies with the grills off?
 

Orcish75

AVForums Veteran
Joined
Dec 14, 2018
Messages
347
Reaction score
143
Location
Roodepoort, JHB
You have to push the Bentleys very hard to get the drivers to hit the grills. Most of the slapping sound comes from the grill material hitting the baffle by the port. A lot of air moves through the port when pushing the speakers hard, so that material moves a lot. To check, gently put your hand over the material by the port when playing at levels that you hear the noise so that the material can no longer move and the sound should go away. Unfortunately the only real solution is to remove the grills when cranking it up. The Bentleys can take a beating, I've had my FS-150s at silly levels and they've taken it in their stride.

Check if the Krell has some sort of sub-sonic filter, or high pass filter enabled. I can't imagine the Krell would have such a filter hard wired in, I'd be extremely upset if I had a Krell that couldn't go down to single digit frequencies.
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Hi the Emotiva is a Mini X 100 - I know it is far too weak for the Bentley Speakers , Pls don't bite my head off....It was just an experiment to hear how it sounds
I am VERY HAPPY with the Krell KAV 300i running the Bentley's , but did not experience the Vibration from the baffle? as with the Emotiva ...That was strange to me ?
Both Amps are functioning 100% 
There is no filters on the Krell , it is only set to function as a Power Amp , so also tone is bypassed
Thanks
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
And sorry Forgot ..I am not lacking low freq resp from the krell , just not the Baffle sound ....I know it is not something or a benchmark to go by , but it was just strange to me
 

Shonver

AVForums Grandmaster
Joined
Dec 18, 2005
Messages
11,784
Reaction score
513
Location
Cape Town, South Africa
Emotiva mini-X a-100 vs Krell KAV-300i. You couldn't ask for a more dissimilar pair to compare. The Emotiva is essentially a midi amp, while the Krell comes with a pedigree. However, I don't believe that damping factor is the issue here: there is not much an amp can do about how a speaker fundamentally works. If both amps are delivering the same signal to the speaker, the speaker will respond with the same excursion.

Here is an article about how ported enclosures work that includes a helpful animation:

https://hometheaterhifi.com/editorial/a-big-dig-into-bass-reflex/
 

BiZKiT

AVForums Grandmaster
Joined
Feb 18, 2011
Messages
3,338
Reaction score
306
I think the Krell has much more control then the Emotiva. Remember there are special order grill we can do with much better material if need be.
 

Cross_over

AVForums Veteran
Joined
Jun 4, 2017
Messages
740
Reaction score
200
Location
Hermanus, WC
Anton said:
There is no filters on the Krell , it is only set to function as a Power Amp , so also tone is bypassed
Thanks

I assume you meant "volume is also bypassed". I have never seen a KAV300i (or any other Krell amp/preamp) with tone controls.
 

Anton

AVForums Member
Joined
Mar 1, 2016
Messages
81
Reaction score
15
Location
Pretoria
Yes, i meant the volume is bypassed and that i do not use any tone controls, have never believed in adjustimg bass or treble
Some people would just assume you turned the bass up too much
 
Top