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A very basic question on bass reproduction from Floor Standers

Audiolab 6000CDT Dedicated CD Transport

john_k_antony

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I have Kef iQ7 FS. I always felt that it didn't have any bass. I was playing it with Denon 2310 AVR and felt that was the reason for low bass from the speakers. I always had to use a sub woofer to get any bass from my system. 2 days ago, I got an Acoustic Portrait NJ1 dual mono power amp. Connecting to the power amp did improve some bass response but it was nothing close to the bass I heard from Acoustic Portrait Bookshelves connected to the same NJ1s.

But today I notice something strange. I was sitting pretty close to the speaker (around 3 feets from the speaker) and my ear was at the woofer level. Voila the speakers are producing pretty good bass :O. Then I moved back to my listening position that is around 15 feets from the speakers and ear level is at midrange/tweeter level. Now the bass has significantly reduced. When I move closer to the speakers and lower my ears to the woofer level, the bass is back with a bang.

My questions,

1. Is the woofer not able to push the air so far to 15ft due to lack of amplifier power or the bass driver is not capable of pushing the air that far to give the bass at 15ft away from speakers?

2. The volume levels are pretty high and the mids and highs are very fine and detailed, so I am not sure the amplification is the issue here.

3. The AP power amp is rated at 75W/ch @8ohms. I think this is good enough to drive the 3-Way, 90db, 15W-150W Kef iQ7 to produce good bass.

-John.
 
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odyssey

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it is possible that there are null points at your listening position. What is the room size? Do you feel low bass output even at the backwall (furthest point from the speaker)?
 

prepress

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Also check your speaker's polarity, it may be because of positive-negative mismatch. Try to change the polarity of ONE SPEAKER.
 

Hari Iyer

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Null points at room could be one of the reason as mentioned by odyssey. The side and the back walls helps to increase bass response by around 3 dB to 6dB overall if place properly. Also in the speaker if the mids and highs are not balanced with the lows, due to baffle step the mids / highs will tend to mask the low frequency. It may be possible that your speaker has good bass but it also has more mids and highs which are not in level with your lows. Using a DSP or EQ will help to bring the level same for all freq. Not sure if this is the case with you. Only a proper analysis will help conclude.
 

kuruvilajacob

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I think your speaker positioning is not correct. Far field speaker positioning I feel is in my opinion more difficult to get the bass output if you are not positioned correctly. Plus you will need to consider bass traps and ways to control standing waves. As i have not seen your set-up, i am just guessing that these could be factors affecting lower frequncies
 

john_k_antony

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Hi,

Thanks for all the details. The speaker polarity is fine. I guess it could be the room and null points that is causing the issue :(. The speakers are kept in the living room without any acoustic treatments. I think there are null points as I could feel the bass response varying when I start walking from the rear wall towards the speaker, which is around 28 ft away from the speakers.

I also felt lots of bass when I stood behind the speakers.

I think the room is doing the major spoil sport here. I have a carpet on the floor and some couches in the living room. And I don't think I can acoustically treat the living room without messing up the aesthetics :). I will be acoustically treating my dedicated listening room. But I am wondering how can I fix this in my living room without messing up the aesthetics of my living room :).

Right now I am in an apartment with "L" shaped living cum dining room. I will be soon moving to my new house where the Living room is rectangular and the dimension is 22.5'x15.5'. Speakers are going to placed on 15.5' wall and listening position would be roughly 20 ft away from the speakers.

I would really appreciate if there are some simple ways to acoustically treat a living room.

Thanks,
John.
 

Nikhil

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John, I just googled the iQ7 and found a few similar posts like yours mentioning lack of bass. I suspect there's a possible dip in the impedance in the low end. Does the bass turn muddy? How long is you run of speaker cables?

Can't say for sure but try speaker cables with a lesser gage (thicker conductor) and see if this helps. Doing this reduces the load as seen by the amp and should give you better bass response.
 

john_k_antony

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Null points at room could be one of the reason as mentioned by odyssey. The side and the back walls helps to increase bass response by around 3 dB to 6dB overall if place properly. Also in the speaker if the mids and highs are not balanced with the lows, due to baffle step the mids / highs will tend to mask the low frequency. It may be possible that your speaker has good bass but it also has more mids and highs which are not in level with your lows. Using a DSP or EQ will help to bring the level same for all freq. Not sure if this is the case with you. Only a proper analysis will help conclude.
Hari,

I think you are right on the fact that exaggerated highs and mids masking the bass from the iQ7. These speakers are bright speakers. They tend to produce brighter Highs. The reason why I am saying this is that, I am now playing around with the new CNC MM phono stage I just built. I was trying different loading resistance and with low load resistance configuration (18K Ohm), the highs are pretty rolled off and I could get a balanced high, mid and relatively better bass. When I change the settings to higher load resistance(62K Ohm), the highs and mids are more detailed and prominent and the bass is reduced.

Well I am not sure if its the CNC phono doing the trick or the speaker is responding to a low HF and producing a balanced sound stage.

I am going to try a tube Pre and hook it to the chain to roll of that extra Highs and expect the speakers to produce a balanced High-Mid-Low output. Right now my Denon 2310 AVR is used as the Pre.

Thanks,
John.
 

john_k_antony

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John, I just googled the iQ7 and found a few similar posts like yours mentioning lack of bass. I suspect there's a possible dip in the impedance in the low end. Does the bass turn muddy? How long is you run of speaker cables?

Can't say for sure but try speaker cables with a lesser gage (thicker conductor) and see if this helps. Doing this reduces the load as seen by the amp and should give you better bass response.
Hi Nikhil,

Thanks for the reply. I am right now using a very cheap speaker cable that I got free when I got the speakers. I was not paying attention to change the cables :). Actually I am changing one thing at a time

1. I got a dedicated power amp and that did improve the overall sound quality and bass response compared to Denon 2310

2. Change my player from the basic Sony DVD player to Oppo 93. I thinks source may not be the real culprit as I get similar bass response from my TT as well. Well my TT is not high quality either. But I am not doubting too much on my sources here.

3. Get a tube Pre amp and remove Denon completely from the chain. I will use Denon only for HT job. I assume the tube Pre will mellow down the Highs and improve the overall sound.

4. Change the speaker cables.

But I started this thread when I suddenly heard good bass from KEFs when I sat near to it and ear level at the woofer level with my current setup.

So as others commented, the room may be playing the spoil sport here :(.

-John.
 

Nikhil

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Hi Nikhil,

Thanks for the reply. I am right now using a very cheap speaker cable that I got free when I got the speakers. I was not paying attention to change the cables :). ...

4. Change the speaker cables.

-John.
You will be surprised ... Pay attention to your cables.
 
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olly42

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John see if you can borrow cables for a short while and see if it makes the difference and if it does (Which Im sure it will) you can invest in good cables
 

john_k_antony

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I tried some position adjustments with toe-in and stuff like that suggested by a FM before. But the options for me to make the position changes are pretty limited as its in a living room.

I will try the cable changes tomorrow itself. I will try to borrow cables from Mr Murthy who has a shop in Commercial street. Heard rave reviews about his cables. So would try it. I am also planning to take my current cables with me to Mr Murthy and have him take a look at them.

-John.
 

kaps

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Dear Antony, Imho bass is non directional. You may have revrse polarity and cables are mostly never so effective untill and unless cable resistance is too high (cables arent equalizers or amps) I suggest get a multimeter. Its always handy. What is the rated power of the amp. Is the impedance of spkrs and amp matching. And bass is best reproduced when subs are at a min dist frm the floor.
 

Tanoj

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Hi John

How old are the speakers, approx. how many hrs they ran till date ?

are they front ported or rare ported or no port at all ( bass port )

bypass the pre amp and connect source directly to the power amp, reduce volume on cdp and check

distance between two speakers, distance between side walls to the speakers, rear wall to the speakers , everything matters

last but not the least , it can be source too

I got Acoustic portrait speakers and they rock, bass is great

best of luck,
 

Hari Iyer

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John, I just googled the iQ7 and found a few similar posts like yours mentioning lack of bass. I suspect there's a possible dip in the impedance in the low end. Does the bass turn muddy? How long is you run of speaker cables?

Can't say for sure but try speaker cables with a lesser gage (thicker conductor) and see if this helps. Doing this reduces the load as seen by the amp and should give you better bass response.
The woofer impedance increase at the resonating freq of the woofer and does not dip. In a vented enclosure there are 2 peaks for the impedance one for the woofer and other for the enclosure. The trick is to have both the impedance peaks as same for perfect tuning of the enclosure and the woofer. For a typical woofer the impedance peak can be anywhere between 35Hz to 60Hz and for the enclosure from 50Hz to 100Hz. May be this could be one of the reason for low bass at lower frequencies.
 

Hari Iyer

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Hari,

I think you are right on the fact that exaggerated highs and mids masking the bass from the iQ7. These speakers are bright speakers. They tend to produce brighter Highs. The reason why I am saying this is that, I am now playing around with the new CNC MM phono stage I just built. I was trying different loading resistance and with low load resistance configuration (18K Ohm), the highs are pretty rolled off and I could get a balanced high, mid and relatively better bass. When I change the settings to higher load resistance(62K Ohm), the highs and mids are more detailed and prominent and the bass is reduced.

Well I am not sure if its the CNC phono doing the trick or the speaker is responding to a low HF and producing a balanced sound stage.

I am going to try a tube Pre and hook it to the chain to roll of that extra Highs and expect the speakers to produce a balanced High-Mid-Low output. Right now my Denon 2310 AVR is used as the Pre.

Thanks,
John.
Try using a Baffle step compensation circuit in series with your speaker and check out if the lows, mids and highs get balanced. Will PM you details later.
 

kaps

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Open baffle design gets rid of all these fine tuning issues man. However you need more power to the true uncoloured music.
 

captrajesh

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I am right now using a very cheap speaker cable that I got free when I got the speakers. I was not paying attention to change the cables :).
You will be surprised ... Pay attention to your cables.
John see if you can borrow cables for a short while and see if it makes the difference and if it does (Which Im sure it will) you can invest in good cables
I will try the cable changes tomorrow itself.
I'm glad you are open to suggestions. Even a 14 gauge OFC cable from a reputed brand will give you substantial results. Thereafter, you can buy stuff that suits your pocket and overall setup.

Also, placement makes a big difference. It would help if you could post a pic of the room where the setup is kept.
 

john_k_antony

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Hi,

Thank you all for giving all the valuable details and suggestions.

I will take a picture tonite and post the placement and rest of my furniture and room layout.

The speakers are in use for last 4 years. So I think it has enough break in. But I doubt that the woofers had any real workout with my Denon AVR :). I think the new AP amps are giving it some decent workout and let me see if bass opens up after a while :).

The speakers are front ported. Here are the specs and details - http://www.kef.com/html/gb/explore/about_kef/museum/2000s/iQ1_iQ2c_iQ3_iQ5_iQ5SE_iQ/index.html

I was running the speakers for the last 4 years with Denon 2310 rated at 100W/ch @8ohms.

The new AP power amps are rated at 75w/ch @8ohms.

I think the power is adequate for the speakers as they have 90db sensitivity.

I am taking my existing speaker cables to Mr Murthy today so that he can check out the characteristics of the current cables. I think he can rent me a pair for cables that I can try out in my setup.

Thanks,
John.
 
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