Bass boom after swapping from solid-state to tube power amp

by BrAvO Tue Jun 23, 2009 11:41 am

After switching to the tube amp from solid state, my speaker is producing much stronger bass now & it's giving booming effect. It's only a 30w KT88 but the bass is much deeper than my old Primare A30.1 with 100w of output. Driver is moving in & out a lot more now with the amp. It's sick to hear this kind of strong bass & booming sound.

Can all the Sifu help out to solve the problem?

Can diffuser trap some bass away & the best placement?

Thank you.

by 123_rocketman Tue Jun 23, 2009 11:58 am

Hi Bravo,

I am currently facing the same problem, although I didnt change my amp and still in the midst of reducing the boomy bass problem.

I have tried placing my speakers further from the front wall and have wooden planks placed at first reflection point and DIY diffusers placed at the corners and centre of the front wall.

The sonic presentation changed and boomy bass reduced slightly.

So, just like you, I appreciate all the sifus out there who can point us to the right direction.

Sorry bro to 'tumpang' your thread.

Regards.

by JayJay Tue Jun 23, 2009 2:18 pm

Apart from the wall damping and diffuser, there are other possible solutions:

1. do not remove the speaker's front cover, it acts as a filter to the boomy bass.
2. if the speakers have firing-port, cover it with sponge to reduce/restrict the driver movement.
3. do not use hollow speaker's stand, it will add to boomy/echo sound. (fill it with sand/ball-bearings or atabites).
4. to reduce vibrations, secure the bookshelf speakers to the speakers stand with blue-tag.
5. use spikes on floor stand speaker and the spikes sit on a wooden plank.
6. place some cone noise dampers on top of the speakers.
7. place hard/heavy objects on top of the speakers to reduce speaker's vibrations.
8. place a carpet in front of the system to absorb the bass and as bass damper.

Happy Listening
Cheers.
Smile

by pakleng Tue Jun 23, 2009 2:37 pm

get a few boxes, filled with scrambles old newspaper

place these boxes on the floor eg behind the speakers, side etc.

trial & error till u get the right bass

sure can work, but looks very ugly

by **Hi-Fi 4 Sale** Tue Jun 23, 2009 3:54 pm

BrAvO wrote:After switching to the tube amp from solid state, my speaker is producing much stronger bass now & it's giving booming effect. It's only a 30w KT88 but the bass is much deeper than my old Primare A30.1 with 100w of output. Driver is moving in & out a lot more now with the amp. It's sick to hear this kind of strong bass & booming sound.

Can all the Sifu help out to solve the problem?

Can diffuser trap some bass away & the best placement?

Thank you.

The problem you are facing is not primarily a room acoustics issue. Rearranging the speaker layout or doing room tuning will not totally ameliorate the bass boom.

Instead, if what you describe is correct, the root cause is most probably an amp-speaker matching issue. Most likely, the high output impedance of your tube amp is interacting with the impedance of the speakers over the entire frequency spectrum.

The link from Stereophile may help explain this phenomenon: http://www.stereophile.com/reference/810/

BTW, what speakers are you using?

by BrAvO Tue Jun 23, 2009 4:06 pm

Thank you Sir,

My speaker is Audio Physic Yara Evolution Floorstander.

by BrAvO Tue Jun 23, 2009 4:20 pm

Hi-Fi 4 Sale wrote:
BrAvO wrote:After switching to the tube amp from solid state, my speaker is producing much stronger bass now & it's giving booming effect. It's only a 30w KT88 but the bass is much deeper than my old Primare A30.1 with 100w of output. Driver is moving in & out a lot more now with the amp. It's sick to hear this kind of strong bass & booming sound.

Can all the Sifu help out to solve the problem?

Can diffuser trap some bass away & the best placement?

Thank you.

The problem you are facing is not primarily a room acoustics issue. Rearranging the speaker layout or doing room tuning will not totally ameliorate the bass boom.

Instead, if what you describe is correct, the root cause is most probably an amp-speaker matching issue. Most likely, the high output impedance of your tube amp is interacting with the impedance of the speakers over the entire frequency spectrum.

The link from Stereophile may help explain this phenomenon: http://www.stereophile.com/reference/810/

BTW, what speakers are you using?

There are 4 ohm & 8 ohm speakers terminal from the amp, will by using 8 ohm output reduced the booming, my speaker is rated at 4 ohm.

by **Hi-Fi 4 Sale** Tue Jun 23, 2009 4:36 pm

You can try the 8 ohm taps. Results may vary.

by JayJay Tue Jun 23, 2009 5:46 pm

Amplifier that uses KT88 tubes; produce high bass and low treble output.
This is the characteristic of KT88 (fat body) and unlike EL34 tubes, which is slim; it has high treble and low bass.
So it’s the tubes that produce the bass sound.

Happy Listening.
Cheers.
Smile

by azri Tue Jun 23, 2009 6:37 pm

nice info jayjay, but can we simply swap kt88 with el34?

by cmboy Tue Jun 23, 2009 8:37 pm

The general practice is one does NOT swap power tubes for another type unless the manufacturer documents so. Selected power tubes are selected for the amp, where circuit, voltages and current are optimized based within tube operational specifications for a determined amplifier power or gain stage. DIfferent types of tube have different operating perimeters and their output transformer would match the tube specs. To cut it short, one does not swap an EL34 for KT88 or vice versa. However, there are known replacement alternatives for most tubes. Only problem is the availability. For example, EL34 can be swapped for near alternatives such as 6CA7, KT77. Tube circuits are just different from solid state circuits. One have to understand tube circuit electronics, tube data to have a clearer idea of tube swaps. You have to know what you're doing and power tube rolling isn't the last word to get the best sound. There's other issues that also improve or degrade the sound.

by mugenfoo Tue Jun 23, 2009 9:21 pm

is the bass boom over all the entire bass range, or just as certain particular frequencies?

If it booms at the entire range, congrats, you now have a more powerful amp that is capable of delivering a fuller spectrum of sound than your previous amp. The next step would be to re-position the speakers and/or experimenting with room sound treatment stuff.

if the bass booms at just some particular freqs just by swapping the amp, the first thing i would suspect is that the boomier sounding amp has higher output impedances, therefore the damping factor is now lower (which is a bad thing) and it cannot handle the speakers. The amp is unable to properly control and handle the woofer cones at that particular frequency hence the cone over-vibrates and hence the boomy sound. This amp is lousy, better swap back to the old one. Razz

Hope your case is the former and not the latter.
cheers.

by dixchen Tue Jun 23, 2009 9:49 pm

Which tube amp is this? The KT88 type tube typically emphasizes a lot of low end frequencies. I personally don't like it at all especially Chinese Shuguang KT88's. But the type of circuit and component values used in your amp now has a lot to do with it.

Swapping 6550's in place such as the new reissued Tung Sol's would take a lot of that low end out and reemphasizes the mids more. Interchangeble with each other but with any power tube change just rebias the tubes after the change.

IF there is a ultralinear or triode mode selection on your amp, I'd say go for the triode mode..less power less emphasis on the low end but improves mids and high definition better.

But having said the above bass boom has also a lot to do with your present room acoustics and your speaker type.

Good luck Surprised

by JayJay Tue Jun 23, 2009 10:08 pm

Get check on the amplifier biasing first, auto-biasing or manually adjust biasing.
As mentioned by our good forumer here, some amplifiers use specific tubes to achieve the ideal amplification gain and are not meant to swap/change to different tubes specification directly. It will do more harm than gain.

Happy Listening.
Cheers.
Smile

by cmboy Tue Jun 23, 2009 10:26 pm

Tube amps are inherently slower transient speed than it solid state brethren. Slower bass lines can be perceived as bass boom, fuller bass, wetter, or more decay, whereas if the same notes are reproduced by a solid state amp, the amp can be capable of much tighter and drier at the lower end of the audible frequency spectrum, assuming its power matched to the speaker in question. Solid state transistors all have its own switching speed and the performance of these devices will have a bearing on audio sound reproduction. I remember a Marantz PM66 KI amp produced nice audible bass for one kind of Cai Qin track but when the amplifier was replaced to a much faster amp, the bass was just not that apparent. Its all in the design, speaking broadly about SS amps. Normal aspirated tube amps are slow, but not neccessarily boomy. Its all in the total synergy of all the components in place and the sound room. A terrible room void of any damping is not a nice place to relax and listen to hifi. (lets also not mix in the likes of exotic megabuck multiple parallel output tube config types into this equation).

Thats why high current solid state amps (those heavy mutha's weighing a ton and can fry an egg on it) are significantly more dynamic and maximum resolve, producing tight bass lines and sparkling performance, almost eliminating any audible bass boom. I trust the owner better reposition the speakers to minimize bass boom or re-arrange other household items in the room that may be resonant. Amplifier to speaker mismatch is another possibility.

by dixchen Tue Jun 23, 2009 11:22 pm

The beauty of tube amps is that one could inherently ' tune ' or alter the sound characteristics of its sound almost infinitely.

An avid tube gearhead by nature, the reason why I commented on the characteristics of KT88 tubes in any amps is that my tube amp in original nature came with KT 88 power tubes that did very little elsewhere except boom like how our forumer here has experienced. Very much to do with the original values of the components used in the amp circuit and also partially a natural characteristics of KT88 tubes.

That aside it is also possible to ' tune ' the particular amp to much more cleaner bass lines and not boom. One gotta know what he is doing though.

THe owner is also using floor standers that will typically ' enhance ' the typical bass response in any music compared to typical bookshelfs.

The irony of an audio system is that we can't have everthing we want always unfortunately..

by BrAvO Wed Jun 24, 2009 10:09 am

JayJay wrote:Amplifier that uses KT88 tubes; produce high bass and low treble output.
This is the characteristic of KT88 (fat body) and unlike EL34 tubes, which is slim; it has high treble and low bass.
So it’s the tubes that produce the bass sound.

Happy Listening.
Cheers.

Thanks Jay Jay for your info, I am fully agreed with you that the KT88 is producing the extra bass & less of treble (Fat sounding) Vocal is like the singer with heavy jaw. Will try the 6550 later to find out the result. By inserting the back firing port with sponge does help up to reduced the booming by at least 30% & it's sound much smoother at the present moment.

by BrAvO Wed Jun 24, 2009 10:22 am

azri wrote:nice info jayjay, but can we simply swap kt88 with el34?

I think the cross reference for KT88 will be the 6550.

by JayJay Wed Jun 24, 2009 10:27 am

BrAvo,
It is good to hear some improvement on your system, at least 30%.
Bravo... cheers

Lets look into this information if the amplifier to speaker is mismatch;

What is the power handling (Watt) and sensitivity (dB) of Physic Yara Evolution floorstand speakers?
What is the frequency response (Hz) and power rating (Watt) of the tube amplifier?
List all type of the tubes used on the amplifier.
How many tubes are used on the amplifier?

Happy Listening.
Cheers.
Smile

by BrAvO Wed Jun 24, 2009 12:12 pm

Found this page from the net about KT88 & 6550;

http://www.jacmusic.com/KT88/kt88.htm

by BrAvO Wed Jun 24, 2009 12:25 pm

ltra

JayJay wrote:BrAvo,
It is good to hear some improvement on your system, at least 30%.
Bravo...
Lets look into this information if the amplifier to speaker is mismatch;

What is the power handling (Watt) and sensitivity (dB) of Physic Yara Evolution floorstand speakers?
What is the frequency response (Hz) and power rating (Watt) of the tube amplifier?
List all type of the tubes used on the amplifier.
How many tubes are used on the amplifier?

Happy Listening.
Cheers.

Hi JayJay,

My speakers power handling is at 20-120W, 4 ohm & 89db.

The amp frequency response is 13Hz-60KHz (-1db), power rating of Ultra Linear 60W x 2 / Triode 30W x 2. I listen to Triode mode only.

There are 10 tubes for this amp with KT88 x 4, 6SL7 x 2, 6SN7 x 2 & 5U4G x 2.

Hope these informations can help you to figure out more solution for my problem.

Thank you.

by cmboy Wed Jun 24, 2009 12:58 pm

Ah!...rectifier tube 5U4G (or any other for that matter). Its traditionally a full tube amplifier and this will account for near vintage sound where its audio transient speed will still fall far behind any solid state amps. Newer/current or purposely designed amps mostly cut cost by using solid state rectifiers and this accounts for "not so vintage" sound or "newer sound" in understandable terms. Solid state rectifier are more efficient than its old tube counterpart, with much less voltage drop and other electronic inefficiency. In otherwords, the PSU section is more highly efficient and will deliver all the required current juice when required. Tube rectifiers have limitations but it contribute to the tonal quality that many tubeheads may want. The dynamics and pace is a lot slower than amps that use solid state parts in the circuitry. Similar to opamps, they all have specified slew rates and amplification speed specifications...other words, slow to fast. Same with amplifiers. Slower amplifiers, bigger and fatter bass lines. Faster amps, tighter and leaner bass. Loudspeakers are also seen as slow to fast types. The synergy between amp and speaker will result in speed issues. E.g. Fast amp + fast speakers = tight bass and leaner. My 2 sen.
I leave you to figure the rest and strike a balance somewhere.

by azri Wed Jun 24, 2009 6:41 pm

hi, anyone knows anything about 6BL8=ECF80 tube?
characteristics etc, im still new & still learning about tubes
sorry bravo, tumpang thread

by lkm Wed Jun 24, 2009 6:48 pm

BraVo,

If your tube amp has less than 100 hrs of operation, give the tubes a chance to burn in and keep the amp as far away from the speakers as the tubes are microphonic. I had the same problem with my amp when new and I thought it was the tubes (Chinese Shuguang KT88) that were problematic, so I switched to EL34 which sounded leaner but with better mids and treble. The tubes sound better given time so don't get worked up by switching tubes at this stage. After 3 months of using the EL34 (about 4 hrs per day of operation), I switched back to KT88 and have been sticking to it eversince. Btw my amp is a Prima Luna Prologue 2 that allows switching between EL34 and KT88. If the problem persists then only you should try better quality tubes eg. Svetlana (C), Tungsol, Electro harmonix etc.

by BrAvO Thu Jun 25, 2009 10:28 am

lkm wrote:BraVo,

If your tube amp has less than 100 hrs of operation, give the tubes a chance to burn in and keep the amp as far away from the speakers as the tubes are microphonic. I had the same problem with my amp when new and I thought it was the tubes (Chinese Shuguang KT88) that were problematic, so I switched to EL34 which sounded leaner but with better mids and treble. The tubes sound better given time so don't get worked up by switching tubes at this stage. After 3 months of using the EL34 (about 4 hrs per day of operation), I switched back to KT88 and have been sticking to it eversince. Btw my amp is a Prima Luna Prologue 2 that allows switching between EL34 and KT88. If the problem persists then only you should try better quality tubes eg. Svetlana (C), Tungsol, Electro harmonix etc.

Hi, lkm.

Thank you for you advise, for the time being I am using the Electro Harmonix KT88EH. You might get it right that I need to burn in the tubes & the amp too since I got it only about a week ago.

Does it mean that we can use KT88, 6550 & EL34 for our amp. I think the Prima Luna is having the automatic biasing system as mine Bewitch KT88.

I will be borrowing the 6550 from my friend today, will update with the result as soon as possible.

by lkm Thu Jun 25, 2009 1:30 pm

Yes, the Prima Luna Prologue 2 has the auto biasing feature which takes away the headache and uncertainty of adjusting biasing for optimum performance. I'm not aware that the Bewitch amp has this feature too. Best that you check with the dealer just to be on the safe side. To see the type of tubes which can be used as replacement, check out the 'Manual' section under Prologue 2 of Prima Luna's website. Another website giving sensible advice and good information on tubes is UpscaleAudio.com.

On thing I learnt in having a tube amp is that it requires a great deal of patience due to the breaking-in period of the tubes and the nature of the amp which requires a good 1/2 hour to warm up and sound good. At the 3rd to 4th hour, it sounds even better (and this is a common observation of valve amp owners). So be prepared to spend more time with your amp.

by JayJay Fri Jun 26, 2009 1:54 am

BrAvo,

Bewitch KT88 is a high current tube amplifier with 2 x 6SN7 as input, 2 x 5U4G as rectifier and 4 x KT88 as output. Just pretty like “Samantha” @ Elizabeth Montgomery and Nicole Kidman in Bewitch…

Since the Bewitch KT88 is rather new, the speakers may be sensitive from the change of solid state to tube amplifier. This is probably the transition/adaptation period between the speakers and tube amplifier and may need time to run-in/burnt-in (about 100 - 150 hours) on the tubes.

Important : -Get check on the amplifier biasing first, auto-biasing or manually adjust biasing because high bias/gain will shorten the life span of the tubes and produces unstable amplifier output.

Other possible experiment is to use a thin speaker cable rather than thick/fat one.

Is there any difference of using 8 ohms taps instead of 4 ohms?

Hope these information will help to solve your problem.

SUCCESS in life is not what we’ve accumulated in material wealth, but the sum total of the many lessons and experiences we’ve gathered from the various experiments/crises we’ve encountered.

Happy Listening.
Cheers.
Smile

by JayJay Fri Jun 26, 2009 9:28 am

BrAvo,

Any improvement or development on your amplifier?
Any difference of using 6550 tubes?

Happy Listening.
Cheers.
Smile

News on the demise of our beloved Michael Jackson has shocked the music world today.
May GOD bless his soul.
Hope HIStory and songs be remembered always.
Lets cherish them…

by **WongKN** Fri Jun 26, 2009 10:15 am

One of the biggest possibility I can think of, for this bass-boom problem, is that due to the frequency response matching of the new tube-amp to the speakers, there is an emphasis in a certain bass frequency. And unfortunately this frequency also corresponds to one of the resonance nodes (I think that is the term) in the listening room.

Note : resonance node. Unless one has a custom built room with custom dimentions and shape, otherwise all rooms that us normal hi-fi owners owns will have resonance nodes. These nodes are frequencies where the reflection of the sound waves off the room walls/floor/ceiling creates standing waves. As a result, the frequency becomes reinforced causing an artificial enhancement in the strength/volume of that frequency. This is one of the most common cause for the boom.

With the solid-state amp, it could be that due to its frequency balance, or perhaps due to its better bass control, there was no emphasis in that frequency. But this new amp, sometimes not due to any speaker control issue, can very well be just due to the tonal balance or frequency response of the amp, it will emphasize that certain frequency which if you are unlucky, like this case, it coincides with the room resonance and becomes a boom.

To check if this is the case, you can use one of those frequency testing CDs, where they have pure tones at various frequency. Or better a pure tone generator (difficult to find). Then test the various frequencies and see which one booms. If you still have your original solid-state amp, put that back in and test the same frequency to see if it booms or not.

If this is the cause of the boom, then the best way is to either re-position the loudspeaker or to put dampening materials on the wall, floor, etc.

For speaker re-positioning, try this (if you have not already tried yet, that is). Measure the dimension of your room : length X width. Now divide both dimensions by 3. Then you use masking tape and mark out the 2 points which are on the 1/3rd point of the room width (since there are 2 speakers) and 1/3rd distance away from the back wall. Place the speakers here and see if it helps. - I am of course assuming you have a dedicated hi-fi room where spouse-acceptance or spouse-approval does not come into consideration (spouse-approval is more important than sound quality, trust me).

For extreme cases, if one is a DIY guy, you can always built helmhotz resonators to absorb that specific fequency. Google the web for an explanation of the helmhotz resonator. Depending on the severity of the resonance problem, you might need to build more than 1.

Of course, the cause of the problem can also be tube run-in or one of the possibilities other memebrs are suggesting. The only sure way is to test.

by BrAvO Fri Jun 26, 2009 10:32 am

Sorry guys,

Not able to test the 6550 yet. Will be trying them out this evening.

by BrAvO Fri Jun 26, 2009 10:39 am

WongKN wrote:One of the biggest possibility I can think of, for this bass-boom problem, is that due to the frequency response matching of the new tube-amp to the speakers, there is an emphasis in a certain bass frequency. And unfortunately this frequency also corresponds to one of the resonance nodes (I think that is the term) in the listening room.

Note : resonance node. Unless one has a custom built room with custom dimentions and shape, otherwise all rooms that us normal hi-fi owners owns will have resonance nodes. These nodes are frequencies where the reflection of the sound waves off the room walls/floor/ceiling creates standing waves. As a result, the frequency becomes reinforced causing an artificial enhancement in the strength/volume of that frequency. This is one of the most common cause for the boom.

With the solid-state amp, it could be that due to its frequency balance, or perhaps due to its better bass control, there was no emphasis in that frequency. But this new amp, sometimes not due to any speaker control issue, can very well be just due to the tonal balance or frequency response of the amp, it will emphasize that certain frequency which if you are unlucky, like this case, it coincides with the room resonance and becomes a boom.

To check if this is the case, you can use one of those frequency testing CDs, where they have pure tones at various frequency. Or better a pure tone generator (difficult to find). Then test the various frequencies and see which one booms. If you still have your original solid-state amp, put that back in and test the same frequency to see if it booms or not.

If this is the cause of the boom, then the best way is to either re-position the loudspeaker or to put dampening materials on the wall, floor, etc.

For speaker re-positioning, try this (if you have not already tried yet, that is). Measure the dimension of your room : length X width. Now divide both dimensions by 3. Then you use masking tape and mark out the 2 points which are on the 1/3rd point of the room width (since there are 2 speakers) and 1/3rd distance away from the back wall. Place the speakers here and see if it helps. - I am of course assuming you have a dedicated hi-fi room where spouse-acceptance or spouse-approval does not come into consideration (spouse-approval is more important than sound quality, trust me).

For extreme cases, if one is a DIY guy, you can always built helmhotz resonators to absorb that specific fequency. Google the web for an explanation of the helmhotz resonator. Depending on the severity of the resonance problem, you might need to build more than 1.

Of course, the cause of the problem can also be tube run-in or one of the possibilities other memebrs are suggesting. The only sure way is to test.

Dear Wong,

My speaker position now is 1/3 from the back wall & 1/7 from the side, listening position is also 1/7 from back wall. This is what Mr. Adrian from Audio Image recommended me to place the Audio Physic. It helps to bring out the vocals & reduce boom from my previous solid state amp. The position is still remain unchanged for the tube amp.

My speaker cable is kind of thick with 12AWG solid core copper. Does tube amp requires only smaller guage cables?

by chua55 Fri Jun 26, 2009 10:44 am

try silver plated speaker cable. interconnect and power cable to tube amp.

I do encounter this b4.

I am using goldwater and CS102 MKIII, power cord is PCOCC.

if u still fint it boomy after acoustics treatment, time to think about matching.

by dixchen Fri Jun 26, 2009 5:12 pm

If you had already close up the rear ports, thus moving your speakers away from the side/back of the walls will decrease bass response. Then again really depends on the outlay of the room itself.

Given that the amp is only a weeks old and bias values rarely run by much in a short time of operation but bar that, I would think that it really has insignificant effect on such bass boom experienced by the owner.

As mentioned earlier, he is after all running floor standers on which given the nature of floor standers themselves and also through the clear explanation provided by our dear forumer on resonance nodes, amplifies whatever frequency that co incides with the resonant frequency node of the room he is in now.

I think if you follow his instructions clearly, you will notice that you can inherently ' tune ' the bass response of your listening room. While it could be suggested by your dealer on a particular positioning however you will find that there is no ' fixed ' positioning as many variables inherently change the response of your system as what is happening now. No harm trying so I guess.

After all 30W of tube amp watts is very very different to 100W of solid state watts...

by BrAvO Fri Jun 26, 2009 10:27 pm

Finally have some free time to tried the 6550 out this evening, after installing the 6550, on the amp & warm it up for about 30 mins.

No doubt that the 6550 is giving more higher frequency & I find that the vocal of Mary Black on No Frontier has more air & freely. For testing this 6550, i have removed the back firing port sponge.

Dear all, the bass booming is still there Crying or Very sad

It is time to do some room acoustic soon. May want to buy a few diffuser soon to place behind of speakers & center of back wall. May also put 1 behind of my listening seat to prevent any bass reflection.

by ryder Fri Jun 26, 2009 11:01 pm

For bass frequencies, get some proper bass traps and place them at the front two corners of the room. Diffusors are good for reducing direct reflections without deadening them and are effective for mainly mid to high frequencies which can be beneficial in making the sound more spacious without excessive brightness. Diffusion won't address bass problems. For bass boom, bass trap decreases the wave strength(reflection) by flattening the peaks and raising the nulls ie. fix suck-outs. Before attempting to try bass traps, experiment with speaker placement and listening position. You may be sitting at the peak of the waves where the bass frequencies are the strongest.

by **WongKN** Sat Jun 27, 2009 8:50 am

Bravo,

Since you bought the speakers from the dealer's whose setup / tuning skills I trust most, my best suggestion to you is to go back to Adrian and ask for his advice what's the next best thing to do.

by azri Sat Jun 27, 2009 8:19 pm

bravo, which tube amp did u purchased & how much does it cost u?

by uncle_vic Fri Nov 06, 2009 3:29 pm

apologies for bringing this old thread back.

my inferences from reading this thread.......

the amp's damping factor is in question, it's the 'breaking system'
for the drivers' cone movement. It's like a sport car with very good accelerating capability, the braking system have to be very good to compliment the accelerating power, so double disc brakes, all round and ventilated is preferable.

using tube traps and other devices to absorb the excessive energy is workable, but do look at it as loss of wasted energy! If the amp could handle so much, lets not give it excessive duties. division of labour may work another way, don't have the main speakers workout too much on the low bass, pass the duties down to the subwoofers, in some setups i have seen, the bass boom is reduced or almost negligible. But integrating subwoofer(s) to the main system is a real pain. hence most may choose to use tube traps instead.

closing the ports of the main speakers, will enable the bass to roll of earlier than the ported designs. the bass will sound more natural, though the impact on the bass in reduced. this is one way (somewhere in the thread, someone suggest closing the ports) to reduce bass duties to the main speakers, if so adding a subwoofer (if successfully done) will get the listener to a different level of enjoyment.

so it's either u absorb the unwanted excessive bass energy or u reduce its production from the main speakers and have the bass reproduced another way thru subwoofer. It's possible, can be done.

by wabun Fri Nov 06, 2009 3:57 pm

not all KT88 amp produce terrible bass. Melody SP9 sing well..
sure you will have less bass by connecting 4ohms speaker to 8ohms terminal, the mismatch will reduce maximum power transfer which
reduce output power but this is not a good solution..if I were you
I won't keep the tube amp anymore. seldom people will match
4ohms speaker with tube amp, especially high power one.

by cheelun Sun Nov 08, 2009 6:51 pm

I also have the same problem when I was using the hybrid Soundstage Integrated with Mordaunt-Short 906i. The boom was terrible on certain pop songs. I connected the said amp (which has a pre-out) to my wharfedale power cube 10. The problem is still there (maybe the placement of the sub was wrong).

The problem went away after I changed the Soundstage to AudioVega KT88. I use only the ultralinear mode as I mostly listen to slow rock and alternative rock. I found that the bass is now enjoyable albeit a little bit on the slow side. My audiovega still lacks behind in terms of punch and urgency compared to a SS amp. But getting a SS amp is not an option bcos I just love the looks of tubes ....heheheheheh.

Later on, I swapped the MS 906i for a pair of Zu Druid MK4. The sound is smoother now and I kind of miss the boomy bass .... ehehehehehe.

BTW, I am still using my Wharfy sub. Am looking for a good REL (if the price is rite) coz I heard that REL can blend in well with my ZU's.

In my limited experience, I believe the problem lies in the equipment. If the cost of room treatment exceeds that of the cost of equipment, i would suggest to just change the equipment. There's no point in having a set of tyres that is more costly the the CAR!

Cheers

by mugenfoo Sun Nov 08, 2009 9:01 pm

Yup, its the damping factor thats the reason for this kind of bass boom due to equipment.

Most probably, at that particular freq (where it booms), the speaker's impedance would probably have dipped very low and the Amp's output stage cannot properly control the woofer's movements. Hence the woofer rings like a church bell (albeit at this particular low freq) and quivers uncontrollably.

BUT, all being said ... have you checked what freq is it booming at ?

Does it correspond to one of your room's resonant modes ?

Its easy to verify this... and if so, maybe a simple repositioning job might solve the bass boom. No need to buy any new GEAR.

Lets see .. whats the formula... V=F x L,
V=speed of sound at room temperature, in metres per second,
F = frequency in Hertz,
L = length in meters

Multiples of half-wavelenghts would be the resonant frequencies.
E.g. at V=330m/s, and a room length is 6.6 metres, then the fundamental "boom" freq is 50Hz. (330/6.6 = 50)
A 50Hz signal would have a wavelength L of 6.6 metres.
So consider wavelengths of 3.3, 2.2, 1.65, 1.32, 1.1 .... metres, these lengths would nicely add up to 6.6metres (which is the room length). The corresponding standing waves. Which means boom at 50Hz, 100Hz, 150Hz, 200 Hz, etc etc ..... resonant freqs.

by Wan Azami Hamzah Sun Nov 08, 2009 9:08 pm

Goodness Mugen, ever thought of designing loudspeakers yourself? Don't talk all this jargon to me when we meet ok. It's too scientific. I'm into hi fi only for the music, not the science of it. Scaaarrryyyy.

by mugenfoo Sun Nov 08, 2009 10:00 pm

Wan Azami Hamzah wrote:Goodness Mugen, ever thought of designing loudspeakers yourself? Don't talk all this jargon to me when we meet ok. It's too scientific. I'm into hi fi only for the music, not the science of it. Scaaarrryyyy.

But its all simple mathematics ... and "mathematics is the language of the universe" ! (some really brainy dude said that).

by Wan Azami Hamzah Sun Nov 08, 2009 10:52 pm

Sure for some brainy folks, yourself therefore included. I don't speak hi fi language in mathematical formulas I'm afraid.

by mugenfoo Mon Nov 09, 2009 12:32 am

Got one piece of spare 7 or 8 inch tube trap about 4 ft tall thats lying around and doing nothing ... Still trying to figure out what to do with it.

by sting Mon Nov 09, 2009 8:23 am

I didn't read all the responses as it's too long but here's my opinion..

The booming could be the amp wattage of wpc is too low for your speakers (in this case your amp will go kaput easier than your speakers) and the interaction of the woofers movements due to distortion...

To all hifi sifus out there, sorry if I'm wrong....

by sting Mon Nov 09, 2009 9:11 am

adding up...

my previous Naim 202/200 (70wpc) was setup around Dynaudio and it was fine until I matched them with Von Schweikert VR1 Ref...the bass especially as the VR1 is easier to drive even with 16wpc Single ended...

by mugenfoo Mon Nov 09, 2009 9:39 am

sting wrote:I didn't read all the responses as it's too long but here's my opinion..

The booming could be the amp wattage of wpc is too low for your speakers (in this case your amp will go kaput easier than your speakers) and the interaction of the woofers movements due to distortion...

To all hifi sifus out there, sorry if I'm wrong....

Go read up on this:

http://en.wikipedia.org/wiki/Damping_factor

"Damping factor describes the ability of the amplifier to control
unintended movement of the speaker cone near the resonant frequency of
the driver."

Any reference to amp wattage there ?

by sting Mon Nov 09, 2009 9:59 am

mugenfoo wrote:
sting wrote:I didn't read all the responses as it's too long but here's my opinion..

The booming could be the amp wattage of wpc is too low for your speakers (in this case your amp will go kaput easier than your speakers) and the interaction of the woofers movements due to distortion...

To all hifi sifus out there, sorry if I'm wrong....

Go read up on this:

http://en.wikipedia.org/wiki/Damping_factor

"Damping factor describes the ability of the amplifier to control
unintended movement of the speaker cone near the resonant frequency of
the driver."

Any reference to amp wattage there ?

did you read the fine line at below my post there?..."To all hifi sifus out there, sorry if I'm wrong.

...and you're the SIFu in here...sorry bro, you're knowledge make me feel very small.

and I didn't say about movement of cones due to wattage?..maybe the booming thing with wattage, did I? sorry if I did....

My reference to distortion could be anything in the chain...I don't know..it just from my previous experience....damn..need to learn more...

by sting Mon Nov 09, 2009 10:14 am

ok, sharing is caring....from polkaudio website. Didn't mean to attract any conflicts..again I possibly wrong even before I contribute in this thread...

Feed Forward

Advanced Distortion Supression Technology

Too much power from the amplifier causes over heating of the
voice-coil, higher distortion and ultimately failure of the woofer
driver.
Too little power available from the amplifier causes high
distortion in the signal fed to the woofer driver, generates excess
heat and may eventually burn out the amplifier.
Excessive movement of the driver cone caused by over driving at low
frequencies leads first to high distortion, then to objectionable
mechanical noises and finally to mechanical damage to the woofer driver
as it literally tears itself apart.

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