Contemplating a TL sub

[Hari Iyer]

Its almost an year that i built 'The Metronomes' and have been enjoing every bit of them. In my stint, the most challenging aspect of living with the Metronomes have been placing the speakers optimialy in my puny living room. As always the best placement of speakers in any room is not practical and in my case they are very close to my main door. ie. 3 feet away from the rear walls and 1.5 feet away from the side-wall. But unfortunately the left speakers opens to the main door making this placement a heavy challenge. Currently i have been placing the left speakers here only when i am listening to music and after that i goes back to the rear wall making this exercise rather boring on a daily basis. So what are the options,

1. Find out the 2nd best place for the Metronome which is just not existing due to centre image error, bass boom and too much side wall reflections.
2. Diagonal placement - have tried this with excellent mid-range presence and organic sound but very weak low end lift.
3. Subwoofer - just contemplating if this will work which in principle should but don't know unless i try and make one.

Was trying to work out the associated cost and have asked for some quotes of the subwoofer plate amplifier and drivers. Have fixed a budget too as it needs to be well within my estimates.

Again the challenge in selecting the drivers and the box loading is going to be the room as too big a subwoofer box is a big no no for me as it will have a poor WAF. Hence have to settle down for 8" subwoofer driver to fit in the tiny space between my AV Rack and the main-door without booming. I have done one ML TL simulation using an IWAI 8" subwoofer driver and the results were quite encouraging and acceptable. Dimension wise also it was quite modest to have good WAF. But i will have to procure, measure and simulate again to confirm this. The current Metronome itself is too huge a speaker as per Indian standards and having one more huge speaker in my living room is going to be like asking for more trouble.

The simulation gives a me a -3dB of 28Hz, and a -10dB of 23Hz with the published TS values. The dimensions are H-30", W-9.5", D-11.5" if i can call it small. The woofer is front firing and the port bottom firing. Keeping my fingers crossed on this.

Thanks for looking.

 

[VSTEREO]

Waiting eagerly to see subwoofer getting shape. My wishes sir.

 

[heliumflight]

Sir, you have a passion for innovation. Can you make subs if I provide a pair of 8" Kef B200 drivers- http://p10hifi.net/TLS/drivers/images/B200_SP1039.gif Do let me know the frequency response and cost involved?

 

[Hari Iyer]

Sir, you have a passion for innovation. Can you make subs if I provide a pair of 8" Kef B200 drivers- http://p10hifi.net/TLS/drivers/images/B200_SP1039.gif Do let me know the frequency response and cost involved?

I have seen the TS parameter and this driver will be suitable for a nice 2-way FS design as it has a wide frequency range till 3.5KHz. Also the flux density is around BL=7.5Tl which is low considering a subwoofer design. I would rather prefer over 10Tl for greater power handling for a subwoofer design. This driver has a huge Vas and actually can give very deep and punchy low end.

 

[heliumflight]

British quality. Each driver weighs 3kg with huge magnets. May I have the shipping address please

 

[Hari Iyer]

FMs who know me personally would also know that i am not a subwoofer fan. They are quite right at their assessment. Hence in this month i would try if i can avoid the sub. This is because i have my own worries in 2 fronts -
A- finding the right space to keep them in my room.
B - integrating the sub with the main speakers and the room without boom and level matching. IME, most listeners are tuned to listening boom music and may not find boom with the sub. In my case i have been on TL for almost 10 years now and know what exactly is boom if i carry my reference music and listen to any system. IMO even to identify boom you need some training and experience.

In the meanwhile, I have ordered a Dayton Audio UMM-6 measurement microphone which should arrive in another 10 days. I will use to measure the Metronomes and check out if there are any phase issues or any frequency response anomalies to be addressed first in them.

Also i will try and simulate some simple BSC circuits which could tame the upper mids and highs a bit which could prevent them from masking the mid-bass and lows. The easy way to do this is to keep the BSC outside the box till the time you get the correct level listening by ear method. But the challenge hear again is to use the correct reference music to tune the speakers. This exercise itself takes a month or so tweaking with different music till the best compromise is reached for your speakers and room. If i am able to get the best balance between the lows, mids and highs then i may probably not pursue the subwoofer route. Keeping my fingers crossed on this one too.

 

[sound_cycle]

IME, most listeners are tuned to listening boom music and may not find boom with the sub.<snip>IMO even to identify boom you need some training and experience.

In the meanwhile, I have ordered a Dayton Audio UMM-6 measurement microphone which should arrive in another 10 days.

I agree completely to the first part about getting used to listening to boomy rooms. I have had friends come to my place and actually prefer the boomy bass over something more controlled and tuneful.

I don't forget that was where I was when I started (and for quite a while after), but I can longer stand to hear music in an untreated room which sound as bad as the "dhinkchak" share autos I encounter on my commute (and TBH my treatment is rather rudimentary and very basic, I am sure I can do a lot better). Aside: I've also seen pics of setups in small rooms with nothing but bare walls, and wondered why people don't put in even basic treatment which would improve their listening experience per rupee more than anything else would, for starters they would at least get a halfway decent phantom centre.

I went the software route to bass control (and you could consider trying the trial when you get your measurement mic.) I'm certain, no let me correct that I bet, that you will not need a sub. I'm hoping that an amp upgrade (on its way) over my int. amp will give me a bit of bass slam that I wish I had.

ciao
gr

 

[sound_cycle]

<duplicate of post #7 deleted>

 

[Hari Iyer]

Treating boom bass becomes rather difficult as you need to have thick absorbent at corners to tame the bass. This is not a solution at-least for me for aesthetic purpose. Hence am thinking of ways to level the current speaker response as much as possible. May be measurement could help me to some extend to know how much dB needs to be reduced in the mids and the highs to achieve this. Theoretical is 6dB, practical is around 3dB to 5dB depending upon speakers and room. Some times around 8dB also sounds good depending upon other constraints. Its better to have someone around who is more knowledgeable about subjective listening to fine tune along with you. It really helps.

 

[sudhirbhosale]

Its almost an year that i built 'The Metronomes' and have been enjoing every bit of them. .

What is benefit of Metronomes' . Are there any design parameters like size, shape, weight? What is success factors of best Metronomes'
Where / or for what types of speakers it should be used or should not be used?

Thanks

 

[Hari Iyer]

What is benefit of Metronomes' . Are there any design parameters like size, shape, weight? What is success factors of best Metronomes'
Where / or for what types of speakers it should be used or should not be used?

Thanks

The Metronome is a type of ML TQWT (Mass loaded Tapered Quarter Wave Tube) which uses a expanding taper in my case. The taper ratio is 1:10. The port is at the bottom and is tuned at 59Hz slightly above the resonance of the Fostex to reduce excessive cone vibration at low frequency. '

Mostly full range drivers of a particular type are suited for this design where you require low to medium stuffing and will like to bring out the midrange very clearly and articulate. Due to the low stuffing the Metronome behaves like a hybrid horn. For frequencies below resonance it behaves like a horn and hence only 60% of the box require stuffing from top to around little below the FR driver. The bottom 40% need not be stuffed. The best way to stuff the box is to do impedance measurement while stuffing and get it right as per recommendations.

I read more about the Metronome from this link and redesigned for my version of the Fostex using LA TL simulator. The Metronome

 

[Hari Iyer]

I have a pair of Bolton 10" woofer which was barely used for 20 odd hours when it was purchased, which i resuscitated from my loft yesterday and was wondering if they can be a good subwoofer drivers. After a bit of cleaning i measured the VC resistance and it showed 7 ohms. But when i connected there was huge disortion at the low frequency anything below 50Hz. The cone was completely compressed and offered stiff inertia to any movement as this was unused for almost 25 years. Since the cone material was polypropylene this was as good as new without damage.

I have now given this driver for re-coning with a new voice coil and a new coated paper cone locally. This replacement cone has a rubber surround. This woofer has an impressive 2 inch voice coil. I will be getting this driver back on Friday after which i will do TS parameter measurement after the usual break-in period. He also showed me the voice coil and it has a paper former. Also he has a polypropylene / paper dust cap.

I checked with the speaker repair vendor and he told me that all his materials are from Taiwan imported. Going to LT road would have had better choice and variety but i was too bored to travel that far. More over it would be like travelling twice. Keeping my fingers crossed on this one too.

 

[Hari Iyer]

I measured the TS Parameter for the reconed woofer and final designed a ML TL box for this subwoofer. The cone mass is high and so is the stiffness. Will power them with a 200 Watts subwoofer amplifier which I have yet to purchase.

The box dimensions are modest and will have WAF in my favour. To design using LA, I had to do a bit of out of box approach as the know method was not suitable for this driver. The box has an unusual high stuffing and approximate more towards a sealed or Aperiodic type enclosure. The -10dB extension is around 27Hz.

 

[Hari Iyer]

I will now keep this project on hold as of now, as my current stereo speakers are able to fulfill my bass requirements with ease and I am not feeling any loss of low frequency at the bottom end.