The Metronome - mass loaded TL speaker - Make in India

[Hari Iyer]

Completed my last and final tweak on the Metronome which was pending for more than 2 months now with full success. I can now fully say that the Metronome project is complete in all aspects. Will now only have to do some polish touch-ups.

The final tweak was for the step response accuracy that determines the phase coherence of the speaker system. I have achieved this by a physical offset of the woofer and tweeter voice coils. The Fostex having a deeper cone, i had to go for an offset of almost 40mm with the Ribbons to achieve the accurate step response. (Will post images later_ Also tweaked the cross-over a bit for the crossover frequency and accurate filter phase.

Here are the images of the final outcome for the diy community.

Having an accurate step resonse (read phase coherence) removes the mid-range clutter as the vocals sounds very accurate. If there is a time difference between woofer and tweeter, the high frequencies reaches your ears earlier than the mids and lows causing the vocals to smear a lot and adding clutter fatigue to the sound stage. When the highs, mids and lows arrive at your ears at the same time, you get very smooth sound stage and the entire music just flows like real live performance and you can enjoy long listening hours due to absence of fatigue.

 

[jmascreen]

Any pointers to get these drivers I am looking for the 4" or 5" one

Sent from my Moto G (4) using Tapatalk

 

[Hari Iyer]

Any pointers to get these drivers I am looking for the 4" or 5" one

Sent from my Moto G (4) using Tapatalk

When i searched last year, madisound had the best deal w.r.t price and shipping charges. If you are lucky you may get a better deal.

 

[jmascreen]

When i searched last year, madisound had the best deal w.r.t price and shipping charges. If you are lucky you may get a better deal.

Thanks Hari, I would prefer local first (any pointers,diyaudiocart is out off stock) if not able to get then will go with madisound

 

[Hari Iyer]

Thanks Hari, I would prefer local first (any pointers,diyaudiocart is out off stock) if not able to get then will go with madisound

diyaudiocart did not have the model which i was looking for and hence did not buy from them. Price wise both are similar even if you include the customs + shipping. Infact it was cheaper by few hundred rupees to buy from madisound if i remember correctly.

 

[Hari Iyer]

Posting some measurements with brief explanation of my own analysis for the diy community. This was measured last month but was too busy to post

SPL:

Shows the frequency response in my listening room for a swiped response from 10Hz to 20KHz. The response is reasonably flat from 200 Hz till 20KHz inspite of no room treatment.

Step:

Displays perfect time alignment and phase coherence beween the fostex full range and Audiopur ribbon tweeter which is offset by 54mm from the front baffle.

Impulse:

No stored energy inside the box as the impulse settles down immediately after the falling step.

Schroeder Integral:

The random noise continues till the falling step of the impulse response and the schroeder integral line shows a perfect exponential decay past the room noise. This is inspite of not using any room absorbent material.


Decay:

Even decay of responses from the inital response to T120ms from 20Hz to 20KHz with no stored energy at the lower frequencies. No room treatment used.

GD:

No major peak in the GD after 200Hz.

Waterfall:

Even response in the high and mid-freq, though the lower mid could have been better.

Spectrogram:

Some energy storage in mid and high freq typical of a full range driver and ribbon tweeter.

 

[Hari Iyer]

..................................

 

[Hari Iyer]

Update

- simulated and measure impedance and phase - Final
- Simulated square wave response - Final
- Latest images taken today. - The fostex FR and Audiopur RT has an offset of 54mm for time alignment.

Currently dont have the microphone with me and hence cannot show the step, impulse response. Planning to buy one soon.

 

[prem]

Heard Hari's new creation last weekend along with Sumanta. The speakers look very nice and is solid and quite inert. However couldn't really figure out what the speakers are capable of since I found his room and associated electronics a bit of an issue. Am sure given the right electronics and the right room, his speakers should sound very good since a lot of effort has gone into designing them

 

[Sumanta]

I once heard a Metronome in Kolkata some years back but I think the drivers were of Philips. The reference I brought here is because they were placed, (as I remember and realize now) right in the central part of the room with near field listening mode. Which most of us can not afford for various reasons.


As I think more, I think Hari can have
1) Wall mounted or cupboard bookshelves and a sub-woofer
2) Omni speaker of light weight design.
3) Stand mount OBs with fixed sub-woofer ( I am an OB-dict)

I once made Omnis and they can bring wonderful imaging like OBs in a small place. Not that cabinet ones do not make wonderful imaging, OBs use walls for imaging which is more forgiving for our halls.

 

[prem]

Agreed Sumanta, it's very important to have a speaker that works in your room

 

[Hari Iyer]

I once heard a Metronome in Kolkata some years back but I think the drivers were of Philips. The reference I brought here is because they were placed, (as I remember and realize now) right in the central part of the room with near field listening mode. Which most of us can not afford for various reasons.


As I think more, I think Hari can have
1) Wall mounted or cupboard bookshelves and a sub-woofer
2) Omni speaker of light weight design.
3) Stand mount OBs with fixed sub-woofer ( I am an OB-dict)

I once made Omnis and they can bring wonderful imaging like OBs in a small place. Not that cabinet ones do not make wonderful imaging, OBs use walls for imaging which is more forgiving for our halls.

Thanks for your suggestion about OB. The OB speaker if i make cannot b more than 4" due to space constraint. Also the subwoofer need to be as compact as possible to accomodate with the OB.

In the meanwhile i have made some changes to the Metronome and now it sounds like a totally different speakers that what you heard last. I may not comment what it sounds like, its for others to discover and comment.

Cheers,

 

[Sumanta]

The OB speaker if i make cannot b more than 4" due to space constraint. Also the subwoofer need to be as compact as possible to accomodate with the OB.
Cheers,

That's exactly the point. Have a narrower & thinner speaker than your current one yet get better suitability in your room.

A Ripole, interestingly can be more compact than a closed/ported sub.
If you have a 4" Mid, instead of 6.5" that you have now, you most probably would not corss 90 dB. To have a sub of similar SPL, I suggest you make a TL sub, or may be two subs attached. And you are a TL speaker maker already.

I will come for listening the new one someday. We can bring your one in my listening room too to see if it is really the room that is impacting as much as we felt. And if Prem can bring one of his amps, that will be the icing.:yahoo:

I have a tube amp as well which is not in use now.

It is the journey that I enjoy.

 

[Hari Iyer]

Question, did you make the cabinets yourself or had a carpenter do it?

Family carpenter for past 25 years

 

[Hari Iyer]

That's exactly the point. Have a narrower & thinner speaker than your current one yet get better suitability in your room.

A Ripole, interestingly can be more compact than a closed/ported sub.
If you have a 4" Mid, instead of 6.5" that you have now, you most probably would not corss 90 dB. To have a sub of similar SPL, I suggest you make a TL sub, or may be two subs attached. And you are a TL speaker maker already.

I will come for listening the new one someday. We can bring your one in my listening room too to see if it is really the room that is impacting as much as we felt. And if Prem can bring one of his amps, that will be the icing.:yahoo:

I have a tube amp as well which is not in use now.

It is the journey that I enjoy.

Carrying the Metronome will be a challenge as it will not fit in my car. I have made the following major changes to the design,
- using varying stuffing density. The stuffing at the top half is now one third of bottom half. This has a advantage of tight bass, elimination of mid freq related resonance to interfere from the port. Also the cone motion is better controlled without any boom.
- Remove the first order low pass filter from the full ranger and keep just the zobel to prevent the rising impedance at the higher frequency without sacrificing the FR of the driver.
- Operate the tweeter only where it's required from 10kHz onwards where the Fostex rolls-off rapidly. This allows for less phase shift and is any way not audible. A tweeter crossed at 2kHz if not phase coherent is easily audible.
- Move the speaker 3 feet from the rear wall and about 1.5feet from the side walls. A small 10 Deg toe-in was done to get the center image resolution.

After these mods, subjective listening has made the Metronome a ruthless speaker. The vocal details and scaling, and the overall timber mimics the recording. For a well recorded source the speakers are very open and natural sounding. Conversely for a poorly recorded source the speakers are ruthlessly honest about that.

 

[Sumanta]

I guess then you are done. Enjoy the music now.

 

[Hari Iyer]

After one month of accurate simulations and countless iterations, finally was able to get the right balance for the Fostex FR and Audiopur RT. This was assisted by the Xsim crossover simulator by giving me the near perfect square wave response for the speaker system. This also time aligned the drivers by giving a near perfect step and impulse response.

I modified the speakers yesterday evening and was overwhelmed by the final outcome. Now no more mods will be required for this project. I have yet to complete all my subjective listening with the Metronome.

 

[keith_correa]

I modified the speakers yesterday evening and was overwhelmed by the final outcome. Now no more mods will be required for this project.

Famous last words?

 

[Hari Iyer]

Famous last words?

Absolutely. IMO this is what "Passion" is all about and also my signature tells this. Never settle unless you are more than cent percent satisfied with the outcome.

I was still playing with the stuffing yesterday evening. Trying to figure out will low stuffing or moderate stuffing will be well suited. Low stuffing gives more low end lift but also increase the mid-range presence. Moderate stuffing gave me a tighter bass but the low-end extension was a higher by a few Hz. But this also gave me a better control of internal standing waves and resonance and the mids were very lively and presentable with moderate stuffing. Now this experiment was done with just one speaker and i tried comparing the left (low stuffing) and the right speaker (moderate stuffing) - apples to apples - side by side with mono signal been fed. All the time the moderate stuffing suited to my listening taste. Will be doing some more test with other tracks to substantiate the findings.

 

[Hari Iyer]

After listening to some more tracks finally settling for the moderate stuffing TL box. Will post some impedance measurements later for the low stuffing and moderate stuffing for the diy community.