A new micro-TL speaker for my wife

Hari Iyer

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My TL FS speakers and my pre-amplifiers connected to the Dared VP-300B tubes are very in-convinient for my wife to use as it involves swithching on multiple devices for her. She last week requested me a simple system which is just plug and play and that which can play music from her smart phone and usb device and above all NOTHING fancy. She even told me to get one of the sound boxes available as she wanted a portable device to move it from the kitchen to the bedroom.

I wondered if this is the new trend of how music is going to be listened too? Are the new generations also thinking likewise? This tempted me to design a new micro-TL speakers- one that is portable, not heavy weight and also having a fabulous sound stage. I thought of the suitable amplifiers that will be paired with this new TL speakers and found the Topping TP30 with the USB interface to be suitable for the speakers.

I will be using a 3.5" full-range driver along with this micro-TL loading and the terminus will be below the driver. The driver will be a Titanium doped poly proplene cone and will be using a compensation network for balancing the harmonics to allow the low, mids and highs to be in sync. The speakers will have to be placed appropriately if extended lows are required.

As my wife 95% of music taste is more of carnactic classicals, bollywood oldies (kishorekumar / Lata Mangeshkar / M.Rafi) types, occassional Gazals etc, i am not much worried about going anything lower than 50Hz. More over the available sound box in the market will seldom go below even 100Hz.

I have done a simulation of this micro-TL and the simulated response shows a low end response of around 60Hz (-8dB reference) and a high of around 18KHz( -8 dB reference). Due to the advance TL loading and improved compensation network the speakers are very smooth in the mid-range and tight in the lower end. Extended listening for over 3 hrs and more will tend to cause some amount of listening fatigue most attributed to the Titatinum metal cone, but i think this is due to the driver not being break-in. Playing it at moderate levels over 200Hrs will allow me to discover this. Currently only the unfinished prototype is ready and the finished version should be available in another 2 weeks. Will post the images after the final speaker is ready. Till then stay-on.
 
Features of the new micro-TL speaker:


Enclosure:

1. Diffraction and edge corrected baffle

2. Coherent sound stage

3. Wave guides for lows & mids

4. Guided wave Transmission Line enclosure ensure no boom bass stimulating atmosphere of live performance and extended dynamics

5. Harmonics balanced to ensure real life performance of music and vocals


Compensation Network:

1. A new harmonic balance compensator is introduced in this speaker to allow perfect sync of the lows, mids and highs. This will ensure no listening fatigue for extended hours of listening sessions. The mids and highs are very mellow and smooth and allows long hours of soulful music.

2. Excellent Transient & Phase response
3. Excellent on & off- axis response due to advanced compensation network.

Drivers:

1. Titanium metal doped polypropylene cone ensures stiffness required for mids and highs. The resonance of this driver is tuned and aligned with the transmission line for lowering the impedance at resonance there by ensuring deep bass at lower frequencies. This is in turn matched with the Harmonic Balance compensation allowed a well balanced sound stage across the music spectrum.

2. Wide range drivers ensure optimum performance in the entire frequency band-width of the speaker system
:)
 
Specification of the micro-TL for interested FM:

Power Bandwidth (-3dB) : 80 Hz till 16KHz
Frequency response (-6dB) : 60 Hz till 20 KHz
Nominal Impedance : 8 ohms
Minimum Impedance : 7.1 ohms
Continuous Power : 40 Watts
Max Power @ 8 Ohms :60 Watts
Enclosure Type :Linear Micro Advanced Transmission Line -BS
Compensation Network : Harmonic Balance, Level matching and Smoothing network used
Cross-over frequency : Not Applicable
Cone Break-In Time : Approximately 200 Hours with moderate sound pressure
Driver : 3.5" Titanium dope polypropylene cone
SPL /w/m : 88 dB (measured)
Max Recommended Speaker Wire Impedance : 0.5 Ohms or 1dB loss
Dimensions (H x W x D) Inches : 13.5"x 5"x 9"
 
Hari, you might have come up with something for a lot of people as a bed room system.
BTW, where are the pics of the prototype?
 
Hari, you might have come up with something for a lot of people as a bed room system.
BTW, where are the pics of the prototype?

Thanks iaudio. This micro-TL can be an ideal system for small rooms where placement is a challenge. The dimensions are very modest, yet it does full justice to the low frequencies if placed appropriately. The prototype has a different TL loading internally and the external looks are also quite different. I will post the images within a week when i have the final product. Till then stay tuned.:)
 
Finally got the box picked up yesterday evening and quickly completed my simulations and assembly. Here are some images.

14ditqd.jpg


kb3g9i.jpg



2eyud7k.jpg


Will post measurements and listening impressions later
 
Here are the measured values for the micro-TL speakers,

2agnux5.jpg


The unstuffed line impedance peak indicate accurate tuning of the line frequency with the driver resonance frequency. Also the odd harmonics are visible clearly in this measurement.

21klekg.jpg


The stuffed line deadens the two peaks and a single smaller peak at driver resonance is seen. Also all the odd harmonics are damped with stuffing.
The line frequency helps to deaden the driver resonance and the stuffing helps to deaden the odd harmonics.

rc6k9i.jpg


The response of the speaker system with compensation network installed.

2my46dx.jpg


The combined response of the unstuffed line and the stuffed line with compensator network.

Cheers,:)
 
Re: A new micro-TL speaker with wide sound stage

Made a single channel Frequency Response measurement at 1 meter distance. Will require some tweaking in the 2KHz to 8KHz region.

2wdn1c7.png
 
Last edited:
Hi,
Today I got chance to hear these ones.They look nice not only in pictures but also in real world too.Cute curves give rich feeling.The net grill also is solid.How do they sound?
They are very open and bring out details in recordings.They have wide sound and appeared musical.Since they are full ranged,no issues related to cross over.Overall sound is lively,not very bright.Bass is good but not as deep as it should be.Yes its obvious that the driver matters.But for near field listening,like PC set up,they should be a good choice.Overall it delivers balanced sound with very detailed approach.
Its outcome of certainly great efforts by Hari.:thumbsup:
Cheers.
 
I have off-late modified the compensation network to make the FR more flatter, the impedance more flatter and the impedance phase offer a more resistive load to the amplifier. The overall improvement is seen in its outcome.

1z5699c.png
 
Hi,
Today I got chance to hear these ones.They look nice not only in pictures but also in real world too.Cute curves give rich feeling.The net grill also is solid.How do they sound?
They are very open and bring out details in recordings.They have wide sound and appeared musical.Since they are full ranged,no issues related to cross over.Overall sound is lively,not very bright.Bass is good but not as deep as it should be.Yes its obvious that the driver matters.But for near field listening,like PC set up,they should be a good choice.Overall it delivers balanced sound with very detailed approach.
Its outcome of certainly great efforts by Hari.:thumbsup:
Cheers.

@Spirovious
FM Sumanta heard these speakers 3 weeks ago and expressed similar sentiments with the micro-TL. Currently i am using them as my HT surround and Center speakers. The TL FS is my front speakers and i am getting amazing sound stage and experience. In your next visit we can explore the HT options with these gems minus the sub.

Cheers,
 
Below are images of the previous version and current version of the tweaked cross-over network actual measured values using REW.

2q9gffm.jpg



ibjl0i.jpg


As you can notice the simulated and measured impedance is within 5% of it value.
 
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