Designing a 2-way bookshelf speaker

[Hari Iyer]

A very well researched and best design approach taken by Tarun.

In your next simulation images, will be eager to look at the impedance phase and the filter phase of the woofer, tweeter and system.

In my design i give more importance to phase than the non-linear response of the drivers. Imo if you have carefully chosen the fc and have taken the precaution to tame the resonant peak of the driver 80% of the battel is won. The rest 20% should be getting the phase accuracy. Getting the phase correct is going to be the game changer in the design ime.

All the best.

 

[avesbilal]

I went over to diyaudiocart, since they have the biggest range of drivers in India. I wanted to choose a 6.5" or 5.25" driver for my midbass, and a tweeter which would be reasonably easy to mate with it.

For the midbass driver, I can see the following options:

• Fountek FR135EX -- can be crossed over fairly high, like 3K, if I want
• Fostex FE126 -- expensive. And the SPL unevenness always makes me a bit nervous with Fostex drivers. These drivers seem to be preferred by those audiophiles who like "character" to their sound, like valve amp lovers. I like transparent.
• Dayton PS180 -- very expensive. And quite uneven SPL again.
• Peerless 830657 -- this is not Peerless India, but Peerless of Tympany. Good driver, very difficult to tame the resonant peaks
• Dayton PK165 -- ditto
• Fountek FM135 -- power handling is a bit too low (I'd like at least 40W) and Fs is not mentioned. If they call it a midrange, I presume their bass extension will be too weak to be very attractive in a 2-way. Frequency SPL curve is smooth and easy to work with.
• Peerless India M13NH -- no SPL curve. No idea how good or bad it will be to work with. Coated paper cones from Peerless India are usually benign in their graphs, and are easy to fit into a decent crossover. Their stamped steel frames are mediocre, but will probably be acceptable in the kind of speaker I'm thinking of.
• Peerless India SM16IH-4 -- stamped steel chassis, typical of their budget models. But the really smooth SPL curve and the fact that it's a coated paper cone probably will result in an easy, simple crossover delivering good performance.
• Peerless India S16NI-8 -- another mediocre frame, another smooth easy-to-use SPL curve, very suitable for a simple 2-way crossover

My choice would have been the Peerless India M16KI, but as luck would have it, it's out of stock. If I understand the supply chain of these things, it'll never come back into stock again.

The Peerless 830657 is a better built driver than any of the Peerless India models, but its SPL curve and resonant peak would make it a real dog to fit into a reasonable passive crossover. These drivers are great to work with if I had the power of an active xo.

Looking at the options left, the Indian SM16IH-4 seems really attractive. It has an easy and smooth SPL curve, its bass extension will (if I trust the spec sheet) be decent with Fs in the mid-forties, and its 4-Ohm impedance will mean that it'll suck more power from the amp than the tweeter, thus probably minimising the need to match tweeter and midbass SPL levels. If the spec sheet is to be believed, it's also a pretty sensitive driver, rated 92 dB/W/m.

For the tweeter, I can simply go with the old standard Peerless India SR10DT, an excellent tweeter if one can afford to cross over at 2.5KHz or higher.

Hi Tcpip,

The driver you mentioned peerless MK16ki looks in stock on theaudiocrafts.

I don't have any commercial interests with them, just thought of mentioning it as your build will be a learning for FM's like me. So that we can copy from you at later stage[emoji12]

http://theaudiocrafts.com/drivers/midbass/m16ki-6-5andquot-black-kevlar-woofer

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[tcpip]

Ya, I saw that. Wish there was some Vas data for it, so that I could design the box size quickly. Now if I choose to use those drivers, I'll first have to make a test box, fit them to it, take measurements to get the Vas, then design the final box size accordingly.

See, with speaker design you can't avoid taking (i) impedance measurements, to get most of the T/S parameters, and (ii) final SPL measurements needed for the crossover design. These two are needed to let you design the box and crossover.

The third measurement, of making a test box and fitting the driver in it, and making an impedance of driver-with-test-box, is an additional headache and expense, just for Vas. It's a pain, and I am lazy. But without a reasonable idea of Vas, you can't arrive at the box size.

With foreign drivers I use the Vas given in their datasheet, so I avoid making a test box and doing this extra round of measurement. All other measurements must be done anyway.

With Indian drivers, that option is not there. The box must be made and the extra pain must be taken. I'd done it for the first Asawari -- those drivers were the 4-Ohm first cousins of this MK16i. If I choose the Miami again, I'll have to do that again.

But I am sure xo design will be simpler with this driver. The Peerless HDS driver or the Dayton RS driver will have huge cone breakup challenges which will make the xo difficult.

 

[keith_correa]

Won't the added mass method work for deriving Vas?

 

[tcpip]

I've tried that. It's very hard to get it accurate. You need to keep a mass on the cone but it must stick to the cone, not vibrate independently. If I stick something to a cone properly, it will be with super-glue, which will damage the driver. I tried BluTack, but it doesn't stick the weight well.

 

[keith_correa]

I've tried that. It's very hard to get it accurate. You need to keep a mass on the cone but it must stick to the cone, not vibrate independently. If I stick something to a cone properly, it will be with super-glue, which will damage the driver. I tried BluTack, but it doesn't stick the weight well.

I've seen it done by a relatively heavy ring placed on the dustcap. Because of the weight it doesn't vibrate independently and the ring by nature of its shape stays put. Maybe you can try that.

 

[avesbilal]

In a video by part express, he used a paper Tape as the weight. The video is on YouTube and he was measuring a Dayton driver.

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[Hari Iyer]

The third measurement, of making a test box and fitting the driver in it, and making an impedance of driver-with-test-box, is an additional headache and expense, just for Vas. It's a pain, and I am lazy. But without a reasonable idea of Vas, you can't arrive at the box size.

With foreign drivers I use the Vas given in their datasheet, so I avoid making a test box and doing this extra round of measurement. All other measurements must be done anyway.

With Indian drivers, that option is not there. The box must be made and the extra pain must be taken. I'd done it for the first Asawari -- those drivers were the 4-Ohm first cousins of this MK16i. If I choose the Miami again, I'll have to do that again.

But I am sure xo design will be simpler with this driver. The Peerless HDS driver or the Dayton RS driver will have huge cone breakup challenges which will make the xo difficult.

Why dont' you use the "Added Mass" method to calculate the Vas of the driver. Its more accurate than the "Known Volume" method. Now a days you get precision weight measurement scale for as low as Rs.350/- at Amazon. I have always used this method to measure the Vas and can say that i am atleast 95% accurate.

I've tried that. It's very hard to get it accurate. You need to keep a mass on the cone but it must stick to the cone, not vibrate independently. If I stick something to a cone properly, it will be with super-glue, which will damage the driver. I tried BluTack, but it doesn't stick the weight well.

You can use a higher weight to prevent vibration of the cone. I have some time used weight as high as 50 grams added to the cone. I usually do not add the mass to the dust cap. I have used ceramic bowls slightly moistened with water to grip it to cone and keep them at the center of the driver cone. By looking at the impedance curve you will be able to make out if the cone vibrated during the measurement. Any resonance above the free air resonance means that the mass vibrated during measurement. You can try this and let us know your findings. A weight like a ceramic bowl is even along the circumference and is evenly distributed across the driver cone and gives a very smooth impedance curve imo. Will try and post some measurement with this method if you wish.

 

[venki7744]

One thing I use is to stick multiple 5 Rs coins using double side tape on to the cone/diaphragm. This keeps the mass stuck to the cone while measuring with low power (like WT2). However you would run into issues if the cone is paper as the double sided tape might peel part of the paper when removing. Alternatively you could try using play dough (make sure that you store this in dry condition otherwise it would stick to everything).

Cheers
Venki

 

[tcpip]

Ya, these are interesting. The idea of the ring on the dust cap is cool. For the M16ki, we can probably get by with just double sided tape, because the cone is Kevlar, it won't tear when I peel off the tape.

Maybe I should stop complaining and give it a shot.

Shuvam

 

[jmascreen]

But I am sure xo design will be simpler with this driver. The Peerless HDS driver or the Dayton RS driver will have huge cone breakup challenges which will make the xo difficult.

Off topic question - is the highlighted issue could cause MID Range Shout? or else what are the known symptoms of MID Range shout?

 

[tcpip]

Yes, cone breakup of these drivers will add to midrange "shout". Very well put.

Conversely, if this breakup is tamed thoroughly, and the xo does a good job with even response, then the entire sound will be clean warm, and soft.

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[keith_correa]

For the M16ki, we can probably get by with just double sided tape, because the cone is Kevlar, it won't tear when I peel off the tape.

Just make sure you stick and peel off the tape multiple times on the back of your palm [before you have washed them] so that the oils from your skin get on the tape and make the stickiness a lot less sticky - peeling off a full strength double sided tape from a driver and finding that a part of the driver cone is peeling off with it is what my nightmares are made of. Some of the double side tapes are super powerful in their adherence. Be careful please.

 

[jmascreen]

By any chance you worked with M13NH drivers?

Yes, cone breakup of these drivers will add to midrange "shout". Very well put.

Conversely, if this breakup is tamed thoroughly, and the xo does a good job with even response, then the entire sound will be clean warm, and soft.

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[tcpip]

Just make sure you stick and peel off the tape multiple times on the back of your palm [before you have washed them] so that the oils from your skin get on the tape and make the stickiness a lot less sticky - peeling off a full strength double sided tape from a driver and finding that a part of the driver cone is peeling off with it is what my nightmares are made of. Some of the double side tapes are super powerful in their adherence. Be careful please.

Thanks. Will remember this.

By any chance you worked with M13NH drivers?

M13NH: you mean the Peerless India 5" Kevlar drivers? Yes, I think I've bought them, but haven't finished any speakers with them. One weird pair is in the works.

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[jmascreen]

Na its 5.25 paper cone from Peerless india, it has a sibbling of kelvar cone as well.

here is a link to this item Link

Can you please check, if there are any abnormality till 2200 Region?

M13NH: you mean the Peerless India 5" Kevlar drivers? Yes, I think I've bought them, but haven't finished any speakers with them. One weird pair is in the works.

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[tcpip]

Hi. I've been inactive on speaker building for almost a year now, but that's over and I'm back at work.

I never forgot this thread. I'll now design and build some simple 2-way designs with drivers available in India. I've changed my original goal a bit: I may use imported tweeters if they're available from diyaudiocart or theaudiocrafts. Just for variety.

So, I'm thinking of making two designs, both small 2-way standmount. One will be a TM, with a 6.5" Peerless India midbass unit and Peerless India TL26SG silk dome tweeter.

The other will be an MTM with 5.25" paper cone Peerless India midbass units and a smaller tweeter. For this one, I'm toying with the idea of using the Tympany XT25SC90 tweeter. It'll allow me to place the midbass drivers a bit closer to each other, and will will allow me a comfortable 4th order high-pass at about 2KHz for the crossover. The SB Acoustics SB29-RDCN is a superb tweeter with a small faceplate too, but I thought I'll keep costs low for this project when I'm working with these Peerless India midbass units with their variable quality.

I have yet to order the drivers. I'll have to measure the T/S parameters of the drivers, this being Peerless India.

The MTM will work horizontally too, for anyone thinking of a cheap and cheerful centre channel. And I don't know how much bass we can expect from these drivers in these configurations, but we'll live with what we get. (If I was building an MTM floorstander with 6.5" Peerless India drivers, I'd get more than enough bass for Indian homes -- I've seen it with the Asawaris.)

I'll keep you posted as I go.

 

[Hari Iyer]

Hi. I've been inactive on speaker building for almost a year now, but that's over and I'm back at work.

I never forgot this thread. I'll now design and build some simple 2-way designs with drivers available in India. I've changed my original goal a bit: I may use imported tweeters if they're available from diyaudiocart or theaudiocrafts. Just for variety.

So, I'm thinking of making two designs, both small 2-way standmount. One will be a TM, with a 6.5" Peerless India midbass unit and Peerless India TL26SG silk dome tweeter.

The other will be an MTM with 5.25" paper cone Peerless India midbass units and a smaller tweeter. For this one, I'm toying with the idea of using the Tympany XT25SC90 tweeter. It'll allow me to place the midbass drivers a bit closer to each other, and will will allow me a comfortable 4th order high-pass at about 2KHz for the crossover. The SB Acoustics SB29-RDCN is a superb tweeter with a small faceplate too, but I thought I'll keep costs low for this project when I'm working with these Peerless India midbass units with their variable quality.

I have yet to order the drivers. I'll have to measure the T/S parameters of the drivers, this being Peerless India.

The MTM will work horizontally too, for anyone thinking of a cheap and cheerful centre channel. And I don't know how much bass we can expect from these drivers in these configurations, but we'll live with what we get. (If I was building an MTM floorstander with 6.5" Peerless India drivers, I'd get more than enough bass for Indian homes -- I've seen it with the Asawaris.)

I'll keep you posted as I go.

The peerless paper cone has an Fs of around 70Hz, you can go for an Aperiodic loading to improve on low freq extension.

 

[tcpip]

The peerless paper cone has an Fs of around 70Hz, you can go for an Aperiodic loading to improve on low freq extension.

Yes I was afraid I'll have to think beyond bass reflex for some of these smaller drivers. I will at all costs, aim to keep the box size small. So, things like MLTL are out. (I remember Lynn Olson's famous Ariel speakers, slim MTM TL floorstanders with 5.25" Vifa poly cone midbass. I'm not building a floorstander here, come what may.)

 

[tcpip]

I was inclined to use this driver for the 5.25" MTM:

https://diyaudiocart.com/Raw-Driver...igh-fidelity-8-Ohm-5-1-4-inch-Woofer-M13NH-08

This one, paralleled, will give me a nominal 4 Ohm impedance. If the sensitivity spec can be trusted, I'll get excellent 95dB sensitivity after paralleling. The stated Fs spec is 60Hz, and as is typical with Peerless India spec sheets, there's no mention of Vas. So, those will need to be measured to let me figure out box dimensions and alignment.

An alternate driver is this one:

https://diyaudiocart.com/Raw-Driver...High-fidelity-8-Ohm-5-1-4-inch-Woofer-M13GH-8

which gives me a slightly lower Fs (useful) and 3dB lower sensitivity (which I can live with); it's just that I find these truncated frames irritating to work with.

For the 6.5" TM, I was thinking of

https://diyaudiocart.com/Raw-Drivers/Woofer/Peerless-6.5-Inch-Kevlar-Woofer-M16KI

but it has huge Vas (54 litres!) and the irritating truncated frame. And then there's this one, which seems simpler to work with:

https://diyaudiocart.com/Raw-Driver...d-High-fidelity-8-Ohm-6.5-inch-Woofer-S16NI-8

Of course, who knows what the Vas will be.

Am still freezing on the specific models.