Designing a 2-way bookshelf speaker

[tcpip]

Went through the capacitors and inductors. All the inductors are as ordered. Out of the capacitors, I'd ordered six 15uF, but I've received only three. And I'd ordered two 10uF which haven't been sent. Will wait for a response from TheAudioCrafts. So, crossover building is now again on hold till I get the missing parts.

The inductors are very nice looking, well finished. I'll aim to use these instead of hand-wound custom made coils in future. And the caps: the Audiophiler caps are nice, MKT, but not as well finished as the Jantzen Cross-caps I ordered for another project. I'll still use Audiophiler to save costs -- I don't think the quality issue is significant.

I've also ordered some material for enclosure wall damping and filling -- from Amazon and diyaudioparts. I've ordered their polyfill fibre for filling the enclosure. For wall damping, I've ordered some two or three different things from Amazon -- let's see how they turn out:

• MMT Acoustix sound damping pad
• MMT Acoustix Turbo soundproofing acoustic foam panel
• Coromose 10mm insulation mat
• Total Home 152x90cm closed cell foam sheet

I don't know how each of these will work out. I have the least expectation from the last one -- it seems thin and light in the photos. While searching for these things on Amazon, I discovered that this company, MMT Acoustix, is big-time into sound damping panels, though they are not aware of a customer segment called DIY speaker builders. Can't blame them: this market in India is too price sensitive, and the MMT products are fairly expensive. Let's see how they work out.

In the past, I've actually built speakers without any damping on the inner walls -- other than the Asawari 1, built in 2006. For all the speakers since then, I've just used thick MDF sheets for the walls and braced them so well that I've not felt the need for any additional damping. This time, I've decided to experiment with these materials just to get a feel for them.

If you have any experience with any of these things, please share.

I'm also trying to up my crossover assembly game a bit -- I am buying terminal strips: one row and two-row. The two-row ones are good to connect the wires from the drivers to the crossover board -- no need to solder them directly, just use a screwdriver. And the one-row strip will, I hope, be really useful for the ground connection. In every parallel crossover (and to a lesser extent in a series crossover too), there are a million wires and components which connect to the ground connection. One wire comes in from the -ve binding post into the crossover board. And then there are all the shunt capacitors and inductors whose ground terminals connect to this point. And then there are the -ve terminals from all the speaker drivers. It makes for a really crazy pile of wires, all wrapped tightly and soldered together, like a royal mess. That's how I've built the crossovers till now, and didn't like them. I'm hoping these barrier strips will clean things up a lot. Stay tuned.

It's amazing how many of these DIY things are available on Amazon India.

 

[suraj]

I recently purchased some butyl rubber damping sheets from ths Indian company called Dampmat.900Rs for a 4sqft sheets.I am yet to apply it to my speaker build,so cannot comment on its performance.Its sticky rubber and not foam,so I expect it to be much better.It will have a layer of MMT's foam over it.

 

[Hari Iyer]

tcpip, how do you judge the right amount of stuffing. Is it by listening or some other method?

 

[keith_correa]

tcpip, how do you judge the right amount of stuffing. Is it by listening or some other method?

I'm not tcpip but maybe this could be useful:

From Altec - 1974

The normal method to check speaker damping is simple, but is easiest if you start out with too little fiberglass. We recommend the battery test method to check for damping. Attach a short length of speaker wire to the loudspeaker terminals in the normal manner, and bring the loose end around front – where you can easily listen to the loudspeaker sound while testing. Hold one of the speaker leads to either end of a standard 1.5 volt flashlight battery. Then touch the second lead to the other end of the battery and release. A properly damped loudspeaker will reproduce a clean “click” as contact is made and released.

The underdamped speaker will reproduce the battery contact as a “whomp” sound. Fiberglass may be added in a loose manner to the enclosure until the proper “click” is obtained, and then stapled into place according to above practices relating to the specific type of enclosure.

The overdamped speaker is more difficult to observe. It is a matter of degrees that becomes familiar with one or two experiments. Thus, the recommendation to start tests with too little, build up, and then go back down as required.

 

[Hari Iyer]

I'm not tcpip but maybe this could be useful:

From Altec - 1974

Thanks Keith for the details. Though this method is nice it will be tedious to do this way imo as you will require to remove the driver each time.

When I started my journey of building TL speakers 15 years ago, I has asked this question to Martin King the TL guru. He had replied mentioning to put my ears at the terminus and listen for a rumble at the terminus playing pink noise.

Another method was to measure the speaker impedance while adding / removing stuffing. A properly stuffed TL line will show impedance around 50% less than the free air impedance at resonance

For ported enclosures the unstuffed line for a properly designed box shows two impedance peak - one of the driver and other of the box with both the peaks having equal amplitude. By adding stuffing to the box these peaks gets reduced and mistuned which will drastically affect bass response. That's one of the reason why ported enclosure are not stuffed. I would rather just line the enclose back , top and bottom wall with felt and not stuff at all if my box is properly tuned. This can be done by measuring impedance when you do this. The key is to know the impedance peak of the unstuffed box and stuff/ damp accordingly.

 

[somakmaitra]

Nice to see you back in DIY have you looked at the SB Acoustics satori range recently. A design from you will help us greatly .
Regards
Somak

 

[tcpip]

One small exploration paid off. I now have one very affordable supplier of high quality name plates for my speakers.

These are 20mm x 70mm, brushed stainless steel, laser etched. I paid some USD 11 or 12 for 16 nameplates. Their minimum quantity is 10, and they will print 10 different texts on the 10 pieces. The vendor is on AliExpress. Very good customer service and quick turnaround, but takes some 3 weeks for the packet to reach.

 

[tcpip]

Nice to see you back in DIY have you looked at the SB Acoustics Satori range recently. A design from you will help us greatly .

In fact, I'm quite curious about the entire SB Acoustics range, and the fact that we have a retailer in India is really nice. I'm quite impressed even with their non-Satori range. The Satori ones are really sexy. I intend to build a pair of TM standmounts with the Satori 7.5" midbass and a good Satori tweeter -- maybe their TW29R. This is one of the most affordable Satori tweeters with a super sexy two-colour faceplate which is guaranteed to make it sound awesome. (As my speaker guru says, "If your speakers look great, they are guaranteed to sound superb." )

The 7.5" is an unusual size for a midbass, because almost every other brand seems to jump from 6.5" for a 2-way to 8" for a pure woofer. It'll be nice to stretch beyond the usual size and still try a 2-way. I'm certain to embark on this design, with a bit of an unusual, non-rectangular front shape and bevelled edges like those Avalon speakers, cut out of a thick 4" front baffle. I'm thinking of making the front baffle with 1" of MDF and 3" of Baltic birch plywood, and then just polishing the naked ply, to highlight the stripes of the edges of the sheets as an aesthetic high point. Let's see how it turns out. I'll be sharing the design details online, as always. I didn't want to talk about it till now because it's best to talk about things once you actually have something to report, but since you asked...

On the tweeter front, left to myself, I don't feel the need to go beyond the Peerless HDS tweeter for pretty much anything. It's close to flawless -- it can be crossed over very low (even 1200Hz 4th order), flat response curve, very low distortion throughout its range, has no cone breakup resonances which most metal domes have, is well built and reasonably priced. I've used it for the Darbari. For an almost as good tweeter with a slightly lighter construction and a tighter budget, the famous Seas TDFC and metal-dome TBFC/G are my go-to tweeters. I've almost finished an MTM design which uses Dayton RS metal-cone midbass drivers with the TDFC tweeter at 1.5KHz, 6th order slopes, where the very high quality and low-crossover capability of this tweeter were very valuable.

Now, with the SB Acoustics range, maybe I'll use something like the RDAC, RDNC or RDC as my general-purpose tweeter. The RDAC and RDC will probably go as low as the Peerless HDS, and the RDNC will work for MTM or other configs where a smaller front plate is useful. The Satori TW29R is too rich for my blood usually -- it's too expensive. But with the Satori 7.5" midbass drivers, I thought I should splurge for a similarly expensive tweeter to keep it company. Am not sure there will be any audible quality drop if I use the Peerless HDS there.

tcpip, how do you judge the right amount of stuffing. Is it by listening or some other method?

I don't stuff a bass reflex box -- I just line the walls, as you have said. I am more worried about the duct length than the degree of stuffing, and I use the impedance measurement to see if the duct length is right. I try to get the twin peaks to roughly match the curve shown by Unibox, my box modelling software. And in any case, what you hear at the low end of the frequency range in your room is so little related with the theoretical behaviour of the box that I am not too fussy about a bit of misalignment.


On the matter of the building of the original standmounts -- I'm still waiting for some missing capacitors. Apparently they've cleared Customs and entered India now.

 

[somakmaitra]

In fact, I'm quite curious about the entire SB Acoustics range, and the fact that we have a retailer in India is really nice. I'm quite impressed even with their non-Satori range. The Satori ones are really sexy. I intend to build a pair of TM standmounts with the Satori 7.5" midbass and a good Satori tweeter -- maybe their TW29R. This is one of the most affordable Satori tweeters with a super sexy two-colour faceplate which is guaranteed to make it sound awesome. (As my speaker guru says, "If your speakers look great, they are guaranteed to sound superb." )

The 7.5" is an unusual size for a midbass, because almost every other brand seems to jump from 6.5" for a 2-way to 8" for a pure woofer. It'll be nice to stretch beyond the usual size and still try a 2-way. I'm certain to embark on this design, with a bit of an unusual, non-rectangular front shape and bevelled edges like those Avalon speakers, cut out of a thick 4" front baffle. I'm thinking of making the front baffle with 1" of MDF and 3" of Baltic birch plywood, and then just polishing the naked ply, to highlight the stripes of the edges of the sheets as an aesthetic high point. Let's see how it turns out. I'll be sharing the design details online, as always. I didn't want to talk about it till now because it's best to talk about things once you actually have something to report, but since you asked...

On the tweeter front, left to myself, I don't feel the need to go beyond the Peerless HDS tweeter for pretty much anything. It's close to flawless -- it can be crossed over very low (even 1200Hz 4th order), flat response curve, very low distortion throughout its range, has no cone breakup resonances which most metal domes have, is well built and reasonably priced. I've used it for the Darbari. For an almost as good tweeter with a slightly lighter construction and a tighter budget, the famous Seas TDFC and metal-dome TBFC/G are my go-to tweeters. I've almost finished an MTM design which uses Dayton RS metal-cone midbass drivers with the TDFC tweeter at 1.5KHz, 6th order slopes, where the very high quality and low-crossover capability of this tweeter were very valuable.

Now, with the SB Acoustics range, maybe I'll use something like the RDAC, RDNC or RDC as my general-purpose tweeter. The RDAC and RDC will probably go as low as the Peerless HDS, and the RDNC will work for MTM or other configs where a smaller front plate is useful. The Satori TW29R is too rich for my blood usually -- it's too expensive. But with the Satori 7.5" midbass drivers, I thought I should splurge for a similarly expensive tweeter to keep it company. Am not sure there will be any audible quality drop if I use the Peerless HDS there.


I don't stuff a bass reflex box -- I just line the walls, as you have said. I am more worried about the duct length than the degree of stuffing, and I use the impedance measurement to see if the duct length is right. I try to get the twin peaks to roughly match the curve shown by Unibox, my box modelling software. And in any case, what you hear at the low end of the frequency range in your room is so little related with the theoretical behaviour of the box that I am not too fussy about a bit of misalignment.


On the matter of the building of the original standmounts -- I'm still waiting for some missing capacitors. Apparently they've cleared Customs and entered India now.

Thanks Tarunda for your reply.
I am also following a few designs closely it includes a couple of Troels designs :-
SBA-741
SBA-761
There is one design which I am very intrigued, is a closed design but based on Satori 7.5"
SBA MW19

Instead of SATORI TW29RN Ring dome SB29RDC-C000-4 can be used but it a 4 ohms tweeter.

We require your help in such a design.
Regards
Somak

 

[tcpip]

This is very interesting. Will you please start a separate thread while I do some reading on all the links you've given? Your inputs also coincide with my current interests -- I was thinking of (I) a high-quality conventional 2-way TM standmount (hence the Satori explorations), and (ii) the importance of midranges and how to do good 3-ways. Completely different topics, but they are all in the broad area of the designs you've cited. So a separate thread may be good.

 

[somakmaitra]

This is very interesting. Will you please start a separate thread while I do some reading on all the links you've given? Your inputs also coincide with my current interests -- I was thinking of (I) a high-quality conventional 2-way TM standmount (hence the Satori explorations), and (ii) the importance of midranges and how to do good 3-ways. Completely different topics, but they are all in the broad area of the designs you've cited. So a separate thread may be good.

That will be really helpful from a DIY prospective.