what type of enclosure to use for 6.5 inch Bolton

[somakmaitra]

hi ,

I have two old BOLTON 6.5 inch 4 ohms woofers lying .I want to make a woofer enclosure using the two woofers in push-pull arrangement .i will use 24db/oct linkwitz crosssover and using lm3886
i have a problem as to what type of enclosure to use following the calculation of the T/S Parameters

the parameters of the woofers are :-
fs= 48hz

Qms 2.97
Qes 2.23
Qts 1.27

please suggeat what type of cabinet to use -sealed or vented ?

thanks,
somak

[aman]

hi,
You can use WINisd pro alpha to find out the best enclosure for ur speaker. Just feed the t/s parameters in the software and u would get the results.
hope it would help,
Aman

[tcpip]

Originally posted by somakmaitra
Qts 1.27

please suggeat what type of cabinet to use -sealed or vented ?

You have very little options with a driver with a Qts like that. It's not for no reason that Indian diyers keep hankering after imported drivers.

No box modelling software can help you when your driver Qts is higher than about 0.6. You have only two choices, AFAIK:

• Use those Boltons as mids in a three-way (they may work well as OB mids in a 3-way, for instance, if xo'd to the woofer at a high enough freq to side-step the peak due to their high Q)
• Use a sealed enclosure with those drivers, use active xo (which you seem to have decided to do already) and apply the LT to get the Qtc of the final box down to a manageable 0.7-0.8

I too have some Bolton 6.5" woofers, and they give me a Qts greater than 1. Given the low price of the drivers, one doesn't want to burn good money in active xo and top-end amps to fix their Qts problems, so chipamps and inexpensive LT is the only practical solution, I feel.

One word about those Boltons and LT. If you use LT, there will be a lot of excursion demands made on those drivers. Hence, using at least two drivers per box will be recommended, to allow them to share the bass load.

And one more point: do you know the Vas of the drivers? Without the Vas, you can't determine box size.

[aman]

hi tcpip
could u plz suggest any book available in India on DIYing speakers. I also went to world book fair in delhi but couldnt find any book relating this. I built speaker enclosures with the help of information available on the net but they dont sound good.There are two shops here that sell bolton speakers of all sizes(without t/s parameters)plz suggest me the way i can utilize them.
thanks
aman

[tcpip]

could u plz suggest any book available in India on DIYing speakers. I also went to world book fair in delhi but couldnt find any book relating this. I built speaker enclosures with the help of information available on the net but they dont sound good.There are two shops here that sell bolton speakers of all sizes(without t/s parameters)plz suggest me the way i can utilize them.

If you want to build speakers using Bolton drivers, you'll have to design them. This is not suitable for a beginner, as you appear to be.

If you want to build pre-designed speakers, I suggest that you look for a 2-way Vifa design built around the P17 drivers. These drivers are available from Corrson (www.corrson.com). They use Vifa tweeters, which too are available there. A friend made a pair of these, and they sounded wonderful. I recommended this design to another person who was a member of this forum, and he too made them. I believe he's from B'lore. He too reported that they sounded very good. Therefore, I strongly suggest that you look through my earlier posts on this forum to find out where I've recommended this Vifa design (designed by Marshall Leach and his students), and just build accordingly.

The Vifa drivers are expensive by Bolton standards, but they also sound far superior. The problem with Indian drivers is that there's no really adequate midbass drivers in the 6"-7" range, where most of the world's midbass drivers lie. You need some such drivers with adequate midrange and bass reproduction to be able to build good, simple, 2-way speakers with passive xo. Since they don't exist, a beginner is better off using these Vifas and then building the simple 2-way I've mentioned earlier.

The Peerless India tweeters are fairly adequate for beginner use, so in theory someone could design a decent, low-cost speaker using these tweeters. It's the midbass drivers where Indian options seem to run dry. I'm in the process of building a pair using the only Indian midbass drivers I could find: the Peerless India kevlar cone 6.5" drivers. When I finish, I'll write it up. However, I'm pretty sure I will not use those Kevlar drivers for subsequent projects... the Vifa P17s are better value for money, I feel.

As for books, you'll have to get yourself a copy of Vance Dickason's LSDC (LoudSpeaker Design Cookbook). Various people have various opinions about this book, but it's unlikely that there's anyone who has understood speaker design but has not read this book at all. Personally, I find the problems in the book very minor, and the useful content absolutely essential. I couldn't do without it.

You don't need Dickason to build pre-designed speakers, I feel, other than the sections discussing common issues about cabinet construction.

And I'm not too bothered about books being available or not available in India, because import of books is a totally hassle-free thing. Most large bookshops in Bombay, Delhi, B'lore, and elsewhere will import any book in print for you, for a small (less than 20%) premium, or sometimes none at all. Or else you can always order online and foot the (hefty) courier charges into India. From Jawaharlal Nehru's time, there has never been Customs Duty on books.

[aman]

hi tcpip
thanks for information. I have got a three way system of BPL built with MDF. Another 3-way system with passive xo i built using .75"MDF and locally available drivers. But i know that i dont have much knowledge and dont have equipments to measure t/s parameters of the drivers. I cant use/import costly drivers......lack of funds...
A few days back i bought 8' *4' MDF board.75 inch for building an 3-way passive system with 12" bolton woofer(2.7 cuft volume). But everybody says that they are good for nothing so i m confused what to do????
I know that i m a beginner but i dont wanna waste money and time in beginners project. I dont want ultimate system/sound .I just wanna use available drivers in their best form. Some of my friends have built enclosure using boltons and they are sounding good for me.But they have used pre built crossovers cheaply available in the market. But i want to built good system with the help of so many intelligent friends of the forum and i know they will help me.
any suggestions.......
regards Aman

[tcpip]

There are contradictory statements in your post.

If you are just interested in using available drivers, you will have to learn to design your own speakers. If you don't have any knowledge or equipment to even measure T/S parameters, you should opt for a pre-built design.

And when you go looking for pre-built designs, you'll find that there's nothing worth listening to based on Indian drivers. The reasons are basically simple: no good Indian midbass drivers, no consistency of T/S parameters in Indian drivers, poor QC of Indian drivers, and simply too small a DIY community in India who have the knowledge and patience to design things from scratch from these drivers.

Hence, either you teach yourself enough designing to create your own designs using these hard-to-work-with Bolton and Peerless drivers, or else you use Corrson's imported drivers to construct a pre-designed speaker.

I don't see any other way out for you. This is what I've learned in my own travels along these paths.

Some statements you've made which I find confusing:

• You say you don't want to waste time and money in beginner projects. AFAIK, only really knowledgeable designers can avoid wastage of time and money. Time, money, and knowledge are three mutually contradictory attributes. If you want to save one, you'll need to have the other two. Or else, pick up an inexpensive kit design and just build it.
• You want to work with cheap Bolton drivers, but you don't know how to design your own speakers... this seems contradictory. Either you do your own designs, or else you quietly use the drivers and components that other designers have used in their designs. Remember, cheap, ill-designed drivers like the Boltons are the most difficult to design good speakers with... they need the maximum corrections and compensations.
• You say you like the sound of pre-packaged xo's bought across the counter. In that case, why do you want to bother with "your own" designs? We all struggle to learn xo design because we don't like the sound of pre-built xo's.
• Last and most important: no one on this forum will help you unless you struggle to teach yourself the very difficult subject of speaker design. If you are struggling, and others can see your struggle, then they help you most patiently and cheerfully with the difficult bits. But if you want to "do your own design" without investing that huge amount of time and effort to learn what Dickason and others are trying to teach, then I am not sure you'll get much help from this forum. Everyone here will (very rightly) try to suggest that you pick up a pre-designed speaker and try to build it. That's the sanest advice for you at this stage, so please don't overreach at this stage... it will result in more waste of time and money.

Hope some of this helps somewhere.

[aman]

hi tcpip
Thanks for enlightenihg me ......This all is due to lack of knowledge.... I do wanna design my own speaker but dont have literature . I m sticking to bolton coz i have got two 12"bolts and two tweeters,a few 10" drivers and two 4" philips tweeters and a few 5.5"bpl dome midrange.
I know that imported drivers are miles ahead of indian drivers and any cheap imported driver can outperform a costly indian driver but a huge amount has to be paid for it......very difficult to get them.I searched everywhere in delhi but .........
Had i been in mumbai or banglore i would have bought good driver from there and kicked off cheap boltons but alas......
I have also built a three-way 24 db/octave LR active crossover and have three amplifiers symasym,P3A and an amplifier+preamp+equalizer purchased from enbee electronics in new delhi each is of 100 wrms per channel.
more suggestions invited
regards ,aman