MTM TL speaker project questions

[KenM10759]

I've got a pair of 1988-1991 Hafler 300 floor-standing speakers that I picked up cheap. They're in excellent condition and don't sound horrible, but at volume it seems the 4 old Carbonneau 6-1/2" woofers have a lot of distortion. The 2 Vifa 1-1/8" tweeters aren't really as clear as they should be, perhaps a case of ferro fluid needing a change/charge.

I'm thinking this is a golden opportunity to learn how to upgrade a speaker with a really solid cabinet. The oak veneer over MDF seems really quite inert because inside there's essentially a nearly full length "brace" between the sides of the cabinet, creating a transmission line configuration.

I'm good at calculating the internal volume of something like this, but need to learn how to use that information to come up with 4 appropriate drivers, a pair of tweeters, and a properly engineered crossover network. Using these well built cabinets would save me a fair bit of time and cost, plus they look good (and a pretty heavy.)

When I recently did something similar with an old Miller & Kreisel V-90 sub, I got help from a couple of key people here and it turned out to be a better sub than I ever imagined. (Spanks my SVS SB2000.)

I don't want to impose in the same way, asking that much help. The help I'd want for this is what design tools should I get and learn? I have only Windows 10 PC's, patience, and a willingness to learn.

Thanks in advance!

 

[Swerd]

The first thing you must do is measure how those Carbonneau 6-1/2" woofers behave. You will need to know their Thiele/Small (T/S) parameters, especially their resonance frequency (Fs), total Q factor (Qts), and their equivalent volume (Vas). You also should learn their loudness vs. frequency, and impedance vs. frequency curves.

Once you know this info, you'll be able to decide what kind of cabinet (sealed, ported, or transmission line) will work best for these woofers. You'll also learn the maximum frequency at which these woofers can perform well without going into break up.

To do this, you'll need a tool like this: https://www.parts-express.com/dayton-audio-dats-v2-computer-based-audio-component-test-system--390-806.

This is only the first step. You'll also need cabinet design and crossover design software, or access to someone else who has these and knows how to use them. Once you figure out the T/S parameters of these woofers, I suggest contacting TLS Guy. He can easily design a sealed or ported cabinet them, and he can tell you if they are suitable for a transmission line cabinet. He may also tell you these woofers are junk and a waste of time & effort.

 

[KenM10759]

Thanks for the reply, but to be clear I don't want to keep the old woofers, it's only the cabinets I wish to use.

 

[Swerd]

Thanks for the reply, but to be clear I don't want to keep the old woofers, it's only the cabinets I wish to use.

To find woofers suitable for an existing cabinet, backwards engineering so to speak, is difficult in the sense that it requires a lot of trial & error as well as luck. I know of no systematic way to go about it.

If you can find 6½" woofers with T/S parameters similar to those Carbonneau's, their bass response should work ok in those cabinets. But they might not work well with those tweeters.

 

[KenM10759]

I haven't been able to dig up any information on the Carbonneau woofers, barely any history of the company itself seems to exist. I do wish I could just replace all the drivers and crossover network with new stuff, but don't know how to go about it other than to copy the crossover components that might have values marking. I should be able to find something on the Vifa tweeters, though it seems Tymphany/Peerless doesn't seem to make a direct replacement because of its recessed mount.

 

[TLS Guy]

That really is an impossible project. To find drivers that have the correct Vas, for the pipe volume and correct Qts and Fs for that pipe length will be impossible.

If you want an MTM TL your best bet is to start from scratch with a totally new design. In addition I have no idea what type of line we are talking about. What is he length, type if taper and volume?

OK, I found the manual. There is a diagram. That is a bogus design, that makes no sense. It is not a TL, it is a reflex enclosure with a sloping brace. That could not possibly work as a pipe. You are wasting your time with that one.

If you want a TL then start from scratch.

 

[KenM10759]

I don't necessarily want a transmission line speaker. I just want to replace the drivers and perhaps crossover network components in the speakers now with something as good or better than what these are now, because they're 30 years old and something isn't right. I don't expect them to be a world-class speaker, but if I can get them to sound better, I'm willing to work at it.

BTW, these did get some very good reviews when they came out. I remember reading about them, and heard them when I bought the "little brother" Hafler 200's. My niece still uses those. I just want to know what software I could by or books I could read that would help me with this project. Thank you!

 

[TLS Guy]

I don't necessarily want a transmission line speaker. I just want to replace the drivers and perhaps crossover network components in the speakers now with something as good or better than what these are now, because they're 30 years old and something isn't right. I don't expect them to be a world-class speaker, but if I can get them to sound better, I'm willing to work at it.

BTW, these did get some very good reviews when they came out. I remember reading about them, and heard them when I bought the "little brother" Hafler 200's. My niece still uses those. I just want to know what software I could by or books I could read that would help me with this project. Thank you!

So, even if we go with a tuned enclosure we still have a big problem. A sub is one thing a speaker like this another matter. With vented cabinets there is little room for enclosure size error. The cross over is very difficult and the software just gets you close as rule, and then if you are lucky. So you need not only software, but measuring equipment and then you have to know what to do to correct the problems. Even then you often make corrections based on extended listening tests.

So the most effective from a price point is to invest in the combination package of Bass Box Pro/X-Over Pro. You will need the Dayton Woofer tester and their omni mic program at the least.

Best deal for the design software is Amazon. $139.95

Woofer Tester. $99.88

Omni Mic measuring system. $298.00

So a bill of $540 for the bare basics.

However once you have it you can design as many speakers as you want. If the bug has caught you, and in your case, I think it may have it is worth the investment.

With that much on the line and the time involved, you are much better off doing you design from the ground up.

If you want a TL, then I can help you, as I have software I got from George Aspergerer.

Just to make you aware I'm travelling to our Eagan Home today and my wife and I fly to Engalnd tomorrow, for my mother's funeral. She died Christmas Eve.

When I get back, I have to start packing this place up in earnest, to get the place cleared for the New owners April 30.

We broke ground a couple of days ago for a new home in Eagan. So we are leaving lakes country and downsizing to one home. It is ADA and handy and designed to the max for nursing home prevention. I'm excited about the project. It is an ICF home and I have designed it to be comfortable, withstand very high winds, and be highly energy efficient. I hope I'm not to far to the bleeding edge, but we will see.

So this will be a very busy year I think, with not much time for doodling with other people's projects.

 

[KenM10759]

Thank you for the reply, TLS Guy!

I have a UMIK-1, a PC and could download REW. Would that be of any use?

I was looking at that very same software package, so will definitely get that. I do understand that the cabinets really aren't a true transmission line type. They are however, very well-built and I'd like to use them if at all possible. If I don't, there's $200 worth of good-looking but "pedestrian level" performing speakers in our guest room.

Yeah the bug has bit me and I do want to learn as much as I can, though I want a quality education and not be creating "white van" tire speakers. I have limited woodworking skills and equipment, though my son has some nicer tools and better skills.

I'll look into the woofer tester but that Omni mic seems pricey. If that's what it really takes, I'll save up and get one.

PS - Very sorry for your loss, travel safe.

 

[Swerd]

Thanks TLS Guy for the link to the manual of those Hafler 300 speakers. In it, I noticed that Hafler was owned by Rockford when those speakers were made. Hafler originally was a highly regarded maker of rather inexpensive solid state amplifiers in the 70s. I don't believe that Hafler, as a privately owned company, ever made speakers. At a later time, the company was bought by Rockford, a company better known for audio in cars. Apparently Rockford also owned Carbonneau speakers. New Hafler amps briefly appeared, but the name soon disappeared. Old Hafler amps from the days before Rockford's ownership are excellent values on the used market.

So you need not only software, but measuring equipment and then you have to know what to do to correct the problems. Even then you often make corrections based on extended listening tests.

TLS Guy, thanks for your comments. We are on the same page. I'm sorry to hear about your mother's passing – my condolences. Good luck with your travel to England.

In addition to the gear that TLS Guy recommended, I also suggest this book, Speaker Building 201 by Ray Alden. It's sold by Parts Express, Madisound, and Amazon. The first 3 or 4 chapters will give you a good understanding on the thought process behind designing sealed or ported cabinets. It doesn't deal with transmission lines. Alden explains how the design process depends on knowing a woofer's T/S parameters, much better than I have here. I wouldn't bother trying to run the numbers myself because the design software, such as Bass Box, is much more reliable for that. If you do this type of designing enough, you'll eventually learn by trial & error, but I think it's better to learn quickly why things are done a certain way. This book is good for that.

 

[KenM10759]

Book is on order. Thanks!

 

[Irvrobinson]

When I get back, I have to start packing this place up in earnest, to get the place cleared for the New owners April 30.

Taking apart and packing your audio system must be a record-breaking pain in the butt.

 

[Alex2507]

my wife and I fly to Engalnd tomorrow, for my mother's funeral.

I'm very sorry to be reading that. Sometimes it seems like life has more to do with loss than living and I'm sorry for yours.

 

[TLS Guy]

I'm very sorry to be reading that. Sometimes it seems like life has more to do with loss than living and I'm sorry for yours.

Thank you for your comments. My mother had a very good life, and lived it to the full. She was 98 and only in very bad shape for the last 7 weeks, when she had to go to a nursing home. She loved on the same house since 1953. Death comes to us all and we meet our end in various ways. I did visit her at the end of November/beginning
December. I know she recognized me when I first arrived, but I'm not certain after that. By all accounts her death was peaceful.

The Old Parsonage Frindsbury.

The garden which was her pride and joy.

You can see the estuary of the River Medway in the distance.

My parents at their 60th wedding anniversary 2004

My mother was a WW II veteran. She was the personal secretary to the Brigadier General of the Royal Engineers. My father was a Captain in the royal Engineers and that was how they met.

They were married the day before D-Day. My mother knew but my Father did not. She kept the secret.

My father dies six years ago next week.

 

[KenM10759]

Thank you for sharing, and may peace be with you and your family at this difficult time. I have also buried both my parents (before I hit 56, now 59) and it was tough, but it's the way things really should come to pass as no parent should ever have to bury their child. Mine buried 2 of 6.

 

[TLS Guy]

Thank you for the reply, TLS Guy!

I have a UMIK-1, a PC and could download REW. Would that be of any use?

I was looking at that very same software package, so will definitely get that. I do understand that the cabinets really aren't a true transmission line type. They are however, very well-built and I'd like to use them if at all possible. If I don't, there's $200 worth of good-looking but "pedestrian level" performing speakers in our guest room.

Yeah the bug has bit me and I do want to learn as much as I can, though I want a quality education and not be creating "white van" tire speakers. I have limited woodworking skills and equipment, though my son has some nicer tools and better skills.

I'll look into the woofer tester but that Omni mic seems pricey. If that's what it really takes, I'll save up and get one.

PS - Very sorry for your loss, travel safe.

REW is not what you need. You need Omni mic plus the discs and computer software.

 

[KenM10759]

The MiniDSP UMIK-1 (with its device-specific calibration file) does appear to be very much the same as an Omni Mic, and even comes with what appears to be the same little tripod and mount. It was recommended to be used with Dirac Live (which I also have) and does measure seemingly accurate.

I'll get the software, but would like to know what makes the two mics so different from each other. I can buy the Omni mic if need be, but it seems to have the same USB compatibility and range as the UMIK-1.

 

[BoredSysAdmin]

We broke ground a couple of days ago for a new home in Eagan. So we are leaving lakes country and downsizing to one home. .

With your main speakers which are basically built for that specific room, I guess time for new ones?
Sorry for off-topic KenM

 

[TLS Guy]

With your main speakers which are basically built for that specific room, I guess time for new ones?
Sorry for off-topic KenM

No they will revoice for the new room just fine, if needs be. The room has similar ratios, but is bigger. It will be a nine seat rather then five seat room and 9" rather than 8".

My guess is that the speakers will perform even better in the new space. They have enormous power in reserve. I'm not in the least concerned about moving them to the new space.

 

[TLS Guy]

The MiniDSP UMIK-1 (with its device-specific calibration file) does appear to be very much the same as an Omni Mic, and even comes with what appears to be the same little tripod and mount. It was recommended to be used with Dirac Live (which I also have) and does measure seemingly accurate.

I'll get the software, but would like to know what makes the two mics so different from each other. I can buy the Omni mic if need be, but it seems to have the same USB compatibility and range as the UMIK-1.

I can't answer that question. However it does state that the mic that comes with it is calibrated for that program.