Speakers

[Pete Maddex]

Hi Chaps

Knocked these up just for a laugh, I bought the drivers and crossovers secondhand and made the cabinets from 12mm ply.

Speaker by Pete Maddex, on Flickr

Internals, note the brace and deadsheet, I wanted the cabinet to be as stiff as possible and they are.

Glue up by Pete Maddex, on Flickr

Crossover on the back its insulated from the deadsheet with some plastic from a 2L lemonade bottle, and holes cut out of the foil where the screws go through.

Crossover by Pete Maddex, on Flickr

Lashed together to see what they sounded like.

Speaker and Nait 1 by Pete Maddex, on Flickr

Sprayed satin black.

Black holes by Pete Maddex, on Flickr

They sound rather nice, I have tried them with my amp in the kitchen and a Class D digital amp using B&O modules.
I need to get them connected to my main amps but that means moving furniture and its a bit hot.

Pete

 

[Planeiron]

They look great. Wish I had the electronics skills to do this. Photos actually give the impression of the music playing!

 

[Sheffield Tony]

Hi Pete - how big are they ? I see they are a ported design; do you design the box / porting yourself ? It has always looked a bit of a black art to me !

 

[Cabinetman]

I’ve come across that type of insulation before but haven’t heard it called Deadsheet, presumably because that’s what it does? Is it the same stuff as is used in attic conversions? Ian

 

[Pete Maddex]

Hi Pete - how big are they ? I see they are a ported design; do you design the box / porting yourself ? It has always looked a bit of a black art to me !

Hi Tony
They are 250x200x180mm the front is 250x200mm. I was advised by the seller to tune the port to 50Hz so I entered the cabinet sizes and port diameter in to an on line port calculator which gave me the port length.

Pete

 

[Pete Maddex]

I’ve come across that type of insulation before but haven’t heard it called Deadsheet, presumably because that’s what it does? Is it the same stuff as is used in attic conversions? Ian

It’s usually used in cars as sound proofing it’s made from a tar like substance and aluminium foil.

Pete

 

[Pete Maddex]

They look great. Wish I had the electronics skills to do this. Photos actually give the impression of the music playing!

I am doing a 365 where I post a photo a day for a year and have chosen a Lensbaby sweet 35mm lens which gives you a sweet spot of focus which you can move around the frame and control the size.

Pete

 

[fuse]

Thats a bit more intentional than a laugh!
Very nice

 

[Woodbloke]

I've packed my Monitor Audio speakers and stands in the loft as they took up too much room - Rob

 

[Sheffield Tony]

Hi Tony
They are 250x200x180mm the front is 250x200mm. I was advised by the seller to tune the port to 50Hz so I entered the cabinet sizes and port diameter in to an on line port calculator which gave me the port length.

Pete

Ahh. Online calculators. That's useful. I am enough of a dinosaur that when I wanted to do this, there were no online calculators. In fact there was no "online" at all yet !

 

[Cabinetman]

I've packed my Monitor Audio speakers and stands in the loft as they took up too much room - Rob

Yes my Monitors went to my son, 4’ high and roughly 12 x 15 on the top, most impressive to listen to but covered in white Formica they were “of a period” shall we say. A copy of Cambridge R50’s I built back in 1976.
Ian

 

[AJB Temple]

This is a trip down memory lane. Years ago I built a pair of quite big speakers from some Hi-Fi magazine plans. Ported. Woofer mid and treble and a point to point wired fairly basic crossover. They served me very well until I got a bit more flush. I don't recall being able to buy sound deadening board at the time, but the internals had a rudimentary bracing arrangement. At the time there was a big thing about isolating the cabinets from the floor using adjustable pointy legs.

 

[Cabinetman]

This is a trip down memory lane. Years ago I built a pair of quite big speakers from some Hi-Fi magazine plans. Ported. Woofer mid and treble and a point to point wired fairly basic crossover. They served me very well until I got a bit more flush. I don't recall being able to buy sound deadening board at the time, but the internals had a rudimentary bracing arrangement. At the time there was a big thing about isolating the cabinets from the floor using adjustable pointy legs.

Yes these had those three plus a super tweeter all kef speakers, big port and the insides of the whole thing was covered in car underseal- dreadful stuff till it dried. Then the interior spaces were filled with a blue wool, special stuff that I can’t recall the name of.
But no pointy legs, they had a base made from 2x3 softwood.
Ian

 

[Sheffield Tony]

I had always assumed that the high price tag of decent speakers in part reflected quite a lot of work with signal generators, microphones etc to refine on what the theory suggests ? Or maybe that's what they'd like us to think.

I'm more of an electronics type. I did design a couple of active crossovers, and even there making sure the amplitude and phase behaved smoothly through the crossover frequency range took a bit of thought and maths.

 

[Eric the Viking]

Back in the late 1970s I bought a pair of Monitor Audio MA7s. I still have them, sort-of.

The first mod was to get rid of the nasty back-to-back electrolytics in the crossovers, replaced with a forest of polyester caps.

Then the woofer went open-circuit on one side. Replaced both with Audax drivers.

Then one tweeter went. Also replaced with Audax, and adaptor plates, as their mountings were a bit different.

They then sounded a bit harsh at the lower end. Out of idle curiosity I wondered about the bass ports. They're the then-usual toilet rolls, glued into the baffle, with a counterbored hole, tubes seated about 1/4" back from the front surface of the chipboard.

On the basis I had nothing to lose, I decided to put a roundover on the port. A 1/4" Trend cutter was handy, so I used that. Added a bit of black paint, and you'd never know the roundover wasn't original.

Quite a transformation, for the better! They sound a lot smoother now and the apparent 'roughness' has gone.

These days they're scratched up and look like junk (I didn't paint the aluminium rings for the tweeters - really ought to!), but that's OK. Their main role in life is amplifying the TV for rare spells of movie watching.

I'm only mentioning this because I was surprised what a difference the roundovers made. Amusingly, my LS 3/7s also have caerdboard tube ports, but they're glued flush with the front of the baffles - there's no shoulder. They seem to work fine, and anyway I'm not messing with a BBC design (would be like removing the felt from the LS 3/5As!). I'm still not convinced that I'm not fooling myself (hearing going these days, in any case), but the principle of having a 'bell' is sound.

Monitor Audio long ago went seriously 'upmarket'. I don't think my original MA7s were anything like as good as the current range, and they weren't expensive either, but I like what I have now. The boxes, terminals and crossover inductors are all original! ;-)

[Photos to follow if someone really (REALLY!) wants to see them, but 'old and tatty' is being kind.]

 

[Pete Maddex]

I have good results from reducing refraction from sharp edges on cabinets and grills, I have felt diffusers round the recessed mid and tweeters which sharpens the image as does chamfering the grill edges.

Pete

 

[Eric the Viking]

There's a trick in use, which works really well, and with bookshelf-sized speakers particularly: if going for an equilateral triangle setup, arrange the speakers so that the tweeter axes cross over about 8" to 1ft in front of the listener's nose. Don't aim for where their ears will be!

Thus, as the listener moves left or right, they also move more on-axis to the speaker that's furthest away. This is subtle, but it stabilizes the stereo image substantially.

It works well with LS3/5As and my "Monitor Audio" units (which are a little bigger), and to a lesser extent with big speakers, too. Obviously you get best results with something recorded on a coincident stereo pair in the first place (e.g. most orchestral music, old-style radio drama etc.). Muilti-mic pop/rock won't be quite as good, but it should still help.

It also helps to keep the tweeters as close to 'ear height off the floor' as possible. Where I worked, it was common to find speakers mounted upside down in some studios and control vans with limited space. Obviously the further away the speakers are, the less this matters.

 

[SteveMP]

I’ve come across that type of insulation before but haven’t heard it called Deadsheet, presumably because that’s what it does? Is it the same stuff as is used in attic conversions? Ian

In the US i have used a similar product called Dynamat.

 

[SteveMP]

These look great! One of my first jobs out of school was installing car audio and security systems in cars, (and car phones i guess thats how old i am) custom speaker enclosures, fiberglass door pods for separates, bandpass boxes for trunk/boot etc. i kind of miss those days.

 

[SteveMP]

Ahh. Online calculators. That's useful. I am enough of a dinosaur that when I wanted to do this, there were no online calculators. In fact there was no "online" at all yet !

Back when i worked in an audio shop we used a DOS program (before internet) called Blaubox , made by German company Blaupunkt. You had to manually enter all of the Thiell & Small parameters of the speakers and it would calculate optimal internal box volume for sealed and ported boxes and port size etc, you could tweak some things as needed. You could save sets of parameters and name them by speaker. It was such a primitive computer program but it was really the best thing out there for most of the 1990s

 

[AJB Temple]

There's a trick in use, which works really well, and with bookshelf-sized speakers particularly: if going for an equilateral triangle setup, arrange the speakers so that the tweeter axes cross over about 8" to 1ft in front of the listener's nose. Don't aim for where their ears will be!

Thus, as the listener moves left or right, they also move more on-axis to the speaker that's furthest away. This is subtle, but it stabilizes the stereo image substantially.

It works well with LS3/5As and my "Monitor Audio" units (which are a little bigger), and to a lesser extent with big speakers, too. Obviously you get best results with something recorded on a coincident stereo pair in the first place (e.g. most orchestral music, old-style radio drama etc.). Muilti-mic pop/rock won't be quite as good, but it should still help.

It also helps to keep the tweeters as close to 'ear height off the floor' as possible. Where I worked, it was common to find speakers mounted upside down in some studios and control vans with limited space. Obviously the further away the speakers are, the less this matters.

Interesting. I am an ignoramus on set up. These days we have among other things a pair of B&O Daleks BeoLab 5), which have big woofers in the base and weigh a ton. Active. Quite old now, but still good. They came with a kind of microphone I suppose, with which you set up the speakers to the room dynamics and listener seating positions. Makes a surprising difference but no idea how it works.

 

[Pete Maddex]

There's a trick in use, which works really well, and with bookshelf-sized speakers particularly: if going for an equilateral triangle setup, arrange the speakers so that the tweeter axes cross over about 8" to 1ft in front of the listener's nose. Don't aim for where their ears will be!

Thus, as the listener moves left or right, they also move more on-axis to the speaker that's furthest away. This is subtle, but it stabilizes the stereo image substantially.

It works well with LS3/5As and my "Monitor Audio" units (which are a little bigger), and to a lesser extent with big speakers, too. Obviously you get best results with something recorded on a coincident stereo pair in the first place (e.g. most orchestral music, old-style radio drama etc.). Muilti-mic pop/rock won't be quite as good, but it should still help.

It also helps to keep the tweeters as close to 'ear height off the floor' as possible. Where I worked, it was common to find speakers mounted upside down in some studios and control vans with limited space. Obviously the further away the speakers are, the less this matters.

I have Shahinian Arcs which are semi omnidirectional speakers so they are not to fussy about placement.

Pete

 

[Raymedullary]

Interesting post. I built some Kef Concertos back in the early 80's T27 B110 and B139 drivers. I upgraded the crossover like most people from the DN12. A lovely big warm sound. Unfortunately too physically big though so I reworked the design by arranging the drivers vertically and making a slightly smaller closed box instead of the ported concerto design. Still good, tighter bass, imaging pretty good.
I was moving around a lot then so I sold the drivers for decent money. I currently use a pair of Wharfdale Evo 4.2 with a sub which I like a lot. I tried some modern Kefs (Q1) recently but was disappointed to find that they have lost their signature sound and become over accurate verging on harsh. Amazed at LS3 prices now!