Speekerz wot I maid

This design went through a number of versions. I have posted my final ideas in post 5 of this thread - https://www.audio-forums.com/as-rediect/showthread.php?t=18763


Well I said I would post a speaker design so here it is!

This is based on the Seas T18RE/XFCTV2 (H1333) which is a coaxial 18cm driver. This driver is used in the Ascendo C7 & C5. there are a lot of other speakers out there which use some version of this driver but I don’t think they are this latest ‘TV2’ version, but they are out there and probably very good.

My aim was to build a very good speaker with the minimum of fuss. So it had to have a simple crossover and simple cabinet. …and that’s what I have done I think!

In terms of sound they are on par with speakers costing a few thousand. Nearly as good as my PMC AML1s. They image VERY well, as would be expected and have surprisingly deep tight bass for the size of the cone.

They cost me about £300 all together.

Oh, and I designed them originally to have a rear tweeter because the roll-off of the tweeter in the Seas is pretty early so they sound dull. But after playing with the Xover I decided I liked them more without the rear tweeter and simply using a low value cap and a resistor to compensate the early roll-off which seems to work perfectly. My point is, I built mine with a sloping back, but you really don’t need to and I have not drawn the plans that way.

So, some pictures! I do have a few of the build but I have to get them off my Dad’s camera and since I did mine with the sloping back and you probably won’t, it doesn’t mean a lot. But it is a very simple box and I’m sure anyone with a bit of woodworking skill and build it in their sleep.







I know, I know… not a living room friendly colour! I always wanted a pair of boy-racer, Ferrari red speakers with go-faster stripes but never thought I would be able to live with them for long. So I finally have my wish And actually they suit my room very well! The white lines are in fact grooves cut in to the wood. I painted the primer in to the grooves but just went over the top with the red. I wish I had Shinobiwan's skills at paint finishing but I think not only don't I have the skill, I don't have the patients either! I want to see them done and finished as soon as I can

Here are the plans – internal and external measurements as well as showing how the wood goes together. I used 18mm MDF. To the left there is a diagram of how you can get the wood for both speakers out of one sheet of MDF, so wood won’t cost more than £20-£30.

I stuffed the cabinet pretty well as I will show in the pictures I get from my Dad's camera. But the important thing is to put lots of absorption (I used Rockwool) around where the driver mounts. I was getting some colouration which was reflections from the internal sides of the cabinet coming back through the cone. Once I put rockwool to either side of the cone it cleared up completely. I used lighter stuffing, the more standard loft insulation wads (the sort that hold their shape but are floppy) for the rest of the cabinet.

The port is tuned about right for most rooms I expect but for larger rooms I may tune the port slightly higher for a boosted bass responce. I made my port 55cm long and the speakers are used near room corners in a small room.

In terms of bracing I used a few slices of MDF that conenct between each side. The top and bottom brace I also cut an angled edge on and fixed one to the fron and one to the back baffle to help brace that at the same time.

There is also the crossover diagram. Very simple indeed The tweeter is marked as ‘-‘ because I think Seas already invert the terminals on it, so although it is a 1st order high-pass you have to wire it ‘out of phase’.

You can adjust the amount of treble by lowering (more treble) or raising (less treble) the value of the series resistor near the tweeter. I am using 1.33 ohms and it is just right I think.

You can also adjust the amount of bass and lower-mid via L1. A higher value will give you less bass, a lower value will give more. 0.3mH in either direction should give enough adjustment range.



Thank-you and enjoy

P.S. It does look a lot like the Ascendo C7 but apart from using the same driver it is completely my own. It would have been more similar wit the rear tweeter, admittedly.

 

:respect:

Well done, you should be very proud of yourself.

Whats the bass like?

 

They look very cool !

Is the circuit your own design ?

 

looks pretty damn good work!

nice one!






D.

 

They look excellent Simon. I like how you broke up the somewhat monolithic baffle with the port and router detail, works really well. I almost thought you'd done a transmission line with the slot loaded port.

Not bad for 300quid if they're close the £3k AML1's!

Not sure about the colour but hey, who cares about that.

Once again, great job and I'd really love to see and hear these at the DIY meet later this year.

 

Where's the prancing horse Simon? They should go well with Meridian's new F80, if the built in speakers aren't man enough for you.

 

Dev, I saw that at the show and was very impressed. I didn't notice the horsy on the front though! Way cool

Levi, circuit is my own design. I use the woofers natural roll-of at high frequencies to make the xover more simple. The components on the woofer are simply for baffle step correction and then we have a 1st order high pass on the tweeter and the resistor to compensate the top end as I said.

The bass is very good! Listening to Evanesce - The open Door which arrived yesterday and the floor is shaking.

The overall balance of the speakers is clear and present, but not hash most of the time. A well recorded female vocal sound stunning, as does well recorded anything actually. You really get transported in to the recording venue. I think the large port helps with good quality bass though - I really like the sound of large diameter slot ports, both for sound and build reasons.

I must admit I like these more than the Ascendo C7, which is about £3.5k (£4.5k with the piano black! Painted by Porsche). The Ascendo have deeper more powerful bass since they a have a band-pass woofer in the cabinet and crossover to that. But I think they went too complex. The beauty of this Seas is how simple you can go in the crossover and still have brilliant sound.

I will take them to the show if I can get a lift Ant. I might have something more practical for me to take on the train by then though. I just got an email to confirm that Solen have got the new deflector pads for the RAAL and will be shipping to me now. I also ordered some other parts for some small very high quality speakers so we shall see what happens!

Just to add, this is the computer modelled impedance plot. It is not that friendly, but it is suitable for most solid-state amps with I’d have thought. My Cyrus 3 can drive them without complaining. Pretty much a no-no for valve amps though I’m sorry to say.

 

Impressive, Simon.

I am curious if Seas would have a bigger DC driver? Like 15" at least

 

Volt do! Check out the FR220.1 which is an 8" with a dome tweeter and the RVCXD3153 which is a 12" with a BMS compression driver mounted coaxial.

 

Wow! - you really have painted them red

They look superb and well done for getting them up and running so quickly.

Have you tried running the bass/mid driver direct?
Usually gives better bass grip and PRaT at the expense of tonal balance and of course you'd lose the baffle step correction.

A good valve amp (and I mean good - not some limp crap) would probably manage on it's 4 Ohm tap given that power damands are massvely reduced above 10khz

 

Hi,

Talking with Thorsten he pointed out that 4.7uF in to 1.3 ohm (the tweeter and parallel cap) is about the same as 1uF in to the tweeters own 6 ohm DCR. So I tried that and it is pretty close. After a bit of toying around I have found that 1.33uF with a 1.33 ohm resistor in series with the tweeter gets me the same response I was listening to before, but with a much more acceptable impedance plot. So I have updated the design posted above and how to tune the top end response. Thanks for the tip Thorsten!

Rob, I had the woofer running with no BSC (baffle step correction) to begin with and it was way too bass light. I think the BSC is a necessity, I wouldn't have used it if I didn't have to. With it, the bass is just perfect and the lower mid fleshes out a little bit too with gives a more balanced sound rather than all tizz and boom which is what would happen if I just tuned the port higher. If I could get them really[/] near the back wall then I may be able to do away with it but the cabinet would need to be really thin and very wide and high to get sufficient volume. Not really practical IMO.

Anyway, here is the new impedance plot - much nicer.



Oh, I also asked him "Is the low impedance really an issue at such a high frequency though?"

and he replied-

"Especially there.... Most Amplifiers have falling feedback amounts (minimum 6db/8ve) AND rising natural (pre NFB application) distortion (at least 18db/8ve) so that IMD and all sorts of nasties rise up anyway, given the load dependence etc. I find the effect significant, try it."

 

Sorry to hijack your thread Simon but you mentioning Thorsten reminded me to congratulate him on this review of AMR kit by 6moons.

 

I drewd some pictures

 

Nice work, Tenson.
I like the colour!

 

Hi Tenson

Is there a bookshelf size enclosure design for these drivers?

Also, do you have a BoM and list of suppliers for all the required parts (excluding mdf of course....)

never done speaker diy before, but very tempted by this...

cheers

James

 

Hi James,

While the drivers can work in a bookshelf size enclosure, I did not design them as such and the bass roll-off and baffle-step compensation would be rather different.

I could try and estimate what would work but I think it is best if you just follow the proven design since I can't promise it would work well otherwise. Things always need tuning by ear.

 

fair enough, cheers, may well give these a crack if I get the time over the coming months...

ta

 

I also am extremely tempted to take a punt but have absolutely no experience. I can get the woodworking dome semi-professionally by a mate who would veneer them for me if I beg, although the go faster stripes probably add to their look - maybe I'll get him to do a bit of marquetry. Is there a way they could be wired and fitted out after all the carpentry were finished or should the 2 processes go hand in hand ? Perhaps if the bottom were the last piece to be fitted/glued. Also what are the green pieces - bracing ? and is there a black art to those angles ?
Would my Sugden A21Se be up to driving them ?
Being front ported, would 30cms from the back wall be a problem ?

 

You will need to add the stuffing before they are sealed up. I built / glued everything on to one side panel and then the other side went on last. If your friend screqwd the last side panel on each speaker when making it you could un-screw it to add the bits inside. Then when you are done, screw and glue. It is a good idea to put the wires in too, from the driver to the terminals where the Xover will be. I forgot to do that and it was hard work getting them threaded through with a load of absorptive wadding in the way.

I'll try and get some pictures of the stuffing tomorrow. I thought I had some I took when I put it in, but it seems not.

The bracing is at an angle because you want enough space for the air to flow freely and you also don't want standing waves between any of the cabinet sides and the bracing... so having it at an angle is the only option left. The piece near the driver wants to be done so it won't reflect sound back at the driver.

I got my inductors from Falcon Components and used 'super power' ferrite core. Using ferrite core gives a lower DCR than air core and as long as they do not saturate they have no more distortion. The resistors and caps I simply ordered from RS components. Caps want to be 50V rating or more and the resistors need to be 15watts or more. I think used 25watt for the ones on the woofer network. RS also sell speaker terminals but I had some from an old Gale speaker that I used.

I use mine about 30cm from the back wall, but I have bass traps there. I tuned the port to 55cm which seems to work well for corner placement.

Your Sugden should drive them alright with 30watts.

 

Hi Tenson,
In for a penny.... I am definitely going to try your design and was wondering if you had had any "What if ......" thoughts - I dunno, damping the cabinet walls internally or "why didn't I put the cone 1.67 cms lower" or double skinning the front baffle or anything like that. I really fancy the idea for their simplicity and the possibility to "tune" bass response. Have you any ideas on how I might minimise the adverse effects of a dirty great antique roll top burr walnut bureau stuck in between my speakers which means they are virtually in an inverted corner position ?