Basschat easy-build lockdown cab project

[Downunderwonder]

On 30/05/2021 at 23:51, Phil Starr said:

the average pub gig

With the PA doing the work? That's not average for me.

[EBS_freak]

9 hours ago, Downunderwonder said:

With the PA doing the work? That's not average for me.

Then you know what to do! 

[Downunderwonder]

11 minutes ago, EBS_freak said:

Then you know what to do! 

The question was for the OP.

[EBS_freak]

16 minutes ago, Downunderwonder said:

The question was for the OP.

If it's not average for you, then make it so. The lower stage volume and dispersion of the band throughout the PA speakers will make your band sound so much better out front.

[Downunderwonder]

53 minutes ago, EBS_freak said:

If it's not average for you, then make it so. The lower stage volume and dispersion of the band throughout the PA speakers will make your band sound so much better out front.

Ime 'pub band' venues don't have the capacity for worthwhile stage monitoring without causing an unholy mess out front, even with a stage. Vocal PA ftw.

So I asked OP what his average means.

[Chienmortbb]

On 15/05/2021 at 21:01, Phil Starr said:

2.83V is the voltage we use to check speaker parameters, it represents a standard 1W into 8 ohms.

This is true but for sensitivity you should use that voltage that gives 1W, so if the driver is 4 ohms, the input should be 2 volts.

[Jolltax]

On 19/05/2021 at 20:31, stevie said:

I'd advise against using carpet inside the cab. It's relatively heavy and not very effective. Carpet felt underlay is good - I use that for some things - or the usual BAF wadding, which is the kind of thing you find in duvets or sleeping bags. Don't put any within about six inches or so of the port.

More dumb questions! Went to my carpet place to get underfelt and they say they don't really use felt any more but have this stuff they use when they are installing underfloor insulation?

 

On 30/05/2021 at 12:51, Phil Starr said:

Just a quick update on the 110T, I have it back from Stevie and reassembled it. I had a chance to run some test tones through it and there really was a serious panel resonance on the baffle centred around the area between the port and the bass speaker. You really need a brace on the baffle behind that point. I'll make some changes to the drawings to show this.

Do I need to extend the length of my tubey port thing, what does a baffle brace look like?

Its sunny today so I'm off outside to start cutting holes and stuff!

J

 

Edited June 1, 2021 by Jolltax
duh!

[Phil Starr]

3 hours ago, Downunderwonder said:

Ime 'pub band' venues don't have the capacity for worthwhile stage monitoring without causing an unholy mess out front, even with a stage. Vocal PA ftw.

So I asked OP what his average means.

OK that's fair enough, pubs in the UK are usually fairly small and 50 people in the space you are playing would be a very decent audience. A lot of our pubs are pretty old so tend to have low ceilings and be odd shapes where separate rooms have been combined to make bigger spaces. Bands tend to be weekend warriors like myself rather than pro musicians and the better bands often move on to function work with bigger venues.

It isn't well paid over here and PA equipment is often basic with vocals only PA. That's why I mentioned that we are lucky enough to have PA that will handle a bit of bass when we need it, a lot of people will still want a bass amp that will be enough to reach an audience of up to 50 people and most of us in the UK are familiar with 'an average pub gig'. It was just a very rough guide to how capable this little speaker would be.

[FirstBass]

Hi All

I've read these pages several times now and my juices are flowing again so.......I'm about to build one of these cabs (maybe two)

I've built a few different designs over the years (home brew stuff, cubos, bill fitzmaurice tubas and jacks)

Two questions if I may

I've used the rice technique to determine the tuning of an enclosure and it works well (no access to anything more technical)

BUT

I've also tried the rice technique and then laid a grille on or stretched a grille cloth over the cab and the rice has begun to rattle again

This would indicate that the grille material has changed the tuning of the port slightly

Does the "resistance" of the grille material ever get taken into account? 

Also - i've read that the HF section often gets wired in reverse to the LF section (+ to - and vice versa) Has this been tried with this design? 

Looking forward to cracking on once all the bits arrive

I'll take plenty of pictures

Big thanks to everyone that contributes to this project 👍

Jon

[Phil Starr]

Funnily enough I've just done this to the prototype.

 

[Phil Starr]

50 minutes ago, carnabass said:

Hi All

I've read these pages several times now and my juices are flowing again so.......I'm about to build one of these cabs (maybe two)

I've built a few different designs over the years (home brew stuff, cubos, bill fitzmaurice tubas and jacks)

Two questions if I may

I've used the rice technique to determine the tuning of an enclosure and it works well (no access to anything more technical)

BUT

I've also tried the rice technique and then laid a grille on or stretched a grille cloth over the cab and the rice has begun to rattle again

This would indicate that the grille material has changed the tuning of the port slightly

Does the "resistance" of the grille material ever get taken into account? 

Also - i've read that the HF section often gets wired in reverse to the LF section (+ to - and vice versa) Has this been tried with this design? 

Looking forward to cracking on once all the bits arrive

I'll take plenty of pictures

Big thanks to everyone that contributes to this project 👍

Jon

Hi Jon, the resistance of the grille cloth is something I've thought about but never done any investigation of. We had a mouse problem once and I added some nylon over the end of the ports to stop them getting in, I didn't notice a change in their performance. The grille is clear of the port end of course. There is a bigger effect i would have thought on the horn output and I know that is clearly audible when you remove the grille from a hi-fi speaker.

Reversing the connection of the horn compression driver is quite common. The crossover components shift the phase of the sound so that a conventional even order crossover there is always cancellation at the crossover point and a dip in the frequency response, if you go back in the thread you can clearly see this in the frequency response plot Stevie measured. Reversing the connection puts the signal in phase and you'll get a peak. That's all assuming that the cone behaves like a piston and has no phase issues of it's own, and of course we went for a simple HPF to bring the horn in as the Pulse naturally started to roll off.

Generally speaking it's less obtrusive to have a dip than to have a spike in the response which will make certain notes jump out at you but as a self builder you can decide which you prefer. With my hi-fi designs I certainly try both and I've tweaked PA speakers by trying this in the past. I did try with this speaker (I'm an inveterate fiddler) and it is better this way round IMO.

Looking forward to your build and hope you love the speaker. All I can say is that when I'm testing it I end up forgetting the speaker and just enjoy playing bass.

[FirstBass]

Cheers Phil

Appreciate the feedback

Looking forward to getting on with this build

Then i'll attack V3 of the "other" design

 

[stevie]

On 01/06/2021 at 12:57, Jolltax said:

More dumb questions! Went to my carpet place to get underfelt and they say they don't really use felt any more but have this stuff they use when they are installing underfloor insulation?

 

Do I need to extend the length of my tubey port thing, what does a baffle brace look like?

Its sunny today so I'm off outside to start cutting holes and stuff!

J

 

That doesn't look like the kind of felt that works in loudspeaker cabs. You could use this: http://www.bluearan.co.uk/index.php?id=TUFFWAD14A

which is the stuff they use in duvets, pillows and sleeping bags. The original eBay felt supplier now has a minimum order of 15 metres, which is a shame.

Yes, you'll need to lengthen the port by 2 or three inches. The easiest way of doing it is with some card. Roll it round the end of the plastic port and attach it with duck tape of similar. Just make sure it can't rattle.

Edited June 9, 2021 by stevie

[paul_5]

Does a ported cab need insulation?

[JohnDaBass]

18 minutes ago, paul_5 said:

Does a ported cab need insulation?

Yup , the wind from the port makes it really chilly in there 🤣🤣🤣🤣

[Jolltax]

On 05/03/2021 at 08:50, stevie said:

Here's a diagram of the crossover. It doesn't get any simpler than this. I've assembled the circuit using a (chocolate block) terminal strip. So - no soldering needed. I'll post a frequency response of the finished system and of the assembled crossover later today.

The Pulse 10 is wired directly to the input and this circuit connects to the HF unit.

 

PLease could I just clarify a couple of things on wiring the crossover and the speaker internals :

Is it correct to wire the speakers in parallel from the input connector with the crossover just to to the HF speaker, as they are both 8 Ohms in parallel will the speaker then be 4 Ohms?

The connector thing I got for the back panel has two sets of connectors 1+ 1- and 2+ 2-, does it matter which ones I connect to or does the amp drive both?

Thanks in advance

J

 

[nilebodgers]

The convention for 4-pole NL4 connectors is full-range signal on 1+/1-. The 2+/2- pair are not connected in this case.

Bi-amp would have low driver on 1+/1- and HF driver on 2+/2-.

[nekomatic]

To answer the first one, at low frequencies the capacitor in series with the HF driver will have relatively high impedance, and at high frequencies the LF driver itself will have relatively high impedance due to the inductance of its coil. So the nominal impedance of the design is still 8 ohms. 

[Chienmortbb]

1 hour ago, nilebodgers said:

The convention for 4-pole NL4 connectors is full-range signal on 1+/1-. The 2+/2- pair are not connected in this case.

Bi-amp would have low driver on 1+/1- and HF driver on 2+/2-.

+/2- is also used to 100V line systems, however that is unlikely to be found on a bass amp/speaker.

[Phil Starr]

13 hours ago, nekomatic said:

To answer the first one, at low frequencies the capacitor in series with the HF driver will have relatively high impedance, and at high frequencies the LF driver itself will have relatively high impedance due to the inductance of its coil. So the nominal impedance of the design is still 8 ohms. 

For the OP yes this is spot on. You don't need to worry as all of this has been taken care of by @stevie in the design stage.

For anyone interested you'll notice that we always talk about a speaker's impedance but measure it in ohms, which is resistance. That's because the resistance of a speaker and the crossover components change with frequency. Capacitors resist low frequencies and inductors resist high frequencies. The speaker has a coil in it of course so that is an inductor too and it's resistance to the amp's power rises with frequency. The amp 'sees' a higher impedance.

In this case we have a capacitor in series with the horn tweeter which limits the bass and an inductor coil across the horn which shorts out or bleeds off the treble. The horn is louder than the 10" speaker so there is a resistor too, which reduces the horn driver's output. The trick is to match everything up so that at the crossover point there is enough 'resistance' to cut the output to each driver by half so the combined output stays the same across the frequency range.

One little point of detail is that the speaker is a really complex load with an impedance that varies at just about every different frequency. Stevie doesn't just rely on theoretical figures in designing his crossovers but by measuring each driver and building prototypes and then measuring frequency responses. It isn't rocket science but a lot of care goes into a simple circuit like this.

[Phil Starr]

I'm growing used to this a bit now, I've still got to spray the grille frame black but an extra coat of Tuff Coat has improved the finish since I took this pic. I wish the cloth had been black ad gold as advertised not black and brown but i can live with it.

Anyway I'm still testing it and I had a gig yesterday, a wedding with about 60 people in a well ventilated and quite large hall. Decent PA support and Covid restrictions on volume so i decided a good chance to run out the 110T as on-stage monitor. Our drummer didn't get the memo about volume but the 110T could still be heard and the PA did the rest (just a pair of QSC12's no subs)

We have a proper sound engineer now. He said something interesting when I asked about whether it had been enough from his point of view front of house. "I can't believe that little cab, it's the best bass sound I've ever worked with". What really? In normal non-Covid times the guy works with touring bands at festivals and in musical theatre, but I guess from his point of view it's just what he wants. The basic sound is clean and really rather sweet, it sounds like a bass with no sonic nasties to clean up, nothing to trouble the vocal mics and just enough to hold the on-stage sound together. It sits well in the mix and the basic sound is excellent. (and it is nice, I love playing it at home with my Peavey Minimax)

OK it's a simple little thing, it's only a 200W speaker and the components come it at only around £100 but I am so warming to it. I can carry in my complete rig in one go. Amp in a shoulder bag, speaker in one hand bass in the other. The bass is heavier and more awkward than the cab. Plug it in everything set flat and it just sounds right from the get go. You wouldn't expect a single 10 to hold up the bass end unsupported but it's only a little way off and it's enough to be your on-stage monitor and cope with anything short of a rock band. Did i say it sounds nice?

[FirstBass]

Me again..... Quick question

I'd like to use 2 of these with a 300W @ 4 ohm Shuttle 3.0

The bottom one with the hf section switched off

2 cabs daisy chained together would give me a load of 4ohms at my amp

Would this be an issue with regards to the performance of the crossover in the upper cab? 

I assume it would lower the crossover point???? 

Is a two cab setup viable with the simple crossover?

Cheers

[stevie]

The easiest way to do this is to build a second cab without an HF unit or crossover. Then link it to the full-range cab in the normal way. A second HF unit isn't helpful because you'll get phase-induced constructive and destructive interference between the two units (comb filtering).

[FirstBass]

will it lower the crossover point at all Stevie? 

[Phil Starr]

5 hours ago, carnabass said:

will it lower the crossover point at all Stevie? 

not at all though it will change the sound balance. In this design there is no low pass filter on the bass units. Stevie took advantage of the natural roll off of the 10" Pulse and designed the crossover to bring the horn in to take over the frequencies that the bass units don't create. The shape of the frequency responses for two identical speakers are going to be the same within manufacturing limits but you are going to get far more of those frequencies. Somebody out in the audience will hear a bass heavy sound but for you this will be countered by the fact you have raised the horn to nearer ear level so it may still sound very good to you.

The horn driver will still be seeing the same voltage being produced by your amp so will still be protected by the crossover.