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Hybrid Practice cab!

Discussion in 'Amps and Cabs [BG]' started by Bass Unique, Jan 20, 2012.

  1. Bass Unique

    Bass Unique

    Nov 3, 2011
    Hi, thought I would share my latest build with you all. This is a small practice combo I have built for rehearsals and small acoustic/Jazz gigs.

    It uses an Eminence Deltalite 2 speaker and I am using a GK MB200 amplifier in this combo (so it is providing around 140watts in to 8 ohms). at 97 dB/w this should give me 118 dB or so. Enough for a rehearsal.

    Here are some pictures for you:

    1 Finished practice cab.

    6 Design for practice cab.

    The speaker itself uses a long port in an adaption of my previous reflex/quarter wave hybrid. The design models suggest that I am getting around 45 Hz resonance from the reflex mode, which appears to model well if you consider only the 35mm straight section as the port. The rest of the tapered section appears to be partially "box volume" in the model. (Actual transition point is unknown at this time).

    The line length is physically 650mm but this should also include up to 260mm to the top of the box behind the driver. This would suggest a resonance of around 115 Hz although by tapering the line and partly stuffing it, the resonance is just under 100 Hz. (The driver spreads its output across the length of the first 1/4 of the line helping reduce nulls. This section is stuffed right up to the 180 degree bend at the top of the box.

    This means I can tune the system pretty low for a small box to prevent large cone movements at the low end and in a typical reflex box, this would mean I would breach the 4.2mm X max at 90 to 100 Hz. As it has this second resonance which controls the cone as well, this movement does not happen so I end up with a broader port output than a reflex and better cone control.

    In fact I have run this on my 300W amp (reasonably carefully) but drove it harder than the MB200 could allow and it still seems to handle it (short term as it is a 250W speaker).

    Will do an impedance plot next to confirm the resonances. It certainly sounds great (it also has a custom tweeter which I made 15 years ago.)

    If my calculations are true, this means I am converting more of the cone movement to port movement (some mass loading effects going on too). With a large area port, this is not a problem as the maximum velocity is still below 17mm/s. I tend to slightly flare the terminus to improve flow here.

    This also means that ultimate X max is less important in bass guitar speaker of this type than seems to be mentioned on this site for conventional speakers. If you model a sealed box, below resonance, there is lots of movement above the X max. For a high tuned reflex, even more at the low end. A low tuned reflex has more at 2 x the resonance. In my design, the entire low end is controlled and above resonances, the cone movement is never that large so up to 140W, no issues (in fact up to nearly 200W in this design).

  2. Bass Unique

    Bass Unique

    Nov 3, 2011
    Oh, and by the way, including my amplifier in this combo, it weighs 7.2 kgs. Would be less than 6 kgs if just the speaker.
  3. arai

    arai Banned

    Jul 16, 2007
    Great work. Subscribed
  4. oerk


    Oct 16, 2009
    Interesting, and unique. So, it's a crossover between a regular ported design and a TQWT?

    Would love more details about the custom tweeter.

    How did you mount the amp?
  5. Bass Unique

    Bass Unique

    Nov 3, 2011
    The neo dome tweeter is 38mm diameter so fits in the space perfectly in the top right corner of the front baffle (you could probably fit up to 45mm diameter at a push). It is not particularly efficient but adds a little sparkle above where the driver rolls off (5 kHz and above).

    Unfortunately these are no longer available as the company I was working for when I made it has gone out of business. You may like to try looking at some off the shelf car audio tweeters to fit in the small space. Keep the crossover high to protect them.

    The amplifier is fitted from the top in some custom mounts. It can slide out easily and forms my backup amp when gigging. It is super small! See pics below for space where amp goes and the top view.

    2 Finished except for grille.

    5 Rear view before fitting back.

  6. I'm neither a musician nor an electrician, (nor a beautician, mortician, optician or magician for that matter), but do you have any heat dissipation issues with the amp snuggled in that slot?

    I'm watching this with great interest as I can see needing one of these very soon. Nice work!
  7. Bass Unique

    Bass Unique

    Nov 3, 2011
    Interesting point about cooling. Its a fully class D - I have run it hard and it did not get hot enough to turn its fan on. The rear panel is not carpeted to minimise insulation and is very thin ply, there is air around the unit, especially to the sides and I have put in two holes on the back panel to allow air to circulate. See pics below:

    8 rear view of combo.

    7 Bottom view of amplifier.

    I thought people would be more interested in the speaker so I omitted the amp build part! These should show you some more details.

    In terms of cost, the Amp was £200 new and the speaker is now around £115 new (neo prices still high!). The wood was £20. It took a day to build it plus another half day of finishing. So, some DIY plus £350 gets you this combo.

    I am confident it would outperform most other small commercial combos with 140W at twice this price. Most seem to have 50 to 60 watts. Of course, you cant beat building your own and knowing you put in the time and love to build it. Makes you proud :)

    Headphone jack, aux in and DI /line out. What else do you need? It only has one speaker connection but you can fit another one in the back of the cab if you need one.
  8. Bass Unique

    Bass Unique

    Nov 3, 2011
    By next month I will have another one in the range. I already have a large cab (see Transmission line cabs thread previously) and this would be a smaller one designed to stand alone for smaller gigs or to be sat underneath the large cab, matching size, finish etc. will be great.

    It will use a 3012 HO driver and a Number 1 tweeter in a slot at the top angled upwards. For stand alone use, it would have full range to the HO driver and the tweeter would take over above 4 kHz. As it is facing partly upwards, if you stand by your amp, you still get some HF.

    For use with the large one, the tweeter section will be covered and a second input allows it to have a 500 Hz crossover matching the LF driver in the unit above.

    I anticipate 39 Hz reflex resonance with an 80 Hz T-line resonance. It should take all 400W without having too much excursion.

    So the range would be large and small cabs for gigs (or the combination for the larger gigs) and a practice cab.

    More details on this new one in a new thread. I will post dimensions again.
  9. Thank you for the additional pictures. Everything makes perfect sense to me (a usually scary situation).
  10. will33


    May 22, 2006
    Another sort of quasi-TL hybrid? This one looks fairly compact..."old guy friendly":D

    I'm liking your designs, man. They're a different approach, something out of the ordinary, not your typical smallbox combo....nice.
  11. YuppyPunk


    Oct 21, 2011
    Cool design. The only thing I think might be a problem is that if you ever decide to make a matching extension cab it will be hard to make it sit flush underneath. Plus you'd have to to redo they way that the head connects to the speaker as the MB200 only has 1 speakon.
  12. Bass Unique

    Bass Unique

    Nov 3, 2011
    You could build an extension cab deeper to match the combo. This would raise the box volume from 11 litres to around 16. In order to control the cone and re-set the tuning, you need to make the channels larger. It would work, I just need to come up with the sizes for you. (This is what I would eventually do on the website - taking my standard designs and modifying them for custom jobs). It would be better for a 5 string too and have a resonance around 39 Hz instead of 45 Hz.

    I used an encapsulated speaker lead (so I never lost it) on my design but it would be simple to fit a speakon/jack combo output connector so you can always connect to another cab as well. Don't forget it is a simple job to slide out the amp and use it on any other cab too!
  13. Bass Unique

    Bass Unique

    Nov 3, 2011
    I have taken this small Hybrid single 10" to a loud rehearsal and I have to say that I was more impressed than I thought I would be. Using the GK MB200, I left it on flat response and there was still plenty of low end. It went pretty loud too. It should be good for semi-acoustic and boutique gigs too.

    I would encourage some of you to try to build this speaker to see what it can do. It certainly controls the cone well. You have the dimensions in a post above - the stuffing consists of 30mm undulated acoustic foam lining the 11 litre box and at the top of the 180 degree bend. There is then some teased out polyfibre directly behind the driver and loosely filled in the first section of the channel. The rear tapered section and straight section are unlined.

    Full bass is available down to E 43 Hz. (System reflex -resonance is 46 Hz). The lower notes on a 5 string are still very powerful but it is rolling off slightly below 40 Hz which is certainly adequate! Bearing in mind this is a small combo and most roll off somewhere around 60 Hz, it sounds much bigger than it is.

    The tweeter I have used seems to be around 90 dB/W (far less than the 97 dB/W of the Deltalite 2 but it is still helping over 5 kHz for those that want the sparkle on the top. A more efficient tweeter would offer higher top end output. Even so, I left the control flat and just boosted the highs a little on the bass. (Mayones Be Exotic 5 string)

    So, build away, ask me as many questions as you need and hopefully someone will give a review!
  14. oerk


    Oct 16, 2009
    Very tempting, except for the fact the amp and speaker alone would be 400€, not counting wood, finish and hardware. Can't afford one right now.
  15. miiitch


    Nov 27, 2011
    very interesting

    i suddenly feel the need to build a similar one, just bigger and with lower resonance for full 5-string compatibility :cool:
  16. Bass Unique

    Bass Unique

    Nov 3, 2011
    Just wait another few week and I will post a design using a 12".

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