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8" vs 10" truck Tuba

Posted: Fri Nov 08, 2019 8:52 pm
by centner
Long time Lurker have built 4 24" wide Tuba 24's and now 1 truck Tuba for my nephew. After having it installed we couldn't leave the install store for 2 hours as they had all their techs come through and listen to the vehicle. They couldn't believe what they were hearing out of a 8" box with only 300 watts. As kids are kids and deeper and louder is always better I was wondering how much more output you would get from a 10" box. I built the 8" box 8" deep with theTang Band W8-740P driver. I would go the full 10" with the next build any recommendations on the two drivers listed in the plans (Dayton DCS 255-4 and LS10-44) both are cheaper than the Tang Band I used last time? or another driver that is better than those


Re: 8" vs 10" truck Tuba

Posted: Fri Nov 08, 2019 10:30 pm
by Bill Fitzmaurice
A ten might go louder than an eight if it has greater Vd (xmax times Sd). With all else being equal, and assuming you don't exceed the thermal rating, doubling Vd will give 6dB more maximum SPL. The W8-740 Vd is 260cc, DCS255 280cc, LS10 360cc.

Re: 8" vs 10" truck Tuba

Posted: Sat Nov 09, 2019 1:56 pm
by himhimself
Follow on question, as I've been thinking about building a trucktuba. My plans don't list the dayton LS10-44, but I just looked it up and it's specs fall nicely in the middle of the recommended ranges. Plans say with a 10" driver, minimum cabinet width should be 7" (6" internal panel width). Is that just to accommodate the driver depth? With the shallow LS10-44 (only 3.4"), could the cabinet be made narrower like the 8" driver version? Would the benefits of the 10" driver still be realized, with say a 5" deep box? The LS10-44 is about twice the cost of the MCM55-2421, and would take a two channel amp to drive since it's DVC. Wanting to do this on the cheap if possible, so any advice on whether I should consider this option. Thanks!!

Re: 8" vs 10" truck Tuba

Posted: Sat Nov 09, 2019 4:05 pm
by Bill Fitzmaurice
With the larger cone area of a ten the horn throat needs to be wider, which is accomplished by making the cabinet deeper.

Re: 8" vs 10" truck Tuba

Posted: Sat Nov 09, 2019 10:00 pm
by himhimself
Aha, thanks Bill. I think I'll probably stick with the 8" MCM then.

Re: 8" vs 10" truck Tuba

Posted: Fri Apr 17, 2020 12:51 pm
by iSurfSouthChinaSea
Hello. I am new to the forum but not to the site. I would like to resurrect this thread.

I bought a tiny "kei" JDM van (Subaru Sambar) for weekend runs to the beach and occasional gigs with bass gear, including an upright.
I have been out of the car audio scene for about 10 years, as I tend to do a system, set and forget.

I am thinking the truck tuba would be perfect in that I can simply put my cargo- bike, boards, bass gear on top of it.
I'd like to do this while the beaches and bars are still closed. I would also like to keep it efficient and use modest power amps that don't draw too much current.

I am leaning for an 8" driver and from what I read above I would appreciate any guidance.
Looking at the Dayton UM8-22. Seems to be a good candidate with a claimed Xmax of 16mm, Sd of 211cm^2, Qts of .58.
If the TB W8-740P has a Vd of 260cc, what, would the UM8 yield in Vd and would there be a noticeable improvement in either extension or SPL?
It seems the stated power handling is much better on the UM8 and its DVC. With the UM8, would a depth 6" be acceptable?
Are their other drivers I should consider? Goal is SQ over SPL.


Re: 8" vs 10" truck Tuba

Posted: Fri Apr 17, 2020 1:51 pm
by Bill Fitzmaurice
Forget SQ. That's determined by the enclosure, not the driver, assuming the driver is within spec. The same applies to frequency response and sensitivity. Whatever you learned about direct radiating designs doesn't apply to horns.

Re: 8" vs 10" truck Tuba

Posted: Fri Apr 17, 2020 1:59 pm
by iSurfSouthChinaSea
Can the design be scaled up so that the mouth the horn is bigger?

Re: 8" vs 10" truck Tuba

Posted: Fri Apr 17, 2020 2:09 pm
by Bill Fitzmaurice
Make it deeper.

Re: 8" vs 10" truck Tuba

Posted: Sat Apr 18, 2020 3:19 am
by SethRocksYou
iSurfSouthChinaSea wrote:
Fri Apr 17, 2020 12:51 pm
...Looking at the Dayton UM8-22. Seems to be a good candidate with a claimed Xmax of 16mm, Sd of 211cm^2, Qts of .58.
If the TB W8-740P has a Vd of 260cc, what would the UM8 yield in Vd...
Hello and welcome to the forums. I'm Seth.

Vd is calculated by multiplying the cone area (Sd) by the distance the cone travels (Xmax). So, even though a manufacturer may not provide a stated spec for Vd, it's easy enough to calculate if the state an Xmax and Sd.

In your case, convert Xmax from mm to cm then multiply by the Sd. 1.6cm x 211cm² = 337cc Vd

Re: 8" vs 10" truck Tuba

Posted: Sun Apr 19, 2020 12:06 am
by iSurfSouthChinaSea
Thanks. I was getting 3,376 because I didn't convert 16 into 1.6. Math.

I'm guessing 337cc would, in theory, have higher output than the TB's 260cc but identical sound quality to TB or the $30 MCM driver.

I would still think the UM8 would be better due to the increased RMS (thermal) rating. I would shoot for a single chassis solution for amps but 250 watts sounds perfect for my modest needs.

Now, I am wondering whether all cabin gain is created equal and what I could expect from the boxy cabin of a kei van. I would think it would behave like other econo-box cabins like the Scion Xb or Kia Soul. Does the cabin gain in small boxy cars differ thank those of crew cab pickups, 4 door sedans etc. Or is that immaterial and only applies to direct radiators? Assuming I cornerload the mouth of the horn in the van, should I still expect a nosedive at 50Hz, per the graph?

Been looking for more reviews and info but there isn't much in the usual outlets.

Thanks so much.

Re: 8" vs 10" truck Tuba

Posted: Sun Apr 19, 2020 1:33 am
by SethRocksYou
I have a 2x8" MCM loaded Tall AutoTuba, which in the past I had in a Jeep Cherokee. The "boxier" one. Granted it's not a Truck Tuba, but sound was absolutely fantastic. Cabin gain offsets the response rolloff and it played well down into the 20's with serious authority. Loud and silky smooth. A TruckTuba will likely be awesome for you too.

The TAT is too large for my current vehicle, VW Golf TDi. However, a turck tuba should fit nicely, laid flat in the cargo/hatch area. It's on the to-do list of builds. I'll be loading it with the MCM 8" driver. After having the twin loaded deal, I'm confident a single will suit my current needs handsomely.

I really wouldn't sweat the details too much. Although, I'm very much guilty of doing so quite often myself. That said, go ahead and get that UM8 and a sheet or two of ½"/12mm plywood and get it built. Even if you went with another driver that cost less but is still in spec... you'll likely be all grins. Looking through the plans, it really shouldn't take more than a few short afternoons or evenings at a comfortable non-rushed pace to start making some noise.

Any amplifier will surprise you. Even if all you had was 50 watts.

The last car audio system I did was in a Chevrolet Extra Cab pick-up truck. The amp I used had 5 channels and was about the size of a red brick. It was plenty. The real icing on the cake is in the signal processing, which I used a Dayton Audio DSP deal. It had all the crossover and EQ I needed to make it sound simply outstanding. That system did not use any Bill Fitzmaurice cabinets though. Point is, I'd be more apt to put money into DSP instead of larger amplifiers.

Anyway, happy to help with any other questions. Good luck with the project :thumbsup:

BTW, I'm Seth. What can I call you, man?

Re: 8" vs 10" truck Tuba

Posted: Sun Apr 19, 2020 5:32 am
by AntonZ
SethRocksYou wrote:
Sun Apr 19, 2020 1:33 am
Any amplifier will surprise you. Even if all you had was 50 watts.
This. I have had my stock autotuba for many years now. It fit the vehicle we had 15 yrs ago. It doesn't fit well in my daily drives for the last 10 yrs or so, now it sits mostly in the attic. When I went on a long trip alone to the UK I wanted nice music, so I got out the autotuba and just dropped it in the trunk. I hooked up a cheap amp from the cigarette lighter socket. It was plenty of power for me. Mind you I am in my fifties now, I am not after bleeding ear drums. The effortless silky smooth aspect of the bass coming from an autotuba in a car is very satisfying.

Re: 8" vs 10" truck Tuba

Posted: Sun Apr 19, 2020 12:38 pm
by iSurfSouthChinaSea
Oh this is all good news. It seems these days I have nothing but time to overthink this stuff.
At the risk of getting admonished for going off topic, any help would be appreciated for the remainder of the system: head unit, DSP and midbass solution.

I'm encouraged by the low power thing in car audio.
The factory locations of the front speakers seem useless: 4"x6" that fire slightly downward towards the knees.

But at least the horny theme continues. I will be trying the under dash HLCDs from Stevens Audio. (So much for frugality.) There are the "Minihorns" and are designed to crossfire. Eric Stevens suggested 1,200Hz @ a 24dB LR slope. As a threshold matter, these will fit easily.

The real challenge I see will be the midbass. Fatai 5" or Eminience 6.5" in the doors? That will require fabricating something. A friend offered to help image the door panels and 3D print something. I would like to take the path of least resistance. I haven't seen any off-the-shelf pods/enclosures that would work yet. I was also thinking of using the factory 4x6 locations and trying to stuff a sealed PVC pipe enclosure and loading with the Fatai 4". But that may require cutting some metal and may only yield lukewarm results.

For power, I would, at a minimum need a 4 channel amp wherein channels 1 and 2 would power the HLCDs and channels 3 and 4 the midbass. Or better yet a 5 or 6 channel to handle everything that doesn't draw more than 30-40 amps. There is a cool 4 channel from Audio Control that is not expensive, waterproof and very small. But I would need another amp for the sub.

For DSP, we have the Parts Express DSP thing, as well as the boutique stuff. Should I get an outboard DSP or would the onboard DSP engines on the latest head units from Pioneers, Alpine, Kenwood etc. would be adequate? Not all have 3 way crossovers or the required frequency(1.2khz) choices.

I am not really consulting with anyone else. The car audio biz seems geared towards mediocrity and absurdity and not much in between. So I avoid that scene.
And I doubt the customer service rep at Crutchfield would get where I am coming from.

Anyway, those are my thoughts.

Re: 8" vs 10" truck Tuba

Posted: Sun Apr 19, 2020 3:13 pm
by SethRocksYou
Mr. Smith, If it were me, I'd get the Truck Tuba built, put some 4x6 Coaxial's in the doors, DSP, and a 5 channel amp (and only use 3 channels) in there and see if I felt like it was worth going any further. With DSP, you can get nearly any system to provide impressive SQ as long as the components are reasonably capable of producing the frequencies. Once upon a time, I had a pair of cheap tweets rated to 18k that wouldn't do anything past 16kHz no matter what I did with the signal processing. Anyway...

Here's some items I have experience with that I'd recommend to any friend. They are budget minded, but not bottom of the barrel:
Kenwood Head unit w/o CD player ... If you want a CD player, don't get this one.
Dayton Audio DSP-408 ... Awesome unit, great price. User interface is on PC and isn't entirely intuitive. But easy enough to figure out.
Soundstream 5 channel amplifier ... Probably a bit over rated in the output rating, but still a decent unit that did what I wanted. Compact too.
Kicker 4x6 ... Does what they should.

Having done that system before, I'd do it again in a heartbeat. For you... It sounds like you may want to take it a little further. It's a good place to start. Could install all that in a day and have a very respectable system quick, easy, and at a reasonable cost. Leaving the option open to add the Stevens Audio tweets at any later time and just band pass the highs out of the 4x6's in the DSP. From there, you can obviously go as crazy as you want with custom install stuff.

Here's something else I highly recommend after using it the last install I did; 9 conductor wire. Runs 4 channels of audio and a remote turn on from the amp to behind the dash in one go. Way more tidy than 4 individual zip wire runs and a turn on. From behind the dash, just tap into factory speaker wiring and/or split off to the tweeters if that's the set-up.

Anyway, that's all I got. Good luck with the build.

Oh! Wait! One last thing... You can download a free app on your phone or tablet and use a Dayton Audio iMM-6 Calibrated Measurement Microphone to get everything dialed in beautifully.