THT low profile build.

[But it Hertz]

So I placed it where I think will be its final resting place in the living room. Holy. Shit!!! What a difference giving it some space makes!!

I have been ultra lucky with placement. The bass hits super hard all over the sofa.

Luckily almost the entire kitchen seems to be in a null so that's perfect. I pity future guests though. The spare bedroom seems to be a hot spot.

I haven't got my receiver yet and I'm only running with 2 SLA's and a miniDSP. I spent an hour or so EQing it and then spent a while playing.

I think some of my disappointment from yesterday stemmed from the fact that I have probably never heard 15 Hz or 20 Hz on my terms before so didn't know what to expect. It's not "loud, loud" like 35 or 40 Hz.... I played a 15Hz tone at 20v and the house literally shook, although there wasn't a great deal to hear. The SPL meter could see it though.

The bedroom door on the other side of the house was literally moving 1/4 inch at 15 Hz!!! I couldn't believe my eyes.

After an initially shaky start I'm starting to really appreciate what this is capable of. Movies? OMG. Yes.

Turns out a nice volume to watch movies is approx 80 to 90 ish dB. Any more than that and your ears start complaining. This seems to equate to circa 5v so there is plenty in hand. I needn't have worried about achieving peak RMS values

Amazing that it produces such pure tones at such high volumes. One unexpected surprise... it's really difficult to locate the bass. First time I have experienced that. Very happy indeed.

So now I need to make more SLA's and get a receiver.

I still need to do some finishing work so I'll take some measurements outside and post them here at some point.

[But it Hertz]

And getting the most out of a sub is just like buying real estate: what matters the most is location, location, location. The worlds best sub simply won't work if you put it in the wrong place.

I'm starting to get it. If only there was a way to see the sound waves!

[But it Hertz]

Silly question time. Just trying to get this completely.

The limit for the THT is 28V.

OK, so does this apply to pretty much any THT driver (unless 28v happens to be more than the thermal limits of a paticular driver)?

To choose the driver that gives the highest output for a given horn, I should always go for the recomended driver with the highest xmax rather than highest RMS?

Would there be a difference between total horn output comparing 2 drivers with the same xmax but one is rated at 250w and the other at 500w?

Or to put it another way. When choosing a driver, if money is no object how do you choose the one that will give you the highest SPL in a given horn.

[shawn_g]

...
Or to put it another way. When choosing a driver, if money is no object how do you choose the one that will give you the highest SPL in a given horn.

The driver with the highest Vd (volume displacement) figure will have the most output (assuming the other specs are within range). Some manufacturers don't list the Vd in their T/S parameters, but you can use a calculator like this one to figure it out assuming you have the Sd and Xmax parameters:
http://www.ajdesigner.com/phpsubwooferc ... uation.php

[But it Hertz]

The driver with the highest Vd (volume displacement) figure will have the most output (assuming the other specs are within range). Some manufacturers don't list the Vd in their T/S parameters, but you can use a calculator like this one to figure it out assuming you have the Sd and Xmax parameters:
http://www.ajdesigner.com/phpsubwooferc ... uation.php

This makes a little more sense. Thanks.

So would there be a difference between maximum horn outputs comparing 2 drivers with the same Vd but one is rated at 250w and the other at 500w? The answer is surely "no, but the 250w driver would be more sensitive".

Also, how is the 28v limit for the THT arrived at? Is it a true statement?

[shawn_g]

So would there be a difference between maximum horn outputs comparing 2 drivers with the same Vd but one is rated at 250w and the other at 500w? The answer is surely "no, but the 250w driver would be more sensitive".

I don't believe so. I'm mostly talking out of my butt here, but say you have a 500w driver with 12mm of xmax and a 250w driver with 12mm of xmax. The 500w driver's voice coil might be able to handle more wattage before frying itself, but that doesn't mean anything if it runs out of xmax at 250w with a 20hz sine wave.

Also, how is the 28v limit for the THT arrived at? Is it a true statement?

Speculating again, but I always assumed voltage limits were based on a combination of the driver RMS handling and when the driver runs out of xmax. I have no idea how that magic number of 28v was derived though. Realistically, the limit is going to be different for each driver based on the xmax and power handling.

Someone correct me if I'm wrong here. I'm a newbie too.

[But it Hertz]

I appreciate the conversation even if it is out of your butt! (that didn't mean to sound creepy in any way)

So unless anyone else says otherwise I'm going to go with what you said

It kind of feels right.

[But it Hertz]

So I passed up a great Xmas deal on the DVC385 thinking it was too cheap to be reliable enough (having recently toasted the rather cheap MCN 55-2421)

Of the recommended drivers, it turns out the DVC385 has the most displacement!! Wow. Lesson learned there!! Could have saved almost $100 with a different mind set.

DVC385 $119
Vd=1252cc

RSS390 (my driver) $172
Vd=1161cc

Lab15 (not recommended over 21 inch cab width) $280
Vd=971cc

Lab12 $165
Vd=658cc

Interesting stuff!!

[Grant Bunter]

There is a definite limit to all drivers, regardless of Vd and Xmax and thermal limit.
Horn cabs seem to place limitations on drivers that direct radiators don't (but doesn't mean they don't perform well against them).

While Vd is king in comparing 1 driver to how many of another driver, all the parameters are finite in horn loaded cabs. You can only get so much with a specific design.
The whole idea of limiting the driver to a voltage (at least in pro sound cabs) is to prevent it failing.
In the home scenario, the defining limit is your ears.
Stoopid loud is just that, stooopid loud.

[matt996]

The RSS driver has a more advanced motor design with shorting rings and all that. In theory that should give lower harmonic distortion, which might matter if you find yourself driving the horn below its cutoff. The harmonics would still be in the horn gain band, so it's good to have a driver that minimizes them. IMO, money not necessarily wasted. Whether any of this is actually audible, well that's another question

[Bill Fitzmaurice]

Horn cabs seem to place limitations on drivers that direct radiators don't

Not really. The difference is that when you push a direct radiator past xmax you hear it, with a folded horn you don't.

The RSS driver has a more advanced motor design with shorting rings and all that. In theory that should give lower harmonic distortion, which might matter if you find yourself driving the horn below its cutoff.

All moot in a folded horn, which filters above bandwidth harmonics out. Most of what you're paying for in a premium driver just doesn't matter in a folded horn.

[Ian Westwood]

I had a rush of blood to the head this morning and woke up determined to install my Bash 300. I'm really pleased with the results and the Bash amp is a little gem. More than enough power for the THTLP.

I love the auto power feature that puts it in standby when there is no signal present. That is a nice touch!


I rechecked the driver for leaks having used it for the last month or so. It was fine but I put another quarter turn on all the bolts for the feel good factor.






I found a very slight leak on the cover that wasn't there when I first built it so I doubled up on all the screws. That fixed it!

[Drey Chennells]

The bash amps are great but not airtight. A subchamber behind it is needed or substantial sealing behind each leaky connector/control etc..

[Ian Westwood]

The bash amps are great but not airtight. A subchamber behind it is needed or substantial sealing behind each leaky connector/control etc..

Hi Drey,

Yeah, I was concerned about leaks and this was a bit of a gamble. But I'm pleased with the results. I would have thought a sub chamber would reduce the volume of the rear chamber too much, affecting the performance.. You'd have to allow for it during the build. I was originally going to put it in the external void between panels 8 and 10, but I hadn't allowed for the speaker wire during the build. It would have been ugly.

They are obviously 'supposed' to be air tight. I wish I had taken some close up pictures of the back of the Bash. They look to have spent a lot of time preventing leaks... and this one thankfully does not leak. It even came with pre-stuck speaker gasket with holes cut for the mounting screws.

I just checked the Parts Express reviews... couldn't find a single mention of an actual leak. How long ago did you try? Perhaps it was an earlier version or perhaps just a bad one??

If this one had leaked I would have tried drizzling some epoxy on the parts that leaked or even returned it.

I'll keep an eye on it for the first month or so and report back here if it gives me any problems.

Cheers,

Ian.

[Radian]

Top notch build Ian!