Phil,

I just got my Boston Acoustics GT24 amp. I am going to replace the current 4-channel Memphis amp with this GT24 amp this weekend.

The Nakamichi HU will power the rear speakers, the GT24 will power the Kappa Perfect front speakers, I also have 2 Bose subs connected to HU sub's outputs (RCA).

Is there anything special about tunning the Boston GT24 ? I read the owner manual last night, it seems to me it is more complicated than the Memphis amp. I will follow the steps in the Boston manual in tunning the amp, if your experiences with GT22 in your minivan are different with what in the manual, then please tell me what did you do to make it sounded best.

Thanks and have a great weekend.

 

actually -- as best i recall, i went using my normal efforts and got good success. i actually have the GT-40 (close to the same power as the GT-22) to power all 4 channels in the van. (edit - correction, close to the power of the GT-20, not 22. but the van is really quiet on the road (compared to the S)... so 60 Wrms / channel is plenty for me)
looking at the manual - it looks as if they are a bit over done, but nothing outrageous.


i'm glad to hear you landed it, and hopefully at that price you mentioned. that was a sweet deal.

and yes, it probably is notably more complex than the Memphis amp with the biggest change being the Q control.

you'll need to set gains like normal. (w/ highpass to off, lowpass to off, and Q to .7)
then, set the highpass to ON and leave the lowpass OFF. figure that you probably want a crossover point around 50 hz or so. (figure about 1/2 way between the 20 hz (lowest) and the bottom dot.) you can readjust the gains w/ the highpass on, but w/ moderation (no huge changes... tweaking mainly)

then, you'll want to adjust the Q to match your ears. the Q is a very odd control (i haven't seen it much before), but essentially what it does is adjust the slope not of the crossover itself but of the rolloff right around the crossover point. thus allowing you to correct some for speaker frequency response rolloff or whatever around the crossover point....
actually -- it's a very cool little adjustment. but mainly, just use it to satisfy your ears.
then, recheck the gains to make sure you're not distorting or bottoming out the speakers.
done.


so -- summary.
roughly set gains. turn on crossover and set it up. set the Q. then readjust the gains for the final tweak.


the ONLY beef i have about the Boston amp is that the recessed RCA jacks are just too tight. i had to modify my KnuKonceptz cables to get them to fit...



that help?

 

Thanks Phil,

I got it for less than $285 shipped, it looks brand new with no scratches

The main different with Memphis amp is the Q settings as you said.
I will set the crossover point around 50 hz, just like I did for the Memphis, because the frequencies of the Kappa Perfect are 50Hz to 22kHz.

I will start the Q at 0.7, then adjust it after setting the gain with Highpass "ON" and crossover point around 50 hz.

Since the HU will power the rear for fill, the maximum volume of Nakmichi is 60 and maximum power is 45W/ch, the RMS power is about 12 to 15 Wrms. My guess is that the volume should be set at around 35 to 40 to get close to 15 Wrms without much distortion. To set the gain on GT24, I will set the volume at around 30 and the gain of GT24 such that I will get about 40 to 50% power from it, i.e., I will get the rated power of 120 Wrms (at 12.6V) at volume 35-40. Is this correct ?

As you can see, I am trying to get close to maximum RMS powers of both HU and GT24 at the maximum volume I will ever use (35-40).

I will report my tunning procedures later, and correct my steps if I made any mistake.

Again, Thanks for Your Great Helps, I can always count on you for Your Great Advices. Have a great Memorial weekend.

 

*nods* maybe a bit higher, but it should be in that range.

try this to get your max volume for the HU. connect the rears, and dial them up till you hear distortion of any kind (mainly clipping is what you should hear first - clipping is a blurring type sound of the music.). then dial it back a bit. that is where i'd set the amps. 40 sounds like a good number to expect, but it could be higher or lower.

the only thing i'd do different is set the volume of the HU just under the distortion point for the rears (like 2-3 notches... say if distortion at 40, set at 38/37), and set the amp right there. i'd do this rather than try to predict the distortion point by setting at a lower volume. that leaves less error in the situation. remember, if the fronts start to get too loud w/o distortion, you CAN leave it lower without any problems.
and when the car is running (closer to 14 V) this amp is going to be outputting close to 175 Wrms x 2 @ 4 ohms. so you might even want to tweak it out again when the car is running.

then set the Q at this point, just adjusting it for taste. you might have to dial the gain back just a little at this point -- since one of the things the Q will do is introduce some bass at the crossover point. that will depend on how close you get the gain to the ragged edge.




you have a great weekend as well... i'm just thankful that i get Monday off this year....

 

Hi Phil,

The Memphis amp is alived. Before I disconnected the amp, I tried to pound the amp cover with my palm, it did not work, I then pounded it with a large screw-driver handle, it did not work either. I then shaked and pounded the amp on the cross-over bar on front of the driver seat, it woke-up, but it went back to sleep as soon as I laid it down on the floor. That told me something was loose inside the amp. I then opened the amp cover and started tracing all connections, I found two loose wire solders. After re-solder these two wires, the Memphis amp is working again.

I will try to think about how do to use the Boston amp with my system. I do not like to have it collecting dust in the garage. The two Bose are 1 ohm subs, so that it can not be driven by the Boston amp (except in series). There are many options in utilizing 2 external amps: 120Wrms x 2 and 50Wrms x 4. Also the power of the HU: 15Wrms x 4

 

dude -- "I then shaked and pounded the amp on the cross-over bar on front of the driver seat, it woke-up,"
OMG!

i know i mentioned knocking on it... but i meant like you'd knock on a door...


very glad to hear it's up again. now.... what to do with it?

personally -- the Boston amp is a pretty darn nice amp. i'd consider using it to run your fronts. what about using the Memphis (maybe only 2 of 4 channels) to power your rears? and aren't the Bose subs self powered?