Lacking mid bass on Macintosh system in 08 Liberty

[Checker]

Hi All

New here and hoping for some friendly advice. I have recently upgraded the amp to a PDX-5 and had a 13" Focal sub put in. To run the new sub off the new amp, the stock 8" sub in the back shelf has been taken out.

The result is a louder overall sound with good clarity and nice (very) low end but am badly missing mid bass. So there is no "punch" if listening to any type of music (and generally very little bass guitar and kick drum when listening to rock/pop). While I'm a novice on car set ups, I have some experience with sound and can tell which frequencies are missing.

The options to get more mid bass as I see them are to:
1) re-install the stock 8" (or install a new midbass driver) into the back shelf, run it from the PDX-5 and intall a new amp just to run the 13" sub; or
2) sound deaden the front doors, lower the frequency response on the front woofers (sorry, not very technical expressions) and swap the 13" for a smaller sub (say, 10") (which I can do at no cost as the shop I got it from is happy for me to test out another sub).

I have spoken to the guys at the shop and they say option 1) is a waste as the 13" sub in the boot will lose its potency and will produce a muddy sound when combined with a midbass driver in the back shelf - so they recommend option 2). My concern with option 2) is that the woofers in the doors look tiny (4" I think) and won't be able to bridge the gap with the sub in the boot in getting the mid bass I lack.

Any suggestions would be appreciated.

Thanks

[mihai]

Did you swap out the front speakers?

How are they wired? Are they going to the McIntosh amp or have you removed the McIntosh and replaced it with the PDX-5 (therefore rewiring all speakers to PDX5)?

If you are running the PDX-5 along side the McIntosh, it will be very hard to match the crossover points on both amps as the crossovers on the McIntosh are unknown. Therefore you will have a gap in your frequency range if the crossovers are miss matched (which they probably would be if this is the way it has been set up).

If you completely rewired the PDX-5 in place of the McIntosh, then again, make sure the crossovers are set correctly.

Sound deadening the front doors helps quite a bit. And the front doors actually have 4 speakers. You have a 6" woofer, a 4" mid range a tweeter and a squaker. So in terms of bridging the gap, they should be fine. However, a decent set of after market 2 way speakers (6" woofer + 1" tweeter) have proved to sound better (paired with the right amp) than the stock speakers. So thats another option for you.

[solongaudi]

At the risk of embarressing someone, have you got your front speakers wired in the correct phase (+ to +, - to -) on both input and output. This can cause a massive decline in 'midbass' (80hz to 250hz) which is actually handled more by your 6" woofers than your sub (which is why a sub is called a sub, because it handles sub-bass frequencies 80hz and lower). If the woofers are wired out of phase you will have one speaker pushing while the other pulls and that will cancel most frequencies that are meant to be deliverd by those drivers, leaving only reflected overtones that are slighly out of phase due to reflection delay. In short it sounds terrible.

The other big thing after an upgrade that I find people pay off (includeing installers from reputable stores) is seating the base of the driver properly. ensure there are no airgaps between the back of the driver mounting ring and the seat of the hole your mounting it into, I find strip foam to be quite good for this as it compresses as you tighten down, I have also seen silicone used but I shy away from this method for obvious reasons, its just far too messy and if you slip you can destroy the driver by glueing up the spider and coil :-O!!! Any air gaps that exist here will allow positive preasure on the back half (negative) end of the audio signal to escape onto the front half (positive) of the audio signal and cancel some frequencies while boosting others by up to 3dB! By ensureing a proper seal you will prevent any unwanted phasing and the response of your speakers will be a lot flater, resulting in better efficiency and easier eq-ing.

Hope this helps, check these two things and let us know how you've gone.

P.S. My wife tells me I can be demeining with me tone, forgive me for that , I'm just a smart ass. And even with my background I still make those mistakes listed above from time to time

Oooh, forgot to mention, the 'Punch' Frequency of say a kick drum is around 100 - 200hz (depending on the kick, mic used, type of beater on the kick etc), but the resonance is about 50-80hz. Hope that helps you when you go to tune this sucker for your tastes. a +3-6db spike with a q of about .75 - 1 at 120-150hz should help give you what your after without degrading sub freqencies.

[Checker]

Thanks gents, that's very useful info.

The PDX-5 was rewired in place of the original Macintosh amp (and the sub put in) by a reputable installer - they told me to take my time to listen whether it is the sound I want and are happy to keep tweaking things progressively without getting me to spent a boatload of $$. I was told that the woofer cut off frequency after the install is 100Hz, which sounds too high - hence the installer has since suggested lowering it to 80Hz and dynamatting the front doors.

Your comments confirm that it is the right path to go down (rather than putting in another 8" midbass woofer in the back shelf). I will get the dynamatting, lower the cut off frequencies on the front door woofers, swap out the 13" sub for a 10" and check that the front speakers are wired in the correct phase. It sounds like there should be significant improvement. If its not enough, I will take mihai's suggestion and swap out the front woofers for a better set.

I will post my thoughts in the next week or two after I get the above things done.

PS solongaudi - your tone is not demeaning at all and, given I'm no expert, your comments were not obvious to me. Cheers for that.

[jp928]

Its a Mcintosh! what do you expect?

I replaced mine with a JVC DV6105, std speakers , and I dont even run Loudness, just play a bit with fixed type equalization.......And the SQ is MUCH better, fuller, richer, everything the Mc wasnt.

Obvioulsy YMMV, as all our ears vary, but thats my experience.
jp 08 gtb 6mt wagon.

[solongaudi]

Its a Mcintosh! what do you expect?

LOL!

[Checker]

Done. Dynamatted front doors, front door woofers go down to 80Hz, swapped the 13" Focal for a 10" Hertz - the kick is there now. It sounds fantastic (well, good enough for me).